Technopedia Center
PMB University Brochure
Faculty of Engineering and Computer Science
S1 Informatics S1 Information Systems S1 Information Technology S1 Computer Engineering S1 Electrical Engineering S1 Civil Engineering

faculty of Economics and Business
S1 Management S1 Accountancy

Faculty of Letters and Educational Sciences
S1 English literature S1 English language education S1 Mathematics education S1 Sports Education
  • Registerasi
  • Brosur UTI
  • Kip Scholarship Information
  • Performance
  1. Weltenzyklopädie
  2. Formelsammlung Tensoranalysis – Wikipedia
Formelsammlung Tensoranalysis – Wikipedia 👆 Click Here!
aus Wikipedia, der freien Enzyklopädie
x n {\displaystyle {\sqrt[{n}]{x}}} {\displaystyle {\sqrt[{n}]{x}}}
Dieser Artikel ist eine Formelsammlung zum Thema Tensoranalysis. Es werden mathematische Symbole verwendet, die im Artikel Liste mathematischer Symbole erläutert werden.

Diese Formelsammlung fasst Formeln und Definitionen der Analysis mit Vektor- und Tensorfeldern zweiter Stufe in der Kontinuumsmechanik zusammen.

Allgemeines

[Bearbeiten | Quelltext bearbeiten]

Siehe auch

[Bearbeiten | Quelltext bearbeiten]

Formelsammlung Tensoralgebra

Nomenklatur

[Bearbeiten | Quelltext bearbeiten]
  • Operatoren wie „ g r a d {\displaystyle \mathrm {grad} } {\displaystyle \mathrm {grad} }“ werden nicht kursiv geschrieben.
  • Buchstaben in der Mitte des Alphabets werden als Indizes benutzt: i , j , k , l ∈ { 1 , 2 , 3 } {\displaystyle i,j,k,l\in \{1,2,3\}} {\displaystyle i,j,k,l\in \{1,2,3\}}
  • Es gilt die Einsteinsche Summenkonvention ohne Beachtung der Indexstellung.
    • Kommt in einer Formel in einem Produkt ein Index doppelt vor wie in c = a i b i {\displaystyle c=a_{i}b^{i}} {\displaystyle c=a_{i}b^{i}} wird über diesen Index von eins bis drei summiert:
      c = a i b i = ∑ i = 1 3 a i b i {\displaystyle c=a_{i}b^{i}=\sum _{i=1}^{3}a_{i}b^{i}} {\displaystyle c=a_{i}b^{i}=\sum _{i=1}^{3}a_{i}b^{i}}.
    • Kommen mehrere Indizes doppelt vor wie in c = A i j B j i {\displaystyle c=A_{ij}B_{j}^{i}} {\displaystyle c=A_{ij}B_{j}^{i}} wird über diese summiert:
      c = A i j B j i = ∑ i = 1 3 ∑ j = 1 3 A i j B j i {\displaystyle c=A_{ij}B_{j}^{i}=\sum _{i=1}^{3}\sum _{j=1}^{3}A_{ij}B_{j}^{i}} {\displaystyle c=A_{ij}B_{j}^{i}=\sum _{i=1}^{3}\sum _{j=1}^{3}A_{ij}B_{j}^{i}}.
    • Ein Index, der nur einfach vorkommt wie i {\displaystyle i} {\displaystyle i} in v i = A i j b j {\displaystyle v_{i}=A_{ij}b_{j}} {\displaystyle v_{i}=A_{ij}b_{j}}, ist ein freier Index. Die Formel gilt dann für alle Werte der freien Indizes:
      v i = A i j b j ↔ v i = ∑ j = 1 3 A i j b j ∀ i ∈ { 1 , 2 , 3 } {\displaystyle v_{i}=A_{ij}b_{j}\quad \leftrightarrow \quad v_{i}=\sum _{j=1}^{3}A_{ij}b_{j}\quad \forall \;i\in \{1,2,3\}} {\displaystyle v_{i}=A_{ij}b_{j}\quad \leftrightarrow \quad v_{i}=\sum _{j=1}^{3}A_{ij}b_{j}\quad \forall \;i\in \{1,2,3\}}.
  • Vektoren:
    • Alle hier verwendeten Vektoren sind geometrische Vektoren im dreidimensionalen euklidischen Vektorraum 𝕍={ℝ3,+,·}.
    • Vektoren werden mit Kleinbuchstaben bezeichnet.
    • Einheitsvektoren mit Länge eins werden wie in ê mit einem Hut versehen.
    • Vektoren mit unbestimmter Länge werden wie in a → {\displaystyle {\vec {a}}} {\displaystyle {\vec {a}}} mit einem Pfeil versehen.
    • Standardbasis e ^ 1 , e ^ 2 , e ^ 3 {\displaystyle {\hat {e}}_{1},{\hat {e}}_{2},{\hat {e}}_{3}} {\displaystyle {\hat {e}}_{1},{\hat {e}}_{2},{\hat {e}}_{3}}
    • Beliebige Basis b → 1 , b → 2 , b → 3 {\displaystyle {\vec {b}}_{1},{\vec {b}}_{2},{\vec {b}}_{3}} {\displaystyle {\vec {b}}_{1},{\vec {b}}_{2},{\vec {b}}_{3}} mit dualer Basis b → 1 , b → 2 , b → 3 {\displaystyle {\vec {b}}^{1},{\vec {b}}^{2},{\vec {b}}^{3}} {\displaystyle {\vec {b}}^{1},{\vec {b}}^{2},{\vec {b}}^{3}}
    • Der Vektor x → = x i e ^ i {\displaystyle {\vec {x}}=x_{i}{\hat {e}}_{i}} {\displaystyle {\vec {x}}=x_{i}{\hat {e}}_{i}} wird durchgängig Ortsvektor genannt.
  • Tensoren zweiter Stufe werden wie in T mit fetten Großbuchstaben notiert. Insbesondere Einheitstensor 1.
  • Koordinaten:
    • #Kartesische Koordinaten x 1 , x 2 , x 3 ∈ R {\displaystyle x_{1},x_{2},x_{3}\in \mathbb {R} } {\displaystyle x_{1},x_{2},x_{3}\in \mathbb {R} }
    • #Zylinderkoordinaten: ρ , φ , z {\displaystyle \rho ,\varphi ,z} {\displaystyle \rho ,\varphi ,z}
    • #Kugelkoordinaten: r , ϑ , φ {\displaystyle r,\vartheta ,\varphi } {\displaystyle r,\vartheta ,\varphi }
    • Krummlinige Koordinaten y 1 , y 2 , y 3 ∈ R {\displaystyle y_{1},y_{2},y_{3}\in \mathbb {R} } {\displaystyle y_{1},y_{2},y_{3}\in \mathbb {R} }
  • Konstanten: c , c → , C {\displaystyle c,{\vec {c}},\mathbf {C} } {\displaystyle c,{\vec {c}},\mathbf {C} }
  • Zeit t ∈ ℝ
  • Variablen: skalar r,s ∈ ℝ oder vektorwertig r → , s → ∈ V 3 {\displaystyle {\vec {r}},{\vec {s}}\in \mathbb {V} ^{3}} {\displaystyle {\vec {r}},{\vec {s}}\in \mathbb {V} ^{3}}
  • Feldfunktionen abhängig von x → , t {\displaystyle {\vec {x}},t} {\displaystyle {\vec {x}},t} oder y → , t {\displaystyle {\vec {y}},t} {\displaystyle {\vec {y}},t}:
    • Skalar f , g ∈ R {\displaystyle f,g\in \mathbb {R} } {\displaystyle f,g\in \mathbb {R} } oder vektorwertig f → , g → ∈ V 3 {\displaystyle {\vec {f}},{\vec {g}}\in \mathbb {V} ^{3}} {\displaystyle {\vec {f}},{\vec {g}}\in \mathbb {V} ^{3}}
    • Tensorwertig: S, T
  • Operatoren:
    • Formelsammlung Tensoralgebra#Spur: Sp
    • Formelsammlung Tensoralgebra#Transposition: T⊤
    • Formelsammlung Tensoralgebra#Inverse: T -1
    • Transponierte Inverse: T ⊤-1
    • Formelsammlung Tensoralgebra#Skalarprodukt von Tensoren :, von Vektoren ·
    • Formelsammlung Tensoralgebra#Kreuzprodukt eines Vektors mit einem Tensor × oder von Vektoren untereinander
    • Formelsammlung Tensoralgebra#Dyadisches Produkt ⊗
    • Äußeres Tensorprodukt ( a → ⊗ g → ) # ( b → ⊗ h → ) := ( a → × b → ) ⊗ ( g → × h → ) {\displaystyle ({\vec {a}}\otimes {\vec {g}})\#({\vec {b}}\otimes {\vec {h}}):=({\vec {a}}\times {\vec {b}})\otimes ({\vec {g}}\times {\vec {h}})} {\displaystyle ({\vec {a}}\otimes {\vec {g}})\#({\vec {b}}\otimes {\vec {h}}):=({\vec {a}}\times {\vec {b}})\otimes ({\vec {g}}\times {\vec {h}})}
    • Vektorinvariante i → ( a → ⊗ b → ) = a → × b → {\displaystyle {\vec {\mathrm {i} }}({\vec {a}}\otimes {\vec {b}})={\vec {a}}\times {\vec {b}}} {\displaystyle {\vec {\mathrm {i} }}({\vec {a}}\otimes {\vec {b}})={\vec {a}}\times {\vec {b}}}
  • Differentialoperatoren:
    • #Nabla-Operator: 𝜵
    • #Gradient: grad
    • #Divergenz: div
    • #Rotation: rot
    • #Laplace-Operator: Δ
    • Ein Index hinter einem Komma bezeichnet die Ableitung nach einer Koordinate:
      f , i := ∂ f ∂ x i , f i , j k = ∂ 2 f i ∂ x j ∂ x k , f r , ϑ = ∂ f r ∂ ϑ {\displaystyle f_{,i}:={\frac {\partial f}{\partial x_{i}}}\,,\quad f_{i,jk}={\frac {\partial ^{2}f_{i}}{\partial x_{j}\partial x_{k}}}\,,\quad f_{r,\vartheta }={\frac {\partial f_{r}}{\partial \vartheta }}} {\displaystyle f_{,i}:={\frac {\partial f}{\partial x_{i}}}\,,\quad f_{i,jk}={\frac {\partial ^{2}f_{i}}{\partial x_{j}\partial x_{k}}}\,,\quad f_{r,\vartheta }={\frac {\partial f_{r}}{\partial \vartheta }}}
    • Zeitableitung mit Überpunkt: f ˙ = d f d t , f → ˙ = d f → d t , T ˙ = d d t T {\displaystyle {\dot {f}}={\frac {\mathrm {d} f}{\mathrm {d} t}},{\dot {\vec {f}}}={\frac {\mathrm {d} {\vec {f}}}{\mathrm {d} t}},{\dot {\mathbf {T} }}={\frac {\mathrm {d} }{\mathrm {d} t}}\mathbf {T} } {\displaystyle {\dot {f}}={\frac {\mathrm {d} f}{\mathrm {d} t}},{\dot {\vec {f}}}={\frac {\mathrm {d} {\vec {f}}}{\mathrm {d} t}},{\dot {\mathbf {T} }}={\frac {\mathrm {d} }{\mathrm {d} t}}\mathbf {T} }
  • Landau-Symbole: f = 𝓞(x): f wächst langsamer als x.
  • Kontinuumsmechanik:
    • Verschiebung u → = u i e ^ i {\displaystyle {\vec {u}}=u_{i}{\hat {e}}_{i}} {\displaystyle {\vec {u}}=u_{i}{\hat {e}}_{i}}
    • Geschwindigkeit v → = v i e ^ i {\displaystyle {\vec {v}}=v_{i}{\hat {e}}_{i}} {\displaystyle {\vec {v}}=v_{i}{\hat {e}}_{i}}
    • Deformationsgradient F {\displaystyle \mathbf {F} } {\displaystyle \mathbf {F} }
    • Räumlicher Geschwindigkeitsgradient l {\displaystyle \mathbf {l} } {\displaystyle \mathbf {l} }
    • der Differentialoperator D/Dt und der Überpunkt steht für die substantielle Zeitableitung

Kronecker-Delta

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Kronecker-Delta
δ i j = δ i j = δ i j = δ j i = { 1 falls   i = j 0 sonst {\displaystyle \delta _{ij}=\delta ^{ij}=\delta _{i}^{j}=\delta _{j}^{i}=\left\{{\begin{array}{ll}1&{\text{falls}}\ i=j\\0&{\text{sonst}}\end{array}}\right.} {\displaystyle \delta _{ij}=\delta ^{ij}=\delta _{i}^{j}=\delta _{j}^{i}=\left\{{\begin{array}{ll}1&{\text{falls}}\ i=j\\0&{\text{sonst}}\end{array}}\right.}

Permutationssymbol

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Permutationssymbol
ϵ i j k = e ^ i ⋅ ( e ^ j × e ^ k ) = { 1 falls ( i , j , k ) ∈ { ( 1 , 2 , 3 ) , ( 2 , 3 , 1 ) , ( 3 , 1 , 2 ) } − 1 falls ( i , j , k ) ∈ { ( 1 , 3 , 2 ) , ( 2 , 1 , 3 ) , ( 3 , 2 , 1 ) } 0 sonst, d. h. bei doppeltem Index {\displaystyle \epsilon _{ijk}={\hat {e}}_{i}\cdot ({\hat {e}}_{j}\times {\hat {e}}_{k})={\begin{cases}1&{\text{falls}}\;(i,j,k)\in \{(1,2,3),(2,3,1),(3,1,2)\}\\-1&{\text{falls}}\;(i,j,k)\in \{(1,3,2),(2,1,3),(3,2,1)\}\\0&{\text{sonst, d. h. bei doppeltem Index}}\end{cases}}} {\displaystyle \epsilon _{ijk}={\hat {e}}_{i}\cdot ({\hat {e}}_{j}\times {\hat {e}}_{k})={\begin{cases}1&{\text{falls}}\;(i,j,k)\in \{(1,2,3),(2,3,1),(3,1,2)\}\\-1&{\text{falls}}\;(i,j,k)\in \{(1,3,2),(2,1,3),(3,2,1)\}\\0&{\text{sonst, d. h. bei doppeltem Index}}\end{cases}}}

Kreuzprodukt:

a i e ^ i × b j e ^ j = ϵ i j k a i b j e ^ k {\displaystyle a_{i}{\hat {e}}_{i}\times b_{j}{\hat {e}}_{j}=\epsilon _{ijk}a_{i}b_{j}{\hat {e}}_{k}} {\displaystyle a_{i}{\hat {e}}_{i}\times b_{j}{\hat {e}}_{j}=\epsilon _{ijk}a_{i}b_{j}{\hat {e}}_{k}}
ϵ i j k e ^ k = e ^ i × e ^ j {\displaystyle \epsilon _{ijk}{\hat {e}}_{k}={\hat {e}}_{i}\times {\hat {e}}_{j}} {\displaystyle \epsilon _{ijk}{\hat {e}}_{k}={\hat {e}}_{i}\times {\hat {e}}_{j}}

Formelsammlung Tensoralgebra#Kreuzprodukt eines Vektors mit einem Tensor:

( a → × A ) ⋅ g → := a → × ( A ⋅ g → ) {\displaystyle ({\vec {a}}\times \mathbf {A} )\cdot {\vec {g}}:={\vec {a}}\times (\mathbf {A} \cdot {\vec {g}})} {\displaystyle ({\vec {a}}\times \mathbf {A} )\cdot {\vec {g}}:={\vec {a}}\times (\mathbf {A} \cdot {\vec {g}})}
b → ⋅ ( a → × A ) = ( b → × a → ) ⋅ A {\displaystyle {\vec {b}}\cdot ({\vec {a}}\times \mathbf {A} )=({\vec {b}}\times {\vec {a}})\cdot \mathbf {A} } {\displaystyle {\vec {b}}\cdot ({\vec {a}}\times \mathbf {A} )=({\vec {b}}\times {\vec {a}})\cdot \mathbf {A} }
g → ⋅ ( A × a → ) := ( g → ⋅ A ) × a → {\displaystyle {\vec {g}}\cdot (\mathbf {A} \times {\vec {a}}):=({\vec {g}}\cdot \mathbf {A} )\times {\vec {a}}} {\displaystyle {\vec {g}}\cdot (\mathbf {A} \times {\vec {a}}):=({\vec {g}}\cdot \mathbf {A} )\times {\vec {a}}}
( A × a → ) ⋅ b → = A ⋅ ( a → × b → ) {\displaystyle (\mathbf {A} \times {\vec {a}})\cdot {\vec {b}}=\mathbf {A} \cdot ({\vec {a}}\times {\vec {b}})} {\displaystyle (\mathbf {A} \times {\vec {a}})\cdot {\vec {b}}=\mathbf {A} \cdot ({\vec {a}}\times {\vec {b}})}

Basisvektoren

[Bearbeiten | Quelltext bearbeiten]

Kartesische Koordinaten

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Kartesische Koordinaten
x 1 , x 2 , x 3 ∈ R {\displaystyle x_{1},x_{2},x_{3}\in \mathbb {R} } {\displaystyle x_{1},x_{2},x_{3}\in \mathbb {R} }

mit Basisvektoren

e ^ 1 = ( 1 0 0 ) , e ^ 2 = ( 0 1 0 ) , e ^ 3 = ( 0 0 1 ) {\displaystyle {\hat {e}}_{1}={\begin{pmatrix}1\\0\\0\end{pmatrix}},\quad {\hat {e}}_{2}={\begin{pmatrix}0\\1\\0\end{pmatrix}},\quad {\hat {e}}_{3}={\begin{pmatrix}0\\0\\1\end{pmatrix}}} {\displaystyle {\hat {e}}_{1}={\begin{pmatrix}1\\0\\0\end{pmatrix}},\quad {\hat {e}}_{2}={\begin{pmatrix}0\\1\\0\end{pmatrix}},\quad {\hat {e}}_{3}={\begin{pmatrix}0\\0\\1\end{pmatrix}}}

die Standardbasis oder allgemeiner eine beliebige Orthonormalbasis ist.

Zylinderkoordinaten

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Zylinderkoordinaten
e ^ ρ = ( cos ⁡ ( φ ) sin ⁡ ( φ ) 0 ) , e ^ φ = ( − sin ⁡ ( φ ) cos ⁡ ( φ ) 0 ) , e ^ z = ( 0 0 1 ) {\displaystyle {\hat {e}}_{\rho }={\begin{pmatrix}\cos(\varphi )\\\sin(\varphi )\\0\end{pmatrix}},\quad {\hat {e}}_{\varphi }={\begin{pmatrix}-\sin(\varphi )\\\cos(\varphi )\\0\end{pmatrix}},\quad {\hat {e}}_{z}={\begin{pmatrix}0\\0\\1\end{pmatrix}}} {\displaystyle {\hat {e}}_{\rho }={\begin{pmatrix}\cos(\varphi )\\\sin(\varphi )\\0\end{pmatrix}},\quad {\hat {e}}_{\varphi }={\begin{pmatrix}-\sin(\varphi )\\\cos(\varphi )\\0\end{pmatrix}},\quad {\hat {e}}_{z}={\begin{pmatrix}0\\0\\1\end{pmatrix}}}
e ^ ρ , φ = e ^ φ , e ^ φ , φ = − e ^ ρ e ^ z , φ = 0 → {\displaystyle {\hat {e}}_{\rho ,\varphi }={\hat {e}}_{\varphi },\quad {\hat {e}}_{\varphi ,\varphi }=-{\hat {e}}_{\rho }\quad {\hat {e}}_{z,\varphi }={\vec {0}}} {\displaystyle {\hat {e}}_{\rho ,\varphi }={\hat {e}}_{\varphi },\quad {\hat {e}}_{\varphi ,\varphi }=-{\hat {e}}_{\rho }\quad {\hat {e}}_{z,\varphi }={\vec {0}}}

Winkelgeschwindigkeit#Zylinderkoordinaten:

ω → = φ ˙ e ^ z → e ^ ˙ ρ / φ / z = ω → × e ^ ρ / φ / z {\displaystyle {\vec {\omega }}={\dot {\varphi }}{\hat {e}}_{z}\;\rightarrow \;{\dot {\hat {e}}}_{\rho /\varphi /z}={\vec {\omega }}\times {\hat {e}}_{\rho /\varphi /z}} {\displaystyle {\vec {\omega }}={\dot {\varphi }}{\hat {e}}_{z}\;\rightarrow \;{\dot {\hat {e}}}_{\rho /\varphi /z}={\vec {\omega }}\times {\hat {e}}_{\rho /\varphi /z}}

Kugelkoordinaten

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Kugelkoordinaten
e ^ r = ( sin ⁡ ( ϑ ) cos ⁡ ( φ ) sin ⁡ ( ϑ ) sin ⁡ ( φ ) cos ⁡ ( ϑ ) ) , e ^ ϑ = ( cos ⁡ ( ϑ ) cos ⁡ ( φ ) cos ⁡ ( ϑ ) sin ⁡ ( φ ) − sin ⁡ ( ϑ ) ) , e ^ φ = ( − sin ⁡ ( φ ) cos ⁡ ( φ ) 0 ) {\displaystyle {\hat {e}}_{r}={\begin{pmatrix}\sin(\vartheta )\cos(\varphi )\\\sin(\vartheta )\sin(\varphi )\\\cos(\vartheta )\end{pmatrix}},\quad {\hat {e}}_{\vartheta }={\begin{pmatrix}\cos(\vartheta )\cos(\varphi )\\\cos(\vartheta )\sin(\varphi )\\-\sin(\vartheta )\end{pmatrix}},\quad {\hat {e}}_{\varphi }={\begin{pmatrix}-\sin(\varphi )\\\cos(\varphi )\\0\end{pmatrix}}} {\displaystyle {\hat {e}}_{r}={\begin{pmatrix}\sin(\vartheta )\cos(\varphi )\\\sin(\vartheta )\sin(\varphi )\\\cos(\vartheta )\end{pmatrix}},\quad {\hat {e}}_{\vartheta }={\begin{pmatrix}\cos(\vartheta )\cos(\varphi )\\\cos(\vartheta )\sin(\varphi )\\-\sin(\vartheta )\end{pmatrix}},\quad {\hat {e}}_{\varphi }={\begin{pmatrix}-\sin(\varphi )\\\cos(\varphi )\\0\end{pmatrix}}}

Winkelgeschwindigkeit#Kugelkoordinaten:

ω → = ( − ϑ ˙ sin ⁡ ( φ ) ϑ ˙ cos ⁡ ( φ ) φ ˙ ) = φ ˙ cos ⁡ ( ϑ ) e ^ r − φ ˙ sin ⁡ ( ϑ ) e ^ ϑ + ϑ ˙ e ^ φ → e ^ ˙ r / ϑ / φ = ω → × e ^ r / ϑ / φ {\displaystyle {\begin{aligned}&{\vec {\omega }}={\begin{pmatrix}-{\dot {\vartheta }}\sin(\varphi )\\{\dot {\vartheta }}\cos(\varphi )\\{\dot {\varphi }}\end{pmatrix}}={\dot {\varphi }}\cos(\vartheta ){\hat {e}}_{r}-{\dot {\varphi }}\sin(\vartheta ){\hat {e}}_{\vartheta }+{\dot {\vartheta }}{\hat {e}}_{\varphi }\\&\rightarrow \;{\dot {\hat {e}}}_{r/\vartheta /\varphi }={\vec {\omega }}\times {\hat {e}}_{r/\vartheta /\varphi }\end{aligned}}} {\displaystyle {\begin{aligned}&{\vec {\omega }}={\begin{pmatrix}-{\dot {\vartheta }}\sin(\varphi )\\{\dot {\vartheta }}\cos(\varphi )\\{\dot {\varphi }}\end{pmatrix}}={\dot {\varphi }}\cos(\vartheta ){\hat {e}}_{r}-{\dot {\varphi }}\sin(\vartheta ){\hat {e}}_{\vartheta }+{\dot {\vartheta }}{\hat {e}}_{\varphi }\\&\rightarrow \;{\dot {\hat {e}}}_{r/\vartheta /\varphi }={\vec {\omega }}\times {\hat {e}}_{r/\vartheta /\varphi }\end{aligned}}}

Krummlinige Koordinaten

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Krummlinige Koordinaten
y 1 , y 2 , y 3 ∈ R {\displaystyle y_{1},y_{2},y_{3}\in \mathbb {R} } {\displaystyle y_{1},y_{2},y_{3}\in \mathbb {R} }
b → i = ∂ x → ∂ y i , b → i = grad ⁡ ( y i ) = ∂ y i ∂ x → → b → i ⋅ b → j = δ i j {\displaystyle {\vec {b}}_{i}={\frac {\partial {\vec {x}}}{\partial y_{i}}},\quad {\vec {b}}^{i}=\operatorname {grad} (y_{i})={\frac {\partial y_{i}}{\partial {\vec {x}}}}\quad \rightarrow \quad {\vec {b}}_{i}\cdot {\vec {b}}^{j}=\delta _{i}^{j}} {\displaystyle {\vec {b}}_{i}={\frac {\partial {\vec {x}}}{\partial y_{i}}},\quad {\vec {b}}^{i}=\operatorname {grad} (y_{i})={\frac {\partial y_{i}}{\partial {\vec {x}}}}\quad \rightarrow \quad {\vec {b}}_{i}\cdot {\vec {b}}^{j}=\delta _{i}^{j}}

Ableitung von Skalar-, Vektor- oder Tensorfunktionen

[Bearbeiten | Quelltext bearbeiten]

Gâteaux-Differential

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Gâteaux-Differential
D f ( x ) [ h ] := d d s f ( x + s h ) | s = 0 = lim s → 0 f ( x + s h ) − f ( x ) s {\displaystyle \,\mathrm {D} f(x)[h]:=\left.{\frac {\mathrm {d} }{\mathrm {d} s}}f(x+sh)\right|_{s=0}=\lim _{s\rightarrow 0}{\frac {f(x+sh)-f(x)}{s}}} {\displaystyle \,\mathrm {D} f(x)[h]:=\left.{\frac {\mathrm {d} }{\mathrm {d} s}}f(x+sh)\right|_{s=0}=\lim _{s\rightarrow 0}{\frac {f(x+sh)-f(x)}{s}}}

mit s ∈ R {\displaystyle s\in \mathbb {R} } {\displaystyle s\in \mathbb {R} }, f , x , h {\displaystyle f,x,h} {\displaystyle f,x,h} skalar-, vektor- oder tensorwertig aber x {\displaystyle x} {\displaystyle x} und h {\displaystyle h} {\displaystyle h} gleichartig.

Produktregel:

D ( f ( x ) ⋅ g ( x ) ) [ h ] = D f ( x ) [ h ] ⋅ g ( x ) + f ( x ) ⋅ D g ( x ) [ h ] {\displaystyle \mathrm {D} (f(x)\cdot g(x))[h]=\mathrm {D} f(x)[h]\cdot g(x)+f(x)\cdot \mathrm {D} g(x)[h]} {\displaystyle \mathrm {D} (f(x)\cdot g(x))[h]=\mathrm {D} f(x)[h]\cdot g(x)+f(x)\cdot \mathrm {D} g(x)[h]}

Kettenregel:

D f ( g ( x ) ) [ h ] = D f ( g ) [ D g ( x ) [ h ] ] {\displaystyle \mathrm {D} f{\big (}g(x){\big )}[h]=\mathrm {D} f(g)[Dg(x)[h]]} {\displaystyle \mathrm {D} f{\big (}g(x){\big )}[h]=\mathrm {D} f(g)[Dg(x)[h]]}

Fréchet-Ableitung

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Fréchet-Ableitung

Existiert ein beschränkter linearer Operator A {\displaystyle {\mathcal {A}}} {\displaystyle {\mathcal {A}}}, sodass

A [ h ] = D f ( x ) [ h ] ∀ h {\displaystyle {\mathcal {A}}[h]={Df}(x)[h]{\quad \forall \;}h} {\displaystyle {\mathcal {A}}[h]={Df}(x)[h]{\quad \forall \;}h}

gilt, so wird A {\displaystyle {\mathcal {A}}} {\displaystyle {\mathcal {A}}} Fréchet-Ableitung von f {\displaystyle f} {\displaystyle f} nach x {\displaystyle x} {\displaystyle x} genannt. Man schreibt dann auch

∂ f ∂ x = A {\displaystyle {\frac {\partial f}{\partial x}}={\mathcal {A}}} {\displaystyle {\frac {\partial f}{\partial x}}={\mathcal {A}}}.

Ableitung von Potenzen eines Tensors

[Bearbeiten | Quelltext bearbeiten]
( T − 1 ) ˙ = − T − 1 ⋅ T ˙ ⋅ T − 1 = − ( T − 1 ⊗ T ⊤ − 1 ) ⊤ 23 : T ˙ d T − 1 d T = − ( T − 1 ⊗ T ⊤ − 1 ) ⊤ 23 ( T ⊤ − 1 ) ˙ = − T ⊤ − 1 ⋅ T ˙ ⊤ ⋅ T ⊤ − 1 = − ( T ⊤ − 1 ⊗ T ⊤ − 1 ) ⊤ 24 : T ˙ d T ⊤ − 1 d T = − ( T ⊤ − 1 ⊗ T ⊤ − 1 ) ⊤ 24 {\displaystyle {\begin{aligned}{\big (}\mathbf {T} ^{-1}{\dot {{\big )}\;}}=&-\mathbf {T} ^{-1}\cdot {\dot {\mathbf {T} }}\cdot {\mathbf {T} }^{-1}=-\left(\mathbf {T} ^{-1}\otimes \mathbf {T} ^{\top -1}\right)^{\stackrel {23}{\top }}:{\dot {\mathbf {T} }}\\{\frac {\mathrm {d} \mathbf {T} ^{-1}}{\mathrm {d} \mathbf {T} }}=&-\left(\mathbf {T} ^{-1}\otimes \mathbf {T} ^{\top -1}\right)^{\stackrel {23}{\top }}\\{\big (}\mathbf {T} ^{\top -1}{\dot {{\big )}\;}}=&-\mathbf {T} ^{\top -1}\cdot {\dot {\mathbf {T} }}^{\top }\cdot {\mathbf {T} }^{\top -1}=-\left(\mathbf {T} ^{\top -1}\otimes \mathbf {T} ^{\top -1}\right)^{\stackrel {24}{\top }}:{\dot {\mathbf {T} }}\\{\frac {\mathrm {d} \mathbf {T} ^{\top -1}}{\mathrm {d} \mathbf {T} }}=&-\left(\mathbf {T} ^{\top -1}\otimes \mathbf {T} ^{\top -1}\right)^{\stackrel {24}{\top }}\end{aligned}}} {\displaystyle {\begin{aligned}{\big (}\mathbf {T} ^{-1}{\dot {{\big )}\;}}=&-\mathbf {T} ^{-1}\cdot {\dot {\mathbf {T} }}\cdot {\mathbf {T} }^{-1}=-\left(\mathbf {T} ^{-1}\otimes \mathbf {T} ^{\top -1}\right)^{\stackrel {23}{\top }}:{\dot {\mathbf {T} }}\\{\frac {\mathrm {d} \mathbf {T} ^{-1}}{\mathrm {d} \mathbf {T} }}=&-\left(\mathbf {T} ^{-1}\otimes \mathbf {T} ^{\top -1}\right)^{\stackrel {23}{\top }}\\{\big (}\mathbf {T} ^{\top -1}{\dot {{\big )}\;}}=&-\mathbf {T} ^{\top -1}\cdot {\dot {\mathbf {T} }}^{\top }\cdot {\mathbf {T} }^{\top -1}=-\left(\mathbf {T} ^{\top -1}\otimes \mathbf {T} ^{\top -1}\right)^{\stackrel {24}{\top }}:{\dot {\mathbf {T} }}\\{\frac {\mathrm {d} \mathbf {T} ^{\top -1}}{\mathrm {d} \mathbf {T} }}=&-\left(\mathbf {T} ^{\top -1}\otimes \mathbf {T} ^{\top -1}\right)^{\stackrel {24}{\top }}\end{aligned}}}

siehe Formelsammlung Tensoralgebra#Tensoren vierter Stufe.

Allgemein mit n ∈ ℕ, >0, T0 := 1:

D T n ( T ) [ H ] = ∑ m = 0 n − 1 T m ⋅ H ⋅ T n − m − 1 d T n d T = ( ∑ m = 0 n − 1 T m ⊗ ( T n − m − 1 ) ⊤ ) ⊤ 23 {\displaystyle {\begin{aligned}\mathrm {D} \mathbf {T} ^{n}(\mathbf {T} )[\mathbf {H} ]=&\sum _{m=0}^{n-1}\mathbf {T} ^{m}\cdot \mathbf {H\cdot T} ^{n-m-1}\\{\frac {\mathrm {d} \mathbf {T} ^{n}}{\mathrm {d} \mathbf {T} }}=&\left(\sum _{m=0}^{n-1}\mathbf {T} ^{m}\otimes \left(\mathbf {T} ^{n-m-1}\right)^{\top }\right)^{\stackrel {23}{\top }}\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {D} \mathbf {T} ^{n}(\mathbf {T} )[\mathbf {H} ]=&\sum _{m=0}^{n-1}\mathbf {T} ^{m}\cdot \mathbf {H\cdot T} ^{n-m-1}\\{\frac {\mathrm {d} \mathbf {T} ^{n}}{\mathrm {d} \mathbf {T} }}=&\left(\sum _{m=0}^{n-1}\mathbf {T} ^{m}\otimes \left(\mathbf {T} ^{n-m-1}\right)^{\top }\right)^{\stackrel {23}{\top }}\end{aligned}}}

#Gâteaux-Differential der Inversen:

T ⋅ T − 1 = 1 → D T ( T ) [ H ] ⏞ H ⋅ T − 1 + T ⋅ D T − 1 ( T ) [ H ] = 0 → D T − 1 ( T ) [ H ] = − T − 1 ⋅ H ⋅ T − 1 = − ( T − 1 ⊗ T ⊤ − 1 ) ⊤ 23 : H D T ⊤ − 1 ( T ) [ H ] = − T ⊤ − 1 ⋅ H ⊤ ⋅ T ⊤ − 1 = − ( T ⊤ − 1 ⊗ T ⊤ − 1 ) ⊤ 24 : H {\displaystyle {\begin{aligned}\mathbf {T\cdot T} ^{-1}=&\mathbf {1} \;\rightarrow \quad \overbrace {\mathrm {D} \mathbf {T} (\mathbf {T} )[\mathbf {H} ]} ^{\mathbf {H} }\cdot \mathbf {T} ^{-1}+\mathbf {T} \cdot \mathrm {D} \mathbf {T} ^{-1}(\mathbf {T} )[\mathbf {H} ]=\mathbf {0} \\\rightarrow \quad \mathrm {D} \mathbf {T} ^{-1}(\mathbf {T} )[\mathbf {H} ]=&-\mathbf {T} ^{-1}\cdot \mathbf {H} \cdot \mathbf {T} ^{-1}=-\left(\mathbf {T} ^{-1}\otimes \mathbf {T} ^{\top -1}\right)^{\stackrel {23}{\top }}:\mathbf {H} \\\mathrm {D} \mathbf {T} ^{\top -1}(\mathbf {T} )[\mathbf {H} ]=&-\mathbf {T} ^{\top -1}\cdot \mathbf {H} ^{\top }\cdot \mathbf {T} ^{\top -1}=-\left(\mathbf {T} ^{\top -1}\otimes \mathbf {T} ^{\top -1}\right)^{\stackrel {24}{\top }}:\mathbf {H} \end{aligned}}} {\displaystyle {\begin{aligned}\mathbf {T\cdot T} ^{-1}=&\mathbf {1} \;\rightarrow \quad \overbrace {\mathrm {D} \mathbf {T} (\mathbf {T} )[\mathbf {H} ]} ^{\mathbf {H} }\cdot \mathbf {T} ^{-1}+\mathbf {T} \cdot \mathrm {D} \mathbf {T} ^{-1}(\mathbf {T} )[\mathbf {H} ]=\mathbf {0} \\\rightarrow \quad \mathrm {D} \mathbf {T} ^{-1}(\mathbf {T} )[\mathbf {H} ]=&-\mathbf {T} ^{-1}\cdot \mathbf {H} \cdot \mathbf {T} ^{-1}=-\left(\mathbf {T} ^{-1}\otimes \mathbf {T} ^{\top -1}\right)^{\stackrel {23}{\top }}:\mathbf {H} \\\mathrm {D} \mathbf {T} ^{\top -1}(\mathbf {T} )[\mathbf {H} ]=&-\mathbf {T} ^{\top -1}\cdot \mathbf {H} ^{\top }\cdot \mathbf {T} ^{\top -1}=-\left(\mathbf {T} ^{\top -1}\otimes \mathbf {T} ^{\top -1}\right)^{\stackrel {24}{\top }}:\mathbf {H} \end{aligned}}}

n ∈ ℕ, >0:

D T − n ( T ) [ H ] = ∑ m = 1 − n 0 T m ⋅ D T − 1 ( T ) [ H ] ⋅ T 1 − n − m = − ∑ m = 1 − n 0 T m − 1 ⋅ H ⋅ T − n − m d T − n d T = − ( ∑ m = 1 − n 0 T m − 1 ⊗ ( T − n − m ) ⊤ ) ⊤ 23 {\displaystyle {\begin{aligned}\mathrm {D} \mathbf {T} ^{-n}(\mathbf {T} )[\mathbf {H} ]=&\sum _{m=1-n}^{0}\mathbf {T} ^{m}\cdot \mathrm {D} \mathbf {T} ^{-1}(\mathbf {T} )[\mathbf {H} ]\cdot \mathbf {T} ^{1-n-m}\\=&-\sum _{m=1-n}^{0}\mathbf {T} ^{m-1}\cdot \mathbf {H\cdot T} ^{-n-m}\\{\frac {\mathrm {d} \mathbf {T} ^{-n}}{\mathrm {d} \mathbf {T} }}=&-\left(\sum _{m=1-n}^{0}\mathbf {T} ^{m-1}\otimes \left(\mathbf {T} ^{-n-m}\right)^{\top }\right)^{\stackrel {23}{\top }}\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {D} \mathbf {T} ^{-n}(\mathbf {T} )[\mathbf {H} ]=&\sum _{m=1-n}^{0}\mathbf {T} ^{m}\cdot \mathrm {D} \mathbf {T} ^{-1}(\mathbf {T} )[\mathbf {H} ]\cdot \mathbf {T} ^{1-n-m}\\=&-\sum _{m=1-n}^{0}\mathbf {T} ^{m-1}\cdot \mathbf {H\cdot T} ^{-n-m}\\{\frac {\mathrm {d} \mathbf {T} ^{-n}}{\mathrm {d} \mathbf {T} }}=&-\left(\sum _{m=1-n}^{0}\mathbf {T} ^{m-1}\otimes \left(\mathbf {T} ^{-n-m}\right)^{\top }\right)^{\stackrel {23}{\top }}\end{aligned}}}
D T ⊤ − n ( T ) [ H ] = − ∑ m = 1 − n 0 ( T m − 1 ) ⊤ ⋅ H ⊤ ⋅ ( T − n − m ) ⊤ d T ⊤ − n d T = − ( ∑ m = 1 − n 0 ( T m − 1 ) ⊤ ⊗ ( T − n − m ) ⊤ ) ⊤ 24 {\displaystyle {\begin{aligned}\mathrm {D} \mathbf {T} ^{\top -n}(\mathbf {T} )[\mathbf {H} ]=&-\sum _{m=1-n}^{0}\left(\mathbf {T} ^{m-1}\right)^{\top }\cdot \mathbf {H^{\top }\cdot {\big (}T} ^{-n-m}{\big )}^{\top }\\{\frac {\mathrm {d} \mathbf {T} ^{\top -n}}{\mathrm {d} \mathbf {T} }}=&-\left(\sum _{m=1-n}^{0}\left(\mathbf {T} ^{m-1}\right)^{\top }\otimes \left(\mathbf {T} ^{-n-m}\right)^{\top }\right)^{\stackrel {24}{\top }}\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {D} \mathbf {T} ^{\top -n}(\mathbf {T} )[\mathbf {H} ]=&-\sum _{m=1-n}^{0}\left(\mathbf {T} ^{m-1}\right)^{\top }\cdot \mathbf {H^{\top }\cdot {\big (}T} ^{-n-m}{\big )}^{\top }\\{\frac {\mathrm {d} \mathbf {T} ^{\top -n}}{\mathrm {d} \mathbf {T} }}=&-\left(\sum _{m=1-n}^{0}\left(\mathbf {T} ^{m-1}\right)^{\top }\otimes \left(\mathbf {T} ^{-n-m}\right)^{\top }\right)^{\stackrel {24}{\top }}\end{aligned}}}

Orthogonaler Tensor (Q·Q⊤=1):

Q ˙ ⊤ = − Q ⊤ ⋅ Q ˙ ⋅ Q ⊤ {\displaystyle {\dot {\mathbf {Q} }}^{\top }=-\mathbf {Q} ^{\top }\cdot {\dot {\mathbf {Q} }}\cdot \mathbf {Q} ^{\top }} {\displaystyle {\dot {\mathbf {Q} }}^{\top }=-\mathbf {Q} ^{\top }\cdot {\dot {\mathbf {Q} }}\cdot \mathbf {Q} ^{\top }}

Ableitungen nach dem Ort

[Bearbeiten | Quelltext bearbeiten]

Nabla-Operator

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Nabla-Operator

#Kartesische Koordinaten x → {\displaystyle {\vec {x}}} {\displaystyle {\vec {x}}} : ∇ = e ^ i ∂ ∂ x i {\displaystyle \nabla ={\hat {e}}_{i}{\frac {\partial }{\partial x_{i}}}} {\displaystyle \nabla ={\hat {e}}_{i}{\frac {\partial }{\partial x_{i}}}}

#Zylinderkoordinaten: ∇ = e → ρ ∂ ∂ ρ + 1 ρ e → φ ∂ ∂ φ + e → z ∂ ∂ z {\displaystyle \nabla ={\vec {e}}_{\rho }{\frac {\partial }{\partial \rho }}+{\frac {1}{\rho }}{\vec {e}}_{\varphi }{\frac {\partial }{\partial \varphi }}+{\vec {e}}_{z}{\frac {\partial }{\partial z}}} {\displaystyle \nabla ={\vec {e}}_{\rho }{\frac {\partial }{\partial \rho }}+{\frac {1}{\rho }}{\vec {e}}_{\varphi }{\frac {\partial }{\partial \varphi }}+{\vec {e}}_{z}{\frac {\partial }{\partial z}}}

#Kugelkoordinaten: ∇ = e → r ∂ ∂ r + 1 r e → ϑ ∂ ∂ ϑ + 1 r sin ⁡ ( ϑ ) e → φ ∂ ∂ φ {\displaystyle \nabla ={\vec {e}}_{r}{\frac {\partial }{\partial r}}+{\frac {1}{r}}{\vec {e}}_{\vartheta }{\frac {\partial }{\partial \vartheta }}+{\frac {1}{r\sin(\vartheta )}}{\vec {e}}_{\varphi }{\frac {\partial }{\partial \varphi }}} {\displaystyle \nabla ={\vec {e}}_{r}{\frac {\partial }{\partial r}}+{\frac {1}{r}}{\vec {e}}_{\vartheta }{\frac {\partial }{\partial \vartheta }}+{\frac {1}{r\sin(\vartheta )}}{\vec {e}}_{\varphi }{\frac {\partial }{\partial \varphi }}}

#Krummlinige Koordinaten y → {\displaystyle {\vec {y}}} {\displaystyle {\vec {y}}} : ∇ = b → j ∂ ∂ y j {\displaystyle \nabla ={\vec {b}}^{j}{\frac {\partial }{\partial y_{j}}}} {\displaystyle \nabla ={\vec {b}}^{j}{\frac {\partial }{\partial y_{j}}}}    mit    b → j = ∂ y j ∂ x i e ^ i {\displaystyle {\vec {b}}^{j}={\frac {\partial y_{j}}{\partial x_{i}}}{\hat {e}}_{i}} {\displaystyle {\vec {b}}^{j}={\frac {\partial y_{j}}{\partial x_{i}}}{\hat {e}}_{i}}.

Gradient

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Gradient (Mathematik)

Definition des Gradienten/Allgemeines

[Bearbeiten | Quelltext bearbeiten]

Definierende Eigenschaft bei skalar- oder vektorwertiger Funktion f:[1]

f ( y → ) − f ( x → ) = grad ⁡ ( f ) ⋅ ( y → − x → ) + O ( | y → − x → | ) {\displaystyle f({\vec {y}})-f({\vec {x}})=\operatorname {grad} (f)\cdot ({\vec {y}}-{\vec {x}})+{\mathcal {O}}(|{\vec {y}}-{\vec {x}}|)} {\displaystyle f({\vec {y}})-f({\vec {x}})=\operatorname {grad} (f)\cdot ({\vec {y}}-{\vec {x}})+{\mathcal {O}}(|{\vec {y}}-{\vec {x}}|)} wenn y → → x → {\displaystyle {\vec {y}}\to {\vec {x}}} {\displaystyle {\vec {y}}\to {\vec {x}}}

Wenn der Gradient existiert, ist er eindeutig. Berechnung bei skalar- oder vektorwertiger Funktion f:

grad ⁡ ( f ) ⋅ h → = d d s f ( x → + s h → ) | s = 0 = lim s → 0 f ( x → + s h → ) − f ( x → ) s ∀ h → ∈ V {\displaystyle \operatorname {grad} (f)\cdot {\vec {h}}=\left.{\frac {\mathrm {d} }{\mathrm {d} s}}f({\vec {x}}+s{\vec {h}})\right|_{s=0}=\lim _{s\to 0}{\frac {f({\vec {x}}+s{\vec {h}})-f({\vec {x}})}{s}}\quad \forall \;{\vec {h}}\in \mathbb {V} } {\displaystyle \operatorname {grad} (f)\cdot {\vec {h}}=\left.{\frac {\mathrm {d} }{\mathrm {d} s}}f({\vec {x}}+s{\vec {h}})\right|_{s=0}=\lim _{s\to 0}{\frac {f({\vec {x}}+s{\vec {h}})-f({\vec {x}})}{s}}\quad \forall \;{\vec {h}}\in \mathbb {V} }

Integrabilitätsbedingung: Jedes rotationsfreie Vektorfeld ist das Gradientenfeld eines Skalarpotentials:

rot ⁡ ( f → ) = 0 → → ∃ g : f → = grad ⁡ ( g ) {\displaystyle \operatorname {rot} ({\vec {f}})={\vec {0}}\quad \rightarrow \quad \exists g\colon {\vec {f}}=\operatorname {grad} (g)} {\displaystyle \operatorname {rot} ({\vec {f}})={\vec {0}}\quad \rightarrow \quad \exists g\colon {\vec {f}}=\operatorname {grad} (g)}.

Koordinatenfreie Darstellung als Volumenableitung:

  • Volumen v {\displaystyle v} {\displaystyle v} mit
  • Oberfläche a {\displaystyle a} {\displaystyle a} mit äußerem vektoriellem Oberflächenelement d a → {\displaystyle \mathrm {d} {\vec {a}}} {\displaystyle \mathrm {d} {\vec {a}}}
grad ⁡ ( f ) = lim v → 0 ( 1 v ∫ a f d a → ) {\displaystyle \operatorname {grad} (f)=\lim _{v\to 0}\left({\frac {1}{v}}\int _{a}f\,\mathrm {d} {\vec {a}}\right)} {\displaystyle \operatorname {grad} (f)=\lim _{v\to 0}\left({\frac {1}{v}}\int _{a}f\,\mathrm {d} {\vec {a}}\right)}

Skalarfeld f:

grad ⁡ ( f ) = ∇ f =: ∂ f ∂ x → {\displaystyle \operatorname {grad} (f)=\nabla f=:{\frac {\partial f}{\partial {\vec {x}}}}} {\displaystyle \operatorname {grad} (f)=\nabla f=:{\frac {\partial f}{\partial {\vec {x}}}}}

Vektorfeld f → = f i e ^ i {\displaystyle {\vec {f}}=f_{i}{\hat {e}}_{i}} {\displaystyle {\vec {f}}=f_{i}{\hat {e}}_{i}}:[2]

g r a d ( f → ) = ( ∇ ⊗ f → ) ⊤ =: ∂ f → ∂ x → {\displaystyle \mathrm {grad} ({\vec {f}})=(\nabla \otimes {\vec {f}})^{\top }=:{\frac {\partial {\vec {f}}}{\partial {\vec {x}}}}} {\displaystyle \mathrm {grad} ({\vec {f}})=(\nabla \otimes {\vec {f}})^{\top }=:{\frac {\partial {\vec {f}}}{\partial {\vec {x}}}}}
g r a d ( x → ) = 1 {\displaystyle \mathrm {grad} ({\vec {x}})=\mathbf {1} } {\displaystyle \mathrm {grad} ({\vec {x}})=\mathbf {1} }

Zusammenhang mit den anderen Differentialoperatoren:

g r a d ( f ) = d i v ( f 1 ) = ∇ ⋅ ( f 1 ) {\displaystyle \mathrm {grad} (f)=\mathrm {div} (f\mathbf {1} )=\nabla \cdot (f\mathbf {1} )} {\displaystyle \mathrm {grad} (f)=\mathrm {div} (f\mathbf {1} )=\nabla \cdot (f\mathbf {1} )}
g r a d ( f ) × c → = r o t ( f c → ) {\displaystyle \mathrm {grad} (f)\times {\vec {c}}=\mathrm {rot} (f{\vec {c}})} {\displaystyle \mathrm {grad} (f)\times {\vec {c}}=\mathrm {rot} (f{\vec {c}})}

Gradient in verschiedenen Koordinatensystemen

[Bearbeiten | Quelltext bearbeiten]

#Kartesische Koordinaten:

g r a d ( f ) = f , i e ^ i {\displaystyle \mathrm {grad} (f)=f_{,i}{\hat {e}}_{i}} {\displaystyle \mathrm {grad} (f)=f_{,i}{\hat {e}}_{i}}
g r a d ( f → ) = f → , i ⊗ e ^ i = e ^ i ⊗ g r a d ( f i ) = f i , j e ^ i ⊗ e ^ j {\displaystyle \mathrm {grad} ({\vec {f}})={\vec {f}}_{,i}\otimes {\hat {e}}_{i}={\hat {e}}_{i}\otimes \mathrm {grad} (f_{i})=f_{i,j}{\hat {e}}_{i}\otimes {\hat {e}}_{j}} {\displaystyle \mathrm {grad} ({\vec {f}})={\vec {f}}_{,i}\otimes {\hat {e}}_{i}={\hat {e}}_{i}\otimes \mathrm {grad} (f_{i})=f_{i,j}{\hat {e}}_{i}\otimes {\hat {e}}_{j}}

#Zylinderkoordinaten:

g r a d ( f ) = f , ρ e ^ ρ + f , φ ρ e ^ φ + f , z e ^ z {\displaystyle \mathrm {grad} (f)=f_{,\rho }{\hat {e}}_{\rho }+{\frac {f_{,\varphi }}{\rho }}{\hat {e}}_{\varphi }+f_{,z}{\hat {e}}_{z}} {\displaystyle \mathrm {grad} (f)=f_{,\rho }{\hat {e}}_{\rho }+{\frac {f_{,\varphi }}{\rho }}{\hat {e}}_{\varphi }+f_{,z}{\hat {e}}_{z}}
g r a d ( f → ) = e ^ ρ ⊗ g r a d ( f ρ ) + e ^ φ ⊗ g r a d ( f φ ) + e ^ z ⊗ g r a d ( f z ) + 1 ρ ( f ρ e ^ φ − f φ e ^ ρ ) ⊗ e ^ φ {\displaystyle {\begin{aligned}\mathrm {grad} ({\vec {f}})=&{\hat {e}}_{\rho }\otimes \mathrm {grad} (f_{\rho })+{\hat {e}}_{\varphi }\otimes \mathrm {grad} (f_{\varphi })+{\hat {e}}_{z}\otimes \mathrm {grad} (f_{z})\\&+{\frac {1}{\rho }}(f_{\rho }{\hat {e}}_{\varphi }-f_{\varphi }{\hat {e}}_{\rho })\otimes {\hat {e}}_{\varphi }\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {grad} ({\vec {f}})=&{\hat {e}}_{\rho }\otimes \mathrm {grad} (f_{\rho })+{\hat {e}}_{\varphi }\otimes \mathrm {grad} (f_{\varphi })+{\hat {e}}_{z}\otimes \mathrm {grad} (f_{z})\\&+{\frac {1}{\rho }}(f_{\rho }{\hat {e}}_{\varphi }-f_{\varphi }{\hat {e}}_{\rho })\otimes {\hat {e}}_{\varphi }\end{aligned}}}

#Kugelkoordinaten:

g r a d ( f ) = f , r e ^ r + f , ϑ r e ^ ϑ + f , φ r sin ⁡ ( ϑ ) e ^ φ {\displaystyle \mathrm {grad} (f)=f_{,r}{\hat {e}}_{r}+{\frac {f_{,\vartheta }}{r}}{\hat {e}}_{\vartheta }+{\frac {f_{,\varphi }}{r\sin(\vartheta )}}{\hat {e}}_{\varphi }} {\displaystyle \mathrm {grad} (f)=f_{,r}{\hat {e}}_{r}+{\frac {f_{,\vartheta }}{r}}{\hat {e}}_{\vartheta }+{\frac {f_{,\varphi }}{r\sin(\vartheta )}}{\hat {e}}_{\varphi }}
g r a d ( f → ) = e ^ r ⊗ g r a d ( f r ) + e ^ ϑ ⊗ g r a d ( f ϑ ) + e ^ φ ⊗ g r a d ( f φ ) + f r r ( 1 − e ^ r ⊗ e ^ r ) − e ^ r ⊗ f ϑ e ^ ϑ + f φ e ^ φ r + f ϑ e ^ φ − f φ e ^ ϑ r tan ⁡ ( ϑ ) ⊗ e ^ φ {\displaystyle {\begin{aligned}\mathrm {grad} ({\vec {f}})=&{\hat {e}}_{r}\otimes \mathrm {grad} (f_{r})+{\hat {e}}_{\vartheta }\otimes \mathrm {grad} (f_{\vartheta })+{\hat {e}}_{\varphi }\otimes \mathrm {grad} (f_{\varphi })\\&+{\frac {f_{r}}{r}}(\mathbf {1} -{\hat {e}}_{r}\otimes {\hat {e}}_{r})-{\hat {e}}_{r}\otimes {\frac {f_{\vartheta }{\hat {e}}_{\vartheta }+f_{\varphi }{\hat {e}}_{\varphi }}{r}}+{\frac {f_{\vartheta }{\hat {e}}_{\varphi }-f_{\varphi }{\hat {e}}_{\vartheta }}{r\tan(\vartheta )}}\otimes {\hat {e}}_{\varphi }\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {grad} ({\vec {f}})=&{\hat {e}}_{r}\otimes \mathrm {grad} (f_{r})+{\hat {e}}_{\vartheta }\otimes \mathrm {grad} (f_{\vartheta })+{\hat {e}}_{\varphi }\otimes \mathrm {grad} (f_{\varphi })\\&+{\frac {f_{r}}{r}}(\mathbf {1} -{\hat {e}}_{r}\otimes {\hat {e}}_{r})-{\hat {e}}_{r}\otimes {\frac {f_{\vartheta }{\hat {e}}_{\vartheta }+f_{\varphi }{\hat {e}}_{\varphi }}{r}}+{\frac {f_{\vartheta }{\hat {e}}_{\varphi }-f_{\varphi }{\hat {e}}_{\vartheta }}{r\tan(\vartheta )}}\otimes {\hat {e}}_{\varphi }\end{aligned}}}

#Krummlinige Koordinaten:

Siehe auch: Gradient eines Vektorfeldes

Christoffelsymbole: Γ i j k = g → i , j ⋅ g → k {\displaystyle \Gamma _{ij}^{k}={\vec {g}}_{i,j}\cdot {\vec {g}}^{k}} {\displaystyle \Gamma _{ij}^{k}={\vec {g}}_{i,j}\cdot {\vec {g}}^{k}}

Vektorfelder:

g r a d ( g → i ) = Γ i j k g → k ⊗ g → j {\displaystyle \mathrm {grad} ({\vec {g}}_{i})=\Gamma _{ij}^{k}{\vec {g}}_{k}\otimes {\vec {g}}^{j}} {\displaystyle \mathrm {grad} ({\vec {g}}_{i})=\Gamma _{ij}^{k}{\vec {g}}_{k}\otimes {\vec {g}}^{j}}
g r a d ( g → k ) = − Γ i j k g → i ⊗ g → j {\displaystyle \mathrm {grad} ({\vec {g}}^{k})=-\Gamma _{ij}^{k}{\vec {g}}^{i}\otimes {\vec {g}}^{j}} {\displaystyle \mathrm {grad} ({\vec {g}}^{k})=-\Gamma _{ij}^{k}{\vec {g}}^{i}\otimes {\vec {g}}^{j}}
g r a d ( f i g → i ) = f i | j g → i ⊗ g → j {\displaystyle \mathrm {grad} (f^{i}{\vec {g}}_{i})=\left.f^{i}\right|_{j}{\vec {g}}_{i}\otimes {\vec {g}}^{j}} {\displaystyle \mathrm {grad} (f^{i}{\vec {g}}_{i})=\left.f^{i}\right|_{j}{\vec {g}}_{i}\otimes {\vec {g}}^{j}}
g r a d ( f i g → i ) = f i | j g → i ⊗ g → j {\displaystyle \mathrm {grad} (f_{i}{\vec {g}}^{i})=\left.f_{i}\right|_{j}{\vec {g}}^{i}\otimes {\vec {g}}^{j}} {\displaystyle \mathrm {grad} (f_{i}{\vec {g}}^{i})=\left.f_{i}\right|_{j}{\vec {g}}^{i}\otimes {\vec {g}}^{j}}

Mit den kovarianten Ableitungen

f i | j = f , j i + Γ k j i f k {\displaystyle \left.f^{i}\right|_{j}=f_{,j}^{i}+\Gamma _{kj}^{i}f^{k}} {\displaystyle \left.f^{i}\right|_{j}=f_{,j}^{i}+\Gamma _{kj}^{i}f^{k}}
f i | j = f i , j − Γ i j k f k {\displaystyle \left.f_{i}\right|_{j}=f_{i,j}-\Gamma _{ij}^{k}f_{k}} {\displaystyle \left.f_{i}\right|_{j}=f_{i,j}-\Gamma _{ij}^{k}f_{k}}

Tensorfelder:

g r a d ( T ) [ h → ] = ( h → ⋅ g → k ) T , k = h → ⋅ ( g → k ⊗ T , k ) = ( T , k ⊗ g → k ) ⋅ h → {\displaystyle \mathrm {grad} (\mathbf {T} )[{\vec {h}}]=({\vec {h}}\cdot {\vec {g}}^{k})\mathbf {T} _{,k}={\vec {h}}\cdot ({\vec {g}}^{k}\otimes \mathbf {T} _{,k})=(\mathbf {T} _{,k}\otimes {\vec {g}}^{k})\cdot {\vec {h}}} {\displaystyle \mathrm {grad} (\mathbf {T} )[{\vec {h}}]=({\vec {h}}\cdot {\vec {g}}^{k})\mathbf {T} _{,k}={\vec {h}}\cdot ({\vec {g}}^{k}\otimes \mathbf {T} _{,k})=(\mathbf {T} _{,k}\otimes {\vec {g}}^{k})\cdot {\vec {h}}}

Soll das Argument wie beim Vektorgradient rechts vom Operator stehen, dann lautet der Tensorgradient

g r a d ( T ) = T , k ⊗ g → k {\displaystyle \mathrm {grad} (\mathbf {T} )=\mathbf {T} _{,k}\otimes {\vec {g}}^{k}} {\displaystyle \mathrm {grad} (\mathbf {T} )=\mathbf {T} _{,k}\otimes {\vec {g}}^{k}}

Für ein Tensorfeld zweiter Stufe:

g r a d ( T i j g → i ⊗ g → j ) = T i j | k g → i ⊗ g → j ⊗ g → k , T i j | k = T i j , k − Γ i k l T l j − Γ j k l T i l g r a d ( T i j g → i ⊗ g → j ) = T i j | k g → i ⊗ g → j ⊗ g → k , T i j | k = T , k i j + Γ l k i T l j + Γ l k j T i l g r a d ( T i . j g → i ⊗ g → j ) = T i . j | k g → i ⊗ g → j ⊗ g → k , T i . j | k = T i , k . j − Γ i k l T l . j + Γ l k j T i . l g r a d ( T . j i ) g → i ⊗ g → j = T . j i | k g → i ⊗ g → j ⊗ g → k , T . j i | k = T . j , k i + Γ l k i T . j l − Γ j k l T . l i {\displaystyle {\begin{aligned}\mathrm {grad} (T^{ij}{\vec {g}}_{i}\otimes {\vec {g}}_{j})=&\left.T_{ij}\right|_{k}{\vec {g}}^{i}\otimes {\vec {g}}^{j}\otimes {\vec {g}}^{k},\quad \left.T_{ij}\right|_{k}\!\!\!\!\!\!\!\!\!\!\!\!&=T_{ij,k}-\Gamma _{ik}^{l}T_{lj}-\Gamma _{jk}^{l}T_{il}\\\mathrm {grad} (T^{ij}{\vec {g}}_{i}\otimes {\vec {g}}_{j})=&\left.T^{ij}\right|_{k}{\vec {g}}_{i}\otimes {\vec {g}}_{j}\otimes {\vec {g}}^{k},\quad \left.T^{ij}\right|_{k}\!\!\!\!\!\!\!\!\!\!\!\!&=T_{,k}^{ij}+\Gamma _{lk}^{i}T^{lj}+\Gamma _{lk}^{j}T^{il}\\\mathrm {grad} (T_{i}^{.j}{\vec {g}}^{i}\otimes {\vec {g}}_{j})=&\left.T_{i}^{.j}\right|_{k}{\vec {g}}^{i}\otimes {\vec {g}}_{j}\otimes {\vec {g}}^{k},\quad \left.T_{i}^{.j}\right|_{k}\!\!\!\!\!\!\!\!\!\!\!\!&=T_{i,k}^{.j}-\Gamma _{ik}^{l}T_{l}^{.j}+\Gamma _{lk}^{j}T_{i}^{.l}\\\mathrm {grad} (T_{.j}^{i}){\vec {g}}_{i}\otimes {\vec {g}}^{j}=&\left.T_{.j}^{i}\right|_{k}{\vec {g}}_{i}\otimes {\vec {g}}^{j}\otimes {\vec {g}}^{k},\quad \left.T_{.j}^{i}\right|_{k}\!\!\!\!\!\!\!\!\!\!\!\!&=T_{.j,k}^{i}+\Gamma _{lk}^{i}T_{.j}^{l}-\Gamma _{jk}^{l}T_{.l}^{i}\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {grad} (T^{ij}{\vec {g}}_{i}\otimes {\vec {g}}_{j})=&\left.T_{ij}\right|_{k}{\vec {g}}^{i}\otimes {\vec {g}}^{j}\otimes {\vec {g}}^{k},\quad \left.T_{ij}\right|_{k}\!\!\!\!\!\!\!\!\!\!\!\!&=T_{ij,k}-\Gamma _{ik}^{l}T_{lj}-\Gamma _{jk}^{l}T_{il}\\\mathrm {grad} (T^{ij}{\vec {g}}_{i}\otimes {\vec {g}}_{j})=&\left.T^{ij}\right|_{k}{\vec {g}}_{i}\otimes {\vec {g}}_{j}\otimes {\vec {g}}^{k},\quad \left.T^{ij}\right|_{k}\!\!\!\!\!\!\!\!\!\!\!\!&=T_{,k}^{ij}+\Gamma _{lk}^{i}T^{lj}+\Gamma _{lk}^{j}T^{il}\\\mathrm {grad} (T_{i}^{.j}{\vec {g}}^{i}\otimes {\vec {g}}_{j})=&\left.T_{i}^{.j}\right|_{k}{\vec {g}}^{i}\otimes {\vec {g}}_{j}\otimes {\vec {g}}^{k},\quad \left.T_{i}^{.j}\right|_{k}\!\!\!\!\!\!\!\!\!\!\!\!&=T_{i,k}^{.j}-\Gamma _{ik}^{l}T_{l}^{.j}+\Gamma _{lk}^{j}T_{i}^{.l}\\\mathrm {grad} (T_{.j}^{i}){\vec {g}}_{i}\otimes {\vec {g}}^{j}=&\left.T_{.j}^{i}\right|_{k}{\vec {g}}_{i}\otimes {\vec {g}}^{j}\otimes {\vec {g}}^{k},\quad \left.T_{.j}^{i}\right|_{k}\!\!\!\!\!\!\!\!\!\!\!\!&=T_{.j,k}^{i}+\Gamma _{lk}^{i}T_{.j}^{l}-\Gamma _{jk}^{l}T_{.l}^{i}\end{aligned}}}

Produktregel für Gradienten

[Bearbeiten | Quelltext bearbeiten]
g r a d ( f g ) = ( f , i g + f g , i ) e ^ i = g r a d ( f ) g + f g r a d ( g ) g r a d ( f g → ) = ( f , i g → + f g → , i ) ⊗ e ^ i = g → ⊗ g r a d ( f ) + f g r a d ( g → ) g r a d ( f → ⋅ g → ) = ( f → , i ⋅ g → + f → ⋅ g → , i ) e ^ i = g → ⋅ g r a d ( f → ) + f → ⋅ g r a d ( g → ) g r a d ( f → × g → ) = ( f → , i × g → + f → × g → , i ) ⊗ e ^ i = f → × g r a d ( g → ) − g → × g r a d ( f → ) {\displaystyle {\begin{array}{rclcl}\mathrm {grad} (fg)&=&(f_{,i}g+fg_{,i}){\hat {e}}_{i}&=&\mathrm {grad} (f)g+f\mathrm {grad} (g)\\\mathrm {grad} (f{\vec {g}})&=&(f_{,i}{\vec {g}}+f{\vec {g}}_{,i})\otimes {\hat {e}}_{i}&=&{\vec {g}}\otimes \mathrm {grad} (f)+f\mathrm {grad} ({\vec {g}})\\\mathrm {grad} ({\vec {f}}\cdot {\vec {g}})&=&\left({\vec {f}}_{,i}\cdot {\vec {g}}+{\vec {f}}\cdot {\vec {g}}_{,i}\right){\hat {e}}_{i}&=&{\vec {g}}\cdot \mathrm {grad} ({\vec {f}})+{\vec {f}}\cdot \mathrm {grad} ({\vec {g}})\\\mathrm {grad} ({\vec {f}}\times {\vec {g}})&=&\left({\vec {f}}_{,i}\times {\vec {g}}+{\vec {f}}\times {\vec {g}}_{,i}\right)\otimes {\hat {e}}_{i}&=&{\vec {f}}\times \mathrm {grad} ({\vec {g}})-{\vec {g}}\times \mathrm {grad} ({\vec {f}})\end{array}}} {\displaystyle {\begin{array}{rclcl}\mathrm {grad} (fg)&=&(f_{,i}g+fg_{,i}){\hat {e}}_{i}&=&\mathrm {grad} (f)g+f\mathrm {grad} (g)\\\mathrm {grad} (f{\vec {g}})&=&(f_{,i}{\vec {g}}+f{\vec {g}}_{,i})\otimes {\hat {e}}_{i}&=&{\vec {g}}\otimes \mathrm {grad} (f)+f\mathrm {grad} ({\vec {g}})\\\mathrm {grad} ({\vec {f}}\cdot {\vec {g}})&=&\left({\vec {f}}_{,i}\cdot {\vec {g}}+{\vec {f}}\cdot {\vec {g}}_{,i}\right){\hat {e}}_{i}&=&{\vec {g}}\cdot \mathrm {grad} ({\vec {f}})+{\vec {f}}\cdot \mathrm {grad} ({\vec {g}})\\\mathrm {grad} ({\vec {f}}\times {\vec {g}})&=&\left({\vec {f}}_{,i}\times {\vec {g}}+{\vec {f}}\times {\vec {g}}_{,i}\right)\otimes {\hat {e}}_{i}&=&{\vec {f}}\times \mathrm {grad} ({\vec {g}})-{\vec {g}}\times \mathrm {grad} ({\vec {f}})\end{array}}}

In drei Dimensionen ist speziell[3]

g r a d ( f → ⋅ g → ) = g r a d ( f → ) ⋅ g → + g r a d ( g → ) ⋅ f → + f → × r o t ( g → ) + g → × r o t ( f → ) {\displaystyle \mathrm {grad} ({\vec {f}}\cdot {\vec {g}})=\mathrm {grad} ({\vec {f}})\cdot {\vec {g}}+\mathrm {grad} ({\vec {g}})\cdot {\vec {f}}+{\vec {f}}\times \mathrm {rot} ({\vec {g}})+{\vec {g}}\times \mathrm {rot} ({\vec {f}})} {\displaystyle \mathrm {grad} ({\vec {f}}\cdot {\vec {g}})=\mathrm {grad} ({\vec {f}})\cdot {\vec {g}}+\mathrm {grad} ({\vec {g}})\cdot {\vec {f}}+{\vec {f}}\times \mathrm {rot} ({\vec {g}})+{\vec {g}}\times \mathrm {rot} ({\vec {f}})}

Beliebige Basis:

g r a d ( f i b → i ) = b → i ⊗ g r a d ( f i ) + f i g r a d ( b → i ) {\displaystyle \mathrm {grad} (f_{i}{\vec {b}}_{i})={\vec {b}}_{i}\otimes \mathrm {grad} (f_{i})+f_{i}\,\mathrm {grad} ({\vec {b}}_{i})} {\displaystyle \mathrm {grad} (f_{i}{\vec {b}}_{i})={\vec {b}}_{i}\otimes \mathrm {grad} (f_{i})+f_{i}\,\mathrm {grad} ({\vec {b}}_{i})}

Divergenz

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Divergenz eines Vektorfeldes

Definition der Divergenz/Allgemeines

[Bearbeiten | Quelltext bearbeiten]

Vektorfeld f → {\displaystyle {\vec {f}}} {\displaystyle {\vec {f}}} :

d i v ( f → ) = ∇ ⋅ f → = S p ( g r a d ( f → ) ) {\displaystyle \mathrm {div} ({\vec {f}})=\nabla \cdot {\vec {f}}=\mathrm {Sp} {\big (}\mathrm {grad} ({\vec {f}}){\big )}} {\displaystyle \mathrm {div} ({\vec {f}})=\nabla \cdot {\vec {f}}=\mathrm {Sp} {\big (}\mathrm {grad} ({\vec {f}}){\big )}}
d i v ( x → ) = S p ( g r a d ( x → ) ) = S p ( 1 ) = 3 {\displaystyle \mathrm {div} ({\vec {x}})=\mathrm {Sp} {\big (}\mathrm {grad} ({\vec {x}}){\big )}=\mathrm {Sp} (\mathbf {1} )=3} {\displaystyle \mathrm {div} ({\vec {x}})=\mathrm {Sp} {\big (}\mathrm {grad} ({\vec {x}}){\big )}=\mathrm {Sp} (\mathbf {1} )=3}

Klassische Definition für ein Tensorfeld T:[1]

d i v ( T ) ⋅ c → = d i v ( T ⊤ ⋅ c → ) ∀ c → ∈ V {\displaystyle \mathrm {div} (\mathbf {T} )\cdot {\vec {c}}=\mathrm {div} \left(\mathbf {T} ^{\top }\cdot {\vec {c}}\right)\quad \forall {\vec {c}}\in \mathbb {V} } {\displaystyle \mathrm {div} (\mathbf {T} )\cdot {\vec {c}}=\mathrm {div} \left(\mathbf {T} ^{\top }\cdot {\vec {c}}\right)\quad \forall {\vec {c}}\in \mathbb {V} }
→ d i v ( T ) = ∇ ⋅ ( T ⊤ ) {\displaystyle \mathrm {div} (\mathbf {T} )=\nabla \cdot \left(\mathbf {T} ^{\top }\right)} {\displaystyle \mathrm {div} (\mathbf {T} )=\nabla \cdot \left(\mathbf {T} ^{\top }\right)}

Koordinatenfreie Darstellung:

  • Volumen v {\displaystyle v} {\displaystyle v} mit
  • Oberfläche a {\displaystyle a} {\displaystyle a} mit äußerem vektoriellem Oberflächenelement d a → {\displaystyle \mathrm {d} {\vec {a}}} {\displaystyle \mathrm {d} {\vec {a}}}
d i v ( f → ) = lim v → 0 ( 1 v ∫ a f → ⋅ d a → ) {\displaystyle \mathrm {div} ({\vec {f}})=\lim _{v\to 0}\left({\frac {1}{v}}\int _{a}{\vec {f}}\;\cdot \mathrm {d} {\vec {a}}\right)} {\displaystyle \mathrm {div} ({\vec {f}})=\lim _{v\to 0}\left({\frac {1}{v}}\int _{a}{\vec {f}}\;\cdot \mathrm {d} {\vec {a}}\right)}

Zusammenhang mit den anderen Differentialoperatoren:

d i v ( f → ) = ∇ ⋅ f → = S p ( g r a d ( f → ) ) d i v ( f 1 ) = ∇ ⋅ ( f 1 ) = g r a d ( f ) {\displaystyle {\begin{array}{lcccl}\mathrm {div} ({\vec {f}})&=&\nabla \cdot {\vec {f}}&=&\mathrm {Sp(grad} ({\vec {f}}))\\\mathrm {div} (f\mathbf {1} )&=&\nabla \cdot (f\mathbf {1} )&=&\mathrm {grad} (f)\end{array}}} {\displaystyle {\begin{array}{lcccl}\mathrm {div} ({\vec {f}})&=&\nabla \cdot {\vec {f}}&=&\mathrm {Sp(grad} ({\vec {f}}))\\\mathrm {div} (f\mathbf {1} )&=&\nabla \cdot (f\mathbf {1} )&=&\mathrm {grad} (f)\end{array}}}

Divergenz in verschiedenen Koordinatensystemen

[Bearbeiten | Quelltext bearbeiten]

#Kartesische Koordinaten:

d i v ( f → ) = f → , i ⋅ e ^ i = f i , i {\displaystyle \mathrm {div} ({\vec {f}})={\vec {f}}_{,i}\cdot {\hat {e}}_{i}=f_{i,i}} {\displaystyle \mathrm {div} ({\vec {f}})={\vec {f}}_{,i}\cdot {\hat {e}}_{i}=f_{i,i}}
d i v ( T ) = T , i ⋅ e ^ i = T i j , j e ^ i {\displaystyle \mathrm {div} (\mathbf {T} )=\mathbf {T} _{,i}\cdot {\hat {e}}_{i}=T_{ij,j}{\hat {e}}_{i}} {\displaystyle \mathrm {div} (\mathbf {T} )=\mathbf {T} _{,i}\cdot {\hat {e}}_{i}=T_{ij,j}{\hat {e}}_{i}}
∇ ⋅ T = e ^ i ⋅ T , i = T i j , i e ^ j = T j i , j e ^ i {\displaystyle \nabla \cdot \mathbf {T} ={\hat {e}}_{i}\cdot \mathbf {T} _{,i}=T_{ij,i}{\hat {e}}_{j}=T_{ji,j}{\hat {e}}_{i}} {\displaystyle \nabla \cdot \mathbf {T} ={\hat {e}}_{i}\cdot \mathbf {T} _{,i}=T_{ij,i}{\hat {e}}_{j}=T_{ji,j}{\hat {e}}_{i}}

#Zylinderkoordinaten:

d i v ( f → ) = 1 ρ ∂ ∂ ρ ( ρ f ρ ) + 1 ρ f φ , φ + f z , z {\displaystyle \mathrm {div} ({\vec {f}})={\frac {1}{\rho }}{\frac {\partial }{\partial \rho }}(\rho f_{\rho })+{\frac {1}{\rho }}f_{\varphi ,\varphi }+f_{z,z}} {\displaystyle \mathrm {div} ({\vec {f}})={\frac {1}{\rho }}{\frac {\partial }{\partial \rho }}(\rho f_{\rho })+{\frac {1}{\rho }}f_{\varphi ,\varphi }+f_{z,z}}
d i v ( T ) = ( T ρ ρ , ρ + 1 ρ ( T ρ φ , φ + T ρ ρ − T φ φ ) + T ρ z , z ) e ^ ρ + ( T φ ρ , ρ + 1 ρ ( T φ φ , φ + T ρ φ + T φ ρ ) + T φ z , z ) e ^ φ + ( T z ρ , ρ + 1 ρ ( T z φ , φ + T z ρ ) + T z z , z ) e ^ z {\displaystyle {\begin{aligned}\mathrm {div} (\mathbf {T} )=&\left(T_{\rho \rho ,\rho }+{\frac {1}{\rho }}(T_{\rho \varphi ,\varphi }+T_{\rho \rho }-T_{\varphi \varphi })+T_{\rho z,z}\right){\hat {e}}_{\rho }\\&+\left(T_{\varphi \rho ,\rho }+{\frac {1}{\rho }}(T_{\varphi \varphi ,\varphi }+T_{\rho \varphi }+T_{\varphi \rho })+T_{\varphi z,z}\right){\hat {e}}_{\varphi }\\&+\left(T_{z\rho ,\rho }+{\frac {1}{\rho }}(T_{z\varphi ,\varphi }+T_{z\rho })+T_{zz,z}\right){\hat {e}}_{z}\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {div} (\mathbf {T} )=&\left(T_{\rho \rho ,\rho }+{\frac {1}{\rho }}(T_{\rho \varphi ,\varphi }+T_{\rho \rho }-T_{\varphi \varphi })+T_{\rho z,z}\right){\hat {e}}_{\rho }\\&+\left(T_{\varphi \rho ,\rho }+{\frac {1}{\rho }}(T_{\varphi \varphi ,\varphi }+T_{\rho \varphi }+T_{\varphi \rho })+T_{\varphi z,z}\right){\hat {e}}_{\varphi }\\&+\left(T_{z\rho ,\rho }+{\frac {1}{\rho }}(T_{z\varphi ,\varphi }+T_{z\rho })+T_{zz,z}\right){\hat {e}}_{z}\end{aligned}}}

∇ ⋅ T = d i v ( T ⊤ ) {\displaystyle \nabla \cdot \mathbf {T} =\mathrm {div} \left(\mathbf {T} ^{\top }\right)} {\displaystyle \nabla \cdot \mathbf {T} =\mathrm {div} \left(\mathbf {T} ^{\top }\right)} ergibt sich hieraus durch Vertauschen von Tab durch Tba.

#Kugelkoordinaten:

d i v ( f → ) = f r , r + 2 f r + f ϑ , ϑ r + f ϑ cos ⁡ ( ϑ ) + f φ , φ r sin ⁡ ( ϑ ) d i v ( T ) = ( T r r , r + 2 T r r − T ϑ ϑ − T φ φ + T r ϑ , ϑ r + T r φ , φ + T r ϑ cos ⁡ ( ϑ ) r sin ⁡ ( ϑ ) ) e ^ r ( T ϑ r , r + 2 T ϑ r + T r ϑ + T ϑ ϑ , ϑ r + ( T ϑ ϑ − T φ φ ) cos ⁡ ( ϑ ) + T ϑ φ , φ r sin ⁡ ( ϑ ) ) e ^ ϑ ( T φ r , r + 2 T φ r + T r φ + T φ ϑ , ϑ r + ( T ϑ φ + T φ ϑ ) cos ⁡ ( ϑ ) + T φ φ , φ r sin ⁡ ( ϑ ) ) e ^ φ {\displaystyle {\begin{aligned}\mathrm {div} ({\vec {f}})=&f_{r,r}+{\frac {2f_{r}+f_{\vartheta ,\vartheta }}{r}}+{\frac {f_{\vartheta }\cos(\vartheta )+f_{\varphi ,\varphi }}{r\sin(\vartheta )}}\\\mathrm {div} (\mathbf {T} )=&\left(T_{rr,r}+{\frac {2T_{rr}-T_{\vartheta \vartheta }-T_{\varphi \varphi }+T_{r\vartheta ,\vartheta }}{r}}+{\frac {T_{r\varphi ,\varphi }+T_{r\vartheta }\cos(\vartheta )}{r\sin(\vartheta )}}\right){\hat {e}}_{r}\\&\left(T_{\vartheta r,r}+{\frac {2T_{\vartheta r}+T_{r\vartheta }+T_{\vartheta \vartheta ,\vartheta }}{r}}+{\frac {(T_{\vartheta \vartheta }-T_{\varphi \varphi })\cos(\vartheta )+T_{\vartheta \varphi ,\varphi }}{r\sin(\vartheta )}}\right){\hat {e}}_{\vartheta }\\&\left(T_{\varphi r,r}+{\frac {2T_{\varphi r}+T_{r\varphi }+T_{\varphi \vartheta ,\vartheta }}{r}}+{\frac {(T_{\vartheta \varphi }+T_{\varphi \vartheta })\cos(\vartheta )+T_{\varphi \varphi ,\varphi }}{r\sin(\vartheta )}}\right){\hat {e}}_{\varphi }\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {div} ({\vec {f}})=&f_{r,r}+{\frac {2f_{r}+f_{\vartheta ,\vartheta }}{r}}+{\frac {f_{\vartheta }\cos(\vartheta )+f_{\varphi ,\varphi }}{r\sin(\vartheta )}}\\\mathrm {div} (\mathbf {T} )=&\left(T_{rr,r}+{\frac {2T_{rr}-T_{\vartheta \vartheta }-T_{\varphi \varphi }+T_{r\vartheta ,\vartheta }}{r}}+{\frac {T_{r\varphi ,\varphi }+T_{r\vartheta }\cos(\vartheta )}{r\sin(\vartheta )}}\right){\hat {e}}_{r}\\&\left(T_{\vartheta r,r}+{\frac {2T_{\vartheta r}+T_{r\vartheta }+T_{\vartheta \vartheta ,\vartheta }}{r}}+{\frac {(T_{\vartheta \vartheta }-T_{\varphi \varphi })\cos(\vartheta )+T_{\vartheta \varphi ,\varphi }}{r\sin(\vartheta )}}\right){\hat {e}}_{\vartheta }\\&\left(T_{\varphi r,r}+{\frac {2T_{\varphi r}+T_{r\varphi }+T_{\varphi \vartheta ,\vartheta }}{r}}+{\frac {(T_{\vartheta \varphi }+T_{\varphi \vartheta })\cos(\vartheta )+T_{\varphi \varphi ,\varphi }}{r\sin(\vartheta )}}\right){\hat {e}}_{\varphi }\end{aligned}}}

∇ ⋅ T = d i v ( T ⊤ ) {\displaystyle \nabla \cdot \mathbf {T} =\mathrm {div} \left(\mathbf {T} ^{\top }\right)} {\displaystyle \nabla \cdot \mathbf {T} =\mathrm {div} \left(\mathbf {T} ^{\top }\right)} ergibt sich hieraus durch Vertauschen von Tab durch Tba.

Produktregel für Divergenzen

[Bearbeiten | Quelltext bearbeiten]
d i v ( f g → ) = ∇ ⋅ ( f g → ) = ( f , i g → + f g → , i ) ⋅ e ^ i = g r a d ( f ) ⋅ g → + f d i v ( g → ) {\displaystyle \mathrm {div} (f{\vec {g}})=\nabla \cdot (f{\vec {g}})=\left(f_{,i}{\vec {g}}+f{\vec {g}}_{,i}\right)\cdot {\hat {e}}_{i}=\mathrm {grad} (f)\cdot {\vec {g}}+f\mathrm {div} ({\vec {g}})} {\displaystyle \mathrm {div} (f{\vec {g}})=\nabla \cdot (f{\vec {g}})=\left(f_{,i}{\vec {g}}+f{\vec {g}}_{,i}\right)\cdot {\hat {e}}_{i}=\mathrm {grad} (f)\cdot {\vec {g}}+f\mathrm {div} ({\vec {g}})}
d i v ( f → × g → ) = ∇ ⋅ ( f → × g → ) = ( f → , i × g → + f → × g → , i ) ⋅ e ^ i = g → ⋅ r o t ( f → ) − f → ⋅ r o t ( g → ) {\displaystyle \mathrm {div} ({\vec {f}}\times {\vec {g}})=\nabla \cdot ({\vec {f}}\times {\vec {g}})=\left({\vec {f}}_{,i}\times {\vec {g}}+{\vec {f}}\times {\vec {g}}_{,i}\right)\cdot {\hat {e}}_{i}={\vec {g}}\cdot \mathrm {rot} ({\vec {f}})-{\vec {f}}\cdot \mathrm {rot} ({\vec {g}})} {\displaystyle \mathrm {div} ({\vec {f}}\times {\vec {g}})=\nabla \cdot ({\vec {f}}\times {\vec {g}})=\left({\vec {f}}_{,i}\times {\vec {g}}+{\vec {f}}\times {\vec {g}}_{,i}\right)\cdot {\hat {e}}_{i}={\vec {g}}\cdot \mathrm {rot} ({\vec {f}})-{\vec {f}}\cdot \mathrm {rot} ({\vec {g}})}
d i v ( f → ⊗ g → ) = ( f → , i ⊗ g → + f → ⊗ g → , i ) ⋅ e ^ i = g r a d ( f → ) ⋅ g → + d i v ( g → ) f → d i v ( f T ) = ( f , i T + f T , i ) ⋅ e ^ i = T ⋅ g r a d ( f ) + f d i v ( T ) d i v ( T ⋅ f → ) = ( T , i ⋅ f → + T ⋅ f → , i ) ⋅ e ^ i = d i v ( T ⊤ ) ⋅ f → + T ⊤ : g r a d ( f → ) d i v ( f → × T ) = ( f → , i × T + f → × T , i ) ⋅ e ^ i = i → ( g r a d ( f → ) ⋅ T ⊤ ) + f → × d i v ( T ) {\displaystyle {\begin{aligned}\mathrm {div} ({\vec {f}}\otimes {\vec {g}})=&\left({\vec {f}}_{,i}\otimes {\vec {g}}+{\vec {f}}\otimes {\vec {g}}_{,i}\right)\cdot {\hat {e}}_{i}\!\!\!\!\!\!\!\!\!\!&=&\mathrm {grad} ({\vec {f}})\cdot {\vec {g}}+\mathrm {div} ({\vec {g}}){\vec {f}}\\\mathrm {div} (f\mathbf {T} )=&(f_{,i}\mathbf {T} +f\mathbf {T} _{,i})\cdot {\hat {e}}_{i}\!\!\!\!\!\!\!\!\!\!&=&\mathbf {T} \cdot \mathrm {grad} (f)+f\mathrm {div} (\mathbf {T} )\\\mathrm {div} (\mathbf {T} \cdot {\vec {f}})=&\left(\mathbf {T} _{,i}\cdot {\vec {f}}+\mathbf {T} \cdot {\vec {f}}_{,i}\right)\cdot {\hat {e}}_{i}\!\!\!\!\!\!\!\!\!\!&=&\mathrm {div} (\mathbf {T} ^{\top })\cdot {\vec {f}}+\mathbf {T} ^{\top }:\mathrm {grad} ({\vec {f}})\\\mathrm {div} ({\vec {f}}\times \mathbf {T} )=&({\vec {f}}_{,i}\times \mathbf {T} +{\vec {f}}\times \mathbf {T} _{,i})\cdot {\hat {e}}_{i}\!\!\!\!\!\!\!\!\!\!&=&{\vec {\mathrm {i} }}\left(\mathrm {grad} ({\vec {f}})\cdot \mathbf {T} ^{\top }\right)+{\vec {f}}\times \mathrm {div} (\mathbf {T} )\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {div} ({\vec {f}}\otimes {\vec {g}})=&\left({\vec {f}}_{,i}\otimes {\vec {g}}+{\vec {f}}\otimes {\vec {g}}_{,i}\right)\cdot {\hat {e}}_{i}\!\!\!\!\!\!\!\!\!\!&=&\mathrm {grad} ({\vec {f}})\cdot {\vec {g}}+\mathrm {div} ({\vec {g}}){\vec {f}}\\\mathrm {div} (f\mathbf {T} )=&(f_{,i}\mathbf {T} +f\mathbf {T} _{,i})\cdot {\hat {e}}_{i}\!\!\!\!\!\!\!\!\!\!&=&\mathbf {T} \cdot \mathrm {grad} (f)+f\mathrm {div} (\mathbf {T} )\\\mathrm {div} (\mathbf {T} \cdot {\vec {f}})=&\left(\mathbf {T} _{,i}\cdot {\vec {f}}+\mathbf {T} \cdot {\vec {f}}_{,i}\right)\cdot {\hat {e}}_{i}\!\!\!\!\!\!\!\!\!\!&=&\mathrm {div} (\mathbf {T} ^{\top })\cdot {\vec {f}}+\mathbf {T} ^{\top }:\mathrm {grad} ({\vec {f}})\\\mathrm {div} ({\vec {f}}\times \mathbf {T} )=&({\vec {f}}_{,i}\times \mathbf {T} +{\vec {f}}\times \mathbf {T} _{,i})\cdot {\hat {e}}_{i}\!\!\!\!\!\!\!\!\!\!&=&{\vec {\mathrm {i} }}\left(\mathrm {grad} ({\vec {f}})\cdot \mathbf {T} ^{\top }\right)+{\vec {f}}\times \mathrm {div} (\mathbf {T} )\end{aligned}}}
∇ ⋅ ( f → ⊗ g → ) = e ^ i ⋅ ( f → , i ⊗ g → + f → ⊗ g → , i ) = ( ∇ ⋅ f → ) g → + ( ∇ ⊗ g → ) ⊤ ⋅ f → ∇ ⋅ ( f T ) = e ^ i ⋅ ( f , i T + f T , i ) = ( ∇ f ) ⋅ T + f ∇ ⋅ T ∇ ⋅ ( T ⋅ f → ) = e ^ i ⋅ ( T , i ⋅ f → + T ⋅ f → , i ) = ( ∇ ⋅ T ) ⋅ f → + T : ( ∇ ⊗ f → ) ∇ ⋅ ( T × f → ) = e ^ i ⋅ ( T , i × f → + T × f → , i ) = ( ∇ ⋅ T ) × f → − i → ( ( ∇ ⊗ f → ) ⊤ ⋅ T ) {\displaystyle {\begin{aligned}\nabla \cdot ({\vec {f}}\otimes {\vec {g}})=&{\hat {e}}_{i}\cdot \left({\vec {f}}_{,i}\otimes {\vec {g}}+{\vec {f}}\otimes {\vec {g}}_{,i}\right)\!\!\!\!\!\!\!\!\!\!&=&(\nabla \cdot {\vec {f}}){\vec {g}}+(\nabla \otimes {\vec {g}})^{\top }\cdot {\vec {f}}\\\nabla \cdot (f\mathbf {T} )=&{\hat {e}}_{i}\cdot (f_{,i}\mathbf {T} +f\mathbf {T} _{,i})\!\!\!\!\!\!\!\!\!\!&=&(\nabla f)\cdot \mathbf {T} +f\nabla \cdot \mathbf {T} \\\nabla \cdot (\mathbf {T} \cdot {\vec {f}})=&{\hat {e}}_{i}\cdot \left(\mathbf {T} _{,i}\cdot {\vec {f}}+\mathbf {T} \cdot {\vec {f}}_{,i}\right)\!\!\!\!\!\!\!\!\!\!&=&(\nabla \cdot \mathbf {T} )\cdot {\vec {f}}+\mathbf {T} :(\nabla \otimes {\vec {f}})\\\nabla \cdot (\mathbf {T} \times {\vec {f}})=&{\hat {e}}_{i}\cdot (\mathbf {T} _{,i}\times {\vec {f}}+\mathbf {T} \times {\vec {f}}_{,i})\!\!\!\!\!\!\!\!\!\!&=&(\nabla \cdot \mathbf {T} )\times {\vec {f}}-{\vec {\mathrm {i} }}\left((\nabla \otimes {\vec {f}})^{\top }\cdot \mathbf {T} \right)\end{aligned}}} {\displaystyle {\begin{aligned}\nabla \cdot ({\vec {f}}\otimes {\vec {g}})=&{\hat {e}}_{i}\cdot \left({\vec {f}}_{,i}\otimes {\vec {g}}+{\vec {f}}\otimes {\vec {g}}_{,i}\right)\!\!\!\!\!\!\!\!\!\!&=&(\nabla \cdot {\vec {f}}){\vec {g}}+(\nabla \otimes {\vec {g}})^{\top }\cdot {\vec {f}}\\\nabla \cdot (f\mathbf {T} )=&{\hat {e}}_{i}\cdot (f_{,i}\mathbf {T} +f\mathbf {T} _{,i})\!\!\!\!\!\!\!\!\!\!&=&(\nabla f)\cdot \mathbf {T} +f\nabla \cdot \mathbf {T} \\\nabla \cdot (\mathbf {T} \cdot {\vec {f}})=&{\hat {e}}_{i}\cdot \left(\mathbf {T} _{,i}\cdot {\vec {f}}+\mathbf {T} \cdot {\vec {f}}_{,i}\right)\!\!\!\!\!\!\!\!\!\!&=&(\nabla \cdot \mathbf {T} )\cdot {\vec {f}}+\mathbf {T} :(\nabla \otimes {\vec {f}})\\\nabla \cdot (\mathbf {T} \times {\vec {f}})=&{\hat {e}}_{i}\cdot (\mathbf {T} _{,i}\times {\vec {f}}+\mathbf {T} \times {\vec {f}}_{,i})\!\!\!\!\!\!\!\!\!\!&=&(\nabla \cdot \mathbf {T} )\times {\vec {f}}-{\vec {\mathrm {i} }}\left((\nabla \otimes {\vec {f}})^{\top }\cdot \mathbf {T} \right)\end{aligned}}}

Beliebige Basis:

d i v ( f i b → i ) = ∇ ⋅ ( f i b → i ) = g r a d ( f i ) ⋅ b → i + f i d i v ( b → i ) {\displaystyle \mathrm {div} (f_{i}{\vec {b}}_{i})=\nabla \cdot (f_{i}{\vec {b}}_{i})=\mathrm {grad} (f_{i})\cdot {\vec {b}}_{i}+f_{i}\,\mathrm {div} ({\vec {b}}_{i})} {\displaystyle \mathrm {div} (f_{i}{\vec {b}}_{i})=\nabla \cdot (f_{i}{\vec {b}}_{i})=\mathrm {grad} (f_{i})\cdot {\vec {b}}_{i}+f_{i}\,\mathrm {div} ({\vec {b}}_{i})}
d i v ( T i j b → i ⊗ b → j ) = ( g r a d ( T i j ) ⋅ b → j ) b → i + T i j ( g r a d ( b → i ) ⋅ b → j + d i v ( b → j ) b → i ) {\displaystyle \mathrm {div} (T^{ij}{\vec {b}}_{i}\otimes {\vec {b}}_{j})=(\mathrm {grad} (T^{ij})\cdot {\vec {b}}_{j}){\vec {b}}_{i}+T^{ij}\,{\big (}\mathrm {grad} ({\vec {b}}_{i})\cdot {\vec {b}}_{j}+\mathrm {div} ({\vec {b}}_{j}){\vec {b}}_{i}{\big )}} {\displaystyle \mathrm {div} (T^{ij}{\vec {b}}_{i}\otimes {\vec {b}}_{j})=(\mathrm {grad} (T^{ij})\cdot {\vec {b}}_{j}){\vec {b}}_{i}+T^{ij}\,{\big (}\mathrm {grad} ({\vec {b}}_{i})\cdot {\vec {b}}_{j}+\mathrm {div} ({\vec {b}}_{j}){\vec {b}}_{i}{\big )}}
∇ ⋅ ( T i j b → i ⊗ b → j ) = ( ( ∇ T i j ) ⋅ b → i ) b → j + T i j ( ( ∇ ⋅ b → i ) b → j + ( ∇ b → j ) ⋅ b → i ) {\displaystyle \nabla \cdot (T^{ij}{\vec {b}}_{i}\otimes {\vec {b}}_{j})={\big (}(\nabla T^{ij})\cdot {\vec {b}}_{i}{\big )}{\vec {b}}_{j}+T^{ij}\,{\big (}(\nabla \cdot {\vec {b}}_{i}){\vec {b}}_{j}+(\nabla {\vec {b}}_{j})\cdot {\vec {b}}_{i}{\big )}} {\displaystyle \nabla \cdot (T^{ij}{\vec {b}}_{i}\otimes {\vec {b}}_{j})={\big (}(\nabla T^{ij})\cdot {\vec {b}}_{i}{\big )}{\vec {b}}_{j}+T^{ij}\,{\big (}(\nabla \cdot {\vec {b}}_{i}){\vec {b}}_{j}+(\nabla {\vec {b}}_{j})\cdot {\vec {b}}_{i}{\big )}}

Produkt mit Konstanten:

d i v ( f C ) = C ⋅ g r a d ( f ) → d i v ( f 1 ) = g r a d ( f ) {\displaystyle \mathrm {div} (f\mathbf {C} )=\mathbf {C} \cdot \mathrm {grad} (f)\quad \rightarrow \quad \mathrm {div} (f\mathbf {1} )=\mathrm {grad} (f)} {\displaystyle \mathrm {div} (f\mathbf {C} )=\mathbf {C} \cdot \mathrm {grad} (f)\quad \rightarrow \quad \mathrm {div} (f\mathbf {1} )=\mathrm {grad} (f)}
∇ ⋅ ( f C ) = g r a d ( f ) ⋅ C → ∇ ⋅ ( f 1 ) = ∇ f {\displaystyle \nabla \cdot (f\mathbf {C} )=\mathrm {grad} (f)\cdot \mathbf {C} \quad \rightarrow \quad \nabla \cdot (f\mathbf {1} )=\nabla f} {\displaystyle \nabla \cdot (f\mathbf {C} )=\mathrm {grad} (f)\cdot \mathbf {C} \quad \rightarrow \quad \nabla \cdot (f\mathbf {1} )=\nabla f}
d i v ( C ⋅ f → ) = C ⊤ : g r a d ( f → ) → d i v ( f → ) = d i v ( 1 ⋅ f → ) = 1 : g r a d ( f → ) = S p ( g r a d ( f → ) ) {\displaystyle {\begin{aligned}\mathrm {div} (\mathbf {C} \cdot {\vec {f}})=\mathbf {C} ^{\top }:\mathrm {grad} ({\vec {f}})\quad \rightarrow \quad \mathrm {div} ({\vec {f}})=&\mathrm {div} (\mathbf {1} \cdot {\vec {f}})=\mathbf {1} :\mathrm {grad} ({\vec {f}})\\=&\mathrm {Sp} (\mathrm {grad} ({\vec {f}}))\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {div} (\mathbf {C} \cdot {\vec {f}})=\mathbf {C} ^{\top }:\mathrm {grad} ({\vec {f}})\quad \rightarrow \quad \mathrm {div} ({\vec {f}})=&\mathrm {div} (\mathbf {1} \cdot {\vec {f}})=\mathbf {1} :\mathrm {grad} ({\vec {f}})\\=&\mathrm {Sp} (\mathrm {grad} ({\vec {f}}))\end{aligned}}}

Rotation

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Rotation eines Vektorfeldes

Definition der Rotation/Allgemeines

[Bearbeiten | Quelltext bearbeiten]

Vektorfeld f → {\displaystyle {\vec {f}}} {\displaystyle {\vec {f}}} :

r o t ( f → ) = ∇ × f → {\displaystyle \mathrm {rot} ({\vec {f}})=\nabla \times {\vec {f}}} {\displaystyle \mathrm {rot} ({\vec {f}})=\nabla \times {\vec {f}}}

Klassische Definition für ein Tensorfeld T:[1]

r o t ( T ) ⋅ c → = r o t ( T ⊤ ⋅ c → ) ∀ c → ∈ V {\displaystyle \mathrm {rot} (\mathbf {T} )\cdot {\vec {c}}=\mathrm {rot} \left(\mathbf {T} ^{\top }\cdot {\vec {c}}\right)\quad \forall {\vec {c}}\in \mathbb {V} } {\displaystyle \mathrm {rot} (\mathbf {T} )\cdot {\vec {c}}=\mathrm {rot} \left(\mathbf {T} ^{\top }\cdot {\vec {c}}\right)\quad \forall {\vec {c}}\in \mathbb {V} }
→ r o t ( T ) = ∇ × ( T ⊤ ) {\displaystyle \mathrm {rot} (\mathbf {T} )=\nabla \times \left(\mathbf {T} ^{\top }\right)} {\displaystyle \mathrm {rot} (\mathbf {T} )=\nabla \times \left(\mathbf {T} ^{\top }\right)}

Allgemeine Identitäten:

T = T ⊤ → S p ( r o t ( T ) ) = S p ( ∇ × T ) = 0 {\displaystyle \mathbf {T=T} ^{\top }\quad \rightarrow \quad \mathrm {Sp{\big (}rot} (\mathbf {T} ){\big )}=\mathrm {Sp} (\nabla \times \mathbf {T} )=0} {\displaystyle \mathbf {T=T} ^{\top }\quad \rightarrow \quad \mathrm {Sp{\big (}rot} (\mathbf {T} ){\big )}=\mathrm {Sp} (\nabla \times \mathbf {T} )=0}
r o t ( x → ) = 0 → {\displaystyle \mathrm {rot} ({\vec {x}})={\vec {0}}} {\displaystyle \mathrm {rot} ({\vec {x}})={\vec {0}}}

Integrabilitätsbedingung[4]: Jedes divergenzfreie Vektorfeld ist die Rotation eines Vektorfeldes:

d i v ( f → ) = 0 → ∃ g → : f → = r o t ( g → ) {\displaystyle \mathrm {div} ({\vec {f}})=0\quad \rightarrow \quad \exists {\vec {g}}\colon {\vec {f}}=\mathrm {rot} ({\vec {g}})} {\displaystyle \mathrm {div} ({\vec {f}})=0\quad \rightarrow \quad \exists {\vec {g}}\colon {\vec {f}}=\mathrm {rot} ({\vec {g}})}.

Siehe auch #Satz über rotationsfreie Felder.

Koordinatenfreie Darstellung:

  • Volumen v {\displaystyle v} {\displaystyle v} mit
  • Oberfläche a {\displaystyle a} {\displaystyle a} mit äußerem vektoriellem Oberflächenelement d a → {\displaystyle \mathrm {d} {\vec {a}}} {\displaystyle \mathrm {d} {\vec {a}}}
r o t ( f → ) = − lim v → 0 ( 1 v ∫ a f → × d a → ) {\displaystyle \mathrm {rot} ({\vec {f}})=-\lim _{v\rightarrow 0}\left({\frac {1}{v}}\int _{a}{\vec {f}}\times \mathrm {d} {\vec {a}}\right)} {\displaystyle \mathrm {rot} ({\vec {f}})=-\lim _{v\rightarrow 0}\left({\frac {1}{v}}\int _{a}{\vec {f}}\times \mathrm {d} {\vec {a}}\right)}

Zusammenhang mit den anderen Differentialoperatoren:

r o t ( f c → ) = g r a d ( f ) × c → r o t ( f → ) = − i → ( g r a d ( f → ) ) = i → ( ∇ ⊗ f → ) = ∇ × f → {\displaystyle {\begin{aligned}\mathrm {rot} (f{\vec {c}})=&\mathrm {grad} (f)\times {\vec {c}}\\\mathrm {rot} ({\vec {f}})=&-{\vec {\mathrm {i} }}{\big (}\mathrm {grad} ({\vec {f}}){\big )}={\vec {\mathrm {i} }}(\nabla \otimes {\vec {f}})=\nabla \times {\vec {f}}\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {rot} (f{\vec {c}})=&\mathrm {grad} (f)\times {\vec {c}}\\\mathrm {rot} ({\vec {f}})=&-{\vec {\mathrm {i} }}{\big (}\mathrm {grad} ({\vec {f}}){\big )}={\vec {\mathrm {i} }}(\nabla \otimes {\vec {f}})=\nabla \times {\vec {f}}\end{aligned}}}

Rotation in verschiedenen Koordinatensystemen

[Bearbeiten | Quelltext bearbeiten]

#Kartesische Koordinaten:

r o t ( f → ) = e ^ i × f → , i = f j , i e ^ i × e ^ j = ϵ i j k f j , i e ^ k = ( f 3 , 2 − f 2 , 3 ) e ^ 1 + ( f 1 , 3 − f 3 , 1 ) e ^ 2 + ( f 2 , 1 − f 1 , 2 ) e ^ 3 {\displaystyle {\begin{aligned}\mathrm {rot} ({\vec {f}})=&{\hat {e}}_{i}\times {\vec {f}}_{,i}=f_{j,i}{\hat {e}}_{i}\times {\hat {e}}_{j}=\epsilon _{ijk}f_{j,i}{\hat {e}}_{k}\\=&(f_{3,2}-f_{2,3}){\hat {e}}_{1}+(f_{1,3}-f_{3,1}){\hat {e}}_{2}+(f_{2,1}-f_{1,2}){\hat {e}}_{3}\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {rot} ({\vec {f}})=&{\hat {e}}_{i}\times {\vec {f}}_{,i}=f_{j,i}{\hat {e}}_{i}\times {\hat {e}}_{j}=\epsilon _{ijk}f_{j,i}{\hat {e}}_{k}\\=&(f_{3,2}-f_{2,3}){\hat {e}}_{1}+(f_{1,3}-f_{3,1}){\hat {e}}_{2}+(f_{2,1}-f_{1,2}){\hat {e}}_{3}\end{aligned}}}
r o t ( T ) = e ^ i × T , i ⊤ = e ^ i × T l j , i e ^ j ⊗ e ^ l = ϵ i j k T l j , i e ^ k ⊗ e ^ l {\displaystyle \mathrm {rot} (\mathbf {T} )={\hat {e}}_{i}\times \mathbf {T} _{,i}^{\top }={\hat {e}}_{i}\times T_{lj,i}{\hat {e}}_{j}\otimes {\hat {e}}_{l}=\epsilon _{ijk}T_{lj,i}{\hat {e}}_{k}\otimes {\hat {e}}_{l}} {\displaystyle \mathrm {rot} (\mathbf {T} )={\hat {e}}_{i}\times \mathbf {T} _{,i}^{\top }={\hat {e}}_{i}\times T_{lj,i}{\hat {e}}_{j}\otimes {\hat {e}}_{l}=\epsilon _{ijk}T_{lj,i}{\hat {e}}_{k}\otimes {\hat {e}}_{l}}

#Zylinderkoordinaten:

r o t ( f → ) = f z , φ − ρ f φ , z ρ e ^ ρ + ( f ρ , z − f z , ρ ) e ^ φ + f φ + ρ f φ , ρ − f ρ , φ ρ e ^ z {\displaystyle \mathrm {rot} ({\vec {f}})={\frac {f_{z,\varphi }-\rho f_{\varphi ,z}}{\rho }}{\hat {e}}_{\rho }+(f_{\rho ,z}-f_{z,\rho }){\hat {e}}_{\varphi }+{\frac {f_{\varphi }+\rho f_{\varphi ,\rho }-f_{\rho ,\varphi }}{\rho }}{\hat {e}}_{z}} {\displaystyle \mathrm {rot} ({\vec {f}})={\frac {f_{z,\varphi }-\rho f_{\varphi ,z}}{\rho }}{\hat {e}}_{\rho }+(f_{\rho ,z}-f_{z,\rho }){\hat {e}}_{\varphi }+{\frac {f_{\varphi }+\rho f_{\varphi ,\rho }-f_{\rho ,\varphi }}{\rho }}{\hat {e}}_{z}}
r o t ( T ) = e ^ ρ × ( T , ρ ⊤ ) + 1 ρ e ^ φ × ( T , φ ⊤ ) + e ^ z × ( T , z ⊤ ) {\displaystyle \mathrm {rot} (\mathbf {T} )={\hat {e}}_{\rho }\times (\mathbf {T} _{,\rho }^{\top })+{\frac {1}{\rho }}{\hat {e}}_{\varphi }\times (\mathbf {T} _{,\varphi }^{\top })+{\hat {e}}_{z}\times (\mathbf {T} _{,z}^{\top })} {\displaystyle \mathrm {rot} (\mathbf {T} )={\hat {e}}_{\rho }\times (\mathbf {T} _{,\rho }^{\top })+{\frac {1}{\rho }}{\hat {e}}_{\varphi }\times (\mathbf {T} _{,\varphi }^{\top })+{\hat {e}}_{z}\times (\mathbf {T} _{,z}^{\top })}
∇ × T = e ^ ρ × T , ρ + 1 ρ e ^ φ × T , φ + e ^ z × T , z {\displaystyle \nabla \times \mathbf {T} ={\hat {e}}_{\rho }\times \mathbf {T} _{,\rho }+{\frac {1}{\rho }}{\hat {e}}_{\varphi }\times \mathbf {T} _{,\varphi }+{\hat {e}}_{z}\times \mathbf {T} _{,z}} {\displaystyle \nabla \times \mathbf {T} ={\hat {e}}_{\rho }\times \mathbf {T} _{,\rho }+{\frac {1}{\rho }}{\hat {e}}_{\varphi }\times \mathbf {T} _{,\varphi }+{\hat {e}}_{z}\times \mathbf {T} _{,z}}

#Kugelkoordinaten:

r o t ( f → ) = f φ , ϑ sin ⁡ ( ϑ ) + f φ cos ⁡ ( ϑ ) − f ϑ , φ r sin ⁡ ( ϑ ) e ^ r + ( f r , φ r sin ⁡ ( ϑ ) − f φ + r f φ , r r ) e ^ ϑ + f ϑ + r f ϑ , r − f r , ϑ r e ^ φ {\displaystyle {\begin{aligned}\mathrm {rot} ({\vec {f}})=&{\frac {f_{\varphi ,\vartheta }\sin(\vartheta )+f_{\varphi }\cos(\vartheta )-f_{\vartheta ,\varphi }}{r\sin(\vartheta )}}{\hat {e}}_{r}+\left({\frac {f_{r,\varphi }}{r\sin(\vartheta )}}-{\frac {f_{\varphi }+rf_{\varphi ,r}}{r}}\right){\hat {e}}_{\vartheta }\\&+{\frac {f_{\vartheta }+rf_{\vartheta ,r}-f_{r,\vartheta }}{r}}{\hat {e}}_{\varphi }\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {rot} ({\vec {f}})=&{\frac {f_{\varphi ,\vartheta }\sin(\vartheta )+f_{\varphi }\cos(\vartheta )-f_{\vartheta ,\varphi }}{r\sin(\vartheta )}}{\hat {e}}_{r}+\left({\frac {f_{r,\varphi }}{r\sin(\vartheta )}}-{\frac {f_{\varphi }+rf_{\varphi ,r}}{r}}\right){\hat {e}}_{\vartheta }\\&+{\frac {f_{\vartheta }+rf_{\vartheta ,r}-f_{r,\vartheta }}{r}}{\hat {e}}_{\varphi }\end{aligned}}}
r o t ( T ) = e ^ r × ( T , r ⊤ ) + 1 r e ^ ϑ × ( T , ϑ ⊤ ) + 1 r sin ⁡ ( ϑ ) e ^ φ × ( T , φ ⊤ ) {\displaystyle \mathrm {rot} (\mathbf {T} )={\hat {e}}_{r}\times (\mathbf {T} _{,r}^{\top })+{\frac {1}{r}}{\hat {e}}_{\vartheta }\times (\mathbf {T} _{,\vartheta }^{\top })+{\frac {1}{r\sin(\vartheta )}}{\hat {e}}_{\varphi }\times (\mathbf {T} _{,\varphi }^{\top })} {\displaystyle \mathrm {rot} (\mathbf {T} )={\hat {e}}_{r}\times (\mathbf {T} _{,r}^{\top })+{\frac {1}{r}}{\hat {e}}_{\vartheta }\times (\mathbf {T} _{,\vartheta }^{\top })+{\frac {1}{r\sin(\vartheta )}}{\hat {e}}_{\varphi }\times (\mathbf {T} _{,\varphi }^{\top })}
∇ × T = e ^ r × T , r + 1 r e ^ ϑ × T , ϑ + 1 r sin ⁡ ( ϑ ) e ^ φ × T , φ {\displaystyle \nabla \times \mathbf {T} ={\hat {e}}_{r}\times \mathbf {T} _{,r}+{\frac {1}{r}}{\hat {e}}_{\vartheta }\times \mathbf {T} _{,\vartheta }+{\frac {1}{r\sin(\vartheta )}}{\hat {e}}_{\varphi }\times \mathbf {T} _{,\varphi }} {\displaystyle \nabla \times \mathbf {T} ={\hat {e}}_{r}\times \mathbf {T} _{,r}+{\frac {1}{r}}{\hat {e}}_{\vartheta }\times \mathbf {T} _{,\vartheta }+{\frac {1}{r\sin(\vartheta )}}{\hat {e}}_{\varphi }\times \mathbf {T} _{,\varphi }}

Produktregel für Rotationen

[Bearbeiten | Quelltext bearbeiten]
r o t ( f g → ) = e ^ i × ( f , i g → + f g → , i ) = g r a d ( f ) × g → + f r o t ( g → ) r o t ( f → × g → ) = e ^ i × ( f → , i × g → + f → × g → , i ) = ( e ^ i ⋅ g → ) f → , i − ( e ^ i ⋅ f → , i ) g → + ( e ^ i ⋅ g → , i ) f → − ( e ^ i ⋅ f → ) g → , i = g r a d ( f → ) ⋅ g → − d i v ( f → ) g → + d i v ( g → ) f → − g r a d ( g → ) ⋅ f → = d i v ( f → ⊗ g → ) − d i v ( g → ⊗ f → ) = ∇ ⋅ ( g → ⊗ f → ) − ∇ ⋅ ( f → ⊗ g → ) {\displaystyle {\begin{aligned}\mathrm {rot} (f{\vec {g}})=&{\hat {e}}_{i}\times (f_{,i}{\vec {g}}+f{\vec {g}}_{,i})=\mathrm {grad} (f)\times {\vec {g}}+f\mathrm {rot} ({\vec {g}})\\\mathrm {rot} ({\vec {f}}\times {\vec {g}})=&{\hat {e}}_{i}\times \left({\vec {f}}_{,i}\times {\vec {g}}+{\vec {f}}\times {\vec {g}}_{,i}\right)\\=&({\hat {e}}_{i}\cdot {\vec {g}}){\vec {f}}_{,i}-\left({\hat {e}}_{i}\cdot {\vec {f}}_{,i}\right){\vec {g}}+\left({\hat {e}}_{i}\cdot {\vec {g}}_{,i}\right){\vec {f}}-({\hat {e}}_{i}\cdot {\vec {f}}){\vec {g}}_{,i}\\=&\mathrm {grad} ({\vec {f}})\cdot {\vec {g}}-\mathrm {div} ({\vec {f}}){\vec {g}}+\mathrm {div} ({\vec {g}}){\vec {f}}-\mathrm {grad} ({\vec {g}})\cdot {\vec {f}}\\=&\mathrm {div} ({\vec {f}}\otimes {\vec {g}})-\mathrm {div} ({\vec {g}}\otimes {\vec {f}})=\nabla \cdot ({\vec {g}}\otimes {\vec {f}})-\nabla \cdot ({\vec {f}}\otimes {\vec {g}})\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {rot} (f{\vec {g}})=&{\hat {e}}_{i}\times (f_{,i}{\vec {g}}+f{\vec {g}}_{,i})=\mathrm {grad} (f)\times {\vec {g}}+f\mathrm {rot} ({\vec {g}})\\\mathrm {rot} ({\vec {f}}\times {\vec {g}})=&{\hat {e}}_{i}\times \left({\vec {f}}_{,i}\times {\vec {g}}+{\vec {f}}\times {\vec {g}}_{,i}\right)\\=&({\hat {e}}_{i}\cdot {\vec {g}}){\vec {f}}_{,i}-\left({\hat {e}}_{i}\cdot {\vec {f}}_{,i}\right){\vec {g}}+\left({\hat {e}}_{i}\cdot {\vec {g}}_{,i}\right){\vec {f}}-({\hat {e}}_{i}\cdot {\vec {f}}){\vec {g}}_{,i}\\=&\mathrm {grad} ({\vec {f}})\cdot {\vec {g}}-\mathrm {div} ({\vec {f}}){\vec {g}}+\mathrm {div} ({\vec {g}}){\vec {f}}-\mathrm {grad} ({\vec {g}})\cdot {\vec {f}}\\=&\mathrm {div} ({\vec {f}}\otimes {\vec {g}})-\mathrm {div} ({\vec {g}}\otimes {\vec {f}})=\nabla \cdot ({\vec {g}}\otimes {\vec {f}})-\nabla \cdot ({\vec {f}}\otimes {\vec {g}})\end{aligned}}}
r o t ( f → ⊗ g → ) = e ^ i × ( g → , i ⊗ f → + g → ⊗ f → , i ) = r o t ( g → ) ⊗ f → − g → × g r a d ( f → ) ⊤ r o t ( f T ) = e ^ k × ( f , k T ⊤ + f T , k ⊤ ) = g r a d ( f ) × ( T ⊤ ) + f r o t ( T ) {\displaystyle {\begin{aligned}\mathrm {rot} ({\vec {f}}\otimes {\vec {g}})=&{\hat {e}}_{i}\times \left({\vec {g}}_{,i}\otimes {\vec {f}}+{\vec {g}}\otimes {\vec {f}}_{,i}\right)\!\!\!\!\!\!\!\!\!\!&=&\mathrm {rot} ({\vec {g}})\otimes {\vec {f}}-{\vec {g}}\times \mathrm {grad} ({\vec {f}})^{\top }\\\mathrm {rot} (f\mathbf {T} )=&{\hat {e}}_{k}\times (f_{,k}\mathbf {T} ^{\top }+f\mathbf {T} _{,k}^{\top })\!\!\!\!\!\!\!\!\!\!&=&\mathrm {grad} (f)\times (\mathbf {T} ^{\top })+f\mathrm {rot} (\mathbf {T} )\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {rot} ({\vec {f}}\otimes {\vec {g}})=&{\hat {e}}_{i}\times \left({\vec {g}}_{,i}\otimes {\vec {f}}+{\vec {g}}\otimes {\vec {f}}_{,i}\right)\!\!\!\!\!\!\!\!\!\!&=&\mathrm {rot} ({\vec {g}})\otimes {\vec {f}}-{\vec {g}}\times \mathrm {grad} ({\vec {f}})^{\top }\\\mathrm {rot} (f\mathbf {T} )=&{\hat {e}}_{k}\times (f_{,k}\mathbf {T} ^{\top }+f\mathbf {T} _{,k}^{\top })\!\!\!\!\!\!\!\!\!\!&=&\mathrm {grad} (f)\times (\mathbf {T} ^{\top })+f\mathrm {rot} (\mathbf {T} )\end{aligned}}}

r o t ( T ⋅ f → ) = e ^ k × ( T , k ⋅ f → + T ⋅ f → , k ) = r o t ( T ⊤ ) ⋅ f → + i → ( e ^ k ⊗ T ⋅ f → , k ) = r o t ( T ⊤ ) ⋅ f → − i → ( T ⋅ g r a d ( f → ) ) r o t ( f → × T ) = − r o t ( ( T ⊤ × f → ) ⊤ ) = − ∇ × ( T ⊤ × f → ) = − ( ∇ × T ⊤ ) × f → + T ⊤ # ( ∇ ⊗ f → ) = − r o t ( T ) × f → + ( T # g r a d ( f → ) ) ⊤ {\displaystyle {\begin{aligned}\mathrm {rot} (\mathbf {T} \cdot {\vec {f}})=&{\hat {e}}_{k}\times {\big (}\mathbf {T} _{,k}\cdot {\vec {f}}+\mathbf {T} \cdot {\vec {f}}_{,k}{\big )}\\=&\mathrm {rot} (\mathbf {T} ^{\top })\cdot {\vec {f}}+{\vec {\mathrm {i} }}\left({\hat {e}}_{k}\otimes \mathbf {T} \cdot {\vec {f}}_{,k}\right)\\=&\mathrm {rot} (\mathbf {T} ^{\top })\cdot {\vec {f}}-{\vec {\mathrm {i} }}\left(\mathbf {T} \cdot \mathrm {grad} ({\vec {f}})\right)\\\mathrm {rot} ({\vec {f}}\times \mathbf {T} )=&-\mathrm {rot} \left((\mathbf {T} ^{\top }\times {\vec {f}})^{\top }\right)\\=&-\nabla \times \left(\mathbf {T} ^{\top }\times {\vec {f}}\right)\\=&-(\nabla \times \mathbf {T} ^{\top })\times {\vec {f}}+\mathbf {T} ^{\top }\#(\nabla \otimes {\vec {f}})\\=&-\mathrm {rot} (\mathbf {T} )\times {\vec {f}}+\left(\mathbf {T} \#\mathrm {grad} ({\vec {f}})\right)^{\top }\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {rot} (\mathbf {T} \cdot {\vec {f}})=&{\hat {e}}_{k}\times {\big (}\mathbf {T} _{,k}\cdot {\vec {f}}+\mathbf {T} \cdot {\vec {f}}_{,k}{\big )}\\=&\mathrm {rot} (\mathbf {T} ^{\top })\cdot {\vec {f}}+{\vec {\mathrm {i} }}\left({\hat {e}}_{k}\otimes \mathbf {T} \cdot {\vec {f}}_{,k}\right)\\=&\mathrm {rot} (\mathbf {T} ^{\top })\cdot {\vec {f}}-{\vec {\mathrm {i} }}\left(\mathbf {T} \cdot \mathrm {grad} ({\vec {f}})\right)\\\mathrm {rot} ({\vec {f}}\times \mathbf {T} )=&-\mathrm {rot} \left((\mathbf {T} ^{\top }\times {\vec {f}})^{\top }\right)\\=&-\nabla \times \left(\mathbf {T} ^{\top }\times {\vec {f}}\right)\\=&-(\nabla \times \mathbf {T} ^{\top })\times {\vec {f}}+\mathbf {T} ^{\top }\#(\nabla \otimes {\vec {f}})\\=&-\mathrm {rot} (\mathbf {T} )\times {\vec {f}}+\left(\mathbf {T} \#\mathrm {grad} ({\vec {f}})\right)^{\top }\end{aligned}}}

∇ × ( f → ⊗ g → ) = e ^ i × ( f → , i ⊗ g → + f → ⊗ g → , i ) = ( ∇ × f → ) ⊗ g → − f → × ( ∇ ⊗ ( g → ) ∇ × ( f T ) = e ^ k × ( f , k T + f T , k ) = ( ∇ f ) × T + f ∇ × T {\displaystyle {\begin{aligned}\nabla \times ({\vec {f}}\otimes {\vec {g}})=&{\hat {e}}_{i}\times \left({\vec {f}}_{,i}\otimes {\vec {g}}+{\vec {f}}\otimes {\vec {g}}_{,i}\right)\!\!\!\!\!\!\!\!\!\!&=&(\nabla \times {\vec {f}})\otimes {\vec {g}}-{\vec {f}}\times (\nabla \otimes ({\vec {g}})\\\nabla \times (f\mathbf {T} )=&{\hat {e}}_{k}\times (f_{,k}\mathbf {T} +f\mathbf {T} _{,k})\!\!\!\!\!\!\!\!\!\!&=&(\nabla f)\times \mathbf {T} +f\nabla \times \mathbf {T} \end{aligned}}} {\displaystyle {\begin{aligned}\nabla \times ({\vec {f}}\otimes {\vec {g}})=&{\hat {e}}_{i}\times \left({\vec {f}}_{,i}\otimes {\vec {g}}+{\vec {f}}\otimes {\vec {g}}_{,i}\right)\!\!\!\!\!\!\!\!\!\!&=&(\nabla \times {\vec {f}})\otimes {\vec {g}}-{\vec {f}}\times (\nabla \otimes ({\vec {g}})\\\nabla \times (f\mathbf {T} )=&{\hat {e}}_{k}\times (f_{,k}\mathbf {T} +f\mathbf {T} _{,k})\!\!\!\!\!\!\!\!\!\!&=&(\nabla f)\times \mathbf {T} +f\nabla \times \mathbf {T} \end{aligned}}}

∇ × ( T ⋅ f → ) = e ^ k × ( T , k ⋅ f → + T ⋅ f → , k ) = ( ∇ × T ) ⋅ f → + i → ( e ^ k ⊗ T ⋅ f → , k ) = ( ∇ × T ) ⋅ f → − i → ( T ⋅ ( ∇ ⊗ f → ) ⊤ ) ∇ × ( T × f → ) = e ^ k × ( T , k × f → + ( T ⋅ e ^ i ) ⊗ e ^ i × f → , k ) = ( ∇ × T ) × f → − ( T ⋅ e ^ i ) × e ^ k ⊗ e ^ i × f → , k = ( ∇ × T ) × f → − T # ( ∇ ⊗ f → ) {\displaystyle {\begin{aligned}\nabla \times (\mathbf {T} \cdot {\vec {f}})=&{\hat {e}}_{k}\times (\mathbf {T} _{,k}\cdot {\vec {f}}+\mathbf {T} \cdot {\vec {f}}_{,k})\\=&(\nabla \times \mathbf {T} )\cdot {\vec {f}}+{\vec {\mathrm {i} }}\left({\hat {e}}_{k}\otimes \mathbf {T} \cdot {\vec {f}}_{,k}\right)\\=&(\nabla \times \mathbf {T} )\cdot {\vec {f}}-{\vec {\mathrm {i} }}{\big (}\mathbf {T} \cdot (\nabla \otimes {\vec {f}})^{\top }{\big )}\\\nabla \times (\mathbf {T} \times {\vec {f}})=&{\hat {e}}_{k}\times (\mathbf {T} _{,k}\times {\vec {f}}+(\mathbf {T} \cdot {\hat {e}}_{i})\otimes {\hat {e}}_{i}\times {\vec {f}}_{,k})\\=&(\nabla \times \mathbf {T} )\times {\vec {f}}-(\mathbf {T} \cdot {\hat {e}}_{i})\times {\hat {e}}_{k}\otimes {\hat {e}}_{i}\times {\vec {f}}_{,k}\\=&(\nabla \times \mathbf {T} )\times {\vec {f}}-\mathbf {T} \#(\nabla \otimes {\vec {f}})\end{aligned}}} {\displaystyle {\begin{aligned}\nabla \times (\mathbf {T} \cdot {\vec {f}})=&{\hat {e}}_{k}\times (\mathbf {T} _{,k}\cdot {\vec {f}}+\mathbf {T} \cdot {\vec {f}}_{,k})\\=&(\nabla \times \mathbf {T} )\cdot {\vec {f}}+{\vec {\mathrm {i} }}\left({\hat {e}}_{k}\otimes \mathbf {T} \cdot {\vec {f}}_{,k}\right)\\=&(\nabla \times \mathbf {T} )\cdot {\vec {f}}-{\vec {\mathrm {i} }}{\big (}\mathbf {T} \cdot (\nabla \otimes {\vec {f}})^{\top }{\big )}\\\nabla \times (\mathbf {T} \times {\vec {f}})=&{\hat {e}}_{k}\times (\mathbf {T} _{,k}\times {\vec {f}}+(\mathbf {T} \cdot {\hat {e}}_{i})\otimes {\hat {e}}_{i}\times {\vec {f}}_{,k})\\=&(\nabla \times \mathbf {T} )\times {\vec {f}}-(\mathbf {T} \cdot {\hat {e}}_{i})\times {\hat {e}}_{k}\otimes {\hat {e}}_{i}\times {\vec {f}}_{,k}\\=&(\nabla \times \mathbf {T} )\times {\vec {f}}-\mathbf {T} \#(\nabla \otimes {\vec {f}})\end{aligned}}}

Beliebige Basis:

r o t ( f i b → i ) = g r a d ( f i ) × b → i + f i r o t ( b → i ) {\displaystyle \mathrm {rot} (f^{i}{\vec {b}}_{i})=\mathrm {grad} (f^{i})\times {\vec {b}}_{i}+f^{i}\,\mathrm {rot} ({\vec {b}}_{i})} {\displaystyle \mathrm {rot} (f^{i}{\vec {b}}_{i})=\mathrm {grad} (f^{i})\times {\vec {b}}_{i}+f^{i}\,\mathrm {rot} ({\vec {b}}_{i})}

Produkt mit Konstanten:

r o t ( C ⋅ f → ) = − i → ( C ⋅ g r a d ( f → ) ) → r o t ( f → ) = r o t ( 1 ⋅ f → ) = − i → ( g r a d ( f → ) ) r o t ( f → × 1 ) = 1 # g r a d ( f → ) ⊤ = g r a d ( f → ) − d i v ( f → ) 1 {\displaystyle {\begin{array}{rcl}\mathrm {rot} (\mathbf {C} \cdot {\vec {f}})&=&-{\vec {\mathrm {i} }}\left(\mathbf {C} \cdot \mathrm {grad} ({\vec {f}})\right)\\&&\rightarrow \quad \mathrm {rot} ({\vec {f}})=\mathrm {rot} (\mathbf {1} \cdot {\vec {f}})=-{\vec {\mathrm {i} }}\left(\mathrm {grad} ({\vec {f}})\right)\\\mathrm {rot} ({\vec {f}}\times \mathbf {1} )&=&\mathbf {1} \#\mathrm {grad} ({\vec {f}})^{\top }=\mathrm {grad} ({\vec {f}})-\mathrm {div} ({\vec {f}})\mathbf {1} \end{array}}} {\displaystyle {\begin{array}{rcl}\mathrm {rot} (\mathbf {C} \cdot {\vec {f}})&=&-{\vec {\mathrm {i} }}\left(\mathbf {C} \cdot \mathrm {grad} ({\vec {f}})\right)\\&&\rightarrow \quad \mathrm {rot} ({\vec {f}})=\mathrm {rot} (\mathbf {1} \cdot {\vec {f}})=-{\vec {\mathrm {i} }}\left(\mathrm {grad} ({\vec {f}})\right)\\\mathrm {rot} ({\vec {f}}\times \mathbf {1} )&=&\mathbf {1} \#\mathrm {grad} ({\vec {f}})^{\top }=\mathrm {grad} ({\vec {f}})-\mathrm {div} ({\vec {f}})\mathbf {1} \end{array}}}

In divergenzfreien Feldern ist also: r o t ( f → × 1 ) = g r a d ( f → ) {\displaystyle \mathrm {rot} ({\vec {f}}\times \mathbf {1} )=\mathrm {grad} ({\vec {f}})} {\displaystyle \mathrm {rot} ({\vec {f}}\times \mathbf {1} )=\mathrm {grad} ({\vec {f}})}

Laplace-Operator

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Laplace-Operator

Definition/Allgemeines

[Bearbeiten | Quelltext bearbeiten]
Δ := ∇ ⋅ ∇ = ∇ 2 {\displaystyle \Delta :=\nabla \cdot \nabla =\nabla ^{2}} {\displaystyle \Delta :=\nabla \cdot \nabla =\nabla ^{2}}

Zusammenhang mit anderen Differentialoperatoren:

Δ f = d i v ( g r a d ( f ) ) = ∇ ⋅ ( ∇ f ) Δ f → = d i v ( g r a d ( f → ) ) = ∇ ⋅ ( ∇ ⊗ f → ) {\displaystyle {\begin{array}{rclcl}\Delta f&=&\mathrm {div{\big (}grad} (f){\big )}&=&\nabla \cdot (\nabla f)\\\Delta {\vec {f}}&=&\mathrm {div{\big (}grad} ({\vec {f}}){\big )}&=&\nabla \cdot (\nabla \otimes {\vec {f}})\end{array}}} {\displaystyle {\begin{array}{rclcl}\Delta f&=&\mathrm {div{\big (}grad} (f){\big )}&=&\nabla \cdot (\nabla f)\\\Delta {\vec {f}}&=&\mathrm {div{\big (}grad} ({\vec {f}}){\big )}&=&\nabla \cdot (\nabla \otimes {\vec {f}})\end{array}}}

„Vektorieller Laplace-Operator“:

Δ f → = g r a d ( d i v ( f → ) ) − r o t ( r o t ( f → ) ) {\displaystyle \Delta {\vec {f}}=\mathrm {grad{\big (}div} ({\vec {f}}){\big )}-\mathrm {rot{\big (}rot} ({\vec {f}}){\big )}} {\displaystyle \Delta {\vec {f}}=\mathrm {grad{\big (}div} ({\vec {f}}){\big )}-\mathrm {rot{\big (}rot} ({\vec {f}}){\big )}}

Laplace-Operator in verschiedenen Koordinatensystemen

[Bearbeiten | Quelltext bearbeiten]

#Kartesische Koordinaten:

Δ f = f , k k Δ f → = Δ f i e ^ i = f i , k k e ^ i Δ T = Δ T i j e ^ i ⊗ e ^ j = T i j , k k e ^ i ⊗ e ^ j {\displaystyle {\begin{aligned}\Delta f=&f_{,kk}\\\Delta {\vec {f}}=&\Delta f_{i}{\hat {e}}_{i}=f_{i,kk}{\hat {e}}_{i}\\\Delta \mathbf {T} =&\Delta T_{ij}{\hat {e}}_{i}\otimes {\hat {e}}_{j}=T_{ij,kk}{\hat {e}}_{i}\otimes {\hat {e}}_{j}\end{aligned}}} {\displaystyle {\begin{aligned}\Delta f=&f_{,kk}\\\Delta {\vec {f}}=&\Delta f_{i}{\hat {e}}_{i}=f_{i,kk}{\hat {e}}_{i}\\\Delta \mathbf {T} =&\Delta T_{ij}{\hat {e}}_{i}\otimes {\hat {e}}_{j}=T_{ij,kk}{\hat {e}}_{i}\otimes {\hat {e}}_{j}\end{aligned}}}

#Zylinderkoordinaten:

Δ f = f , ρ ρ + f , ρ ρ + f , φ φ ρ 2 + f , z z Δ f → = ( Δ f ρ − 2 f φ , φ + f ρ ρ 2 ) e ^ ρ + ( Δ f φ + 2 f ρ , φ − f φ ρ 2 ) e ^ φ + Δ f z e ^ z {\displaystyle {\begin{aligned}\Delta f=&{\frac {f_{,\rho }}{\rho }}+f_{,\rho \rho }+{\frac {f_{,\varphi \varphi }}{\rho ^{2}}}+f_{,zz}\\\Delta {\vec {f}}=&\left(\Delta f_{\rho }-{\frac {2f_{\varphi ,\varphi }+f_{\rho }}{\rho ^{2}}}\right){\hat {e}}_{\rho }+\left(\Delta f_{\varphi }+{\frac {2f_{\rho ,\varphi }-f_{\varphi }}{\rho ^{2}}}\right){\hat {e}}_{\varphi }+\Delta f_{z}{\hat {e}}_{z}\end{aligned}}} {\displaystyle {\begin{aligned}\Delta f=&{\frac {f_{,\rho }}{\rho }}+f_{,\rho \rho }+{\frac {f_{,\varphi \varphi }}{\rho ^{2}}}+f_{,zz}\\\Delta {\vec {f}}=&\left(\Delta f_{\rho }-{\frac {2f_{\varphi ,\varphi }+f_{\rho }}{\rho ^{2}}}\right){\hat {e}}_{\rho }+\left(\Delta f_{\varphi }+{\frac {2f_{\rho ,\varphi }-f_{\varphi }}{\rho ^{2}}}\right){\hat {e}}_{\varphi }+\Delta f_{z}{\hat {e}}_{z}\end{aligned}}}

#Kugelkoordinaten:

Δ f = 1 r 2 ∂ ∂ r ( r 2 ∂ f ∂ r ) + 1 r 2 sin ⁡ ( ϑ ) ∂ ∂ ϑ ( sin ⁡ ( ϑ ) ∂ f ∂ ϑ ) + 1 r 2 sin 2 ⁡ ( ϑ ) ∂ 2 f ∂ φ 2 = 2 f , r r + f , r r + f , ϑ cos ⁡ ( ϑ ) + f , ϑ ϑ sin ⁡ ( ϑ ) r 2 sin ⁡ ( ϑ ) + f , φ φ r 2 sin 2 ⁡ ( ϑ ) Δ f → = ( Δ f r − 2 r 2 ( f r + f ϑ , ϑ ) − 2 f φ , φ + f ϑ cos ⁡ ( ϑ ) r 2 sin ⁡ ( ϑ ) ) e ^ r + ( Δ f ϑ + 2 f r , ϑ r 2 − f ϑ + 2 f φ , φ cos ⁡ ( ϑ ) r 2 sin 2 ⁡ ( ϑ ) ) e ^ ϑ + ( Δ f φ − f φ − 2 f ϑ , φ cos ⁡ ( ϑ ) − 2 f r , φ sin ⁡ ( ϑ ) r 2 sin 2 ⁡ ( ϑ ) ) e ^ φ {\displaystyle {\begin{aligned}\Delta f=&{\frac {1}{r^{2}}}{\frac {\partial }{\partial r}}\left(r^{2}{\frac {\partial f}{\partial r}}\right)+{\frac {1}{r^{2}\sin(\vartheta )}}{\frac {\partial }{\partial \vartheta }}\left(\sin(\vartheta )\,{\frac {\partial f}{\partial \vartheta }}\right)+{\frac {1}{r^{2}\sin ^{2}(\vartheta )}}{\frac {\partial ^{2}f}{\partial \varphi ^{2}}}\\=&{\frac {2f_{,r}}{r}}+f_{,rr}+{\frac {f_{,\vartheta }\cos(\vartheta )+f_{,\vartheta \vartheta }\sin(\vartheta )}{r^{2}\sin(\vartheta )}}+{\frac {f_{,\varphi \varphi }}{r^{2}\sin ^{2}(\vartheta )}}\\\Delta {\vec {f}}=&\left(\Delta f_{r}-{\frac {2}{r^{2}}}(f_{r}+f_{\vartheta ,\vartheta })-2{\frac {f_{\varphi ,\varphi }+f_{\vartheta }\cos(\vartheta )}{r^{2}\sin(\vartheta )}}\right){\hat {e}}_{r}\\&+\left(\Delta f_{\vartheta }+{\frac {2f_{r,\vartheta }}{r^{2}}}-{\frac {f_{\vartheta }+2f_{\varphi ,\varphi }\cos(\vartheta )}{r^{2}\sin ^{2}(\vartheta )}}\right){\hat {e}}_{\vartheta }\\&+\left(\Delta f_{\varphi }-{\frac {f_{\varphi }-2f_{\vartheta ,\varphi }\cos(\vartheta )-2f_{r,\varphi }\sin(\vartheta )}{r^{2}\sin ^{2}(\vartheta )}}\right){\hat {e}}_{\varphi }\end{aligned}}} {\displaystyle {\begin{aligned}\Delta f=&{\frac {1}{r^{2}}}{\frac {\partial }{\partial r}}\left(r^{2}{\frac {\partial f}{\partial r}}\right)+{\frac {1}{r^{2}\sin(\vartheta )}}{\frac {\partial }{\partial \vartheta }}\left(\sin(\vartheta )\,{\frac {\partial f}{\partial \vartheta }}\right)+{\frac {1}{r^{2}\sin ^{2}(\vartheta )}}{\frac {\partial ^{2}f}{\partial \varphi ^{2}}}\\=&{\frac {2f_{,r}}{r}}+f_{,rr}+{\frac {f_{,\vartheta }\cos(\vartheta )+f_{,\vartheta \vartheta }\sin(\vartheta )}{r^{2}\sin(\vartheta )}}+{\frac {f_{,\varphi \varphi }}{r^{2}\sin ^{2}(\vartheta )}}\\\Delta {\vec {f}}=&\left(\Delta f_{r}-{\frac {2}{r^{2}}}(f_{r}+f_{\vartheta ,\vartheta })-2{\frac {f_{\varphi ,\varphi }+f_{\vartheta }\cos(\vartheta )}{r^{2}\sin(\vartheta )}}\right){\hat {e}}_{r}\\&+\left(\Delta f_{\vartheta }+{\frac {2f_{r,\vartheta }}{r^{2}}}-{\frac {f_{\vartheta }+2f_{\varphi ,\varphi }\cos(\vartheta )}{r^{2}\sin ^{2}(\vartheta )}}\right){\hat {e}}_{\vartheta }\\&+\left(\Delta f_{\varphi }-{\frac {f_{\varphi }-2f_{\vartheta ,\varphi }\cos(\vartheta )-2f_{r,\varphi }\sin(\vartheta )}{r^{2}\sin ^{2}(\vartheta )}}\right){\hat {e}}_{\varphi }\end{aligned}}}

Verknüpfungen

[Bearbeiten | Quelltext bearbeiten]

Wegen der in der Literatur teilweise abweichenden Definitionen der Differentialoperatoren kann es in der Literatur zu abweichenden Formeln kommen. Wenn die Definitionen der Literatur hier eingesetzt werden, gehen die hiesigen Formeln in die der Literatur über.

d i v ( r o t ( f → ) ) = ∇ ⋅ ( ∇ × f → ) = 0 r o t ( g r a d ( f ) ) = ∇ × ∇ f = 0 → d i v ( g r a d ( f ) × g r a d ( g ) ) = ∇ ⋅ ( ∇ f × ∇ g ) = ∇ g ⋅ ( ∇ × ∇ f ) = 0 r o t ( g r a d ( f → ) ) = ∇ × ( ∇ ⊗ f → ) = 0 d i v ( r o t ( T ) ⊤ ) = ∇ ⋅ ( ∇ × T ) = 0 → {\displaystyle {\begin{array}{rclcl}\mathrm {div(rot} ({\vec {f}}))&=&\nabla \cdot (\nabla \times {\vec {f}})&=&0\\\mathrm {rot(grad} (f))&=&\nabla \times \nabla f&=&{\vec {0}}\\\mathrm {div(grad} (f)\times \mathrm {grad} (g))&=&\nabla \cdot (\nabla f\times \nabla g)=\nabla g\cdot (\nabla \times \nabla f)&=&0\\\mathrm {rot{\big (}grad} ({\vec {f}}){\big )}&=&\nabla \times (\nabla \otimes {\vec {f}})&=&\mathbf {0} \\\mathrm {div{\big (}rot} (\mathbf {T} )^{\top }{\big )}&=&\nabla \cdot (\nabla \times \mathbf {T} )&=&{\vec {0}}\end{array}}} {\displaystyle {\begin{array}{rclcl}\mathrm {div(rot} ({\vec {f}}))&=&\nabla \cdot (\nabla \times {\vec {f}})&=&0\\\mathrm {rot(grad} (f))&=&\nabla \times \nabla f&=&{\vec {0}}\\\mathrm {div(grad} (f)\times \mathrm {grad} (g))&=&\nabla \cdot (\nabla f\times \nabla g)=\nabla g\cdot (\nabla \times \nabla f)&=&0\\\mathrm {rot{\big (}grad} ({\vec {f}}){\big )}&=&\nabla \times (\nabla \otimes {\vec {f}})&=&\mathbf {0} \\\mathrm {div{\big (}rot} (\mathbf {T} )^{\top }{\big )}&=&\nabla \cdot (\nabla \times \mathbf {T} )&=&{\vec {0}}\end{array}}}
d i v ( g r a d ( f ) ) = ∇ ⋅ ( ∇ f ) = ( ∇ ⋅ ∇ ) f = Δ f d i v ( g r a d ( f → ) ) = ∇ ⋅ ( ∇ ⊗ f → ) = ( ∇ ⋅ ∇ ) f → = Δ f → {\displaystyle {\begin{array}{rclcl}\mathrm {div{\big (}grad} (f){\big )}&=&\nabla \cdot (\nabla f)=(\nabla \cdot \nabla )f&=&\Delta f\\\mathrm {div{\big (}grad} ({\vec {f}}){\big )}&=&\nabla \cdot (\nabla \otimes {\vec {f}})=(\nabla \cdot \nabla ){\vec {f}}&=&\Delta {\vec {f}}\end{array}}} {\displaystyle {\begin{array}{rclcl}\mathrm {div{\big (}grad} (f){\big )}&=&\nabla \cdot (\nabla f)=(\nabla \cdot \nabla )f&=&\Delta f\\\mathrm {div{\big (}grad} ({\vec {f}}){\big )}&=&\nabla \cdot (\nabla \otimes {\vec {f}})=(\nabla \cdot \nabla ){\vec {f}}&=&\Delta {\vec {f}}\end{array}}}
d i v ( g r a d ( f → ) ⊤ ) = ∇ ⋅ ( ∇ ⊗ f → ⊤ ) = f i , i j e ^ j = g r a d ( d i v ( f → ) ) r o t ( g r a d ( f → ) ⊤ ) = ∇ × ( ( ∇ ⊗ f → ) ⊤ ) = ∇ × ( f → , i ⊗ e ^ i ) = g r a d ( r o t ( f → ) ) {\displaystyle {\begin{array}{rclcl}\mathrm {div{\big (}grad} ({\vec {f}})^{\top }{\big )}&=&\nabla \cdot (\nabla \otimes {\vec {f}}^{\top })=f_{i,ij}{\hat {e}}_{j}&=&\mathrm {grad{\big (}div} ({\vec {f}}){\big )}\\\mathrm {rot{\big (}grad} ({\vec {f}})^{\top }{\big )}&=&\nabla \times {\big (}(\nabla \otimes {\vec {f}})^{\top }{\big )}=\nabla \times {\big (}{\vec {f}}_{,i}\otimes {\hat {e}}_{i}{\big )}&=&\mathrm {grad{\big (}rot} ({\vec {f}}){\big )}\end{array}}} {\displaystyle {\begin{array}{rclcl}\mathrm {div{\big (}grad} ({\vec {f}})^{\top }{\big )}&=&\nabla \cdot (\nabla \otimes {\vec {f}}^{\top })=f_{i,ij}{\hat {e}}_{j}&=&\mathrm {grad{\big (}div} ({\vec {f}}){\big )}\\\mathrm {rot{\big (}grad} ({\vec {f}})^{\top }{\big )}&=&\nabla \times {\big (}(\nabla \otimes {\vec {f}})^{\top }{\big )}=\nabla \times {\big (}{\vec {f}}_{,i}\otimes {\hat {e}}_{i}{\big )}&=&\mathrm {grad{\big (}rot} ({\vec {f}}){\big )}\end{array}}}
r o t ( r o t ( f → ) ) = ∇ × ( ∇ × f → ) = ∇ ( ∇ ⋅ f → ) − Δ f → = g r a d ( d i v ( f → ) ) − Δ f → r o t ( r o t ( T ) ⊤ ) ⊤ = ( ∇ × ( ∇ × ( T ⊤ ) ) ) ⊤ = ( ∇ ⊗ ∇ ⋅ T ⊤ ) ⊤ − ( ∇ ⋅ ∇ ) T = g r a d ( d i v ( T ) ) − Δ T {\displaystyle {\begin{array}{rclcl}\mathrm {rot{\big (}rot} ({\vec {f}}){\big )}&=&\nabla \times (\nabla \times {\vec {f}})=\nabla (\nabla \cdot {\vec {f}})-\Delta {\vec {f}}&=&\mathrm {grad(div} ({\vec {f}}))-\Delta {\vec {f}}\\\mathrm {rot{\big (}rot} (\mathbf {T} )^{\top }{\big )}^{\top }&=&{\big (}\nabla \times (\nabla \times (\mathbf {T} ^{\top })){\big )}^{\top }\\&=&{\big (}\nabla \otimes \nabla \cdot \mathbf {T} ^{\top }{\big )}^{\top }-(\nabla \cdot \nabla )\mathbf {T} &=&\mathrm {grad(div} (\mathbf {T} ))-\Delta \mathbf {T} \end{array}}} {\displaystyle {\begin{array}{rclcl}\mathrm {rot{\big (}rot} ({\vec {f}}){\big )}&=&\nabla \times (\nabla \times {\vec {f}})=\nabla (\nabla \cdot {\vec {f}})-\Delta {\vec {f}}&=&\mathrm {grad(div} ({\vec {f}}))-\Delta {\vec {f}}\\\mathrm {rot{\big (}rot} (\mathbf {T} )^{\top }{\big )}^{\top }&=&{\big (}\nabla \times (\nabla \times (\mathbf {T} ^{\top })){\big )}^{\top }\\&=&{\big (}\nabla \otimes \nabla \cdot \mathbf {T} ^{\top }{\big )}^{\top }-(\nabla \cdot \nabla )\mathbf {T} &=&\mathrm {grad(div} (\mathbf {T} ))-\Delta \mathbf {T} \end{array}}}
r o t ( r o t ( T ⊤ ) ) = − Δ T − g r a d ( g r a d ( S p ( T ) ) ) + g r a d ( d i v ( T ) ) + g r a d ( d i v ( T ⊤ ) ) ⊤ + [ Δ S p ( T ) − d i v ( d i v ( T ) ) ] 1 {\displaystyle {\begin{array}{rcl}\mathrm {rot{\big (}rot} (\mathbf {T} ^{\top }){\big )}&=&-\Delta \mathbf {T} -\mathrm {grad{\big (}grad(Sp} (\mathbf {T} )){\big )}+\mathrm {grad{\big (}div} (\mathbf {T} ){\big )}+\mathrm {grad{\big (}div} (\mathbf {T} ^{\top }){\big )}^{\top }\\&&+\left[\Delta \mathrm {Sp} (\mathbf {T} )-\mathrm {div{\big (}div} (\mathbf {T} ){\big )}\right]\mathbf {1} \end{array}}} {\displaystyle {\begin{array}{rcl}\mathrm {rot{\big (}rot} (\mathbf {T} ^{\top }){\big )}&=&-\Delta \mathbf {T} -\mathrm {grad{\big (}grad(Sp} (\mathbf {T} )){\big )}+\mathrm {grad{\big (}div} (\mathbf {T} ){\big )}+\mathrm {grad{\big (}div} (\mathbf {T} ^{\top }){\big )}^{\top }\\&&+\left[\Delta \mathrm {Sp} (\mathbf {T} )-\mathrm {div{\big (}div} (\mathbf {T} ){\big )}\right]\mathbf {1} \end{array}}}

Bei symmetrischem T = T⊤ gilt:

r o t ( r o t ( T ) ) = − Δ T − g r a d ( g r a d ( S p ( T ) ) ) + g r a d ( d i v ( T ) ) + g r a d ( d i v ( T ) ) ⊤ + [ Δ S p ( T ) − d i v ( d i v ( T ) ) ] 1 {\displaystyle {\begin{array}{rcl}\mathrm {rot{\big (}rot} (\mathbf {T} ){\big )}&=&-\Delta \mathbf {T} -\mathrm {grad{\big (}grad(Sp} (\mathbf {T} )){\big )}+\mathrm {grad{\big (}div} (\mathbf {T} ){\big )}+\mathrm {grad{\big (}div} (\mathbf {T} ){\big )}^{\top }\\&&+\left[\Delta \mathrm {Sp} (\mathbf {T} )-\mathrm {div{\big (}div} (\mathbf {T} ){\big )}\right]\mathbf {1} \end{array}}} {\displaystyle {\begin{array}{rcl}\mathrm {rot{\big (}rot} (\mathbf {T} ){\big )}&=&-\Delta \mathbf {T} -\mathrm {grad{\big (}grad(Sp} (\mathbf {T} )){\big )}+\mathrm {grad{\big (}div} (\mathbf {T} ){\big )}+\mathrm {grad{\big (}div} (\mathbf {T} ){\big )}^{\top }\\&&+\left[\Delta \mathrm {Sp} (\mathbf {T} )-\mathrm {div{\big (}div} (\mathbf {T} ){\big )}\right]\mathbf {1} \end{array}}}


Wenn zusätzlich T = T ⊤ = G − S p ( G ) 1 {\displaystyle \mathbf {T} =\mathbf {T} ^{\top }=\mathbf {G} -\mathrm {Sp} (\mathbf {G} )\mathbf {1} } {\displaystyle \mathbf {T} =\mathbf {T} ^{\top }=\mathbf {G} -\mathrm {Sp} (\mathbf {G} )\mathbf {1} } dann ist:

r o t ( r o t ( T ) ) = − Δ G + g r a d ( d i v ( G ) ) + g r a d ( d i v ( G ) ) ⊤ − d i v ( d i v ( G ) ) 1 {\displaystyle \mathrm {rot{\big (}rot} (\mathbf {T} ){\big )}=-\Delta \mathbf {G} +\mathrm {grad{\big (}div} (\mathbf {G} ){\big )}+\mathrm {grad{\big (}div} (\mathbf {G} ){\big )}^{\top }-\mathrm {div{\big (}div} (\mathbf {G} ){\big )}\mathbf {1} } {\displaystyle \mathrm {rot{\big (}rot} (\mathbf {T} ){\big )}=-\Delta \mathbf {G} +\mathrm {grad{\big (}div} (\mathbf {G} ){\big )}+\mathrm {grad{\big (}div} (\mathbf {G} ){\big )}^{\top }-\mathrm {div{\big (}div} (\mathbf {G} ){\big )}\mathbf {1} }

Der Laplace-Operator kann zwischen den anderen Operatoren wie ein Skalar behandelt werden, also an beliebiger Stelle in die Formeln eingesetzt werden, z. B.:

Δ r o t ( r o t ( f → ) ) = r o t ( Δ r o t ( f → ) ) = r o t ( r o t ( Δ f → ) ) = … … = Δ g r a d ( d i v ( f → ) ) − Δ Δ f → = g r a d ( Δ d i v ( f → ) ) − Δ Δ f → = g r a d ( d i v ( Δ f → ) ) − Δ Δ f → {\displaystyle {\begin{array}{l}\Delta \mathrm {rot(rot} ({\vec {f}}))=\mathrm {rot(\Delta rot} ({\vec {f}}))=\mathrm {rot(rot} (\Delta {\vec {f}}))=\ldots \\\ldots =\Delta \mathrm {grad(div} ({\vec {f}}))-\Delta \Delta {\vec {f}}=\mathrm {grad} (\Delta \mathrm {div} ({\vec {f}}))-\Delta \Delta {\vec {f}}=\mathrm {grad(div} (\Delta {\vec {f}}))-\Delta \Delta {\vec {f}}\end{array}}} {\displaystyle {\begin{array}{l}\Delta \mathrm {rot(rot} ({\vec {f}}))=\mathrm {rot(\Delta rot} ({\vec {f}}))=\mathrm {rot(rot} (\Delta {\vec {f}}))=\ldots \\\ldots =\Delta \mathrm {grad(div} ({\vec {f}}))-\Delta \Delta {\vec {f}}=\mathrm {grad} (\Delta \mathrm {div} ({\vec {f}}))-\Delta \Delta {\vec {f}}=\mathrm {grad(div} (\Delta {\vec {f}}))-\Delta \Delta {\vec {f}}\end{array}}}

Grassmann-Entwicklung

[Bearbeiten | Quelltext bearbeiten]
f → × r o t ( f → ) = 1 2 g r a d ( f → ⋅ f → ) − g r a d ( f → ) ⋅ f → = ( g r a d ( f → ) ⊤ − g r a d ( f → ) ) ⋅ f → = i → ( g r a d ( f → ) ) × f → {\displaystyle {\begin{aligned}{\vec {f}}\times \mathrm {rot} ({\vec {f}})=&{\frac {1}{2}}\mathrm {grad} ({\vec {f}}\cdot {\vec {f}})-\mathrm {grad} ({\vec {f}})\cdot {\vec {f}}\\=&{\big (}\mathrm {grad} ({\vec {f}})^{\top }-\mathrm {grad} ({\vec {f}}){\big )}\cdot {\vec {f}}={\vec {\mathrm {i} }}{\big (}\mathrm {grad} ({\vec {f}}){\big )}\times {\vec {f}}\end{aligned}}} {\displaystyle {\begin{aligned}{\vec {f}}\times \mathrm {rot} ({\vec {f}})=&{\frac {1}{2}}\mathrm {grad} ({\vec {f}}\cdot {\vec {f}})-\mathrm {grad} ({\vec {f}})\cdot {\vec {f}}\\=&{\big (}\mathrm {grad} ({\vec {f}})^{\top }-\mathrm {grad} ({\vec {f}}){\big )}\cdot {\vec {f}}={\vec {\mathrm {i} }}{\big (}\mathrm {grad} ({\vec {f}}){\big )}\times {\vec {f}}\end{aligned}}}
g r a d ( f → ) ⋅ f → = 1 2 g r a d ( f → ⋅ f → ) − f → × r o t ( f → ) {\displaystyle \mathrm {grad} ({\vec {f}})\cdot {\vec {f}}={\frac {1}{2}}\mathrm {grad} ({\vec {f}}\cdot {\vec {f}})-{\vec {f}}\times \mathrm {rot} ({\vec {f}})} {\displaystyle \mathrm {grad} ({\vec {f}})\cdot {\vec {f}}={\frac {1}{2}}\mathrm {grad} ({\vec {f}}\cdot {\vec {f}})-{\vec {f}}\times \mathrm {rot} ({\vec {f}})}

Sätze über Gradient, Divergenz und Rotation

[Bearbeiten | Quelltext bearbeiten]

Ein Vektorfeld, dessen Divergenz und Rotation verschwindet, ist harmonisch:

div ⁡ ( f → ) = 0 und r o t ( f → ) = 0 → → Δ f → = 0 → {\displaystyle \operatorname {div} ({\vec {f}})=0\;{\text{und}}\;\mathrm {rot} ({\vec {f}})={\vec {0}}\quad \rightarrow \quad \Delta {\vec {f}}={\vec {0}}} {\displaystyle \operatorname {div} ({\vec {f}})=0\;{\text{und}}\;\mathrm {rot} ({\vec {f}})={\vec {0}}\quad \rightarrow \quad \Delta {\vec {f}}={\vec {0}}}

Helmholtz-Theorem

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Helmholtz-Theorem

Jedes Vektorfeld lässt sich eindeutig in einen divergenzfreien und einen rotationsfreien Anteil zerlegen. Den Integrabilitätsbedingungen für Rotationen und Gradienten zufolge ist der erste Anteil ein Rotationsfeld und der zweite ein Gradientenfeld.
f → = f → 1 + f → 2 : d i v ( f → 1 ) = 0 und rot ⁡ ( f → 2 ) = 0 → ↔ ∃ g , g → : f → = rot ⁡ ( g → ) + g r a d ( g ) {\displaystyle {\begin{array}{rclccl}{\vec {f}}={\vec {f}}_{1}+{\vec {f}}_{2}:&&&\mathrm {div} ({\vec {f}}_{1})=0&{\text{und}}&\operatorname {rot} ({\vec {f}}_{2})={\vec {0}}\\\leftrightarrow \exists g,{\vec {g}}:&&{\vec {f}}=&\operatorname {rot} ({\vec {g}})&+&\mathrm {grad} (g)\end{array}}} {\displaystyle {\begin{array}{rclccl}{\vec {f}}={\vec {f}}_{1}+{\vec {f}}_{2}:&&&\mathrm {div} ({\vec {f}}_{1})=0&{\text{und}}&\operatorname {rot} ({\vec {f}}_{2})={\vec {0}}\\\leftrightarrow \exists g,{\vec {g}}:&&{\vec {f}}=&\operatorname {rot} ({\vec {g}})&+&\mathrm {grad} (g)\end{array}}}

Satz über rotationsfreie Felder

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Poincaré-Lemma
I : r o t ( u → ) := e ^ k × u → , k = 0 → → ∃ f : u → = g r a d ( f ) II : r o t ( T ) = 0 → ∃ u → : T = g r a d ( u → ) III : r o t ( T ) = 0 und S p ( T ) = 0 → ∃ W : T = r o t ( W ) und W = − W ⊤ {\displaystyle {\begin{array}{rrcll}{\textsf {I}}:&\mathrm {rot} ({\vec {u}}):={\hat {e}}_{k}\times {\vec {u}}_{,k}={\vec {0}}&\rightarrow &\exists f\colon &{\vec {u}}=\mathrm {grad} (f)\\{\textsf {II}}:&\mathrm {rot} (\mathbf {T} )=\mathbf {0} &\rightarrow &\exists {\vec {u}}\colon &\mathbf {T} =\mathrm {grad} ({\vec {u}})\\{\textsf {III}}:&\mathrm {rot} (\mathbf {T} )=\mathbf {0} \;{\text{und}}\;\mathrm {Sp} (\mathbf {T} )=0&\rightarrow &\exists \mathbf {W} \colon &\mathbf {T} =\mathrm {rot} (\mathbf {W} )\;{\text{und}}\;\mathbf {W} =-\mathbf {W} ^{\top }\end{array}}} {\displaystyle {\begin{array}{rrcll}{\textsf {I}}:&\mathrm {rot} ({\vec {u}}):={\hat {e}}_{k}\times {\vec {u}}_{,k}={\vec {0}}&\rightarrow &\exists f\colon &{\vec {u}}=\mathrm {grad} (f)\\{\textsf {II}}:&\mathrm {rot} (\mathbf {T} )=\mathbf {0} &\rightarrow &\exists {\vec {u}}\colon &\mathbf {T} =\mathrm {grad} ({\vec {u}})\\{\textsf {III}}:&\mathrm {rot} (\mathbf {T} )=\mathbf {0} \;{\text{und}}\;\mathrm {Sp} (\mathbf {T} )=0&\rightarrow &\exists \mathbf {W} \colon &\mathbf {T} =\mathrm {rot} (\mathbf {W} )\;{\text{und}}\;\mathbf {W} =-\mathbf {W} ^{\top }\end{array}}}

oder

II : ∇ × ( T ⊤ ) = 0 → ∃ u → : T = g r a d ( u → ) III : ∇ × ( T ⊤ ) = 0 und S p ( T ) = 0 → ∃ W : T = r o t ( W ) und W = − W ⊤ {\displaystyle {\begin{array}{rrcll}{\textsf {II}}:&\nabla \times (\mathbf {T} ^{\top })=\mathbf {0} &\rightarrow &\exists {\vec {u}}\colon &\mathbf {T} =\mathrm {grad} ({\vec {u}})\\{\textsf {III}}:&\nabla \times (\mathbf {T} ^{\top })=\mathbf {0} \;{\text{und}}\;\mathrm {Sp} (\mathbf {T} )=0&\rightarrow &\exists \mathbf {W} \colon &\mathbf {T} =\mathrm {rot} (\mathbf {W} )\;{\text{und}}\;\mathbf {W} =-\mathbf {W} ^{\top }\end{array}}} {\displaystyle {\begin{array}{rrcll}{\textsf {II}}:&\nabla \times (\mathbf {T} ^{\top })=\mathbf {0} &\rightarrow &\exists {\vec {u}}\colon &\mathbf {T} =\mathrm {grad} ({\vec {u}})\\{\textsf {III}}:&\nabla \times (\mathbf {T} ^{\top })=\mathbf {0} \;{\text{und}}\;\mathrm {Sp} (\mathbf {T} )=0&\rightarrow &\exists \mathbf {W} \colon &\mathbf {T} =\mathrm {rot} (\mathbf {W} )\;{\text{und}}\;\mathbf {W} =-\mathbf {W} ^{\top }\end{array}}}

Gaußscher Integralsatz

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Gaußscher Integralsatz
  • Volumen v {\displaystyle v} {\displaystyle v} mit Volumenform d v {\displaystyle \mathrm {d} v} {\displaystyle \mathrm {d} v} und
  • Oberfläche a {\displaystyle a} {\displaystyle a} mit äußerem vektoriellem Oberflächenelement d a → {\displaystyle \mathrm {d} {\vec {a}}} {\displaystyle \mathrm {d} {\vec {a}}}
  • Ortsvektoren x → ∈ v {\displaystyle {\vec {x}}\in v} {\displaystyle {\vec {x}}\in v}
  • Skalar-, vektor- oder tensorwertige Funktion f , f → , T {\displaystyle f,{\vec {f}},\mathbf {T} } {\displaystyle f,{\vec {f}},\mathbf {T} } des Ortes x → {\displaystyle {\vec {x}}} {\displaystyle {\vec {x}}} :
∫ v g r a d ( f ) d v = ∫ a f d a → ∫ v g r a d ( f → ) d v = ∫ a f → ⊗ d a → ∫ v d i v ( f → ) d v = ∫ a f → ⋅ d a → ∫ v r o t ( f → ) d v = − ∫ a f → × d a → ∫ v d i v ( T ) d v = ∫ a T ⋅ d a → ∫ v ∇ ⋅ T d v = ∫ a T ⊤ ⋅ d a → {\displaystyle {\begin{array}{rcl}\int _{v}\mathrm {grad} (f)\,\mathrm {d} v&=&\int _{a}f\,\mathrm {d} {\vec {a}}\\\int _{v}\mathrm {grad} ({\vec {f}})\,\mathrm {d} v&=&\int _{a}{\vec {f}}\otimes \mathrm {d} {\vec {a}}\\\int _{v}\mathrm {div} ({\vec {f}})\,\mathrm {d} v&=&\int _{a}{\vec {f}}\cdot \mathrm {d} {\vec {a}}\\\int _{v}\mathrm {rot} ({\vec {f}})\,\mathrm {d} v&=&-\int _{a}{\vec {f}}\times \mathrm {d} {\vec {a}}\\\int _{v}\mathrm {div} (\mathbf {T} )\,\mathrm {d} v&=&\int _{a}\mathbf {T} \cdot \mathrm {d} {\vec {a}}\\\int _{v}\nabla \cdot \mathbf {T} \,\mathrm {d} v&=&\int _{a}\mathbf {T} ^{\top }\cdot \mathrm {d} {\vec {a}}\end{array}}} {\displaystyle {\begin{array}{rcl}\int _{v}\mathrm {grad} (f)\,\mathrm {d} v&=&\int _{a}f\,\mathrm {d} {\vec {a}}\\\int _{v}\mathrm {grad} ({\vec {f}})\,\mathrm {d} v&=&\int _{a}{\vec {f}}\otimes \mathrm {d} {\vec {a}}\\\int _{v}\mathrm {div} ({\vec {f}})\,\mathrm {d} v&=&\int _{a}{\vec {f}}\cdot \mathrm {d} {\vec {a}}\\\int _{v}\mathrm {rot} ({\vec {f}})\,\mathrm {d} v&=&-\int _{a}{\vec {f}}\times \mathrm {d} {\vec {a}}\\\int _{v}\mathrm {div} (\mathbf {T} )\,\mathrm {d} v&=&\int _{a}\mathbf {T} \cdot \mathrm {d} {\vec {a}}\\\int _{v}\nabla \cdot \mathbf {T} \,\mathrm {d} v&=&\int _{a}\mathbf {T} ^{\top }\cdot \mathrm {d} {\vec {a}}\end{array}}}

Mit der #Produktregel für Gradienten, #Produktregel für Divergenzen und #Produktregel für Rotationen können Formeln für die partielle Integration im Mehrdimensionalen abgeleitet werden, beispielsweise:

g r a d ( f g ) = g r a d ( f ) g + f g r a d ( g ) → ∫ v g r a d ( f ) g d v = ∫ a f g d a → − ∫ v f g r a d ( g ) d v {\displaystyle {\begin{aligned}\mathrm {grad} (fg)=&\mathrm {grad} (f)g+f\mathrm {grad} (g)\\\rightarrow \int _{v}\mathrm {grad} (f)g\,\mathrm {d} v=&\int _{a}fg\,\mathrm {d} {\vec {a}}-\int _{v}f\mathrm {grad} (g)\,\mathrm {d} v\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {grad} (fg)=&\mathrm {grad} (f)g+f\mathrm {grad} (g)\\\rightarrow \int _{v}\mathrm {grad} (f)g\,\mathrm {d} v=&\int _{a}fg\,\mathrm {d} {\vec {a}}-\int _{v}f\mathrm {grad} (g)\,\mathrm {d} v\end{aligned}}}

Klassischer Integralsatz von Stokes

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Satz von Stokes

Gegeben:

  • Fläche a {\displaystyle a} {\displaystyle a} mit äußerem vektoriellem Oberflächenelement d a → {\displaystyle \mathrm {d} {\vec {a}}} {\displaystyle \mathrm {d} {\vec {a}}}
  • Berandungskurve b {\displaystyle b} {\displaystyle b} der Fläche a {\displaystyle a} {\displaystyle a} mit Linienelement d b → {\displaystyle \mathrm {d} {\vec {b}}} {\displaystyle \mathrm {d} {\vec {b}}}
  • Ortsvektoren x → ∈ a {\displaystyle {\vec {x}}\in a} {\displaystyle {\vec {x}}\in a}

Vektorwertige Funktion f → ( x → , t ) {\displaystyle {\vec {f}}({\vec {x}},t)} {\displaystyle {\vec {f}}({\vec {x}},t)} :

∫ a r o t ( f → ) ⋅ d a → = ∮ b f → ⋅ d b → {\displaystyle \int _{a}\mathrm {rot} ({\vec {f}})\cdot \mathrm {d} {\vec {a}}=\oint _{b}{\vec {f}}\cdot \mathrm {d} {\vec {b}}} {\displaystyle \int _{a}\mathrm {rot} ({\vec {f}})\cdot \mathrm {d} {\vec {a}}=\oint _{b}{\vec {f}}\cdot \mathrm {d} {\vec {b}}}

Mit der #Produktregel für Rotationen können Formeln für die partielle Integration im Mehrdimensionalen abgeleitet werden, beispielsweise:

r o t ( f g → ) = g r a d ( f ) × g → + f r o t ( g → ) → ∫ a ( g r a d ( f ) × g → ) ⋅ d a → = ∮ b f g → ⋅ d b → − ∫ a f r o t ( g → ) ⋅ d a → {\displaystyle {\begin{aligned}\mathrm {rot} (f{\vec {g}})=&\mathrm {grad} (f)\times {\vec {g}}+f\mathrm {rot} ({\vec {g}})\\\rightarrow \int _{a}{\big (}\mathrm {grad} (f)\times {\vec {g}}{\big )}\cdot \mathrm {d} {\vec {a}}=&\oint _{b}f{\vec {g}}\cdot \mathrm {d} {\vec {b}}-\int _{a}f\mathrm {rot} ({\vec {g}})\cdot \mathrm {d} {\vec {a}}\end{aligned}}} {\displaystyle {\begin{aligned}\mathrm {rot} (f{\vec {g}})=&\mathrm {grad} (f)\times {\vec {g}}+f\mathrm {rot} ({\vec {g}})\\\rightarrow \int _{a}{\big (}\mathrm {grad} (f)\times {\vec {g}}{\big )}\cdot \mathrm {d} {\vec {a}}=&\oint _{b}f{\vec {g}}\cdot \mathrm {d} {\vec {b}}-\int _{a}f\mathrm {rot} ({\vec {g}})\cdot \mathrm {d} {\vec {a}}\end{aligned}}}

Reynoldscher Transportsatz

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Reynolds’scher Transportsatz

Gegeben:

  • Zeit t {\displaystyle t} {\displaystyle t}
  • Zeitabhängiges Volumen v {\displaystyle v} {\displaystyle v} mit Volumenform d v {\displaystyle \mathrm {d} v} {\displaystyle \mathrm {d} v} mit
  • Oberfläche des Volumes a {\displaystyle a} {\displaystyle a} und äußerem vektoriellem Oberflächenelement d a → {\displaystyle \mathrm {d} {\vec {a}}} {\displaystyle \mathrm {d} {\vec {a}}}
  • Ortsvektoren x → ∈ v {\displaystyle {\vec {x}}\in v} {\displaystyle {\vec {x}}\in v}
  • Geschwindigkeitsfeld: v → ( x → , t ) {\displaystyle {\vec {v}}({\vec {x}},t)} {\displaystyle {\vec {v}}({\vec {x}},t)}
  • Eine skalare oder vektorwertige Dichtefunktion pro Volumeneinheit f ( x → , t ) {\displaystyle f({\vec {x}},t)} {\displaystyle f({\vec {x}},t)}, die mit den sich bewegenden Partikeln transportiert wird.
  • Die Integrale Größe für das Volumen: ∫ v f → ( x → , t ) d v {\displaystyle \int _{v}{\vec {f}}({\vec {x}},t)\,\mathrm {d} v} {\displaystyle \int _{v}{\vec {f}}({\vec {x}},t)\,\mathrm {d} v}

Skalare Funktion f ( x → , t ) {\displaystyle f({\vec {x}},t)} {\displaystyle f({\vec {x}},t)} :

d d t ∫ v f d v = ∫ v ∂ f ∂ t d v + ∫ a f ( v → ⋅ d a → ) = ∫ v ( ∂ f ∂ t + d i v ( f v → ) ) d v = ∫ v ( ∂ f ∂ t + g r a d ( f ) ⋅ v → + d i v ( v → ) f ) d v = ∫ v ( f ˙ + d i v ( v → ) f ) d v {\displaystyle {\begin{array}{rcl}{\frac {\mathrm {d} }{\mathrm {d} t}}\int _{v}f\,\mathrm {d} v&=&\int _{v}{\frac {\partial f}{\partial t}}\,\mathrm {d} v+\int _{a}f({\vec {v}}\cdot \mathrm {d} {\vec {a}})=\int _{v}\left({\frac {\partial f}{\partial t}}+\mathrm {div} (f{\vec {v}})\right)\,\mathrm {d} v\\&=&\int _{v}\left({\frac {\partial f}{\partial t}}+\mathrm {grad} (f)\cdot {\vec {v}}+\mathrm {div} ({\vec {v}})\,f\right)\,\mathrm {d} v=\int _{v}\left({\dot {f}}+\mathrm {div} ({\vec {v}})\,f\right)\,\mathrm {d} v\end{array}}} {\displaystyle {\begin{array}{rcl}{\frac {\mathrm {d} }{\mathrm {d} t}}\int _{v}f\,\mathrm {d} v&=&\int _{v}{\frac {\partial f}{\partial t}}\,\mathrm {d} v+\int _{a}f({\vec {v}}\cdot \mathrm {d} {\vec {a}})=\int _{v}\left({\frac {\partial f}{\partial t}}+\mathrm {div} (f{\vec {v}})\right)\,\mathrm {d} v\\&=&\int _{v}\left({\frac {\partial f}{\partial t}}+\mathrm {grad} (f)\cdot {\vec {v}}+\mathrm {div} ({\vec {v}})\,f\right)\,\mathrm {d} v=\int _{v}\left({\dot {f}}+\mathrm {div} ({\vec {v}})\,f\right)\,\mathrm {d} v\end{array}}}

Vektorwertige Funktion f → ( x → , t ) {\displaystyle {\vec {f}}({\vec {x}},t)} {\displaystyle {\vec {f}}({\vec {x}},t)} :

d d t ∫ v f → d v = ∫ v ∂ f → ∂ t d v + ∫ a f → ( v → ⋅ d a → ) = ∫ v ( ∂ f → ∂ t + d i v ( v → ⊗ f → ) ) d v = ∫ v ( ∂ f → ∂ t + g r a d ( f → ) ⋅ v → + d i v ( v → ) f → ) d v = ∫ v ( f → ˙ + d i v ( v → ) f → ) d v {\displaystyle {\begin{array}{rcl}{\frac {\mathrm {d} }{\mathrm {d} t}}\int _{v}{\vec {f}}\,\mathrm {d} v&=&\int _{v}{\frac {\partial {\vec {f}}}{\partial t}}\,\mathrm {d} v+\int _{a}{\vec {f}}({\vec {v}}\cdot \mathrm {d} {\vec {a}})=\int _{v}\left({\frac {\partial {\vec {f}}}{\partial t}}+\mathrm {div} ({\vec {v}}\otimes {\vec {f}})\right)\,\mathrm {d} v\\&=&\int _{v}\left({\frac {\partial {\vec {f}}}{\partial t}}+\mathrm {grad} ({\vec {f}})\cdot {\vec {v}}+\mathrm {div} ({\vec {v}}){\vec {f}}\right)\,\mathrm {d} v=\int _{v}({\dot {\vec {f}}}+\mathrm {div} ({\vec {v}}){\vec {f}})\,\mathrm {d} v\end{array}}} {\displaystyle {\begin{array}{rcl}{\frac {\mathrm {d} }{\mathrm {d} t}}\int _{v}{\vec {f}}\,\mathrm {d} v&=&\int _{v}{\frac {\partial {\vec {f}}}{\partial t}}\,\mathrm {d} v+\int _{a}{\vec {f}}({\vec {v}}\cdot \mathrm {d} {\vec {a}})=\int _{v}\left({\frac {\partial {\vec {f}}}{\partial t}}+\mathrm {div} ({\vec {v}}\otimes {\vec {f}})\right)\,\mathrm {d} v\\&=&\int _{v}\left({\frac {\partial {\vec {f}}}{\partial t}}+\mathrm {grad} ({\vec {f}})\cdot {\vec {v}}+\mathrm {div} ({\vec {v}}){\vec {f}}\right)\,\mathrm {d} v=\int _{v}({\dot {\vec {f}}}+\mathrm {div} ({\vec {v}}){\vec {f}})\,\mathrm {d} v\end{array}}}

Transportsatz für Flächenintegrale

[Bearbeiten | Quelltext bearbeiten]

Gegeben:

  • Zeit t {\displaystyle t} {\displaystyle t}
  • Ortsvektoren x → ∈ v {\displaystyle {\vec {x}}\in v} {\displaystyle {\vec {x}}\in v}
  • Geschwindigkeitsfeld: v → ( x → , t ) {\displaystyle {\vec {v}}({\vec {x}},t)} {\displaystyle {\vec {v}}({\vec {x}},t)}
  • Zeitabhängige Fläche a : [ 0 , 1 ] 2 ↦ v {\displaystyle a\colon [0,1]^{2}\mapsto v} {\displaystyle a\colon [0,1]^{2}\mapsto v}, die mit dem Geschwindigkeitsfeld transportiert wird und auf der mit räumlichem, vektoriellem Oberflächenelement d a → {\displaystyle \mathrm {d} {\vec {a}}} {\displaystyle \mathrm {d} {\vec {a}}} im Volumen v integriert wird
  • Eine skalare oder vektorwertige Feldgröße f ( x → , t ) {\displaystyle f({\vec {x}},t)} {\displaystyle f({\vec {x}},t)}, die mit den sich bewegenden Partikeln transportiert wird.
  • Die Integrale Größe auf der Fläche: ∫ a f ( x → , t ) ⋅ d a → {\displaystyle \int _{a}f({\vec {x}},t)\cdot \mathrm {d} {\vec {a}}} {\displaystyle \int _{a}f({\vec {x}},t)\cdot \mathrm {d} {\vec {a}}}

Skalare Funktion f ( x → , t ) {\displaystyle f({\vec {x}},t)} {\displaystyle f({\vec {x}},t)} :

d d t ∫ a f d a → = ∫ a [ f ˙ 1 + f div ⁡ ( v → ) 1 − f grad ⁡ ( v → ) ⊤ ] ⋅ d a → {\displaystyle {\frac {\mathrm {d} }{\mathrm {d} t}}\int _{a}f\,\mathrm {d} {\vec {a}}=\int _{a}[{\dot {f}}\mathbf {1} +f\operatorname {div} ({\vec {v}})\mathbf {1} -f\operatorname {grad} ({\vec {v}})^{\top }]\cdot \,\mathrm {d} {\vec {a}}} {\displaystyle {\frac {\mathrm {d} }{\mathrm {d} t}}\int _{a}f\,\mathrm {d} {\vec {a}}=\int _{a}[{\dot {f}}\mathbf {1} +f\operatorname {div} ({\vec {v}})\mathbf {1} -f\operatorname {grad} ({\vec {v}})^{\top }]\cdot \,\mathrm {d} {\vec {a}}}

Vektorwertige Funktion f → ( x → , t ) {\displaystyle {\vec {f}}({\vec {x}},t)} {\displaystyle {\vec {f}}({\vec {x}},t)}:

d d t ∫ a f → ⋅ d a → = ∫ a [ f → ˙ + f → div ⁡ ( v → ) − grad ⁡ ( v → ) ⋅ f → ] ⋅ d a → {\displaystyle {\frac {\mathrm {d} }{\mathrm {d} t}}\int _{a}{\vec {f}}\cdot \,\mathrm {d} {\vec {a}}=\int _{a}[{\dot {\vec {f}}}+{\vec {f}}\operatorname {div} ({\vec {v}})-\operatorname {grad} ({\vec {v}})\cdot {\vec {f}}]\cdot \,\mathrm {d} {\vec {a}}} {\displaystyle {\frac {\mathrm {d} }{\mathrm {d} t}}\int _{a}{\vec {f}}\cdot \,\mathrm {d} {\vec {a}}=\int _{a}[{\dot {\vec {f}}}+{\vec {f}}\operatorname {div} ({\vec {v}})-\operatorname {grad} ({\vec {v}})\cdot {\vec {f}}]\cdot \,\mathrm {d} {\vec {a}}}

Transportsatz für Kurvenintegrale

[Bearbeiten | Quelltext bearbeiten]

Gegeben:

  • Zeit t {\displaystyle t} {\displaystyle t}
  • Ortsvektoren x → ∈ v {\displaystyle {\vec {x}}\in v} {\displaystyle {\vec {x}}\in v}
  • Geschwindigkeitsfeld: v → ( x → , t ) {\displaystyle {\vec {v}}({\vec {x}},t)} {\displaystyle {\vec {v}}({\vec {x}},t)}
  • Zeitabhängige Kurve b : [ 0 , 1 ) ↦ v {\displaystyle b\colon [0,1)\mapsto v} {\displaystyle b\colon [0,1)\mapsto v}, die mit dem Geschwindigkeitsfeld transportiert wird und entlang derer mit räumlichem, vektoriellem Linienelement d b → {\displaystyle \mathrm {d} {\vec {b}}} {\displaystyle \mathrm {d} {\vec {b}}} im Volumen v integriert wird
  • Eine skalare oder vektorwertige Feldgröße f ( x → , t ) {\displaystyle f({\vec {x}},t)} {\displaystyle f({\vec {x}},t)}, die mit den sich bewegenden Partikeln transportiert wird.
  • Die Integrale Größe entlang des Weges: ∫ b f ( x → , t ) ⋅ d b → {\displaystyle \int _{b}f({\vec {x}},t)\cdot \mathrm {d} {\vec {b}}} {\displaystyle \int _{b}f({\vec {x}},t)\cdot \mathrm {d} {\vec {b}}}

Skalare Funktion f ( x → , t ) {\displaystyle f({\vec {x}},t)} {\displaystyle f({\vec {x}},t)} :

d d t ∮ b f d b → = ∮ b ( f ˙ 1 + f g r a d v → ) ⋅ d b → {\displaystyle {\frac {\mathrm {d} }{\mathrm {d} t}}\oint _{b}f\,\mathrm {d} {\vec {b}}=\oint _{b}({\dot {f}}\mathbf {1} +f\,\mathrm {grad} {\vec {v}})\cdot \mathrm {d} {\vec {b}}} {\displaystyle {\frac {\mathrm {d} }{\mathrm {d} t}}\oint _{b}f\,\mathrm {d} {\vec {b}}=\oint _{b}({\dot {f}}\mathbf {1} +f\,\mathrm {grad} {\vec {v}})\cdot \mathrm {d} {\vec {b}}}

Vektorwertige Funktion f → ( x → , t ) {\displaystyle {\vec {f}}({\vec {x}},t)} {\displaystyle {\vec {f}}({\vec {x}},t)}:

d d t ∮ b f → ⋅ d b → = ∮ b ( f → ˙ + f → ⋅ g r a d v → ) ⋅ d b → {\displaystyle {\frac {\mathrm {d} }{\mathrm {d} t}}\oint _{b}{\vec {f}}\cdot \mathrm {d} {\vec {b}}=\oint _{b}({\dot {\vec {f}}}+{\vec {f}}\cdot \mathrm {grad} {\vec {v}})\cdot \mathrm {d} {\vec {b}}} {\displaystyle {\frac {\mathrm {d} }{\mathrm {d} t}}\oint _{b}{\vec {f}}\cdot \mathrm {d} {\vec {b}}=\oint _{b}({\dot {\vec {f}}}+{\vec {f}}\cdot \mathrm {grad} {\vec {v}})\cdot \mathrm {d} {\vec {b}}}

Kontinuumsmechanik

[Bearbeiten | Quelltext bearbeiten]

Kleine Deformationen

[Bearbeiten | Quelltext bearbeiten]

Ingenieursdehnungen:

ε = ε i j e ^ i ⊗ e ^ j = 1 2 ( u i , j + u j , i ) e ^ i ⊗ e ^ j {\displaystyle {\boldsymbol {\varepsilon }}=\varepsilon _{ij}{\hat {e}}_{i}\otimes {\hat {e}}_{j}={\frac {1}{2}}(u_{i,j}+u_{j,i}){\hat {e}}_{i}\otimes {\hat {e}}_{j}} {\displaystyle {\boldsymbol {\varepsilon }}=\varepsilon _{ij}{\hat {e}}_{i}\otimes {\hat {e}}_{j}={\frac {1}{2}}(u_{i,j}+u_{j,i}){\hat {e}}_{i}\otimes {\hat {e}}_{j}}

Kompatibilitätsbedingungen:

r o t ( r o t ( ε ) ) = ∇ × ( ∇ × ε ) ⊤ = 0 ↓ 2 ε 12 , 12 − ε 22 , 11 − ε 11 , 22 = 0 2 ε 13 , 13 − ε 33 , 11 − ε 11 , 33 = 0 2 ε 23 , 23 − ε 33 , 22 − ε 22 , 33 = 0 ε 11 , 23 + ε 23 , 11 − ε 12 , 13 − ε 13 , 12 = 0 ε 22 , 13 + ε 13 , 22 − ε 12 , 23 − ε 23 , 12 = 0 ε 12 , 33 + ε 33 , 12 − ε 13 , 23 − ε 23 , 13 = 0 {\displaystyle {\begin{array}{rcl}\mathrm {rot{\big (}rot} ({\boldsymbol {\varepsilon }}){\big )}=\nabla \times (\nabla \times {\boldsymbol {\varepsilon }})^{\top }&=&\mathbf {0} \\&\downarrow &\\2\varepsilon _{12,12}-\varepsilon _{22,11}-\varepsilon _{11,22}&=&0\\2\varepsilon _{13,13}-\varepsilon _{33,11}-\varepsilon _{11,33}&=&0\\2\varepsilon _{23,23}-\varepsilon _{33,22}-\varepsilon _{22,33}&=&0\\\varepsilon _{11,23}+\varepsilon _{23,11}-\varepsilon _{12,13}-\varepsilon _{13,12}&=&0\\\varepsilon _{22,13}+\varepsilon _{13,22}-\varepsilon _{12,23}-\varepsilon _{23,12}&=&0\\\varepsilon _{12,33}+\varepsilon _{33,12}-\varepsilon _{13,23}-\varepsilon _{23,13}&=&0\end{array}}} {\displaystyle {\begin{array}{rcl}\mathrm {rot{\big (}rot} ({\boldsymbol {\varepsilon }}){\big )}=\nabla \times (\nabla \times {\boldsymbol {\varepsilon }})^{\top }&=&\mathbf {0} \\&\downarrow &\\2\varepsilon _{12,12}-\varepsilon _{22,11}-\varepsilon _{11,22}&=&0\\2\varepsilon _{13,13}-\varepsilon _{33,11}-\varepsilon _{11,33}&=&0\\2\varepsilon _{23,23}-\varepsilon _{33,22}-\varepsilon _{22,33}&=&0\\\varepsilon _{11,23}+\varepsilon _{23,11}-\varepsilon _{12,13}-\varepsilon _{13,12}&=&0\\\varepsilon _{22,13}+\varepsilon _{13,22}-\varepsilon _{12,23}-\varepsilon _{23,12}&=&0\\\varepsilon _{12,33}+\varepsilon _{33,12}-\varepsilon _{13,23}-\varepsilon _{23,13}&=&0\end{array}}}

Starrkörperbewegung

[Bearbeiten | Quelltext bearbeiten]

Orthogonaler Tensor Q {\displaystyle \mathbf {Q} } {\displaystyle \mathbf {Q} } beschreibt die Drehung.

Ω := Q ˙ ⋅ Q ⊤ = ( Q ⋅ Q ˙ ⊤ ) ⊤ = − Q ⋅ Q ˙ ⊤ {\displaystyle \mathbf {\Omega } :={\dot {\mathbf {Q} }}\cdot \mathbf {Q} ^{\top }={(\mathbf {Q} \cdot {\dot {\mathbf {Q} }}^{\top })}^{\top }=-\mathbf {Q} \cdot {\dot {\mathbf {Q} }}^{\top }} {\displaystyle \mathbf {\Omega } :={\dot {\mathbf {Q} }}\cdot \mathbf {Q} ^{\top }={(\mathbf {Q} \cdot {\dot {\mathbf {Q} }}^{\top })}^{\top }=-\mathbf {Q} \cdot {\dot {\mathbf {Q} }}^{\top }}

Vektorinvariante oder dualer axialer Vektor ω → {\displaystyle {\vec {\omega }}} {\displaystyle {\vec {\omega }}} des schiefsymmetrischen Tensors Ω {\displaystyle \mathbf {\Omega } } {\displaystyle \mathbf {\Omega } } ist die Winkelgeschwindigkeit:

Ω ⋅ r → = ω → × r → ∀ r → {\displaystyle \mathbf {\Omega } \cdot {\vec {r}}={\vec {\omega }}\times {\vec {r}}{\quad \forall \;}{\vec {r}}} {\displaystyle \mathbf {\Omega } \cdot {\vec {r}}={\vec {\omega }}\times {\vec {r}}{\quad \forall \;}{\vec {r}}}

Starrkörperbewegung mit r → = c o n s t . {\displaystyle {\vec {r}}=\mathrm {const.} } {\displaystyle {\vec {r}}=\mathrm {const.} } :

x → = f → + Q ⋅ r → → r → = Q ⊤ ⋅ ( x → − f → ) {\displaystyle {\vec {x}}={\vec {f}}+\mathbf {Q} \cdot {\vec {r}}\quad \rightarrow \quad {\vec {r}}=\mathbf {Q} ^{\top }\cdot ({\vec {x}}-{\vec {f}})} {\displaystyle {\vec {x}}={\vec {f}}+\mathbf {Q} \cdot {\vec {r}}\quad \rightarrow \quad {\vec {r}}=\mathbf {Q} ^{\top }\cdot ({\vec {x}}-{\vec {f}})}
v → = f → ˙ + Q ˙ ⋅ r → = f → ˙ + Q ˙ ⋅ Q ⊤ ⋅ ( x → − f → ) = f → ˙ + Ω ⋅ ( x → − f → ) = f → ˙ + ω → × ( x → − f → ) {\displaystyle {\vec {v}}={\dot {\vec {f}}}+{\dot {\mathbf {Q} }}\cdot {\vec {r}}={\dot {\vec {f}}}+{\dot {\mathbf {Q} }}\cdot \mathbf {Q} ^{\top }\cdot ({\vec {x}}-{\vec {f}})={\dot {\vec {f}}}+\mathbf {\Omega } \cdot ({\vec {x}}-{\vec {f}})={\dot {\vec {f}}}+{\vec {\omega }}\times ({\vec {x}}-{\vec {f}})} {\displaystyle {\vec {v}}={\dot {\vec {f}}}+{\dot {\mathbf {Q} }}\cdot {\vec {r}}={\dot {\vec {f}}}+{\dot {\mathbf {Q} }}\cdot \mathbf {Q} ^{\top }\cdot ({\vec {x}}-{\vec {f}})={\dot {\vec {f}}}+\mathbf {\Omega } \cdot ({\vec {x}}-{\vec {f}})={\dot {\vec {f}}}+{\vec {\omega }}\times ({\vec {x}}-{\vec {f}})}

Ableitungen der Invarianten

[Bearbeiten | Quelltext bearbeiten]
∂ I 1 ( T ) ∂ T = ∂ S p ( T ) ∂ T = 1 {\displaystyle {\frac {\partial \mathrm {I} _{1}(\mathbf {T} )}{\partial \mathbf {T} }}={\frac {\partial \mathrm {Sp} (\mathbf {T} )}{\partial \mathbf {T} }}=\mathbf {1} } {\displaystyle {\frac {\partial \mathrm {I} _{1}(\mathbf {T} )}{\partial \mathbf {T} }}={\frac {\partial \mathrm {Sp} (\mathbf {T} )}{\partial \mathbf {T} }}=\mathbf {1} }
∂ I 2 ( T ) ∂ T = I 1 ( T ) 1 − T ⊤ {\displaystyle {\frac {\partial \mathrm {I} _{2}(\mathbf {T} )}{\partial \mathbf {T} }}=\mathrm {I} _{1}(\mathbf {T} )\mathbf {1} -\mathbf {T} ^{\top }} {\displaystyle {\frac {\partial \mathrm {I} _{2}(\mathbf {T} )}{\partial \mathbf {T} }}=\mathrm {I} _{1}(\mathbf {T} )\mathbf {1} -\mathbf {T} ^{\top }}
∂ I 3 ( T ) ∂ T = ∂ d e t ( T ) ∂ T = d e t ( T ) T ⊤ − 1 = c o f ( T ) = T ⊤ ⋅ T ⊤ − I 1 ( T ) T ⊤ + I 2 ( T ) 1 {\displaystyle {\frac {\partial \mathrm {I} _{3}(\mathbf {T} )}{\partial \mathbf {T} }}={\frac {\partial \mathrm {det} (\mathbf {T} )}{\partial \mathbf {T} }}=\mathrm {det} (\mathbf {T} )\mathbf {T} ^{\top -1}=\mathrm {cof} (\mathbf {T} )=\mathbf {T^{\top }\cdot T^{\top }} -\mathrm {I} _{1}(\mathbf {T} )\mathbf {T} ^{\top }+\mathrm {I} _{2}(\mathbf {T} )\mathbf {1} } {\displaystyle {\frac {\partial \mathrm {I} _{3}(\mathbf {T} )}{\partial \mathbf {T} }}={\frac {\partial \mathrm {det} (\mathbf {T} )}{\partial \mathbf {T} }}=\mathrm {det} (\mathbf {T} )\mathbf {T} ^{\top -1}=\mathrm {cof} (\mathbf {T} )=\mathbf {T^{\top }\cdot T^{\top }} -\mathrm {I} _{1}(\mathbf {T} )\mathbf {T} ^{\top }+\mathrm {I} _{2}(\mathbf {T} )\mathbf {1} }

mit der transponiert inversen T⊤-1 und dem Kofaktor cof(T) des Tensors T.

Funktion f {\displaystyle f} {\displaystyle f} der Invarianten:

∂ f ∂ T ( I 1 ( T ) , I 2 ( T ) , I 3 ( T ) ) = ( ∂ f ∂ I 1 + I 1 ∂ f ∂ I 2 + I 2 ∂ f ∂ I 3 ) 1 − ( ∂ f ∂ I 2 + I 1 ∂ f ∂ I 3 ) T ⊤ + ∂ f ∂ I 3 T ⊤ ⋅ T ⊤ {\displaystyle {\begin{aligned}{\frac {\partial f}{\partial \mathbf {T} }}(\mathrm {I} _{1}(\mathbf {T} ),\,\mathrm {I} _{2}(\mathbf {T} ),\,\mathrm {I} _{3}(\mathbf {T} ))=&\left({\frac {\partial f}{\partial \mathrm {I} _{1}}}+\mathrm {I} _{1}{\frac {\partial f}{\partial \mathrm {I} _{2}}}+\mathrm {I} _{2}{\frac {\partial f}{\partial \mathrm {I} _{3}}}\right)\mathbf {1} -\left({\frac {\partial f}{\partial \mathrm {I} _{2}}}+\mathrm {I} _{1}{\frac {\partial f}{\partial \mathrm {I} _{3}}}\right)\mathbf {T} ^{\top }\\&+{\frac {\partial f}{\partial \mathrm {I} _{3}}}\mathbf {T} ^{\top }\cdot \mathbf {T} ^{\top }\end{aligned}}} {\displaystyle {\begin{aligned}{\frac {\partial f}{\partial \mathbf {T} }}(\mathrm {I} _{1}(\mathbf {T} ),\,\mathrm {I} _{2}(\mathbf {T} ),\,\mathrm {I} _{3}(\mathbf {T} ))=&\left({\frac {\partial f}{\partial \mathrm {I} _{1}}}+\mathrm {I} _{1}{\frac {\partial f}{\partial \mathrm {I} _{2}}}+\mathrm {I} _{2}{\frac {\partial f}{\partial \mathrm {I} _{3}}}\right)\mathbf {1} -\left({\frac {\partial f}{\partial \mathrm {I} _{2}}}+\mathrm {I} _{1}{\frac {\partial f}{\partial \mathrm {I} _{3}}}\right)\mathbf {T} ^{\top }\\&+{\frac {\partial f}{\partial \mathrm {I} _{3}}}\mathbf {T} ^{\top }\cdot \mathbf {T} ^{\top }\end{aligned}}}

Ableitung der Frobenius-Norm:

∂ ∥ T ∥ ∂ T = T ∥ T ∥ {\displaystyle {\frac {\partial \parallel \mathbf {T} \parallel }{\partial \mathbf {T} }}={\frac {\mathbf {T} }{\parallel \mathbf {T} \parallel }}} {\displaystyle {\frac {\partial \parallel \mathbf {T} \parallel }{\partial \mathbf {T} }}={\frac {\mathbf {T} }{\parallel \mathbf {T} \parallel }}}

Eigenwerte (aus der impliziten Ableitung des charakteristischen Polynoms):

T ⋅ v → = λ v → → d e t ( T − λ 1 ) = − λ 3 + I 1 λ 2 − I 2 λ + I 3 = 0 {\displaystyle \mathbf {T} \cdot {\vec {v}}=\lambda {\vec {v}}\quad \rightarrow \quad \mathrm {det} (\mathbf {T} -\lambda \mathbf {1} )=-\lambda ^{3}+\mathrm {I} _{1}\lambda ^{2}-\mathrm {I} _{2}\lambda +\mathrm {I} _{3}=0} {\displaystyle \mathbf {T} \cdot {\vec {v}}=\lambda {\vec {v}}\quad \rightarrow \quad \mathrm {det} (\mathbf {T} -\lambda \mathbf {1} )=-\lambda ^{3}+\mathrm {I} _{1}\lambda ^{2}-\mathrm {I} _{2}\lambda +\mathrm {I} _{3}=0}
→ d λ d T = ( λ 2 − λ I 1 + I 2 ) 1 + ( λ − I 1 ) T ⊤ + T ⊤ ⋅ T ⊤ 3 λ 2 − 2 I 1 λ + I 2 {\displaystyle {\dfrac {\mathrm {d} \lambda }{\mathrm {d} \mathbf {T} }}={\dfrac {(\lambda ^{2}-\lambda \mathrm {I} _{1}+\mathrm {I} _{2})\mathbf {1} +(\lambda -\mathrm {I} _{1})\mathbf {T} ^{\top }+\mathbf {T^{\top }\cdot T^{\top }} }{3\lambda ^{2}-2\mathrm {I} _{1}\lambda +\mathrm {I} _{2}}}} {\displaystyle {\dfrac {\mathrm {d} \lambda }{\mathrm {d} \mathbf {T} }}={\dfrac {(\lambda ^{2}-\lambda \mathrm {I} _{1}+\mathrm {I} _{2})\mathbf {1} +(\lambda -\mathrm {I} _{1})\mathbf {T} ^{\top }+\mathbf {T^{\top }\cdot T^{\top }} }{3\lambda ^{2}-2\mathrm {I} _{1}\lambda +\mathrm {I} _{2}}}}

Eigenwerte symmetrischer Tensoren:

T ⋅ v → = λ v → → ∂ λ ∂ T = v → ⊗ v → {\displaystyle \mathbf {T} \cdot {\vec {v}}=\lambda {\vec {v}}\quad \rightarrow \quad {\frac {\partial \lambda }{\partial \mathbf {T} }}={\vec {v}}\otimes {\vec {v}}} {\displaystyle \mathbf {T} \cdot {\vec {v}}=\lambda {\vec {v}}\quad \rightarrow \quad {\frac {\partial \lambda }{\partial \mathbf {T} }}={\vec {v}}\otimes {\vec {v}}}

Eigenwerte von T = ∑ i = 1 3 λ i v → i ⊗ v → i {\displaystyle \mathbf {T} =\sum _{i=1}^{3}\lambda _{i}\,{\vec {v}}_{i}\otimes {\vec {v}}^{i}} {\displaystyle \mathbf {T} =\sum _{i=1}^{3}\lambda _{i}\,{\vec {v}}_{i}\otimes {\vec {v}}^{i}}, wo v → i {\displaystyle {\vec {v}}^{i}} {\displaystyle {\vec {v}}^{i}} dual zu den Eigenvektoren v → i {\displaystyle {\vec {v}}_{i}} {\displaystyle {\vec {v}}_{i}} sind ( v → i ⋅ v → j = δ i j ) {\displaystyle ({\vec {v}}_{i}\cdot {\vec {v}}^{j}=\delta _{i}^{j})} {\displaystyle ({\vec {v}}_{i}\cdot {\vec {v}}^{j}=\delta _{i}^{j})}:

∂ λ i ∂ T = v → i ⊗ v → i {\displaystyle {\frac {\partial \lambda _{i}}{\partial \mathbf {T} }}={\vec {v}}^{i}\otimes {\vec {v}}_{i}} {\displaystyle {\frac {\partial \lambda _{i}}{\partial \mathbf {T} }}={\vec {v}}^{i}\otimes {\vec {v}}_{i}} (keine Summe)

Die Eigenwerte von T = c v → 1 ⊗ v → 1 + a ( v → 2 ⊗ v → 2 + v → 3 ⊗ v → 3 ) + b ( v → 2 ⊗ v → 3 − v → 3 ⊗ v → 2 ) {\displaystyle \mathbf {T} =c\,{\vec {v}}_{1}\otimes {\vec {v}}^{1}+a({\vec {v}}_{2}\otimes {\vec {v}}^{2}+{\vec {v}}_{3}\otimes {\vec {v}}^{3})+b({\vec {v}}_{2}\otimes {\vec {v}}^{3}-{\vec {v}}_{3}\otimes {\vec {v}}^{2})} {\displaystyle \mathbf {T} =c\,{\vec {v}}_{1}\otimes {\vec {v}}^{1}+a({\vec {v}}_{2}\otimes {\vec {v}}^{2}+{\vec {v}}_{3}\otimes {\vec {v}}^{3})+b({\vec {v}}_{2}\otimes {\vec {v}}^{3}-{\vec {v}}_{3}\otimes {\vec {v}}^{2})} sind λ 1 = c , λ 2 = a + i b , λ 3 = a − i b {\displaystyle \lambda _{1}=c,\,\lambda _{2}=a+\mathrm {i} b,\,\lambda _{3}=a-\mathrm {i} b} {\displaystyle \lambda _{1}=c,\,\lambda _{2}=a+\mathrm {i} b,\,\lambda _{3}=a-\mathrm {i} b} mit den Eigenvektoren v → 1 , w → 2 = v → 2 + i v → 3 , w → 3 = v → 2 − i v → 3 {\displaystyle {\vec {v}}_{1},\,{\vec {w}}_{2}={\vec {v}}_{2}+\mathrm {i} {\vec {v}}_{3},\,{\vec {w}}_{3}={\vec {v}}_{2}-\mathrm {i} {\vec {v}}_{3}} {\displaystyle {\vec {v}}_{1},\,{\vec {w}}_{2}={\vec {v}}_{2}+\mathrm {i} {\vec {v}}_{3},\,{\vec {w}}_{3}={\vec {v}}_{2}-\mathrm {i} {\vec {v}}_{3}}. Hier ist:

∂ λ 1 ∂ T = v → 1 ⊗ v → 1 , ∂ λ k ∂ T = 1 2 w → k ⊗ w → k ¯ , k = 2 , 3 {\displaystyle {\frac {\partial \lambda _{1}}{\partial \mathbf {T} }}={\vec {v}}^{1}\otimes {\vec {v}}_{1},\quad {\frac {\partial \lambda _{k}}{\partial \mathbf {T} }}={\frac {1}{2}}{\overline {{\vec {w}}^{k}\otimes {\vec {w}}_{k}}},\quad k=2,3} {\displaystyle {\frac {\partial \lambda _{1}}{\partial \mathbf {T} }}={\vec {v}}^{1}\otimes {\vec {v}}_{1},\quad {\frac {\partial \lambda _{k}}{\partial \mathbf {T} }}={\frac {1}{2}}{\overline {{\vec {w}}^{k}\otimes {\vec {w}}_{k}}},\quad k=2,3} (keine Summe)

mit w → 2 = v → 2 + i v → 3 , w → 3 = v → 2 − i v → 3 {\displaystyle {\vec {w}}^{2}={\vec {v}}^{2}+\mathrm {i} {\vec {v}}^{3},\,{\vec {w}}^{3}={\vec {v}}^{2}-\mathrm {i} {\vec {v}}^{3}} {\displaystyle {\vec {w}}^{2}={\vec {v}}^{2}+\mathrm {i} {\vec {v}}^{3},\,{\vec {w}}^{3}={\vec {v}}^{2}-\mathrm {i} {\vec {v}}^{3}} und der Überstrich markiert den konjugiert komplexen Wert.

Konvektive Koordinaten

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Konvektive Koordinaten

Konvektive Koordinaten y 1 , y 2 , y 3 ∈ R {\displaystyle y_{1},y_{2},y_{3}\in \mathbb {R} } {\displaystyle y_{1},y_{2},y_{3}\in \mathbb {R} }

Kovariante Basisvektoren B → i = d X → d y i {\displaystyle {\vec {B}}_{i}={\frac {\mathrm {d} {\vec {X}}}{\mathrm {d} y_{i}}}} {\displaystyle {\vec {B}}_{i}={\frac {\mathrm {d} {\vec {X}}}{\mathrm {d} y_{i}}}},    b → i = d x → d y i {\displaystyle {\vec {b}}_{i}={\frac {\mathrm {d} {\vec {x}}}{\mathrm {d} y_{i}}}} {\displaystyle {\vec {b}}_{i}={\frac {\mathrm {d} {\vec {x}}}{\mathrm {d} y_{i}}}}

Kontravariante Basisvektoren B → i = d y i d X → := G R A D ( y i ) {\displaystyle {\vec {B}}^{i}={\frac {\mathrm {d} y_{i}}{\mathrm {d} {\vec {X}}}}:=\mathrm {GRAD} (y_{i})} {\displaystyle {\vec {B}}^{i}={\frac {\mathrm {d} y_{i}}{\mathrm {d} {\vec {X}}}}:=\mathrm {GRAD} (y_{i})},    b → i = d y i d x → := g r a d ( y i ) {\displaystyle {\vec {b}}^{i}={\frac {\mathrm {d} y_{i}}{\mathrm {d} {\vec {x}}}}:=\mathrm {grad} (y_{i})} {\displaystyle {\vec {b}}^{i}={\frac {\mathrm {d} y_{i}}{\mathrm {d} {\vec {x}}}}:=\mathrm {grad} (y_{i})}

B → i ⋅ B → j = b → i ⋅ b → j = δ i j {\displaystyle {\vec {B}}_{i}\cdot {\vec {B}}^{j}={\vec {b}}_{i}\cdot {\vec {b}}^{j}=\delta _{i}^{j}} {\displaystyle {\vec {B}}_{i}\cdot {\vec {B}}^{j}={\vec {b}}_{i}\cdot {\vec {b}}^{j}=\delta _{i}^{j}}

Deformationsgradient F = b → i ⊗ B → i {\displaystyle \mathbf {F} ={\vec {b}}_{i}\otimes {\vec {B}}^{i}} {\displaystyle \mathbf {F} ={\vec {b}}_{i}\otimes {\vec {B}}^{i}}

Räumlicher Geschwindigkeitsgradient l = b → ˙ i ⊗ b → i = − b → i ⊗ b → ˙ i {\displaystyle \mathbf {l} ={\dot {\vec {b}}}_{i}\otimes {\vec {b}}^{i}=-{\vec {b}}_{i}\otimes {\dot {\vec {b}}}^{i}} {\displaystyle \mathbf {l} ={\dot {\vec {b}}}_{i}\otimes {\vec {b}}^{i}=-{\vec {b}}_{i}\otimes {\dot {\vec {b}}}^{i}}

Kovarianter Tensor T = T i j b → i ⊗ b → j {\displaystyle \mathbf {T} =T_{ij}{\vec {b}}^{i}\otimes {\vec {b}}^{j}} {\displaystyle \mathbf {T} =T_{ij}{\vec {b}}^{i}\otimes {\vec {b}}^{j}}

Kontravarianter Tensor T = T i j b → i ⊗ b → j {\displaystyle \mathbf {T} =T^{ij}{\vec {b}}_{i}\otimes {\vec {b}}_{j}} {\displaystyle \mathbf {T} =T^{ij}{\vec {b}}_{i}\otimes {\vec {b}}_{j}}

Geschwindigkeitsgradient

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Geschwindigkeitsgradient

Räumlicher Geschwindigkeitsgradient: l = g r a d ( v → ) = F ˙ ⋅ F − 1 {\displaystyle \mathbf {l} =\mathrm {grad} ({\vec {v}})={\dot {\mathbf {F} }}\cdot \mathbf {F} ^{-1}} {\displaystyle \mathbf {l} =\mathrm {grad} ({\vec {v}})={\dot {\mathbf {F} }}\cdot \mathbf {F} ^{-1}}

Divergenz der Geschwindigkeit: d i v ( v → ) = S p ( l ) {\displaystyle \mathrm {div} ({\vec {v}})=\mathrm {Sp} (\mathbf {l} )} {\displaystyle \mathrm {div} ({\vec {v}})=\mathrm {Sp} (\mathbf {l} )}

Winkelgeschwindigkeit oder Wirbelstärke ist der duale axiale Vektor

ω → = l → A = − 1 2 i → ( l ) = 1 2 r o t ( v → ) {\displaystyle {\vec {\omega }}={\stackrel {A}{\vec {\mathbf {l} }}}=-{\frac {1}{2}}{\vec {\mathrm {i} }}(\mathbf {l} )={\frac {1}{2}}\mathrm {rot} ({\vec {v}})} {\displaystyle {\vec {\omega }}={\stackrel {A}{\vec {\mathbf {l} }}}=-{\frac {1}{2}}{\vec {\mathrm {i} }}(\mathbf {l} )={\frac {1}{2}}\mathrm {rot} ({\vec {v}})}
D D t d e t ( F ) = d e t ( F ) F ⊤ − 1 : F ˙ = d e t ( F ) S p ( F ˙ ⋅ F − 1 ) = d e t ( F ) d i v ( v → ) {\displaystyle {\frac {\mathrm {D} }{\mathrm {D} t}}\mathrm {det} (\mathbf {F} )=\mathrm {det} (\mathbf {F} )\mathbf {F} ^{\top -1}:{\dot {\mathbf {F} }}=\mathrm {det} (\mathbf {F} )\mathrm {Sp} ({\dot {\mathbf {F} }}\cdot \mathbf {F} ^{-1})=\mathrm {det} (\mathbf {F} )\,\mathrm {div} ({\vec {v}})} {\displaystyle {\frac {\mathrm {D} }{\mathrm {D} t}}\mathrm {det} (\mathbf {F} )=\mathrm {det} (\mathbf {F} )\mathbf {F} ^{\top -1}:{\dot {\mathbf {F} }}=\mathrm {det} (\mathbf {F} )\mathrm {Sp} ({\dot {\mathbf {F} }}\cdot \mathbf {F} ^{-1})=\mathrm {det} (\mathbf {F} )\,\mathrm {div} ({\vec {v}})}

Objektive Zeitableitungen

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Euklidische Transformation

Bezeichnungen wie in #Konvektive Koordinaten.

Räumlicher Geschwindigkeitsgradient l = b → ˙ i ⊗ b → i = − b → i ⊗ b → ˙ i = d + w {\displaystyle \mathbf {l} ={\dot {\vec {b}}}_{i}\otimes {\vec {b}}^{i}=-{\vec {b}}_{i}\otimes {\dot {\vec {b}}}\,^{i}=\mathbf {d} +\mathbf {w} } {\displaystyle \mathbf {l} ={\dot {\vec {b}}}_{i}\otimes {\vec {b}}^{i}=-{\vec {b}}_{i}\otimes {\dot {\vec {b}}}\,^{i}=\mathbf {d} +\mathbf {w} }

Räumliche Verzerrungsgeschwindigkeit d = 1 2 ( l + l ⊤ ) {\displaystyle \mathbf {d} ={\frac {1}{2}}(\mathbf {l} +\mathbf {l} ^{\top })} {\displaystyle \mathbf {d} ={\frac {1}{2}}(\mathbf {l} +\mathbf {l} ^{\top })}

Wirbel- oder Spintensor w = 1 2 ( l − l ⊤ ) {\displaystyle \mathbf {w} ={\frac {1}{2}}(\mathbf {l} -\mathbf {l} ^{\top })} {\displaystyle \mathbf {w} ={\frac {1}{2}}(\mathbf {l} -\mathbf {l} ^{\top })}

Objektive Zeitableitungen von Vektoren

[Bearbeiten | Quelltext bearbeiten]

Gegeben: v → = v i b → i = v i b → i {\displaystyle {\vec {v}}=v_{i}{\vec {b}}^{i}=v^{i}{\vec {b}}_{i}} {\displaystyle {\vec {v}}=v_{i}{\vec {b}}^{i}=v^{i}{\vec {b}}_{i}}:

v → Δ = v → ˙ + l ⊤ ⋅ v → = v ˙ i b → i v → ∇ = v → ˙ − l ⋅ v → = v ˙ i b → i v → ∘ = v → ˙ − w ⋅ v → {\displaystyle {\begin{array}{rclcl}{\stackrel {\Delta }{\vec {v}}}&=&{\dot {\vec {v}}}+\mathbf {l} ^{\top }\cdot {\vec {v}}&=&{\dot {v}}_{i}{\vec {b}}^{i}\\{\stackrel {\nabla }{\vec {v}}}&=&{\dot {\vec {v}}}-\mathbf {l} \cdot {\vec {v}}&=&{\dot {v}}^{i}{\vec {b}}_{i}\\{\stackrel {\circ }{\vec {v}}}&=&{\dot {\vec {v}}}-\mathbf {w} \cdot {\vec {v}}\end{array}}} {\displaystyle {\begin{array}{rclcl}{\stackrel {\Delta }{\vec {v}}}&=&{\dot {\vec {v}}}+\mathbf {l} ^{\top }\cdot {\vec {v}}&=&{\dot {v}}_{i}{\vec {b}}^{i}\\{\stackrel {\nabla }{\vec {v}}}&=&{\dot {\vec {v}}}-\mathbf {l} \cdot {\vec {v}}&=&{\dot {v}}^{i}{\vec {b}}_{i}\\{\stackrel {\circ }{\vec {v}}}&=&{\dot {\vec {v}}}-\mathbf {w} \cdot {\vec {v}}\end{array}}}

Objektive Zeitableitungen von Tensoren

[Bearbeiten | Quelltext bearbeiten]

Gegeben: T = T i j b → i ⊗ b → j = T i j b → i ⊗ b → j {\displaystyle \mathbf {T} =T_{ij}{\vec {b}}^{i}\otimes {\vec {b}}^{j}=T^{ij}{\vec {b}}_{i}\otimes {\vec {b}}_{j}} {\displaystyle \mathbf {T} =T_{ij}{\vec {b}}^{i}\otimes {\vec {b}}^{j}=T^{ij}{\vec {b}}_{i}\otimes {\vec {b}}_{j}}

T Δ = T ˙ + T ⋅ l + l ⊤ ⋅ T = T ˙ i j b → i ⊗ b → j T ∇ = T ˙ − l ⋅ T − T ⋅ l ⊤ = T ˙ i j b → i ⊗ b → j T ∘ = T ˙ + T ⋅ w − w ⋅ T T ⋄ = T ˙ + S p ( l ) T − l ⋅ T − T ⋅ l ⊤ {\displaystyle {\begin{array}{rclcl}{\stackrel {\Delta }{\mathbf {T} }}&=&{\dot {\mathbf {T} }}+\mathbf {T\cdot l} +\mathbf {l} ^{\top }\cdot \mathbf {T} &=&{\dot {T}}_{ij}{\vec {b}}^{i}\otimes {\vec {b}}^{j}\\{\stackrel {\nabla }{\mathbf {T} }}&=&{\dot {\mathbf {T} }}-\mathbf {l\cdot T} -\mathbf {T\cdot l} ^{\top }&=&{\dot {T}}^{ij}{\vec {b}}_{i}\otimes {\vec {b}}_{j}\\{\stackrel {\circ }{\mathbf {T} }}&=&{\dot {\mathbf {T} }}+\mathbf {T\cdot w} -\mathbf {w\cdot T} \\{\stackrel {\diamond }{\mathbf {T} }}&=&{\dot {\mathbf {T} }}+\mathrm {Sp} (\mathbf {l} )\mathbf {T} -\mathbf {l\cdot T} -\mathbf {T\cdot l} ^{\top }\end{array}}} {\displaystyle {\begin{array}{rclcl}{\stackrel {\Delta }{\mathbf {T} }}&=&{\dot {\mathbf {T} }}+\mathbf {T\cdot l} +\mathbf {l} ^{\top }\cdot \mathbf {T} &=&{\dot {T}}_{ij}{\vec {b}}^{i}\otimes {\vec {b}}^{j}\\{\stackrel {\nabla }{\mathbf {T} }}&=&{\dot {\mathbf {T} }}-\mathbf {l\cdot T} -\mathbf {T\cdot l} ^{\top }&=&{\dot {T}}^{ij}{\vec {b}}_{i}\otimes {\vec {b}}_{j}\\{\stackrel {\circ }{\mathbf {T} }}&=&{\dot {\mathbf {T} }}+\mathbf {T\cdot w} -\mathbf {w\cdot T} \\{\stackrel {\diamond }{\mathbf {T} }}&=&{\dot {\mathbf {T} }}+\mathrm {Sp} (\mathbf {l} )\mathbf {T} -\mathbf {l\cdot T} -\mathbf {T\cdot l} ^{\top }\end{array}}}

Materielle Zeitableitung

[Bearbeiten | Quelltext bearbeiten]
Siehe auch: Substantielle Ableitung
f ˙ ( x → , t ) = D f D t = ∂ f ∂ t + g r a d ( f ) ⋅ v → = ∂ f ∂ t + ( v → ⋅ ∇ ) f {\displaystyle {\dot {f}}({\vec {x}},t)={\frac {\mathrm {D} f}{\mathrm {D} t}}={\frac {\partial f}{\partial t}}+\mathrm {grad} (f)\cdot {\vec {v}}={\frac {\partial f}{\partial t}}+({\vec {v}}\cdot \nabla )f} {\displaystyle {\dot {f}}({\vec {x}},t)={\frac {\mathrm {D} f}{\mathrm {D} t}}={\frac {\partial f}{\partial t}}+\mathrm {grad} (f)\cdot {\vec {v}}={\frac {\partial f}{\partial t}}+({\vec {v}}\cdot \nabla )f}
f → ˙ ( x → , t ) = D f → D t = ∂ f → ∂ t + g r a d ( f → ) ⋅ v → = ∂ f → ∂ t + ( v → ⋅ ∇ ) f → {\displaystyle {\dot {\vec {f}}}({\vec {x}},t)={\frac {\mathrm {D} {\vec {f}}}{\mathrm {D} t}}={\frac {\partial {\vec {f}}}{\partial t}}+\mathrm {grad} ({\vec {f}})\cdot {\vec {v}}={\frac {\partial {\vec {f}}}{\partial t}}+({\vec {v}}\cdot \nabla ){\vec {f}}} {\displaystyle {\dot {\vec {f}}}({\vec {x}},t)={\frac {\mathrm {D} {\vec {f}}}{\mathrm {D} t}}={\frac {\partial {\vec {f}}}{\partial t}}+\mathrm {grad} ({\vec {f}})\cdot {\vec {v}}={\frac {\partial {\vec {f}}}{\partial t}}+({\vec {v}}\cdot \nabla ){\vec {f}}}

#Kartesische Koordinaten: D f D t := ∂ f ∂ t + v x ∂ f ∂ x + v y ∂ f ∂ y + v z ∂ f ∂ z {\displaystyle {\frac {\mathrm {D} f}{\mathrm {D} t}}:={\frac {\partial f}{\partial t}}+v_{x}{\frac {\partial f}{\partial x}}+v_{y}{\frac {\partial f}{\partial y}}+v_{z}{\frac {\partial f}{\partial z}}} {\displaystyle {\frac {\mathrm {D} f}{\mathrm {D} t}}:={\frac {\partial f}{\partial t}}+v_{x}{\frac {\partial f}{\partial x}}+v_{y}{\frac {\partial f}{\partial y}}+v_{z}{\frac {\partial f}{\partial z}}}

#Zylinderkoordinaten: D f D t := ∂ f ∂ t + v ρ ∂ f ∂ ρ + v φ ρ ∂ f ∂ φ + v z ∂ f ∂ z {\displaystyle {\frac {\mathrm {D} f}{\mathrm {D} t}}:={\frac {\partial f}{\partial t}}+v_{\rho }{\frac {\partial f}{\partial \rho }}+{\frac {v_{\varphi }}{\rho }}{\frac {\partial f}{\partial \varphi }}+v_{z}{\frac {\partial f}{\partial z}}} {\displaystyle {\frac {\mathrm {D} f}{\mathrm {D} t}}:={\frac {\partial f}{\partial t}}+v_{\rho }{\frac {\partial f}{\partial \rho }}+{\frac {v_{\varphi }}{\rho }}{\frac {\partial f}{\partial \varphi }}+v_{z}{\frac {\partial f}{\partial z}}}

#Kugelkoordinaten: D f D t := ∂ f ∂ t + v r ∂ f ∂ r + v φ r sin ⁡ ( ϑ ) ∂ f ∂ φ + v ϑ r ∂ f ∂ ϑ {\displaystyle {\frac {\mathrm {D} f}{\mathrm {D} t}}:={\frac {\partial f}{\partial t}}+v_{r}{\frac {\partial f}{\partial r}}+{\frac {v_{\varphi }}{r\sin(\vartheta )}}{\frac {\partial f}{\partial \varphi }}+{\frac {v_{\vartheta }}{r}}{\frac {\partial f}{\partial \vartheta }}} {\displaystyle {\frac {\mathrm {D} f}{\mathrm {D} t}}:={\frac {\partial f}{\partial t}}+v_{r}{\frac {\partial f}{\partial r}}+{\frac {v_{\varphi }}{r\sin(\vartheta )}}{\frac {\partial f}{\partial \varphi }}+{\frac {v_{\vartheta }}{r}}{\frac {\partial f}{\partial \vartheta }}}

Materielle Zeitableitungen von Vektoren werden mittels D f → D t = D f i D t e ^ i {\displaystyle {\tfrac {\mathrm {D} {\vec {f}}}{\mathrm {D} t}}={\tfrac {\mathrm {D} f_{i}}{\mathrm {D} t}}{\hat {e}}_{i}} {\displaystyle {\tfrac {\mathrm {D} {\vec {f}}}{\mathrm {D} t}}={\tfrac {\mathrm {D} f_{i}}{\mathrm {D} t}}{\hat {e}}_{i}} daraus zusammengesetzt.

Fußnoten

[Bearbeiten | Quelltext bearbeiten]
  1. ↑ a b c Morton E. Gurtin: „The linear theory of elasticity.“ In: S. Flügge (Hrsg.): Handbuch der Physik. Band VIa/2.: Festkörpermechanik II / C. Truesdell (Bandherausgeber). Springer, Berlin 1972, ISBN 3-540-05535-5, S. 10 ff.
  2. ↑ In der Literatur (z. B. Altenbach 2012) wird auch die transponierte Beziehung benutzt:
    grad ~ ( f → ) = ∇ ⊗ f → = e ^ i ⊗ ∂ f → ∂ x i = f j ∂ x i e ^ i ⊗ e ^ j = grad ⁡ ( f → ) ⊤ {\displaystyle {\tilde {\operatorname {grad} }}({\vec {f}})=\nabla \otimes {\vec {f}}={\hat {e}}_{i}\otimes {\frac {\partial {\vec {f}}}{\partial x_{i}}}=f_{j}{\partial x_{i}}{\hat {e}}_{i}\otimes {\hat {e}}_{j}=\operatorname {grad} ({\vec {f}})^{\top }} {\displaystyle {\tilde {\operatorname {grad} }}({\vec {f}})=\nabla \otimes {\vec {f}}={\hat {e}}_{i}\otimes {\frac {\partial {\vec {f}}}{\partial x_{i}}}=f_{j}{\partial x_{i}}{\hat {e}}_{i}\otimes {\hat {e}}_{j}=\operatorname {grad} ({\vec {f}})^{\top }}
    Dann muss, um die Formeln zu vergleichen, g r a d ~ ( f → ) {\displaystyle {\tilde {\mathrm {grad} }}({\vec {f}})} {\displaystyle {\tilde {\mathrm {grad} }}({\vec {f}})} und g r a d ( f → ) ⊤ {\displaystyle \mathrm {grad} ({\vec {f}})^{\top }} {\displaystyle \mathrm {grad} ({\vec {f}})^{\top }} vertauscht werden.
  3. ↑ Wolfgang Werner: Vektoren und Tensoren als universelle Sprache in Physik und Technik. Tensoralgebra und Tensoranalysis. Band 1. Springer Vieweg Verlag, Wiesbaden 2019, ISBN 978-3-658-25271-7, S. 367, doi:10.1007/978-3-658-25272-4. 
  4. ↑ R. Greve (2003), S. 111.

Literatur

[Bearbeiten | Quelltext bearbeiten]
  • H. Altenbach: Kontinuumsmechanik. Springer, 2012, ISBN 978-3-642-24118-5. 
  • M. Bestehorn: Hydrodynamik und Strukturbildung. Springer, 2006, ISBN 978-3-540-33796-6. 
  • Adolf J. Schwab: Begriffswelt der Feldtheorie. Praxisnahe, anschauliche Einführung. Elektromagnetische Felder, Maxwellsche Gleichungen, Gradient, Rotation, Divergenz. 6., unveränderte Auflage. Springer, Berlin u. a. 2002, ISBN 3-540-42018-5. 
  • Konrad Königsberger: Analysis. überarbeitete Auflage. Band 2. 4. Springer, Berlin u. a. 2000, ISBN 3-540-43580-8. 
  • Ralf Greve: Kontinuumsmechanik. Springer, 2003, ISBN 3-540-00760-1. 
  • C. Truesdell: Festkörpermechanik II. In: S. Flügge (Hrsg.): Handbuch der Physik. Band VIa/2. Springer, 1972, ISBN 3-540-05535-5. 
Abgerufen von „https://de.teknopedia.teknokrat.ac.id/w/index.php?title=Formelsammlung_Tensoranalysis&oldid=263137105“
Kategorien:
  • Kontinuumsmechanik
  • Vektoranalysis
  • Formelsammlung

  • indonesia
  • Polski
  • العربية
  • Deutsch
  • English
  • Español
  • Français
  • Italiano
  • مصرى
  • Nederlands
  • 日本語
  • Português
  • Sinugboanong Binisaya
  • Svenska
  • Українська
  • Tiếng Việt
  • Winaray
  • 中文
  • Русский
Sunting pranala
Pusat Layanan

UNIVERSITAS TEKNOKRAT INDONESIA | ASEAN's Best Private University
Jl. ZA. Pagar Alam No.9 -11, Labuhan Ratu, Kec. Kedaton, Kota Bandar Lampung, Lampung 35132
Phone: (0721) 702022
Email: pmb@teknokrat.ac.id