渦量方程 (英語:vorticity equation )是流體力學 中描述流體 質點渦量 變化的方程。可壓縮牛頓流體 的渦量方程表達式為:
D
ω
D
t
=
∂
ω
∂
t
+
(
u
⋅
∇
)
ω
=
(
ω
⋅
∇
)
u
−
ω
(
∇
⋅
u
)
+
1
ρ
2
∇
ρ
×
∇
p
+
∇
×
(
∇
⋅
τ
ρ
)
+
∇
×
(
B
ρ
)
{\displaystyle {\begin{aligned}{\frac {D{\boldsymbol {\omega }}}{Dt}}&={\frac {\partial {\boldsymbol {\omega }}}{\partial t}}+(\mathbf {u} \cdot \nabla ){\boldsymbol {\omega }}\\&=({\boldsymbol {\omega }}\cdot \nabla )\mathbf {u} -{\boldsymbol {\omega }}(\nabla \cdot \mathbf {u} )+{\frac {1}{\rho ^{2}}}\nabla \rho \times \nabla p+\nabla \times \left({\frac {\nabla \cdot \tau }{\rho }}\right)+\nabla \times \left({\frac {B}{\rho }}\right)\end{aligned}}}
其中D / Dt 表示物質導數 ,u 為流速 ,ρ 為流體密度 ,p 為壓強 ,τ 為粘性應力張量 ,B 為流體所受外力。方程右邊第一項表示渦旋伸展 。使用愛因斯坦求和約定 指標記號,上式又可寫作
d
ω
i
d
t
=
∂
ω
i
∂
t
+
v
j
∂
ω
i
∂
x
j
=
ω
j
∂
v
i
∂
x
j
−
ω
i
∂
v
j
∂
x
j
+
e
i
j
k
1
ρ
2
∂
ρ
∂
x
j
∂
p
∂
x
k
+
e
i
j
k
∂
∂
x
j
(
1
ρ
∂
τ
k
m
∂
x
m
)
+
e
i
j
k
∂
B
k
∂
x
j
{\displaystyle {\begin{aligned}{\frac {d\omega _{i}}{dt}}&={\frac {\partial \omega _{i}}{\partial t}}+v_{j}{\frac {\partial \omega _{i}}{\partial x_{j}}}\\&=\omega _{j}{\frac {\partial v_{i}}{\partial x_{j}}}-\omega _{i}{\frac {\partial v_{j}}{\partial x_{j}}}+e_{ijk}{\frac {1}{\rho ^{2}}}{\frac {\partial \rho }{\partial x_{j}}}{\frac {\partial p}{\partial x_{k}}}+e_{ijk}{\frac {\partial }{\partial x_{j}}}\left({\frac {1}{\rho }}{\frac {\partial \tau _{km}}{\partial x_{m}}}\right)+e_{ijk}{\frac {\partial B_{k}}{\partial x_{j}}}\end{aligned}}}
對於保守外力 作用下的不可壓縮流體 ,渦量方程可以簡化為
D
ω
D
t
=
(
ω
⋅
∇
)
u
+
ν
∇
2
ω
{\displaystyle {\frac {D{\boldsymbol {\omega }}}{Dt}}=\left({\boldsymbol {\omega }}\cdot \nabla \right)\mathbf {u} +\nu \nabla ^{2}{\boldsymbol {\omega }}}
其中ν 為運動黏度 ,∇2 為拉普拉斯算符 。
Manna, Utpal; Sritharan, S. S. Lyapunov Functionals and Local Dissipativity for the Vorticity Equation in LTemplate:Isup and Besov spaces. Differential and Integral Equations. 2007, 20 (5): 581–598.
Barbu, V.; Sritharan, S. S. M -Accretive Quantization of the Vorticity Equation (PDF) . Balakrishnan, A. V. (編). Semi-Groups of Operators: Theory and Applications. Boston: Birkhauser. 2000: 296–303 [2016-12-10 ] . (原始內容存檔 (PDF) 於2016-03-03).
Krigel, A. M. Vortex evolution. Geophysical, Astrophysical Fluid Dynamics. 1983, 24 : 213–223.