移動現象論
ρ ∂ v x ∂ t = μ ( ∂ 2 v x ∂ x 2 + ∂ 2 v x ∂ y 2 ) {\displaystyle \rho {\frac {\partial v_{x}}{\partial t}}=\mu \left({\frac {\partial ^{2}v_{x}}{\partial x^{2}}}+{\frac {\partial ^{2}v_{x}}{\partial y^{2}}}\right)}