The incompressible Navier-Stokes equations are ρ D u D t = − ∇ p + μ ∇ 2 u , {\displaystyle \rho {\frac {D\mathbf {u} }{Dt}}=-\nabla p+\mu \nabla ^{2}\mathbf {u} \,,} ∇ ⋅ u = 0 , {\displaystyle \nabla \cdot \mathbf {u} =0\;,} something for density... put in the equations for the Boussinesq approximation.
