Euler equations

${\frac {\partial \rho }{\partial t}}+\nabla \cdot \left(\rho \mathbf {u} \right)=0\,,$
${\frac {\partial (\rho u)}{\partial t}}+{\frac {\partial }{\partial x}}\left(\rho u^{2}+p\right)+{\frac {\partial }{\partial y}}\left(\rho uv\right)=0\,,$