They correspond to the Navier - Stokes equations with zero viscosity and heat conduction terms , although they are usually written in the form shown below to emphasize that they directly represent conservation of mass , momentum , and energy .
They correspond to the Navier - Stokes equations with zero viscosity and heat conduction terms . 
 They are usually written in the conservation form shown below to emphasize that they directly represent conservation of mass , momentum , and energy .