An all-speed projection and filtering method for gravity-stratified flows.

Gravity waves arise in gravitationally stratified compressible flows at low Mach and Froude numbers, and these waves impose a sharp restriction on the time step. This paper presents a filtering strategy for the fully compressible equations based on normal-mode analysis that is used throughout the simulation to compute the fast dynamics and is able to damp only chosen modes. This method is based on an asymptotic analysis and respects the dynamics of gravity waves for thin layers. Finally, the filtering method is tested on a series of examples.