Abstract | In the first part, I consider the Navier-Stokes system written in the rotational frame describing the motion of a compressible viscous fluid under strong strati cation. The asymptotic limit for low Mach and Rossby numbers and large Reynolds number is studied on condition that the Froude number characterizing the degree of strati cation is proportional to the Mach number. In the second part, I consider a system arising from modeling of mixture of two fluids. This system can be written as a compressible Navier-Stokes equation with singular pressure. We show the global existence of weak solution, and study the limit behavior as the true densities of the two fluids become close. |