pyro's low Mach hydrodynamics solver is designed for atmospheric flows. It captures the effects of stratification on a fluid element by enforcing a divergence constraint on the velocity field. The governing equations are:

\frac{\partial \rho}{\partial t} + \nabla \cdot (\rho U) &= 0 \\
\frac{\partial U}{\partial t} + U \cdot \nabla U + \frac{\beta_0}{\rho} \nabla \left ( \frac{p'}{\beta_0} \right ) &= \frac{\rho'}{\rho} g \\
\nabla \cdot (\beta_0 U) = 0

with \nabla p_0 = \rho_0 g and \beta_0 = p_0^{1/\gamma}.

As with the incompressible solver, we implement a cell-centered approximate projection method.

The main parameters that affect this solver are: