Regimes of subsonic compressible flow in gas-particle systems

We present regime maps for subsonic flow in dense gas-particle systems, which demarcate regions of compressible and (effectively) incompressible flow. These maps should aid researchers and industrialists in selecting the appropriate modeling approach, as well as in verifying numerical solvers. Demonstrating compressibility at Mach numbers lower than 0.3, we show that this commonly used criterion is insufficient for flows in porous media. For M < 0.1, systems dominated by heat exchange experience compressible effects at a fixed value of a dimensionless system parameter, while critical parameters in an adiabatic system can be assessed using a simple relation of the Mach number. Ultimately, we present a model based on computational fluid dynamics and discrete element method (CFD-DEM) allowing efficient calculation of subsonic compressible gas-particle flows.