Gas-monodisperse dust mixtures in smoothed particle hydrodynamics: Computing of stiff non-linear drag

Simulation the dynamics of gas-solid mixtures is crucial in many applications: chemical reactor design, evolution of circumstellar discs, etc. Such mixtures where gas is a carrier phase and solid grains are dispersed phase can be simulated as interpenetrating continuum media. The characteristic parameter of this problem is relaxation time between gas and dust velocities. In many applications this parameter varies significantly during the simulation (from small to unity). Moreover, the drag force can be non-linearly dependent on solids to gas relative velocity. These factors place high requirements on the numerical methods for such problems. We propose a novel non-iterative algorithm for Smoothed Particle Hydrodynamics for computing gas-solid mixtures with exchange momentum between phases. Forces (except drag force) are approximated explicitly, while drag force is linearized and velocity relaxation time is approximated explicitly while relative velocity is approximated implicitly. The algorithm was tested on dynamical problems for dusty gas mixtures. It was shown that in the developed algorithm for stiff nonlinear drag we can use temporal and spatial resolution independent of drag parameters.