Monodisperse gas-solid mixtures with intense interphase interaction in two-fluid smoothed particle hydrodynamics

Simulations of gas-solid mixtures are used in many scientific and industrial applications. Two-Fluid Smoothed Particle Hydrodynamics (TFSPH) is an approach when gas and solids are simulated with different sets of particles interacting via drag force. Several methods are developed for computing drag force between gas and solid grains for TFSPH. Computationally challenging are simulations of gas-dust mixtures with intense in- tephase interaction, when velocity relaxation time tstop is much smaller than dynamical time of the problem. In explicit schemes the time step τ must be less than tstop, that leads to high computational costs. Moreover, it is known that for stiff problems both grid-based and particle methods may require unaffordably detailed resolution to capture the asymptotical bahaiviour of the solution. To address this problem we developed fast and robust method for computing stiff and mild drag force in gas solid-mixtures based on the ideas of Particle-in-Cell approach. In the paper we compare the results of new and previously developed methods on test problems

Numerical modeling of gravitational instability outcomes in multiphase circumstellar discs

To suggest consistent route toward planetesimal and planetary core formation in circumstellar discs we study gravitational instability outcomes in massive multiphase (gas-collisionless bodies) disc. Such unstable massive disc can be formed together with protostar in molecular cloud collapse with increased ratio of solids to gas density. In our calculations we found regimes when low-massive solid bodies subdisc drastically affect global structure formation in the disc, whose mass is constituted mainly by the gas. We demonstrated also that solitary areas of high gas density can concentrate solids, producing multiphase clumps, which can be considered as a cradle of large bodies formation

Numerical modeling of gravitational instability outcomes in multiphase circumstellar discs

To suggest consistent route toward planetesimal and planetary core formation in circumstellar discs we study gravitational instability outcomes in massive multiphase (gas-collisionless bodies) disc. Such unstable massive disc can be formed together with protostar in molecular cloud collapse with increased ratio of solids to gas density. In our calculations we found regimes when low-massive solid bodies subdisc drastically affect global structure formation in the disc, whose mass is constituted mainly by the gas. We demonstrated also that solitary areas of high gas density can concentrate solids, producing multiphase clumps, which can be considered as a cradle of large bodies formation

When and why formation of large bodies in circumstellar discs could take place?

We outlined the scenario of the planetary system formation, where large bodies are formed on the stage of massive discs. On this stage the whole of factors: chemical composition, chemical catalytic reactions, the disc self- gravitation, the increased ratio of solids to gas surface density, adiabatic gas cooling provides favorable conditions for gravitational instabilities development. Gravitational instabilities in multiphase medium can lead to planetesimal and planetary embryo formation