Supercomputer simulation of monatomic rarefied gas flows using parallel code “Nesvetay”

The presentations makes an overview of the current capabilities of the Nesvetay code as applied to monatomic rarefied gas flows based on the numerical solution of the kinetic equation with BGK and E.M. Shakhov (S-model) collision integrals. The “Nesvetay” code uses the author’s version of the discrete velocity method, which includes a finite volume scheme for approximating the transfer operator on arbitrary spatial grids, a conservative method for calculating macroparameters on an unstructured velocity grid, an implicit scheme for stationary problems, and an explicit method on moving deforming grids for modeling nonstationary currents. To solve large problems, the code implements a two-level approach to organizing parallel computing, which allows using thousands of physical x86 cores in calculations. Examples of calculations are given for three classes of problems: 1) flows in microchannels, 2) external high-altitude aerodynamics, 3) simulation of the expansion of a gas cloud into the surrounding space due to evaporation from a solid surface. The results obtained are compared with the calculations of other authors using the method of direct statistical modeling (results of F. Sharipov et al., SMILE code from ITAM SB RAS and LasInEx code from A.A. Morozov from IT SB RAS) and based on the solution of the Boltzmann equation with the exact collision integral (Unified Flow Solver, Frolova A.A.).