The occurrence of oscillations in the numerical solution of unsteady rarefied gas flow problems with discontinuous boundary conditions using the discrete velocity method is a problem known in the literature as the “ray effect”. This effect is a significant obstacle in the numerical integration of kinetic equations under strong non-equilibrium conditions with low collision frequency. The application of global adaptation in velocity space allows in many cases to reduce oscillations in macroparameters. The results of using this algorithm are demonstrated by solving a two-dimensional evaporation problem during laser-matter interaction.
A.A. Frolova (Wed,) studied this question.