Relaxation of Rayleigh and Lorentz gases in shock waves

Two-dimensional Fokker–Planck type kinetic equations were derived, and some calculation results are presented to illustrate the principal distinction of the process of translational relaxation in a flow behind the front of a shock wave from the one-dimensional description that is valid for a stationary gas. In contrast to a Lorentz gas (a small admixture of light particles in a thermostat of heavy particles), the process of translational relaxation in a Rayleigh gas (a small admixture of heavy particles in a thermostat of low-weight gas particles) has an obvious two-dimensional character.