Numerical modeling of shock waves in a non-equilibrium reactive gas

The nonlinear dynamics of unstable sound waves in a nonequil- ibrium vibrationally excited gas is considered, taking into account viscosity, thermal conductivity, chemical reactions and arbitrary dependences of the relaxat- ion time, heating and cooling functions on density and temperature. A numerical model has been constructed and a software package has been developed, based on the gas-dynamic methods of end-to-end calculation CSPH-TVD/MUSCL, to study the linear and nonlinear stages of the development of acoustic instability in a nonequilibrium chemically active gas with different models of relaxation, heating and cooling times. The numerical model has high spatial resolution and second order accuracy. The influence of chemical activity in a nonequilibrium vibrationally excited gas on the nonlinear dynamics of acoustic instability has been studied. It is shown that taking into account chemical reactions in a nonequilibrium gas leads to an increase in acoustic instability and, as a result, at the final nonlinear stage, shock wave pulses of higher intensity and with a larger spatial scale are formed. The structure and stability of shock waves (SW) of various intensities have been studied. It is shown that shock waves in a nonequilibrium vibrationally excited gas turn out to be unstable, i.e. SW the shock front, unstable disturbances are generated, the amplitude of which increases over time, reaching nonlinear saturation.