Passage of a Shock Wave through the Region of Ionization Instability of Gas Discharge Plasma: Experimental and Numerical Study

The article refers to the field of supersonic flow control via external energy deposition. The objective of this work is to study the influence of ionization inhomogeneities organized in the area of a shock wave propagation on its shape, stability and intensity. Passing the strong shock wave (M=5-6) through the region of pre-formed ionization instability in gas discharge plasma has been studied experimentally and numerically. In the experiments the ionization spherical strata have been obtained arising in the gas discharge region due to the development of the ionization instability in air. As a result of the interaction of an initially plane shock wave with the inhomogeneous plasma region the formation of new complicated shock-wave configurations was obtained the shape of which changed from smooth to gear. These configurations were shown to acquire an unstable character. Numerical simulations were carried out on the basis of the Euler system of equations with the parameters corresponding to the experimental conditions with the use of the complex conservative difference schemes. The stratified energy source was modelled by a set of thermal layers with varying characteristics. Changes in the physic-chemical properties of the medium were described by varying the adiabatic index. Stratified shock-wave structures consisting of modified wavy shock-wave and contact discontinuities have been obtained as a result of the interaction of the shock wave with the region of ionization instability. Generation of the Richtmyer-Meshkov instabilities has been obtained on the thermal strata in the vicinity of the shock wave front curvatures which confirmed the unstable character of the shock wave front. Comparison of the obtained experimental and numerical shock front evolution showed a good agreement. Results of the study can be used to control of high-speed flows and shock-wave configurations, as well as mixing processes.