On Shock-shock Interaction In Double-wedge Flow With High Temperature Non-equilibrium Effects

Shock-shock interaction is a common phenomenon in flows around hypersonic ve-hicle.Such shock interactions may cause high localized pressure and heat load on the vehicle,and subsequently have significant impacts on the performance and reliability of hypersonic flight.The massive amount of kinetic energy is converted to internal en-ergy by the shock wave,which results in extremely high temperature behind the shock.The high temperature can cause significant excitation of vibrational energy,dissocia-tion of polyatomic molecules and ionization reaction,which may make the components and energy modes of the gas change with time.All these phenomena generating from high temperature is called high temperature effects.Obviously,the high temperature effects can not be avoided in shock-shock interaction with high Mach number.Studies on shock-shock interaction show that the high temperature effects have significant in-fluence on the feature of flow field,such as shape and position of the shock waves,scale of the boundary layer separation,etc.However,most of the studies are conducted with perfect gas model,and the high temperature effects are ignored.Obviously,the resluts are inaccurate and the high temperature should be considered for correction.In this study,we carry out a theoretical and numerical investigation on the transition between regular reflection and Mach reflection of Type V interaction as well as self-induced shock wave oscillation in double-wedge flow with high temperature effects,feature of the shock waves and the influence of high temperature effects are analyzed.Transition between regular reflection and Mach reflection of Type V shock in-teraction is investigated theoretically and numerically.Park's two-temperature model and the five species chemical kinetic model is adopted to characterize the flow field.The classical shock polar method is extended to the high temperature gas by introduc-ing a non-equilibrium relaxation distance.The shock polar analysis is performed to evaluate the critical angles for the transition under detachment criterion and von Neu-mann criterion.The wave patterns and the process of the transition are investigated through two-dimensional numerical simulation.The critical angles obtained by theo-retical analysis and numerical simulation show evident disagreement,indicating that transition mechanism between regular reflection and Mach reflection is changed.The transition obtained from numerical results shows that collisions between the triple points and interaction point lead to the transition between regular reflection and Mach reflec-tion.By comparing with the frozen counterpart,high temperature effects change the transition mechanism in smaller wedge angle cases,and lead to larger critical angles as well as hysteresis interval.Self-induced oscillation in double-wedge flow under frozen and non-equilibrium conditions are numerically investigated.The results show that refined mesh is neces-sary for catching the right oscillation model.With smaller wedge angle,location and shape of the wave patter oscillate periodically and wave pattern remains a Mach reflec-tion configuration.However,the wave patter transition between Mach reflection and regular reflection during the self-indeced oscillation period with larger wedge angle.The motion of the lower triple point occurs with a small delay relatively to that of the upper triple point,which may cause the self-induced oscillation of the shock.The vor-tex induced by the slip layer may be the inner reason for the oscillation.By comparing with frozen counterpart,high temperature effects have little influence on the model and period of the self-induced oscillation in cases with smaller wedge angle,while the high temperature effects make the self-induced oscillation more intensive and lead to a lager oscillation interval in cases with larger wedge angle.