Investigations On Shock Reflections And Interactions With Thermo-chemical Non-equilibrium Effects

In hypersonic flight,the flow can reach a very high temperature with the stagnation of shock layer and boundary layer.With the high temperature,the gas internal energy like vibrational energy or electronic energy may be excited,molecule may dissociates into atoms.The gas thermochemical properties are deviated from these of calorically perfect gas.With the high altitude,the thermochemical process induced by the high temperature needs a long relaxation time to reach the equilibrium state.The hypersonic flow around the vehicle may be in non-equilibrium state,the flow parameters like gas components,temperature and pressure will change slowly in the field.The high tem-perature gas effects play an important role in the shock location,wall pressure and heat flux,separation zone size and other flow characteristic.At present,the high tempera-ture gas effects in some simple flow have been well known,but in the complicated flow,like shock reflection,shock-boundary layer interaction,the influences and mechanism of high temperature gas effects are still unclear.In this paper,the moving shock reflec-tion and shock-boundary layer interaction are investigated,and the emphasis is placed on the high temperature gas effects on the shape of Mach stem and the evolution of flow field.Firstly,the control equations of fluid mechanics including the vibrational and chem-ical source items are introduced.The thermodynamic relationships,gas transport prop-erties,chemical reaction coefficient and turbulent models are shown.Then the numer-ical methods like equation discretion,interface flux,boundary treatment are shown,With the numerical program,the hypersonic flow around sphere-cone,cylinder and compressional corner are simulated.In these flow,the shock location,wall pressure and heat flux,separation zone size are verified.The numerical result has a good agree-ment with the experimental data.The difference between two classical chemical models is shown in the simulation of sphere-cone flow.The mesh limitation for accurately pre-dicted the boundary layer is also discussed.With the inviscid simulation,two typical flow patterns with convex Mach stem in pseudo-steady shock reflection are discussed.The evolution of these two flow is realized by the change of incident shock Mach number.High temperature gas effects always promotes the deformation of Mach stem.In the non-equilibrium flow,the scales effects have an important influence on the deformation and height of Mach stem.With the self-similar assumption in pseudo-steady shock reflection,the control volume is applied to estimate the disturbance behind the Mach stem.The theoretical deformation in this model agrees with numerical result very well.The model also compares with the previous model,the current model is suitable for lager wide range of wedge angle.Based on the theoretical model,the mechanism of high temperature gas effects on the Mach stem deformation are found to be the heat absorption behind shock.In the shape transition of Mach stem,the curved reflected shock is regarded as the main reason.The boundary layer effects on the deformation of Mach stem is investigated numer-ically and experimentally.SF6 is used to generate the strong shock.With the boundary layer,the wall-jet rolls up more earlier,and this effects enhances with increase of wedge angle.The Reynolds number effects,i.e.the scale effects,are discussed by numerical simulations.With the increase of scale effects,the wall=jet behaves different form.The mechanism is the competitive relationship between the wall viscous forces and the jet inertia force.The incident shock may not be very straight.The Mach stem deformation in curved shock reflection is investigated by the blast wave reflection.In the flow evolution of blast wave reflection,the deformation of Mach stem is always very remarkable,nor in frozen flow,or in non-equilibrium flow.However,in blast wave reflection,the high temperature gas effects prevent the deformation of Mach stem.The phenomena is tried to be explained by the above theoretical model,but it fails.With the severe convex deformation,the triple point trajectory is theoretically predicted,it has a good agreement with the numerical result.The shock-boundary layer interaction is simulated with two classical geometry,double wedge and hypersonic inlet.In the double wedge,the influences of flow slight deflection,leading edge bluntness and the laminar or turbulent boundary layer on the wave patterns and wall heat flux are discussed.The boundary layer transition near the compressional corner are supposed to be the main reason which results the difference between numeric and experimental data.The hypersonic symmetry inlet with inflow Mach 9 is simulated.The high temperature gas effects are found to be negligible in the normal working condition.But in high blocking condition,the high temperature gas effects will reduce the surge frequency and improve the inlet trigger abilities.