Complex Shock Wave Interaction In Supersonic Flow

There are often complex shock wave interaction structures,especially oblique shock trains,exist in the flow fields of an isolator in hypersonic vehicle and wind tunnel.In the region of such structure,the aerodynamic parameters change dramatically and shock trains show obvious unsteady characteristics.The pressure fluctuation caused by the interactions of shock/shock or shock/boundary layer will have a great influence on the fatigue life and aerodynamic performance of the corresponding components.Therefore,it is significant to carry out targeted analysis of complex flow configurations.In this study,experimental and numerical simulation methods were used to study the three kinds of supersonic flow fields,in which the Mach number is about 2.7.Firstly,high-speed schlieren,background oriented schlieren(BOS)and transient pressure measurement have been used to describe the upstream flow field with incident shock wave.Qualitative and quantitative results of flow field parameters,and the three-dimensional information of the width of Mach stem were all obtained by combined results of different technologies.Then,an analysis model of shock reflection based on the minimum entropy production principle was established for the flow field with shock train,which under the perturbation of downstream pressure.The predicted results of this theory were in good agreement with the data of experiment,numerical simulation and literature.There should be a positive correlation between the frequency of the forced oblique shock train oscillation and downstream pressure,and a phenomenon named "hysteresis" existed during shock train moving.Finally,"hysteresis" still occurred in the flow field with incident oblique shock wave.Regular oscillations of shock train appeared near the upstream incident shock wave,while low-frequency oscillation became much more random in other cases.So,the structure of shock wave can be predicted according to the frequency characteristics.In addition,quantitative distribution information of density gradient in the unsteady flow field were also gained by BOS.