Study On Generation Flowfield And Evolution Characteristics Of Streamwise Vortices In Hypersonic Inlet

The tendency of integrated-designed hypersonic vehicles in the future puts forward higher requirements for the design of the inlet.The inlet configuration are more threedimensional characteristics.There is transverse compression in the three-dimensional inlet.For one aspect,the transverse compression increases the compression efficiency.On the other hand,its interaction with developed boundary layer will generate complex vortex structures in the inlet passage,which will deteriorate the performance of the inlet start,total pressure recovery,etc.Therefore,the study of streamwise vortices in hypersonic inlet has important theoretical value and broad engineering application prospect.In three-dimensional inlet,there exists large amount of low-energy flow.The flow has lateral pressure gradient,which will gather the low-energy flow in and roll it up.The vortices zone is formed.The formation and evolution of vortex flow field in hypersonic inlet is closely related to the configuration of flow field and the incoming flow conditions.The interaction between compression wave,shock wave and boundary layer exist in the flow field.The supersonic quiet wind tunnel experiment system was integrated to carry out wind tunnel experiments,and modern flow field observation technologies such as Nano-particle Planar Laser Scattering(NPLS)method and Particle Image Velocimetry(PIV)method were introduced into the flow field study of streamwise vortices.Based on the experimental study,the corresponding flow field is studied by numerical simulation.Firstly,the interaction between the compression wave and the boundary layer is studied.In this paper,the flow field images of the laminar boundary layer at different streamwise positions under the action of isentropic compression wave were obtained.The development and transition of the supersonic laminar boundary layer under the action of isentropic compression wave was observed.The flow field can be divided into three regions.The convergence line is the actual physical line where the boundary layer starts to separate.Turbulence of vortex shedding from the side wall and pressure gradient together lead to the boundary layer transition.The anti-separation capability of laminar boundary layer is weak.Under the action of transverse pressure gradient,the boundary layer flows away from the wall.The flow field images of the wave structure interacting with the single swept shock wave and the turbulent boundary layer are obtained.At the bottom of the boundary layer,the viscosity effect is strong,while the swept shock wave has a weak effect on the boundary layer.Secondly,the interaction between symmetric swept shock wave and boundary layer was studied experimentally.Under the condition of different side pressure angles and different boundary layer thickness of the incoming flow,the transverse flow field images of vortices at the same contraction ratio were obtained.The relationship between streamwise vortex area and shock wave intensity and boundary layer thickness is analyzed.The thicker the boundary layer is,the flatter the streamwise vortex is.When the boundary layer thickness is constant,the area of the streamwise vortex is linearly related to the shock wave intensity.Finally,by means of experiments and numerical simulation,the evolution characteristics of streamwise vortexes in open,semi-open and closed channels are studied.The evolution of streamwise vortex in open,semi-open and closed channels is compared.The height distribution of streamwise vortex at the outlet of inlet decreases gradually from center to both sides,and the decreasing amplitude increases gradually.The momentum loss area of flow decreases fastest in the contraction section.The flow field of streamwise vortex in open passage,semi-open passage and closed passage is similar,but there are still some differences.The wall retarding effect is the main reason for the evolution of streamwise vortex.