Experimental Study On Three-dimensional Boundary Layer Transition Of HyTRV

With the continuous upgrading of the concept of new hypersonic vehicle,the transition of three-dimensional boundary layer under complex shape conditions has always been a research hotspot,which has important guiding value for aerodynamic design optimization and thermal protection engineering of vehicle.Based on the transition research model HyTRV(Hypersonic Transition Research Vehicle)with real aircraft characteristics,this paper uses temperature sensitive paints(TSP)technology,nano tracer planar laser scattering(NPLS)technology and fluctuating pressure measurement technology,through which the flow field characteristics and boundary layer transition of HyTRV under hypersonic conditions are systematically experimentally studied.Based on the flow characteristics of the lower surface,the sub regional studies are carried out,mainly including the types and change laws of unstable modes in different regions of the lower surface,and the effects of angle of attack and incoming Reynolds number on boundary layer transition;Based on the parametric control of angle of attack and incoming Reynolds number,the mechanism and variation law of leeward boundary layer transition at different angles of attack and the effect of incoming Reynolds number on boundary layer transition are studied.The main conclusions are as follows:According to the flow characteristics,the windward surface of the model can be divided into the area controlled by crossflow instability(the area between the leading edge line and the center line)and the area controlled by streamwise vortex instability(the area near the center line).In the crossflow region,the dominant boundary layer transition is the traveling wave,and the transition front is a symmetrically distributed wedge;In the range of small angle of attack,the transition is delayed with the increase of angle of attack and advanced with the increase of Reynolds number.In the region near the centerline,the streamwise vortex structure is mushroom shaped,whose spanwise width changes little along the streamwise direction and height increases,which tends to flatten with the increase of angle of attack;The transition at the centerline is caused by the instability of the streamwise vortex structure.With the increase of the angle of attack,it shows the law of advance first and then delay.This is due to the different transition mechanism of the boundary layer at different angles of attack.With the increase of Reynolds number,the transition is advanced.Under the action of circumferential pressure gradient,different crossflow regions and streamwise vortex regions will be formed on the leeward surface of the model.The impact of the angle of attack on the leeward transition is very significant.With the increase of the angle of attack,the pressure gradient on the model surface will change,resulting in the change of the position of the crossflow region and the streamwise vortex structure.The boundary layer transition in the crossflow region is dominated by the cross flow traveling wave,but the characteristic frequency of the crossflow traveling wave is different in different regions.The Reynolds number also has an influence on the boundary layer transition on the leeward side.With the increase of Reynolds number,the region controlled by the traveling wave in the crossflow region will increase,and the characteristic frequency and amplitude will increase,resulting in the advance of the boundary layer transition.In addition,the Reynolds number will also affect the location and range of the convective vortex structure.