The Study Of The Shock Wave/Boundary Layer Interactions In Hypersonic Inlet

The shock wave / boundary layer interaction,which is ubiquitous in the hypersonic inlet,is an important factor affecting the starting performance of the inlet.Generally,the shock induced boundary layer separation in the inlet can be divided into two type.One is the typical triangular separation,and the other is the interaction between the forebody shock and the cowl boundary layer.In this paper,with the background of inlet unstart,theoretical analysis,wind tunnel tests and numerical simulations were carried out.First,the mechanism of the interaction between the shock and the developed/developing boundary layer is discussed.Considering the viscous effect,the structure of the separation field is analyzed and classified.Type I: the leading edge shock and the incident shock interact with each other,the separation point is located on the weak viscous interaction zone;Type II: the leading edge shock and the separation shock interact with each other,and the separation point is located on the weak viscous interaction zone;Type III: Mach stem appears when the incident shock interacts with separation shock;Type IV:Detached shock occurs before the leading edge point of the flat plate.Based on the characteristics of the interaction field,a simplified analysis model describing the interactions between shock and developed / developing boundary layer is established.Assuming that the mean flow direction behind the Mach stem is half of the sum of the angles of the two slipstream,an analysis model describing the overall Mach reflection is proposed.Secondly,a series of experiments were conduced in the wind tunnel to study the transition from laminar flow field to type IV.The influence of the location of incident shock/ expansion waves,the intensity of incident shock were analyzed.NPLS technique was applied to obtain the fine structure of the interaction between the shock and the developed/developing boundary layer.High-frequency pressure devices were used to study the oscillation characteristics of the separation bubble.By changing the position of the incident shock and Mach number,it is confirmed that there is a hysterasis in the mutual transition between Type II and Type III.Again,A study was conduced on the characteristics of the separation field under double incident shock conditions.Through LES,the fusion and separation phenomena of separation bubbles under double incident shocks condition are studied.The instantaneous flow field structure of these two types of flow fields is obtained,and the internal physical mechanism behind separated and fusion is analyzed.The effects of the second incident shock intensity and the position of the second incident shock were studied.Finally,a hypersonic inlet was selected,to investigate the hypersonic inlet unstart under over rated mode.By changing the angle of attack of the flight,the hysteresis phenomenon of the inlet unstart were obtained.Based on the characteristics of the fusion separation bubble,two measures for improving the inlet starting performance are proposed.