Shock Interactions And Aerodynamic Loads In The Upstream/Downstream Flow Of V-Shaped Blunt Leading Edges At High Mach Numbers

The hypersonic three-dimensional inward-turning inlet is a highly promising air capture system due to its high compression efficiency and excellent off-design performance.As the key part of inward-turning inlet,the V-shaped cowl lip embodies the prominent features of strong three-dimensional interaction and the coupling between upstream and downstream flow.These features cause a complex aerodynamic environment of high pressure/heating loads.However,it is difficult to reveal the flow mechanisms and pressure/heating characteristics of the V-shaped cowl lip based on existing knowledge.In the present work,the V-shaped blunt leading edge(VBLE)is employed to focus on shock interactions and heating/pressure loads in the upstream/downstream flows of V-shaped cowl lip.Comprehensive investigations are performed using a combination of numerical simulations,wind tunnel experiments,and theoretical analyses.The effects of model scale and freestream conditions on the flow structures and aerodynamic loads of VBLE are analyzed at freestream Mach number of 6～12.With the model scale increasing under the same freestream Mach number,the dimensionless pressure is almost unchanged while the dimensionless heating loads decrease significantly.Thus,the canonical pressure-heating correlations are not suitable for VBLE with different model scales.The heating correlations on the stagnation line of swept leading edge are derived in terms of freestream Mach number and Reynolds number.It is confirmed that the combination parameters of Mach number and Reynolds number are crucial parameters governing the heating loads on the stagnation line.The VBLE local heating peak caused by transmitted shock impingement,is correlated with model scale,freestream Mach number,and Reynolds number.These correlations achieve good agreement with the experimental data across freestream Mach number of 6～12,which provides valuable guidelines for aerothermal protection.Complex pressure loads are usually encountered in the downstream of VBLE.To reveal the flow mechanisms of these pressure loads,a V-shaped plate with a blunt leading edge(VBLEP)is proposed.The effect of radius ratio(i.e.,the crotch rounding radius to the leading-edge radius)and freestream Mach number are investigated to focus on the surface pressure characteristics with the help of numerical simulations and the pressure-sensitive paint experiments.The three-dimensional shock structures generated by VBLE change with the increase of radius ratio,which cause the downstream plate surface pressure distributions to evolve into the bifurcated,striped,and central highpressure zones.It is demonstrated that the flow separation,the sweep of shock wave,and the supersonic jet collision are responsible for these three high-pressure zones,respectively.The mechanisms for the transitions of pressure distribution types are clarified,inducing the variation of detached shock structures,disappearance of separation,and decrease of transmitted shock intensity.The transition criteria of pressure distribution types are established based on the analyses of the relative geometric positions,which can be used to predict the pressure distribution types of VBLEP with different radius ratios over a wide range of Mach numbers.The evolutions of maximum pressure on VBLEP with radius ratio and freestream Mach number are clarified,providing valuable guidelines for engineering applications.The oblique shock incidence on VBLE is employed to focus on shock interactions between the forebody shock and V-shaped cowl lip.The evolutions of shock structures between the oblique shock and the detached shock caused by swept leading edge are investigated.The transition from regular reflection to Mach reflection is identified along the intersection line of the two shocks.The local two-dimensional analysis and the method based on hypersonic equivalence principle are used to theoretically analyze the transition mechanisms.It is demonstrated that the decrease of the equivalent Mach number and the increase of the equivalent shock angle are responsible for the transition.Furthermore,the transition positions are obtained with changes in flow deflection angle of oblique shock and sweep angle of leading edge.Due to the influence of low Mach number flow behind oblique shock,the transitions of shock interactions on the crotch of VBLE are delayed.