Unsteady Characteristics And Modulations Of Shock Interactions On V-shaped Blunt Leading Edges

The hypersonic inward-turning inlet is one of the most attractive internal compression systems due to its outstanding performance.As a key part of the capture profile of the inward-turning inlet,the V-shaped cowl lip suffers from multiple shock interactions which is commonly accompanied with strongly unsteady characteristics and causes severe and complex aerodynamic loads on the wall.In this thesis,wind tunnel experiments,numerical simulations,and theoretical analyses are applied to investigate the unsteady characteristics of the flow field and explore the protection method of aerodynamic loads on the V-shaped blunt leading edges.The unsteady characteristics of the flow field and the aerodynamic loads are analyzed for a V-shaped blunt leading edge with regular reflection,which are conducted at freestream Mach number of 4 for both sideslip and non-sideslip cases.The results show that large-scale flow separations with strong unsteadiness are exhibited at the crotch of the V-shaped blunt leading edge.Based on the analyses of high-speed schlieren images,the "anti-phase oscillation" mode and "in-phase oscillation" mode of the separation shocks are identified for the non-sideslip case.The coupled oscillation modes of the separation shocks on both sides are destroyed for the sideslip case,and the oscillation energy of the leeward shock accounts for a higher proportion.The center frequencies of the separation shocks collapse to the same value after being nondimensionalized by the separation length and the flow velocity behind the detached shock for both sideslip and non-sideslip cases.The root mean square distributions of wall pulsating pressure along the crotch present double peak features with a low value at the stagnation point and high values at the sides.The wall pulsating pressure distributions shift to the windward side for the sideslip case.The flow structures and wall pulsating pressure in the stagnation region at the crotch are quite sensitive to the sideslip angle.Compared with the nonsideslip case,the peak value of pulsating pressure on the windward side approximately doubles,and the pulsating energy is concentrated at a narrower band of frequencies.Two reduction methods for the heating loads on the V-shaped blunt leading edges are proposed by modulating shock interactions.A blunt leading edge with an elliptical cross-section is proposed to change the shock interactions into the regular reflection from the same family with the centerline shape of the crotch unchanged.Significant reduction in heat flux at the centerline of the crotch is achieved with a slight increase in heat flux at the stagnation line of swept leading edge.A criterion for the regular reflection from the same family is established for the blunt leading edge with an elliptical cross-section,by introducing an equivalent radius ratio to the blunt leading edge with the circular cross-section,which is based on the similarity of the shock structures on the V-shaped blunt leading edges.An inverse design method for the V-shaped blunt leading edge with a smooth shock wave is proposed in which the centerline shape of the crotch is unrestricted.The constraints are given to satisfy the shock wave construction.The V-shaped blunt leading edge configuration is obtained by solving the inverse problem of shock waves in the symmetric plane.Compared with traditional configurations,the peak heat flux significantly reduces and the heat flux is almost uniformly distributed along the centerline of the inverse-designed configuration.