Design concept of compression wave and opposite cowl shock configuration for hypersonic inlet with inward deflecting cowl

The horizontal external surface of inlet cowl can effectively reduce external drag on the hypersonic inlet. However, this configuration simultaneously requires an inward turning of cowl's inner contour, resulting in significant intensification of the cowl shock. To mitigate the high total-pressure loss caused by cowl shock and alleviate strong shock wave/boundary layer interactions, this study proposes a configuration design concept of compression waves/opposite cowl shock interaction, building upon prior research [Tang et al., “On the centered-compression waves/cowl shock interaction from opposite-family in hypersonic inlet with inward deflection cowl: An inviscid perspective,” Phys. Fluids 37, 076153 (2025)]. Specifically, a scaling factor (r) is introduced to proportionally adjust the third-stage isentropic compression surface, thereby establishing opposite-family interaction between the compression waves and the cowl shock. To validate this wave configuration methodology for hypersonic inlets, six inward-deflecting-cowl hypersonic inlets featuring geometrically distinct third-stage compression surfaces were designed through controlled variations of both compression method and scaling factor magnitude. Comprehensive numerical simulations characterized their aerodynamic performance and flowfield structures under design (Ma0 = 7.0) and off-design (Ma0 = 6.0, 6.5) conditions. The numerical results reveal that, compared with conventional shock-on-lip (SOL) configurations, the cowl shock progressively attenuates with increasing r, resulting in a remarkable reduction in the scale of the separation bubble induced by the cowl shock and a significant improvement in the total-pressure recovery coefficient. At the design condition, an increase in the scaling factor results in a 32.52%–53.36% enhancement in throat total-pressure recovery coefficient, an 18.55%–30.57% reduction in entropy rise, and a 18.33%–72.01% decrease in the bleeding ratio. The inlet also demonstrates significantly enhanced aerodynamic performance under off-design conditions. Specifically, the mass flow ratio increases notably: at Mach 6.5 and 6.0, it rises by 4.29%–4.70% and 7.25%–8.46%, respectively, compared to the SOL configuration. The consistency in flowfield structures and throat-section aerodynamic parameters between the three-dimensional and two-dimensional inlets further confirms the applicability of the wave-configuration method under three-dimensional conditions. An optimal scaling factor range of 1.50–1.75 is identified, which effectively balances the performance metrics, substantially improving total-pressure recovery coefficient and minimizing the bleeding ratio without significantly compromising the pressure ratio characteristics.