Abstract: The inward turning inlet is with better inlet capture ability and higher air compression efficiency. However, this kind of inlet cannot be adjusted locally in the preliminary design, and it is difficult to improve the adverse effects of complex flow structures such as flow separation and secondary flow caused by shock/boundary layer interference. Therefore, there is still the large space for performance optimization. Nowadays, the design optimization of hypersonic inward turning inlet faces many challenges, such as the complex profile, large-scale design variables, and the high accuracy requirement of the flowfield numerical simulation. Therefore, this study adopts the gradient optimization method based on discrete adjoint to carry out the aerodynamic design optimization for the inward turning inlet with wedge forebody. The optimization results show that the undulating shape of the inner and outer compression sections significantly changes the internal shock structure, reduces the wall pressure gradient, and thereby abates the streamwise vortex. In addition, the interference intensity between the shock train and the boundary layer in the isolation section is significantly weakened, which inhibits the expansion of the low energy flow region. At the design condition, compared with the initial configuration, the aerodynamic performances of the optimized configuration are significantly improved. The total pressure recovery coefficient, the flow coefficient and the pressure ratio at the exit are increased by 8.748%, 0.171% and 0.766% respectively, and the drag is reduced by 1.624%.

Key words: hypersonic, inward turning inlet, discrete adjoint, gradient-based optimization, aerodynamic design