Aerodynamic design optimization of the hypersonic inward turning inlet in wide-speed range.

This article focuses on the multipoint aerodynamic shape optimization of a three-dimensional hypersonic inward turning inlet with a rectangular-to-elliptical shape transition, aiming to improve its performance across a wide-speed range. Using a discrete adjoint optimization method combined with free form deformation and a Reynolds averaged Navier–Stokes solver, the study employs 3,180 design variables and achieves an optimized inlet after 67 iterations. The optimized inlet demonstrates significant improvements in total pressure recovery coefficient and mass flow rate under both design and off-design Mach numbers (4, 5, and 6), primarily by inducing hump-like deformations that weaken shock waves and shock wave/boundary layer interactions, thereby reducing spillage and total pressure loss. The study also highlights that differing flow patterns at various Mach numbers create conflicting deformation requirements, making the optimization a tradeoff across conditions, and suggests the optimized design as a reference for air-breathing engine inlets in wide-speed-range hypersonic vehicles.