Optimal bypass shape design of low boom supersonic inlet

A low boom supersonic inlet (LBSI) is a new concept combining a relaxed isentropic compression supersonic inlet and bypass annular duct around the primary flow path to the engine fan face. It produces lower boom and cowl drag than a conventional inlet. The inlet performance, however, depends on the geometric and flow blockage in the bypass duct, which includes gearbox fairing and guiding struts in it. Here we conduct flow analyses for the supersonic bypass inlet and compared the present results with experimental and other CFD data. We also conducted optimal design of strut shapes in the bypass annulus to maximize inlet performance gradient based optimization method utilizing a discrete adjoint method is adopted for efficient shape design. Through a design study of the strut geometry, the inlet performance is recovered close to the initial design intent of the axisymmetric supersonic inlet.