Flow Simulation of Supersonic Inlet with Bypass Annular Duct

A supersonic inlet comprising a bypass annulus and a relaxed isentropic compression is a new concept that produces smaller cowl drag than a conventional inlet, but incurs lower total pressure recovery and increased flow distortion in the (radially) outer flow path. A reliable CFD solution can provide considerable useful information to ascertain quantitatively relative merits of the concept, and further provide a basis for optimizing the design. For a fast and reliable performance evaluation of the inlet, we propose an equivalent axi-symmetric model whose area changes accounts for geometric and physical (blockage) effects resulting from the original complex three-dimensional configuration. In addition, full three-dimensional calculations are conducted for studying flow phenomena and verification of the equivalent model. Inlet-engine coupling is made by embedding NPSS engine data into the flow solver for interactive boundary conditions at engine fan face and exhaust plane. It was found that the blockage due to complex three-dimensional geometries in the bypass duct causes significant degradation of inlet performance by pushing the terminal normal shock upstream.