Flow Control for a Submerged Inlet

Submerged inlets have the advantages of low drag, clean outer profile, and excellent stealth performance. Previous studies indicate that the zones of large total-pressure loss, located at the bottom and top regions of the exit plane, are the main cause of the poor aerodynamic performance in a submerged inlet. To improve the performance, a flow-control method is proposed in this paper, which includes both ramp side boundary layer bleeding and entrance side-edge vortex diverting. With numerical simulations, the efficacy of the proposed flow control is examined by comparing the aerodynamic performance and flow-field pattern of a baseline inlet and a controlled inlet over the typical flight envelope. The results prove that the proposed flow-control method can effectively discharge the low-energy flow of the forebody boundary layer on the ramp and isolate the major low-energy flow of the side-edge vortex. The proposed flow-control method results in a large improvement in the aerodynamic performance over the whole flight envelope. Specifically, the total pressure recovery (σ) of the inlet with the proposed flow-control features raises 3.06%, and the distortion (DC₆₀) and the swirl distortion (SC₆₀) lessen by 72.57% and 17.73%, respectively, in contrast to the baseline inlet under the engine matching point of cruise state (⁠$Ma0=0.72, α=2 deg, β=0 deg, Ma2=0.39$⁠).