Effect of Boundary-layer Bleed System on Radar Stealth and Aerodynamic Performances of S-duct Caret Intake

By using the shear stress transport (SST) k-ω turbulence model and the multi-stage fast multipole method (MLFMM) to respectively calculate the viscous flow and the surface current, the radar stealth and aerodynamic performances of the S-duct caret intakes with different boundary-layer bleed (BLB) systems were numerically investigated. Compared with the diffuser bleed system, the throat system more effectively improved the airflow capacity of the traditional S-duct intake with more significant increase in the radar cross section (RCS). By changing the outlet offset direction and using the local bleed system, the average RCS of the new double S-duct intake decreased below - 1.2db and the distortion index DC60 reduced to 0.17, with the total pressure loss slightly increased. The baffle board reduced the stealth performance loss caused by the throat bleed system effectively with the bleed effect ensured. By applying the two bleed system and the baffle board, the airflow capacity of double S-duct intake was significantly improved with the average RCS less than -0.5db and the DC60 of 0.16 at the designed outlet pressure.