Numerical Investigation of a Super-Sonic Inlet Using Bleed and Micro-Ramps to Control Shock-Wave/Boundary Layer Interactions

Abstract

[Abstract] A computational fluid dynamic investigation was conducted on a variable geometry supersonic mixed compression inlet. The regulating features of the inlet are a variable compression ramp, diffuser, and throat. The compression ramp rotates about the y-axis from 0-12 degrees, and throat heights ranging from 0.75 to 1.5 inches, which is coupled with the trailing edge of the variable diffuser. The inlet produces strong shockwave turbulent boundary layer interactions that cause the boundary layer to separate and diminish the overall performance of the inlet. To counter the adverse effects of shockwave turbulent boundary layer interactions the inlet is equipped to with several conventional bleed systems located along: the compression ramp, and in the throat, along the upper, lower, and sidewall surfaces. As an alternative to boundary layer bleed, the baseline inlet model was fitted with micro-ramps as a potentially more efficient method of turbulent boundary layer separation control. All numerical simulations were conducted using the AFRL developed Air Vehicles Unstructured Solver (AVUS). The CFD computations solve the compressible 3-D steady state Navier-Stokes equations coupled with the Wilcox (1998) k-ω two equation turbulence model. The bleed surfaces and micro-ramps are removable to incorporate numerical baseline testing. A major objective of the numerical simulations is to examine several inlet performance characteristics: total pressure recovery, mass flow, static pressures on the inlet surfaces, and flow distortion. Unstructured hybrid viscous computational grids were generated using Icemcfd and consisted of prisms, pyramids, and tetrahedron. All CFD computations were conducted at a freestream mach number of 3.0 and Reynolds number of 2.71 million/ft. Furthermore, controlling shockwave turbulent boundary layer interactions with micro-ramps has shown to enhance inlet efficiency.