Numerical Investigation of Flow in an Overexpanded Nozzle with Porous Surfaces

A new porous condition has been implemented in the PAB3D solver to simulate flow over porous surfaces. The newly added boundary condition is utilized to compute the flow field of a nonaxisymmetric, convergent-divergent nozzle incorporating porous cavities for shock-boundary layer interaction control. The nozzle has an expansion ratio (exit area/throat area) of 1.797 and a design nozzle pressure ratio (NPR) of 8.78. The flow fields for a baseline nozzle (no porosity) and for a nozzle with porous surfaces (10% porosity ratio) are computed for NPR varying from 2.01 to 9.54. Computational model results indicate that the overexpanded nozzle flow is dominated by shock-induced boundary-layer separation. Porous configurations are capable of controlling off-design separation in the nozzle by encouraging stable separation of the exhaust flow. Computational simulation results, wall centerline pressure, Mach contours, and thrust efficiency ratio are presented and discussed. Computed results are in excellent agreement with experimental data.