Plume-Induced Flow Separation over a Cone-Cylinder Flare Body

Abstract

The extent of boundary-layer separation due to the presence of a jet plume was studied for a cone-cylinder-flare configuration using the Overset Navier-Stokes CFD code, OVERFLOW. Simulations were made at a free-stream Mach number of 4.65 for nozzle exit pressure to free-stream pressure ratios ranging from jet off to 168. CFD results were obtained assuming a fully laminar boundary layer, fully turbulent boundary layer, and a laminar-turbulent transitional boundary layer. The one-equation Spalart-Allmaras (SA) and the two-equation SST model were compared for the turbulent cases. The effect of wall boundary conditions was studied by comparing the isothermal wall to the adiabatic wall conditions. CFD results were compared to existing experimental data obtained from the Langley Unitary Plan wind tunnel. The results indicate strong plume-induced flow separation when modeled as fully laminar and weak separation, if at all, when modeled as fully turbulent. The best agreement with experimental results was achieved when the trip location was placed near the end of the flare. The adiabatic wall boundary condition best suited the wind tunnel experiment. However predicting the extent of the plume induced flow separation with numerical simulations is still unreliable due to the extreme sensitivity of the flow field to turbulence models, boundary conditions, and nozzle pressure ratios.