Numerical study of interaction between a supersonic plume and the base region of the National Aerospace Plane.

摘要

A numerical investigation of the two dimensional interaction between a supersonic jet plume and the afterbody of the National Aerospace Plane (NASP) is performed for the analysis of complicated flow phenomena. A simple flat base surface with or without ramp angle is selected for this purpose.; A variety of flow problems such as flow past an airfoil, rocket afterbody flow, and compression corner flow are chosen for code validation. A central differencing scheme, symmetric and upwind TVD schemes are applied to these problems. For transonic flow around an airfoil, all codes produced reasonable convergence for inviscid computations, but the central differencing scheme with added artificial dissipation was the most robust scheme of the three for the viscous computations.; The problem of rocket afterbody flow is solved for both underexpanded and overexpanded cases and all features typical of afterbody type of flow, such as the shock structure internal to the jet core flow, recompression shocks, and shear layer are clearly predicted.; In another attempt to assess the capability of the flow codes, three computational schemes are applied to a compression corner with various ramp angles. The thin layer Navier-Stokes approximation and the Baldwin-Lomax algebraic turbulence model, which are used throughout this study, prove to be able to predict the complicated flow patterns as well as separation and reattachment.; Finally, the validated code is applied to the main problem of NASP/afterbody flow. The upwind code is applied to this case and essential features of the flow, including the shear layer, are appropriately predicted. The adaptive grid is applied a few times in the course of obtaining the steady state solution for improved convergence and precise description of the shear layers. The hypersonic cruise speed of the NASP necessitates the inclusion of chemical effects into the flow code. The selection of the number of species and reactions is an important factor, considering the enormous computational time required to solve the problem. One-dimensional flow with species concentrations given across an arbitrarily assigned area is solved for hydrogen-air combustion. Six species (excluding nitrogen) and eight reactions are selected for future computations with chemical effects.