Full Navier-Stokes analysis of a three-dimensional hypersonic mixed compression inlet

Abstract

THREE-DIMENSIONAL effects in a mixed compression inlet typical of supersonic combustion ramjet engine are studied using a full Navier-Stokes analysis method. The solution procedure uses a multistep pressure correction method with an implicit density treatment to establish the pressure and velocity fields. The strong shocks are captured using a smart numerical dissipation scheme that adapts monotonically at extrema. Numerical solutions for a mixed compression forebody/inlet are presented including performance calculations. Contents The two-dimensional analysis of hypersonic inlets has advanced dramatically in the past few years. The understanding and analysis of the three-dimensional effects that would be present at hypersonic inlet Mach number are not as advanced. Effects that occur due to ramp splitter plates and shock/ sidewall-boundary-layer interaction may play an important role in the inlet. To estimate three-dimensional effects, a hypersonic compression ramp and inlet flowfield for a generic vehicle is analyzed in the present work. The present method is based on the generalized implicit pressure-based Navier-Stokes method (NASTAR computer code) previously validated for flows ranging from incompressible to hypersonic flow speeds.1'2 The major challenge in hypersonic flow calculation is to develop an accurate shockcapturing capability. The present discretization approach is to use second-order central differencing plus numerical dissipation using a nonstaggered grid arrangement. Rhie1 demonstrated that the numerical dissipation using the limiting gridcell Reynolds-number concept produced accurate results for flows with nominal shocks. The present approach is to extend the previous limiting grid-cell Reynolds-number method for automatic adaptation across strong shocks. The details can be found in Ref. 2. Many questions exist as to the effect of flow three-dimensionality on the performance of a scramjet inlet and combustor. The three-dimensionality effects of greatest concern are created by the presence of splitter plates on the forebody (Fig. I) and the cowl shock sidewall boundary-layer interaction in the inlet. To investigate these concerns, a generic splitter plate/ramp and inlet geometry were devised and analyzed using a three-dimensional full N .vier Stokes (FNS) code. The splitter plate/ramp and inlet geometry shown in Fig. 1 were for a hypothetical scramjet engine that was operating at Mach 15 with a dynamic pressure of 47,880 N/m2.