CFD Validation for Base Flows with and without Plume Interaction

摘要

In the framework of the NATO-RTO-AVT-WG-10 entitled 'Technologies for Propelled Hypersonic Flight,' base flow test cases have been selected for code validation. Concerning the first data set devoted to base flow-plume interaction at moderate nozzle pressure ratios, the influence of numerical discretization technique and turbulence models are discussed. The multi- dimensional upwind (MDU) discretization technique on unstructured grids applied to the axisymmetric base flow model with an under-expanded jet predicts base pressures that are consistently lower than the experimental values. If no proper conclusions can be drawn from this comparison because of the 3-D model support influence in the experiments, conclusions in relation to the turbulence models and to the axisymmetric results of the other code, the finite-volume technique on multi-block grids (LORE), may be of interest. Concerning the second dataset of a boat-tailed afterbody flow field with plume-induced- separation, RANS calculations with transport equations turbulence models reproduce the general organization of the flow, in particular the free separation phenomenon with a lambda-shock system induced by the jet/external flow interaction. The afterbody wall-pressure profile on the cylindrical part and during the expansion wave is well restituted. But it seems difficult to predict accurately the afterbody wall-pressure profile on the boat-tail because turbulence models have difficulties to reproduce positive pressure gradients. Calculations do not reveal the existence of a singular reflection on the symmetry axis for the recompression barrel shock of the propulsive jet, with a Mach disc, as it has been experimentally observed.