Numerical analysis of scramjet internal flow by hybrid unstructured grid method

Computations of internal viscous flowfields of scramjet models were conduct ed at inflow Mach numbers of 3.4 and 5.45. A hybrid unstructured grid metho d was used to compute the scramjet models with and without a short strut. T he numerical method to solve the Navier-Stokes equations on the hybrid unst ructured grid was developed using a finite volume cell vertex scheme and th e lower-upper symmetric Gauss-Seidel (LU-SGS) implicit time integration alg orithm. The computational results revealed that a thick subsonic region did not exist in the combustor near the top wall at Mach number 5.45. It was a desirable feature to avoid unstarting the engine. With the use of a strut, the relatively low velocity regions increased and the downward flow toward the cowl behind the step became strong. An overconcentration of fuel towar d the top wall during weak combustion was observed in the experiment. The r eason for this was that the airflow near the injector was turned to the top wall due to the small influence of combustion in the experiment.