A multi-code CFD solver for the efficient simulation of ramjet/scramjet inlet-engine coupled flowfields

In this paper, an efficient multi-code CFD solver is designed to simulate the integrated flows in a ramjet/scramjet air-breathing engine in a loosely coupled manner. That is, a multiblock, multigrid, single-species, turbulence flow solver is used to simulate the flows in the inlet, while a multi-species one to simulate the flows in the combustor and nozzle. These two loosely coupled on the interface of inlet-combustor conjunction cross section. The flow properties exchange mechanism of the two solvers across the interface is carefully constructed. To further speed-up the computation, a space-marching solver (SSPNS) is adopted to establish the initial single-species supersonic/hypersonic parts of the whole flowfields before the coupled computation starting. These three single-code CFD solvers mentioned above are constructed and validated separately early in our research team. The k-g two-equation turbulence model is used in the NS calculation; while turbulence affect is omitted in the SSPNS solver in this paper. In the multigrid algorithms the source terms of turbulence model and chemical reactions are dealt with the point-implicit method. The FAS-FMG multigrid methods based on V- and W-cycle are adopted for the single- and multi-species NS solver. Pressure damping is considered in the standard restriction and prolongation operators. The time-stepping smoothing methods of LU-SGS are adopted, while van Leer FVS schemes are used to discrete the inviscid fluxes, and center scheme to the viscous fluxes. The multi-code solver is successfully used to calculate the integrated flow field in a typical kerosene-fueled ramjet. The single-stage chemically reaction models are adopted to simulate the nonequilibrium flow. Numerical results show that the flow properties change smoothly across the inlet-engine interface, and the multi-code solver is very efficient for the engine integrated flow field simulation. It's also indicated that the ratio of specific heat across the interface should be dealt careful for the success of the coupled computations.