Rarefaction Effect on the Aerodynamic Performance of Scramjet Inlet in Hypersonic Flow

Accurate prediction of the performances of the scramjet inlet is very imperative to design the advance hypersonic vehicles which usually operate in a low-density fly environment. However, the majority of corresponding researches related to the inlet performance are limited in the continuum region by solving the conventional Navier-Stokes equation (NS solver). In this paper, the primary objective is to examine the rarefaction effect on the aerodynamic performance of scramjet inlet based on the parallel DSMC. First, both the DSMC and NS methods are compared by simulating the low-density hypersonic flow around a scramjet inlet which has been tested in the experiment before. It can be found that NS solver fails to capture the rarefaction flow structure, while the DSMC's solutions match the experimental data well. Then, several hypersonic flow fields with different degrees of rarefaction by changing the flight height are investigated by using DSMC. Some convincing quantitative numerical results related to the flow fields are obtained. The corresponding inlet performance's parameters, such as total pressure recovery coefficient, pressure ratio and flow coefficient, are also compared in details. The numerical results show that a thick viscous layer, which is one of the predominant features of this type of flow field, grows to a thickness almost larger than the height of duct passage with the increase of the rarefaction. Furthermore, shock-boundary layer interactions near the juncture move forward which will greatly affect the inlet performances. These conclusions are very useful to the design of future configuration of hypersonic scramjet inlets.