Numerical Study of the Effects of a Counterflow Jet on the Drag Reduction of a Blunt Body in a Hypersonic Flow

A numerical investigation has been conducted for the drag reduction of a counterflow jet with a blunt body at Mach 6. The computational study was carried out by solving two-dimensional axisymmetric Reynolds-averaged Navier–Stokes (RANS) equations. The Spalart–Allmaras one-equation turbulence model was used in this study. The jet flow of exit Mach number 2.86 interacts with the free stream and changes the single shock structure to a multiple shock structure. The purpose of this study was to investigate the influence of the stagnation pressure based on a parameter, the momentum parameter ratio (MPR), which can characterize the jet. The result shows that the flow field can be categorized as being in a long penetration mode (LPM) or short penetration mode (SPM) depending on the penetration length of the free-stream flow. In the LPM, under overexpanded jet conditions, the shock structure fluctuates continuously, so the flow field is unstable. On the other hand, in the SPM, the shock structure is nearly fixed, and the entire flow field is stable. For this reason, even if the penetration length of the flow field in the SPM is less than that in the LPM, the aerodynamic drag can be reduced by up to 40%. Therefore, it becomes clear that jet pressure conditions can significantly improve aerodynamic performance by reducing the drag applied to the blunt body.