Numerical Investigation of a Counter-flow Jet with Various Mass Flow Rates at Hypersonic Flow over a Spherically Blunt Body in Low-Reynolds Number Regime

This study describes an counter-flow jet that used for drag reduction by controlling the flow field at hypersonic flow. As the design parameters of the counter-flow jet are correlated each other, it is difficult to investigate the dominant design parameters for transition of the flow field. Additionally, it is required to investigate the effect of the counter-flow jet at various flight conditions such as low-Reynolds number (Re < 10^4) regime to high-Reynolds number (Re = 10^5) regime. However, because of the difficulties of the experimental setup, there are few studies with counter-flow jets in a low Reynolds number regimes. In order to solve these kinds of problems, the numerical simulations were conducted to investigate the effect of the mass flow rate at fixed exit Mach number of the counter-flow jet to 2.86. For numerical simulations, the laminar, axi-symmetric, Navier-Stokes equations were solved by the symmetric total variation diminishing (TVD) schemes with second-order accuracy in space and explicit strong stability preserving Runge-Kuta (SSPRK) method. To investigate the effect of the mass flow rate, the nozzle exit radius of the counter-flow jet was ranged from 0.02 R to 0.06 R, while R represents the radius of the spherically blunt of the model. The pressure ratio was ranged from 0.50 to 0.75 while the free-stream Mach number was 6. The numerical results show that the flow field can be classified as SPM, LPM, LPPOM, or stable LPM by controlling the mass flow rate at specific pressure ratio. In terms of the drag reduction, the drag can be reduced by up to 78 %.