Experimental and numerical analysis on opposing jet for drag reduction in hypersonic flow with angles of attack

Abstract Opposing jet has been widely investigated as an effective aerodynamic drag reduction method in recent years. To study the impact of freestream angle of attack on the drag reduction effect of opposing jet, experimental and numerical approaches are employed to analyze the effects of jet pressure ratio, angle of attack, and jet deflection angle on the flow field structure and the underlying mechanism to drag reduction of the opposing jet in a Mach 6 freestream. The results indicate that, within the range of this study, drag reduction increases with higher jet pressure ratios, reaching a maximum reduction of 32.67% at a pressure ratio of 0.60. The drag reduction decreases as the angle of attack increases, with a 5.44% decline observed at 6° compared to 0°. This deterioration stems from the strong compression of the incoming flow on the windward side, which enhances the reattachment shock and increases the peak pressure dramatically. Additionally, at higher angles of attack, the adoption of an appropriate jet deflection angle can significantly enhance the effectiveness of drag reduction, achieving an improvement of up to 2.65%. Three typical flow fields are systematically summarized and analyzed, which have rarely been compared together in previous studies, namely the completely axisymmetric case, freestream with angle of attack but no jet deflection, and freestream with angle of attack while the jet undergoes deflection, respectively. Among all conditions, the position and distance away from the body of the intersection point of the bow shock and reattachment shock wave play a crucial role in drag reduction effect, shifting this point downstream and away from the surface significantly enhances the drag reduction effect.