Influence of rudder-tip opposing jet on shock wave/boundary layer interaction and heat flux regulation

Severe shock wave/boundary layer interaction (SWBLI) at the high-speed rudder tip results in an extremely harsh local thermal environment. In this paper, numerical simulations are employed to investigate the effects of an opposing jet on the shock structure and flow separation characteristics near the blunted rudder tip. The numerical method was validated against experimental data from open literature and grid independence analysis was conducted. The results indicates that the regulation of the flow field at the rudder tip by the opposing jet primarily presents as a Weak Interaction-Detachment Mode and a Strong Interaction-Coupling Mode. In the Weak Interaction-Detachment Mode, the main shock system is pushed away from the wall by the jet through momentum offset, and a stable low-temperature coverage layer is formed. The stagnation point heat flux at the rudder tip is reduced to nearly 0 kW/m², while a maximum drag reduction of 18.0% is achieved. In the Strong Interaction-Coupling Mode, a strong separation shock is induced by the rapidly expanding separation bubble and intersects intensely with the jet wave system. This interaction leads to a peak heat flux at the leading edge exceeding 3500 kW/m² and causes significant flow blockage at the gap entrance. A positive angle jet, which deviates from the rudder bottom surface toward the mainstream direction, effectively suppresses the rudder tip heat flux and achieves drag reduction. Conversely, a negative angle jet directed toward the gap interior and the rudder bottom surface aggravates the flow separation of the plate boundary layer, producing an extreme peak heat flux as high as 6900 kW/m². The peak heat flux is reduced to below 900 kW/m² by the opposing jet at a 20° rudder deflection, and the thermal load in the gap is effectively relieved. It is confirmed that the aerodynamic and thermal environment of the model is effectively improved by the opposing jet through the reconstruction of the rudder tip shock system and low-temperature coolant coverage under appropriate parameters.