Abstract:

Drag reduction spikes can reduce the heat flow of the supersonic aircraft head at 0-degree angle of attack. However， the heat reduction effect sharply drops with the increasing angle of attack. To solve this problem， we propose the heat reduction scheme of the combination of annular jet and drag-reduction spike. Numerical simulations of this scheme under different inflow and jet conditions are carried out to obtain the flow filed and the wall heat flow distribution. The conclusions are as follows： in the flow field of the combined scheme， affected by the low-pressure area behind the drag-reduction spike， the jet does not directly interact with the free stream， and there is no transition between the long and short penetration modes， with the jet pressure ratios ranging from 0.05 to 0.40. Thus， the flow field structure of the reverse jet is more stable. Furthermore， the drag-reduction spike and the blunt body are coated by the reverse jet. The attached shock wave and separated shock wave are pushed away from the wall. The numerical results show that under the condition of 0° angle of attack， a small jet pressure ratio also has a good heat reduction effect. When the jet pressure ratio is 0.05， the peak heat flow on the blunt body wall can be reduced to smaller than half of the original value. The attached shock wave and separated shock wave generated by a single drag reduction spike at an angle of attack act directly on the blunt head wall， resulting in a sharp rise in the heat flow through the wall. The combined scheme has clear heat reduction effect with an angle of attack. With the increase of the angle of attack， the back pressure at the nozzle increases， while the interference effect of the jet on the flow field decreases. To achieve the same heat reduction effect， a larger jet pressure ratio is required. At the same jet pressure ratio， the jet flow before the reattachment point can make the jet flow expand more completely and reduce heat more effectively. At small jet pressure ratios， the drag reduction effect of the combined configuration of the drag reducing rod and the annular jet is enhanced compared to the single drag reducing rod.

Key words: jet, drag reduction spike, flow disturbance, aerodynamic heat, angle of attack, numerical simulation