Drag and heat flux reduction mechanism induced by the combinational forward-facing cavity and pulsed counterflowing jet configuration in supersonic flows

Abstract

The drag and heat flux reduction characteristics plays a very important role in the conceptual design phase and engineering realization of the aerospace vehicle. In the current study, a novel thermal protection system combining the forward-facing cavity and the pulsed counterflowing jet has been proposed, and three groups of the combinations with the same pulsed counterflowing jet but different forward-facing cavities are established. The waveform and period of the pulsed counterflowing jet are triangular waveform and T = 2 ms respectively, and the diameter of the jet nozzle is set to be d = 4 mm. The forward-facing cavities with L/D = 1.25, 1.33 and 1.75 has been taken into consideration. The cavity is placed at the nose of the blunt body, and the jet nozzle is placed at the center of the cavity surface. In the numerical investigation, an axisymmetric numerical simulation model of the counterflowing jet on the supersonic vehicle nose-tip is established, and a two-dimensional axisymmetric Reynolds-averaged Navier-Stokes (RANS) equations coupled with the two equation k-ω shear stress transport (SST) turbulence model are employed. The wall Stanton number distributions, as well as the surface static pressures, have been extracted from the flow field structures in order to evaluate the drag and heat flux reduction characteristics. Further, the influence of the length-to-diameter ratio of the cavity on the drag and heat flux reduction has been analyzed based on the wall Stanton number and surface pressure distributions. The obtained results show that The combinational forward-facing cavity and pulsed counterflowing jet configuration with L/D = 1.33 owns the best drag and heat flux reduction performance in the range considered in this paper, and the smaller cavity volume is beneficial for the stability of the flow field. There is an optimal value for the length-to-diameter ratio of the forward-facing cavity, and the optimal configuration for the thermal protection may be not the same as that for the drag reduction. This should be dealt with the multi-objective design optimization approaches.