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Acta Aeronautica et Astronautica Sinica

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Effect of distributed ablation pattern on hypersonic flat plate boundary-layer instability

  

  • Received:2024-03-29 Revised:2024-06-24 Online:2024-06-25 Published:2024-06-25
  • Contact: Jie Wu

Abstract: After experiencing high-temperature ablation, the thermal protection material on the surface of hypersonic vehicle exhibits a pattern of distributed roughness element. However, the effect of such pattern on hypersonic boundary layer transition and its influencing mechanism have not been recognized at present, which has attracted the attention of transition researchers. In this study, wind tunnel experiments are carried out based on the Φ0.5m Mach 6 Ludwieg tube wind tunnel of Huazhong University of Science and Technology. The evolution of instability waves in the hypersonic boundary layer of the flat plate is studied in the cases of smooth and distributed roughness elements with four heights of h= 0.5, 1.0, 1.5 and 2.0 mm, and various of Reynolds number at 5.39 × 106 m-1~ 1.72 × 107 m-1. The effects of distributed roughness element height and incoming Reynolds numbers on the boundary layer instability of a flat plate are clarified. The experimental results show that the second mode instability waves dominate the instability of the hypersonic boundary layer in the cases of distributed roughness element, and the frequency range is about 60~120 kHz. For the distributed roughness element which is lower than the local bounda-ry layer thickness, it has obvious effect on the base flow in the boundary layer, but the height factor has little influ-ence on the transition position of the hypersonic boundary layer. The influence of the distributed roughness ele-ment height on the flow velocity of the second mode instability waves in the hypersonic plate boundary layer is non-monotonic, and there is a critical height that has the greatest influence. Under different Reynolds number inflow conditions, the characteristic evolution of the second mode instability waves in the smooth case and roughness case is basically the same, and the boundary layer transition position of different height roughness cases has little difference under the same Reynolds number.

Key words: hypersonic, ablation pattern, boundary layer transition, instability, flat plate model, wind tunnel experiment

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