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微槽-波纹壁面对平板边界层第一/二模态波影响研究

EFFECTS OF MICROGROOVED-WAVYWALL ON THE FIRST/SECOND MODE WAVES IN FLAT PLATE BOUNDARY LAYER

  • 摘要: 高速边界层转捩会使飞行器表面的热流和摩阻显著增加, 延迟边界层转捩对飞行器降热减阻具有重要意义. 在以第二模态主导的高速边界层转捩过程中, 适当位置布置的波纹壁和微槽道均能够有效地抑制第二模态的增长, 从而达到延迟边界层转捩的效果. 研究了微槽-波纹组合壁面对马赫数4.5平板边界层稳定性的影响, 通过改变微槽的开槽方向(垂直壁面和竖直向下)、开槽数、孔隙率、开槽深度以及开槽位置等方式, 考察了这些微槽参数对第一/二模态波的作用效果. 研究结果表明: 相比光滑波纹壁面, 微槽-波纹组合壁面促进了第一模态波的增长, 增强了对低频第二模态波的抑制效果, 对高频第二模态波的抑制效果没有明显的提高; 开槽方向对微槽-波纹组合壁面的控制效果没有明显影响; 开槽位置对微槽-波纹组合壁面的控制效果有显著影响, 在波纹壁波峰处开槽时增强对第二模态波的抑制效果, 但同时也会促进第一模态波的发展.

     

    Abstract: Boundary layer transition (BLT) at high speed increases the heat flux and friction significantly. Delaying BLT is of great significance to reduce the heat and drag of aircraft. For BLT dominated by the second mode instabilities, the wavy wall and microgrooves arranged in proper positions can effectively suppress the growth of the second mode waves, thus delaying the BLT. By combining microgrooves and wavywall, the influence of the microgrooved-wavywall on the first/second mode instabilities in the boundary layer of a Mach 4.5 flat plate is studied. By changing the microgroove direction (orthogonal to the wavywall and vertical downward), quantity, depth, porosity, and position, the effects of these microgroove parameters on the first/second mode waves were investigated. The results show that compared with the smooth wavywall, the microgrooved-wavywall promotes the growth of the first mode waves, enhances the suppression effect of the low-frequency second mode waves, and has marginal influence on the suppression effect of the high-frequency second mode. The microgroove direction has no obvious influence on the control effect of microgrooved-wavywall. The microgroove position has significant influence on the control effect. The microgrooves at the crest of wavy wall enhance suppression effect on the second mode waves, but it also promotes the development of the first mode waves.

     

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