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展向振动流向传播的波动壁面的湍流减阻

Turbulent drag reduction via a streamwise traveling wave induced by spanwise wall oscillation

  • 摘要: 采用直接数值模拟方法, 对槽道湍流中展向振动流向传播的波动壁面的流动控制和减阻问题进行了研究, 讨论了流向参数k_x对Stokes层、湍流拟序结构、湍流猝发事件以及壁面阻力的影响, 并对此类波动壁面的湍流控制和减阻机理进行了讨论. 结果表明, 当此类波动壁面被用来调制近壁流动时, 仅低频波对湍流流场具有显著影响, 可导致湍流猝发事件的频率和强度的显著变化; 波数k_x的增大对于湍流猝发事件的频率和强度增减的影响并不同步, 存在一个最优的波数k_x, 在其调制下, 固有流场对诱导流场的影响最弱, 而诱导流场对固有流场的影响显著, 减阻效果最好.

     

    Abstract: The flow control and drag reduction in turbulent channelflow via streamwise traveling wave induced by spanwise-wall oscillation areinvestigated by direct numerical simulation (DNS). The effects of streamwisecontrol parameter k_x on the Stokes layer, the near-wall flow structure,turbulent burst events, as well as the skin-friction drag are discussed. Inaddition, the mechanisms of turbulence suppression and drag reduction viastreamwise traveling wave induced by spanwise-wall oscillation are alsodiscussed. The results suggest that only the low-frequency waves have thesignificant influence on the flow field which induces the great variationsof frequency and the intensity of the burst which can be detected by thevariable-interval time averaging (VITA) detective technique. The variationsof the frequency and the intensity of the burst are unsynchronized as thek_x increases, and there exists an optimal parameter, k_x, in whichthe influence of the intrinsic flow on the induced flow is weakest, and onthe contrary, the intrinsic turbulent flow is modified strongly by theinduced flow, and the largest amount of drag reduction is obtained.

     

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