A comparison of opposition control in turbulent boundary layer and turbulent channel flow
A comparison of opposition control in turbulent boundary layer and turbulent channel flow
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DOI：
10.1063/1.4923234
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发表时间：
2015-07-01
影响因子：
4.6
通讯作者：
Hasegawa, Y.
中科院分区：
文献类型：
--
作者：
Stroh, A.;Frohnapfel, B.;Hasegawa, Y.
本文对应用于充分发展的槽道湍流和应用于空间发展的湍流边界层的经典反向控制进行了比较。结果发现，控制方案产生类似的减阻率相比，在相同的摩擦雷诺数。然而，对表面摩擦系数的动态贡献的详细分析揭示了减阻背后的机制的显着差异。虽然湍流槽道流中的减阻完全基于雷诺剪应力的衰减，但就可实现的减阻而言，空间流动发展的修改对于湍流边界层是必不可少的。结果表明，由于这种空间发展的贡献，减阻变得更加明显，随着雷诺数的增加（高达Re-tau = 660，基于摩擦速度和边界层厚度），甚至超过由于雷诺剪切应力的衰减减阻。在整体能量平衡方面，它被发现，反对派控制是不太有效的湍流边界层由于固有的较大的波动强度在近壁区域。(C)2015 AIP Publishing LLC.
A comparison between classical opposition control applied in the configuration of a fully developed turbulent channel flow and applied locally in a spatially developing turbulent boundary layer is presented. It is found that the control scheme yields similar drag reduction rates if compared at the same friction Reynolds numbers. However, a detailed analysis of the dynamical contributions to the skin friction coefficient reveals significant differences in the mechanism behind the drag reduction. While drag reduction in turbulent channel flow is entirely based on the attenuation of the Reynolds shear stress, the modification of the spatial flow development is essential for the turbulent boundary layer in terms of achievable drag reduction. It is shown that drag reduction due to this spatial development contribution becomes more pronounced with increasing Reynolds number (up to Re-tau = 660, based on friction velocity and boundary layer thickness) and even exceeds drag reduction due to attenuation of the Reynolds shear stress. In terms of an overall energy balance, it is found that opposition control is less efficient in the turbulent boundary layer due to the inherently larger fluctuation intensities in the near wall region. (C) 2015 AIP Publishing LLC.