Parametric Study on a Sinusoidal Riblet for Drag Reduction by Direct Numerical Simulation
Parametric Study on a Sinusoidal Riblet for Drag Reduction by Direct Numerical Simulation
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DOI：
10.1007/s10494-017-9805-2
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发表时间：
2017-04
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影响因子：
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通讯作者：
M. Sasamori;O. Iihama;H. Mamori;K. Iwamoto;A. Murata
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文献类型：
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作者：
M. Sasamori;O. Iihama;H. Mamori;K. Iwamoto;A. Murata
在摩擦雷诺数为110时，对具有正弦沟槽面的充分发展槽道湍流进行了直接数值模拟。在正弦肋中相邻壁的横向间距沿流向正弦变化。正弦型肋的平均横向间距大于准流向涡的直径，其润湿面积小于普通直型肋。本文研究了正弦沟槽设计参数对减阻率和流动统计特性的影响。参数研究表明，在摩擦雷诺数为110时，最大总减阻率约为9.8%。脊状结构分别在扩张区和收缩区产生向下流动和向上流动，从而产生周期性的雷诺切应力。然而，随机雷诺剪应力急剧下降相比，平坦表面的情况下，导致总阻力的减少，由于正弦脊。我们还进行了涡跟踪，以讨论运动的旋涡结构的正弦脊表面上旅行。对涡结构核心的涡跟踪和概率分析表明，涡结构由于正弦脊的存在而衰减，并遵循特征流。这些结果表明，高表面摩擦区域的通道壁是局部的扩展区域的肋壁。结果，肋的润湿面积减小，导致减阻效果。
The direct numerical simulation of fully developed turbulent channel flow with a sinusoidal riblet surface has been carried out at the friction Reynolds number of 110. Lateral spacing of adjacent walls in a sinusoidal riblet is varied sinusoidally in the streamwise direction. The average lateral spacing of a sinusoidal riblet is larger than the diameter of a quasi-streamwise vortex and its wetted area is smaller than that of ordinary straight-type riblets. We investigate the effect of sinusoidal riblet design parameters on the drag reduction rate and flow statistics in this paper. The parametric study shows that the maximum total drag reduction rate is approximately 9.8% at a friction Reynolds number of 110. The riblet induces downward and upward flows in the expanded and contracted regions, respectively, which contribute to periodic Reynolds shear stress. However, the random Reynolds shear stress decreases drastically as compared with the flat surface case, resulting in the reduction of total drag owing to the sinusoidal riblet. We also performed vortex tracking to discuss the motion of the vortical structure traveling over the sinusoidal riblet surface. Vortex tracking and probability analysis for the core of the vortical structure show that the vortical structure is attenuated owing to the sinusoidal riblet and follows the characteristic flow. These results show that the high skin-friction region on the channel wall is localized at the expanded region of the riblet walls. In consequence, the wetted area of the riblet decreases, resulting in the drag-reduction effect.