On the design of optimal compliant walls for turbulence control
On the design of optimal compliant walls for turbulence control
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DOI：
10.1080/14685248.2016.1181267
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发表时间：
2016-04
影响因子：
1.9
通讯作者：
M. Luhar;Ati S. Sharma;B. McKeon
中科院分区：
文献类型：
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作者：
M. Luhar;Ati S. Sharma;B. McKeon
摘要本文采用预解式框架来考虑柔性壁面的设计以减少湍流表面摩擦。具体而言，简单的弹簧阻尼墙的效果与更复杂的墙壁，包括张力，刚度和各向异性的效果进行对比。此外，不同的质量比进行了测试，以提供洞察空气动力学和流体动力学应用之间的差异。尽管物理反应不同，但所有测试的墙壁都表现出一些重要的共同特征。首先，壁的影响（正或负）在接近谐振的条件下最大，在谐振频率或相速度上性能急剧转变。第二，柔顺壁预计有一个更明显的影响，较慢的移动结构，因为这样的结构通常有较大的壁压签名。第三，二维（展向常数）结构特别容易进一步放大。这些特征与许多先前的实验和模拟一致，表明减轻这种二维结构的上升对于设计性能改善的墙壁至关重要。例如，它示出，进一步放大这种大规模的二维结构解释了为什么在以前的直接数值模拟中确定的最佳各向异性壁只导致在非常小的域中的阻力减少。上述观察结果用于开发设计和方法的指导方针，为未来的研究顺应墙。
ABSTRACT This paper employs the resolvent framework to consider the design of compliant walls for turbulent skin friction reduction. Specifically, the effects of simple spring–damper walls are contrasted with the effects of more complex walls incorporating tension, stiffness and anisotropy. In addition, varying mass ratios are tested to provide insight into differences between aerodynamic and hydrodynamic applications. Despite the differing physical responses, all the walls tested exhibit some important common features. First, the effect of the walls (positive or negative) is the greatest at conditions close to resonance, with sharp transitions in performance across the resonant frequency or phase speed. Second, compliant walls are predicted to have a more pronounced effect on slower moving structures because such structures generally have larger wall-pressure signatures. Third, two-dimensional (spanwise constant) structures are particularly susceptible to further amplification. These features are consistent with many previous experiments and simulations, suggesting that mitigating the rise of such two-dimensional structures is essential to designing performance-improving walls. For instance, it is shown that further amplification of such large-scale two-dimensional structures explains why the optimal anisotropic walls identified in previous direct numerical simulations only led to drag reduction in very small domains. The above observations are used to develop design and methodology guidelines for future research on compliant walls.