Effects of wavelength on vortex structure and turbulence kinetic energy transfer of flow over undulated cylinders
Effects of wavelength on vortex structure and turbulence kinetic energy transfer of flow over undulated cylinders
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DOI：
10.1007/s00162-023-00661-2
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发表时间：
2022-06
影响因子：
3.4
通讯作者：
Kathleen Lyons;R. B. Cal;Jennifer A. Franck
中科院分区：
文献类型：
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作者：
Kathleen Lyons;R. B. Cal;Jennifer A. Franck
被动流动控制通常用于钝体上，以减少一系列工程应用中的阻力和振荡升力。这项研究探索了一种受密封须启发的横向波动圆柱体，与光滑圆柱体相比，它可以减少水动力。尽管流体在这种复杂几何结构上的流动已经通过实验和计算得到了记录，但围绕波动地形的几何变化的研究仍然有限，并且诱导力减小的流体机制尚未得到充分研究。在雷诺数下模拟了波动波长的五种变化，并与光滑椭圆圆柱体的结果进行了比较。分析了尾迹中的涡流结构和湍流动能传递，解释了波动波长对减力的影响。波动波长的改变产生各种流动模式，包括交替涡旋滚子和发夹涡。在足够大的波长上观察到最大的力减少，以允许发夹漩涡在不相互相交的情况下发展，并且足够小以防止产生额外的交替流动结构。由于平均应变和波动应变的变化，流动结构的差异改变了TKE产生和耗散的大小和位置。减少TKE产生和增加近尾迹的耗散导致整体TKE降低和力减小。了解流动物理连接几何形状的力量减少将指导适当的参数选择在仿生设计应用。图形抽象
Passive flow control is commonly used on bluff bodies for drag and oscillating lift reduction across a range of engineering applications. This research explores a spanwise undulated cylinder inspired by seal whiskers that is shown to reduce hydrodynamic forces when compared to smooth cylinders. Although the fluid flow over this complex geometry has been documented experimentally and computationally, investigations surrounding geometric modifications to the undulation topography have been limited, and fluid mechanisms by which force reduction is induced have not been fully examined. Five variations of undulation wavelength are simulated at Reynolds numberand compared with results from a smooth elliptical cylinder. Vortex structures and turbulence kinetic energy (TKE) transfer in the wake are analyzed to explain how undulation wavelength affects force reduction. Modifications to the undulation wavelength generate a variety of flow patterns including alternating vortex rollers and hairpin vortices. Maximum force reduction is observed at wavelengths that are large enough to allow hairpin vortices to develop without intersecting each other and small enough to prevent the generation of additional alternating flow structures. The differences in flow structures modify the magnitude and location of TKE production and dissipation due to changes in mean and fluctuating strain. Decreased TKE production and increased dissipation in the near wake result in overall lower TKE and force reduction. Understanding the flow physics linking geometry to force reduction will guide appropriate parameter selection in bio-inspired design applications.Graphic abstract