Flow past a square-section cylinder with a wavy stagnation face
Flow past a square-section cylinder with a wavy stagnation face
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DOI：
10.1017/s0022112000002299
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发表时间：
2001-01
影响因子：
3.7
通讯作者：
Rupad Darekar;S. Sherwin
中科院分区：
文献类型：
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作者：
Rupad Darekar;S. Sherwin
对具有展向几何变形的方形截面圆柱体的流动进行了数值研究，得到了具有正弦波度的停滞面。计算是在雷诺数从10到150的范围内使用谱/惠普单元求解器进行的。从经过雷诺数为100的直柱体的充分发展的脱落开始，脉冲地引入足够高的波浪度，从而使近尾迹稳定到与时间无关的状态。结果表明，展向波度在前缘表面的增长边界层内建立了横流，从而产生了涡度的流向和垂直分量。这些附加的涡度分量出现在波状滞流面拐点附近，在那里展向涡度减弱。这种涡量的重新分布导致非定常交错的Kármán涡尾迹分解为稳定的对称近尾迹结构。近尾迹的稳定性质与雷诺数为100时的总阻力比直的非波状圆柱的总阻力减少约16%有关。波浪度的进一步增大导致近尾迹区出现发夹型涡旋。这种尾迹拓扑与低雷诺数时球体的尾迹有相似之处。由于波动幅度的变化，尾迹的物理结构分为五个不同的区域。此外，在接近A模波长和直方截面圆柱体的主波长的波动度的引入使得Kármán街在最小的波动度幅度下被抑制。
Numerical investigations have been performed for the flow past square-section cylinders with a spanwise geometric deformation leading to a stagnation face with a sinusoidal waviness. The computations were performed using a spectral/hp element solver over a range of Reynolds numbers from 10 to 150. Starting from fully developed shedding past a straight cylinder at a Reynolds number of 100, a sufficiently high waviness is impulsively introduced resulting in the stabilization of the near wake to a time-independent state. It is shown that the spanwise waviness sets up a cross-flow within the growing boundary layer on the leading-edge surface thereby generating streamwise and vertical components of vorticity. These additional components of vorticity appear in regions close to the inflection points of the wavy stagnation face where the spanwise vorticity is weakened. This redistribution of vorticity leads to the breakdown of the unsteady and staggered Kármán vortex wake into a steady and symmetric near-wake structure. The steady nature of the near wake is associated with a reduction in total drag of about 16% at a Reynolds number of 100 compared with the straight, non-wavy cylinder. Further increases in the amplitude of the waviness lead to the emergence of hairpin vortices from the near-wake region. This wake topology has similarities to the wake of a sphere at low Reynolds numbers. The physical structure of the wake due to the variation of the amplitude of the waviness is identified with five distinct regimes. Furthermore, the introduction of a waviness at a wavelength close to the mode A wavelength and the primary wavelength of the straight square-section cylinder leads to the suppression of the Kármán street at a minimal waviness amplitude.