On the flow generated on the leeward face of a rotating flat plate
On the flow generated on the leeward face of a rotating flat plate
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DOI：
10.1007/s00348-013-1495-5
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发表时间：
2013-03
影响因子：
2.4
通讯作者：
A. DeVoria;M. Ringuette
中科院分区：
文献类型：
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作者：
A. DeVoria;M. Ringuette
实验研究了低纵横比旋转梯形平板背风面产生的流动；运动是从静止到攻角为90°的推进冲程，雷诺数为0（103）。目的是表征在不同的板块运动学条件下，靠近板块尖端的流体速度。实验在水箱装置中进行，采用数字粒子图像测速法测量平面速度。在研究范围内，叶尖附近区域的流动对雷诺数相对不敏感。向板的分量不受总旋转幅度的影响，而切向分量则依赖于这个角度。此外，从近尖端速度数据中估计了第一次尖端涡掐断时间，并与使用环流估计的值非常吻合。随着旋转幅值的增加，大块根部到尖端流动相对于板法向的入射角变得更加倾斜。因此，切向速度的峰值幅度也增加了，结果使流体动量以更高的速率远离板块。随着旋转幅度的增加，根到尖端流动的更斜撞击对相关的垂直于板的流体动力力有明显的影响。对于冲动性板块减速，不可忽略力存在的时间减小，而对于非冲动性板块减速，当旋转幅值较大时，不可忽略力存在的时间和相对力的大小都减小。
We experimentally investigate the flow generated on the leeward face of a rotating trapezoidal flat plate of low-aspect-ratio; the motion is an advancing stroke from rest at 90° angle of attack with Reynolds numbers ofO(103). The objectives are to characterize the fluid velocity near the tip of the plate for different plate kinematics. The experiments are conducted in a water tank facility, and digital particle image velocimetry is performed to obtain planar velocity measurements. The flow in the region near the tip is relatively insensitive to Reynolds number over the range studied. The component normal to the plate is unaffected by total rotational amplitude, while the tangential component has dependence on this angle. Also, an estimate of the first tip vortex pinch-off time is obtained from the near-tip velocity data and agrees very well with values estimated using circulation. The angle of incidence of the bulk root-to-tip flow relative to the plate normal becomes more oblique with increasing rotational amplitude. Accordingly, the peak magnitude of the tangential velocity is also increased and as a result advects fluid momentum away from the plate at a higher rate. The more oblique impingement of the root-to-tip flow for increasing rotational amplitude is shown to have a distinct effect on the associated fluid dynamic force normal to the plate. For impulsive plate deceleration the time that a nonnegligible force exists decreases, while for nonimpulsive plate deceleration both this time and the relative force magnitude decrease for larger rotational amplitudes.