Wake induced by an undulating elephant seal whisker
Wake induced by an undulating elephant seal whisker
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DOI：
10.1007/s12650-018-0484-4
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发表时间：
2018-08-01
影响因子：
1.7
通讯作者：
Zhang, Wei
中科院分区：
文献类型：
--
作者：
Bunjevac, Joseph;Turk, Jodi;Zhang, Wei
某些种类的海豹仅凭胡须就能忠实地探测到周围水中的微小扰动，这要归功于胡须起伏的三维（3D）形态。虽然以前的研究已经使用放大的须状模型检查了关键形态参数对尾流的影响，但尚不清楚在真实的波动海豹须诱导下尾流的行为。真正的海豹须的直径通常在一毫米左右，并且在长度上呈现大小和弯曲曲率的变化，这些在设计按比例放大的类似须的模型时没有考虑到。此外，晶须取向如何影响诱导尾迹和涡脱落需要澄清。本研究使用快照粒子图像测速（PIV）和时间分辨PIV方法，研究了在雷诺数为110和390的实验室水道中，真实海象须（波动形态）和加利福尼亚海狮须（光滑形态）产生的尾流特性。结果表明：与光滑晶须相比，当晶须横截面长轴与来流平行时（即攻角或AOA为0时），波动晶须后的反流区明显减小，湍流强度得到明显抑制；虽然波浪晶须和光滑晶须的涡脱落频率都降低了，但功率谱密度却大大增加了。在不考虑AOA的情况下，波动晶须尾迹的功率谱密度比光滑晶须的功率谱密度低约40%，表明波动晶须具有良好的水动力特性。波浪状海豹须独特的水动力特性为改进航空推进流体元件和设计高灵敏度水下流量传感器提供了良好的前景。
Certain species of seals are able to faithfully detect minute disturbances in ambient water solely using their whiskers, which is attributed to the whiskers' undulating three-dimensional (3D) morphology. While previous studies have examined effects of key morphology parameters on the wake using scaled-up whisker models, it is unclear how the wake behaves when induced by a real undulating seal whisker. Real seal whiskers usually have a diameter of about one millimeter and present variation in size and bending curvature along the length, which are not being considered in designing scaled-up whisker-like models. In addition, how the whisker orientation affects the induced wake and vortex shedding needs to be clarified. This work examines the wake flow characteristics generated by a real elephant seal whisker (of undulating morphology) and a California sea lion whisker (of smooth morphology) in laboratory water channels at Reynolds numbers of 110 and 390, using snapshot particle image velocimetry (PIV) and time-resolved PIV methods. Results indicate that the reversed flow region is remarkably reduced and turbulence intensities are greatly suppressed behind the undulating whisker compared to that of the smooth whisker, when the major axis of the whisker cross-section is parallel with the incoming flow (i.e., the angle of attack or AOA is 0). While the vortex shedding frequency is reduced for both the undulating and smooth whiskers, the power spectral density is substantially increased at an in comparison to . Regardless of the AOA, the power spectral density is approximately 40% lower in the wake of the undulating whisker than that of the smooth whisker, indicating the favorable hydrodynamic feature of the undulating whisker. The extraordinary hydrodynamic traits of undulating seal whiskers is promising for renovating aero-propulsion flow components and designing high-sensitivity underwater flow sensors.