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首页> 外文期刊>Bulletin of the American Physical Society >APS -70th Annual Meeting of the APS Division of Fluid Dynamics- Event - Reversing flow causes passive shark scale actuation in a separating turbulent boundary layer
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APS -70th Annual Meeting of the APS Division of Fluid Dynamics- Event - Reversing flow causes passive shark scale actuation in a separating turbulent boundary layer

机译：APS-APS流体动力学分部第70届年会-事件-逆流导致分离的湍流边界层中的被动鲨鱼鳞致动

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Control of flow separation by shortfin mako skin in experiments has been demonstrated, but the mechanism is still poorly understood yet must be to some extent Re independent. The hypothesized mechanisms inherent in the shark skin for controlling flow separation are: (1) the scales, which are capable of being bristled only by reversing flow, inhibit flow reversal events from further development into larger-scale separation and (2) the cavities formed when scales bristle induces mixing of high momentum flow towards the wall thus energizing the flow close to the surface. Two studies were carried out to measure passive scale actuation caused by reversing flow. A small flow channel induced an unsteady, wake flow over the scales prompting reversing flow events and scale actuation. To resolve the flow and scale movements simultaneously we used specialized optics at high magnification (1 mm field of view) at 50,000 fps. In another study, 3D printed models of shark scales, or microflaps (bristling capability up to 50 degrees), were set into a flat plate. Using a tripped, turbulent boundary layer grown over the long flat plate and a localized adverse pressure gradient, a separation bubble was generated within which the microflaps were placed. Passive flow actuation of both shark scales and microflaps by reversing flow was observed.
机译：实验中已经证实了通过短鳍鲨鱼皮控制流分离的机制，但是对这种机制的了解还很少，但在某种程度上必须与Re无关。鲨鱼皮固有的控制流分离的假想机理是：（1）鳞片，仅能通过逆向流动将其刷毛，抑制流向逆转事件进一步发展成较大规模的分离，以及（2）形成的空腔当水垢产生时，刷毛会引起高动量流向壁的混合，从而为靠近表面的流提供能量。进行了两项研究，以测量由逆向流动引起的被动秤驱动。一个小的流动通道会在秤上引起不稳定的尾流，从而促使反向流动事件和秤致动。为了同时解决流量和刻度运动，我们使用了高倍率（1毫米视场），50,000 fps的专用光学元件。在另一项研究中，将鲨鱼鳞或微瓣（鬃毛能力高达50度）的3D打印模型放置在平板上。使用在长平板上生长的跳动的湍流边界层和局部负压梯度，产生了分离气泡，微瓣被放置在其中。观察到通过逆向流动对鲨鱼鳞片和微瓣的被动流动驱动。

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