Collaborative Research: Experimental Studies to Reveal the Boundary Layer Control Mechanisms of Shark Skin

Hueter，0931787这项实验工作将研究一种新的和独特的被动边界层分离控制方法，来自鲨鱼皮，在微观尺度上发挥作用。鲨鱼的皮肤和鳞片代表了超过4亿年的自然选择。鲨鱼皮肤的形态结构的进化适应，发展独特的边界层控制（BLC）机制，源于随之而来的阻力减少，可能增加鳍的性能（如推力生产）和提高快速游泳鲨鱼的转向敏捷性。先前的工作，由PI证实，已经显示了鲨鱼栖息地的能力，以刚毛。PI发现，刚毛微几何形状导致形成互锁嵌入式空腔涡旋系统。假设三种机制，导致边界层控制通过威慑分离鲨鱼皮肤。第一种机制是嵌入式微涡的形成，由于部分滑移条件导致外边界层流动，微涡增加了非常近壁区域的动量。第二种机制是表面几何形状中固有的优先流动方向抑制了全局流动逆转。第三种机制发生在过渡和湍流边界层条件下，涉及与空腔的流动交换，导致湍流增强，或近壁区域和空腔中的流动的额外激励。这项研究涉及工程师，与生物学家合作，以充分理解鲨鱼栖息地的形态学刚毛机制。这项研究将提供第一个全面的表征的形态机制，导致齿状突起，并将分类的范围和程度（或角度）的刚毛，产生数据的鲨鱼皮肤模型的水动力学测试的建设。三个被动BLC机制将通过流动可视化和测量使用时间分辨数字粒子图像测速（TR-DPIV）进行评估。需要BLC领域的创新来提供有效的方法来减少阻力（导致增加有效载荷、航程或燃料节省）、改善控制表面的性能并增强现代技术的转向敏捷性（例如，潜艇、飞机）。将通过期刊/会议记录和公共媒体（例如加拿大探索频道）传播研究结果。本科生参与将通过参与两个NSF REU计划（亚拉巴马大学和莫特海洋实验室），重点是涉及代表性不足的群体; REU补充也将寻求涉及额外的代表性不足的本科生。最后，这项研究的结果将被纳入教育推广计划/展览在莫特海洋实验室的鲨鱼由co-PI和麦克韦恩科学中心在伯明翰，AL由PI。仅通过这两个渠道的宣传，每年就应教育70多万人了解鲨鱼皮的减阻特性。

Hueter,0931787 This experimental work will study a new and unique passive boundary-layer separation control methodology derived from shark skin, functioning at the micro-scale level. The skin and denticles (scales) of sharks represent over 400 million years of natural selection for swimming efficiency. Evolutionary adaptations in the morphological structure of the shark skin, to develop unique boundary layer control (BLC) mechanisms, stem from the ensuing decrease in drag, probable increase in fin performance (e.g. thrust production) and enhanced turning agility for fast-swimming sharks. Previous work, confirmed by the PIs, has shown the capability for shark denticles to bristle. The PI discovered that a bristled microgeometry results in the formation of a system of interlocking embedded cavity vortices. Three mechanisms are hypothesized which lead to boundary layer control via deterrence of separation over the shark skin. The first mechanism is the formation of embedded micro-vortices that increase momentum in the very near-wall region due to the partial slip condition resulting on the outer boundary layer flow. The second mechanism is that the preferential flow direction inherent in the surface geometry inhibits global flow reversal. The third mechanism, occurring during transitioning and turbulent boundary layer conditions, involves an exchange of flow with the cavities resulting in turbulence augmentation, or an additional energizing of flow in the near-wall region and cavities. The study involves engineers, working together with biologists, to fully comprehend the morphological bristling mechanism of shark denticles. This study will provide the first comprehensive characterization of the morphological mechanism resulting in denticle bristling and will classify the scope and degree (or angle) of bristling, yielding data for the building of shark skin models for hydrodynamic testing. The three passive BLC mechanisms will be evaluated through flow visualization and measurement using Time-Resolved Digital Particle Image Velocimetry (TR-DPIV). Innovations in the field of BLC are needed to provide efficient methodologies to decrease drag (resulting in increased payload, range or fuel savings), improve performance of control surfaces and enhance turning agility of modern technologies (e.g., submarines, aircraft). Dissemination of results will occur in journals/conference proceedings and the public media (e.g. Discovery Channel Canada). Undergraduate student involvement will take place through participation with two NSF REU programs (University of Alabama and Mote Marine Laboratory) with a focus on involving underrepresented groups; an REU supplement will also be sought to involve additional underrepresented undergraduates. Finally, the results from this research will be incorporated into educational outreach programs/exhibits at the Mote Marine Laboratory on sharks by the co-PIs and at the McWane Science Center in Birmingham, AL by the PI. Outreach through these two outlets alone should educate over 700,000 people each year about the drag-reducing properties of shark skin.