Understanding the Coupled Interactions Between Hair-Like Micromechanoreceptors and Wall Turbulence

拟议的研究将侧重于理解湍流与长（高纵横比），柔性毛发状微结构或微柱之间的相互作用，这些微结构或微柱受到自然界中遇到的微柱的启发。一些例子包括鱼的侧线传感器，蝙蝠的气流传感器和海豹和蝙蝠等动物的毛发覆盖物。这些结构执行多种生理功能，例如平衡和平衡传感器、流量传感器、飞行控制传感器、热调节器和水收集器。特别地，毛细胞传感器具有这样的结构，其与动物的神经系统结合形成机械感受装置，即，它们将响应于流动能量的力或位移转化为神经系统的响应。 这些响应于背景流而振动的结构在能量收集系统中也很重要。然而，这些相互作用的理解很少，主要是由于基础物理的复杂性。捕获这种物理特性需要同时组合测量微柱运动和流速，这具有挑战性。拟议的研究将使用先进的基于图像的流动诊断工具来详细测量这些微柱阵列与背景流动之间的相互作用。计划开展的外联活动将针对几乎完全由理科学生人数不足、经济上也处于不利地位的学生组成的群体。支持的研究生将参与外展活动，向下一代工程师灌输外展精神。壁湍流和这些微柱之间的相互作用以以下方式发生。跨越几个数量级的尺度的流动结构，存在于壁湍流内，激发微柱的响应。然后，微柱的偏转或振动响应将反馈并修改非线性背景湍流，从而产生非线性耦合系统。此外，在壁处发生的这种相互作用可以影响整个层，从而导致多尺度相互作用层。特别感兴趣的是微柱和背景湍流之间的能量传递途径。为了描述这种耦合的相互作用和相关的能量传递机制，先进的诊断工具，如多相机，多分辨率，镶嵌粒子图像测速将被用来捕捉动态的背景流，同时跟踪相关的微柱运动，使用粒子跟踪技术。这些工具将共同提供独特的多尺度测量，阐明耦合物理学，推进从生理学到航空航天工程到非线性能源系统的领域。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The proposed research will focus on understanding the interactions between turbulent flows and long (high aspect ratio), flexible hair-like microstructures or micropillars inspired by those encountered in nature. Some examples include lateral line sensors in fish, airflow sensors in bats and hair cover of animals such as seals and bats. These structures perform several physiological functions such as balance and equilibrium sensors, flow sensors, flight control sensors, thermal regulators and water harvesters. Particularly, hair-cell sensors have such structures which in conjunction with the animal's nervous system forms a mechanoreceptive device i.e., they turn a force or displacement, in response to the flow energy, into a nervous system response. These structures that vibrate in response to the background flow are also important in energy harvesting systems. However, these interactions are poorly understood primarily due to the complexity of the underlying physics. Capturing this physics requires simultaneous, combined measurements of the micropillar motion and the flow velocities which are challenging. The proposed research will use advanced image-based flow diagnostic tools to measure in detail the interactions between arrays of these micropillars and the background flow. The planned outreach activities will target a group that is almost exclusively comprised of students who are under-represented in the sciences, while also being economically disadvantaged. The graduate student supported will be involved in outreach activities, inculcating a spirit of outreach into the next generation of engineers.The interactions between wall turbulence and these micropillars occur in the following manner. Flow structures of scales spanning several orders of magnitude, present within wall turbulence, excites the response of the micropillars. The deflection or vibratory response of the micropillars will then feedback and modify the non-linear, background turbulence, resulting in a non-linearly coupled system. In addition, this interaction occurring at the wall can affect the entire layer resulting in a multiscale interacting layer. Of particular interest are energy transfer pathways between the micropillars and the background turbulence. To describe this coupled interaction and the associated energy transfer mechanisms, advanced diagnostic tools such as multi-camera, multi-resolution, mosaicing particle image velocimetry will be used to capture the dynamics of the background flow while simultaneously tracking the motion of relevant micropillars using particle tracking techniques. Together these tools will provide unique multiscale measurements that will elucidate the coupled physics, advancing fields ranging from physiology to aerospace engineering to non-linear energy systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.