Collaborative Research: The leaky rake to solid plate transition on flow through biological filtering structures

许多在流动中游泳、飞行、嗅觉或进食的小生物依赖于分支、刚毛和毛茸茸的结构，这些结构对生物学和生物医学应用具有重要意义。这种刚毛层的运动和方向可以改变空气或水流通过它们的行为，这样它们就可以充当固体板或漏水的耙子。了解动物如何创造性地利用这种类型的流动转换可以为过滤器和采样设备的设计提供信息。虽然这种流动已经在许多系统中进行了研究，但漏耙到固板过渡的预测数学模型仍然不可用。该项目的目标是通过数学建模和实验揭示这种转变背后的物理机制。开发的理论模型可以在生物医学问题中找到应用，例如淋巴和血液通过多孔组织和血管保护层的流动。在教育和拓展方面，学生将通过跨学科课程、实地研究和多学科小组会议，在工程、数学和生物学的界面上进行训练。不同的学生将通过路易斯·斯托克斯少数民族参与联盟（LSAMP）招募。这项研究将阐明在中尺度运行的生物和生物启发过滤阵列的基本流体动力学，其中惯性和粘性力几乎是平衡的。它还将揭示当平流和扩散接近平衡时粒子捕获和交换的基本物理。两种类型的海洋无脊椎动物将被研究：1)倒立的水母，通过3D的刚毛口臂驱动水流；2)海扇，分支成大约2D的片状。由于需要同时解决微米尺度结构周围的小尺度流动和厘米尺度阵列周围的大尺度流动，因此模拟泄漏到固体的转变具有挑战性。新的数学模型，通过实验，将开发描述柔性过滤层的有效孔隙率。粒子捕获率和中尺度过滤阵列周围的浓度分布将在生物和物理模型中进行实验量化。化学交换的进一步细节将采用浸入边界法进行数值解析。在生物学方面，这些生物代表了许多例子中的颗粒捕获和营养吸收发生在中尺度刚毛阵列。揭示这个策略是如何有利的直接贡献给NSF生活规则。在生物启发设计方面，这些系统展示了过滤和交换的固有多尺度解决方案，这将为过滤结构的生物启发设计提供新的见解。该奖项反映了美国国家科学基金会的法定使命，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。

Numerous small organisms that swim, fly, smell, or feed in flow rely on branched, bristled and hairy structures that are significant to biological and biomedical applications. The movement and orientation of such bristled layers can change the behavior of the air or water flow through them such that they may act as either solid plates or leaky rakes. Understanding how animals creatively take advantage of this type of flow transition could inform the design of filters and sampling devices. Although such flows have been studied in many systems, predictive mathematical models of the leaky rake to solid plate transition remain unavailable. The goal of this project is to reveal the physical mechanisms behind this transition through mathematical modeling and experimentation. The theoretical models developed could find applications in biomedical problems such as the flow of lymph and blood through porous tissues and vascular protective layers. In terms of education and outreach, students will be trained at the interface of engineering, mathematics, and biology through interdisciplinary courses, field research, and multidisciplinary group meetings. Diverse students will be recruited through the Louis Stokes Alliance for Minority Participation (LSAMP).This research will elucidate the fundamental fluid dynamics of biological and bioinspired filtering arrays operating at the mesoscale, where inertial and viscous forces are nearly balanced. It will also reveal the fundamental physics of particle capture and exchange when advection and diffusion are nearly balanced. Two types of marine invertebrates will be examined: 1) upside-down jellyfish that drive flow through 3D bristled oral arms, and 2) sea fans that are branched into approximately 2D sheets. Modeling the leaky-to-solid transition is challenging due to the need to simultaneously resolve small-scale flow around micron-scale structures and bulk flow around centimeter-scale arrays. New mathematical models, informed by experiments, will be developed to describe the effective porosity of flexible filtering layers. Particle capture rates and concentration profiles around mesoscale filtering arrays will be quantified experimentally in organisms and physical models. Further details of chemical exchange will be resolved numerically using the immersed boundary method. In terms of biology, these organisms represent one of many examples where particle capture and nutrient uptake occur in mesoscale bristled arrays. Revealing how this strategy is advantageous contributes directly to the NSF Rules of Life. In terms of bioinspired design, these systems exhibit inherently multiscale solutions for filtering and exchange that will provide new insights into the bioinspired design of filtering structures.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.