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

许多在水流中游泳、飞行、嗅觉或进食的小生物都依赖于对生物学和生物医学应用具有重要意义的分支、刚毛和多毛结构。这种刷毛层的运动和取向可以改变通过它们的空气或水流的行为，使得它们可以充当实心板或泄漏耙。了解动物如何创造性地利用这种类型的流动过渡可以为过滤器和采样装置的设计提供信息。虽然在许多系统中已经研究了这种流动，但是仍然没有泄漏耙到固体板过渡的预测数学模型。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。在教育和推广方面，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，数学和生物学的接口进行培训。将通过路易斯·斯托克斯少数民族参与联盟（LSAMP）招募不同的学生。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，惯性力和粘性力几乎平衡。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学。两种类型的海洋无脊椎动物将被检查：1）倒置的水母，通过3D刚毛口臂驱动流动，和2）海扇，分支成大约2D片。由于需要同时解决微米级结构周围的小规模流动和厘米级阵列周围的大规模流动，因此对泄漏到固体过渡进行建模具有挑战性。新的数学模型，通知实验，将开发来描述灵活的过滤层的有效孔隙度。将在生物体和物理模型中通过实验对中尺度过滤阵列周围的颗粒捕获率和浓度分布进行量化。化学交换的进一步细节将用浸入边界法在数值上解决。在生物学方面，这些生物体代表了在中尺度刚毛阵列中发生颗粒捕获和营养吸收的许多例子之一。揭示这种策略是如何有利的直接有助于NSF的生活规则。在生物启发设计方面，这些系统展现了过滤和交换的内在多尺度解决方案，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。

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.