Fluid Dynamics of Crossflow Filtration in Suspension-Feeding Fishes

本计画将探讨以悬浮液喂食之鱼类，如鲱鱼、鱼、鲤鱼等之错流过滤之流体动力学。 这些鱼过滤大量的水，以提取直径小至5微米至1毫米的悬浮食物颗粒。 虽然它们占世界鱼类捕获量的约25%，并且过滤效率接近工业过滤器，但它们用于捕获微小猎物的机制仍然很大程度上未知。 一个微型光纤内窥镜最近已被用来观察悬浮液喂养的鱼类口腔内的颗粒运动。 这些数据，结合鱼类口腔中的计算流体动力学模拟，导致了一个新的模型，涉及在悬浮液喂养的鱼类横流过滤的发展。 尽管错流过滤是用于制造我们每天使用的产品（例如，乳制品、啤酒和葡萄酒、药物），这种过滤机制以前在任何脊椎动物中都没有被认识到。 在鱼类的错流过滤过程中，当滤液从鳃耙之间排出时，颗粒物集中在口腔内，但颗粒物不会保留在鳃耙上。 相反，沿着耙状物的高速横流沿着将颗粒从耙状物表面带走并将颗粒朝向食道输送。 工业过滤工程文献中的方程可用于计算在鱼类错流过滤过程中颗粒上的水动力以及由此产生的颗粒速度和轨迹。 然而，必须使用适合悬浮液喂养鱼类的值来代替方程中的变量。 生物交叉流过滤的第一次定量分析所需的经验数据将由实验室实验提供，包括声显微测量、压力转换、光纤内窥镜、高速视频和微热敏电阻探头流速测量。 这项分析将提供深入了解的过程中，横流过滤，因为它决定了悬浮液喂养的鱼类保留的颗粒的大小和密度。 该研究将使本科生和硕士生参与具有重要生态，进化和工程意义的跨学科研究。

This project will investigate the fluid dynamics of crossflow filtration in suspension-feeding fishes such as menhaden, anchovy, and carp. These fishes filter massive volumes of water to extract suspended food particles that are as small as 5 micrometer to 1 mm in diameter. Although they comprise approximately 25% of the world fish catch and have filtration efficiencies approaching those of industrial filters, the mechanisms that they use to trap their tiny prey remain largely unknown. A miniature fiberoptic endoscope has been used recently to observe particle movement inside the oral cavities of live suspension-feeding fishes. These data, combined with computational fluid dynamics simulations in fish oral cavities, have led to the development of a new model involving crossflow filtration in suspension-feeding fishes. Although crossflow filtration is a multi-billion dollar industry for the manufacture of products that we use every day (e.g., dairy products, beer and wine, pharmaceuticals), this filtration mechanism had not been recognized previously in any vertebrate. During crossflow filtration in fishes, particles are concentrated inside the oral cavity as filtrate exits between the gill rakers, but particles are not retained on the rakers. Instead, the high-velocity crossflow along the rakers carries particles away from the raker surfaces and transports the particles towards the esophagus. Equations from the industrial filtration engineering literature could be used to calculate the hydrodynamic forces on particles and the resulting particle velocities and trajectories during crossflow filtration in fishes. However, values that are appropriate for suspension-feeding fishes must be used in place of the variables in the equations. The empirical data needed for the first quantitative analysis of biological crossflow filtration will be provided by laboratory experiments involving sonomicrometry, pressure transduction, fiberoptic endoscopy, high-speed video, and flow velocity measurement with micro-thermistor probes. This analysis will provide insight into the process of crossflow filtration as it determines the sizes and densities of particles that suspension-feeding fishes retain. The study will engage undergraduate and Masters students in interdisciplinary research that has important ecological, evolutionary, and engineering implications.