Mantas and devil rays are large fishes that feed by engulfing massive volumes of seawater, extracting plankton with a specialized filter structure, and expelling filtered water through the gill slits. These animals utilize a highly-efficient filtration mechanism, ricochet separation, that is distinct from previously-described biological or industrial filtration processes. This project will use a multidisciplinary approach to examine the fluid dynamics and filtration mechanics of this unique system. This project will characterize the anatomy of the filtering structure, identify how the shape of the structure affects the flow around the filter, and determine how the resulting flow patterns affect particle filtration. This work will provide critical insights into the physiology of an ecologically important and threatened group of animals. In addition, there is substantial need for improved filtering strategies for use in applications ranging from mitigating large-scale environmental contamination events to routine wastewater treatment. This project will elucidate the mechanics of a novel and highly-efficient filtration process, and has considerable potential to lead to advanced, bioinspired filtration systems. This research will also provide valuable training for undergraduate, graduate, and post-doctoral scientists and support activities to engage school-aged students and expose them to biomechanics and bioinspired engineering.
The filtering apparatus of mobulid fishes (mantas and devil rays) is a highly-specialized gill-raker structure. It has long been believed that the raker functioned as a sieve filter, simply trapping particles larger than the pore size. However, recent work has shown that the raker utilizes a unique filtration mechanism, ricochet separation, in which complex flow fields cause plankton particles to recoil off the filter surfaces and become concentrated within the buccal cavity. This filtration process has several favorable properties including that it efficiently separates particles smaller than the pore size, is highly resistant to clogging, and has low hydrodynamic resistance. This project will examine the fluid dynamic processes underlying this mechanism and the morphological factors that influence its performance. This research uses a multipronged approach that includes anatomical studies (micro computed tomography), experimental fluid mechanics (particle image velocimetry and filtration efficiency measurements), and theoretical modeling (computational fluid dynamics). Aim 1 will investigate the small-scale physical processes at the surface of the filter, identifying how individual plankton particles interact with the filter and how this interaction is affected by the morphology of the filter. Aim 2 will examine the large-scale flow patterns that develop in the mouth and will determine how this flow influences the filtration mechanics. Aim 3 will use an understanding of these processes to create and optimize bio-inspired engineered filtration 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.
