Hydrodynamic Interactions in Vortex Dominated Flows in the Vicinity of Walls

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The world population is expected to reach 10 billion by 2050, heralding an era of increasingly strained resources, including protein to feed the world. Fish, which require far fewer resources to grow than traditional livestock, are a viable protein option that can be harvested from the wild or farmed, a process referred to as aquaculture. As of 2019, the total value of production of aquaculture in Canada is over $1.2B annually and the industry employs over 10,000 people, with growth expected in the future. As this industry expands it becomes critically important to understand the interrelation of stimuli to which fish collectively respond for navigation, feeding, and social interaction to develop more efficient and humane practices and facilities. The long-term goal of the proposed research program is to develop submersible actuators than elicit desired behavioural responses in swimming fish by strategically manipulating the local flow environment. To this end, the five-year research plan proceeds along two themes, with the first focused on thrust enhancement of synthetic jet actuators, and the second on modeling hydrodynamic interactions between model swimmers. Theme 1 looks to exploit the recently discovered "vortex nozzle" effect, wherein the impulse (momentum) of a vortex ring can be passively enhanced by passing it through an appropriately sized aperture. It is hypothesized that the vortex nozzle can be used to enhance the thrust of a synthetic jet (a train of vortex rings ejected from an orifice) without any increase in power input. Thus, we aim to explore the possibility of improving synthetic jet actuator efficiency for future incorporation into engineered aquaculture systems. Theme 2 builds upon recent efforts to model swimming fish as vortex dipoles to explore interactions between animals and their environment. These models have been used to consider the stability of swimming configurations for animal pairs, and to uncover a purely hydrodynamic mechanism by which a single fish in a flow channel can orient itself to swim upstream (called rheotaxis). The preliminary focus of this theme is validating the vortex dipole model using principled numerical simulations of an undulating foil in a channel, then using the simulations to incorporate the effects of a vortex wake, a feature conspicuously missing from current models. The impact of the vortex wake on stable swimming configurations for animal pairs, rheotaxis of a single fish in channel, and the behavior of multiple fish swimming in a flow channel will be explored. Students trained by this program will be armed with a set of unique and complementary skills in engineering and biology that prepares them to join a range of critical Canadian industries, from aquaculture to health science to national defense.