Bio-inspired locomotion using oscillating elastic plates
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We develop a fluid-structure interaction computational model based on the lattice Boltzmann method and the thin plate model to investigate the impact of different strategies for bio-inspired locomotion with an oscillating elastic plate. We first probe the effects of actuation patterns on the dynamic response of plates with different mechanical and geometrical properties. In particular, we consider the actuation using a distributed internal moment that represents the actuation of piezoelectric smart materials and compare the hydrodynamic performance of such plates with the hydrodynamics of a plunging elastic plate. We then examine the combined plate actuation that integrates plunging using an external actuator with internal piezoelectric actuation. We search for hydrodynamic regimes in which the synergy of two different actuation modes leads to improved thrust production and efficiency. Furthermore we investigate the impact of inhomogeneous mechanical properties through a tapered geometry. We show that the tapered thickness, and ultimately stiffness gradient, can be harnessed to enhance the propulsive performance and efficiency. We link this increased performance to the shift from oscillatory to undulatory regime. We demonstrate that this shift is due to the acoustic black hole effect, a phenomenon where waves are trapped in tapered structures, which allows to maintain travelling waves in the plate. Finally, we explore this vast parameter space through a multi-objective optimization procedure based on a genetic algorithm to highlight key futures of tapered designs to maximize the swimming performance.