Abstract
The fluid-structure interaction problems of two side-by-side flexible plates with a finite aspect ratio in a three-dimensional (3D) uniform flow are numerically studied. The plates’ motions are entirely passive under the force of surrounding fluid. By changing the aspect ratio and transverse distance, the coupling motions, drag force and energy capture performance are analyzed. The mechanisms underlying the plates’ motion and flow characteristics are discussed systematically. The adopted algorithm is verified and validated by the simulation of flow past a square flexible plate. The results show that the plate’s passive flapping behavior contains transverse and spanwise deformation, and the flapping amplitude is proportional to the aspect ratio. In the side-by-side configuration, three distinct coupling modes of the plates’ motion are identified, including single-plate mode, symmetrical flapping mode and decoupled mode. The plate with a lower aspect ratio may suffer less drag force and capture less bending energy than in the isolated situation. The optimized selection for obtaining higher energy conversion efficiency is the plate flapping in single-plate mode, especially the plate with a higher aspect ratio. The findings of this work provide several new physical insights into the understanding of fish schooling and are expected to inspire the developments of underwater robots or energy harvesters.
Highlights
Interactions between flexible structures and viscous flow are ubiquitous and familiar in nature and engineering applications
To solve the passive deformation of the flexible body, a finite element method based on a triangular mesh [38,39] is adopted. To validate this coupled algorithm, the dynamics of flow past a square flexible plate were simulated at low Reynolds number
The maximum lift coefficient is obviously higher than the mean drag coefficient, and the difference between them increases with the increasing aspect ratio
Summary
Interactions between flexible structures and viscous flow are ubiquitous and familiar in nature and engineering applications. The flexibility of the structure plays an important role to improve its body stability or propulsion performance in surrounding flow. Through its passive shape reconfiguration in the flow, a tree leaf can achieve substantial and beneficial drag reduction [1,2]. A fish can exploit energy from the surrounding vortex street and achieve cost savings by undulating its body [3,4,5]. A dead fish was observed to propel upstream when its flexible body resonated with the wake of a bluff cylinder [7]; this entirely passive locomotion without energy input was found in a simple articulated fish-like system [8]
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