Study on the hydrodynamic aggregation of parallel self-propelled flexible plates based on a loosely coupled partitioned algorithm

Abstract

Mechanism of hydrodynamic aggregation of swimmers is an intriguing problem, which is usually studied by the immersed boundary (IB) method. In this paper, a loosely coupled partitioned algorithm is used to simulate this fluid-structure interaction (FSI) problem. Specifically, flow field is simulated by finite volume method, and structure field is approximated by solving the momentum equation and bending vibration equation of Euler-Bernoulli beam. First of all, this algorithm is validated through simulating collective behavior of two actively moving two-dimensional (2D) flexible plates in tandem configuration driven by the harmonic plunging motions of their leading edges with identical frequency and amplitude. Then, the hydrodynamic aggregations of multiple (two or three) 2D flexible plates in side-by-side configuration are studied. It is found that two different stable configurations (alternate-leading mode, AL and staggered-following mode, SF) are formed spontaneously in two parallel flexible plates, and are determined by the lateral spacing between them. In three parallel-plates scenario, the middle plate follows behind in SF mode, while the other two plates present AL and SF modes with different lateral spacings accordingly. Besides, the flow details in different configurations are illustrated and the corresponding propulsive properties (velocity, input power and efficiency) of plates are discussed.