Hydrodynamic performance and flow control of two flexible bodies in fish schooling-like configuration

Abstract

Swimming in side-by-side configuration is common in the schooling of fish. In this work, the hydrodynamic performance of two flexible plates in side-by-side configuration is modelled and simulated. The simulations are implemented by an in-house parallelized algorithm, which fully coupling the lattice Boltzmann method (LBM) and immersed boundary (IB) mathematically. The Reynolds number scaled by the plate's length and incoming velocity is 200 to 500 in our study, the transverse gap distance is varied from 0 to 5. The results show that the system's coupling motions and hydrodynamics properties are highly depended on the gap distance. Based on the evolutions of wake pattern, the motion modes can be classified as four types, which are single-plate mode, in-phase mode, anti-phase mode and decoupled mode. Also, we find that the drag coefficient for one plate are always equal to another, and the drag reduction is happened when the distance is in the regime corresponding to in-phase mode. This work may help us to develop the novel underwater robots inspired by fish locomotion.