Study on hydrodynamics of a flexible fishlike foil undulating in wall effect

This paper aims to investigate the hydrodynamics of a flexible fishlike foil undulating near the vertical sidewall by using numerical simulation. To achieve the research target of this paper, an immersed boundary-lattice Boltzmann method (IB-LBM) was proposed for high Reynolds number fluid flow simulation. The influences of the clearance (0.2L ≤ d ≤ 0.8L, L is the chord length of the fishlike foil) between the fishlike foil and sidewall, Strouhal number (0.1 ≤ St ≤ 0.5), and wavelength (0.6L ≤ λ ≤ 1.4L) on the hydrodynamic characteristics and power extraction efficiency were studied. The results indicate that the wall effect on forces increase with increasing St and λ, but it is opposite for the power extraction efficiency. As compared to the case of out of wall effect, the fishlike foil swims near the sidewall has an effect of improving thrust and it will reduce or increase the power extraction efficiency in some specified cases. Moreover, an interesting phenomenon with pair arrayed vortices, pair arrayed low-pressure centers and pair arrayed high-velocity centers are observed due to the presence of sidewall.