Influence of lateral distance and phase difference on energy absorption performance of undulating airfoils in a side-by-side arrangement

It is recognized that traveling wave motion can extract energy from moving water or wind under certain motion parameters. The NACA0012 airfoil section is used as a two-dimensional simplified model of the fishlike body in this paper. We numerically investigated the influence of lateral distance and phase difference on energy absorption performance of two undulating airfoils in a side-by-side arrangement. The findings show that: within a certain range, the energy absorption efficiency of the side-by-side undulating airfoils is higher than the data of a single airfoil. When the phase difference is 0°, the energy absorption efficiency of undulating airfoils increases first and then decreases with the increasing lateral distance, existing a maximum efficiency. When the lateral distance is constant, as the phase difference varies, the curve of absorption efficiency almost takes on an antisymmetric form with the period of 360°. As the phase difference increases, one of the airfoil's efficiency decreases first, then increases and finally decreases, while the other one's efficiency increases first, then decreases and finally increases.