Numerical study on a novel flapping-foil energy harvester with 2D vortex generator

This research presents a passive control energy capture device with two-dimensional (2D) vortex generator on the surface of flapping foil. When Reynolds number equals to 13800, based on the dynamic grid technique, the effects of the key parameters such as the position size as well as shape of 2D vortex generator on the efficiency of flapping foil are simulated, and the results are showed as following: (1) Compared with the original flapping foil, the passive control flapping foil with 2D vortex generator not only can effectively increase the energy exchange of boundary layer on the surface of flapping foil, but also can increase the force consistent with the direction of flapping foil movement and the pressure difference between the pressure surface and the suction surface, so as to improve the energy harvesting efficiency of the flapping foil. (2) The 2D vortex generator with triangle shape at 30% of chord length has an optimal size, which can improve the energy efficiency of the flapping foil energy harvesting device by 6.2% compared with the original (ORI) model. (3) The 2D vortex generator designed in this research does not generate new vortex, while only interfering with the vortex generated at the leading edge of the airfoil, so as to realize the function similar to the traditional vortex generator. The results of this research are of great significance to improve the design of flapping foil, and can provide some guidance for engineering practice.