Energy Harvesting From Vortical Flows by a Passive Heaving Foil

This paper studies energy harvesting of a two-dimensional foil in the wake downstream of a cylinder. The airfoil is passively mobile in the transverse direction. An immersed-boundary method with a fluid-structure interaction model is validated and employed to carry out the numerical simulation. For improving the numerical stability, a modified low-storage 3rd-order Runge-Kutta scheme is implemented for time integration. The performance of this temporal scheme on reducing spurious pressure oscillations of the immersed-boundary method is demonstrated. The simulation shows a foil emerged in a vortical wake achieves better energy harvesting performance than that in a uniform flow. The types of dynamic response for the energy harvester are identified and the properties of vortical wakes are found to be of pivotal importance in obtaining the desired periodic response of the foil.