Flow around a Wingmill device for energy extraction

Abstract

The dynamics of a closed loop self controlled underwater oscillating foil device for energy extraction (a wingmill) is studied through numerical simulations. The viscous two and three dimensional flow around the foil was computed using OpenFOAM and a Lattice-Boltzmann Equation model, respectively. Heaving is driven by the computed hydrodynamic lift and a damper, that extracts energy, while pitching is driven by the hydrodynamic torque and a feedback control torque that leads the foil to a given angle of attack. Unlike most of the related work found in the literature, the heaving and pitching motion of the foil is not prescribed. Dimensional analysis suggests a compromise between the generator and control gains, so a parametric study was carried out. The effect of a three dimensional finite wingspan on the performance of the device, and the flow is compared with the two dimensional case. This fully coupled fluid-solid-body interaction configuration will allow for the system identification, control and optimization of energy harvesting devices in future studies.