Numerical investigation into power extraction by a fully passive oscillating foil with double generators

Abstract

Abstract A new concept of energy conversion system based on fully passive oscillating foil with double generators to extract energy from pitching and swing motions respectively is proposed and numerically tested. The shedding vortices in the wake drive a C-shape foil to pitch around a pivoting axis, and the resulting periodic lift force drives the foil to swing around an arm. Two-dimensional incompressible Navier-Stokes simulations under Re from 1100 to 11000 are carried out to study the fluid-foil interaction. The effects of pitching damping factor, swing damping factor and incoming flow speed are systematically studied. Numerical results demonstrate that the use of pitching generator not only provides extra pitching power, but also improves the swing power. It is also found that the maximum power coefficient and efficiency increase with flow speed slightly in the laminar flow region, but the influence of Re is very limited. The analysis of the correlation between pitching and swing motions shows that the energy conversion system possesses the possibility of connecting pitching motion with swing motion and further simplifying the system.