Numerical investigation into the effects of motion parameters on energy extraction of the parallel foils

Due to the deficiency of the research on parallel foils, the parallel configuration of foils is concerned and the effects of motion parameters on energy extraction are systematically discussed in the present study. The foils undergo combined plunging and pitching motions. The effects of motion parameters (pitching amplitude, plunging amplitude, reduced frequency, and spacing between foils) in wide range are investigated at Re=1100 through two-dimensional (2D) unsteady laminar flow simulations. The features of power output and efficiency changing with these motion parameters as well as the evolution of the vortex fields are gained. The principle that how motion parameters affecting energy extraction performance is studied. The extraction performance of parallel foils and single foil is compared at the optimal working parameters of the single foil. Numerical results indicate the optimal extraction performance of the parallel foils is superior to that of the single foil. C _Pm improves by 6.87% relatively. Therefore, it reveals that the parallel foils can perform the better extraction characteristics than the single foil by controlling parameters.