Numerical Analysis on Energy Harvesting Effectiveness of Staggered Piezoelectric Flags

Abstract

The numerical study of staggered arrangement of the flags is studied in this work. In this computational model, a piezoelectric flag is placed behind the bluff body as it mimics a fish behind an obstacle. The effect of bluff body on the dynamics of the staggered arrangement of the flag has not been studied yet. In the computational model, the fluid flow equations are solved by using Direct Numerical Simulation (DNS) and the dynamics of the flags is explored using penalty-immersed boundary method. The span- and stream-wise distances are varied and the behavior of the vortex shedding from the downstream flag is investigated at these span- and stream-wise distances. The results show that the in-phase and out-of-phase motion of the flag and constructive-destructive behaviors of the vortices leaving the upstream flag has affected the drag on the downstream flag, which in turns effects the energy harvesting performance of the downstream flag. The voltage generation capability of flag depends on the drag and the induced deformation due to vortex-flag interaction. Numerical Simulations indicate that high energy harvesting efficiency is achieved over a range of stream- and span-wise distances and there is higher value of voltage generation when there is lock in between vortex sheet fluctuations and flag vibration. Large amplitude of oscillations and higher bending of the flag correspond to promising energy harvesting efficiency of the flag. The results show that the voltage generation of the piezoelectric material is increased irrespective of the span-wise distance for specific arrangements.