Dynamic energy harvesting performance of two Polyvinylidene Fluoride piezoelectric flags in parallel arrangement in an axial flow

The dynamic performance and output power of two piezoelectric flags are greatly different from those of a single piezoelectric flag due to the coupling effect of each other. In this paper, the dynamic performance and energy harvesting ability of two piezoelectric flags in parallel arrangement in an axial flow are investigated using immersed boundary-lattice Boltzmann method coupled with Euler-Bernoulli beam and piezoelectric theory, which is fully coupled fluid-structure-electric. A 2D simulation model is presented and a resistance is connected to the piezoelectric flag which is made of Polyvinylidene Fluoride (PVDF). The simulation results show that different vibration phases and coupling modes of two piezoelectric flags are identified, including the in-phase mode, the transition mode and the out-phase mode. When the separation distance of two flags is small, the vibration appears to be the in-phase coupling mode. While the separation distance is large enough, two piezoelectric flags decouple and vibrate individually. Between the in-phase mode and the out-phase mode, the transition mode is found. There is strong interference between each other and the output electric energy seems to be disorders. However, the output power of the piezoelectric flags is nearly identical during the in-phase and the out-phase mode. It means that multi-piezoelectric flags can generate multiple times electric energy in reasonable arrangement compared with a single piezoelectric flag.