Energy harvesting simulation of two piezoelectric flags in tandem arrangement in the uniform flow

At present, energy harvesting from the widely existing fluid in the environment is a hot research field. Piezoelectric flags can be used to generate electric energy with the flow excitation for its positive piezoelectric effect. In this paper, the energy harvesting capacity of two piezoelectric flags in tandem arrangement in the uniform flow is analyzed through 2D numerical simulation. Identical vibration frequency and larger vibration amplitude of the downstream flag are found compared with that of the upstream one. Two coupling modes including the in-phase mode and the out-phase mode are identified. The in-phase mode and out-phase mode can be obtained respectively by arranging the distance of two piezoelectric flags at an odd multiples and an even multiples of adjacent vortexes distance. There are 0 phase difference in in-phase mode and π phase difference in out-phase mode of the vibration as well as the output electric current of two flags. Output power of the downstream piezoelectric flag is larger than that of upstream flag and increases with the separation distance until the maximum energy harvesting capacity of piezoelectric flag. The fixed phase difference of coupled two flags and higher power output of downstream piezoelectric flag indicate that reasonable arrangement of multi-piezoelectric flags in tandem arrangement offers an easier approach to collect the obtained electric energy with post-processing circuit of coupled piezoelectric flags, and higher power can be obtained.