Research on Shear Mode Bidirectional Piezoelectric Energy Harvesting Structure Based on Underwater Vortex-Induced Vibration

In order to solve the problem of continuous and stable energy supply of underwater sensor nodes, a shear mode bidirectional piezoelectric energy harvesting structure based on underwater vortex-induced vibration is proposed. The structure was investigated through fluid–solid and piezoelectric coupling numerical simulations using ANSYS 2020, and the relationship between the vibration mode, thickness, flow velocity, spacing diameter ratio of the bluff body and energy harvester (L/D) was studied. The vibration and piezoelectric characteristics of parallel and tandem energy harvesters were analyzed. The results verify that the piezoelectric material with d15 mode has higher output power than that with d33 and d31 modes, under the same conditions, the output power has increased by 50%. When the flow velocity is 1.1 m/s, the bluff body is a wavy cylinder, the L/D is 2, and the maximum voltage and output power values generated by the energy harvesting structure are 56.97 V and 3.25 mW, respectively. Its power density reaches 1.35 mW/cm3, superior to similar-scale collectors reported in the recent literature. In the case of the double energy harvesting structure, it can capture vortex-induced vibration energy in both flow and lateral directions, thereby expanding the working bandwidth and improving the overall energy capture efficiency; the parallel output voltage is also the largest. When L/D is 1.5 and the flow velocity is 1.1 m/s, the maximum output voltage values of the upper and lower energy harvesting structures are 78.65 V and 83.05 V, respectively, and the corresponding output power is 6.19 mW and 6.90 mW. The above simulation results verify that the shear mode energy harvesting structure and its array can appropriately increase the open-circuit output voltage of the structure, which provides a new reference scheme for the study of underwater vortex-induced vibration piezoelectric energy harvesting structures.