Numerical study on energy harvesting from flow-induced vibrations of dual-interfering-cylinders in ocean currents

Ocean energy resources have abundant reserves and play an important role in addressing energy crises. The study simulated flow-induced vibration energy harvesting in an isosceles triangular structure composed of upstream fixed dual interfering cylinders and a downstream single-degree-of-freedom vibrating energy-harvesting cylinder, revealing that the presence of upstream interfering cylinders enhances marine energy capture. With the Reynolds number and spacing ratio fixed at 150 and L/D = 2, respectively, numerical simulations were performed for cases with different diameter ratios (D* = 1.0, 0.8, and 0.6), and wake visualization analysis was employed to illustrate the influence of vortex structures on structural vibrations. Parallel numerical analyses of a single energy-harvesting cylinder configuration were conducted to highlight the advantages of the dual interfering cylinder configuration in wake-excited energy harvesting. The results demonstrated that, under the wake excitation effects of the dual interfering cylinders, the dual interfering configuration exhibited significantly stronger flow-induced vibration energy-harvesting responses compared to the single energy-harvesting configuration, along with maintaining higher dimensionless amplitudes at elevated reduced velocities. Regarding energy harvesting performance, the dual interfering configuration showed high sensitivity-to-diameter ratio variations: The D* = 0.6 case achieved optimal energy-harvesting power and efficiency at reduced velocity (Ur) < 7, while at Ur > 7, the optimal diameter ratio shifted, with the D* = 1.0 configuration demonstrating superior capabilities. This research elucidates the influence mechanisms between multi-bluff-body wake-excited energy harvesting and diameter ratios, emphasizing the advantages of wake excitation in flow-induced vibration energy harvesting and establishes a technical foundation for the design of renewable marine energy harvesting devices based on multi-bluff-body wake excitation.