Research on Flow-Induced Vibration and Energy Harvesting of Three Circular Cylinders with Roughness Strips in Tandem

The flow-induced vibration (FIV) of multiple cylinders is a common phenomenon in industry and nature. The FIV and energy harvesting of three circular cylinders in tandem are numerically studied by 2D-URANS simulations in Reynolds number range of 30,000 < Re < 105,000. Simulation results match well with experiments in the tested cases. Four branches of FIV are clearly captured in the amplitude and frequency ratio curves of the three cylinders with roughness, including initial branch of vortex-induced vibration (VIV), VIV upper branch, transition from VIV to galloping, and galloping. It is shown that the vortices from downstream cylinder are strongly disrupted and modified by vortices of upstream cylinder. The third cylinder is almost suppressed in VIV initial branch. The 2P vortex pattern is observed for the first cylinder in the VIV upper branch. For Re = 90,000 in the transition regime, the vortex patterns of the first and second cylinders are 2P + 4S and 2P + 2S, respectively. In the galloping branch, the shear layer motion is in synchronization with the motion of the cylinder, and the maximum amplitude of 2.8 D is reached by the first cylinder. The total converted power of the three cylinders increases with U * water both in the simulation and experiment. For the three cylinders, the maximum power reaches up to 85.26 W with the increase of Reynolds number. The energy conversion efficiency is stable and higher than 35% in the starting region of VIV upper branch, and the maximum value of 40.41% is obtained when Re = 40,000.