Vortex-induced vibration characteristics of rigidly connected four-cylinder system and nonlinear energy sinks for vibration suppression

In order to study the vortex-induced vibration (VIV) characteristics of rigidly connected four-cylinder systems and the suppression of vortex-induced vibration by nonlinear energy sinks (NESs), a fluid–structure coupling dynamic simulation model of a two-degree-of-freedom rigidly connected four-cylinder system is established based on computational fluid dynamics, structural dynamics, and overset mesh technology. The accuracy of the numerical model established in this paper is verified by comparing with the experimental data of literatures. The results show that the dimensionless vertical amplitude of the four-cylinder system decreases with increase in the inflow angle, the reduced velocity advance of the maximum vertical amplitude moves forward and the frequency “lock-in” interval is shortened. Among them, the maximum amplitude at Ur=7 is 0.75 when the inflow angle is 0°, and the maximum amplitude is 0.54 at Ur=6.5 when the inflow angle is 45°. The corresponding frequency “lock-in” interval ranges from Ur=4.5–7 change to Ur=5–6.5. The NES can absorb the cylinder vibration energy, and when the NES parameter β=0.1,ξ=0.8,γ=0.8, the maximum vertical of the four-cylinder system with inflow angle of 0° can be reduced by 76%.