Journal of Engineering Research and Reports

In order to solve the harm of vortex-induced vibration (VIV), this paper studies the VIV control performance of multi-type nonlinear energy sink (NES) and tube-in-tube (PIP) structures. The multi-degree-of-freedom NES (MDOF-NES) with low linear stiffness coupling control is the best, and the mass block affects the key characteristics of the limit cycle vibration (LCO), and the performance is better than that of the classical type I NES. Rotary NES (R-NES) has better suppression of large mass ratio cylinders, and the mass ratio and rotation radius improve the performance. The damping parameters need to be designed in combination with the mass ratio of the cylinder. The NES with combined nonlinear damping explicitly emphasizes the influence of the control response condition and the amplitude of the external excitation on the frequency detuning coefficient interval. The vertical vibration control performance of NES with cubic stiffness is related to the natural frequency of the main structure. When the frequency is ≥ 3 Hz, the self-weight can be ignored. When the frequency is ≤ 0.8 Hz, the static vertical displacement of the tuned mass damper (TMD) is greater than that of the TMD. The NES stability emphasizes that the system response is caused by the saddle-node bifurcation of the limit cycle of the coupled system, and two conditions need to be satisfied to strengthen the energy transfer. The optimized PIP structure optimizes the flow field and VIV suppression through three-dimensional fluid-solid coupling and computational fluid dynamics simulation, and has the function of heat preservation, which provides a ' heat preservation + vibration reduction ' scheme for marine engineering. Key conclusions: Low linear stiffness MDOF-NES is suitable for nonlinear energy transfer vibration control, and reasonable parameter PIP is preferred for marine engineering.