Critical roles of mass, spring, and damping ratios in nonlinear energy sink vortex-induced vibrational control: CFD & optimization

Vortex-induced vibration (VIV) poses significant challenges in engineering. Structures subjected to fluid flows necessitate effective suppression mechanisms to avoid vibrations. This study investigates the ability of a nonlinear energy sink (NES) system to reduce VIV under a variety of reduced velocities (Ur). Over 3,000 scenarios were examined to assess the impact of NES properties; mass ratio (β=0.01−0.5), spring ratio (γ=0.01−2.0), and damping ratio (ξ=0.01−2.0) on the vibrational response of structures using computational fluid dynamics (CFD) simulations utilizing Reynolds-averaged Navier–Stokes (RANS) turbulence models. The numerical simulations were validated using experimental data demonstrating excellent agreement with the literature. Vibrational contour maps were developed from the CFD predictions over a wide range of Ur,β,γ,andξ. Our findings indicate that the process of tuning the NES parameters (β, γ, and ξ) can either diminish vibrational amplitudes (Ay/D), or if not carefully optimized, can amplify them. With optimal NES parameter tuning, an amplitude reduction of 94% was found to be possible. Furthermore, Sobol sensitivity analysis was performed, which revealed that while Ay/D highly depends on Ur, proper tuning of the β in combination with γ is critical, especially in regimes where parameter interactions become significant. While global optimization is challenging, it is recommended that the optimized NES parameters for the lock-in region differ from those for the lower-branch vibration region.