Numerical investigation on effects of damping ratio for flow-induced vibration of tandem cylinders

Abstract

This study numerically investigates the effects of damping ratios on flow-induced vibration (FIV) of two-degree-of-freedom elastically mounted tandem cylinders. By setting the tandem spacing between cylinder centers to four cylinder diameters, the FIV problem was solved using the two-dimensional unsteady Reynolds-averaged Navier–Stokes equations and the shear stress transport k−ω turbulence model. Four typical damping ratios of 0.0036, 0.036, 0.198, and 0.36 are employed to explore the effects of damping ratios on the FIV response. Simulation results show that the peak transverse amplitudes and the fluid force coefficients of cylinders generally decrease with increasing damping ratios. Owing to the presence of lock-in region in the streamwise vibration of the downstream cylinder for ζ=0.36, its streamwise vibration amplitude is larger than those for the damping ratio ζ=0.198 when the reduced velocity Ur≥8. With the increase in damping ratios, trajectories of the downstream cylinder become more regular. It is found that the damping ratio has little impact on the frequency capture phenomenon in the cross-flow direction, while the frequency capture phenomenon is first discovered in the in-line direction, which depends on the damping ratio. A transition in the vortex shedding mode is observed as the damping ratio increases. The increase in damping ratio contributes to the stabilization of energy transfer. It is suggested that damping ratios play a significant role in the FIV responses of tandem cylinders.