Revealing the effects of damping on the flow-induced vibration of flexible cylinders

Abstract

This study reveals how damping shapes the global vortex-induced vibration (VIV) response of flexible cylinders. Global behavior may vary from full-length standing waves to traveling waves on infinite cylinders. Structural damping rules the standing wave case whereas radiation damping regulates VIV response on very long cylinders. A single scalar equation expresses the balance of power flowing through the structure. In that equation, Arms, which is the root-mean-square response in the VIV excitation region, is shown to be an excellent indicator of global response because of its relation to power flow. Under steady-state conditions, the net power flow must be zero, which directly leads to three independent dimensionless damping parameters, namely α,βR,andc*. βR indicates when radiation damping is important, α reveals the relative importance of structural versus radiation damping, and c∗ locates the global VIV behavior on the spectrum of lightly to strongly damped systems. Structural, hydrodynamic, and wave radiation damping are all taken into account. Plots of Arms∗ versus c∗ show the global effects of damping on response. Uncontrolled factors often reveal themselves as graphical anomalies, leading to new insights on VIV. Data from experiments and numerical simulations are presented to support the conclusions. Keywords: Radiation damping; flow-induced vibration; impedance; wave propagation