Investigation into the effect of vortex-induced vibrations on the power-output of a pitching cylinder wave energy converter

The aim of the present investigation was to examine the question of whether the introduction of cross-flow vortex-induced vibration (VIV) of point absorber wave energy extraction devices is detrimental or beneficial to power take-off (PTO) efficiency. The dynamic drag amplification experienced by a circular cylinder undergoing cross-flow vortex-induced vibration is well documented for both the steady flow and oscillatory flow cases. The dynamic drag amplification experienced by a cylinder undergoing VIV in a wave environment indicates that there are potential benefits in allowing a drag dominated wave energy device to simultaneously experience cross-flow VIV. Experiments were conducted with a pivoted cylinder wave energy convertor to examine the power output of the system with and without cross-flow VIV over a range of wave amplitudes and frequencies. Near the optimal power take-off damping for the wave energy device, no consiste nt improvement in power take- off was observed with the introduction of VIV motions. A small improvement was noted at PTO damping levels higher than the optimal value