Hydrodynamic Performance of Conical Shaped Heave Plates

Abstract

Heave plates are commonly employed as an effective and sustainable method to dampen unwanted oscillations of floating offshore structures caused by wave action. Such motion in the case of offshore floating wind turbines (OFWT) can reduce aerodynamic performance and increase fatigue loading. While the performance of flat heave plates is well documented, there is a lack of research assessing plates of conical shape. Thus, in the present study, the performance of conically shaped heave plates is assessed with reference to OFWT. Experiments consisting of forced oscillations of scale models were conducted in a large water tank at a range of frequencies and amplitudes relevant to OFWT. Plate added mass and damping properties were calculated using a frequency independent extension of the Morison equation. Conical plates were found to have improved performance over their flat counterparts. A conical plate of incline angle 56.8° exhibited an improvement on flat plate damping and added mass of approximately 45% and 94% respectively. Increasing conical incline angle was observed to increase plate added mass while having little effect on damping. The extended model's performance was a significant improvement on the standard Morison equation for all amplitudes investigated.