Numerically Analysis Of Muilt-body Oscillating Ocean Energy System

This paper focus on the Multi-body Oscillating Ocean Energy System(MOOES for short).In MOOES,the floater and cylinder heave relatively to absorb the wave energy.Based on this feature,MOOES means the ocean energy converter which has this relatively heaving motion,including heaving type wave energy converter(WEC for short)and some hybrid wind-wave energy systems.In this paper,the numerical model of MHOEC is built to analysis its motion and power performance,the main research contents are as followings:Numerically model the MOOES's motion,considering cylinder's 6 D.O.F motion and floater's relatively heave motion.Based on rigid body assumption,establish the non-linear motion equations.The methodology is programmed using MATLAB,Runge-Kutta method with an adaptive stepsize control is used.Analysis the environmental load of MOOES,including wave load,PTO(Power Take-Off)damping force and mooring load.Different wave force analysis methods are chosen considering the feature difference between cylinder and floater.Based on linear wave theory,Rainey's slendy body theory is used to estimate cylinder's wave load.Froude-Krylov theory is used to estimate floater's wave load.The numierical model is used to analysis the Mushroom WEC's motion and power performance.Validation is carried out based on the existing experimental data.The motion model is used to analysis the couple effect between cylinder's pitch and floater's heave motion.Addtionally,PTO parameter analysis is carried out.The numerical model is used to analysis the STC(Spar-Torus Combination)hybrid wind-wave energy system's motion and power performance.Firstly,the PTO parameter analysis is carried out in Spar-Fixed mode to estimate the best PTO damping coefficient and the effect of PTO on floater's heave motion.Addtionally,PTO parameter analysis is carried out in STC's operational mode,the interaction betwwen spar and floater makes their motions different.