Numerical Study For Hydrodynamic Performance Of Inner Pendulum Wave Energy Converter

Ocean wave energy utilization technology has made considerable progress in the last half century. Extensive research has been carried out all over the world. Ideas of multiple forms of wave energy conversion device has been proposed, some test equipment have been manufactured, and several of them have been put into commercial production.The inner pendulum wave energy converter, which was presented by the paper, is a device which utilize the relative motion under wave action between the inner pendulum and the external floating body to push the hydraulic pump which can drive the generator to produce electricity.The main advantage of this new form of wave energy conversion device are:good adaptation of varied environmente, relatively low cost and high durability. Studies abroad are still mainly focused on numerical and laboratoray analysis. Further studis about this form of wave energy converter are urgent.Force analysis and motion analysis of the internal pendulum wave energy converter were first taken into consideration. The effect of wave action was based on the potential flow theory, and then equations of motion in both frequency domain and time domain of the WEC were established to calculated its response of motion, which are the foundations of the calculating of driving force, driving torques, output power and wave energy capture efficiency. The objectives of this thesis are as follows:(l)First, consider the effects of three critic parameters, which means the internal hydraulic damping, the internal hydraulic stiffness and the horizontal stiffness of the external floating body. Roughly determine the values of these three parameters.(2)The influences of the ratio between the external floating body mass and the internal pendulum mass, the ratio between the upper ball mass and the lower ball mass of the internal pendulum, the distance between the connection point and the centroid of the external floating body, the distance between the connection point and the centroid of lower ball are investigated systematically based on the equations of motion in frequency domain.(3)The influences of the nonlinear mass matrix and the nonlinear additional forces are calculated by the equations of motion in time domain, which supports a more accurate results of the hydrodynamic charateristics of WEC.