Research On The Motion Response Of Small Buoys Under The Action Of Waves

Small size and low cost are the characteristics of small buoys,so they are widely used in national economic,social development and defense security.However,small buoys always generate movement induced by waves,such as surge,sway,heave,pitch、roll and yaw.Heave and pitch have the greatest affect on the normal work of buoys.These two types of motions are coupled with each other.At present,there are few studies on the coupled motion of small buoys.Therefore,it is significance to study the motion of small buoys induced by waves.This study uses cylindrical buoy as the research object,studied the mechanism about motion of buoy induced by waves.Established simulation methods about motion response of buoy based on different theories,and studied the pattern about motion response of buoy induced by waves.The work of this study is as follows:Based on the improved Morison formula and the dynamics model,the fluid forces of buoys and a mathematical model of the buoys heave-pitch coupling motions induced by waves were studied in depth.And then,a set simulation program of buoy motion was developed based on MATLAB.Based on the RANS method and the VOF model,two kinds of numerical wave sink based on different calculation domain were established.The accuracy of numerical wave effected by different methods was studied.Waveform created by this numerical wave sink and theoretical waveform are analyzed in different physical time.The results show that computational domain processing method based on potential-viscous flow has higher precision and better robustness.And then,using 6DOF model and overlap grid technology,a simulation method of buoy motion based on numerical wave sink was establishedAgainst the same typical model,based on the experimental data,two kinds of simulation methods were compared and researched.The results show that both methods can effectively predict the motion response of the buoy induced by waves.The simulation method based on the potential flow theory has a high prediction accuracy for heave motion,a correct trend of the prediction for pitch motion but a low prediction accuracy for pitch motion.The advantage of this method is that it requires less computing resources,so it can be used to preliminary design for the program;The simulation method based on numerical wave sink has high precision accuracy for heave motion and pitch motion,but it requires large computational resources.The advantage of this method is that it has high prediction accuracy and can guide the fine design of buoys.Finally,using the simulation method based on the numerical wave sink,the influence of the distance of gravity center and floating center,the shape of the bladder,and the sea level for heave and pitch motion of cylindrical buoy was studied.It has guiding significance for designing of cylindrical buoys.