Submersible buoy systems are widely used for oceanographic research,ocean engineering and coastal defense.Severe sea environment has obvious effects on the dynamics of submersible buoy systems.Huge tension can occur and may cause the snap of cables,especially during the deployment period.This paper studies the deployment dynamics of submersible buoy systems with numerical and experimental methods.By applying the lumped mass approach,a three-dimensional multi-body model of submersible buoy system is developed considering the hydrodynamic force,tension force and impact force between components of submersible buoy system and seabed.Numerical integration method is used to solve the differential equations.The simulation output includes tension force,trajectory,profile and dropping location and impact force of submersible buoys.In addition,the deployment experiment of a simplified submersible buoy model was carried out.The profile and different nodes' velocities of the submersible buoy are obtained.By comparing the results of the two methods,it is found that the numerical model well simulates the actual process and conditions of the experiment.The simulation results agree well with the results of the experiment such as gravity anchor's location and velocities of different nodes of the submersible buoy.The study results will help to understand the conditions of submersible buoy's deployment,operation and recovery,and can be used to guide the design and optimization of the system.
Deployment of buoy systems is one of the most important procedures for the operation of buoy system.In the present study,a single-point mooring buoy system which contains surface buoy,cable segments with components,anchor and so on is modeled by applying multi-body dynamics method.The motion equations are developed in discrete node description and fully Cartesian coordinates.Then numerical method is used to solve the ordinary differential equations and dynamics simulations are achieved while anchor is casting from board.The trajectories and velocities of different nodes without current and with current in buoy system are obtained.The transient tension force of each part of the cable is analyzed in the process of deployment.Numerical results indicate that the transient payload increases to a peak value when the anchor is touching the seabed and the maximum tension force will vary with different floating configuration.This work is helpful for design and deployment planning of buoy system.
Marine mobile buoy(MMB) have many potential applications in the maritime industry and ocean science.Great progress has been made,however the technology in this area is far from maturity in theory and faced with many difficulties in application.A dynamic model of the propulsion mechanism is very necessary for optimizing the parameters of the MMB,especially with consideration of hydrodynamic force.The principle of wave-driven propulsion mechanism is briefly introduced.To set a theory foundation for study on the MMB,a dynamic model of the propulsion mechanism of the MMB is obtained.The responses of the motion of the platform and the hydrofoil are obtained by using a numerical integration method to solve the ordinary differential equations.A simplified form of the motion equations is reached by omitting terms with high order small values.The relationship among the heave motion of the buoy,stiffness of the elastic components,and the forward speed can be obtained by using these simplified equations.The dynamic analysis show the following:The angle of displacement of foil is fairly small with the biggest value around 0.3 rad;The speed of mobile buoy and the angle of hydrofoil increased gradually with the increase of heave motion of buoy;The relationship among heaven motion,stiffness and attack angle is that heave motion leads to the angle change of foil whereas the item of speed or push function is determined by vertical velocity and angle,therefore,the heave motion and stiffness can affect the motion of buoy significantly if the size of hydrofoil is kept constant.The proposed model is provided to optimize the parameters of the MMB and a foundation is laid for improving the performance of the MMB.
