Single-point Mooring Dynamics Analysis And Experimental Study Of Ship-type Cage Under Wave Current

In recent years,due to the rough and rough breeding methods offshore,many sea areas have encountered a series of environmental problems such as water pollution and biodiversity decline.Therefore,the development of marine aquaculture towards the open sea has become a consensus in the industry.To lay offshore cages in open seas,a cage type with a stronger ability to resist wind and waves is needed.In this paper,a new type of anti-wind and wave ship-type cage is studied.Based on the relevant theoretical foundations such as the hydrodynamics of the ship-type cage,the hydrodynamic model of the ship-type cage is established.Using the finite element numerical analysis method and the aid of AQWA software tools,the hydrodynamic characteristics of the ship cage floating system and the mooring system were simulated and analyzed.The reasonable structural design of the ship-type cage floating system is obtained,and the influence relationship of the anchoring system parameters on the movement response of the cage and the maximum anchor rope force is obtained.The analysis results provide guidance for the design of anti-wind and wave performance of ship-type cage.The ship-type cage adopts a ship-shaped floating frame structure and a single-point mooring method,and can rotate downstream along the anchor point.In this paper,the design and optimization of the floating structure of ship-type cage was carried out.The cost coefficient of the cage was proposed,and the orthogonal design theory was used to discuss the influence of the length,width and head angle of the cage floating frame on the inclination angle,maximum wave flow force and cost coefficient of the floating frame.The range analysis method is used to process the calculation results,and the reasonable floating structure of the ship-type cage is obtained.Ship-type cage has complex motion response under the action of waves,and at the same time,a single anchor rope bears a greater load during the breeding process.In this paper,based on the segmentation extrapolation method,the stiffness characteristics of the mooring system under different parameters were analyzed.The equivalent damping coefficient of the mooring system was calculated by the energy dissipation principle.In the time domain,the main influencing factor of the motion response of the cage was studied,and the low-frequency motion response under the influence of different mooring system parameters of the cage was numerically simulated.The influence of series buoys on the hydrodynamic characteristics of the ship-type cage was analyzed.After adding buoys to the mooring system,the changes of the inclination angle of the pontoon,the longitudinal displacement of the pontoon,the wave current force on the pontoon and the anchoring force of the mooring system were analyzed.The trend of the influence of buoy position,size and anchor rope length on the maximum anchor rope force under different wave conditions were further obtained.In order to verify the accuracy of the numerical analysis,this paper designs the physical model of the ship-type cage based on the Froude similarity principle.Using the experimental water tank,the maximum anchor rope force of the ship-type cage anchor system under different parameters of buoy diameter,position and anchor rope length was studied experimentally.The results show that the variation rule of the maximum anchor rope force under the test conditions is consistent with the numerical analysis results.The ship-type cages designed based on the structural parameter optimization and dynamics analysis results of this paper were tested for one year at sea,which demonstrated the safety and stability of the ship-type cages under real sea conditions.