Study On The Hydrodynamic Characteristics Of Typical Floating Cages

Due to the increasing popularity of marine development,floating cages are widely used in the aquaculture industry.But in the ocean with complex and changeable environment,floating cages will be affected by different loads.The analysis of the load on the floating cage plays an important role in the safety of its work and directly affects the income of fishery.In order to determine the deformation and changes when the floating cage is moored under different environmental conditions,this dissertation takes the floating cage model as the research object,and uses the equivalent mesh method to reduce the number of units in the floating cage model.The concentrated mass method simplifies the flexible member model,and carries out numerical simulation through Morison formula and differential equation of motion.Taking different environmental parameters as the research object,the floating cage and its mooring system are in current only,regular wave only,and wave-current coupling.Carry out the following research in aspects such as role.Based on the above-mentioned equivalent theory,this dissertation uses Orcaflex to establish calculation models with different equivalent accuracy.Through time domain analysis,the calculation accuracy of different models is compared and analyzed from two aspects of mooring force and cage deformation.The results show that as the length of the equivalent mesh element decreases,the number of elements increases,the calculation time increases,and the calculation accuracy gradually increases.The equivalent model with a relatively moderate number of elements is comprehensively considered.By calculating the degree of improvement of the mesh deformation of each cage under different current velocity under different counterweights,the weight of the counterweight suitable for the following calculations is determined.Through time domain analysis,the influence of different current velocity and directions is studied.The structure shows that as the current velocity increases,the internal tension of different mooring systems changes significantly,the maximum tension increases with the increase of current velocity,and the maximum tension is at 0°.The extreme value occurs in the upstream mooring system of current.At the same time,the change of the tension extreme value with the change of the current direction is determined.The results of the tension extreme values corresponding to each λ/D under different wave steepness under the action of the regular wave show that the phenomenon of "resonance" occurs when λ and D have a certain relationship.When δ=1/30 and δ=1/60 under wavelet steepness,the change is relatively small,while under large wavelet steepness δ=1/15,the extreme value of tension changes significantly.Comparing the influence of different wave directions,it is found that the amplitude of the tension gradually decreases with the increase of the angle.By carrying out time-domain calculations under regular wave-current coupling,the results show that the coupling effect of large wave steepness δ =1/15 has a greater impact on the overall tension,and the maximum numerical difference reaches24.1%.The hydrodynamic situation of the single cage mooring in the working environment is analyzed,and the working environment is simulated by the coupling of irregular wave and current.The tension changes under different wave and current angles are determined.Statistical analysis is made that the mooring system with the extreme tension value is the 1#mooring system,and the single rope failure analysis of the different ropes in the mooring system shows that the single rope failure of the 1#-1 rope makes the 1# mooring system completely invalid,and the 1# mooring system The tension of the system and the 3# mooring system suddenly became 0k N,while the tension in the mooring systems on both sides increased significantly;and the failure of the single rope of the 1#-2 rope and the 1#-3 rope wouldn’t cause the 1# mooring system to be completely failure,but due to the effect of the deformation of the overall mesh,the tension becomes smaller.Through the analysis of the numerical simulation results in this dissertation,the influence of different environmental parameters on the hydrodynamic performance of floating cages and their mooring systems is determined,which provides a certain reference for floating cages to carry out deep-sea aquaculture in different environments.