| Freeboard net is one of the main fishing methods of saury.Its fishing operation is mainly divided into three steps: Net releasing,net luring and net lifting.Saury is an oceanic migratory fish with fast speed and agile action.In the process of Baling net operation,it is often because the floating rod can not reach the designated area in time,resulting in insufficient settlement depth in the middle of the net clothes,which reduces the space volume of the light inducement area.Therefore,the propulsion speed of the dynamic floating rod is one of the important factors affecting the performance of Baling net.The driving force and floating rod structure determine whether the power floating rod can be pushed stably.The power floating rod with large driving force can improve the work efficiency,increase the fishing boat’s net release times and improve the economic benefits.In order to reduce the single net release time and improve the fishing efficiency,a kind of active dynamic floating rod for the balustrade net of saury was designed and its dynamic performance was studied.The main research contents and results of this paper are as follows:(1)Based on the theoretical calculation and mechanical analysis,the theoretical feasibility of the dynamic floating rod is confirmed,and the three-dimensional model size of the dynamic floating rod is obtained through the stability calculation.According to the requirements of saury fishing,an underwater propeller is proposed as the power device.On this basis,the design of dynamic floating rod is realized by using Solid Works 3D modeling software.(2)Simulation test and result analysis of dynamic floating rod.Based on Reynolds averaged Navier Stokes(RANS)equation and SST K-ω Based on the turbulence model equation,the simulation test of water resistance of dynamic floating rod under different draft and speed is carried out by using ANSYS CFD software,so as to provide a basis for the rationality of dynamic floating rod design.The simulation test results show that when the propulsion speed is in the range of 0.1-0.5m/s,the resistance is positively correlated with the propulsion speed,in which the resistance increases the fastest in the range of 0.2-0.4m/s,and the resistance increases slowly in other intervals;When the Wading depth is in the range of 210-360 mm,the resistance is positively correlated with the Wading depth,and when the Wading depth is in the range of 360-720 mm,the resistance is negatively correlated with the Wading depth.The simulation tests show that the Wading depth increases from 210 mm to 270 mm,and the resistance of the floating rod increases in turn.Under five groups of Wading depth,the resistance of the dynamic floating rod increases with the increase of propulsion speed in the range of 0.1-0.5m/s.From the overall growth trend,the resistance of the dynamic floating rod is directly proportional to the increase of propulsion speed.(3)Indoor test,prototype test,offshore test and test result analysis.The indoor flume test shows that the torque generated by the propeller causes the floating rod to rotate and the floating rod loses its driving force.It is necessary to pay attention to the installation position and try to avoid the distance between the propeller and the floating rod.The prototype test formulates the most reliable installation method according to the working environment of autumn swordfish fishing,and proves that the structural design of Moso bamboo and multi cylinder can effectively prevent the rotation of floating rod in the propulsion process,and the installation position of propeller can effectively avoid the generation of force arm,which greatly improves the efficiency of propeller.At the same time,it is also found that in the face of the problem of insufficient power in complex sea conditions,dynamic floating rods need underwater thrusters with large thrust to meet the needs of improving fishing efficiency.(4)Comparison and verification between simulation and prototype test.In order to verify the reliability of numerical simulation,nine dynamic floating rod calculation models are established based on the prototype parameters and test data,and the simulation results are drawn together with the tensile data of prototype test.Comparing the resistance calculated by CFD with the measured resistance of the prototype pool,the error is within9.5%.At the same time,when the speed of the dynamic floating rod prototype is 0.5m/s and the Wading depth is 360 mm,the resistance is the largest,which is consistent with the CFD calculation results.When the speed of the power floating rod is 0.29m/s and the Wading depth is 300 mm,the resistance is 14.6n,which can push the swordfish lifting net to the designated position in a short time.Meet the requirements of improving the efficiency of ocean fishing.Through the comparison between the prototype and numerical simulation,it can be proved that the calculation model of the dynamic floating rod of saury’s sidelift net is accurate.After many field tests,the results show that the design method of the power floating rod has high reliability.At the same time,the power floating rod is equipped with p75 underwater propeller.When the maximum power is 260 W,it can produce a maximum thrust of 5kg and the fastest propulsion speed is 0.29m/s.The installation mode of dynamic floating rod makes it able to adapt to the complex changes at sea,provides a good reference value for the promotion and application of dynamic floating rod,and provides a good technical support for the research of fishing equipment. |
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