Mechanical Calculation Of The Beam Shrimp Trawl Fishing Gear In Zhoushan Zhejiang

Along with the traditional economic fish resources of the East China Sea declining, beam shrimp trawl gradually developed. So far, the production of the shrimp in Zhejiang province on the East China Sea has reached three hundred and seventy nine thousand t, accounting for 13% of the total marine fish catch in Zhejiang province, the beam shrimp trawl has become a main pattern of fishing operation. The purpose of this Master thesis is to further analysis fishing operation by mechanics calculation of beam shrimp trawl.This article is based on the model experiment, which was accomplished in the circulating water channel of Tokyo University of Marine Science and Technology, then according to the model experiments results to calculate the beam shrimp trawl mechanics nature. First, through the numerical solution of warp shape and tension, we can work out the warp shape and tension in the process of drag. Second, the beam is equivalent to a continuous beam. Through solving the three moment equation, we can deduce the method to calculate the tension of cross rope acting on the beam. Then figure out the bending moment and shearing force of the beam. The results show that the bending moment is ax symmetric with the line across the beam center, while the shearing force is point symmetry with the center. The cross ropes whose tension acting on the beam is minimum is the cross ropes on the two endpoints of beam, while the maximum tension cross ropes are the second ropes from the beam endpoints to the center, the maximum tension-compression of the beam under the max experiment trawl speed is far lesser then the allowable stress of steel. So the beam can be made of other material whose allowable stress permits. Last, the analysis of the beam shrimp trawl nets. The nets are regarded as full soft curved film surface. Using nonmomental theory of shell, the basic differential equations about shape and tension of nets were deduced. According to the special structure of mesh, the basic differential equations can be solved with finite difference method. From the results of the first section net solution, this section takes on plane net, the shape and tension in z-axis without change. It complies with the actual situation. Because of the uncertainty of the flow in the net, the precise value can't be obtained with the finite difference method. Therefore, we can get the approximate value by the beam shrimp trawl net shape and the results match the tension of warp from the experiments results.