Study On The Mechanical Characteristics Of The Net System Of Pile Net Separation

The Net Enclose Aquaculture is a new type of marine culture model,which aims at ecology and naturalization.As the net plane is a kind of complex flexible structure,it is easy to be torn and damaged by high wave current in typhoon weather,and this kind of culture mode is in the development stage,lacking of effective structural safety theory and design norms and standards.Therefore,this paper systematically studies the damage and safety of net in the newly developed shallow water pilaster type Net Enclose project in order to provide scientific support for the design and application of Net Enclose project.This paper focuses on the study of the mechanical characteristics of the pile net system,establishes the theoretical and numerical model of the mechanical analysis of the system,and forms an effective means of the safety analysis of the net system.On this basis,in-depth study on the damage factors of the net system is carried out,and the impact of pile-netconnection mode on the mechanical characteristics of the net system is innovatively proposed.Finally,based on the influencing factors of the damage of the net,the mechanical characteristics of the pile-net-speration system are sorted out,and the practical design theory is constructed,which is the important basis of the design code or standard of the post type pile-net-speration system.In this study,a numerical model of Net Enclose is established by using the method of concentrated mass point,focusing on the hydrodynamic characteristics of the net under the action of waves and currents,and analyzing the effects of wave height,velocity,water depth,pile spacing,rope diameter,net twine diameter,net twine length,and pile net separation mode on the maximum stress of the net system.The results show that when the wave height reaches 6m,the maximum force on the net exceeds the limit tension of the net(1.5KN),and the maximum force on the transverse direction of the rope at the point of pile-net-tie always appears on the static water surface under the action of wave,but under the action of pure water flow,the maximum force of each water depth changes little,and the water depth has little influence on the maximum force of the net system;the maximum force on the net line varies with the pile spacing and net twine diameter increase with the increase of rope diameter and net twine length.The maximum stress of the rope increases with the increase of pile spacing and rope diameter,and decreases with the increase of the length of the foot.In order to protect the safety of the net twine and the rope,it is suggested that the spacing between the fence piles should be 6-8 m,the diameter of the rope should be 27-36 mm,the diameter of the net twine should be 3.5 mm,and the length of the foot should be more than 7.08 cm but not too long.The maximum tension of the net twine under the condition of no rope protection is about 10 times of that under the condition of pile net separation;the maximum stress of the net twine and the net twine can be approximately linear with the wave height,water depth,pile spacing,diameter of the net twine,and diameter of the net twine,which is quadratic with the velocity.Among them,the maximum tension of the net twine and the rope is inversely proportional to the water depth,and the maximum tension of the wire is inversely proportional to the diameter of the rope.Water flow and wave height are the main factors that affect the maximum stress of the screen system diagram.The multiple regression model of the net system established by Morrison empirical equation can accurately reflect the maximum stress of the net system;the error of the regression model can be effectively reduced by using BP neural network multiple training;the PyQt technology in Python is used to encapsulate the maximum stress prediction model of the net system to reduce the repeated code and improve the calculation efficiency.The prediction system of the maximum stress of the purse seine can provide the design theory for the purse seine,and provide the scientific basis for the formulation of the design specifications and standards of the system.