A Study On Dynamic Responses Of Single-point Mooring Deep-water Aquaculture Cage

Since the 1980 s,the production of capture fisheries in the world has remained relatively stable whiling aquaculture production has increased rapidly to meet the growing population’s demand for high-quality aquatic products.Due to the large-scale and disorderly development of inshore aquaculture in China in the past decades,the aquaculture space has gradually become saturated.Moreover,the rapid development of coastal tourism and heavy industry will inevitably occupy further coastal water resources.Therefore,it is an inevitable trend to move marine aquaculture towards much deeper water in open sea areas by using of efficient farming facilities and advanced equipment.The deep-water cage is a representative of the advanced productivity of Marine aquaculture,with the obvious advantages of high production and good economic efficiency,and has become an important facility and equipment for China’s deep-water aquaculture to expand the space of Marine aquaculture.The main structure studied in this paper is a single-point mooring high-density polyethylene cage applied in the South China Sea.The main contents are as follows:First chapter introduces the research background and significance,research status at home and abroad cage systems,as well as the main content of this paper.Second chapter introduces the wave theory,the basic theory of the numerical model and the finite element method.The third and fourth chapters established the cage numerical model and carry out the relevant physical model tests to verify the validity of the numerical model.On this basis,a simulation study on the force and deformation of the actual size single-point mooring prototype cage under different combinations of wind,waves and currents was carried out.And analyzed and discussed the influence of the three types of floating collar wall thickness,three types of mooring line length and three types of sinker quality on the force of the mooring line and the deformation of the floating collar in the cage system.Finally,the deformation of the floating frame and the mooring force of the cages in single-point mooring and multi-point mooring methods are analyzed,and the influence of mooring methods on the movement characteristics of the cages is further analyzed.Chapter 5 studies the dynamic response of cages under irregular waves and currents,and analyzes the force,deformation and movement characteristics of the cages through frequency domain and time domain.The turbulence of the cage system is closely related to the tension of the mooring line,and the current rate also has an obvious main effect on both.The cage system responds in both low and wave frequencies,and behaves as a high damping system in the high frequency area.Finally,the research results of this paper are summarized and the future research directions are prospected.In the analysis of the movement of the cage,the relationship between the heave of the floating collar and the wave height and current velocity is obtained,and the longitudinal movement is highly related to the tension of the mooring line and is significantly affected by the current velocity.