| With the continuous growth of the world’s population and the growing prosperity of the social economy,the market’s demand for fish has also expanded,and the aquaculture industry has broad prospects for development.As offshore aquaculture has become saturated with the exploitation of shallow sea and bays,and it is easy to cause serious damage to the marine ecological environment,cage aquaculture is rapidly developing in the exposed waters.However,the sea conditions in the exposed waters are more severe than those in the offshore,and the environment with strong winds and waves poses a high challenge to the safety of cage systems and farmed fish.The submersible net cage is a kind of breeding equipment with strong adaptability to deep-sea waters.The cage has two states of floating and dive.When the sea area is in a bad sea condition,the cage can be temporarily submerged to a certain depth below the sea surface.Because of the natural law of exponential decay of wave strength with increasing water depth effectively,the submersible net cage can avoids damage caused by wind and wave impact.Recently,the common submersible net cages often have the problem of excessive cage inclination and damage to farmed fish during the lifting movement process.To investigate lifting movement characteristics of submersible net cage,improve flotation/submersion performance of net cage,a submersible net cage flotation/submersion system using helical pipes is proposed to achieve horizontally stable floating and sinking motions.Helical pipes are arranged along the circle.The net cage is submerged when the pipes is filled of water,and the injection of high-pressure air regenerates buoyancy and enables the net cage to rise in the water.Physical experiments are carried out to study the lifting movement dynamic response of the cage.In addition,the excessive sinking depth of the cage will cause the cage collision and grounding.Therefore,the numerical simulation method is used to further investigate the relationship between the optimal sinking depth of the cage bottom under extreme waves and the wave parameters.The paper is organized as follows:1.The research background of this paper,the development of the submersible net cages and the research status at home and abroad are introduced,and the research contents and methods of this paper are proposed.2.The design of each part of the physical model of the submersible net cage is introduced in detail incombination with the actual parameters of the cage.3.Through the model experiment method,the lifting movement dynamic response of the cage under the action of still water and steady currents is studied.4.Experiments were carried out on the lifting and lowering movement of the cage under the action of waves,and the dynamic response of the cage under the action of waves was studied.5.The dynamic response characteristics of the submersible net cage under waves combined with current field are analyzed by the physical model experiments.6.The numerical simulation of the bottom’s movement of the submersible net cage under the action of waves is carried out.The optimal sinking depth of the cage under extreme waves and the dynamic response of the cage at this depth are studied. |
