Research On The Expansion Performance Of Trawl Fishing Vessel’s Net Port Under Real Sea Operation

Compared with developed countries in fishing technology,China’s marine fisheries have a relatively low level of intelligence in trawl fishing equipment,and the fishing equipment of fishing vessels is also uneven.The position and size of the net during trawling operations are basically determined by experience,making it difficult to control the balance of the net equipment.This will reduce fishing efficiency and waste fishery resources.This article relies on a national key research and development project to conduct real sea experiments and numerical simulation research on the horizontal and vertical expansion of the trawl fishing vessel’s net mouth.When trawling,the main method is to adjust the fishing direction,speed,and catch and release of the towing line to adjust the fishing conditions for trawling operations.Important research parameters include net position and net mouth size.Net position refers to the operating position of a fishing net in the real sea,and net mouth size is divided into vertical expansion and horizontal expansion of the net mouth.Reasonable opening is the key to ensuring the sweeping area of trawl operations and improving fishing efficiency.This article mainly conducts real sea experiments and numerical simulations on the hydrodynamic performance of trawl fishing vessels under operating conditions.The main research contents are as follows:(1)Real sea experiments on the hydrodynamic performance of trawl fishing vessels under operating conditions.A monitoring device for the length and tension of the towing rope has been designed,and a data collection system for the length and tension of the towing rope has been developed.During the operation of a trawler,the length and tension of the towing rope can be collected in real-time,and the balance adjustment of the towing rope can be achieved based on the length and tension of the left and right towing ropes.Developed nets and designed a sea trial plan for the net mouth and net position of trawl fishing vessels based on the actual conditions of a certain scientific research vessel.Two 10 day sea trials were conducted to investigate the effects of different ship speeds and different mesh lengths on the horizontal and vertical expansion of the trawler’s net mouth,based on the location of the fish shoal in the water layer,under various operating conditions such as downstream and upstream.At the same time,in order to obtain the optimal sweep area of the net mouth,horizontal and vertical expansion schemes for trawl fishing vessels were explored to improve fishing efficiency and reduce operational energy consumption.(2)Numerical simulation of the hydrodynamic performance of trawlers under operating conditions.During the actual sea trial,a network location data collection scheme was designed.During the actual sea trial,the depth at the location of the depth sensor is synchronously collected by relying on the depth sensor placed on the mesh.A numerical model of the trawl was established based on the measurement data of actual sea trials to study the effects of different speeds on the horizontal and vertical expansion of the trawl,and a comparative study was conducted with the results of actual sea trials.Exploring the changes in the position and shape of trawl nets and control methods has improved the efficiency of trawl fishing operations and the stability of trawl systems.