Prediction Of Resistance And Seakeeping Of Trawlers Considering Fishing Gear Influence

China has a long coastline and rich marine resources.Therefore,China vigorously develops fishery resources to meet the needs of the people's marine fish products,while promoting the development of China's economy.There are a lot of fishing boats in China,especially the small and medium-sized ones,whose operation area is coastal or inshore.However,the transitional fishing of offshore fishery resources has brought great pressure to nature.In order to protect the ecological environment of offshore marine resources,the state has issued a series of fishing policies,and the control of fishery resources is more and more strict.With the development of society and the improvement of people's quality of life,offshore fishery resources can not meet people's daily needs.The development of ocean fishery is the general trend,so the role of large-scale ocean fishing vessels is more and more obvious.The large-scale ocean trawlers play the main role in the fishing operation.Considering the complexity of the marine environment,the research of resistance and Seakeeping is a crucial link in the design and construction of this type of ship,so it is of practical significance to study the resistance and seakeeping performance of large-scale ocean trawlers under waves.In recent decades,computational fluid dynamics(CFD),with its advantages of economy and efficiency.In this paper,the theory of CFD,the governing equations of fluid motion,the discretization method and the mesh theory are introduced.The selection of turbulence models,including S-A model,k-? model and K-? model.Numerical wave making and elimination is one of the important contents of this part,because this paper mainly studies the trawler's motion response in regular waves.Then the boundary conditions of entrance,exit,symmetry and wall are introduced.In this paper,taking a large-scale ocean fishing boat as an example,with the aid of CFD technology,the resistance performance and seakeeping performance of the ship are predicted and analyzed,which provides a theoretical reference for the design and construction of the ship.First of all,numerical simulation is carried out according to KCs standard ship type,and its resistance is calculated to verify the feasibility of relevant theories and methods,and provide guarantee for the accuracy of the data obtained in this paper.Then,the resistance of trawler is calculated.Starting from the influence of the towing force of fishing gear on the trawler,the towing force of fishing gear causes the change of the ship's longitudinal angle and the resistance in the horizontal direction.In this paper,the towing force of fishing gear is simulated by the way of loading force.According to the different longitudinal angle,six working conditions are determined,each working condition corresponds to six speeds,and the trawler model is simulated according to the designed working conditions Then the total resistance,friction resistance and pressure difference resistance are analyzed and predicted.Comparing the friction resistance with the empirical value,the simulation value and the empirical value are in good agreement.The results show that the friction resistance also goes through a slow to slow growth process with the increase of the wet surface area.Then,the resistance of trawler is calculated.Starting from the influence of the towing force of fishing gear on the trawler,the towing force of fishing gear causes the change of the ship's longitudinal angle and the resistance in the horizontal direction.In this paper,the towing force of fishing gear is simulated by the way of loading force.According to the different longitudinal angle,six working conditions are determined,each working condition corresponds to six speeds,and the trawler model is simulated according to the designed working conditions Then the total resistance,friction resistance and pressure difference resistance are analyzed and predicted.Comparing the friction resistance with the empirical value,the simulation value and the empirical value are in good agreement.The results show that the friction resistance also goes through a slow to slow growth process with the increase of the wet surface area.Then,the wave resistance of trawler is simulated and predicted.Based on the difference of wave angle,the pitching and heave of three wave angles,i.e.0 ° head wave,45 ° bow oblique wave and 90 ° transverse wave,are simulated.According to the calculation results,the prediction is made,and the result is found at ? / L< 1.26,the pitch angle of 0 ° wave angle is slightly greater than that of 45 ° and 90 ° direction,which indicates that the pitch response of 0 ° wave angle is relatively large.From the three curves,the overall trend is upward growth.In the same ? / L,the heave response at 90 ° wave angle is larger than that at other wave angles.Although there are local fluctuations,the general trend is upward.When ? / L > 1.73,the curvature of pitch response curve begins to decrease,which provides a reference for trawler design.