Numerical Study On Hydrodynamic Characteristics Of Fishery Administration Ship In Multi Vessel Encounter

In recent years,with the rapid development of China’s economy,marine fisheries have also developed vigorously.However,overfishing,illegal discharge of oil and other hazardous wastes are not uncommon.As the "maritime police",the fishery administration ship is mainly responsible for patrolling and supervising the surrounding fishing grounds,protecting the marine environment,and inspecting the implementation of fishery laws and regulations,and so on.When a fishery administration vessel performs its tasks,it often encounters(encounters and overtakes)movements with illegal fishing vessels or other vessels.When two ships are sailing at close distances,their respective flow fields will inevitably affect the force and motion state of the other ship,which will increase the unstable factors of ship maneuvering.For the safety of ship navigation,the correct prediction of hydrodynamic interference between encountering ships can provide guidance for ship maneuvering.This article first takes two elliptical cylinders of ship-like hulls as the research objects,and only considers the three-degree-of-freedom motion model of the elliptical cylinders moving along the X-axis and Y-axis and rotating along the Z-axis.In order to facilitate the research and analysis of multiple working conditions,and to better study the ship’s encounter problems,this paper first compresses the three-dimensional grid into a two-dimensional cross-sectional grid along the Z axis to reduce the amount of calculation,and obtain the mutual interference force and deviation Flight torque and other information.It also predicts the motion trajectory,and simulates the more complex multi-degree-of-freedom motion in the direction of surge,yaw and yaw caused by the interaction effect.Then the numerical results of the model’s fixed motion(only free to fluctuate)are compared with the experimental results of Collatz to verify the effectiveness of the numerical method in this paper.Then,through systematic comparison and analysis of the numerical results obtained under different ship speed,lateral distance and hull size conditions,the effect of the three factors on the inter-ship hydrodynamic interference is summarized.Then,under the condition that the boundary conditions and other calculation parameters are the same,this paper continues to study the original problem based on the large eddy simulation method,and compares it with the original Renault average result.Finally,a medium-sized fishery administration vessel is used as the research object,and the catching and overtaking motions of fishery administration vessels under different ship speeds and lateral spacing conditions are numerically simulated,and the ship speed and the lateral distance between vessels are investigated in the law enforcement process of fishery administration vessels.Affected by interference force and moment,motion state and surrounding flow field.