Electromagnetic Characteristics Of The Wake Of A Surface Vehicle In The South China Sea

During navigation,the surface vehicle will cause the movement of the surrounding sea water to form a wake.The wake contains a lot of vehicle information and will show different physical characteristics from the surrounding sea water.As one of the important characteristics,the electromagnetic characteristics of wake occupy an important position in the fields of torpedo homing,ship positioning and ocean exploration.In this paper,taking the KRISO Container Ship(KCS)ship as the simulation ship model,based on the relevant theories such as magnetohydrodynamics(MHD),Maxwell equations and generalized Ohm's law,the electromagnetic field model of ship wake is established.With the help of finite element and computational fluid dynamics(CFD)simulation software,the electromagnetic characteristics of KCS ship wake are simulated,and the electromagnetic characteristics of KCS ship wake under the sea conditions in the South China Sea are studied in combination with the real sea environment.The main contents of this paper are as follows:Firstly,Modeling and simulation analysis of hull induced magnetic field.Based on the principle of finite element numerical simulation,according to Maxwell equations and the constitutive relationship of medium,combined with the boundary conditions of electromagnetic field,the ship hull induced magnetic field model is established;the KCS ship model is built by selecting ship parameters,and the calculation domain model of KCS hull induced magnetic field is established.By selecting appropriate boundary conditions and grid size,the KCS hull induced magnetic field under different magnetic field environments is simulated and analyzed,and the influence of relative permeability and hull thickness of different hull materials on KCS hull induced magnetic field is discussed.Secondly,Modeling and simulation analysis of ship wake velocity field and induced electromagnetic field.Combined with the relevant theories of ship hydrodynamics and computational fluid dynamics,the wake velocity field of KCS ship is simulated by CFD software,and the shape and velocity distribution of ship wake under different water depth,different velocity and different distance are explored.Based on the principles of MHD motion equation,Maxwell's equations and generalized Ohm's law,the ship wake induced magnetic field model is established.Combined with the simulation of KCS ship wake velocity field distribution,the distribution law of KCS ship wake magnetic field with unidirectional background magnetic field,multidirectional background magnetic field and different speeds is analyzed.Similarly,starting from the ship wake velocity field,the model of ship wake induced electric field is established by Maxwell equations,and the spatial distribution law of KCS ship wake induced electric field intensity and induced current density under different background magnetic field intensity and different water depths is simulated and analyzed by the control variable method.Thirdly,Study on electromagnetic characteristics of ship wake in the environment of the South China Sea.Based on the geomagnetic field cut by moving seawater,the sea wave and ocean current induced magnetic field model is established,and the distribution law of sea wave and ocean current induced magnetic field under different background magnetic field intensity and different speeds is simulated and analyzed.By searching the data of the South China Sea and selecting the measurement point,the sea state and geomagnetic field data of the measurement point are obtained,and the KCS hull induced magnetic field,wake induced magnetic field,ocean current induced magnetic field and sea wave induced magnetic field under the environment of the measurement point are simulated,characteristic differences of these kinds of induced magnetic fields are compared,the magnitude of ocean induced total magnetic field under different conditions is explored,and the distribution law of ocean induced total magnetic field is obtained.The results show that the greater the magnetic inclination and magnetic declination,the lower the extreme value of the wake induced magnetic field,the more regular the magnetic field distribution and the less the wave crest;In the waters directly below the ship,the magnetic field induced by the wake can be approximated as the total magnetic field induced by seawater composed of the sea state magnetic field and the wake magnetic field;The more complicated the sea environment is,the greater the total magnetic field intensity induced by seawater in the sea area around the KCS ship during sailing;For the total ocean magnetic field composed of KCS hull induced magnetic field,wake induced magnetic field,ocean current induced magnetic field and sea wave induced magnetic field,it is consistent with the change trend of hull induced magnetic field in X direction and with the change trend of seawater induced total magnetic field composed of ocean current,sea wave and wake induced magnetic field in Y direction.