Gao Junji

Accurate calculating method of marine three-component geomagnetic field in shipboard measurement

In order to remove ship magnetizing fields interference, a method is proposed to calculate marine three-component geomagnetic field accurately. Ship magnetizing field can be shown by magnetizing parameter and it is hard to be obtained. The bound of geomagnetic vector can be got by WMM and magnetic total value can be measured in advance, thus geomagnetic vector and magnetizing parameter are taken as unknown quantities simultaneously to maximally eliminate solve for eliminating ships magnetic interference. GAPSO is used to calculate based on measured value when ship sails and sway in circle, simulation indicates that three-component geomagnetic field can be got in high precision and ships magnetic interference is removed effectively. The method is easy to operate and has important practical value for geomagnetic fields marine survey.

Study on the Modeling of Ship Induced Magnetic Field

A novel model on the calculating of ship induced magnetic field with hybrid finite element-boundary element method of double scalar potentials is presented. The full scalar potential and linearity element are adopted in ferromagnetic region. Reduced scalar potential and hybrid element mesh are adopted on the boundary surface. The coupling relationship between variables on the interface and the formulas to computing element coefficients are deduced. The degenerate transforms combination is used in deeling with singular boundary integrals. An equivalent magnetic model is proposed to compute ship mockups induced magnetic field. The three dimensional model of the ship mockup was drawn and meshed. Through the hysteresis during the magnetization of ship ferromagnet, it is pointed out that the induced magnetic field will be a bit high with the slope of basic magnetization curve as the permeability of the material. Based on that, the equivalent permeability of the material was calibrated through the curve of average relative error-relative permeability. The results of ship model experiment testify that the calculating model have good applicability to the calculating of ships induced magnetic field.