Study of Open Boundary Electromagnetic Field Coupling Computation Method

In this paper a method of combining finite elements and boundary elements is proposed to try to solve opened three-dimension eddy field in electromagnetic detection, which subdivide the opened region into closed inner sub-region and opened outer infinite sub-region by defining a suppositional boundary. Then using Finite Elements Method (FEM) and Boundary Elements Method (BEM) in above two sub-region respectively, the A -Phi and A equations restricted by Coulomb criterion are derived. On suppositional boundary, direct coupling method is adopted to combine the FEM equations and BEM equations; therefore the solution of the entire region can be obtained. At last, the three-dimension magnetic field in cable eccentricity detection is computed, and magnetic field distribution and eddy loss are given out. The results show that the magnetic field has a reasonable distribution, and also that the linear relation between the computed results and the value of eccentricity has good coherence with that between the experiment results and the value of eccentricity.