The Volume Integral Equations Method in Magnetostatics Problems

In this article, use of volume integral equations method for calculations of magnetic systems is considered. GFUN program package based on integral approach to magnetostatics applies the method of collocations and piecewise constant approximations of unknown variables within the elements to discretization of equations. The limitation of this approach is related to singularity of the integral equations kernel. An alternative to collocation method, replacing observation point by integration over discretization elements, is considered in this article. This approach enables one to use higher order approximations for unknown variables. In the context of the finite element method, the piecewise constant and piecewise linear approximations of unknown variables are considered. The problem of computing matrix elements for discretized systems of equations can be reduced to evaluation of sixth-order integrals, singular ones in the general case, over two different elements of the computational region. Possible methods are proposed for calculating this kind of integrals. Iterative processes for solving the arising nonlinear systems of discretized equation are discussed. The proposed approach enables one to build discretizations with higher precision of approximation for the initial volume integral equations of magnetostatics. The proposed method was used for 3D modeling of a dipole magnet. Comparison of results obtained for simulation of the dipole magnet using different versions of integral magnetostatics problem discretization are given.

magnetostatics, volume integral equations method, the finite element method, discretization, nonlinear problem, iterative process