The use of modified surface impedance in a minimum-order boundary element method

It has previously been shown that by using both surface electric current and magnetic charge distributions, the equivalence principle provides the basis for a direct boundary-element (BE) method which can be used to give solutions to eddy-current problems in unbounded media. Use of the impedance boundary condition reduces the method to one of minimum order, but the present results show that in the presence of corners inaccurate results are obtained using the simple one-dimensional impedance value. Modification of surface impedance is shown to considerably improve the solution in the corner region. A similar result is obtained when a finite element solution of the conducting region is coupled to the BE method. The improvement in the accuracy of field quantities computed in the region of a corner in a two-dimensional problem is demonstrated