A case study on open boundary techniques for electromagnetic field problems with translational symmetry

Antônio Flavio Licarião Nogueira


The paper discusses two finite element open boundary techniques for the solution of electromagnetic field problems with translational symmetry. Firstly, the underlying assumptions and ideas behind the techniques of simple truncation and Kelvin transformation are presented. The techniques are then analyzed computationally with an instructive problem. This consists of a pair of two parallel and long conductive busbars where the force due to currents in opposing directions is to be evaluated. The value of the force calculated analytically is used to check the accuracy of the computed forces. The main features of the numerical models are explained and a comparative study based on the necessary steps to reach a specified accuracy in computed forces is presented. Numerical results show that to obtain accuracy better than 1% using the simple truncation method, very large outer boundaries must be employed. With the Kelvin method, accuracy better than 0.1% is readily achieved without using a large number of mesh elements.

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