Asymptotic delta-Parametrization of Surface-Impedance Solutions

The surface impedance methods are among the most efficient for solving time-harmonic eddy-current problems with a small penetration depth. When the solution is required for a wide range of frequencies (or material conductivities) the standard approach leads to the solution of a complex-valued problem for each frequency (or conductivity). Hereafter we introduce a close method, parametrized by the skin depth ( delta), based on a formal asymptotic expansion. It provides accurate results with a reduced computational cost for a wide range of delta values