Static Approximation Skin Effect

This option adds a static (Ohmic losses) approximation skin effect.

Note: The material parameters for the skin effect are defined with the DI card. The SK card then uses the label defined at the DI card.

Parameters:

Thickness of elements: The thickness d of the surface elements in metres (if an SF card is present, this is always scaled).
Material label: Label of the material which will be used (as specified in the DI card).

The required parameters are $μ_{r}$ , $\tan δ_{u}$ and $σ$ (defined with the DI card). If applied to surfaces then also the thickness d is required.

The following restrictions apply:

A good conductivity is required, satisfying the condition $σ ≫ ω ε_{0}$ .
For wires the skin depth must satisfy the condition $δ_{skin} > ϱ$ where $ϱ$ is the wire radius. The surface impedance is given by $Z_{s}^{'} = \frac{1}{π ϱ^{2} σ}$
For metallic surfaces the skin depth must satisfy the condition $δ_{skin} > \frac{d}{2}$ . The surface impedance is given by $Z_{s} = \frac{1}{σ d}$ .