The Surface Roughness subnode is available from the context menu (right-click the
Impedance Boundary Condition or
Transition Boundary Condition parent node) or from the
Physics toolbar,
Attributes menu.
Select a Surface roughness model —
Sawtooth (the default) or
Snowball. For
Sawtooth, enter a value or expression for the
Surface roughness ΔRMS (SI unit: m). For
Snowball, enter a
Snowball hexagon cell area Ahex (SI unit: m
2). Then enter values for the
Snowball radius (SI unit: m) and
Number of snowballs in the table, adding as many rows as you need.
The Surface Roughness increases the impedance, and consequently it decreases the surface current density of
Impedance Boundary Condition or
Transition Boundary Condition, proportional to the ratio between the impedance of a rough surface and that of a smooth surface:
where ΔRMS is the root mean square of the surface roughness, and
δ is the skip depth of the material (
Ref. 1).
where Ahex is the hexagonal area of a unit cell,
Ni is the number of snowballs,
ai is the radius of a snowball, and
δ is the skip depth of the material (
Ref. 2).
For Transition Boundary Condition, select Side —
Upside (the default) or
Downside to define on which side the
Surface Roughness is applied. The red arrow visualized on the selected boundaries always indicates the upside.