Boundary Conditions

Boundary Conditions

Wall Boundary Condition

At closed boundaries, two boundary conditions are applied. The first is zero flow normal to the boundary, and the second is the tangential shear stress due to flow parallel to the wall boundary. In CMS, two boundary conditions are available for tangential flow to walls. The first is a free-slip boundary condition in which the tangential shear stress set to zero, and the second is partial-slip boundary condition in which a friction term is included by assuming a log-law for a rough wall.

${\overrightarrow {\tau }}_{wall}=-\rho c_{wall}\mid {\overrightarrow {U_{\Box }}}\mid {\overrightarrow {U_{\Box }}}$ (2-34)

where $c_{wall}$ is the wall friction coefficient equal to