The Slip Wall boundary condition is a linearized version of the
Slip Velocity option in the
Wall boundary in the CFD interface. See the section
Theory for the Wall Boundary Condition in
Theory for the Single-Phase Flow Interfaces in the
CFD Module User’s Guide.
where σs is the viscous slip coefficient,
λ0 is the mean free path,
σT is the thermal slip coefficient,
utherm is the thermal creep. There are two contributions to the slip velocity
uslip: the contribution from the acoustics stress tensor
τ and the thermal creep
utherm induced by the thermal gradient tangential to the boundary. The linearized temperature jump between the fluid and the boundary is given as,
where ζT is the temperature jump coefficient and
λ1 is the acoustic perturbation of the mean free path.