Understanding Navier's Slip Condition: Fixed Walls & Applicability

[Suvadip]

Is it necessary for the channel walls to move for the applicability of Navier's slip condition at the boundary. i.e., Is it possible that the channels walls are fixed, but we can apply the Navier's slip condition at both the channel walls.

 

[Andy Resnick]

The slip condition simply allows for relative motion between the fluid and sold at the interface. Slip is invoked to explain wetting, for example.