[patpat]

I am modeling the deformation of a water droplet placed on a horizontal flat surface in a two-phase system (VOF model). The flow of the oil phase causes droplet deformation. The oil flow is parallel to the solid surface (wall). I want to read/extract from the Fluent value of dynamic contact angle of stationary but deformed droplet shape (in every iteration step for transient simulation).

I will use the relationship given in the attachment where ∇∅ denotes the gradient of volume fraction. The problem I have met is how to impose the condition |∇∅|=1 on the wall. This boundary condition is necessary to correctly calculate the gradient near the wall (cells adjacent to the wall).
I would be grateful for any help.