Gradient of velocity on the wall
 

Dear all,

If using the green gauss theorem to compute the gradient of velocity in the cell centered finite volume method, how should the green gauss theorem be implemented to calculate the gradient of velocity on the wall?

All the best,

The velocity gradient at a wall is nothing else that du/dy|wall (u in the streamwise direction and y in normal-to-wall direction). It has nothing to do with a FV or other methods, so your question is not very clear to me. The problem is only in the accuracy that is governed by the discretization of the derivative but is strongly affected by the grid refinement at the wall.