Lid-driven cavity flow (2-D): Visco-elastic materials

Hi,

I am trying to model flow of visco-elastic materials (using Oldroyd-B model) in a lid-driven cavity.

In this problem the top boundary/wall is sliding, whereas the side and the bottom walls are bound by no-slip boundary conditions. I have specified the Reynolds number (Re) and Weissenberg number (Wi) as per the problem. The physics of the problem is specified by using general form of PDE (PDE(g)) and Laminar flow.

I am unable to write the appropriate stress boundary-conditions for this model. Kindly assist me through this problem.

Thanks in advance.
Saurabh