the initial conditions for cavity flow has all the velocities equal to zero except for the lid, the stream-functions are all zero except for the lid (Ulid*height), and is the vorticity all zero except for the lid being the double derivative of the stream function?..or is that zero as well?

thanks

what I have done so far is define the velocity of the top - Utop, then dPsi/dy for the stream function = Utop*height. Then I differentiate the velocities to get the vorticity within the cavity. But, my as my iterations get larger my velocities take off. And, I can't figure out why.

thanks