Lubrication flow

wodas

Hi I'm a FIDAP user. I have a problem with correct boundary conditions. I try to model fluid flow across the channel witch has large ratio of dimentions (I mean lenght/thickness about 3000). This is a common situation in lubrication problems.

Fluid was assumed as uncompressible and isothermal. I have a velocity b.c. at the inlet and "nothing" at the outlet, the results show that at the outlet there is nonzero pressure value. It is incorrect because at the outlet atmospheric pressure shout be equal to zero. Each attempt to set pressure b.c. at the outlet was unsuccessful.

Have you ever modeled any lubrication task? Do you have any suggestions how to solve correctly this problem?