Open channel with a weir placed at midway
 

I'm using ansys fulent. I'm specifying pressure at both inlet and outlet.
I specified inlet total gauge pressure as 1pa and outlet a zero. Solver- steady lamina material-water reference values- from inlet solutions methods- SIMPlE
Standard initiation- initial guess compute from inlet
When I run the calculation reverse flow is occurring and solution doesn't converged.
What to do ?