pressure problem in reservoir

prem

hi, I am modeling a reservoir and a hydro power tunnel.Here is my geometry definition. There is a trapezoidal approach channel for water flow(depth 2m and width 13.5 m) and 20 m long. at the end of this channel is a sloping bed( 2.5 H: 1 vertical).After this there are trash racks.Then after trash rack a tunnel begins( diameter 3m) which extends for 18 m. I set massflow inlet and outflow boundary condition.For free surface I used wall with zero shear BC.Then I set reference pressure location at a point on top free surface.I set operating pressure as 101300 Pa. There is also a drop in head ( Due to trash rack-Porous) which is 15 cm (water depth).I am getting some junk values for pressure contours. Could anyone help me in specifying pressure for my problem.Very urgent please thanks in advance