How to correctly set up boundary conditions for a turbine with inlet pressure, total volume flow, and outlet pressure?

I would like to know the correct way to set up boundary conditions for a hydraulic turbine, where the water entering the turbine is at approximately 23 PSI, and the pressure at the outlet is simply atmospheric pressure (14.7 PSI). The volume of water is also flowing through the turbine at a rate of 20 ft^3/s.

Here's what I have tried so far:

  1. Use a total pressure boundary condition for the inlet (23 PSI), and outlet volume flow at the outlet (20 ft^3/s).
    • This gave me a negative pressure warning while running the simulation.
  2. Flip the above. So, inlet volume flow (20 ft^3/s) at the inlet, and total pressure (14.7 PSI, or 1 ATM) at the outlet.
    • This didn't give me any warnings, but it doesn't seem correct to me because I didn't specify anywhere that the water is at 23 PSI when it enters the turbine.

My issue seems to lie in the fact that SolidWorks Flow Simulation won't let me specify multiple boundary conditions for one face.

Any help is greatly appreciated.

Josh

SolidworksFlow Simulation