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 March 14, 2012, 13:03 Pressure inlet BCs PLEASE HELP!!!! #1 New Member   tom paice Join Date: Nov 2011 Posts: 1 Rep Power: 0 Hello, I'm trying to set the boundary conditions for a 2D open rotor problem. The open rotor consists of two counter rotating blades. I have created the meshing for each blade and a sliding interface between the meshes. I have also set the cell zones mesh motion translational velocities for each mesh. I am using a pressure based solver and a pressure inlet and pressure outlet but I am unsure what the gauge total pressure and the supersonic/initial gauge total pressure should be set at. The inlet flow is mach 0.3 ( axial velocity 102m/s) and the problem is at take-0ff sea level conditions. I have tried to set gauge total pressure and the supersonic/initial gauge total pressure using the compressible flow equations but each time I solve the inlet flow velocity will not be fixed at 102m/s which is what I require. I have been trying to solve this problem for some time! Thank you very much for you help!

 March 15, 2012, 08:43 #2 Member   Join Date: Nov 2011 Posts: 81 Rep Power: 5 I think the answer comes from the fact that you're specifying the total pressure but the velocity comes from mass flow conservation (and the static pressure is adapted consequentially to match the total pressure you specified). What you impose at the beginning is a guess to initialize the calculation but is not kept constant and is dictated by the mass flow (i.e. by the back pressure). Maybe (but I'm not sure about that, please somebody correct me if I'm wrong) the right approach should be to change the back pressure to obtain the required mass flow. Cheers, Rob

March 20, 2012, 15:00
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Quote:
 Originally Posted by robboflea Maybe (but I'm not sure about that, please somebody correct me if I'm wrong) the right approach should be to change the back pressure to obtain the required mass flow.
Change the pressure at the outlet or inlet so, that your mass flow will be correct and you get your 102 m/s or use a velocity inlet/mass flow inlet....

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