# prghpressure

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 December 29, 2018, 08:59 prghpressure #1 New Member   krishnan Join Date: Feb 2018 Posts: 16 Rep Power: 5 I urgently need clarification on pressure boundary conditions for my simulation. 1. I am performing a multiphase simulation in a water column using twoPhaseEulerFoam. The entire column is filled with water. The second phase enters through an inlet at the bottom of the column (prescribing velocity). Gravity is in the direction against the flow. I am currently using the following BC: For p: Code: ```internalField uniform 0; inlet { type calculated; value \$internalField;// } outlet { type calculated; value \$internalField; }``` For p_rgh: Code: ```internalField uniform 0; inlet { type fixedFluxPressure; value \$internalField; } outlet { type prghPressure; p \$internalField; value \$internalField; }``` For U: Code: ```inlet { type fixedValue; value uniform (0 1 0); } outlet { type pressureInletOutletVelocity; phi phi.air; value \$internalField; }``` 2. For some tutorials, the initial value in the internalfield are 0 for p and p_rgh and for some others they are 1e5. How is this decided? tonnykz likes this. Last edited by wyldckat; January 5, 2019 at 14:54. Reason: Added [CODE][/CODE] markers

 January 1, 2019, 12:40 #2 Senior Member   Mark Olesen Join Date: Mar 2009 Location: https://olesenm.github.io/ Posts: 1,279 Rep Power: 31 Compressible vs. incompressible?

 January 1, 2019, 15:08 #3 New Member   krishnan Join Date: Feb 2018 Posts: 16 Rep Power: 5 The twophaseeulerfoam solver is a compressible solver

 January 5, 2019, 06:45 #4 Super Moderator     Tobias Holzmann Join Date: Oct 2010 Location: Augsburg Posts: 2,587 Blog Entries: 6 Rep Power: 46 Hi, a) please use code tags b) Mark knows that and just gave you the hint for incompressible flows, the pressure gradient is of interest (not the absolute value) for compressible cases, the pressure gradient, as well as the absolute value, is of importance (thermodynamic - calculation of rho) __________________ Keep foaming, Tobias Holzmann

 Tags prghpressure, twophaseeulerfoam