# Negative Pressure

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 August 26, 2007, 11:28 Hi guys, I used lesInterFoam #1 New Member   morteza Join Date: Mar 2009 Posts: 18 Rep Power: 8 Hi guys, I used lesInterFoam to simulate flow around a wedge. My boundary conditions are as follows: Top and bottom boundaries are SYMMETRY Left boundary is INLET Right boundary is OUTLET wedge boundary is WALL I choose gamma=1 for both internal field and inlet value to disable the 2nd phase. Uinlet=100 m/s poutlet=1.0e5 pas rho=1000 nu=1.0e-6 But after solution the pressure is negative.

 August 26, 2007, 11:39 If the flow can be approximate #2 Senior Member   Srinath Madhavan (a.k.a pUl|) Join Date: Mar 2009 Location: Edmonton, AB, Canada Posts: 699 Rep Power: 12 If the flow can be approximated as being incompressible, then I don't see anything wrong with the pressure being negative as only the pressure difference drives the flow. Is the velocity field unphysical?

 August 26, 2007, 11:45 Hi Madhavan, thanks for your #3 New Member   morteza Join Date: Mar 2009 Posts: 18 Rep Power: 8 Hi Madhavan, thanks for your reply How can i make this negative pressure to possitive values. I want to implement a cavitation model and must have possitive pressure. thanks in advance

 August 26, 2007, 12:09 I forgot to mention it. I sol #4 New Member   morteza Join Date: Mar 2009 Posts: 18 Rep Power: 8 I forgot to mention it. I solved this case with oodles that is an incompressible solver, but there was no negative pressure. Morteza

 August 26, 2007, 12:13 Perhaps by modifying the posit #5 Senior Member   Srinath Madhavan (a.k.a pUl|) Join Date: Mar 2009 Location: Edmonton, AB, Canada Posts: 699 Rep Power: 12 Perhaps by modifying the position and/or the value of reference pressure in the lesInterFoam code. I think, the following line in pEqn.H does that: pdEqn.setReference(pdRefCell, pdRefValue); Check it out. Alternately, an easier way would be to add a sufficiently large quantity to the entire phase pressure field after each time-step and calling this new variable something else (say pve_pd) and using this in your model. Bear in mind that I know nothing about cavitation modeling and I could very well be misleading you here. Please wait for a more experienced user to comment.

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