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-   -   Negative Pressure (http://www.cfd-online.com/Forums/openfoam-solving/59479-negative-pressure.html)

morteza August 26, 2007 11:28

Hi guys, I used lesInterFoam
 
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.

http://www.cfd-online.com/OpenFOAM_D...ges/1/5266.jpg

msrinath80 August 26, 2007 11:39

If the flow can be approximate
 
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?

morteza August 26, 2007 11:45

Hi Madhavan, thanks for your
 
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

morteza August 26, 2007 12:09

I forgot to mention it. I sol
 
I forgot to mention it.
I solved this case with oodles that is an incompressible solver, but there was no negative pressure.

Morteza

msrinath80 August 26, 2007 12:13

Perhaps by modifying the posit
 
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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