# prefcell&prefvalue meaning

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 June 22, 2013, 08:42 prefcell&prefvalue meaning #1 Member   Arjang Behnoud Join Date: Oct 2012 Posts: 57 Rep Power: 6 Hi everyone, what do the following lines do in createFields? label pRefCell = 0; scalar pRefValue = 0.0; setRefCell(p, mesh.solutionDict().subDict("PISO"), pRefCell, pRefValue); thanks in advance

 June 22, 2013, 11:58 #2 Senior Member   Nima Samkhaniani Join Date: Sep 2009 Location: Tehran, Iran Posts: 1,208 Blog Entries: 1 Rep Power: 17 Dear Behnoud solvers need the value of pressure at least in one point, so this line consider the value of the pressure of pRefCell equals zero __________________ Telegram channel (https://telegram.me/openfoam4Iranian) My Weblog (http://openfoam.blogfa.com/) Training Course on OpenFOAM at (http://www.isme.ir/)

 June 22, 2013, 12:01 #3 Senior Member   Fumiya Nozaki Join Date: Jun 2010 Location: Yokohama, Japan Posts: 199 Blog Entries: 1 Rep Power: 9 Hi, If you don't fix the pressure values on any boundaries for the incompressible flow, the pressure values can not be determined. In this case you need to specify the pressure value(pRefValue) at the cell(label: pRefCell). Hope that helps, Fumiya

 July 31, 2013, 12:27 pRefvalue #4 Senior Member   musaddeque hossein Join Date: Mar 2009 Posts: 309 Rep Power: 10 Dear all: The default pref is set to a high number 1e5 as shown below in the fvsolutions file (sloshingTank2D): pRefPoint (0 0 0.15); pRefValue 1e5; Is this a standard or can it be set to zero? If it can be, how would I set it so that it is absolute zero (like in fortran absolute zero is set as 0.0d0). I look forward to your reply.

 July 31, 2013, 13:25 #5 Senior Member   Nima Samkhaniani Join Date: Sep 2009 Location: Tehran, Iran Posts: 1,208 Blog Entries: 1 Rep Power: 17 you can use zero! for incompressible case, but for compressible case you should assign absolute pressure __________________ Telegram channel (https://telegram.me/openfoam4Iranian) My Weblog (http://openfoam.blogfa.com/) Training Course on OpenFOAM at (http://www.isme.ir/)

 July 31, 2013, 14:14 pRefvalue #6 Senior Member   musaddeque hossein Join Date: Mar 2009 Posts: 309 Rep Power: 10 thanks for your response! I have another question. I need to probe a point for pressure. I do not want to a probe in controlDict since that would mean that I would have to run the solver each time I need to change the probe location, for example. I would therefore like to have the probe in the sampleDict file. I have the following code in my sampleDict file. But each time I run sample, OpenFoam ignores it. Any suggestions will be greatly appreciated. Thanks! functions { probes1 { type probes; functionObjectLibs ("libsampling.so"); region region1; probeLocations ( (0 0.5 -0.3) ); fields (p); } }

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