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June 9, 2011, 06:38 
About rhoPorousSimpleFoam

#1 
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Manoj L Das
Join Date: Mar 2011
Location: Calcutta, India
Posts: 25
Rep Power: 7 
Hi,
I have a small question. If 'rhoPorousSimpleFoam' is a steady state solver then why it asks for 'deltaT'? If it is a pseudo time step then What will be the difference in solution if we run the case with different deltaT, say the same case is run once with dt=1sec and once with say dt= 0.001 sec?? Further, as in the governing equation the porosity comes only in time derivative (ddt) term, then how it considers the porosity if it is a steady state solver? Regards, MLD 

June 9, 2011, 09:53 

#2 
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Dima Risch
Join Date: Jun 2011
Location: Cologne
Posts: 22
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Hi, MLD
i think deltaT is set to calculate the total amount of iterations startTime 0; endTime 50; deltaT 1; should be the same like startTime 0; endTime 5; deltaT 0.1; (but not sure) therefore writeInterval had to be >= 1 in what governing equation do you find the porosity comes only in time derivative (ddt) term like i understand you can set the porousZone/porosity Explizit or Implizit if(pressureImplicitPorosity){...} else(...){...} in the UEqn and pEqn pressureImplicitPorosity is defined in createFields and is set ON with the nUCorrectors entry in the fvSolution the porosity is considered in the UEqn by pZones.addResistance(UEqn()); but i am new to OpenFoam and to fluiddynamics and this is what i understand, please correct me, if i am wrong. regards, Dima 

June 10, 2011, 11:12 

#3 
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Dima Risch
Join Date: Jun 2011
Location: Cologne
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Hi, MLD, its me again
now i found the governing equation you talked about, and i understand why you ask this so i take a look at the porousZone files in /OpenFOAM/OpenFOAM1.7.1/src/finiteVolume/cfdTools/general/porousMedia/ and in the porousZone.H i found Code:
// porosity of the zone (0 < porosity <= 1) // Placeholder for treatment of temporal terms. // Currently unused. scalar porosity_; and therefore only the source term which is represented in the DarcyForchheimer law is important regards, Dima 

June 13, 2011, 00:49 

#4 
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Manoj L Das
Join Date: Mar 2011
Location: Calcutta, India
Posts: 25
Rep Power: 7 
Hi Dima,
Thanks for your quick replies. And you are right, I was also studying the codes of 'rhoPorousSimleFoam' and found that it does not consider the porosity 'phi' explicitly, but it considers the superficial velocity instead. Check also the following link... RhoExplicitPorousSimpleFoam. In my case considering only the porous drag is not enough and at some point of time I would have to use another solver named 'rhoPorousMRFSimpleFoam' which seems to be a transient solver for porosity. We can share our experiences. In fact my projects requirements are beyond the existing solver capabilities in OF and after getting the results from the existing solvers I would like to modify the existing solvers for my project needs, which would consider the transient porosity from DEM (discrete element modeling). Regards, MLD 

June 13, 2011, 05:38 

#5 
New Member
Manoj L Das
Join Date: Mar 2011
Location: Calcutta, India
Posts: 25
Rep Power: 7 
Hi,
What form of Energy euation is solved in rhoPorousSimpleFoam. I mean, does it takes the heat transfer between fluid and solid parts. And if yes then where it asks for the thermal conductivities of fluid and solid. See the part of the code in file hEqn.H : 00001 { 00002 fvScalarMatrix hEqn 00003 ( 00004 fvm::div(phi, h) 00005  fvm::Sp(fvc::div(phi), h) 00006  fvm::laplacian(turbulence>alphaEff(), h) 00007 == 00008 fvc::div(phi/fvc::interpolate(rho)*fvc::interpolate(p, "div(U,p)")) 00009  p*fvc::div(phi/fvc::interpolate(rho)) 00010 ); Here, what it refer to 'alphaEff()', is it thermal diffusivity?? The question may be stupid as I ma new user of this kind of code. Regards, MLD 

June 14, 2011, 05:07 

#6  
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Dima Risch
Join Date: Jun 2011
Location: Cologne
Posts: 22
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Hi,
thank you for the link. i think you are right with the 'alphaEff()' is the thermal diffusivity. EDIT: in e.g. src/turbulenceModels/compressible/RAS/kEpsilon/kEpsilon.H Quote:
maybe chtMultiRegionFoam takes both fluid and solid in its Energy/Temperature Eqn. would be nice, if someone who is familiar with that could reply regards, Dima Last edited by dima; June 14, 2011 at 06:13. 

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