[SergioCosta]

I need to setup a simulation model with a porous metal plate in the center of a rectangular duct air flows at a known temperature T and velocity U from the left. (see Figure 1 below)
MY OBJECTIVE IS TO CALCULATE THE PRESSURE DROP IN THE (COPPER) POROUS PLATE. The materials and dimensions are known.
Refer to the post trihttps://www.cfd-online.com/Forums/openfoam-solving/145333-how-set-correctly-porosity-properties-use-porousinterfoam.html
MY DOUBT is how to set properly the values of porosity, D, F, e1, e2 in the
constant / openfoam file in the text below
ANOTHER DOUBT: according to my Figure 2 below D and F are functions (also) of the porosity. So, why is it necessary to write the porosity explicitly ? Is it sufficient to calculate D and F externally and write them ?
SO, THE QUESTION IS how to fill this data in this code

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.2.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "constant";
object porosityProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
porosity1
{
type DarcyForchheimer;
active yes;
cellZone porouszone;
porosity 0.5;
permeability 5e-11;
　
DarcyForchheimerCoeffs
{
mu mu;
d d [0 -2 0 0 0 0 0] (0.1e11 0.1e11 0.1e11); //0.5/5e-11=0.1e11
f f [0 -1 0 0 0 0 0] (0 0 0);
　
//coordinateSystem
//{
// e1 (0.70710678 0.70710678 0);
// e2 (0 0 1);
//}
}
}

[LuckyTran]

It is enough to explicitly specify D&F. The formula you show that has a porosity in it is coming from a correlation for flow through packed beds.


In the early days of porous metals continuing into the present, that was no flow data available for porous foams and so people stupidly used correlations for packed beds. Mass porosity is very easy to measure, you just weigh the foam, and so people liked it. It's much easier to do CFD and make some colorful pictures than come up with actual data. One reason is incompetence but probably the bigger reason is lack of funding. CFD is very cheap with high ROI, equipment is expensive with low ROI.

[SergioCosta]

Hi and thanks for the comment.
The info I need is only related to the way of inserting D and F in the code. The point is HOW to explicitly specify D&F in the vectorial way. Can you help me on this?
About the equation, which is not the focus of my question, it is sufficiently good for my purposes, and I could prove this with a real laboratory test. The text in page 2 (near Eq.3) is clear about the applicability.
https://www.researchgate.net/publica...tal_structures

[LuckyTran]

If it's not a question then maybe don't ask it as a question....

D and F are vectors

the coordinateSystem constructor builds the local coordinate system which D and F references from the global coordinate system. e1 is the 1st ordinate, e2 is the 2nd ordinate, e3 is not an input but is orthogonal to e1 and e2. e1 (1 0 0 ) e2 ( 0 1 0) would be keeping the cartesian x,y,z coordinate system. If you have constant scalars with no directinoality then you can put any valid combination for e1 and e2 (any e2 that isn't parallel with e1).


I'm not a telepath, I don't know what your data suggests D and F are to tell you what exactly to put into the dict.

[SergioCosta]

Thank you very much Lucky. Now I could understand how those vectors are organized. The file describing the Class
Foam:orosityModels:arcyForchheimer
has the details
/////////////////////////////////////////////
if (coordSys_.R().uniform())
{
D_.setSize(1);
F_.setSize(1);

D_[0] = Zero;
D_[0].xx() = dXYZ_.value().x();
D_[0].yy() = dXYZ_.value().y();
D_[0].zz() = dXYZ_.value().z();

D_[0] = coordSys_.R().transform(Zero, D_[0]);

// leading 0.5 is from 1/2*rho
F_[0] = Zero;
F_[0].xx() = 0.5*fXYZ_.value().x();
F_[0].yy() = 0.5*fXYZ_.value().y();
F_[0].zz() = 0.5*fXYZ_.value().z();

F_[0] = coordSys_.R().transform(Zero, F_[0]);
}
else
{
const labelList& cells = mesh_.cellZones()[zoneName_];

D_.setSize(cells.size());
F_.setSize(cells.size());