# Radiator values for porous media

#1

Hi guys,

I´m trying to set up some more detailed simulations. As shown in the Formula-Student-Webinar I want to use the advanced simulation concept: porous media.

The problem is that I got no idea what values I should use.
There are:
a)Coefficient d
b)Coefficient f
Coordinate system properties
c)e1
d)e3

My radiator is in a sidepod in a angle of approximately 45°.
Is there any method to calculate these values (a-d) or can I get them of the manufacturer and convert them?

Couldn´t find a helpful forum entry for this. Maybe a short how to for this topic wouldn´t be bad.

If interested I can send you a link to the project, but it isn´t much done yet.

Greetings
David

Define Porous media by Volume Selection
#2

Hi David (@BRT)!

You can also have a look at the documentation page about Porous Media

Let me know if that helps!

Cheers,

Jousef

#3

Hi Jousef,

I had some time to have a closer look at This two descriptions. I understand that e1, e2, e3 are the main directions of my radiator in relation to the main coordinate system.

The main problems are the coefficients d and f. When I got it right they can just be determined by tests. I don´t think that I can do this myself so ill ask the producing company of our radiator.
Or is there a simple way to determine them ??

Cheers,
David

#4

Hi David!

Very sorry for the late response!

As posted by our PowerUser @varsey you can determine the coefficients in the following manner:

• d = 150 (1-eps)^2 / (eps^2 * D^2)

• f = 2 * 1.75 * (1-eps) / (eps^3 * D)

Where eps and D is characteristics of your porous media (porosity and mean particles diameter).

These documents might also be helpful for you: Transport Phenomena and Porous Media in OpenFOAM

Let me know if I can do anything else for you.

Jousef

#5

Hi,

I read the above conversation and also the links provided by Jousef. But I am still confused as to how to get the values of e1 and e3 for the porous media.
Could you explain it in detail.

Varun

#6

Hi Varun (@pdarda)!

I think @varsey explained it very well here: Simulation - Porous Media

From one document listed above you can also find the following explanation:

“The global coordinate system of the geometry is set by default…Here it is specified with two vectors. The vector e1 is created as a linear combination of the global x- and y-axes so it is aligned with the angled duct and the vector e2 is set orthogonal to e1. The vector e3 is then created in a right handed order by the coordinateSystem class orthogonally to both e1 and e2.”

If that is not enough could you explain in detail what you are struggling with?

As an example, please have a look at this project: Gas Flow Through Catalytic Converter And Exhaust

Best,

Jousef

#7

Hi,

So the vector e1 represents the direction in which the material will be porous, right?
Then will the vector direction for the nonporous direction be zero?

Could you please specify the direction vector for the following case so that I can understand how to define them.
Suppose a porous media is in the plane perpendicular to z axis and air flows in the direction of +z axis.
The material is porous in the z direction only and non porous along other directions.
So what will be the values of e1 and e3 vectors for this case?

Varun

#8

Hi @pdarda!

For the case you described e1 has coordinates (1, 0, 0) and e3 has ccordinates (0, 0, 1) (I’ve described simulation with exactly the same configutation of flow on screenshot here - link)

So the vector e1 represents the direction in which the material will be porous, right?

Vectors e1 and e3 create a coordinate system, so you cant define just one of them to set direction of your porosity. You have to define at least two vectors among e1, e2 and e3.

#9

Thanks @varsey

Now I understood the what they mean/
Thanks once again!!!

Best,
Varun