Hi everyone! Thank you for the attention, especially you @varsey!
However I still couldn’t get this simulation running. You explained the e1 and e3 vectors but I didn’t quite understand the diference between these vectors and the Darcy-Forchheimer’s.
In my example I should set my Darcy-Forchheimer parameters’ vectors in a way that the ‘Y’ and ‘Z’ components are zero, right? It means that the porous media is only permissible in that direction (X). With that being said, what does these e1 and e3 vectors really represent? Once I determined the direction of the porous surface, what will theses e1 and e3 vectors change? I’m sorry but I couldn’t understand the physics behind it. That’s probably why I still can’t run this simulation without resulting in errors.
I quickly looked at your case and it seems like the problem you have is not connected with porous region. The problem is in the BC set up - the better options for your case, i believe, is to choose “wall function” and “zeroGradient” at the walls boundaries. This way setup should be more stable.
Also I think your mesh is not optimal (through it’s not crucial problem, i guess) - you can make it a little corser but with the boundary layer in it. This way it will be faster to calculate and more robust for numerical scheme. To look up how to do this kind of mesh you can check out almost any public project of flow in pipe simulatiom, for example in this tutorial.
When you get a good result without porous media, you can easily add it to see if it brings new problems or not.
Sorry I can’t change your project to help - I ran out of my quota, so I hope my advice here will be helpfull enough.
I set up your simulation the way you can see in this project. As you can see, I’ve created a coarse mesh with boundary layer + changed boundary conditions at walls and it works pretty wel now.
A couple of things I’d like to mention regarding you project - first of all you have a pretty fast flowing air,so you should choose “turbulent” simulation (as you did in simulation 2 and simulation 3), not a laminar (as you did in simulation 1). Usually before CFD simulation you calculate Reynolds number for your case to be sure if you choose laminar or turbulent simulation set up.
The second thing is that if you simulate isothermal flow (without temperature change within the domain) you can put “zeroGradinet” BC for temperautre at the wall. It means they are not able to transfer heat and this is the most robust set up in this case.
The third one is that you should’t use negative constants in porous media set up as you alredy have “minus” sign in D-F equation (see my first post in this thread).
Sorry to be probably too much into details, but I just wanted to share points I noticed during your case configuration.
Just to finish what we discussed here: the specific example how to find out what numbers exactly you put in a porous media properties is the following: the darcy eq. in OpenFOAM (eq. 3 here) you put in correspondance with semi-emperical data here - slide 207 here - eq (6.4-14).
This gives you the following equations:
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).
First of all I’m sorry for the absence, and thank you for your review on my simulation. I really appreciated!
Regarding your last post, about the specific example on how to find the D-F numbers, I took a look and it seems really interesting. However I don’t have some of the important data about the porous zone geometry I’m trying to imitate in these simulations. For instance, I don’t have the mean particles diameter (D) nor the porosity (eps). All the data I have is the pressure drop per mass flow and the basic dimensions of the radiator, like frontal area, length, depth and height. With these I can estimate the flow velocity in the core of the radiator and plot a Pressure Drop x Flow Velocity graph.
Checking these equations I noticed that there are similar equations in that material I first referenced to, in this ANSYS TUTORIAL LINK.
If you check equations 7.19-17 and 7.19-18 you will see the similarity. Like I said before, the problem is I don’t have those parameters (D and eps), however the therms alpha and C2 I managed to find in the way specified in that same web page in equations 7.19-23 to 7.19-27, with the Pressure Drop and Flow Velocity data.
That method gave me a negative Darcy parameter, which I though it was OK because in the example this same coefficient is also negative. Now I’m not sure if it is correct.
Thank you for your attention @varsey, I’ll keep trying. Once I get it right I’ll share here the procedures I took.
great resources - especially the slide deck / book. I didn’t know that on slideshare they have entire books! Will test this as well. I think such computations should be built into SimScale. What would be from your perspective a more convenient workflow to define porous media within SimScale?
To be honest, I dont see anything to improve here at the moment, since what we are having now in the means of porous media configuration in Simscale are the native OpenFOAM tools with it’s pros and cons.
I’ll let you know if figure out the way to improve this aspect.
@ibrito
Hi.
I have a problem at hand for which I think I need to simulate as flow through porous media.
Could you please tell me how did you start-off with this simulation (the one you have posted)?
Thank you for the calculation formulas for the Darcy/Forchheimer coefficients.
I am just wondering about the eps^2 term in the calculation of the Darcy coefficient. Shouldn’t this not be eps^3 taking into account the Ergun equation and the ANSYS TUTORIAL LINK by ibrito?
Hi there!
This is a really useful post about the Porous media settings.
About the Darcy-Forchheimer formula I have found another mistype about the f coefficient:
I want to ask about the porosity value how it is included in simscale ?
It is not clear for me how to include values for porosity in simulation for porous media
or the flow resistance is included as source terms without any changes in the momentum equation ???as some terms in the momentum equation for flow in porous media include porosity
