So I have to model a porous wind barrier in CFD simulation software that would stop the majority of dust from entering but also allows air to go in. I have decided to start with a 1D flow assumption with unidirectional porosity. From some literature search, I got the required porosity to be around 45%. I am stuck with an estimate of the permeability. I am simulating it numerically so I don't have experimental data. I have taken a material that won't deform significantly, So based on geometry(I have taken the pores to be rectangular slits of 0.3mm thickness), How can I get an estimate of the viscosity. Also, will compressibility effects play a role at naturally occurring wind velocities? I also need to estimate the velocity of air going across the wall
Please suggest an approach on how to approach the problem. Getting some literature references on this would be helpful
Hey Saurav, I have some experience with a similar type of simulation.
In the past I had to simulate a porous material which I didn't have experimental data for.
In my case, it was a tube fin heat exchanger where I needed to replace the fins/tubes with a simple porous model.
The easiest way to do this would be to take just a section of your porous CAD model and simulate it over a range of different flow rates. For each flow rate note down the Pressure Drop through your model.
This will give you the pressure loss curve of the porous. If you expect it to have different porosity/permeability vs flow-direction, then you should run the above test in all three directions (x,y,z)
Then you can directly utilize the pressure loss curve as an input to a simple porous model like its done here
https://www.simscale.com/docs/simulation-setup/advanced-concepts/porous-media/#pressure-loss-curve
or alternatively, be able to estimate the permeability by, I believe, a 2nd order curve fitting on your simulation data (flow rate vs pressure drop)
This article generally explains the different methods
https://www.simscale.com/docs/simulation-setup/advanced-concepts/porous-media/
and there is also a very extensive discussion taking place here
https://www.simscale.com/forum/t/porous-media-simulation-guide-for-fsae-radiator/87503
Hope this helps,
Good luck with your simulations!
Thank you. I will look into it. Do I need to have decent estimates of viscous and inertial resistances to start with for it to converge?
You are welcome!
In the method I'm suggesting all you need is to run a simple fluid flow simulation, for several flow rates, through your perforated CAD model (without any porous conditions set).
This will give you the pressure loss curve which you can then use to build a porosity model (isotropic or anisotropic)
This method is described here in more detail
https://www.simscale.com/forum/t/how-to-predict-the-alpha-and-beta-values-for-the-fixed-coefficients-porous-media/96572
It pretty much depends on what are the available option in the software you are using, but I believe you should pretty much find this method in most of the CFD tools.
Hope this helps,
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