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j-avdeev August 20, 2012 03:59

Modeling of particle absorption in air filter in CFX

I am trying to setup absorption efficiency of air filter. I have particles of different size and want setup, that air filter pass for example 1% of big particles, 2% of medium particles and 3% of small particles (filter retains 99% of big, 98% of medium and 97% of small particles).

I can find corresponding options (almost) for this case - in "wall" object, but can't find this in "interface" object and in porous media.

Is it possible to reach my goal with using interface? Or I have to use something like "user defined functions"? Or maybe it is possible with walls (I need that particles pass through surface)?

Thank you.

ghorrocks August 20, 2012 06:01

If you are doing this with Lagrangian particle tracking you will need a fortran sub routine to do this. If you are doing this with a Eularian model it can be done with a source term (I think).

j-avdeev August 20, 2012 06:27

ghorrocks, thank for your rapid answer.

Also can you tell - is it possible to solve this problem with using CFX Expression Language (CEL) or fortran only?

And if it will on fortran - can you show something for example? Or give a link, where I can find something close to my case.

ghorrocks August 20, 2012 06:46

If you are doing a Eularian this might be able to be done by a CEL expression.

But for Lagrangian particle tracking you will need fortran. I do not have an example to hand, but the documentation includes some examples of fortran for particle tracking. I think it is in the CFX-Pre manual.

j-avdeev August 20, 2012 07:37

Thank you, Glenn.

Also can you tell - where can I insert fortran code for interface? For wall - exist separate window, but I can not find same for interface.

Felggv August 20, 2012 10:40


It's kinda tricky to link FORTRAN routines with CFX. Many people had asked about it before, you can search for it later!

Revise the concept of what you're trying to do. CEL supports if statements besides another basic things (look at the manual) it's very useful and maybe you won't even need to use FORTRAN.

Good luck

_srs_ October 28, 2015 11:19

Hello j-avdeev,

did you find a solution for your problem?

I want to simulate the absorption of dust in a filter. The filter itself is set up as porous medium. I have air as continous fluid an use the Lagrangian particle tracking.

Did you use fortran or is there any other way to simulate the accumulation of dust especially in a porous medium?

Thank you

j-avdeev October 31, 2015 08:25

Hello, _srs_
It was too difficult for me to make through routines.
So I solve it in 2 steps:
1. Made simulation of the porous medium without dust - the purpose of the calculation to estimate the average length of the passage of dust particles inside the material.
2. Further, was analytically calculated number of particles of a given diameter that can pass a given length, of the probability of the particle retention in the material.

_srs_ November 2, 2015 07:29

Thanks a lot for your answer j-avdeev

I have some more questions about your solution.

Step 1:
How did you simulate the averrage passage of dust particles in the material without dust?

Step 2:
Did you simulate the particle retention in the porous medium in a final step (if yes: how? I didīt find a way to model the particle absorption)

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