Simulation Forums

Find Simulation answers, share expertise, and connect with your peers

Simulation CFD


Creating 100 micron filter

140 Views, 14 Replies
02/07/2018 9:40 AM

Hi.

Just as the title says im having trouble understanding how to best create a filter/resistance material that has approx 100 micron size mesh.
The filter has 30% open area, so we came up with this;
far.jpg

What we don't understand is how to mesh the filter, so that it will imitate the true filter openings. My understanding of FAR is limited. Any suggestions on how to create this filter? 


27848299_10159860979135401_1732889254_n.pngweave.jpg
Many thanks,
Isak


Report Inappropriate Content
Message 1 of 14 ( Views: 140 )

Re: Creating 100 micron filter

02/07/2018 10:50 AM

What you have looks sensible.

 

Two things to be aware of though:

 

  1. Use Advection Scheme 5 with a volumetric resistance (Solve-Solution Control-Advection)
  2. Start with at least 5-6 elements through its thickness and use a uniform mesh to be sure that this is applied all over
    • How thick is this filter and how large is the overall model? Just to be sure that recommendation is not too crazy

Thanks,

Jon


Report Inappropriate Content
Message 2 of 14 ( Views: 129 )

Re: Creating 100 micron filter

02/07/2018 11:09 AM
Thanks.

1. We use Advection Scheme 5

2. Yes, we will use minimum 5-6 elements through its thickness and uniform mesh.
The filer is 0.1 mm thick. the overall model is varies with design, from about 18-30 mm high.
dear john.jpg
The issue is with the size of the holes(mesh of filter)? I mean, the filters with 100->about 400 micron has all 30% opening, but they look very different.
How would i mesh the filter to make it behave like the 100 micron one? or is there an other way to configure this?

Thanks,
Isak


 


Report Inappropriate Content
Message 3 of 14 ( Views: 125 )

Re: Creating 100 micron filter

02/07/2018 12:17 PM

Thank you for sharing.

 

I have a couple more things to share then I think!

 

You could consider using a surface material as a resistance, although then you would need to use ADV1.

To break it up into regions, how are the holes distributed? Could you simply have several resistances with different FAR's applied to each? 

 

Thanks,
Jon


Report Inappropriate Content
Message 4 of 14 ( Views: 116 )

Re: Creating 100 micron filter

02/07/2018 12:50 PM

 


We haven't looked into using surface material as a resistance. Even more unsure about using ADV1, wouldn't that complicate the solutions even more? i will read about ADV1 and surface material, but i feel we are very close with the design as it is now. But if the surface material resistance break it up into regions, maybe it's the way to go. The holes are uniformly distributed, as the first post show.

jon jo jo.jpg

The idea is to have several(0-6) 0.1mm thick filters with approx 1mm room between them to stabilize the flow(make it uniformly exit in z-direction(flow direction)) . As for now we have 1 thick filter (1mm) just for testing.


What confuses us is how to create this filter (except we know the FAR, hole size and wire diameter).
As you can see in the picture, the hole openings and wire diameter differentiate, but the FAR stays about the same 30-31 %. 
Creating a filter then with FAR at 0.3 could in my understanding be any of those different filters (120-> 300 micron).

thanks,
Isak


Report Inappropriate Content
Message 5 of 14 ( Views: 114 )

Re: Creating 100 micron filter

02/07/2018 2:12 PM

Can I ask a dumb question? Is this axisymmetric? If so, you could take a small section and  run in 2D axisymmetric (super fast and with loads of mesh!)

 

Or perhaps take a small slice and really model the filter?

 

Remember that CFD is not actually modelling this filter, it is only approximating. So if you really need to be sure how many you need before the flow is straight, it might be a good experiment to model it as a test?


Report Inappropriate Content
Message 6 of 14 ( Views: 104 )

Re: Creating 100 micron filter

02/07/2018 4:40 PM

I'm not sure if it's axisymmetric. I don't think it is. I'm confused and tired. Maybe if i upload the .cfz someone can answer this. Would be nice to have a lot of mesh.

We are doing the test on our filter. with just a tube and the filter.

thanks
Isak

Report Inappropriate Content
Message 7 of 14 ( Views: 101 )

Re: Creating 100 micron filter

02/08/2018 7:27 AM

You are right, the holes mean that this is not axisymmetric. You could still run a 1/2 model at least :)

 

I also still cannot recommend all of those P=0 outlets, sorry ;)


Report Inappropriate Content
Message 8 of 14 ( Views: 93 )

Re: Creating 100 micron filter

02/08/2018 8:17 AM

I also still cannot recommend all of those P=0 outlets, sorry ;)


Alright, new day! How else would i recreate a "air surrounding my welding pistol? there are better ways? 

And we will run with the cloud system, so i guess we can have alot of mesh anyway :)

Thanks,
Isak


Report Inappropriate Content
Message 9 of 14 ( Views: 89 )

Re: Creating 100 micron filter

02/08/2018 11:24 AM

Tried 2d simulations of a patch sketch. uploaded as .sat and was a nice "plate" put inlet as flow rate and outlet as P=0, solver didnt solve. am i missing something about the 2d simulation?

 


Report Inappropriate Content
Message 10 of 14 ( Views: 78 )

Re: Creating 100 micron filter

02/08/2018 12:04 PM

In the bullet tutorial i should select axisymmetric in x, but there is no option for this that i can find. the only option is "edit"


2dd.jpg


Report Inappropriate Content
Message 11 of 14 ( Views: 73 )

Re: Creating 100 micron filter

02/08/2018 1:41 PM

OK, to answer in a bit of order :)

 

Alright, new day! How else would i recreate a "air surrounding my welding pistol? there are better ways? 

I would simply have a larger domain with a P=0 on the top

 

 

Tried 2d simulations of a patch sketch. uploaded as .sat and was a nice "plate" put inlet as flow rate and outlet as P=0, solver didnt solve. am i missing something about the 2d simulation?

The sketch needs to be in the x-y plane in CAD and in alignment with the axis also as it really revolves around the axes. Then, you should have the option once you start a new model. Does that work?

 

I am not totally sure that 2D can work though as you have those small horizontal pipes? Good as a quick test for sure.

 

Thanks,

Jon

 


Report Inappropriate Content
Message 12 of 14 ( Views: 62 )

Re: Creating 100 micron filter

02/09/2018 8:46 AM

Having a larger area would seem like the solutions yes. We will probably go back to that, thanks.

About the 2d,
It was drawn in xy plane in inventor. 
xy.jpg
tried again, but its not very important. was just for learning. but weird i don't get the options.

Anyway. i Think we sorta solved the 100 micron filter here. Many thanks

Isak


Report Inappropriate Content
Message 13 of 14 ( Views: 51 )

Re: Creating 100 micron filter

02/09/2018 9:02 AM

Great, thanks for the update.

 

Let us know if you wish to receive a little help on the 2D at any point.

Might you be able to mark a post above as the solution if it provided you with an answer?

 

Thanks and have a lovely weekend,

Jon


Report Inappropriate Content
Message 14 of 14 ( Views: 49 )