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Unsimetric analysis in a symetric part?

15 REPLIES 15
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Message 1 of 16
DelNegro
550 Views, 15 Replies

Unsimetric analysis in a symetric part?

I am trying to create a cone top optimize the flow to a filter.   it is essentially a cone with a screen at the end just before the filter.  When I run the analysis, it shows the flow going off to one side.  Is this even possible?  I'm not really convinced that this would happen.

 

Any opinions?

15 REPLIES 15
Message 2 of 16
Jon.Wilde
in reply to: DelNegro

Could you provide a simple sketch including your Boundary Conditions too please?

Chances are, if this is set up correctly, you do not have sufficient mesh - so an image showing the mesh on a cut-plane would also be very useful if possible.

 

Kind regards,

Jon

Message 3 of 16
DelNegro
in reply to: Jon.Wilde

I had added an image but it appears to have not uploaded.  I'll try again.

 

As far as boundary conditions...  I have 10LPM inlet and 0 PSI outlet.  The thin part at the large end of the cone is a 10% open area screen.

 

T

Message 4 of 16
DelNegro
in reply to: DelNegro

 

SP32-20130919-164523.jpg

SP32-20130920-084938.jpg

Message 5 of 16
Jon.Wilde
in reply to: DelNegro

I suggest refining your mesh - also could you share the resistance settings? Do you just have FAR or 0.1 in each of the 3 directions? If so, that is OK.

 

The ideal here is to run this as a 2D axisymmetric analysis, lots of mesh and far faster!

Message 6 of 16
DelNegro
in reply to: Jon.Wilde

I have a FAR of 0.1 allowing flow only in the K direction.

 

I am unfamiliar how to run a 2D simulation.  Can you direct me to some help on that?

Message 7 of 16
Jon.Wilde
in reply to: DelNegro

Sure, take a look in the help and Wiki but the basics are:

 

Sketch a 2D slice of your model on the x-y plane (this is important) - use either the x or y axes for the actual part axis as you are going rotate around as you will use this in CFD.

Then when in CFD you apply everything the same but volumes are now surfaces and surfaces are now edges.

Also be sure to select 2D axisymmetric in the top left (Units) part of the screen.

 

Then run it. You have the option here for a far better mesh and hugely reduced runtimes.

The downside is that you cannot use traces as you have here - the results are strictly 2 dimensional.

 

Does that help?

 

Thanks,

Jon

Message 8 of 16
DelNegro
in reply to: Jon.Wilde

Do I need to sketch each part in the cross-section?  Also  If you'll notice how I have the 'filter' on the left side (close-up below).  Because our filter is essentially a bundle of straws, we section it this way to prohibit flow in the non-K direction.  Would I need to create the individuatl sections of the filter here too?

SP32-20130920-092834.jpg

Message 9 of 16
DelNegro
in reply to: DelNegro

Also, do I create the sketch within my 3D model or as a separate file alltogether?
Message 10 of 16
Jon.Wilde
in reply to: DelNegro

You can sketch it is a new part within the assembly but then just launch it on its own.

You should be able to change the resistance settings to prevent flow in the directions you do not wish it to travel.

Message 11 of 16
DelNegro
in reply to: Jon.Wilde

OK. I will give that a try. Just so you know, we set our filter up as a FAR reseistance as well. Even though you can set the flow in a FAR resistance to only be in the K-direction, there is a natural disipation in the non-K directions that occurs in the resistance model that does not provide correct results for us. This is why we section it. i.e. if I provide flow to only half of my filter at the inlet, I will still see flow exiting the entire filter at the other end. This is not the case for our filters (think of the straws).
Message 12 of 16
DelNegro
in reply to: DelNegro

I tried loading a sketch and got an error that the Granite kernel could not launch 2D geometry and to try the Mechanica launch method.  When I do this, it actually doesn't launch at all.  Any ideas?

Message 13 of 16
DelNegro
in reply to: DelNegro

Could you possibly direct me to the section in the manual that explains 2D analysis?
Message 14 of 16
apolo_vanderberg
in reply to: DelNegro

Tony,

I agree here with Jon. Knowing some of the geometry you've dealt with in the past, you might be able to look at portions from a 2D axisymmetric aspect. However if you were going to run in 3D (quarter/half symmetry, or full model) I would also suggest refining the mesh in the cone as you can see that teh flow field is following the coarser elements and as you refine you'll start to see tht the results become more symmetric.
I would also encourage you to run ADV5 (in 2014/2013) or ADV2 (otherwise) as it will help with the results in applications like this.

Message 15 of 16
DelNegro
in reply to: apolo_vanderberg

Apolo,



Thanx for the reply. I am unfamiliar with ADV5 or ADV2. Can you
elaborate? Also, I am still on CFDesign 2010...
Message 16 of 16

ADV5/2 refer to advection schemes (found under the Solve dialog - Solution Control - Advection)
In 2010 we only had ADV2, which would be a good start for this model. If you were to update to 2013+ you would have the option of ADV5 which is a newer/improved version of ADV2

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