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Active Member
andrew.lesiecki
Posts: 9
Registered: ‎10-24-2013
Accepted Solution

Unable to run CFD with regions

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11-05-2013 05:23 AM

Hello,

I am a student and i have been using Autodesk CFD 13 for about a year now and have become fairly comfortable with it. When the 2014 version came out i downloaded it along with the 360 pro version. The cloud version I would always get an error that sai "the server has exited unexpectedly" I was able to run a very simple cfd but as soon as I applied any mesh regions to it it wouldn't work. With the normal version of 14 anytime I added a region to it, it would tell me I dont have enough RAM which isnt the case but i cleared some room anyway and now it just wont run it will just sit there after it surfaces meshes.

 

So I kind of gave up on the 2014 versions since I dont have the time to figure them out and decided to go back to 2013 that i know how to work. Well now I can't get the 2013 to work anytime i add a mesh region to it. I have read through the forums and it suggest it to be on the C drive and both 2014 versions were but my  2013 is on an external harddrive which has worked just fine for the past year.

 

Attatched is the .cfz of the simulation I was trying to run in 2013. It says my file is too large to attatch.

 

Thanks,

Andrew

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Product Support
wildej
Posts: 725
Registered: ‎08-25-2011

Re: Unable to run CFD with regions

11-05-2013 06:03 AM in reply to: andrew.lesiecki

Hi Andrew, 

 

OK, so to be clear, you can run 2013 and 2014 but when you add a region it does not work?
It is entirely possible you are running out of RAM, what is the mesh estimate before and after adding the region? We need about  2GB of RAM for each million elements. If you are running on 360, you cannot change the available RAM as this is all remote.

As an aside, you cannot make space to increase RAM, that would be hard drive space, which is not the same. 

 

I am happy to take a look at the file, could you pop it into 360 or Dropbox and share a link?

 

Kind regards,

Jon

 



Jon Wilde
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Active Member
andrew.lesiecki
Posts: 9
Registered: ‎10-24-2013

Re: Unable to run CFD with regions

11-05-2013 08:27 AM in reply to: wildej

Yes both of them worked and then when I add a region it does not work.

My system has 16GB of RAM and a 60,000 element mesh is failing, it was 20,000 elements before the regions. I have previously done up to 3 million elements.

2014 is installed on a SSD, which was close to full and I made some space on that (not RAM)

2013 is installed on an internal HDD.

 

Here is the link to the most recent that failed on 2013.

https://www.dropbox.com/s/9i24x4k8u5zph9m/16.4.6_1_support.cfz 

 

Thanks,

Andrew

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Product Support
wildej
Posts: 725
Registered: ‎08-25-2011

Re: Unable to run CFD with regions

11-05-2013 08:56 AM in reply to: andrew.lesiecki

Hi Andrew,

 

You should be able to run 8-10m elements on your machine I would have thought.


I cannot open this file though, it gives an error. Could you try saving a CFZ from the interface and re-sharing? You will find it under 'Save Share File'

 

Kind regards,

Jon



Jon Wilde
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Active Member
andrew.lesiecki
Posts: 9
Registered: ‎10-24-2013

Re: Unable to run CFD with regions

11-05-2013 10:34 AM in reply to: wildej

Jon, 

Please let me know if this works. It was saved as a share file with the 'everything' option checked.

https://www.dropbox.com/s/7w5rvos6ws6vadc/16-4-6_Share.cfz

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Product Support
wildej
Posts: 725
Registered: ‎08-25-2011

Re: Unable to run CFD with regions

11-06-2013 01:45 AM in reply to: andrew.lesiecki

Hi Andrew,

 

This opens fine, thanks.

 

I am surprised you are not running in 2D though, is there a reason for using 3D?

Looking at the mesh regions, you just have too much mesh for your PC to handle - this is not reflected in the approximate element count (regions sometimes are not) but this would easily run into many millions.

Refine the mesh gradually, run 0 iterations or preview the mesh and see what the real mesh count is as you progress.

 

You should also refine the mesh on the outer air - right now you have areas with just one element from one side to the other, you need 4-5 really.

 

Kind regards,

Jon



Jon Wilde
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Active Member
andrew.lesiecki
Posts: 9
Registered: ‎10-24-2013

Re: Unable to run CFD with regions

11-12-2013 06:39 AM in reply to: andrew.lesiecki

Jon,

 

Thank you for the help. I did not realize that when I was looking at approximate element count that it was not counting for everything. Now looking at the element after meshing this makes much more sense. I had been running 3D because that is what I first started with to get affects of sideboard and full vehicle integration but for now I switched to 2D to do just the profiles and it has been running much quicker.

 

Only problem now is that with the 2D I have an area with accelerating velocity near the back/bottom corner of the box. Have tried a few different setting and am unable to get rid of it. Any suggestions? I have attached a screen shot of the velocity and the mesh/boundary conditions.

 

Thanks,

 

Andrew

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Product Support
wildej
Posts: 725
Registered: ‎08-25-2011

Re: Unable to run CFD with regions

11-12-2013 07:19 AM in reply to: andrew.lesiecki

Hi Andrew,

 

I am glad you switched to 2D, good approach.

 

What you probably need to do here is extend the outlet, I would be running about 5x this length or so. Ideally there should be no recirculation over the outlet BC and just nice laminar flow.

 

Kind regards,

Jon



Jon Wilde
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OmkarJ
Posts: 406
Registered: ‎10-02-2012

Re: Unable to run CFD with regions

11-12-2013 08:52 AM in reply to: andrew.lesiecki

Additionally, also make sure you have run for enough iterations, by monitoring few points at key locations and ensurign flat monitors. The larger unphysical velocities at unexpexted regions often indicate that the solution is still propagating, and this process may be slow for fine meshes with pseudo transient solver on (Intelligent Solution Control). 

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Product Support
Royce_adsk
Posts: 554
Registered: ‎08-24-2011

Re: Unable to run CFD with regions

11-12-2013 09:31 AM in reply to: OmkarJ

I agree with OJ. No need to extend your outlet, you really just need to run your analysis much longer and that should clean up the high velocity at the bottom.

 

Many times you will need to turn on the convergence checker and then make a manual assessment of convergence for these external air domain analysis.



Royce Abel
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