[MarkoP]

Hi all,

I have a rather (I'd say) simple system. Heatsink with 12 small plates representing diodes or IGBTs and 3 baseplates representing baseplates of power modules for power electronics. I am trying to simulate cooling of this system with forced air cooling.

Mesh file is around 20MB large and it has 200k elements. The CFX-Pre reacts SERIOUSLY slow. Opening the file took around 20-30 mins at least as I wasn't near my laptop when it opened. Each change, adding domain or subdomain takes 10-15 minutes.

I am using a machine with i7 processor and 16GB RAM and Intel HD Graphics 620. Task Manager indicates that CFX used around 1.5GB of RAM.

Anybody had similar issues or know what is happening and how it can be fixed?

I am using a shared academic license from my university and I'm connected through VPN to my university network, just in case this might be an issue.

[ghorrocks]

Have you checked your virus checker is not killing it?

[MarkoP]

Originally Posted by ghorrocks

Have you checked your virus checker is not killing it?

Nope, have no idea how to do this. How do I do it?

I am a fairly basic user of Ansys, just need it for a quick simulation.

[ghorrocks]

Open the virus checker control panel and turn it off or pause it. Then try using CFX-Pre and see if it works as expected again. It could be the virus checker scanning every single CFX-Pre input and output file in detail, or it could be conducting a scheduled scan. A scheduled scan has nothing to do with CFX-Pre, but all applications can slow down when this happens. Check both options as either of them could cripple applications like CFX-Pre.

You might also need to consider pausing the MS Windows file search indexing gizmo as it can also cripple applications when it is running (if you are on Windows). Also check any other applications you have running which potentially scans a wide range of files.

[evcelica]

What is your working directory? Meaning where is the file saved? If not on a local drive on the machine, it will be very slow. Are you working off a remote drive, or flash drive?

[urosgrivc]

Yes CFX has huge problems with this:
It has been even worse in the past though.

It only happens in CHT simulations, where yor geometry usualy has large number of surfaces in contact between bodies (reducing this number vith virtual topology does work but is not the best solution).
CFX somehow tries to autodetect them and because of large number of faces fails badly. It is a perfect program otherwise it just has this problem. And these proceses of opening preprocesing and postporocesing are all done in serial so having a procesor vith a lot of cores is actualy a disadvantage, becouse of, them usualy having lower frequency.
i7 is I think the most apropriate procesor for pre and post procesing no 28 core xeon monster will match it in single thread operations so that is definetly not the problem.

1) The only real solution to this problem I have found is this: (and this is not a joke) works perfectly ewery time and when you get used to it you are able to do it in les than a minute which is beter than waiting for half an hour and than when you change something another 15min goes past eweritime:

Move your solid body in design modeler out from the fluid domain, like for a fixed distance in one direction so they dont touch.
(this way the bodies wont touch and there will be no conections for cfx to find) even if you disable domain checking and that stuf it still doesent vork throuhg the change of options. I have tried ewerithing to solve this problem belive me

Than in CFX it is extremly simple to put the solid domain back where it should be in the first place. In the tree if you click on domain you can move it. by some amount in some direction.

Now you can proceed normaly..

2) Deactivate phisics checking and all that automatic stuf under options, but that wont make the opening times much better. it will just work a litle quicker.

Have fun