CFX-Pre Loading Problems big Model

marcel_jay · January 7, 2016, 12:05

Hello and Happy new year,

I am trying to do a CHT-simulation through a complex model and there seems to be a problem with the pre-engine handling it.
I used a coarse mesh to do some testings so it "only" has a about 3M elements, in an accurate mesh it would be about 14M - I will try to use symmetry in meshing later on, but I'm not sure if that makes the setup more complicated (periodical interface on different domains).

So the model consists of 28 solid domains and 1 fluid. There are about 85 connections, most of them very important for the heat transfer.
When I start pre, nothing would happen - it will show 0% in the lower right corner for at least half an hour.

The computer I'm using has a Xeon E5-2687W with 128 GB Ram in it.

It am not sure, but it probably would take way too long to create domains and interfaces manually, especially as I think it's too much effort to do all the proper named selections.

So does anyone encountered an issue like this before?
I'd be thankful for some advice.

Cheers
Marcel

ghorrocks · January 7, 2016, 19:52

If you mean to ask "have you seen the software runs really slow when I do a big model?", then yes, I have seen this many times. Your mesh is pretty big (14M) and has lots of interfaces so the interface detection thing and other mesh verification stuff is going to take a long time.

I would turn the automatic interface detection off and see if that speeds things up. If that works fine and you want to use automatic interface detection then your best option is to leave it even longer for it to run.

marcel_jay · January 12, 2016, 10:06

Thank you for your advice.
It seems to me though that CFX is still struggling.

When loading the model without automatic domain/interface generation, the geometry was imported successfully after quite a while (>30min as I left it loading over night). The Mesh was so coarse it only had about 400k elements.

Then, once I inserted one single domain, the programm again froze (updating boundary condition marker rendering, currently for more then 15minutes and I'm still waiting).

I guess this is not a good workflow considering the fact that I'll have more than 20 Domains.
Would you know if the "Default Boundary" option or any other of the marked ones in the attached image might slow the process down that hard?

Cheers
Marcel

ghorrocks · January 12, 2016, 18:20

A simple 400k node mesh should load in a few seconds. If this took >30min then something is very wrong. Are you using a reasonably modern computer? Does the hard drive have enough free space? Is the hard drive fragmented to oblivion? Is a virus checker crippling it? Are your motherbord, bios and drivers up to date? Are other users on the machine at the same time?

marcel_jay · January 14, 2016, 08:43

I think the computer as a factor can be eliminated as the program lags both on my local i5,8gb and on the rack with a xeon,128gb ram.

The question is really why CFX has trouble loading a model when Meshing and Designmodeler can load and process it easily.

What I will try now is to supress parts of the assembly to see if it's a specific body that causes the trouble. But I never encountered such an issue in former projects.

ghorrocks · January 14, 2016, 18:01

As I said, CFX can normally load a 400k mesh in seconds. I would not be so sure your computer is fine. BIOS, motherboards and hard disk drivers are all things which have crippled computers for me before - you really should check these. Just because it is a modern CPU does not mean everything else is set up correctly.

And don't forget antivirus software. This is the most common source of crippled computers.

monkey1 · January 15, 2016, 04:50

Sounds really weird.
Even if Glenn thinks a 14M mesh is big...I usually have between 10M and 16M Elements and on a i7 2,8GHz Quadcore with 16 gb RAM it loads fine and within less than 10 min.
But I never had more than maybe 6 Domains that would have Interfaces to each other...
Dunno if it might be a problem but seeing that you are located in Berlin...are you sure that your file paths and names do NOT contain any special characters like Ä,Ö,Ü?
Ansys is unable to deal with that symbols if exsitant in ANY part of the full path....

Oh and if you are using ICEM as a mesher...exporting the mesh as binary file instead of ascii would reduce the file size significantly and speed up the loading in pre a bit...

Have you checked your RAM usage during the Load process?

marcel_jay · February 11, 2016, 08:46

I isolated the problematic geometry, which is a cooling fan with about 80 blades at a 80mm outer diameter. So there was only 1 interface left.
I even extraced the silhouette geometry and remodeled the part in NX10 and afterwards created an enclosure in DesignModeler. The problem still persists.
I sent the geometry to our supporting partner CADFEM but so far they have not come to an conclusion what causes the issue.
There seems to be some kind of geometry that is totally fine in meshing and designmodeler but not in CFX-Pre. Maybe it's some kind of bug.

Cheers

marcel_jay · February 25, 2016, 09:15

The main issue that CFX has in such a case are too many connectivities because of a high numer of faces on one body (~600).

There is a workaround though: Export the mesh as fluent, import it in ICEM CFD and export it for CFX again. The connectivities are now all gone and contact regions have been defined. The model loads quickly.

hereford_jon · April 10, 2017, 05:55

I have the same issue with a CHT model in CFX 18.0 I have tried it on several machines to rule out machine issues. I suspect that it is a part with many faces (a chassis casting) which is causing the problem. Will try this workaround. Again the geometry is fine in Spaceclaim and Meshing, just CFX-Pre slowing things down massively.

urosgrivc · April 11, 2017, 02:03

I think that the biggest problem in cfxpre loading time is caused by automatic interface detection in cfxpre. I have geometries composed up to 8kfaces and ~13Mnodes by disabeling auto detection the time was reduced by 98% (from 2h to 3min) for a CHT simulation of a brake disc. And the more the faces the longer the loading time.
So I newer ewer use auto detection in my simulations + disabeled phisics valiadation and all that automatic detection stuf.
I had huge problems in the past the cfx pre would go into auto phisics valiadation mode while i was seting up the problem, and than I would wait 2h until it came back so i had to force close the cfx a lot of times during the cfxpre problem set up (furtunatley somehow no data is lost when forceclosing cfx pre so thumbs up for that).

I dont hawe eny problems now with all that disabled.

-Disable strict tipe domain checking
-Disable auto phisics valiadation
-Dont show interface boundaries

Dont let cfx do work automaticly for you it is slow and you dont need it.

Duke711 · December 22, 2018, 19:40

Big Model:

7500 Faces
45 M Cell

................

without a graphic card:

2 hours

with 1080 TI

3 mins.

CFX display all faces, you need a good graphic card

January 7, 2016, 12:05	CFX-Pre Loading Problems big Model	#1
marcel_jay Member Marcel Jay Join Date: Jun 2014 Location: Berlin Posts: 52 Rep Power: 12	Hello and Happy new year, I am trying to do a CHT-simulation through a complex model and there seems to be a problem with the pre-engine handling it. I used a coarse mesh to do some testings so it "only" has a about 3M elements, in an accurate mesh it would be about 14M - I will try to use symmetry in meshing later on, but I'm not sure if that makes the setup more complicated (periodical interface on different domains). So the model consists of 28 solid domains and 1 fluid. There are about 85 connections, most of them very important for the heat transfer. When I start pre, nothing would happen - it will show 0% in the lower right corner for at least half an hour. The computer I'm using has a Xeon E5-2687W with 128 GB Ram in it. It am not sure, but it probably would take way too long to create domains and interfaces manually, especially as I think it's too much effort to do all the proper named selections. So does anyone encountered an issue like this before? I'd be thankful for some advice. Cheers Marcel

February 25, 2016, 09:15	[solved]	#9
marcel_jay Member Marcel Jay Join Date: Jun 2014 Location: Berlin Posts: 52 Rep Power: 12	The main issue that CFX has in such a case are too many connectivities because of a high numer of faces on one body (~600). There is a workaround though: Export the mesh as fluent, import it in ICEM CFD and export it for CFX again. The connectivities are now all gone and contact regions have been defined. The model loads quickly. hereford_jon and kubawin like this.

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January 7, 2016, 19:52		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	If you mean to ask "have you seen the software runs really slow when I do a big model?", then yes, I have seen this many times. Your mesh is pretty big (14M) and has lots of interfaces so the interface detection thing and other mesh verification stuff is going to take a long time. I would turn the automatic interface detection off and see if that speeds things up. If that works fine and you want to use automatic interface detection then your best option is to leave it even longer for it to run.

January 12, 2016, 18:20		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	A simple 400k node mesh should load in a few seconds. If this took >30min then something is very wrong. Are you using a reasonably modern computer? Does the hard drive have enough free space? Is the hard drive fragmented to oblivion? Is a virus checker crippling it? Are your motherbord, bios and drivers up to date? Are other users on the machine at the same time?

January 14, 2016, 08:43		#5
marcel_jay Member Marcel Jay Join Date: Jun 2014 Location: Berlin Posts: 52 Rep Power: 12	I think the computer as a factor can be eliminated as the program lags both on my local i5,8gb and on the rack with a xeon,128gb ram. The question is really why CFX has trouble loading a model when Meshing and Designmodeler can load and process it easily. What I will try now is to supress parts of the assembly to see if it's a specific body that causes the trouble. But I never encountered such an issue in former projects.

January 14, 2016, 18:01		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	As I said, CFX can normally load a 400k mesh in seconds. I would not be so sure your computer is fine. BIOS, motherboards and hard disk drivers are all things which have crippled computers for me before - you really should check these. Just because it is a modern CPU does not mean everything else is set up correctly. And don't forget antivirus software. This is the most common source of crippled computers.

January 15, 2016, 04:50		#7
monkey1 Senior Member Join Date: Jul 2011 Location: Berlin, Germany Posts: 173 Rep Power: 15	Sounds really weird. Even if Glenn thinks a 14M mesh is big...I usually have between 10M and 16M Elements and on a i7 2,8GHz Quadcore with 16 gb RAM it loads fine and within less than 10 min. But I never had more than maybe 6 Domains that would have Interfaces to each other... Dunno if it might be a problem but seeing that you are located in Berlin...are you sure that your file paths and names do NOT contain any special characters like Ä,Ö,Ü? Ansys is unable to deal with that symbols if exsitant in ANY part of the full path.... Oh and if you are using ICEM as a mesher...exporting the mesh as binary file instead of ascii would reduce the file size significantly and speed up the loading in pre a bit... Have you checked your RAM usage during the Load process?

February 11, 2016, 08:46		#8
marcel_jay Member Marcel Jay Join Date: Jun 2014 Location: Berlin Posts: 52 Rep Power: 12	I isolated the problematic geometry, which is a cooling fan with about 80 blades at a 80mm outer diameter. So there was only 1 interface left. I even extraced the silhouette geometry and remodeled the part in NX10 and afterwards created an enclosure in DesignModeler. The problem still persists. I sent the geometry to our supporting partner CADFEM but so far they have not come to an conclusion what causes the issue. There seems to be some kind of geometry that is totally fine in meshing and designmodeler but not in CFX-Pre. Maybe it's some kind of bug. Cheers

April 10, 2017, 05:55		#10
hereford_jon New Member Jon Powell Join Date: Oct 2009 Location: Herefordshire Posts: 16 Rep Power: 17	I have the same issue with a CHT model in CFX 18.0 I have tried it on several machines to rule out machine issues. I suspect that it is a part with many faces (a chassis casting) which is causing the problem. Will try this workaround. Again the geometry is fine in Spaceclaim and Meshing, just CFX-Pre slowing things down massively.

April 11, 2017, 02:03		#11
urosgrivc Senior Member urosgrivc Join Date: Dec 2015 Location: Slovenija Posts: 365 Rep Power: 12	I think that the biggest problem in cfxpre loading time is caused by automatic interface detection in cfxpre. I have geometries composed up to 8kfaces and ~13Mnodes by disabeling auto detection the time was reduced by 98% (from 2h to 3min) for a CHT simulation of a brake disc. And the more the faces the longer the loading time. So I newer ewer use auto detection in my simulations + disabeled phisics valiadation and all that automatic detection stuf. I had huge problems in the past the cfx pre would go into auto phisics valiadation mode while i was seting up the problem, and than I would wait 2h until it came back so i had to force close the cfx a lot of times during the cfxpre problem set up (furtunatley somehow no data is lost when forceclosing cfx pre so thumbs up for that). I dont hawe eny problems now with all that disabled. -Disable strict tipe domain checking -Disable auto phisics valiadation -Dont show interface boundaries Dont let cfx do work automaticly for you it is slow and you dont need it.

December 22, 2018, 19:40		#12
Duke711 Member Join Date: Dec 2016 Posts: 44 Rep Power: 10	Big Model: 7500 Faces 45 M Cell ................ without a graphic card: 2 hours with 1080 TI 3 mins. CFX display all faces, you need a good graphic card