Who here uses OpenFOAM ?

[KamperBob]

Originally Posted by Cd

Thanks a billion KamperBob !

NP

I'd love to hear a report if you try it.

I just got Puppy Linux running on my laptop. I haven't got OpenFOAM to work yet. So many learning curves. I did get MATLAB running under Linux but had to use software OpenGL. That does not bode well...

Cheers
KB

[Ardent]

This linux live CD looks like an easy way to get started without the need for installation: caelinux.com/CMS/index.php?option=com_frontpage&Itemid=1

I haven't tried it myself, but was looking into it.

[ConnClark]

Well I got the bug and started playing with open foam again. I learned a nice lesson about hard disk space, time, and 3d simulations. You need a lot of space and patience. I ran the pitz daily 3d test case and it used up all 50GB of space I had free on my laptop. It also took 5 minutes to simulate 0.0005 seconds and would have required 100 hours to finish the full half second simulation if I had the disk space to spare.

I have some recommendations for people trying to use it for car simulations. Use linux ( a fast distribution like Gentoo is a good choice ). Have at least 4GB of ram, more is better. Have more than 200GB of free disk space. Compile the package yourself and optimize it for your machine. Compile your kernel yourself and optimize it for your machine.


Some other performance notes. Use a linux kernel that has the transparent hugepage patch applied. A processor with four cores is not that much faster than one with just two cores because they fight over memory bandwidth (Larger level 2 caches help a little). If your going to do a cluster you want a fast network with low latency (gigabit or faster).

[ConnClark]

An interesting paper on using openfoam for vehicle design

http://web.student.chalmers.se/group...nPaperOFW5.pdf

note that they have access to a super computing cluster

[ChrstphrR]

Originally Posted by ConnClark

An interesting paper on using openfoam for vehicle design

http://web.student.chalmers.se/group...nPaperOFW5.pdf

note that they have access to a super computing cluster

Also noted for that paper, they set their CFD job to run on only 64 or 128 cores of the 8000 the cluster had available. That does make it far more powerful than what most of us have at home, but it's not thousands of times more.

Did your laptop have the same amount of RAM you were recommending, ConnClark? My "spare" machine that's already running Ubuntu's distro of linux has plenty of disk space, but it only has 1Gb of RAM memory, and likely that will be the limiting factor. That, and it's wouldn't be dedicated solely for running OpenFOAM.

[ConnClark]

Yes my laptop has 4 GB of ram. I once tried to simulate a ramjet without combustion on a dual core desktop with 2GB. It really needed about 8GB of ram for the simulation and started swapping like crazy. At that point every 4k of ram I could free up helped. I even resorted to using some of my video card memory for a fast swap file. It helped some when I off loaded some of the processing load to a single core machine with just 1GB but still it was too slow and I gave up.

You really don't want to swap at all when you simulate so the more ram you have free the better. There is another new kernel feature that uses some of your ram as a compressed swap file that may help as it is less costly to compress and decompress from ram than to swap out to disk but it is still experimental with some quirks.

compcache - Project Hosting on Google Code

I'm still no expert at this but often you can't have enough hardware to throw at serious problems. Another part where you'll need a lot of ram is when it comes time to visualize the data.

[ConnClark]

I found that there is a basic windtunnel like tutorial case for Openfoam in the tutorials/incompressible/simpleFoam/motorBike directory.

It consumes about 1/2 a Gig of ram when running.

[Cd]

Really glad to see you guys are still trying to figure this out.

[KamperBob]

Originally Posted by cd

really glad to see you guys are still trying to figure this out.

+10

[khafra]

How are the OpenFOAM efforts going? I was hoping I could use a simpler program like Khamsin, a Sketchup plugin--but the CFD solver it uses only seems to work with static meshes. I want to see the effect of the dynamic aerodynamic devices in this Chrysler patent: Motor vehicle with flow-influencing ... - Google Patents And only OpenFOAM seems to support dynamic meshes.

I can't figure out any way to simply prototype and test that physically, even with a lifetime supply of Coroplast :/