Open source cfd program

[Christopher Crowe]

Has anyone used one of the open source CFD programs?

If so, can you share what you learned? Was it beneficial? Etc...

Thank you,

Christopher Crowe

[Rick Ross]

http://www.dailyfinance.com/story/cr...wide/19728402/

Do a search here for "OpenFOAM" and you will find some general info. You may also want to contact Nathan at Radon Sport -- they have used OpenFOAM for their FC designs. OpenFOAM is a powerful application in the hands of an experienced user.

However, in my opinion, attempting an analysis with OpenFOAM or similar would most likely be a complete waste of your time, unless you want to hire professional help. I suspect that a few hours in a decent rolling-road tunnel would be much more cost effective.

[lmpdesigner]

Open source is a bit tricky.

You have to get a preprocessor to generate the mesh from the .stl or CAD file.
You then need a solver (Like open foam)
Then you need a post processor to generate any decent data.

And you need all three to talk to each other.

And if they don't you have no one to go to to ask how to fix the problem.

Actually you have no support at all.

And then do you have a CPU cluster that can actually handle the analysis? Figure a linux cluster of 30-40 CPU's (not computers) to get you into acceptable runtimes.

And then do you have any experience or clue as to how to set up the environment/system constraints?

How do you model a rotating tire?
What do you do about tire/earth contact?
What do you do about Control volume size?
What do you do about correlation? (Big one!)

A lot of people create fancy looking pictures of cars and diffusers and wings with pressure distributions and streamlines and it all looks good but 90% of all this stuff has been done wrong.

And I do know. It is part of what I do for a living.

[Wright D]

[FONT=Verdana]I too have a lot of experience setting up and correlating CFD studies to real life. It is both expensive and time consuming to get good correlated data. Setting up rolling roads and tires/wheels(and the flow through the wheel) may be difficult in open source CFD programs. Not to mention things like flow through the heat exchangers or hot exhaust. . Open source CFD for the club level might be best used to determine big trends, as opposed to refining small details. Even if your model is only 90% accurate, it is still better than just plain old guesswork or throwing darts at a board.[/FONT]

[Ty_Handke_83]

It is better than nothing, but it can also be worse.
I've tried 4 different open source programs, and all 4 of them produce different results running what I thought were the same tests. When I did find my errors in 2 of them, the results were closer, but still not what I would call comparable to be able to use one over the other as hard data.
As was said above, it's not as easy as it may seem to correctly program all the factors needed for usable data.

[Christopher Crowe]

This is really the tough part (on this racing level). Thanks for the heads ups, the hard-won information from each of you!

Christopher Crowe

[rperry]

I use openFOAM. It's great code, and the mesher (snappyhexmesh) is good as well. BUT, it is VERY difficult to use. It can do rotating wheels, moving ground planes, radiators and cooling flows, etc. If anything it's more capable than most commercial codes. But unless you're an experienced CFD person don't even bother. It's very tedious until you write custom scripts to setup cases, etc. And it takes a long time to establish the correct meshing and solving practices. The mesher is big on memory, too.

It is as good for detailed design as any other code, and some F1 teams use it, as do quite a few automotive OEM's. It is certainly miles ahead of things like floworks, but then you don't need a PhD in CFD to get floworks running! It's getting better though, and there are some commercial meshers that actually interface with FOAM nicely.

Unfortunately, at the small Formula car level it's really the only affordable way of doing CFD. I used it for race car development and have found it great! But at the same time CFD is my career focus and I've been doing it for a while.

[Rick Ross]

Hi Robert,

Thank you for taking the time to comment on this interesting subject. You have reinforced my opinion that useful and valid CFD results are almost impossible to obtain for 99% of us club racers. In my opinion, most club racers would be better off spending their time and money on a few hours in a decent wind tunnel.

BTW, I enjoyed your 2008 AIAA paper regarding F1 aerodynamics. This paper would be good reading for anyone who is considering an attempt with something like OpenFOAM.

Rick

[Janko]

Is the 2008 AIAA paper regarding F1 aerodynamics paper available for download anywhere? or what is the exact title so that I can find it.
Best regards,
Jan

Hi Robert,

Thank you for taking the time to comment on this interesting subject. You have reinforced my opinion that useful and valid CFD results are almost impossible to obtain for 99% of us club racers. In my opinion, most club racers would be better off spending their time and money on a few hours in a decent wind tunnel.

BTW, I enjoyed your 2008 AIAA paper regarding F1 aerodynamics. This paper would be good reading for anyone who is considering an attempt with something like OpenFOAM.

Rick

[rperry]

Hi Robert,

Thank you for taking the time to comment on this interesting subject. You have reinforced my opinion that useful and valid CFD results are almost impossible to obtain for 99% of us club racers. In my opinion, most club racers would be better off spending their time and money on a few hours in a decent wind tunnel.

BTW, I enjoyed your 2008 AIAA paper regarding F1 aerodynamics. This paper would be good reading for anyone who is considering an attempt with something like OpenFOAM.

Rick

I agree that no club racer could find openFOAM useful, but as costs go down it will be more and more affordable to hire specialists to do it.

And thanks for the feedback on the paper! I didn't know anyone but me ever read it

Is the 2008 AIAA paper regarding F1 aerodynamics paper available for download anywhere? or what is the exact title so that I can find it.
Best regards,
Jan

Here it is:
http://pdf.aiaa.org/preview/CDReadyM...V2008_6733.pdf

I think AIAA charges a ridiculous amount for their papers though, so if you PM me your email I can find my original copy at home and email it to you :-)

[Rick Ross]

Hello Robert,

I did indeed read your paper, although I must admit that much of it was over my head. Nevertheless, I think that it provides an excellent perspective on what is required to do any type of comprehensive CFD analysis of an open-wheel race car.

I was able to obtain a copy of the paper for free from my university library in conjunction with a graduate aerodynamics course that I was taking at the time. Purchasing the paper directly from AIAA would probably be quite expensive. Perhaps a Google search for AIAA 2008-6733 would reveal a free copy somewhere on the net?

Rick