## CFD - Computational Fluid Dynamics, Motorsport, Formula 1

Here are our CFD links and discussions about aerodynamics, suspension, driver safety and tyres. Please stick to F1 on this forum.
shelly
144
Joined: Tue May 05, 2009 11:18 am

### Re: CFD - Computational Fluid Dynamics, Motorsport, Formula

OpenFoam is powerful, and I think some professionals are beginning to look at it for their simulation. I don't know how difficult it is to use it out of the box.

AcoidanBM
0
Joined: Fri Mar 18, 2011 12:59 am

### Re: CFD - Computational Fluid Dynamics, Motorsport, Formula

PNSD wrote:Hello.

I was wondering if somebody could offer me some help with Fluent.

Ive done a 3d sim, I simply want to display the pathlines as shown here:
http://www.f1technical.net/articles/71

I know that I have to define where to release from but thats where I get stuck.

Say for example my flow domain is:

x = 10
y = 2
z= 4

And then say my object of interest is at:

x = 4 to 6
y = 0.75 to 1.25
z = 1 to 3

How would I go about setting my pathlines using such dimensions as an example. Is this clear?

Thankyou
Hi.
I think I dont understand your question.
You just have to create a line behind your shape: Surface - Line/Rake and put the coordinates. For example:
x0: 3 .........x1: 0
y0: 0.75 ......y1: 1.25
z0: 0.5 ...... z1: 0.5

Then Display-Pathlines and select that line as a source in the pathline (release from surfaces).
I recomend you to increase the steps (by default 500) depending on your domain and to color by Velocity Magnitude.

Then, using Scene Description (Display-Scene) you can combine pathlines plot with contours plot.

PNSD
4
Joined: Mon Apr 03, 2006 5:10 pm

### Re: CFD - Computational Fluid Dynamics, Motorsport, Formula

This was a long time ago, I learned since but thanks for the reply :p

edit - you are right, it was a rake or surface iso i used, i dont remember now...

connollyg
0
Joined: Sat Jul 22, 2006 8:25 am

### Re: CFD - Computational Fluid Dynamics, Motorsport, Formula

Some of the F1 teams use OpenFoam, at least they used to. Brawn being one of them.

The thing about the F1 teams is that they are probably using 1000 core machines to do their CFD on as their models can go as high as 100 million cells

Tozza Mazza
1
Joined: Thu Jan 13, 2011 11:00 am
Location: UK

### Re: CFD - Computational Fluid Dynamics, Motorsport, Formula

Hi, I'm a first year at college in the UK, and have been looking at a course at Southampton University, Aeronautics & Astronautics, with a view to specialising in aerodynamics in my 3rd and 4th year. It has a strong motorsport history, with Newey having graduated there. I've been following F1 since i was a wee lad, been to races, and the cars never cease to amaze me. I'm intelligent enough and have actually been created a model of an F1 car. I would love to learn about and run CFD, however i have windows XP and it seems all the software i could find was for linux, which is freeware. any tips/software advice. i would love to see my front wing i modelled go through CFD, it's very close to the W02's front wing.
TM

connollyg
0
Joined: Sat Jul 22, 2006 8:25 am

### Re: CFD - Computational Fluid Dynamics, Motorsport, Formula

I think you need to learn Linux quick. i don't believe any of the F1 teams use windows for their CFD work

Just_a_fan
259
Joined: Sun Jan 31, 2010 7:37 pm

### Re: CFD - Computational Fluid Dynamics, Motorsport, Formula

http://www.caelinux.com/CMS/ was mentioned earlier in the thread. Try that. You can download the iso, whack it on a disc and boot to it from the dvd. No need to take XP off your machine or dual boot linux from the HD.

What spec pc do you have? Lots of RAM is good. Multicore is good too. But lots of RAM is good...cfd is memory intensive.

Remember also that cfd resource requirements scale really quickly. Double the cells in each axis and you have 8 times the number of cells. I used cfd for my MSc (in a fire-related subject, not aeronautics) and found how quickly you can go from a simple model running in a few hours to one that takes several weeks just by simply increasing the cell count. This was with a structured mesh model rather than the unstructured meshes usually used in aeronautical work.
Turbo says "Dumpster sounds so much more classy. It's the diamond of the cesspools."

0
Joined: Tue May 04, 2010 9:10 am

### Re: CFD - Computational Fluid Dynamics, Motorsport, Formula

connollyg wrote:Some of the F1 teams use OpenFoam, at least they used to. Brawn being one of them.

The thing about the F1 teams is that they are probably using 1000 core machines to do their CFD on as their models can go as high as 100 million cells

not related to F1 but i am now running a job with 3.6 billion cells and with 670 odd processors.

That is for drag computations of golf ball.

Formula None
1
Joined: Wed Nov 17, 2010 4:23 am

### Re: CFD - Computational Fluid Dynamics, Motorsport, Formula

That's a lot fore a golf ball. Does it have an f-duct?

0
Joined: Tue May 04, 2010 9:10 am

### Re: CFD - Computational Fluid Dynamics, Motorsport, Formula

Formula None wrote:That's a lot fore a golf ball. Does it have an f-duct?

Yaa, but that is Direct Numerical Simulation for high Reynolds number.

no ducts etc, trying to calculate drag lift with various spins.

Ps: I mentioned that because 100mil somehow now looks very small to me. There was a time when i used to think 5 million were too many. Now 100-200 million cells and i think it is a baby calculation.

raymondu999
138
Joined: Thu Feb 04, 2010 6:31 am

### Re: CFD - Computational Fluid Dynamics, Motorsport, Formula

Forgive my ignorance, but I used to do something similar-ish for submarine propulsion; wouldn't these calculations, though you have millions/billions of them, wouldn't each individual calculation be actually rather simple? I don't remember the kind of computational power I was using, but I think for a golf ball (never did something that small before, so I could be wrong) that 670 procs would be overkill, no?

gridwalker
6
Joined: Fri Mar 27, 2009 11:22 am
Location: Sheffield, UK

### Re: CFD - Computational Fluid Dynamics, Motorsport, Formula

Just_a_fan wrote:http://www.caelinux.com/CMS/ was mentioned earlier in the thread. Try that. You can download the iso, whack it on a disc and boot to it from the dvd. No need to take XP off your machine or dual boot linux from the HD.
... that is IF you don't mind running the whole OS off of a virtual RAM disk and making your entire computer run like a slug in a coma. Booting from a live CD is great for a quick demonstration, but terrible under a heavy-use scenario.

I'd hate to see what running a CFD job whould be like when running off of a live CD : I can imagine it being worse than useless due to the speed penalties of running in that mode.
"Change is inevitable, except from a vending machine ..."

shelly
144
Joined: Tue May 05, 2009 11:18 am

### Re: CFD - Computational Fluid Dynamics, Motorsport, Formula

raymondu999 wrote:Forgive my ignorance, but I used to do something similar-ish for submarine propulsion; wouldn't these calculations, though you have millions/billions of them, wouldn't each individual calculation be actually rather simple? I don't remember the kind of computational power I was using, but I think for a golf ball (never did something that small before, so I could be wrong) that 670 procs would be overkill, no?
If you are doing DNS at high Re computational power is never enough because you are not modelling turbulence, but directly calculating it (Direct Numerical Simulation). So you need much finer spatial grids and shorter time intervals.
It is the top level of simulation hierarchy (which tells: RANS, URANS, DES, LES, DNS), the most demanding in terms of computational effort.

F1 teams instead often use thousands of processors for performing RANS / URANS job quickly with meshes around 100-300M cells.
Maybe some of them have already approached DES and LES

Just_a_fan
259
Joined: Sun Jan 31, 2010 7:37 pm

### Re: CFD - Computational Fluid Dynamics, Motorsport, Formula

I once did a DNS run of an idealised candle flame (the domain was 50mmx50mmx200mm with cells <1mm in dimension but less than 1M cells in total).

That took about a week to generate about 10 seconds of simulation using all 4 cores on a quad core with 8GB of RAM. That did include thermal radiation as well as modelling of the thermally driven airflow though.
Turbo says "Dumpster sounds so much more classy. It's the diamond of the cesspools."

0
Joined: Tue May 04, 2010 9:10 am

### Re: CFD - Computational Fluid Dynamics, Motorsport, Formula

shelly wrote:
raymondu999 wrote:Forgive my ignorance, but I used to do something similar-ish for submarine propulsion; wouldn't these calculations, though you have millions/billions of them, wouldn't each individual calculation be actually rather simple? I don't remember the kind of computational power I was using, but I think for a golf ball (never did something that small before, so I could be wrong) that 670 procs would be overkill, no?
If you are doing DNS at high Re computational power is never enough because you are not modelling turbulence, but directly calculating it (Direct Numerical Simulation). So you need much finer spatial grids and shorter time intervals.
It is the top level of simulation hierarchy (which tells: RANS, URANS, DES, LES, DNS), the most demanding in terms of computational effort.

F1 teams instead often use thousands of processors for performing RANS / URANS job quickly with meshes around 100-300M cells.
Maybe some of them have already approached DES and LES

Exactly. Thanks for writing as now I do not have to write all this.