Rolling Wind Tunnel CFD
 

I'm happy :D

I just figured out how to model a rolling wind tunnel for CFD analysis.... This makes me happy because ground effect plays a big role in drag :thumbup:

http://forum.ecomodder.com/attachmen...1&d=1207021467


To make sure it was working, I made the rolling ground move in the opposite direction at 250m/s - it created some massive crazy swirls :D

That was a super duper low resolution run - tonight I'll run a high resolution version to do some calculations with :D

OpenFOAM?

OfficeLinebacker , welcome to the site.



trebuchet03,
It is an airfoil big enough to enclose a rabbitt.

the excel plot is for a pickup truck
diesel

What type of info are you looking for? That is, post a sketch on how you want it setup (do you want a ground, how far off?, velocity, size, etc.) and list what outputs you want.... I might not be able to do it immediatly, but if I can find the equation that governs that foil shape, I can model this in a few minutes and run CFD ;)

Quick search from google got a cool flow visualization...
http://legacy.ensight.com/news/airfo...animation.html

What's nice about NACA foils is that there's a lot of data on them already :)


And Linebacker, not FOAM - COSMOS FloWorks ;)

trebuchet03 : I was working on a 3D model of your Jetta. ( We discussed it on the Gassavers forum )
I just had to replace my hard drive, so my liscenses got messed up on the 3D program.
I, as well as a couple of others here and on the Gassavers forum would really love to see some tests done with the Jetta.
Do you think you will ever find time to run any tests ?

It would be nice to see what kind of figures could be produced by lowering the car and adding a trunk extention, since the Jettas' profile is almost identical to the Ford Fusion Bonneville car ( which if you recall scored a .21 .Cd ! )

.cD

trying to parametrically model a car - from scratch - is incredibly hard (beyond the amount of time I'm willing to invest at the moment). Simplification won't yield much, if any, useful data considering the chaotic nature of this sort of system (small input changes yield great output changes).

But, I'm trying to come up with a way to reverse engineer large objects cheaply... I need to do more research, but right now the only solution I've got is building a large rotating platform and casting a laser line over the car and video recording it... Not practical at the moment as that platform would have to be motorized to move at a constant angular velocity (and cars are heavy :p).

If I can find or come up with a way to reverse engineer large bodies on the cheap - this wouldn't be limited to a Jetta :p

For reference... here's an expensive method
http://www.sammertech.com/measuremen...ry_session.jpg
Photogrammetry
you get....
http://www.sammertech.com/measuremen...ygon_model.jpg

in a .stl file -- techniques like this is how a full scale clay model is digitized for further analysis :D


EDIT:

As far as time is concerned.... Time to run tests is no problem... It's mostly a set it and forget it sort of thing. Well, maybe an hour or so of setup... It's just getting the model :p Doing things like that NACA are no problem if I can get that foil shape parametrically... Something like a car, freaking hard :D I'll have much more time this summer though :D

I might have to send a model your way for testing... :)

.cD - look what I just found... Not a Jetta, but it's European cousin :D

http://www.3dcadbrowser.com/preview.aspx?ModelCode=8547

http://all3models.brinkster.net/th/1/8/8547.png

http://all3models.brinkster.net/th/2/8/8547.png

Too bad it's not a free download (but they have a stereo lithography format I can work with :D).... You get 1 download for every upload, I'm going to see what they're looking for in an upload :D

trebuchet03 -

that flow visualization is awesome.

i got the foil data from this site.

http://www.pagendarm.de/trapp/progra...les/NACA4.html

looking for the Cd for the shape in post #3 with the top and bottom splitters.

approx. 4 inches off the ground

trebuchet03 -

You should do the following :

1 - Get 4 ecomodders to chip in $20 for the 5 download registration ($79)
2 - Download your car "for free" and one car for each ecomodder that pitched in.
3 - Model their cars using your software, any way they want ... UNTIL THE END OF TIME!!!!!!!!!!!!!!!!

Hmmmm, maybe it's not worth it for you.

EDIT: Here's the one I want (modded into a wagon, of course) :D :
http://64.78.14.108/ts/1/2/2224.png

CarloSW2

It's tempting.... But it's my time -I don't want to ostracize myself because my unreliable schedule at the moment. That, and if it turns out these models are crap.... That would suck, a lot.

Maybe in the not so distant future though :p

Hey guys, Actually I'm working on that very model.
It is a very detailed model, but is missing the supension and engine pieces.
So far, the only things that I have done to the model is add the VW logo to the front of the car. ( The outside of the car is pretty much finished as is. It even has the wipers modelled. )
I would have started working on some other pieces of the car, but I do not have reference to go from. ( So it would be a waste of time since I have no idea what I'm supposed to be modelling. )
What I am needing is an image of the suspension of the car, as well as what the inside of the engine bay looks like. Anyone have a picture of the underside of a TDI Jetta ?

Also, I believe we spoke over at the other ( gassavers) forum concerning your Saturn model CarloSW2.
I will need to get my liscense back for my 3D program since I'm having some issues there, but when I do I'd like to do some mods. with your Saturn model.

Hey, .cD

What format do you have that model in?

What format do you need ?

I believe the original format was .DXF .

" ChrstphrR " over at the gassavers forums kindly converted the file to .3ds

I currently have it as a .obj

I haven't opened the file in months. ( Ever since the hard drive problems )

.Cd -

Coolio, now I remember. If you did that, then other Saturn S-Series Ecomodders could benefit. I may take you up on that!!!!!!!!!

I wonder if you could model a "generic suspension/belly pan" that would at least give you a starting point for "the messy air" coming from under the car.

CarloSW2

( cfg83 ) So you have the model with you now, or are you just considering purchasing it ?

There is a free, easy to learn 3D program called wings3d . Give it a try you'll get hooked !

www.wings3d.com

Just import the model into the program and have at it !

If you have the model with you, just PM me and I'll try and get to it when i install the new drive.

Anything that solidworks can open :D

If you've got the dxf, it looks like I can open that... I don't think I can open a .obj or .3ds though :( The best format, for me, would be .sldprt (solidworks part)... I'll take anything though - if I can't open it, I can probably find someone who can and have them convert it.... Send me a PM :thumbup:

So... I've got some files :D Thanks

But holy fudge nuggets! It's huge! (that's what she said)

It's going to take some work to make this usable (for me)... My computer doesn't have the memory to deal with this thing :p But, once I've got it sorted out - I'll start some CFD... Moving ground, spinning wheels, everything. That might take awhile - some big deadlines for the HPV are coming up (presentation for the class next Tuesday - competition near the end of the month!).

Oh man... Excited!

http://www.primitiveengineering.com/VW/model/Front.JPG

http://www.primitiveengineering.com/VW/model/Left.JPG

http://www.primitiveengineering.com/VW/model/Top.JPG


I made it 1/12 scale - for some reason that made it much easier for my machine to handle. It lags, a lot - and it looks distorted at distance - but it's good :thumbup:

Now I need to make some underbelly channels and such and then work on developing channels for internal flow. I may just skip the air inlets and use it for relative comparison for modifications :thumbup:

Oh, and when I get to it (that is, cut extrude and make a surface)... I'll get the actual frontal area :D


Thanks .cD :thumbup::thumbup:

Hey
 

Hey buddy... Don't forget about your TDI cousin. :)

BTW If you want to make the trip over to tower 2 my main desktop has solidworks, a 3200+ and 3 gigs of ram

Oh cool !
I'm glad that you could finally open the file.
I'm still puzzled as to why the file is so huge.

Keep us updated. :)

What are the specs of your machine? I also have some powerful hardware. The most powerful are a Core 2 Quad running at 3.6GHz and an e8400 running at around 3.2 GHz. Those systems only have 2 GB of RAM though. I have an AMD 64 X2 running around 3.5 GHz that has 4 GB though. However that's a Linux box that I am using to try to learn OpenFOAM.

Speaking of which, anyone tried OpenFOAM?

Hey, I noticed that there's a gallery of user submitted objects, and in the automotive category, there are struts/springs, rotors, mufflers, etc. Maybe you could work from some of these:

http://www.3dcontentcentral.com/part...tle=Automotive

At least for a start--a generic suspension/underbody

Local
 

It's nothing too amazing. Just a 3200+ w/ the 3 gigs of DDR2.

OpenFOAM ? Too brainny for me. ;)
Personally, I'm lucky to get around a simple 3D program.

SolidWorks looks like you don't have to be a rocket scientist to learn it ( familiar U.I., no C++ )
Too bad the student version is basically an extended trial version ( and the regular version cost more than my old car .)

OpenFOAM doesn't run on Windows either correct ?

Thanks for the link for the suspension pieces.

P.S. While we are talking supercomputers here, my system is a 1.6 Ghz Centrino tablet PC with a blazing 16 MB of video. ( and a 12" screen)

I feel your envy .

( Seriously ..I am serious ! I actually do run professional 3D software with this weak little piece o' crap. )

Time for a new PC !

Right, OpenFOAM is for Linux. I have a file server that runs Linux so I am playing on that. Based on the pictures and comments I've seen, once one gets it working, it's as good as anything else.

Whenever I am looking for software I generally look on the free side first, and Linux is like a parallel world where everything exists but for a price (effort).