CFD progress ?

[Nerds laugh at me]

Hello everyone!
My computer died, so I took a much needed break from computers and spent a lot of my extra time outside.
( You should try it sometime ! )

The last time that I was here on this site though, I had a discussion involving CFD aerodynamics software.

What I'd like to find out is what progress has been made with the fellow here on this site that was using CFD software ( sorry - I don't recall your name :) )

I tried the search feature using the words " CFD and Fluent " but it came up with nothing .

Thanks !

[ChrstphrR]

Nerds laugh at me, I think the thread you were after, was this one by trebuchet03.

http://www.gassavers.org/showthread.php?t=5714

Hello everyone!
What I'd like to find out is what progress has been made with the fellow here on this site that was using CFD software ( sorry - I don't recall your name :) )


You'd mentioned in that thread that you had a model of a '93 Civic that you were hoping to adapt for CFD purposes. And you mentioned the crash, too :(

I had to hunt, myself, because I'm interested in getting more accurate models made of a Mk IV Jetta, which is the same body model that trebuchet03 has.

[Nerds laugh at me]

Yep ..that's the one !
Thanks for the help.

BTW, I still plan to do a model of a MkIV Jetta as well.
The profile is very similar to that of the Ford Fusion Bonneville car which attained a .21 Cd.
I plan to possibly purchase one myself and run it on Veggie fuel ( and get over 40 MPG to boot )

[ChrstphrR]

I'd been hunting the past few months since that other thread for decent baseline models of the 4th-gen Jetta, and I did find a few.

The better ones ring in at around 38k polygons, part of this is modelling the interior.

Seems to have details like some panel seams.

The downside, however, is...


Improper vents for the intercooler and radiator up front.
Flat underbody that doesn't model the real non-flat underbody
No engine / drivetrain / engine bay
Simplified wheel wells. Front wheels can't turn.


Getting/making a good, accurate model will take a lot of extra legwork, I think.

I'm about a decade away from the last time I used any CAD program, but hey, it's a lot like riding a bike!

My intent with this, was to help improve the missing details with the model, when I've time to take better measurements off my car. My focus right now is directly on the stock hubcaps

My eventual todo list:

Base model hubcaps (working on the "VW" logo bezel in the center, and working outward)
Base model Steelie rims under the hubcaps
Mudflaps
Wheel wells
Brakes/suspension bits in the wheelwells
Lower valance under the bumper
Rough out the engine bay and then, the drivetrain in it.


The stock plastic "skidplate" on the Jetta isn't in the works -- mine's not on, so I can't take measurements. :(

The best of the drawings I've found, was stored up as a series of meshes on different layers, in Autocad .DWG format, if anyone IS interested, I'll check my original source, to see if I can post the file, or if I'm restricted to digging up the original site/link.

[Nerds laugh at me]

Could you e-mail me the mesh ? I would save me a lot of time.
I just started adding some details to the Civic model. So far it is just a body shell and some wheels.
I planned to add a full undercarrige and engine .... so I've got a lot of work to do still.

[ChrstphrR]

http://www.accustudio.com/exchange/fm_objects.php?dir=vehicles

Relocated where it was, so that the lurkers can poke around too...

It's near the bottom of this page, listed as "vw-bora.zip" (Jettas are Boras in Europe).

[Nerds laugh at me]

ChrstphrR : I managed to follow your link and find the file that you were talking about.
Unfortunately, my main 3D program is having problems with a .DWG file.
I have a demo of Cinema 4D R10 that opens the model, but I it is save disabled.
I had hoped that my older version of C4D R 6.5 would open the file, but V6 won't open .DWG files.
I also tried Wings, Blender ( still working on that one ) Silo, XSI, ....
Can you convert the file to .3ds or .obj ?
i just downloaded a converter. I'm not sure if it will work or not.
I'll let you know.

From what I saw of the model in the C4D demo, it is very accurate and well built.
I would be happy to finish it given the time.

BTW, my Civic model is nowhere near as good as these models. I still have loads to do on it.
( Part of which is learning how to use the tools .)

[Nerds laugh at me]

I just tried an app. called QCad to convert the file.
Not -gonna -work.

[Nerds laugh at me]

So what of the CFD program ?
Where can I buy one that won't cost me a fortune ?
Anyone have any ideas ?
I'd like to take advantage of a student discount to save some cash

I'd really like to find one that is no harder to learn than the 3D software that I currently use.

( Thanks ! )

[ChrstphrR]

Converted the files, left you a private message on the forum here with the link to grab them.

Both .3ds and .obj format conversions.

Both lost the pretty colouring that they had for each layer, so everything's black for ease of confusion. :P

It's an accurate model that's been floating around in several formats, so, if you still have issues importing the converted files I made, I'll scour the 'net for the original 3DS file.

Let me know how it goes.

[ChrstphrR]

The CFD program that trebuchet03 was using, was a plugin that worked with SolidWorks - SolidWorks being the mechanical CAD program, and Cosmos FloWorks being the CFD plugin that models fluids thermodynamically.

I haven't gotten to the CFD phase, myself, mostly because I'm intent on modelling the underbody of the model I do have more accurately.

Erm, and since I have wear and outright missing parts on my own Mk IV Jetta, I will have an up close and personal look at some of the parts that weren't given as much detail, like the black lower valance under the bumper, and some of the inner fender panels.

Rest assured, I'll be taking plenty of pictures for that! :)

...

Back to SolidWorks, I finished digging around on their site:
http://www.solidworks.com/pages/products/edu/studenteditionsoftware.html?pid=107

Student version, for those whom are students, is around $99 USD, SolidWorks with all the Cosmos plugins (inlcuding FloWorks), is $199 USD.

Now, that said ... I've never used the programs, trebuchet03 can vouch for them better. And, quite likely, he might have other suggestions for programs as well.

[Nerds laugh at me]

Wow.
One copy of Solid Works ... sold !

( Once I get back into classes that is ! )

Have you had any luck with converting the file to either .obj or .3ds ?

I could volunteer to model some of the car and we could compare notes.

My neighbor has a Jetta that I could use as reference, but I'm not sure how he ( or she ? ) would think of some stranger taking pictures of their car. :)

[ChrstphrR]

Check your messages on the forum -- I left a link for the converted files. :)

The missing bits of the model are under the hood, or underneath, so I think you'd REALLY want to ask the neighbour ahead ;)

I just layed out part of my drawings for the stock plastic hubcaps. Surprisingly, VW's design uses fairly simple numbers (if you use metric measures, that is).

[Nerds laugh at me]

I just read the fine print - Solid Works Student edition is only functional for 24 months aand then you can't buy it again unless you pay the $ 4,995 fee.
I would think it could take me 24 months just to learn how to get around the interface.

What a letdown.

[Nerds laugh at me]

I would think that perhaps a smarter thing for me to do would be to model things that I wanted to run CFD testing on and then see if trebuchet 03 would run it through a CFD test session for a fee.
Trebuchet03 : What do think of that idea ?

[Nerds laugh at me]

ChrstphR : I added the VW emblem to the front of the grille.
I have plenty of reference of the outside of a Jetta, but I need some good pictures of the engine compartment and the underside of the car.
( Also the underside structure of the hood and in the wheel-well area. )
You said you planned on taking plenty of pictures. So any help would be appreciated.

EDIT : I just viewed the picture that you posted of your car. NICE hubcaps !
Can you post a good picture of them so I can add them to the model ?
As smooth as they appear to be, they should function just as well as 'moon' wheels.

[Nerds laugh at me]

What modifications are you plannig to test on your Jett' ?

Are you going to keep the stock open spoke wheels ? Block the grille ? Add spoilers ? Lower the car ? Add vortex generators ? Add a belly pan ?

[ChrstphrR]

ChrstphR : I added the VW emblem to the front of the grille.

*snip*

EDIT : I just viewed the picture that you posted of your car. NICE hubcaps !
Can you post a good picture of them so I can add them to the model ?
As smooth as they appear to be, they should function just as well as 'moon' wheels.

Whoo, the front emblem is something I didn't yet have in place -- I've gotten the hubcap logo sized up, after many attempts.

And the hubcaps, I don't have a photo per se, but I took measurements ... I'm in the process of trying to model those right now, what I need to do is take depth measurements to get all the details right -- they're not flat hubcaps, like the ones on my mom's ol' 1980 Impala.

My back is killing me from a no-obvious-cause pull around my shoulder blade today, but I'll try to get a few of those remaining depth measurements found out in the next few days. I'll forward a drawing, even if it's only 2-D, of the stock Jetta hubcaps when I get that much done. If I get the whole thing done up, then I'll send that, as well.

The hubcaps on my Jetta "Greta", are the stock model's steelie covers. The model I dug up and sent your way it has the GLI (or GLS?) model alloy wheels, which are nice, but probably not as nice from an aerodynamic standpoint.


And since you mentioned it, here's what I'm hoping to accomplish with my car after getting semi-accurate model with an engine/underbody:

Nearer term ideas:


Rear wheel spats.
Fair in / block most of the extraneous radiator intake vents.
Re-mount either a stock, or an aftermarket skid plate. I'm running without, and I know it's a noisier car without that extra bit of sound deadening. It's probably costing me quite a few points on my Cd as well.
Full undertray, built up in stages, out of coroplast. There's room to improve from the front valance to the stock/aftermarket skidplate, and before the front wheels. I'd have to avoid any hotspots like the exhaust, too, but most of the ares under the passenger compartment, and the trunk can be improved upon, too.
Wiper fairing just after the end of the hood, before the windshield. trebuchet03 and I bantered about this idea in another thread.


Longer term ideas, when I have access to my Dad's garage a few provinces away... These ideas are listed from most practical, to more fanciful. I doubt I'll achieve them all, but hey, why not throw the ideas out? :)


Full undertray. (Metal supports and maybe Al-plastic-Al sandwich material like that used on signage, excepting the area already well covered by the stock or aftermarket skid plate)
Proper air-intake to Radiator fairing, that funnels outward from the intake to the radiator in a venturi tunnel/diffuser shape.
Reshape the front wheel wells for closer tolerances, and/or make fibreglass outer fenders to shape the trailing edge of the wheel wells to allow for better airflow.
Model various fairings for the mirrors, to see if any give reasonable benefits.
Fastback modification. If modelling fails to make this work well, I'd consider keeping my eye out for a Jetta TDI wagon, and consider modifying the roofline so it gradually slopes downward after the front seats, at an 11° angle.
Or, basjoos-inspired fastback/teardrop fairing to improve the drag from the roof and the back end of the car. (pending local laws permitting such things)


Of course, after being able to model a car "stock" and with some of those modfications, I can decide which of the low-hanging fruit give the best improvements in airflow and drag.

Overall, I'd like to make changes that make the car maintain it's stock look, and/or modifications have to be reversable, to return to stock.

Sometimes trunks are useful things when fulled full of groceries, and closer fitting wheel-wells may not work well in winter due to ice and snow buildup. All in all, I still need a reasonably practical car; and other people will be more likely to make changes to their own vehicle that don't change the outward appearance of the car appreciably. If a full undertray's worth 5mpg or more, and no one sees it, it's a more compelling reason to make the change.


One of the benefits to modelling for CFD purposes, will be a bit of testing on the cheap, to refine better ideas before endlessly making physical prototypes.
The auto industry does this already, to reduce R&D costs. I like the idea of building a wiper fairing ... but I don't like the idea of making 12 variations of a fairing, and then doing A-B-A testing on each to verify that one's marginally better than the others.

Another benefit will be -- dimensioned drawings can easily be made from the modelled modification parts, which'll allow for more OEM looking parts to be made for myself, and allow other tinkerers to make their own fairings and parts that will fit their same cars too.

This allows more rigorous testing -- more people to reproduce the results, real-world. I know I would've made some underbody fairings to make a belly pan by now, if someone ELSE made up plans and drawings and a nice how-to already. But that really hasn't happenned, for my Jetta yet.

Thus, instead of waiting for someone else to hand that to me on a silver Jetta... erm, platter, I meant... it looks like I have to do that legwork myself, well with a bit of help from folks like you, Nerds laugh at me.

[Nerds laugh at me]

I just noticed the hub caps on my neighbors Jetta. They are the same as yours - so don't worry about posting an image of them.
I'll just go out and take some pictures of them when she is not looking.

The main thing that I need images of are around the inside of the grille area.
I'll research it some online and see what I can dig up.
Also, I need images of the underside and wheelwell areas.

[JESSE69]

I just read the fine print - Solid Works Student edition is only functional for 24 months aand then you can't buy it again unless you pay the $ 4,995 fee.
I would think it could take me 24 months just to learn how to get around the interface.

What a letdown.

If you can find it, Solidworks 2006 with CFD and FEA bootleg is out there!

I couldn't get the Student Edition because I didn't register in enough classes. And then my old Student Edition models were read and converted by Solidworks Industrial version!

[Nerds laugh at me]

Chrstphr : What's the latest with your modelling efforts ?