[trebuchet03]

Originally Posted by Deezler

Awesome! Thank you for doing this! This thread is rad.

I want to build my deck lid extension soon, and can't decide on whether to stay with the trunk line or bend it up to extend flat behind the car. I would think that staying with the declining angle of the trunk would be best, IF the flow remains attached. Hence some VG's on the roof to trip the flow.
Also much easier to manufacture, thinking just a flat plate of aluminum or maybe plastic (whatever's cheaper, ha.). With the VHB you speak of for attachment (where does one find industrial grade VHB tape?).

I'll add the VG with deck lid to the queue I first need to figure out a better placement for the VG - I did one run with the VG right about where the rear glass starts.

VHB... I haven't looked yet... The place I was interning at last summer had a large roll of it - so I imagine it can be ordered I don't know how much it will cost, however.

Originally Posted by Deezler

Where are you going to locate your "trip" in the model? I would think just before the roof line starts to bend downwards would be most beneficial...?

First test was around the top of the glass... Separation doesn't occur until about midway down the glass, so I'm wondering it they'll need to be placed on the rear glass itself...

Originally Posted by Deezler

What do you mean by streamlined foil? A raw shape to test? (i.e. not something done to the jetta?)

I modeled a NACA 0012 foil - nothing to do with the Jetta

Originally Posted by Deezler

Questions about your model:
- How did you obtain the geometry to build it? - It looks great btw. I would LOVE a copy once its all cleaned up!
- Did you model the curvature in the 3rd dimension? Specifically the gentle arc across the trunklid rear edge:

At the moment, I'm using a 2D model sketched off an image (as seen in my posted images). The fancy 3D model you've seen has not been used yet - it still needs processing to get it usable.

Nice tail lights

Originally Posted by Deezler

So you are running all these CFD simulations. What output are you getting other than a visual flow separation analysis for each iteration? Can you compute a Cd number of some kind also?

As of this instant, I'm mostly just getting visulization results. BUT, I have setup most of the models such that I can grab cD etc. with a little extra work... I don't have/know the equation off hand, but after I spend a few minutes to figure it out, it's a matter of implementing it into the model. Then, I can grab cD I'm not going to do that just yet as the equation is variable depending on geometry.

Originally Posted by Deezler

Seriously though, its rare find a study being done like this, with open data sharing, let alone for my own car... Sweet!

I'm not exactly sharing data - not that I don't want to, it's just I don't have anything... I am sharing the pretty pictures - open for discussion and interpretation We can compare a few things and then decide what is better, or if we can't determine so...

What are the specs of the rig you're using? I tried messing around w/ openfoam/some stuff from gmsh and my computer could not handle it. Oh, and I second the stuff Deezler mentioned. I'm interested to see how curving the sides of the spoiler would change the wake.

P4 3.2 GHz
896MB RAM (1GB total - 128 goes to video)
Whatever speed hard drive that comes in a hpzv5000 laptop
WinXP Home

I'm using Cosmos Floworks in Solidoworks... It's not the best solver - but it's not terrible... As of right now, I don't think it can do LES (Large Eddy Simulation) - so we won't see much in the way of eddies/vorticies.

I'm using a half scale model too - to reduce on computing time... However, I'm stupid and forgot to look up weather or not solidworks could do 2D cfd, which it can... Run time will be much faster now - while I'm still in 2D mode

I've never used OpenFoam, so I can't say too much.

Question: what objective function are we trying to minimize here? speaking in 3D terms -is it important to just minimize the VOLUMEof blue stuff or is it important to minimize the REAR CROSS SECTION of car that separation occurs from?

I can't say for sure at the moment... Optimally, there's no blue zone... What's better? Longer versus thinner? I'm not entirely sure...

As of right now, just take everything as general visualization Later, after finding the better iterations, I'll go back and see about getting barometric numbers for comparison. I'm not doing that now because of the time involved



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In other news, my use of my laptop is going to be cut a little short soon... My girlfriend's laptop took a crap, and she needs it for work...Her machine is identical to mine, so we're going to swap hard drives depending on who's using it. If I can't fix her old laptop tonight, she's ordering a new one that should be in by the end of the week.... Progress will slow down, temporarily

It's also getting colder, which makes working with fiberglass resin a bit more difficult :/