Trebuchet03's JettKamm (2000 VW Jetta)

[MetroMPG]

Are you using that photo to get the Prius lines? I think there's some lens distortion in that one that exaggerates the roof angle.

[trebuchet03]

Originally Posted by MetroMPG

Are you using that photo to get the Prius lines? I think there's some lens distortion in that one that exaggerates the roof angle.

So, as of yet, I have not modeled directly against the Prius....

The last cross section I posted was a simple line, from the trailing edge of my trunk to the first tangent point on my roof line. I'm thinking, if I go this route - that'd be the way to manufacture it - because I'll need a false windshield and I'm ill equipped to make optical compound curved plastics...

I'd have CFD for you, but I accidentally killed the power to my laptop before going grocery shopping - my laptop died mid calculation

How's this picture?

[basslover911]

Originally Posted by Deezler

p.s. I plan on mounting VGs on the roof, just for fun.

I have them on my Mazda 6, and as far as I know nobody with a Mazda 6 (4cyl Auto) has been able to hit the mpg figures that I have been hitting...

Today new high of 42mpg with winter blend gas and 75 degrees outside...

I DO attribute Vg's to some of that success; here is testing I did on them-
--- "vortekz" Generators Tested!! --- Pictures!! - GasSavers.org - Helping You Save at the Pump

[MetroMPG]

I think this one's better: http://www.crunchgear.com/wp-content...yota_prius.jpg



I measure a 9% angle (from horiz.) from the highest point of the roof to the end of the spoiler in that pic, vs. 10% for the silver car and 13% for the red car (after correcting to make the wheels level)

[trebuchet03]

Thanks Metro - I'll work on that shortly...

I've been going back and forth between the cut plots (what I've been posting) and working on the 3D model... The 3Dmodel is HUGE, and really bogs down my machine... Saving is a 5 minute operation, and I've already crashed once I've got maybe 100 or so features to repair - even then, I don't know if it will work

Boundary layer pictures


Those points (some highlighted) indicate where the boundary layer WAS in my last boundary layer post - this shows improvement Angle, according to SW, is 18.18 degrees... As before, red=55mph or more, blue=0mph or less

Here's the wave plot, just to keep things organized



Metro, where are you measuring the 9 degree angle? I'm getting ~15 degrees


When I measure from tip of spoiler to very top, I get something ~9 degrees....

[Bicycle Bob]

Originally Posted by MetroMPG

I think this one's better:
I measure a 9% angle (from horiz.) from the highest point of the roof to the end of the spoiler in that pic, vs. 10% for the silver car and 13% for the red car (after correcting to make the wheels level)

For a first guess, I start with the maximum angle at any area on the back of 15 deg. On the bottom, where air can't flow in from below, I start around 5 degrees, depending on several factors.

[ChrstphrR]

Since Cd got you that model via my original digging ... I'm just curious now, trebuchet03 ... what format is that model saved as -now-?

Maybe I can help and do some of the trimming down on the model to help you cut down the size of it, so it won't bog your machine so. No ulterior motives for me, being that I get direct benefit from ANY work on Jetta models you get good results with, after all.

[lunarhighway]

you may want to have a look at The-Blueprints.com - 25990 blueprints online

not all drawings are in hi res but most cars have several drawings wich should allow you to extrapolate certain angles rather accurate... even the low res sketches can be of use if you import them into a vector drawing softwae (like the free package inkscape) and draw a curve anong the pixeled edges.... wich you can tha scale and overlay on a different drawing

[Katana]

Cool stuff but not sure i understand the images, the different colours represent different air speeds, if so which colour is "best", do you want the air moving quickly over the surfaces?
Would be cool to see one done with a teardrop shape showing how a "perfect" aerodynamic shape looks in the program.

[trebuchet03]

Originally Posted by tasdrouille

This thread is really interesting. Care to give a quick shot at just a small 45 degrees lip spoiler that would be as high as the boundary layer is thick (edit: on the baseline model) at the rear edge of the trunk?

Setup

I modeled with the cut plot visible, but I turned the plot off so you could see the result.


The next two wave plots show velocites from 0-55mph - anything above is saturated black. This makes seeing the BL and separation zone much easier.

Baseline


45 degree Result


Separation happens earlier... Intuitively, this makes sense.