Spoiler at back of a hatchback officially non-useless (SAE paper)

[Arragonis]

Originally Posted by ChazInMT

Vortex Generators, still officially useless 99.5% of the time.

Can we put them into the Unicorn Corral then ? Having a boxy hatchback I would love these to work but I have see 0.00% proof as of yet.

[khafra]

I hope nobody took my SAE cite to mean that just any VG anywhere on a vehicle would be beneficial. But this is not the only paper showing a benefit--there's more basic stuff, like Tombazis, N. & Bearman, P. W. 1997 A study of three-dimensional aspects of vortex shedding from a bluff body with a mild geometric disturbance. J. Fluid Mech. 330, 85–112.
It's clear that VGs at the back of anything but a full boat-tail will improve CdA, if done right--but it's probably hard or impossible to do them right with current commercially available VGs.

[California98Civic]

Originally Posted by khafra

I hope nobody took my SAE cite to mean that just any VG anywhere on a vehicle would be beneficial. But this is not the only paper showing a benefit--there's more basic stuff, like Tombazis, N. & Bearman, P. W. 1997 A study of three-dimensional aspects of vortex shedding from a bluff body with a mild geometric disturbance. J. Fluid Mech. 330, 85–112.
It's clear that VGs at the back of anything but a full boat-tail will improve CdA, if done right--but it's probably hard or impossible to do them right with current commercially available VGs.

Yup. That 62mpg Renault demo car used VG's but I noticed that they were of a special design, not like the commercial deltas even. They were thinner and they were mounted more cleanly, flush with the roof.

[Arragonis]

So the ones off ebay, they don't work then - or at least there is no actual, real, significant proof of an improvement ?

[California98Civic]

Originally Posted by Arragonis

So the ones off ebay, they don't work then - or at least there is no actual, real, significant proof of an improvement ?

Well there is this article, which seems very thorough. But their application was about directing air to a spoiler, and the placement was quite precisely thought out for that application. I would think taking their conclusions and trying to apply it to my car would be fraught with the very great danger of wasted time and money. I'm trying to learn not to get carried away like that. And the Renault VGs seem far smaller, thinnner, more flush, and doubled-up in parallel vertical arrangements. Many precise specs there. I am not up to it.

[InsightfulRay]

Originally Posted by ChazInMT

OK, Sorry to kill the party here, but there is a huge leap from a very highly designed spoiler for one particular vehicle, to Vortex Generators and Tabulators....

They aren't really on the same planet. So don't go making a case for those VG gimmicks to work based on this paper, it isn't even in the same realm. It isn't even a hatchback. VGs have been shown to have a very small benefit in some very specific cases, anywhere on the back part of a minivan style vehicle is not one of them.

Vortex Generators, still officially useless 99.5% of the time.

I agree with your point about comparing a specific spoiler to vortex generators. Not the same beast. I have a set of Airtabs on my Mini Cooper and have gone through 3 fill-ups since the mod. One thing they absolutely do well is keep my rear hatchback window MUCH cleaner. Before the mod, I was going through quite a bit of rear washer fluid even in the Spring and Summer to keep good visibility through the rear window. My fuel log says they're worth 2-3% improvement in mpg. I tend to keep my speed down on the interstate so another driver might see more of an improvement at 60-70 mph speeds. I'm way over in the far right lane doing 55 mph most days.

[HighMPG]

Instead of protruding VG has anybody studied up on dimpled ones?

[Arragonis]

Linky ?

[euromodder]

Originally Posted by Arragonis

Linky ?

To glider zig-zag and dimple tape : right here

They're used to keep the airflow longer on a glider's wings - i.e. delay separation through turbulation. Standard fitment on some gliders.

[gone-ot]

...does this mean they will only "work" during the "glide" portion of your P&G driving (wink,wink)?