Vortex strake device; reducing aerodynamic drag

[aerohead]

Originally Posted by freebeard

You'll know they work when you see a second and third example out on the Interstate.


This is interesting because it does the opposite of the Difflow difusser, collecting rather than dissipating the turbulence behind the rear wheels.

*There would still be turbulence across the entire width of the device behind it.That area is already a torture chamber for air,so it probably can't make matters worse!
*Water spray would likely be completely arrested 'within' the footprint of the device with only 'air' escaping through the central opening.A good reason for using it right there.
*If any sort of 'jet' is created at the central opening,the low pressure of the orifice might be communicated forward,inducing the vans side flow to 'hug' closer to the body,which could also help reduce the turbulence there along with its spray.
*It's way out ahead of nothin'.

[euromodder]

Originally Posted by aerohead

Vortex generators were designed to allow flow reattachment at steep angles,onto a trailing structure.
Truck vans have nothing behind them to reattach to.

They don't need that if they can make it quite literally out of thin air with energised air.

Keeping the tailgate closed also helped as it created a bubble of air in the bed - where physically there's nothing there (but air).

Rear spoilers on a trunk that end up on the template also reduce FC, despite the sharp drop on the rear window.

Simple, flat end-plates on sticks reduce FC when the plates are sized to what a full boattail would be like at that distance.


So apparently, you don't necessarily need full-featured, physical hardware right up to the tail to better streamline a vehicle.

You likely won't get the maximum benefit out of them, but you also don't get the various inconveniences of a physical boattail.


If these vortices can enclose a boattail-bubble of air, you've boattailed the truck with ... nothing but air.

[kach22i]

Originally Posted by euromodder

If these vortices can enclose a boattail-bubble of air, you've boattailed the truck with ... nothing but air.

That is the concept in a nutshell.

You would think that because they paid big bucks to buy time at the Langley wind-tunnel they would at least share some stills of the smoke.

Maybe these vortexes are too violent to photograph well, seems like a lost investment with diminished public relations value.

I really like their wheel covers.

The rear undercarriage treatment I have not seen before, very odd.

[aerohead]

Originally Posted by euromodder

They don't need that if they can make it quite literally out of thin air with energised air.

Keeping the tailgate closed also helped as it created a bubble of air in the bed - where physically there's nothing there (but air).

Rear spoilers on a trunk that end up on the template also reduce FC, despite the sharp drop on the rear window.

Simple, flat end-plates on sticks reduce FC when the plates are sized to what a full boattail would be like at that distance.


So apparently, you don't necessarily need full-featured, physical hardware right up to the tail to better streamline a vehicle.

You likely won't get the maximum benefit out of them, but you also don't get the various inconveniences of a physical boattail.


If these vortices can enclose a boattail-bubble of air, you've boattailed the truck with ... nothing but air.

I have no data from empirical research which demonstrates that the 'bubble' can exist until you've run the boat tail out to 80% of total length.
*Prandtl couldn't do it
*Rumpler couldn't do it
*Jaray couldn't do it
*Dornier couldn't do it
*Klemperer couldn't do it
*Lay couldn't do it
*Heald couldn't do it
*Elliot couldn't do it
*Kamm couldn't do it
*Fachsenfeld couldn't do it
*Arado couldn't do it
*Messerschmitt couldn't do it
*Hoerner couldn't do it
*Morelli/Pininfarina couldn't do it
*NASA couldn't do it
*Volkswagen couldn't do it
*Continuum Dynamics couldn't do it
*AeroVironment couldn't do it
*Renault couldn't do it
*March couldn't do it
*Oldsmobile couldn't do it
*Aerosmith couldn't do it
*Rutan Brothers couldn't do it
*General Dynamics Electric Boat Division couldn't do it
*Lockheed 'Skunkworks' couldn't do it
*W.A.Mair couldn't do it
*---------------------------------------------------------------- ad infinitum!

[racprops]

Funny as I tried a idea like these...

Did NOT seem to make any difference...

The ones I bought look like this:



Rich

[aerohead]

Originally Posted by kach22i

I first posted this in the Unicorn Corral because I thought that was were debatable topics were supposed to go. Turns out I was wrong about that somehow, so to gain a wider audience and hopefully discover with other's help the proof that these work as patented, I now re-post it here.

Vortex strake device and method for reducing the aerodynamic drag of ground vehicles Patent Number US7255387 B2
Patent US7255387 - Vortex strake device and method for reducing the aerodynamic drag of ground ... - Google Patents



If I were to think of this as a rain diverter on a roof, such as found over an entry-way I'd say yes, it works.

However we are talking air pressures and vortexes which have a life far from and beyond the moving body.

What say yee?

I found this quote in the forum.

http://ecomodder.com/forum/showthrea...html#post10971


Fences and strakes are used on aircraft, so there might be something to this patent in my opinion.

We also see similar (but not exactly the same) features on more and more racing cars, and they are being regulated by the rules because they work, right?

Question:
1. What tests have these devices passed?

2. Where are they being used?

I await your research, and I'll do a little as well when I can get to it.

Hucho,in his book offered,that short of a boat tail,nothing really worked on tractor trailers except a box cavity.

[8307c4]

Yeah I took the $20 I was going to spend on these silly things and put it in the gas tank, wow what a difference that made!

[mallrat]

Regarding Rich's van:

Those are spaced a ways apart, seem to work best on a boxy shape spaced at 3 per foot. I put them on an 88 Accord and went from a consistent 30 mpg to a consistent 32mpg with no other changes. Couldn't get proper spacing on my pickup, but they still significantly reduced the dust signature on gravel roads, plays in the mud too much to get a good mileage average.

[mallrat]

Originally Posted by racprops

Funny as I tried a idea like these...

Did NOT seem to make any difference...

The ones I bought look like this:



Rich

Airtabs has a template to help place them approximately 3 per foot in a straight line, that'd probably give you better results.

[racprops]

The instructions I remember said to place them a few inches from the edge.

Rich