Vortex strake device; reducing aerodynamic drag
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 http://patentimages.storage.googleap...814-D00001.png http://patentimages.storage.googleap...814-D00003.png 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 Quote:
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. |
This seems simple enough to test, although I do not believe that my Forester is sufficiently boxy! :D
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These vortex strakes have been verified in a full scale wind tunnel.
here is a link to the company that is commercializing them Solus - Vortex Strakes |
Im sure this legitimate but there is some info missing for those curious about it. These are wind speed specific devices there must be applied air pressure for correct operation. Alot of things that work on airplanes dont do so well at less than 100 mph so remember this when testing. for low speeds it may require 50% more pitch, or surface area etc. etc.
I cant remember which plane but they basically disturbed the air around the whole fuselage so the craft could use a shorter runway. sorta like an extra air cushion under that absorbs major leading edge pressure loads. |
Seeing that it targets semis I would assume the speed range they target is 35 mph to 70 mph. Of course I'm sure the speed they optimize the most for would be 65mph because that would be the speed most long haul trucks travel most of their miles at.
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http://www.solusinc.com/images_inv/vortexstrakes2.gif http://www.solusinc.com/images/sorht/Strakes2Med.jpg Yes, I think this is it because another Patent of Richard M. Wood is being presented by Solus (see below). I'm a little frustrated by the lack of detail on the above. However more detail is in the larger PDF: http://www.solusinc.com/pdf/2003-01-3377.pdf Solus - Cross-Flow Vortex Traps http://www.solusinc.com/images/TrapsProSm.jpg Patent US6986544 - Cross flow vortex trap device and method for reducing the aerodynamic drag ... - Google Patents http://patentimages.storage.googleap...117-D00000.png Both inventions are depicted in the small PDF/Flyer: http://www.solusinc.com/pdf/flyer.pdf |
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Couldn't they have used a real semi with a short trailer? Also, according to http://www.solusinc.com/pdf/2003-01-3377.pdf: Quote:
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cross flow vortex trap gap treatment device (front of trailer) http://ecomodder.com/forum/attachmen...6&d=1371063702 vortex strake device http://patentimages.storage.googleap...814-D00001.png undercarriage flow treatment devicehttp://ecomodder.com/forum/attachmen...8&d=1371064109 Back to my studies! |
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Length is an important factor, so changing it would require corrections - and those would first need to be calculated as well. The corrections required when using models in windtunnels are well known, OTOH. |
Vortex strakes
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In his first English translation,back in his section on commercial vehicles,he gets into some of these type of devices.He seems to dismiss them, as their origins are in aerospace applications which in ground proximity fail to provide results as in free flight. Vortex generators were designed to allow flow reattachment at steep angles,onto a trailing structure. Truck vans have nothing behind them to reattach to. And base pressure on the back of the van is a function of the pressure at the separation point.Perhaps the induced vorticity channels a bit of extra kinetic energy into the wake from a very thick boundary layer present at the back of the van. It's a good question. |
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http://ecomodder.com/forum/attachmen...1&d=1371064109 This is interesting because it does the opposite of the Difflow difusser, collecting rather than dissipating the turbulence behind the rear wheels. |
what say
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*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'. |
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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. |
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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. |
boat tail bubble
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*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! |
Funny as I tried a idea like these...
Did NOT seem to make any difference... The ones I bought look like this: http://i922.photobucket.com/albums/a...ps85d3bde9.jpg Rich |
say ye
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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!
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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. |
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The instructions I remember said to place them a few inches from the edge.
Rich |
More complete instructions under the "about" tab at Airtab: Aerodynamic fuel savers for truck, tractor, trailer, bus, RV. Not trying to spam or shill, I just figure they have a better explanation and I don't need to retype it here.
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Well these are based on this:
Airtabs™ should be installed as close as possible to the back (trailing) edge of the vehicle. If the Airtabs must be moved forward to avoid rivet heads etc, keep the wide edges of the Airtabs within 12-18 inches of the back for optimum performance. Airtabs are effective shielding gaps or reducing turbulence entering undesirable areas. Any vehicle component with an edge that is 90 degrees to the airflow is a possible Airtab® location provided that location receives an adequate supply of relatively undisturbed airflow. Examples: forward of wheel wells, slung tool boxes, trailer skirts etc. Airtabs are also effective on roof trailing edges of automobiles with a rear window slope exceeding 30 degrees. For ALL applications, ensure that the leading (wide) edge of the Airtab® is absolutely flush with the mounting surface. |
Also this
"Install Airtabs 3 per foot which is one every 4 inches on center. Airtabs are 4.76” long, 3.25” wide, and 1” high. Metric: 12cm long, 8.2cm wide, 2.5cm high. Spacing is 10.1 cm on center. Increase spacing to avoid rivet heads, lights, grab bars etc. Do NOT decrease spacing as this may decrease performance." I rechecked and I need to put back a few... I had so call expert tell me I had too many...and I removed every other one on the sides. BUT I had been running them for a couple of years and with so small a improvement calmed could never tell if they or my extra ground effect add ons did ANY good. I was hoping they would help the van... Rich |
Try this:
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Interesting a whole 3% improvement...he would have to done something like 20 test runs to prove so a small improvement and I would then as him to remove the generators and retest 20 to prove that the 3% went away with out them.
NOT worth my time to even bother with them. Rich |
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If it were my van, I'd run the column straight up from the front edge of that side marker light, about as many as I could fit without spacing them too close together. Of course it isn't mine, so do as you see fit. :) |
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That's three percent on an already aero car, a boxy van would probably do a bit better. But it'd still be hard to notice right away. |
Well as I still have them I will replace them in the missing spaces.
Can't hurt. Rich |
Vortex generators are known to improve lift on aircraft wings, enabling lower takeoff and landing speeds, better climb rate, while reducing stall speed. So, using this technology, for a given acceptable stall speed, they would enable an otherwise smaller wing, which in turn would mean higher cruise speed. This happens due to better attached flow over the wing.
Julian Edger shows some improvement in fuel economy, attached flow on the rear glass and deck, and perhaps less noise. Noise is a good indicator of turbulent and detached flow, so less noise would be consistent with smoother air flow. Vortex generators can be make for virtually no cost: Using two-sided adhesive tape such as carpet tape, and bent bits of aluminum, one could make small VGs out of, say, a used beer can. Just cut ~1" X ~1" rectangles, bend 90 degrees at centerline for an L shape, then trim one corner (which will be the leading edge) to rounded shape with a fingernail clipper. (If a beer can skin is too thin, use thicker material from a hardware store such as aluminum ducting for furnaces and chimney flues, etc.) Attach two-sided tape to the untrimmed side of of the L, and stick to the car surface at ~15 degrees off of flow direction, making V shapes with sets of VGs. Google (http://www.microaero.com/ImageGaller.../ig_index.html) for vortex generators for airplanes, and see how they are attached at normally turbulent flow areas, such as inside the angle of horizontal and vertical fin, wingroot, etc. On a car, one might imagine tuft testing of VGs where ever there is detached flow, such as various places on the hood, roof, rear glass, in front of and behind wheel wells, on undertray (Securely attached GoPro camera would be good for this.), etc.. So, for less than a dollar's worth of carpet tape, a used beer can, some yarn tufts and bits of scotch tape to attach, and with a buddy in a chase car with a camera, you could do all sorts of testing. Consider: Edger's 3% fuel economy improvement may not be much in itself, but then he only applied VGs to a tiny portion of his car--the rear window. What would happen if he'd gone whole hog and tested everywhere the tufts showed bad flow? One might imagine 3% here, 2% there, 1% someplace else, and pretty soon we're talking about significant fuel savings. |
I agree they work great when used correctly and wind tunnel tested and all the science and math is done and specially on air craft flying at over 100 MPH..
But like those silly wings stuck on many cars they do not work at normal legal road speeds. (Under 100 MPH) I think I would have better luck with a wrap around air wing that pulls air into the back of the van, like those old rear window cleaners used on station wagons, they help fill the hole behind the back end. Rich |
"It depends" on your driving routine. Lots of stop-and-go driving, or otherwise under 35 mph? Aerodynamics aren't going to help you much. Long stretches at sustained speeds over 45mph? More likely to see a return, especially on boxy vehicles and OTR tractor trailers as shown in some of the early posts. On the commercial vehicle side, a full boattail or "Trailer Tails" may show greater returns, but they also have other drawbacks like somewhat complicated loading/unloading, extra weight, and more likely to be damaged in the truckstop parking area. Standard fenders and bumpers have a hard enough time surviving :)
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Another cheap trick to make VGs is to use clear plastic corner protectors for drywall, as sold at Home Depot. It's a clear plastic strip with an L shape cross-section with sides ~3/4" high, comes in maybe 8' lengths, to protect outer corners of sheetrock wall surfaces in high traffic places like your kitchen. Hardly costs anything, and you could make dozens of VGs out of just one strip.
Being clear, if you can find a good and durable clear two-sided tape, you could stick these onto your car and still see the paint underneath, a sorta stealth application not too noticeable. Or, apply with glue gun? Clear Shoe Goo? Or, whatever works durably in weather, but is removable later without damaging the paint. I suspect a Coroplast undertray might be a great place to experiment, if you had a GoPro camera to record the tuft tests, and a secure mount for the camera. |
I agree , if I start seeing them on the highway I'd take note, this is almost 10 yr;s old no ,
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FE is a "box" funtion, ie: length x width, where length is TIME and width is the amount of SAVINGS.
Thus, a long TIME x small SAVINGS can still be beneficial, provided the TIME element is sufficient. |
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Either the trucking companies have not spent 10 minutes perusing Hoerner, NASA, or Hucho, or they cannot be bothered. The r&d facility for a major trucking manufacturer is about 4 miles from my house. They have an open house weekend every so often, which I've attended. I know for a fact that they have Hucho in their library, as I borrowed it via interlibrary loan. Do their products show much, if any, aero improvement as is common knowledge from the above-mentioned sources? Not really. These people are willfully ignorant, or just blow it off, or maybe they mess with pissants while being trampled by elephants. Sorry about the rant. But, basic vehicular aero optimization has been known and published for about 80 years now, and not many with the power to make changes act accordingly. It's pathetic. |
Also a lot of stuff out there that truly deserves to be labeled "snake oil", many drivers and trucking company executives just lump everything in there and figure if the OEMs don't put it on or the EPA doesn't require it, it must be bunk. The Owner/Operators that are trying to save fuel and money have a lot of information to wade through, much of it false.
I think the consumer figures "if it worked, the manufacturer would install it" and the manufacturer figures "if the consumer wants it, they would demand it or install it themselves." |
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