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Old 06-23-2012, 05:40 PM   #81 (permalink)
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Originally Posted by aerohead View Post
Years ago we talked about this,but maybe at MaxMPG which is now defunct.
In 1990,at World of Speed,a guy was there,who I believe had just received a MS in aeronautical engineering.He had a streamliner which had a sphere mounted on a shaft which 'preceded' the streamliner's nose.
The premise was that the streamliner would ride within the turbulent wake of the sphere kinda like a rocket-powered torpedo riding within some of it's own exhaust shunted out the nose,or a Russian ice-breaker with 'bubbler.'
I have no record that the bulb was a success.
It's possible that it was too small,and already embedded within the Prandtl surface of discontinuity,hidden from the source-flow.Don't know.
It's certainly possible to do such a thing,but with any crosswind component,it would lose performance,as the vehicle would no longer be occulted by the wake.
The other thing is that you're looking at at least a double-deformation of the forebody flow field and most messengers publish that air should make only a single pass over a structure with zero circulation,and zero separation.The bulb concept would kinda violate the rulebook.
There is something similar called aerospike (not the rocket engine) that is used on some missile systems, which is a section of a sphere (dish?) on an extended pole at the nose of the craft. I've seen them used on sub-launched missiles to create a cavitation bubble that the missile flies thru until it breeches the surface, and have seen them also on atmospheric launched missiles, presumably for the same concept of pre-punching the hole in the air with a smaller frontal area and then letting the bigger body fly through the expanding cone of cavitated air created. if it could be made retractable, it could be worth a try in automotives.

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Old 06-23-2012, 10:53 PM   #82 (permalink)
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There is something similar called aerospike (not the rocket engine) that is used on some missile systems, which is a section of a sphere (dish?) on an extended pole at the nose of the craft. I've seen them used on sub-launched missiles to create a cavitation bubble that the missile flies thru until it breeches the surface, and have seen them also on atmospheric launched missiles, presumably for the same concept of pre-punching the hole in the air with a smaller frontal area and then letting the bigger body fly through the expanding cone of cavitated air created. if it could be made retractable, it could be worth a try in automotives.
http://www.scribd.com/doc/40528006/Full-Text







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Old 06-24-2012, 05:47 AM   #83 (permalink)
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Quote:
Originally Posted by bnmorgan View Post
There is something similar called aerospike (not the rocket engine) that is used on some missile systems, which is a section of a sphere (dish?) on an extended pole at the nose of the craft.
presumably for the same concept of pre-punching the hole in the air with a smaller frontal area and then letting the bigger body fly through the expanding cone of cavitated air created.
Something similar is done on the Russian K36 ejection seat to protect the pilot from extreme windblast during high speed ejections : a pole pops up at the front of the seat.

Those are all high speed appliances though.
Have a look at the Mach numbers for the light areas in the graph.
Even the ones in water are for - relatively - high speeds, as that's in a far thicker medium.
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Old 07-18-2012, 09:53 PM   #84 (permalink)
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I read somewhere a while back where the Russians had developed a super high speed sub that shredded the water in front of it self to fly through the cavitized layer, anybody hear of that one , supposedly went supersonic. In the aircraft world just read where somebody put a prop spinner from a constellation on a DC 3 or similar plane and picked up a good bit of speed and much better engine cooling, whats going on there i wonder, whole nother world of course put eventually all these things tie in together,
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Old 07-19-2012, 07:11 PM   #85 (permalink)
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I believe the submersible was actually a torpedo, and it formed a cavitation bubble around itself or some such.

Aha, here is a brief description: Supercavitation - Wikipedia, the free encyclopedia

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Old 07-20-2012, 06:26 PM   #86 (permalink)
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The thing for us is that air cannot undergo a phase change as in an underwater device where cavitation could occur.Air is gaseous and remains so.
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Old 07-20-2012, 10:23 PM   #87 (permalink)
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Gotta point there, I guess another way is to duct air from a high pressure area to a lower one, sort of how they cooled the engines in the Shelby Daytona Coupes, cant think of any ordinary cars that do that , probably because of weather issues, I was also wondering if anyone has tried to relocate their mirrors to the door so the air can flow around the windsheild better, maybe sit the mirror out of the main air flow, maybe back a bit , and while ii am thinking about it has anyone ever tried the flaps in front of the rear wheels like SAAB cars used to have,
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Old 07-21-2012, 05:34 AM   #88 (permalink)
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while ii am thinking about it has anyone ever tried the flaps in front of the rear wheels like SAAB cars used to have,
Check out recent cars - quite a few already have small deflectors in front of the rear (and front) wheels.
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Old 07-21-2012, 02:29 PM   #89 (permalink)
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mirror relocate

a number of low-drag concept cars had their mirrors well aft of the A-pillars and further out from the side glass to get them into slower air.
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Old 10-08-2012, 10:19 AM   #90 (permalink)
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Quote:
Originally Posted by radioranger View Post
while ii am thinking about it has anyone ever tried the flaps in front of the rear wheels like SAAB cars used to have,
The Mercedes ML 350 has curved front air deflectors / spats / spoilers / whatever you want to call them in front of the front tires.

Looks to move some air to the side of the car and some under it.

I am attempting to mimic this using plastic PEX tube bend supports from Grainger as the mounting point for approx. 3" lawn edging coming down.

Grainger Item # 10A675

Seems it takes advantage of the air dam affect to the farthest sides of the car to route air around un aero things like the tires and suspension. But leaves the center of the air dam higher to not force ALL below bumper flow to the sides.

I will create thread with pics when I can. And let you know if it seems to help. I may then try same for rear tires.

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