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Lowering Air Resistance



 
 
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  #1  
Old February 23rd 06, 05:19 AM posted to sci.space.tech
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Default Lowering Air Resistance

Hi, I wanted to mention this article I read, about a newly discovered
way to reduce air resistance:

http://www.physorg.com/news11095.html

No flames, plz -- I just wanted to ask if anybody knows enough about
this effect to say whether it could be used to make a better scramjet
or rocket.

I was thinking scramjet in particular, due to its prolonged contact
with atmosphere at high mach conditions. But while this cylindered
surface would delay transition to turbulence, it might likely increase
overall drag. Therefore, would it be worth it?

Are there some circumstances where reducing turbulence is more
important than reducing drag? Could the interior of a scramjet engine
be such a case?

Comments?

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  #2  
Old February 26th 06, 07:44 AM posted to sci.space.tech
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Default Lowering Air Resistance


manofsanATyahoo.com wrote:
Hi, I wanted to mention this article I read, about a newly discovered
way to reduce air resistance:

http://www.physorg.com/news11095.html

No flames, plz -- I just wanted to ask if anybody knows enough about
this effect to say whether it could be used to make a better scramjet
or rocket.

I was thinking scramjet in particular, due to its prolonged contact
with atmosphere at high mach conditions. But while this cylindered
surface would delay transition to turbulence, it might likely increase
overall drag. Therefore, would it be worth it?

Are there some circumstances where reducing turbulence is more
important than reducing drag? Could the interior of a scramjet engine
be such a case?

Comments?


I read the article you linked to. I am not a subscriber, so I couldn't
read the original source.

http://snipurl.com/my0w

They want $23 to sell me the PDF file. I think that is too much.

Somebody needs to précis the article better than the PhysOrg.com
source.

I googled the article title and found one better description of the
research.
http://focus.aps.org/story/v17/st6

"... "Since the mid 1950's roughness elements have been known to
trigger transition [to turbulence]," Fransson says. But "we put in
roughness elements, and we show that we can delay transition. This is
very new." He suggests that a similar strategy might suppress chaotic
behavior in situations ranging from lasers to fusion plasmas.

"What is really slick about it is it's a passive strategy," in contrast
to complex schemes that "actively" eliminate turbulence after it has
developed, says Edward White of Case Western Reserve University in
Cleveland, Ohio. But he cautions that the clean experimental result may
not capture what happens in the real world. George Karniadakis of Brown
University agrees that the new result is a "good contribution," but he
suspects that the disks will cause extra pressure drag that may
overwhelm any reductions. Fransson says the disks only increase
pressure drag by 3.5% but that the team hasn't yet measured the net
drag. ..."


  #3  
Old March 15th 06, 08:41 PM posted to sci.space.tech
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Default Lowering Air Resistance

It may be useful in some aircraft designs, but laminar flow airfoils
have always been rather vulnerable to minor surface dirt and other
factors that might alter airflow. I have doubts about this helping in a
scramjet; supersonic airfoils are likely to be well beyond the laminar
flow regeim.

 




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