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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? |
#2
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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
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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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