"Herb" wrote:

Am I the only one who is completely underwhelmed by this "exiting"
news that comes well timed after the June article in SSA magazine by
Bill Collum? Is anybody able to explain to me even in basic terms
what the physics behind the claimed effect are? Mr. Collums
explanations are not making any sense, he just throws aerodynamic
terms around and invents new ones such as "slip layer" that nobody
else has ever observed.

Herb,

I'm glad the Soaring article on Sumon Sinha's "deturbulator" technology got
you thinking. I am more engineer than reporter, so I apologize if my
explanations were a little unclear. I promise you that the term "slip layer"
is not a product of my over-active imagination (which can, admittedly, run
wild from time to time; wait until you read about my vision of a mid-21st
century sailplane in a future edition of Soaring), but is a formal concept
inherent in computational fluid dynamics. The "slip effect", for example, is
a recognized phenomenon of pipeline fluid flow and effects processes
utilizing non-Newtonian fluids in the petroleum, chemical, and food
preparation industries. Exactly how and under what conditions this effect
may apply to Newtonian fluids (i.e. "air") interacting with a single
boundary wall (i.e. "a wing") is open to question, and that is what Sumon
and Jim are investigating. Essentially, if they are able to successfully
leverage this effect in aerodynamic applications, it is possible that skin
drag may be reduced or virtually eliminated by forcing the boundary layer to
detach from the wing surface. In such a case, the energy-laden boundary
layer will not be in direct contact with the wing surface, but will instead
"slip" over a layer of static air, preventing the boundary layer from
"dumping" it's energy through micro-scale interactions with the surface over
which it is flowing. Obviously, as I mentioned in my recent article, a great
deal more research is required before any conclusions can be drawn. Only
time (and money) will tell if this phenomenon can be practically applied to
sailplane aerodynamics. I applaud Sumon and Jim for their innovation and
perseverance, and wish them well.

Thank again for your comments.

Bill Collum
"Tango X-Ray"




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