Brian,

Bottom and top surface deturbulators has been a subject of discussion
between Sumon and me for a few years. He was against the idea for reasons
that were hard for me to grasp. But, later, when I did extensive oil flow
visualizations to find out why the present deturbulators were not working,
on a lark, I put oil on the bottom surfaces just to see if the transition
bubble was still there. I was shocked to see that the entire bottom wing
surface had the same non-streamed, mottled oil blotches as on the top
surface (and no hint of a bubble). Even without deturbulators, the bottom
surface was reaping the benefits of the leading edge tape step-down and (I
suppose) the modified flow pattern on the upper surface. At any rate, the
oil flows are clear and I wonder what would be achieved by altering
something so perfect?

BTW, I have a large number of these oil flow images at two speeds, 50 KIA
and 80 KIA. I plan to post them all with my interpretations when I get
the time.

Regards,
JEH

At 13:28 10 June 2008, Brian Bange wrote:
Whether or not anything comes of the research, the post is interesting
and
a lot more enjoyable to read about than what brand of wheel bearing
works
best in glider trailers etc. I think most of us follow the story with
interest and wish he and Dr. Sinha well.

I received an email from Dick Johnson about a month ago on another
subject
and he wrote "Maybe Deturbulators on the wing top surfaces, and
Turbulators on the wing bottom surfaces will be the next step?" So not
all the experts are completely shunning the deturbulator.

Brian Bange


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. How the deturbulator "detaches" the boundary
layer from the surface is a mystery and left to future generations of
physicists to explore.

The whole story reminds me actually of the Cold Fusion hype in the
early 90's: a desirable effect is found and described without
theoretical underpinning. In this case, the effect is found only on
one glider, Jim Hendrix' Cirrus and only in a small airspeed window,
make that exactly 51 knots. We are told that more research is needed
before other gliders can be blessed with this "textured tape
Deturbulator". Again, I'm skeptical by nature and this all just
smells of Voodoo science. The claimed L/D that "peaked" at 70 to 120
to 1 (Collum article) at least I can explain: over short distances in
convective air all our gliders reach those numbers. Hell, I flew last
weekend over 66 miles at an L/D of 125 without circling and at 90mph,
according to SeeYou. Maybe the reason is that I dumped my pee-bag out
the side window before that run and the hyper-viscous fluid affected
the drag of fuselage and empennage, who knows!?

This all is right now of no practical use to us. I could run all day
in Jim's Cirrus at 51 knots and still not make good speed going x-
country. In fact I would guess I spend about 30 seconds at that speed
on a typical 3 hour flight. Sorry for being so negative but again,
please show me the underlying effect. Saying we don't know right now
doesn't cut it. Come back when you can explain what you believe you
measured.
If this 'revolutionary' improvement is for real, Dr. Sinha will
shortly be a very rich man. Until then, good luck. His patent
application is pending and if you google the subject you will find
that nobody but the inventor has published on this subject. One would
guess that the aerodynamicists of the world would beat a path to his
door if they believed this to work.