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aerohead · 02-23-2009, 08:25 PM

After many months,I located the NASA paper I believed would shed some light on the whale tubercles.The paper is entitled "Investigation of Acoustic Effects of Leading-Edge Serrations on Airfoils," by Alan S.Hersh,Paul T.Soderman,and Richard E.Hayden.The paper appeared in JOURNAL OF AIRCRAFT,Vol.11,No.4,April,1974,pp.197-202,Copyright,1974.

The report is pretty technical.15 references are listed,going back to 1928.The research stems from observations of the aero-acoustic behavior of the owl wing,with it's leading-edge "comb",downy wingtop,and serrated trailing edge.

The research was conducted at NASA's low noise BBN acoustic windtunnel.

The crux of the research is that the "tubercles" eliminate "tones" created by periodic vortex shedding, by blasting the flow into turbulent flow and random wake turbulence.

Early roughening of wings produced increased drag,but Soderman was able to tune the serrations so as not to aggravate lift or drag while elliminating noise.

The test data is basically about frequency and sound pressure level.Of note,is the fact that above 10-degrees angle of attack,the comb makes no difference,as the wing is stalled at that point,and turbulence is random and without "tones".

Since "hearing" is so important to both whales and owls,the adaptations appear to be less about aerodynamic or hydrodynamic efficiency,and more about feeding efficiency.

The paper is a good read and I thank Paul for sending me a copy.

P.S. I believe PBS Television has free Pod-Casts of it's programs available at PBS.ORG. If you haven't seen "Raptor Force" on NOVA,you're missing out!

02-23-2009, 08:25 PM	#23 (permalink)
aerohead Master EcoModder Join Date: Jan 2008 Location: Sanger,Texas,U.S.A. Posts: 16,228 Thanks: 24,375 Thanked 7,357 Times in 4,757 Posts	Finally found NASA paper on "tubercles" After many months,I located the NASA paper I believed would shed some light on the whale tubercles.The paper is entitled "Investigation of Acoustic Effects of Leading-Edge Serrations on Airfoils," by Alan S.Hersh,Paul T.Soderman,and Richard E.Hayden.The paper appeared in JOURNAL OF AIRCRAFT,Vol.11,No.4,April,1974,pp.197-202,Copyright,1974. The report is pretty technical.15 references are listed,going back to 1928.The research stems from observations of the aero-acoustic behavior of the owl wing,with it's leading-edge "comb",downy wingtop,and serrated trailing edge. The research was conducted at NASA's low noise BBN acoustic windtunnel. The crux of the research is that the "tubercles" eliminate "tones" created by periodic vortex shedding, by blasting the flow into turbulent flow and random wake turbulence. Early roughening of wings produced increased drag,but Soderman was able to tune the serrations so as not to aggravate lift or drag while elliminating noise. The test data is basically about frequency and sound pressure level.Of note,is the fact that above 10-degrees angle of attack,the comb makes no difference,as the wing is stalled at that point,and turbulence is random and without "tones". Since "hearing" is so important to both whales and owls,the adaptations appear to be less about aerodynamic or hydrodynamic efficiency,and more about feeding efficiency. The paper is a good read and I thank Paul for sending me a copy. P.S. I believe PBS Television has free Pod-Casts of it's programs available at PBS.ORG. If you haven't seen "Raptor Force" on NOVA,you're missing out!