Humpback Whales and Rudders...

[Big Red]

From Scientific American, Aug '04 there is an article about the performance of the lumpy humpback whale flippers. They have all these bumps on the leading edge:

http://www.sailhawaii.com/Images/whales/Pecl.jpg

Apparently, this makes them more hydrodynamic. Tests by a chap called Frank.E.Fish and his associates have revealed that a humpback flipper provides 8% more lift and 32% less drag, and can stand a 40% greater angle of attack before stalling than a normal fin!

Mr Fish who has patented the idea (guess whales don't have lawyers) says it has a wide range of applications. Airplane propellers and wings, helicopters and ship rudders. I dare say keels too.

So what are the chances the next Australia's err, Americas Cup winner is sporting a whale fin rudder? Hmmm, comments...

[ 09-30-2004, 05:09 PM: Message edited by: Big Red ]

[JimD]

Could be the most lucrative patent since velcro. So is that a whale in the photo or a capsized prototype? :D

[Big Red]

Heheh, as if wing masts could get any uglier, just wait... :rolleyes:

Do women swim better than men? :eek: :D

[ 09-30-2004, 07:13 PM: Message edited by: Big Red ]

[ahp]

Women are definatly faster. I even took swimming lessons at the Y even though I already knew how to swim. I just couldn't catch'em. Afterwards I still couln't catch'em.

[N. Scheuer]

Ya'but! Does the main part of a Humpback's fin have a Laminar Flow Section?

Laminar Flow sections exhibit stall at increased angles of attack significantly later, and also exhibit less drag than NACA Sections. Of course I don't expect the Whale gives a rip for NACA Sections neither! But it wouldn't hurt to ask one, would it?

I once read that Dolphins could swim so fast because their skin had a "spongy" layer of fat that would let it "ripple" under the effect of slight water presure changes. At the time I thought that maybe our Nuclear Subs ought to have rubber "spongy" skins for the same purpose.

Moby Nick

[Big Red]

Actually I thought subs did have a spongey layer? Something to do with absorbing sonar?

Was hoping one of the resident designers would pipe in with an opinion. I am afraid you lost me at laminar flow... :confused:

Anyone out there nearly ready to launch and wants to epoxy some egg shells to his rudder, in the name of science? ;)

[JimJ]

They are probally called "vortillons" used to control the water flow. The are used on a few aircraft to control the airflow across the wing.

Maybe they work at loooow speed also!!

Google "vortillons"

[Dave Williams]

I have rowed and sailed a LOT! of miles in a 22ft skin boat. I do believe that she goes easier, with less effort, than a comparable hard shelled boat ever would. I do have some experience to compare her with. Her skin is soft and flexible and her frame gives comfortingly in a seaway. That's what I have seen for what it's worth.

Dave

[brian.cunningham]

Vortex generators

Here's a page on what they do
http://www.microaero.com/pages/v_howvgswrk.html
http://www.microaero.com/Images/What-VGs-do.gif

[imported_Daniel]

(guess whales don't have lawyers) :D :D :D

[ahp]

Brian, have you ever noticed the triple row of stubby little airfoils sticking out of the wings, and on the verticle stablizer of some of the older airliners, such as the 727?

[brian.cunningham]

I could be wrong, but I think those just house the surface control motors.
http://www.panamair.org/Aircraft/boeing727.htm
http://www.panamair.org/newsite/aircraft/boeing727/727100white.jpg
We're talking about the ones on the trailing edge, right?

[ 10-02-2004, 01:24 PM: Message edited by: brian.cunningham ]

[Bruce Hooke]

No, I think AHP is talking about something closer to the leading edge. I recall seeing what I think he is talking about. They are maybe a few inches long and an inch or so tall. IIRC, in plan view they are a cross section of an airfoil (or even just a fin of sheet metal), and they are flat topped. They are set at an angle to the leading edge. It does seem likely that each one would be designed to generate a tiny votex.

Here's a picture:

http://www.microaero.com/ImageGallery/Images/C172.jpg

[ 10-02-2004, 02:11 PM: Message edited by: Bruce Hooke ]

[Bruce Hooke]

Brian,

What you are talking about may be, based on this web page (http://www.pilotfriend.com/flight_training/AERONAUTICS/OTHER%20WING%20ADDITIONS.htm) , "wing fences", which apparently work as follows.


Wing fences are fin-like vertical surfaces attached to the upper surface of the wing, that are used to control the airflow. On swept wing airplanes, they are located about two-thirds of the way out towards the wing tip and prevent the drifting of air toward the tip of the wing at high angles of attack. On straight wing airplanes, they control the airflow in the flap area. In both cases, they give better slow speed handling and stall characteristics. I'm not sure if this is what you had in mind or if you are talking about the more bulbous structures between the flaps on some jets. I'm not sure what they do.

[brian.cunningham]

Bruce,
Those are the vortex generators that Big Red asked about, and I posted about.


Originally posted by Bruce Hooke:
Brian,
...or if you are talking about the more bulbous structures between the flaps on some jets. I'm not sure what they do.That's what I was talking about, I'm not sure what ahp was talking about.

[ahp]

What I was talking about are stubby little airfoil sections, sticking out of the upper wing surface perhaps three inches, and each about three inches cord. There would be about three rows of these, a dozen or more to the row just ahead of the wing flaps.

On the vertical stabilizer there was a similar triple row ahead of the rudder hinge. The purpose I believe was to permit higher angles of attack without flow separation.

[Bruce Hooke]

ahp -- If they are just ahead of the flaps then I'd hazard a guess that they are indeed designed to increase the angle that the flaps can be placed at before seperation starts to take place on the flap. If they were to prevent seperation on the whole wing then I think they would be closer to the front of the wing, as in the picture I posted above. But, this is basically just speculation on my part.

P.S. Unless I'm much mistaken the "stubby little airfoil sections" you are talking about are the "vortex generaters" Brian talked about and posted a diagram of way back near the start of this thread.

[ 10-02-2004, 11:19 PM: Message edited by: Bruce Hooke ]

[garyspear]

Let's be carefull here. Water is a significantly more viscous fluid than air. and the flow characteristics don't scale linearly. :D Think smooth for control surfaces my brother. we do not wish to generate an inordinate amount of heel in the boat. ie make lift neutral. :D but then again when you reach 150 knots in a sailboat we can modify this argument a bit. IMHO.

[Big Red]

Yeah I think that Fish guy kind of hinted that they worked at lower speeds and offered the whale the ability to turn faster. I am sure having your fins cavitate is really unpleasant ;) I thought they might be good then on craft that need to tack fast like racing dinghies?

Then I was wondering if the same principal was related to the bulbous bows seen on some cargo ships? To break up the pressure wave that forms there. Now I am thinking do boat screws have this kind of feature?

[ahp]

Yes Bruce, these are I believe vortex generators and allow greater flap and rudder angles before flow separation occures.

I don't notice them on the newer airliners. I wonder why.

[Meerkat]

Originally posted by brian.cunningham:
Bruce,
Those are the vortex generators that Big Red asked about, and I posted about.

</font><blockquote>quote:</font><hr />Originally posted by Bruce Hooke:
Brian,
...or if you are talking about the more bulbous structures between the flaps on some jets. I'm not sure what they do.That's what I was talking about, I'm not sure what ahp was talking about.</font>[/QUOTE]Some of them serve 2 functions. One function is to house actuators ("servos") for flight controls such as flaps and ailerons and the other bits of Boeing pioneered "disassembling wing" structure. Their other function, especially the solid ones, are to act as resonance dampers so that the wing won't flex across the span as much. They are fairly critical to avoid overstressing the wing spar.

Lockheed, at least on the C-141 "Starlifter", uses a dynamic resonance damping system that continually adjusts the ailerons to dampen flexing. I've seen videos of a plane with the system "on" and "off", and, when off, the plane looks like it's flapping it's wings to stay aloft - very dramatic!

[ 10-03-2004, 05:08 PM: Message edited by: Meerkat ]

[Meerkat]

Originally posted by ahp:
Yes Bruce, these are I believe vortex generators and allow greater flap and rudder angles before flow separation occures.

I don't notice them on the newer airliners. I wonder why.Better airfoil technology and, while they did a good thing, they also induced additional fuel economy robbing drag.

One thing not mentioned thus far are winglets. While they add drag, they also control transverse airflow off the tip of the wing and it's getting sucked under the wing which causes even worse drag. They add as much as 15-20% in fuel economy, thus justifying their existance in a big way.

[Paul Pless]

If you really want an education (or perhaps, more confusion) check out the vortex generators found sprouting all over F1 cars. From the tip of the nose to the engine exhaust tips those cars are all about controlling airflow and developing helpful votices on top of the car, on the bottom of the car, and even inside the car.

[brian.cunningham]

Originally posted by garyspear:
Let's be carefull here. Water is a significantly more viscous fluid than air. and the flow characteristics don't scale linearly. :D Think smooth for control surfaces my brother. we do not wish to generate an inordinate amount of heel in the boat. ie make lift neutral. :D but then again when you reach 150 knots in a sailboat we can modify this argument a bit. IMHO.In order to "scale" the results, the Reynolds # needs to be maintained.

(noun) A dimensionless number used in fluid dynamics that relates the inertial and fluidic properties of the system. Flow properties such as laminar and turbulent flow and boundary layer thickness are determined by the Reynold's number. Low Reynold's numbers generally relate to flow conditions where viscous effects dominate. High Reynold's numbers relate to fluidic systems with predominantly inertial characteristics. In most ink jet systems, internal ink flow is in the low Reynold's number regime. www.trident-itw.com/resource-center/glossary.html (http://www.trident-itw.com/resource-center/glossary.html)

[JimJ]

The small vertical ones on the top surface of the wing are vortex generators. These are designed to energise the air to create a laminar flow over the surface. Have a look on the top surface of the wing of a Westwind II. Here is a good article about VG on light aircraft;
http://www.avweb.com/news/reviews/182564-1.html

http://www.aerospaceweb.org/question/aerodynamics/generators/emb120_wing.jpg

The large vertical ones, generally just one, are wing fences. These are designed to prevent the span wise flow of the low pressure air. These are seen on the early model Falcon 20. Have a look at;

http://www.airliners.net/open.file/309882/M/

Vortillons are small protrusions from under the leading edge of the wing. An article is at;
http://oea.larc.nasa.gov/PAIS/Concept2Reality/deep_st all.html (http://oea.larc.nasa.gov/PAIS/Concept2Reality/deep_stall.html)

Here are the vortillons on a Embraer Legacy.

http://www.ainonline.com/Features/pilotreport03/leg4.jpg

[ 10-04-2004, 09:11 AM: Message edited by: JimJ ]

[ahp]

While on the subject of "Things on Wings" does anyone remember the General Dynamics Convaire 990? This four engine airliner had "Speed Pods", large conical projections off the traiing edge, two or three per wing. The were supposed to make the 990 go faster than the 707, DC8, and the 880 for the same fuel consumption. It didn't.

A number of airlines placed orders with the condition that it would have a certain fuel consumption at a certain speed and Convair could make one or the other but not both at the same time. Orders were cancelled and the only thing that saved General Dynamics was a Federal Loan Guarantee.

American Airlines bought a bunch of them at bargin prices. I traveled on them many times. It was a nice airplane from the passager's point of view.

[Meerkat]

Originally posted by brian.cunningham:
In order to "scale" the results, the Reynolds # needs to be maintained.
A boat's hull/keel is a foil operating in the equivelent of a hypersonic regime per Reynold's Numbers and due to the viscosity of the working environment. Sails are also subject to similar analysis, although, to date, they're decidedly subsonic ;)

[ 10-04-2004, 03:43 PM: Message edited by: Meerkat ]

[Amos Bechtel]

>>A boat's hull/keel is a foil operating in the equivelent of a hypersonic regime per Reynold's Numbers<<

This is something I have often wondered. At what Reynolds number does a boat hull operate? I have never taken the time to do the calculations. Is this even relevant? If it is operating in a hypersonic regime, then are all the conventional airfoils incorrect for this use? I guess I know just enough about aerodynamics to be dangerous.

Thanks - Amos

[Alan D. Hyde]

Some winglets,

in the wind tunnel:

http://oea.larc.nasa.gov/PAIS/Concept2Reality/graphics/fig025.jpg

And in the air:

http://oea.larc.nasa.gov/PAIS/Concept2Reality/graphics/fig032.jpg

Here's a link to an essay:

http://oea.larc.nasa.gov/PAIS/Concept2Reality/winglets.html

***

Alan

[brian.cunningham]

Originally posted by Meerkat:
</font><blockquote>quote:</font><hr />Originally posted by brian.cunningham:
In order to "scale" the results, the Reynolds # needs to be maintained.
A boat's hull/keel is a foil operating in the equivelent of a hypersonic regime per Reynold's Numbers and due to the viscosity of the working environment. Sails are also subject to similar analysis, although, to date, they're decidedly subsonic ;) </font>[/QUOTE]Ah, there's several variables that can be used for a Reynold's number.

This page has a real good analysis
http://www.boat-links.com/foils.html

R = V * L / kv
where V is the velocity
L is the length (fore and aft) of the foil
V is the velocity
kv is kinematic viscosity
kv = ~10-5 ft2/sec for water and ~10-4 ft2/sec for air

[Amos Bechtel]

Thank you for the formula and the link. I was missing the kv for water although I really hadn't looked very hard. Now I'll go home and play around with that a little.

Amos

[Phil Young]

Was watching a show on the ABC called "Inventions from the shed" a week or two ago, and they had a fan, with in effect winglets on the outer edge of the fan blades. Apparently much more effective. Make sense, they stop the air "leaking" off the end of the fan blades, so its all pushed in the right direction. The suggestion was that it would increase the efficiency of helicopter rotors, airplane props, etc etc. Can't see why it wouldn;t work on a boat prop too-a bit like a Kort nozzle attached to the end of the prop blades.