Les Ward

I have been wondering how all those little fins on the top of wings function .
I assume its to direct airflow in various directions to create more lift.

Aloha Les

BMatthews

The little ones that are about 1 inch square or so and stick up?

Those are turbulators. They are too small to direct the air. The idea is to pay a small drag penalty and turbulate the airflow so it'll stick to the wing's surface better and delay the stall during the nasty parts of landings and takeoffs when the speed is low and the lift needs are high.

probligo

There has been some pretty good discussion about this just in recent times.

If you do a search on "winglets" and "tip plates" down this board you should pick up on most.

Very interesting topic I think. Been playing with them (with some success) for about the past ten years. Can't even now that I am sure one way or the other (for or against).

The theory is to reduce the size of the tip vortex thus increasing efficiency.

and what Bruce said, more so than me

Les Ward

Thanks guys ,
I am new to this hobby and appreciate the input , Thinking about building my next plane ( # 3 ). Possibly a gas Spad.

Aloha, Les

HalH

My Feedback: (12)

The turbulators referred to above are actually called vortex generators. They have been used for many years. They were on some early jet fighters on the wings and also on the fuselage near the horizontal stabilizer. The B-720 and B707 had many of them on the wings. As I remember there were over 50 on each wing. They were added to prevent spanwise airflow.

Tall Paul

There's a surprising amount of span-wise flow even at high speeds occuring behind the local shock position.
We experimented with generators on the Tristar. Typical flow patterns looked like these..
Didn't install them ultimately. A combination of NIH and looks bad..

Spindizzy

Its not just the big airliners that have them, we got a Beechcraft Duke in the hangar right now ( piston engine twin,pressurised ) which is smothered in vortex generators, along the wing and up the fin. Apparently also used on old transports like the Beverly which had a pretty much square end to the fuselage. The vortex generators actually cause the laminar airflow to curve further round the rear boxy end than would have if it had no vortex generators. This delays the separation of the airflow from the fuselage thereby reducing the turbulent airflow which causes drag.

Sean

What next, Kucheman carrots

SALMONBUG

My Feedback: (1)

it increase energy in the boundary layer and makes the flow better adhering to profile

BMatthews

That's an amazing pic Paul. Interesting that the tufts in the first shot are flowing OUTWARD. I would guess into a localized separation bubble that was eliminated by the vortex gen's.

And what's NIH mean?

SALMONBUG

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very interstesting pic, I would be intersted to know at what EAS it has been taken

Tall Paul

The b/w was taken at a 1.9 w/delta... probably about .85 Mach.
Here's another odd one....

Tall Paul

And from the Lear....
The disturbed puddle was created by the "good idea" pylon fairing.
Didn't get into production...

e-bird

Did you change your handle Tall Paul from Sparky Paul
Even the B47 had tublators and that was a long time ago. CU

Tall Paul

ISTR one of the reasons we didn't adopt the vortex generators was they are an admission that wing is designed wrong.
That's one of the reasons they show up on planes which entered service without them, they're fixes.. relatively inexpensive though.
Another thing we tried was the McDD "engine ears"' those vanes on the wing engines on the DC-10.
Although there was a benefit to the stall speed, it wasn't sufficient to warrant purchasing the license to use them.. and NIH (Not Invented Here)
MOF, when we tested them, we made them out of 1/2" Lexan, so they wouldn't be visible from the ground.
Interesting flow patterns off them at the stall...
I have some film footage around here someplace...

BMatthews

I'm just a casual aerodynamicist with no formal training or even work time in the industry but I always cringe when I see vortex generators even though I know what they are there for. To me it always seemed like a small Bandaid on a sucking chest wound....

I do love the fact that even with all the windtunnels and other research tools available in the end you were still taping tufts of yarn to the planes and flying them in the "real" world.

SALMONBUG

My Feedback: (1)

The b/w was taken at a 1.9 w/delta... probably about .85 Mach.
Here's another odd one....


that's what I tought, what we saw is a sonic shock wave

Tall Paul

Here's a Mach wave.... and -forward- flow!

Trapnell

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VG's are used on some multi-engined light twins to lower Vmca while those on some large transport aircraft may be used to delay separation, decrease drag at high transonic speeds. They tend to reduce the magnitude of the shock wave produced at Mforce divergence. Interesting how they work at low and high speeds!

causeitflies

Are all of them called turbulators or are some called fences? I thought the fences redirected the airflow while turbulators....well turbulated it.

Trapnell

My Feedback: (1)

Vortex generators (vg's) turbulate (add energy) while fences reduce spanwise flow by redirecting (or excluding the low-pressure area on the outboard/downwing side). Another type of device seen is the vortelon. Invisible at high speeds, it adds energy to the flow at low-speeds by taking advantage of the spanwise flow.