Aero question; 'Serrations' on the leading edges.

This takes me back to Byglund again. I asked him about the raked tips on the 707-320 and the 727 and he off-handedly said, " Oh, we think that it kids the wing into thinking that it's thinner." Essentially the same answer came from a younger aero guru in my old group who explained the winglets and double winglets do the same thing. They increase the span without literally increasing the span...kidding the wing into thinking that it's longer. And reducing the area for tip vortices to form. Whitcomb also invented the "shock bodies" on the Convair 990 that bled the drag producing waves off the wing upper surfaces. Not terribly effective.

 

And how do vortex generators fit into all of this?

 

Thank you...

I remember the problems with the F-102 that were solved with the 102A version.
Area rule.

As I recall, the YF-102 would not even go supersonic before the changes.

 

T- Their first attempt was the XF-92A with a J-57 and she just had too much drag. The area ruled, wasp waisted F-102 with conical camber on the wings easily punched through the mach. The conical camber was area rule applied to a wing and had a dropped, conical leading edge which decreased the wing area the airflow say, thus decreasing drag. Both were applied to the F-102.
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My understanding is that the vortex generators, usually placed along the upper side of the leading edge of the wing, is to slow the air even further as it passes over the top of the wing thus increasing lift. (Something akin to an extended slat)

I also seem to remember something about enhancing boundary layer as well. .

I'm sure an expert will chime in shortly to straighten me out.

 

Also, on supersonic aircraft like the F4 Phantom and SR-71 Blackbird they have movable devices on the air intakes to slow the air down so it can be directed into the intakes.

It's possible that this is what the "vanes" are being used for on the F1 cars, to redirect air where they want it to go to enhance down force..

 

From what I learned about vortex generators is that the "rolling swirl" that they generated pushed the flow down on the wing surface and delayed separation thus maintaining laminar flow. Pretty neat, huh? I just made it up as I was typing. They fixed many problems on wings, stabilizers, and the 727 number two engine inlet.

 

There he goes again....
Thanks, I knew it was something like that.

 

Winglets are actually controlling the spillage of spanwise flow from the lower surface to the upper surface (high pressure to low pressure). This spillage of the lower flow around the tip is what creates the large tip vortices. Many early 'winglets' were just tip fences, e.g. 747-400. Aviation Partners were the first to introduce the concept of blended winglets (G-II, Hawker 800, 737, 767, Falcon) which not only controlled the tip flow but provided additional lift. They also now have a split winglet (up and down) operating on the newest 737NG's. Boeing, while ending up embracing the blended winglet idea on the 737's, has for the most part maintained that their raked tip geometry is just as efficient. This was first employed on the 767-400, and now also on the 747-8 and 787. However Boeing is apparently introducing a split winglet on the new 737Max.

VG's create turbulent flow in order to delay flow separation. Aft of the VG's there is no longer laminar flow.

 

In the center engine duct on the 727 , the throat of the duct took a sharp bend and it was getting lip stall because of the rapid curvature of the lower surface. The center engine was getting compressor stall at high flows so VG's were installed at the lip to get the air to "make the turn" instead of breaking away and stalling. So, it stayed attached to the duct and into the engine. I misused the word " laminar" and should have mentioned attachment that delayed separation. The first take off of the 727 sounded like a war going on when the center engine began a rapid sequence of compressor stalls. Wallick calmly reduced thrust on number two and kept going with the take off. No problem after VG's were installed.