Anti Vortex Plates instead of boards?

Discussion in 'Hydrodynamics and Aerodynamics' started by DennisRB, Oct 7, 2011.

  1. DCockey
    Joined: Oct 2009
    Posts: 4,728
    Likes: 322, Points: 83, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    Probably there for handling, stability and/or stall characteristics reasons.
     
  2. Doug Lord
    Joined: May 2009
    Posts: 16,654
    Likes: 326, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ----------------------
    From wikipedia "Learjet 60":

    The final aerodynamic improvements to the Model 60 included the creation of the distinctive "Ogive" winglet trailing edge. This lengthening of the chord near the interface of the winglet and the wing improved the interaction of the wing’s pressure spike with the winglet’s pressure spike. The result was a significant lowering of the drag in this area and a significant improvement of the wing's efficiency. On the prior “Longhorn” wing the interference between the winglet and the wing nearly canceled the effects of the winglet. The single ventral fin was also replaced with two ventral fins that Learjet called "Delta Fins" to improve stall characteristics and promote aerodynamic stability.
     

    Attached Files:

  3. bscally
    Joined: Sep 2011
    Posts: 17
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Seattle

    bscally Junior Member

    787 wing in flight

    My understanding...

    Is that the 787 wing is a blended structure.
    With variable stiffness.

    Attached is an in flight photo of a 787 wing.

    Now I might not know the name for it but the bent up end bit looks terribly like a winglet.

    The cleverness of Boeing's design ( dock conversation with a non 787 team Boeing wing designer involving beer ) is that as the load changes so does the shape of the wing, and you need more wiglet at high loads for high efficiency.

    Sounded plausible to me.

    --

    If there is anyone who can correct my terminology and understanding I would be pleased to listen.

    Brian
     

    Attached Files:

    Last edited: Oct 11, 2011
  4. DennisRB
    Joined: Sep 2004
    Posts: 1,268
    Likes: 25, Points: 48, Legacy Rep: 228
    Location: Brisbane

    DennisRB Senior Member

    Are you suggesting that the winglet in your pic is just a product of wingtip bend and that it disappears when the plane has stopped? I am pretty sure that is just a normal winglet. All airliner wings flex under flight. The are holding up a couple hundred tonnes.
     
  5. DCockey
    Joined: Oct 2009
    Posts: 4,728
    Likes: 322, Points: 83, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    YouTube video of the 787 roll-out. The wings can be seen from a variety of angles. The wing tips both rake back and sweep up, though the sweep up is much less than with older "winglets".
    http://www.youtube.com/watch?v=ajdbu7UZDS8
     
  6. Petros
    Joined: Oct 2007
    Posts: 2,936
    Likes: 140, Points: 63, Legacy Rep: 1593
    Location: Arlington, WA-USA

    Petros Senior Member

    On winglets with significant vertical areas it tends to decrease directional stablity, that is makes the tail less effective. Another thing they do is increase the dihedral effect of the wing, which can give some very annoying flying characteristics. So the anahedral ventral fins compensate for both of the changes the winglets cause.

    With the more modern wing tip treatments there is less effect on directional stablity.
     
  7. bscally
    Joined: Sep 2011
    Posts: 17
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Seattle

    bscally Junior Member

    The tips seem flatter preflight than in flight.
    The wing has a nominal ~2.5m upwards deflection in flight, but that measurement is at the base of the tip.
    The maximum upwards deflection is supposed to be be ~9m

    I went to watch the first 787 take off for it's delivery flight and I think the tip deflects up more.
    However all my pictures are of the body of the plane and I don't have a single one with the wingtips in!

    Now it could all be an illusion of angles...

    http://www.youtube.com/watch?v=6JV_91Ifwdo&feature=related

    You look and judge. Compare 2:30 .. coming in to to landing with 5:10 for the unloaded wing.


    Brian
     

    Attached Files:

  8. Petros
    Joined: Oct 2007
    Posts: 2,936
    Likes: 140, Points: 63, Legacy Rep: 1593
    Location: Arlington, WA-USA

    Petros Senior Member

    Wings have been designed around "areoelastic" properties of the structure from the beginning. We can just do it better now. If you happen to be at the airport and can get even with the leading edge of the wing of an older 747 (the one without the wingles), sight down the length of the wing. It makes all kinds of strange bends, that all more or less disappear when the wing is lifting the aircraft while flying. It makes a nice smooth arch while it is in the air.

    Now we can do it better with better modeling of the areo loads along the span of the wing, developing the best most efficient shape while in the air.
     
  9. DennisRB
    Joined: Sep 2004
    Posts: 1,268
    Likes: 25, Points: 48, Legacy Rep: 228
    Location: Brisbane

    DennisRB Senior Member

    I see. When combined with wing flex I can see how they would become more effective when needed in such times as take off and landing and when the plane is heavier.
     

  10. tspeer
    Joined: Feb 2002
    Posts: 2,285
    Likes: 252, Points: 83, Legacy Rep: 1673
    Location: Port Gamble, Washington, USA

    tspeer Senior Member


    Style and branding play a bigger part that you might think.

    A simple span extension will do the same thing as a winglet, with less wetted area. You also get a reduction in stall speed from the increased wing area. So from a purely aerodynamic point of view, this is the way to go.

    But winglets are useful when there are other constraints. For example, if the span is extended, it may not be possible to get into the same gates at the airport. And it is possible to achieve the same increase in effective span with less wing-root bending moment (and therefore less structural beef-up) with a winglet than a span extension.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.