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Airfoil orientation on Wind Turbines

  • 28-08-2014 8:41am
    #1
    DJW11
    Registered Users, Registered Users 2 Posts: 188 ✭✭


    Hi all,

    Looking to clear something up in my mind to do with the aerodynamics of wind turbines.

    The underside of the airfoil, the (pressure side), is'nt that always to the front facing the oncoming wind, I understand that it see's the relative velocity of the on coming wind but with regard to which side of the airfoil is to the front, it is always the underside isn't it, as you would look at any conventional airfoil pattern.

    Thanks for any input.


Comments

  • #2
    Capt'n Midnight
    Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 94,272 Mod ✭✭✭✭Capt'n Midnight


    Nope, I don't understand the question.

    so here's this
    https://en.wikipedia.org/wiki/Wells_turbine
    The Wells turbine is a low-pressure air turbine that rotates continuously in one direction in spite of the direction of the air flow. Its blades feature a symmetrical airfoil with its plane of symmetry in the plane of rotation and perpendicular to the air stream.

    it doesn't have a front or back


  • #3
    DJW11
    Registered Users, Registered Users 2 Posts: 188 ✭✭DJW11


    Capt'n Midnight wrote: »
    Nope, I don't understand the question.

    so here's this
    https://en.wikipedia.org/wiki/Wells_turbine

    it doesn't have a front or back

    Sorry if I didn't explain properly, maybe a picture will help, if the airfoil in the picture was flipped with the convex shaped side facing the oncoming wind, would it work the same?


  • #4
    Capt'n Midnight
    Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 94,272 Mod ✭✭✭✭Capt'n Midnight


    Depends

    the one I linked to above works either way

    some aircraft can fly upside down , but with the nose higher to change the angle of attack on the wing - it all depends on the symmetry of the cross section of the wing

    anyway since most horizontal axis wind turbines can turn into the wind it's not an issue.

    with vertical axis turbines it's a big issue since you've got (very roughly) 1/3rd of the turbine being moved by the wind, 1/3rd with the wind not doing useful work, but still creating wind load which requires stronger supports and 1/3rd moving into the wind reducing the speed of rotation


  • #5
    [Deleted User]
    Posts: 5,238 ✭✭✭ [Deleted User]


    DJW11 wrote: »
    Sorry if I didn't explain properly, maybe a picture will help, if the airfoil in the picture was flipped with the convex shaped side facing the oncoming wind, would it work the same?

    Not as well. The concave portion is where you get the start up torque. The convex portion is riding the low pressure trail and creating lift, pushing the blades back and slowing the wind. Leading edge is rounded to reduce noise and turbulence and trailing edge is sharp to reduce resistance.


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