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Ssecond moment of area for a aerofoil.

  1. Nov 24, 2008 #1
    Hi was wondering if anyone could help?

    i am after the method of calculating the second moment of area of a aerofoil shape of which I have all the cordinates. It has a consant thickness of 1mm and lookig for values for

    1)I_xx
    2)I_yy
    3)I_xy


    the equation for the half the erofoil section is

    y=2.391x^5 + 6.784x^4 +7.193x^3-3.647x^2+0.839x+0.011



    3. The attempt at a solution


    now i know that I_xx =integral y^2 DA

    and DA= 1/COS(THETA), HOWEVER CAN BE APPROXED TO 1 HENCE DA=1.dy

    after that im stuck : (
     
  2. jcsd
  3. Nov 24, 2008 #2
    Can you enlighten me with the axis of symmetry if the above equation is only half of the aerofoil?
    Also, where does the curve begins and where does it end? Y is zero when x=0, and it goes to 14 when x=1, and 45000 when x=4.
    Are x and y in metres or in mm?

    as long as y is measured to a line passing through the centroid and parallel to the x-axis.

    not when x is small and dy/dx is small. Here is can be approximated by dx.

    Thus it would seem risky to consider approximations without the knowledge of the domain and range of the curve.
     
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