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Drag Calculation from Matlab

  1. Sep 23, 2011 #1
    I am trying to estimate the Thrust and Torque generated by a propeller blade by utilising the Blade Element Theory. I was able to get Lift but not Drag. Below is the code generated by Matlab.

    The calculation procedure is,

    T1 = twist pitch ratio
    RTheta = root pitch angle
    Phi = atan(V/(Omega*r))
    ro = 1.225 (density)
    C = 0.15 m
    Cdo = 0.008 (zero lift drag)

    Alpha = RTheta + T1*r - Phi

    Here the twist is negative which makes the tip to have a small pitch angle.

    for i = 1:3:132 % Forward Speed of the Aircraft
    for j = 1:3:39 % rps (rpm/60)

    syms r

    omega(j) = 2*pi*j;
    W2(i,j) = i^2 + (omega(j)*r)^2;
    Alpha(i,j) = deg2rad(RTheta) + deg2rad(T1)*r - atan(i/(omega(j)*r));
    CD(i,j) = Cdo + K*(a*Alpha(i,j))^2;

    W2CD(i,j) = expand (W2(i,j)*CD(i,j));

    Drag(i,j) = double(0.5*ro*Cr*int(W2CD(i,j),r,Hr,D/2));

    As the calculation is run, I always gets a message saying below details,

    ??? Error using ==> sym.maple at 87
    Error, (in IntegrationTools:-Utils:-Simplify) too many levels of recursion

    Error in ==> sym.int at 51
    r = reshape(maple('map','int',f(:),[x.s '=(' a.s ')..(' b.s ')']),size(f));

    Error in ==> New at 74
    Drag(i,j) = double(0.5*ro*Cr*int(W2CD(i,j),r,Hr,D/2));

    I would like to know how to get the drag values. I have tried every possible method, but I still get this message.

    Furthermore, independent to the above question, is it OK to get the real part of a complex number to calculations?

    Say if,

    R = 2*D

    D = 0.45 + 09i

    and if you take only the real number then,

    R = 0.90

    Is it correct? or possible? if so or not, is there is an exception where you can take R=0.90?
    Advice me on both questions please. Thank you in advanced
  2. jcsd
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