I am designing a propeller using the BEM model and running an iterative program on octave, but when I add the prandtle tip correction the efficiency increases instead of what should happened which the efficiency decreases. can some one may be give me insight into which could be wrong.


f=(N_blade*1-(dr(i)/rad))/(2*(dr(i)/rad)*sind(theta));
fac(k,i)=(N_blade*1-(dr(i)/rad))/(2*(dr(i)/rad)*sind(theta));

F=real((2/p)*acos(exp(-f)));
Fac(k,i)=real((2/p)*acos(e^-f));


a_new=(((4*F*sind(theta)^2)/(sigma_r(i)*Cn(k)))-1)^-1;
b_new=(((4*F*sind(theta)*cosd(theta))/(sigma_r(i)*(Cl_n*sind(theta) - Cd_n*cosd(theta))))+1)^-1;

this is the part of the correction factor in the code.