Numerical code for lift coefficient

Hi guys,

I have been studying blade design using Blade Element Momentum theory and I have done axial and angular factor resolution, but I’m curious about numerical code for lift and drag coefficient in a function of angle of attack. What I did do is to extrapolate it one by one that wastes of time so I have been figuring out another possible way to predict them.

Do you know how I can form codes to predict the factors? Actually, literature I read mentions this, but it’s not quite clear about derivation.

Also, tip loss correction, F, is due to vortex loss at a tip section of rotor. Am I right that vortex (wake) loss occurs in both hub and tip section so one has to consider F in both section? please clarify my doubt

Any source I can look at please let me know

Thank you very much

Chat.

Hi Chat,

I’m not sure what all you are asking about–maybe it’s a language thing. Are you asking if there’s a way to compute the angle of attack for an airfoil? If so, there’s a freeware program from MIT called XFoil you can use. I think it will predict the lift and drag coefficients over the linear portion of the lift curve, but does not help with stall. If you are trying to extend the alpha range, you may want to try Craig Hansen’s AirfoilPrep spreadsheet. It also helps with calculations for delayed-stall due to rotation.

As for the losses, yes, you should calculate both tip and hub losses. My WT_Perf program does that.

Possible downloads:
http://web.mit.edu/drela/Public/web/xfoil/
http://wind.nrel.gov/designcodes/preprocessors/airfoilprep/
http://wind.nrel.gov/designcodes/simulators/wtperf/