Difference between Lift_(N), Fz_FF_(N) & Fz_sum_(N) (found only the last 2 in the documentation)

Questions, suggestions, feature requests, bug reports, feedback › Category: Questions › Difference between Lift_(N), Fz_FF_(N) & Fz_sum_(N) (found only the last 2 in the documentation)
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Benoît G.Benoît G. asked 1 month ago

Hi there,
I was wondering how the Lift and Drag are calculated, because they don’t seem to match either the body forces calculation nor the far field calculation. As an example, here are comparisons for 3 different states:

I figured CL and CD are calculated using Lift & Darg, but I can’t backtrack their computation using the body or FF forces. Also, which method is used to calculated the moments(L, M, N) ?

Thank you!

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Benoît G.Benoît G. replied 1 month ago

In case the picture doesn’t load:

alpha(°) beta(°) phi(°) CL CD Lift_(N) Drag_(N) Fx_FF_(N) Fy_FF_(N) Fz_FF_(N) Fx_sum_(N) Fy_sum_(N) Fz_sum_(N) Vx_(m/s) Vz_(m/s) V_(m/s)
-9 0 0 -0.34828 0.056443 -126.92 20.568 -17.475 1.67E-05 -125.73 -19.927 1.60E-05 -125.81 49.356 -3.186 50
-9 0 0 -0.34828 0.042061 -182.76 22.071 -25.164 2.40E-05 -181.05 -28.695 2.30E-05 -181.17 59.567 -2.3742 60
-9 0 0 -0.34828 0.038493 -248.75 27.493 -34.252 3.27E-05 -246.43 -39.057 3.13E-05 -246.59 69.576 -2.1728 70

1 Answers
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André Deperroistechwinder Staff answered 1 month ago

Lift and drag coefficients are calculated in the wind axes system using the forces in the Far-Field plane.
Moments are calculated by summation of the moment of forces acting on panels.
André

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