Rocket.addFins() does not support airfoil lift coefficient data with Cl=0 #54
Description
Use case
Try to add fins to a rocket object using the airfoil option:
FinSet = TestRocket.addFins(
n=3,
rootChord=0.077,
tipChord=47/1000,
span=0.104,
distanceToCM=-0.99586,
airfoil='NACA0012_Cl.csv'
)Contents of 'NACA0012_Cl.csv' are:
0, 6.86E-09
0.200712864, 1.05E+00
1.560796326, 0.0Expected result
Fins are added properly with no errors or warnings.
What happens instead
RuntimeWarning: divide by zero encountered in double_scalars FD = 2 * np.pi * AR / (cn *np.cos(gamac))
RuntimeWarning: invalid value encountered in double_scalars Cnalfa1 = cn * FD * (Af/self.area) * np.cos(gamac) / (2 + FD * ( 1 + (4/FD**2) )**0.5)
Furthermore, the resulting cldata created has a nan (not a number) everywhere a zero is expected.
[[0.00000000e+00 5.18408620e-09]
[2.00712864e-01 7.19089724e-01]
[1.56079633e+00 nan]]I believe the error from originates from calling cnalfa1 with cn=0.0 in line 610 of the Rocket.py file.
Applies to versions:
Master branch only, no releases yet.