airfoilprep.Polar.extrapolate

Polar.extrapolate(cdmax, AR=None, cdmin=0.001, nalpha=15)

Extrapolates force coefficients up to +/- 180 degrees using Viterna’s method [3].

Parameters :

cdmax : float

maximum drag coefficient

AR : float, optional

aspect ratio = (rotor radius / chord_75% radius) if provided, cdmax is computed from AR

cdmin: float, optional :

minimum drag coefficient. used to prevent negative values that can sometimes occur with this extrapolation method

nalpha: int, optional :

number of points to add in each segment of Viterna method

Returns :

polar : Polar

a new Polar object

Notes

If the current polar already supplies data beyond 90 degrees then this method cannot be used in its current form and will just return itself.

If AR is provided, then the maximum drag coefficient is estimated as

>>> cdmax = 1.11 + 0.018*AR