4. Module Documentation

Two classes are provided in the module: Polar and Airfoil. Generally, the Polar class is not needed for direct usage except for its constructor. All objects in this module are immutable. In other words, calling Airfoil.correct3D() creates a new modified airfoil object rather than editing the existing object.

4.1. Polar Class

A Polar object is meant to represent the variation in lift, drag, and pitching moment coefficient with angle of attack at a fixed Reynolds number. Generally, the methods of this class do not need to be used directly (other than the constructor), but rather are used by the Airfoil class.

Class Summary:

4.2. Airfoil Class

An Airfoil object encapsulates the aerodynamic forces/moments of an airfoil as a function of angle of attack and Reynolds number. For wind turbine analysis, this class provides capabilities to apply 3-D rotational corrections to 2-D data using the Du-Selig method [DS98] for lift, and the Eggers method [EJCD03] for drag. Airfoil data can also be extrapolated to +/-180 degrees, using Viterna’s method [VJ82]. This class also adds methods to read and write AeroDyn airfoil files directly.

Class Summary:

class airfoilprep.Airfoil(polars)

Constructor

Parameters:

polars : list(Polar)

list of Polar objects

Methods

initFromAerodynFile	Construct Airfoil object from AeroDyn file
correction3D	apply 3-D rotational corrections to each polar in airfoil
extrapolate	apply high alpha extensions to each polar in airfoil
blend	Blend this Airfoil with another one with the specified weighting.
getPolar	Gets a Polar object for this airfoil at the specified Reynolds number.
interpToCommonAlpha	Interpolates all polars to a common set of angles of attack
createDataGrid	interpolate airfoil data onto uniform alpha-Re grid.
writeToAerodynFile	Write the airfoil section data to a file using AeroDyn input file style.

Bibliography

[DS98]

Z. Du and M. Selig. A 3-D stall-delay model for horizontal axis wind turbine performance prediction. In 1998 ASME Wind Energy Symposium, number AIAA-1998-21. Jan 1998.

[EJCD03]

A. J. Eggers Jr, K. Chaney, and R. Digumarthi. An assessment of approximate modeling of aerodynamic loads on the UAE rotor. In Aerospace Sciences Meeting and Exhibit, number AIAA-2003-0868. Jan 2003.

[VJ82]

L.A. Viterna and D.C. Janetzke. Theoretical and experimental power from large horizontal-axis wind turbines. NASA TM-82944, National Aeronautics and Space Administration, Cleveland, OH. Lewis Research Center, September 1982.