Airfoil polar file

The airfoil polar file defines the aerodynamic coefficients of an airfoil. All airfoils need to have at least one polar in order to perform aerodynamic analyses. 

In order to perform an aerodynamic analysis, all aifoils used by a model need to have at least one polar. This is because Ashes uses the BEM algorithm, which requires aerodynamic coefficients to calculate the aerodynamic loads on the blades.

The image below shows part of a polar file. Note that the first column (in grey) is only indicating the line number and is not part of the actual text file. 



The first line contains the Reynolds number of the polar, followed by a tab and the text 'Re number'. If no Reynolds number is specified, a value of -1 has to be written.

The rest of the file is divided into 4 columns. The first column gives the angle of attack, in degrees. The next 3 columns give the lift coefficient Cl, drag coefficient Cd and pitching moment coefficient Cm, respectively. These three coefficient are dimensionless.

An exmaple of the format can be obtained by exporting the polar file from an existing airfoil in Ashes.

Note: if you export an existing polar, you will get additional information in the file before the Reynolds number definition. This is only informative and and is not used by Ashes.

More information about airfoils is given in the following video: https://www.youtube.com/watch?v=xZL7A55aE-0