1. Airfoil library file

The airfoil library file contains the coefficient data required for aerodynamic calculations. All of the airfoils which are referred to must be included in a single file; i.e. whether or not they are part of a wind turbine. The airfoils may be listed in any order. Airfoils which are not referred to will be ignored.

Comment lines may be included on any line, as in other input files. Blank lines between airfoils will at present be ignored, but it is recommended to use comment lines instead. Blank lines at other locations in the file will be interpreted as input lines and the default values will be used.

For each airfoil, the following data groups must be given.

1.1. Airfoil identifier

CHAIRF

  • CHAIRF: character(32): Airfoil identifier

1.2. Airfoil table extension parameters

IATEXT ATAIL1 ATAIL2 ANOSE1 ANOSE2 RNOSEC

  • IATEXT: integer: Flag for extending the table to deep stall regime

    • = 1: Extend the table

    • = 0: Do not extend the table

  • ATAIL1: real: tail angle between a line perpendicular to the flow and the line from the tip of the wedge, low (negative) angles of attack \(\mathrm {[deg]}\)

  • ATAIL2: real: as ATAIL1, but for high (positive) angles of attack \(\mathrm {[deg]}\)

  • ANOSE1: real: nose angle between a line perpendicular to the flow and the line from the tip of the wedge, low (negative) angles of attack \(\mathrm {[deg]}\)

  • ANOSE2: real: as ANOSE1, but for high (positive) angles of attack \(\mathrm {[deg]}\)

  • RNOSEC: real: ratio of the nose radius to the chord of the airfoil \(\mathrm {[1]}\)

1.3. Airfoil table size parameters

NRE NGEO DSIN

  • NRE: integer: Number of Reynolds numbers with coefficient data

  • NGEO: integer, default: 0: number of points describing the airfoil geometry

  • DSIN: integer, default: 0: flag for user-defined dynamic stall initialization parameters

    • = 1: User-defined dynamic stall initialization parameters will be given below

    • = 0: No user-defined dynamic stall initialization parameters will be given

1.4. Airfoil data

One block per Reynolds number, i.e. NRE data blocks

If only one block is given, the data will be used for all Reynolds numbers. For Reynolds numbers outside the range of Reynolds numbers given, the data for the closest Reynolds number will be used; i.e. flat extrapolation.

Reynolds number
RE NAOA

  • RE: real: Reynolds number for this block \(\mathrm {[1]}\)

  • NAOA: integer: number of angle-of-attack points for this data block

Dynamic stall initialization parameters

To be given only if DSIN=1

AOA0 DCLDA1 DCLDA2 AOAFS1 AOAFS2

  • AOA0: real: the angle of attack where there is zero lift, upcrossing \(\mathrm {[deg]}\)

  • DCLDA1: real: maximum slope of the lift curve in the linear region above AOA0 \(\mathrm {[1/deg]}\)

  • DCLDA2: real: maximum slope of the lift curve in the linear region below AOA0 \(\mathrm {[1/deg]}\)

  • AOAFS1: real: angle of attack corresponding to full separation above AOA0 \(\mathrm {[deg]}\)

  • AOAFS2: real: angle of attack corresponding to full separation below AOA0 \(\mathrm {[deg]}\)

The dynamic stall initialization parameters are shown in the figure `Illustration of dynamic stall initialization parameters' below.

dynstall param
Figure 1. Illustration of dynamic stall initialization parameters.
Aerodynamic coefficients

NAOA input lines

AOA CL CD CM

  • AOA: real: angle of attack \(\mathrm {[deg]}\)

  • CL: real: non-dimensional lift coefficient \(\mathrm {[1]}\)

  • CD: real: non-dimensional drag coefficient \(\mathrm {[1]}\)

  • CM: real: non-dimensional moment coefficient \(\mathrm {[1]}\)

1.5. Normalized airfoil geometry

NGEO input lines, to be given only if NGEO > 0.
Airfoil coordinates are normalized by the chord length, with the origin at the aerodynamic reference point. Points around the full airfoil should be given, i.e. several lines may have the same XGEO and different values for YGEO.

XGEO YGEO

  • XGEO: real: x coordinate of geometry point, normalized by chord length.

  • YGEO: real: y coordinate of geometry point, normalized by chord length.