Some CRAFTS data files use the .mat (MATLAB binary file) format. For users without access to MATLAB to produce or format these files, the CSV to MAT conversion function within the Data Generation Tool offers an alternative. Prepare a .csv file with data matching the format of the desired data file, specified below, and convert it to an equivalent .mat file for use in CRAFTS.
Airfoil Polar Data
Description
The airfoil data file defines the polar characteristics for a given airfoil model. The coefficients of lift and drag are provided vs the angle of attack, forming a lookup table. After generating airfoil data files, a manifest .txt file must also be created to populate the airfoils in the blade model (see Notes for additional information).
Parameters
| Name | Description | Value | Unit |
|---|---|---|---|
AoA |
Angle of attack, defined as an array of N elements ascending from -180 to 180 degrees. | Real Nx1 array | [degrees] |
Cl |
Coefficient of lift, with each element corresponding to the respective element of the AoA array. | Real Nx1 array | [-] |
Cd |
Cofficient of drag, with each element corresponding to the respective element of the AoA array. | Real Nx1 array | [-] |
Notes
MAT files should contain three arrays of type double with names exactly matching the parameter names above. To properly fill the lookup table, AoA must contain at least 2 elements that range from -180 to 180 degrees.
To convert a CSV file to MAT, the first row must contain the array names (AoA, Cl, Cd). The subsequent rows of each column should contain the elements of the respective array, in the format described above.
After all desired airfoil data files have been generated, a manifest file must be created to coordinate the airfoil selections for a given blade model. The manifest file is a .txt file that assigns an airfoil data file to each aerodynamic element in the blade model. See the following example for the required format:
// Airfoils across aerodynamic elements for IEA 15MW reference wind turbine
airfoil1 = "modelica://CRAFTS/Resources/Data/Rotor/IEA 15MW/AirfoilPolars/IEA15MW_Polar_1.mat";
airfoil2 = "modelica://CRAFTS/Resources/Data/Rotor/IEA 15MW/AirfoilPolars/IEA15MW_Polar_2.mat";
airfoil3 = "modelica://CRAFTS/Resources/Data/Rotor/IEA 15MW/AirfoilPolars/IEA15MW_Polar_3.mat";
...
airfoilN = "modelica://CRAFTS/Resources/Data/Rotor/IEA 15MW/AirfoilPolars/IEA15MW_Polar_N.mat";
Each line begins with airfoilx, where x ranges from 1 to the number of aerodynamic elements in the model (N). Then, use = "path/to/file.mat" to specify the data file path. In addition to absolute file paths, relative file paths are supported by using the modelica:// URI scheme. With this structure, each aerodynamic element can be assigned a unique airfoil or an airfoil data file can be shared across multiple aerodynamic elements by pointing to the same file.
Once the manifest file has been completed, it can be selected in the CRAFTS blade model to initialize the model with the desired airfoils.
The MATLAB import preview window shows arrays AoA, Cd, and Cl. Since the arrays are of size 200, AoA is specified at 200 angles between -180° and 180°.
Blade Structure Data
Description
The blade structure data file defines geometric properties of the blade structure across the aerodynamic elements. For each aerodynamic element, a spanwise distance from the root, chord length, and blade twist are specified.
Parameters
| Name | Description | Value | Unit |
|---|---|---|---|
BldSpan |
Spanwise distances of N aerodynamic elements. | Real Nx1 array | [m] |
BldTwist |
Local aerodynamic twist angles at the radial stations corresponding to N aerodynamic elements. | Real Nx1 array | [degrees] |
ChordLen |
Chord lengths at the radial stations corresponding to N aerodynamic elements. | Real Nx1 array | [m] |
Notes
MAT files should contain three arrays of type double with names exactly matching the parameter names above. For a blade model containing N aerodynamic elements, the arrays must also be of size N.
To convert a CSV file to MAT, the first row must contain the array names (BldSpan, BldTwist, ChordLen). The subsequent rows of each column should contain the elements of the respective array, in the format described above.
The MATLAB import preview window shows arrays BldSpan, BldTwist, and ChordLen. Since the arrays are of size 50, the CRAFTS model has been configured with 50 aerodynamic elements across the span of the blade.
