This document details how the NREL 5-MW reference wind turbine is implemented in Ashes.
1.1 Blade shape
The data in the Blade shape file in Ashes is taken from the AeroDyn file available on GitHub (https://github.com/OpenFAST/r-test/blob/84616202adc19515e08b5c78f92448aa848e5f12/glue-codes/openfast/5MW_Baseline/NRELOffshrBsline5MW_AeroDyn_blade.dat, accessed January 2023).
There is an almost one-to-one correspondance between the Ashes file and the AeroDyn file, summarised in the table below:
|Column name in Ashes||Column name in AeroDyn||Comment|
|PrebendInPlane||BlSwpAC||The value in Ashes is the opposite of that in AeroDyn|
|Airfoil nickname||BlAFID||The nicknames for the airoils have to match the airfoil list|
1.2 Blade structure
the data in the Blade structure file in Ashes is taken from the BeamDyn file available on GitHub (https://github.com/OpenFAST/r-test/blob/84616202adc19515e08b5c78f92448aa848e5f12/glue-codes/openfast/5MW_Baseline/NRELOffshrBsline5MW_BeamDyn_Blade.dat, accessed January 2023)
The data in the BeamDyn input file is in matrix form, while the data in Ashes in presented as columns. The BeamDyn matrix definition can be found in the BeamDyn manual accessible here: https://openfast.readthedocs.io/en/main/source/user/beamdyn/input_files.html#blade-input-file (matrices 4.62 and 4.63, accessed January 2023). Each structural cross section is defined by two matrices: a stiffness matrix and a generalised sectional mass matrix.
The correspondance between Ashes and BeamDyn is summarised in the table below:
|Column name in Ashes||Parameter in BeamDyn||Parameter name|
|BMassDen||m||mass density per unit span|
|FlpInerDistr||iFlp||Flap mass moment of inertia|
|EdgInerDistr||iEdg||Edge mass moment of inertia|
In BeamDyn, the position along the balde for which the matrices are provided is given just before each pair of matrix. That parameter is equivalent to the BladeFraction column in Ashes.
Note that the BeamDyn file does not provide the structural twist of the blade. When defining the blade in Ashes, we have assumed that the structural twist is equivalent to the aerodynamical twist, interpolated from the AeroDyn file.