Using the Aeroacoustics Model in AeroDyn

A live version of this documentation is available at https://openfast.readthedocs.io/. To run the aeroacoustics model, the flag CompAA needs to be set to True at line 14 of the AeroDyn15 main input file in the inputs block General Options. When the flag is set to True, the following line must include the name of the file containing the inputs to the aeroacoustics model, which is discussed in Section Currently, this module cannot be used with an MHK turbine.

 1------- AERODYN INPUT FILE -----------------------------------------------
 2IEA Wind Task 37 land-based reference wind turbine
 3====== General Options ===================================================
 4False          Echo        - Echo the input to "<rootname>.AD.ech"? (flag)
 5"default"      DTAero      - Time interval for aerodynamic calculations {or "default"} (s)
 61              WakeMod     - Type of wake/induction model (switch) {0=none, 1=BEMT}
 72              AFAeroMod   - Type of blade airfoil aerodynamics model (switch
 80              TwrPotent   - Type of tower influence on wind around the tower (switch)
 90              TwrShadow   - Type of tower influence on wind based on downstream tower shadow (switch) {0=none, 1=Powles model, 2=Eames model}
10False          TwrAero     - Calculate tower aerodynamic loads? (flag)
11False          FrozenWake  - Assume frozen wake during linearization? (flag
12False          CavitCheck  - Perform cavitation check? (flag)
13False          Buoyancy    - Include buoyancy effects? (flag)
14True           CompAA      - Flag to compute AeroAcoustics calculation
15"AeroAcousticsInput.dat"   AA_InputFile
16====== Environmental Conditions ==========================================
17"default"      AirDens     - Air density (kg/m^3)
19File continues... Main Input File

The aeroacoustics main input file comprises a series of inputs and flags that should be set appropriately depending on the analysis that should be run. These are split into the subfields General Options, Aeroacoustics Models, Observer Input, and Outputs.

Starting from the General Options, these are:

  • Echo – True/False: option to rewrite the input file with the correct template

  • DT_AA – Float: time step of the aeroacoustics computations. Only multiples of the time step DTAero of AeroDyn can be used. If set to default, the time step DTAero is adopted.

  • AAStart – Float: time after which the AeroAcoustics module is run.

  • BldPrcnt – Float: percentage value of blade span measured from blade tip that contributes to the noise emissions; 100% corresponds to the entire blade from tip to root.

The field Aeroacoustics Models lists all the flags for the actual noise models:

  • TIMod – Integer 0/1/2: flag to set the turbulent inflow noise model; 0 turns it off, 1 corresponds to the Amiet model discussed in Section, and 2 corresponds to the Simplified Guidati model presented in Section

  • TICalcMeth – Integer 1/2: flag to set the calculation method for the incident turbulence intensity. When set to 1, incident turbulence intensity is defined in a user-defined grid; see Section When set to 2, incident turbulence intensity is estimated from the time history of the incident flow.

  • TICalcTabFile – String: name of the text file with the user-defined turbulence intensity grid; see Section

  • Lturb – Float: value of \(L_{turb}\) used to estimate the turbulent lengthscale used in the Amiet model.

  • TBLTEMod – Integer 0/1/2: flag to set the TBL-TE noise model; 0 turns off the model, 1 uses the Brooks-Pope-Marcolini (BPM) airfoil noise model (see Section, and 2 uses the TNO model described in Section

  • BLMod – Integer 1/2: flag to set the calculation method for the boundary layer characteristics; 1 uses the simplified equations from the BPM model, 2 loads the files as described in Section Only used if TBLTEMod is different than zero.

  • TripMod – Integer 0/1/2: if BLMod is set to 1, different semiempirical parameters are used for a nontripped boundary layer (TRipMod=0), heavily tripped boundary layer (TRipMod=1), or lightly tripped boundary layer (TRipMod=2); 2 is typically used for operational wind turbines, whereas 1 is often used for wind tunnel airfoil models.

  • LamMod – Integer 0/1: flag to activate the laminar boundary layer – vortex shedding model, presented in Section

  • TipMod – Integer 0/1: flag to activate the tip vortex model, presented in Section

  • RoundedTip – True/False: if TipMod=1, this flag switches between a round tip (True) and a square tip (False), see Section

  • Alprat – Float: value of the slope of the lift coefficient curve at blade tip; see Section

  • BluntMod – Integer 0/1: flag to activate (BluntMod=1) the trailing-edge bluntness – vortex shedding model, see Section If the flag is set to 1, the trailing-edge geometry must be specified in the files as described in Section

The field Observer Locations contains the path to the file where the number of observers (NrObsLoc) and the respective locations are specified; see Section

Finally, the set Outputs contains a few options for the output data:

  • AWeighting – True/False: flag to set whether the sound pressure levels are reported with (True) or without (False) the A-weighting correction; see Section

  • NAAOutFile – Integer 1/2/3: flag to set the desired output file. When set to 1, a value of overall sound pressure level at every DT_AA time step per observer is printed to file. When set to 2, the first output is accompanied by a second file where the total sound pressure level spectrum is printed per time step per observer. When set to 3, the two first outputs are accompanied by a third file where the sound pressure level spectrum per noise mechanism is printed per time step per observer. When set to 4, a fourth file is generated with the values of overall sound pressure levels per node, per blade, per observer, and per time step.

  • The following line contains the file name used to store the outputs. The file name is attached with a 1, 2, 3, and 4 flag based on the NAAOutFile options.

The file must be closed by an END command.

 1------- AeroAcoustics Module INPUT FILE -------------------------------------------------------------
 2IEA task 37 RWT turbine -- https://github.com/IEAWindTask37/IEA-3.4-130-RWT
 3======  General Options  ============================================================================
 4False        Echo         - Echo the input to "<rootname>.AD.NN.ech"?  (flag)
 50.1          DT_AA        - Time interval for aeroacoustics calculations (s), must be a multiple of DT_Aero from AeroDyn15  (or "default")
 60            AAStart      - Time after which the AeroAcoustics module is run (s)
 770           BldPrcnt     - Percentage of the blade span, starting from the tip, that will contribute to the overall noise levels. (float)
 8======  Aeroacoustic Models  ============================================================================
 92            TIMod        - Turbulent Inflow noise model  {0: none, 1: Amiet 2: Amiet + Simplified Guidati} (switch) 
101            TICalcMeth   - Method to estimate turbulence intensity incident to the profile {1: given table, 2: computed on the fly} (switch) [Only used if TIMod!=0]
11"TIGrid_InVerify.txt"   TICalcTabFile - Name of the file containing the table for incident turbulence intensity (-) [Only used if TiCalcMeth == 1]
120.5          SurfRoughness- Surface roughness value used to estimate the turbulent length scale in Amiet model (m)
131            TBLTEMod     - Turbulent Boundary Layer-Trailing Edge noise calculation {0: none, 1:BPM, 2: TNO} (switch)
141            BLMod        - Calculation method for boundary layer properties,  {1: BPM, 2: Pretabulated} (switch)
151            TripMod      - Boundary layer trip model {0:no trip, 1: heavy trip, 2: light trip} (switch) [Only used if BLMod=1]
160            LamMod       - Laminar boundary layer noise model {0:none, 1: BPM}  (switch)
170            TipMod       - Tip vortex noise model {0:none, 1: BPM}  (switch)
18True         RoundedTip   - Logical indicating rounded tip (flag) [Only used if TipMod=1]
191.0          Alprat       - Tip lift curve slope (Default = 1.0) [Only used if TipMod=1]
200            BluntMod     - Trailing-edge-bluntness – Vortex-shedding model {0:none, 1: BPM}  (switch)
21"AABlade1.dat"    AABlFile(1)   - Name of file containing distributed aerodynamic properties for Blade #1 (-)
22"AABlade1.dat"    AABlFile(2)   - Name of file containing distributed aerodynamic properties for Blade #2 (-)
23"AABlade1.dat"    AABlFile(3)   - Name of file containing distributed aerodynamic properties for Blade #3 (-)
24======  Observer Input  ===================================================================
25"AA_ObserverLocations.dat"    ObserverLocations        - Name of file containing all observer locations X Y Z (-)
26======  Outputs  ====================================================================================
27False              AWeighting  - A-weighting Flag (flag)  
283                 NrOutFile  - Number of Output files. 1 for Time Dependent Overall SPL, 2 for both 1 and Frequency and Time Dependent SPL as well, or 3 for both 1 and 2 and Acoustics mechanism dependent, 4 for 1-3 and the overall sound pressure levels per blade per node per observer 
29"IEA_LB_RWT-AeroAcoustics_"    AAOutFile   - No Extension needed the resulting file will have .out Name of file containing
30END of input file (the word "END" must appear in the first 3 columns of this last OutList line)
31--------------------------------------------------------------------------------------- Boundary Layer Inputs and Trailing Edge Geometry

When the flag BLMod is set equal to 2, pretabulated properties of the boundary layer must be provided and are used by the turbulent boundary layer – trailing-edge noise models. The file name is to be specified in the field BL_file among the inputs of the file with the airfoil polar coefficients. One airfoil file must be specified per aerodynamic station.

 1! ------------ AirfoilInfo Input File ------------------------------------------
 2! AeroElasticSE FAST driver
 5! ------------------------------------------------------------------------------
 6DEFAULT                  InterpOrd   ! Interpolation order to use for quasi-steady table lookup {1=linear; 3=cubic spline; "default"} [default=1]
 71                        NonDimArea  ! The non-dimensional area of the airfoil (area/chord^2) (set to 1.0 if unsure or unneeded)
 8@"AF20_Coords.txt"       NumCoords   ! The number of coordinates in the airfoil shape file. Set to zero if coordinates not included.
 9AF20_BL.txt              BL_file     ! The file name including the boundary layer characteristics of the profile. Optional and ignored if the aeroacoustic module is not called.
101                        NumTabs     ! Number of airfoil tables in this file.  Each table must have lines for Re and Ctrl.
11! ------------------------------------------------------------------------------
12! data for table 1

The file, in this example named AF20_BL.txt, contains 8 inputs, which are tabulated for a given number of Reynolds numbers, ReListBL, and a given number of angles of attack, aoaListBL. The inputs, which are defined nondimensionally and must be provided for the suction and pressure side of the airfoil above and below the trailing edge, are:

  • Ue_Vinf – flow velocity at the top of the boundary layer

  • Dstar\(\delta^{*}\), boundary layer displacement thickness

  • Delta\(\delta\), nominal boundary layer thickness

  • Cf – friction coefficient.

In the following example, the file was generated thanks to a Python script 4 that runs the boundary layer solver, XFoil. Notably, XFoil, by default, does not return \(\delta\), but the boundary layer momentum thickness, \(\theta\). \(\delta\) can be reconstructed using the expression from [aa-DG87]:

(4.66)\[\delta = \theta \bullet \left( 3.15 + \frac{1.72}{H - 1} \right) + \delta^{*}\]

where \(H\) is the kinematic shape factor, which is also among the standard outputs of XFoil. Because it is usually impossible to obtain these values for the whole ranges of Reynolds numbers and angles of attack, the code is set to adopt the last available values and print to screen a warning.

When the flag BluntMod is set to 1, the detailed geometry of the trailing edge must also be defined along the span. Two inputs must be provided, namely the angle, \(\Psi\) between the suction and pressure sides of the profile, right before the trailing-edge point, and the height, \(h\), of the trailing edge. \(\Psi\) must be defined in degrees, while \(h\) is in meters. Note that the BPM trailing-edge bluntness model is very sensitive to these two parameters, which, however, are often not easy to determine for real blades. Fig. 4.25 shows the two inputs.

Geometric parameters of the trailing-edge bluntness

Fig. 4.25 Geometric parameters \(\mathbf{\Psi}\) and \(\mathbf{h}\) of the trailing-edge bluntness

One value of \(\Psi\) and one value of \(h\) per file must be defined. These values are not used if the flag BluntMod is set to 0.

  1! Boundary layer characteristics at the trailing edge for the airfoil coordinates of /Users/pbortolo/work/2_openfast/noise/verifyAA/OpenFAST_IEA_LB_RWT/Airfoils/AF20_Coords.txt
  2! Legend: aoa - angle of attack (deg), Re - Reynolds number (-, millions), PS - pressure side, SS - suction side,  Ue_Vinf - edge velocity (-), Dstar - displacement thickness (-), Delta - nominal boundary layer thickness (-) Cf  - friction coefficient (-)
  34           ReListBL   -  Number of Reynolds numbers (it corresponds to the number of tables)
  430          aoaListBL  -  Number of angles of attack (it corresponds to the number of rows in each table)
  50.50        -  Re
  6aoa             Ue_Vinf_SS          Ue_Vinf_PS         Dstar_SS           Dstar_PS           Delta_SS           Delta_PS           Cf_SS              Cf_PS
  7(deg)           (-)                 (-)                (-)                (-)                (-)                (-)                (-)                (-)
  8-5.00000        8.39390e-01        -8.37360e-01        7.43700e-03        1.07730e-02        2.75094e-02        5.15849e-02        1.13200e-03        1.58200e-03 
  9-3.96552        8.42050e-01        -8.40230e-01        8.26600e-03        9.29500e-03        2.98650e-02        4.87153e-02        1.04400e-03        1.85700e-03 
 10-2.93103        8.45320e-01        -8.43690e-01        9.08800e-03        8.10000e-03        3.19790e-02        4.70045e-02        9.58000e-04        2.16500e-03 
 11-1.89655        8.48230e-01        -8.46710e-01        9.97400e-03        7.33700e-03        3.44024e-02        4.50456e-02        8.90000e-04        2.35800e-03 
 12-0.86207        8.51550e-01        -8.50140e-01        1.09130e-02        6.54100e-03        3.68822e-02        4.30884e-02        8.26000e-04        2.59900e-03 
 13 0.17241        8.55000e-01        -8.53670e-01        1.18900e-02        5.92900e-03        3.96199e-02        4.27416e-02        7.79000e-04        2.87100e-03 
 14 1.20690        8.63820e-01        -1.04207e+00        1.22130e-02        9.89500e-03        4.18890e-02        1.68156e-02        8.18000e-04       -1.77000e-04 
 15 2.24138        8.61500e-01        -8.60210e-01        1.40420e-02        4.88700e-03        4.51813e-02        3.93105e-02        6.78000e-04        3.28700e-03 
 16 3.27586        8.64430e-01        -8.63080e-01        1.52900e-02        4.57300e-03        4.85938e-02        3.82233e-02        6.39000e-04        3.44000e-03 
 17 4.31034        8.67960e-01        -8.66600e-01        1.65660e-02        4.09100e-03        5.17768e-02        3.63749e-02        5.96000e-04        3.69000e-03 
 18 5.34483        8.72300e-01        -8.70850e-01        1.81000e-02        3.81700e-03        5.43379e-02        3.52278e-02        5.09000e-04        3.86300e-03 
 19 6.37931        8.77930e-01        -8.76410e-01        1.98500e-02        3.39700e-03        5.69109e-02        3.31481e-02        4.18000e-04        4.13900e-03 
 20 7.41379        8.86840e-01        -8.85140e-01        2.22250e-02        3.15000e-03        5.81316e-02        3.19040e-02        2.64000e-04        4.36900e-03 
 21 8.44828        9.00620e-01        -8.98660e-01        2.54290e-02        2.75900e-03        5.91946e-02        2.95298e-02        1.01000e-04        4.76300e-03 
 22 9.48276        9.20300e-01        -9.17700e-01        2.99830e-02        2.48300e-03        6.07767e-02        2.75551e-02        5.00000e-06        5.16000e-03 
 2310.51724        9.48080e-01        -9.44440e-01        3.80160e-02        2.13200e-03        6.65531e-02        2.48447e-02       -1.60000e-05        5.76800e-03 
 2411.55172        9.89560e-01        -9.84930e-01        5.83630e-02        1.85700e-03        8.76076e-02        2.18890e-02       -1.50000e-05        6.49000e-03 
 2512.58621        1.02883e+00        -1.02353e+00        8.80990e-02        1.66700e-03        1.21588e-01        2.00072e-02       -1.30000e-05        7.20200e-03 
 2613.62069        1.05789e+00        -1.05226e+00        1.18914e-01        1.51000e-03        1.57264e-01        1.78004e-02       -1.10000e-05        7.74800e-03 
 2714.65517        1.07975e+00        -1.07394e+00        1.48726e-01        1.41900e-03        1.91423e-01        1.65710e-02       -1.00000e-05        8.15600e-03 
 2815.68966        1.09657e+00        -1.09067e+00        1.76430e-01        1.34400e-03        2.22657e-01        1.56180e-02       -9.00000e-06        8.50600e-03 
 2916.72414        1.11040e+00        -1.10441e+00        2.02883e-01        1.26100e-03        2.52158e-01        1.43276e-02       -9.00000e-06        8.80900e-03 
 3017.75862        1.12290e+00        -1.11682e+00        2.29606e-01        1.20600e-03        2.81695e-01        1.35432e-02       -8.00000e-06        9.07600e-03 
 3118.79310        1.13461e+00        -1.12844e+00        2.55478e-01        1.15500e-03        3.10143e-01        1.28744e-02       -8.00000e-06        9.34700e-03 
 3219.82759        1.14605e+00        -1.13974e+00        2.80923e-01        1.08200e-03        3.37970e-01        1.16844e-02       -8.00000e-06        9.61200e-03 
 3320.86207        1.15722e+00        -1.15073e+00        3.05117e-01        1.03800e-03        3.64240e-01        1.10866e-02       -7.00000e-06        9.87000e-03 
 3421.89655        1.16808e+00        -1.16138e+00        3.27770e-01        9.81000e-04        3.88826e-01        1.02373e-02       -7.00000e-06        1.01370e-02 
 3522.93103        1.17845e+00        -1.17148e+00        3.48909e-01        9.33000e-04        4.11299e-01        9.52780e-03       -7.00000e-06        1.03870e-02 
 3623.96552        1.18930e+00        -1.18205e+00        3.70277e-01        8.93000e-04        4.34300e-01        9.01762e-03       -7.00000e-06        1.06550e-02 
 3725.00000        1.19987e+00        -1.19227e+00        3.90503e-01        8.36000e-04        4.55921e-01        8.12755e-03       -7.00000e-06        1.09080e-02 
 381.00        -  Re
 39aoa             Ue_Vinf_SS          Ue_Vinf_PS         Dstar_SS           Dstar_PS           Delta_SS           Delta_PS           Cf_SS              Cf_PS
 40(deg)           (-)                 (-)                (-)                (-)                (-)                (-)                (-)                (-)
 41-5.00000        8.34300e-01        -8.32480e-01        6.49600e-03        7.74600e-03        2.28566e-02        3.97467e-02        8.39000e-04        1.54900e-03 
 42-3.96552        8.37330e-01        -8.35790e-01        7.10100e-03        6.55800e-03        2.45059e-02        3.67266e-02        7.84000e-04        1.80000e-03 
 43-2.93103        8.40670e-01        -8.39370e-01        7.75600e-03        5.65600e-03        2.62162e-02        3.42658e-02        7.27000e-04        2.03700e-03 
 44-1.89655        8.44170e-01        -8.43070e-01        8.45300e-03        4.96000e-03        2.79616e-02        3.22259e-02        6.72000e-04        2.25700e-03 
 45-0.86207        8.47840e-01        -8.46890e-01        9.21600e-03        4.45100e-03        2.98142e-02        3.07238e-02        6.18000e-04        2.45400e-03 
 46 0.17241        8.51730e-01        -8.50900e-01        1.00790e-02        3.95100e-03        3.18738e-02        2.89503e-02        5.65000e-04        2.66300e-03 
 47 1.20690        8.55470e-01        -8.54730e-01        1.09340e-02        3.54400e-03        3.37289e-02        2.74209e-02        5.12000e-04        2.86100e-03 
 48 2.24138        8.59040e-01        -8.58320e-01        1.18130e-02        3.25200e-03        3.55603e-02        2.64490e-02        4.62000e-04        3.03800e-03 
 49 3.27586        8.63480e-01        -8.62770e-01        1.29500e-02        2.91700e-03        3.78947e-02        2.47691e-02        4.08000e-04        3.23200e-03 
 50 4.31034        8.67590e-01        -8.66830e-01        1.40320e-02        2.69800e-03        3.97441e-02        2.39342e-02        3.50000e-04        3.40400e-03 
 51 5.34483        8.72380e-01        -8.71540e-01        1.53110e-02        2.43000e-03        4.18407e-02        2.22446e-02        2.92000e-04        3.59200e-03 
 52 6.37931        8.78360e-01        -8.77360e-01        1.68420e-02        2.23600e-03        4.38267e-02        2.12352e-02        2.20000e-04        3.78300e-03 
 53 7.41379        8.86030e-01        -8.84810e-01        1.87390e-02        2.00100e-03        4.60113e-02        1.94428e-02        1.44000e-04        4.00100e-03 
 54 8.44828        8.96310e-01        -8.94850e-01        2.13480e-02        1.83100e-03        4.88127e-02        1.83696e-02        5.90000e-05        4.24200e-03 
 55 9.48276        9.25990e-01        -9.23230e-01        2.81520e-02        1.56900e-03        5.51012e-02        1.62260e-02       -1.00000e-06        4.73700e-03 
 5610.51724        9.66170e-01        -9.62320e-01        4.28900e-02        1.36700e-03        7.03103e-02        1.45187e-02       -9.00000e-06        5.34800e-03 
 5711.55172        1.00255e+00        -9.97860e-01        6.33540e-02        1.21700e-03        9.26255e-02        1.29836e-02       -7.00000e-06        5.90200e-03 
 5812.58621        1.03100e+00        -1.02578e+00        8.62500e-02        1.10600e-03        1.18923e-01        1.16999e-02       -6.00000e-06        6.34900e-03 
 5913.62069        1.05406e+00        -1.04857e+00        1.10634e-01        1.04100e-03        1.47132e-01        1.09721e-02       -6.00000e-06        6.70700e-03 
 6014.65517        1.07334e+00        -1.06769e+00        1.35720e-01        9.66000e-04        1.76016e-01        9.96935e-03       -5.00000e-06        7.01900e-03 
 6115.68966        1.08881e+00        -1.08308e+00        1.60129e-01        9.17000e-04        2.03832e-01        9.33244e-03       -5.00000e-06        7.27400e-03 
 6216.72414        1.10158e+00        -1.09579e+00        1.83765e-01        8.82000e-04        2.30423e-01        8.89329e-03       -5.00000e-06        7.49000e-03 
 6317.75862        1.11342e+00        -1.10758e+00        2.08205e-01        8.32000e-04        2.57695e-01        8.20477e-03       -4.00000e-06        7.69800e-03 
 6418.79310        1.12407e+00        -1.11817e+00        2.32504e-01        8.01000e-04        2.84583e-01        7.81234e-03       -4.00000e-06        7.88600e-03 
 6519.82759        1.13501e+00        -1.12904e+00        2.57953e-01        7.76000e-04        3.12682e-01        7.52201e-03       -4.00000e-06        8.07500e-03 
 6620.86207        1.14614e+00        -1.14008e+00        2.83630e-01        7.33000e-04        3.41005e-01        6.90325e-03       -4.00000e-06        8.27100e-03 
 6721.89655        1.15868e+00        -1.15248e+00        3.10888e-01        7.07000e-04        3.71055e-01        6.60979e-03       -4.00000e-06        8.48600e-03 
 6822.93103        1.17050e+00        -1.16410e+00        3.35623e-01        6.81000e-04        3.98279e-01        6.28286e-03       -3.00000e-06        8.69100e-03 
 6923.96552        1.18348e+00        -1.17683e+00        3.61314e-01        6.45000e-04        4.26528e-01        5.81057e-03       -3.00000e-06        8.91700e-03 
 7025.00000        1.19753e+00        -1.19058e+00        3.87323e-01        6.21000e-04        4.54991e-01        5.52432e-03       -3.00000e-06        9.15800e-03 
 715.00        -  Re
 72aoa             Ue_Vinf_SS          Ue_Vinf_PS         Dstar_SS           Dstar_PS           Delta_SS           Delta_PS           Cf_SS              Cf_PS
 73(deg)           (-)                 (-)                (-)                (-)                (-)                (-)                (-)                (-)
 74-5.00000        8.23420e-01        -8.21880e-01        4.67200e-03        4.76700e-03        1.77334e-02        2.96859e-02        6.92000e-04        1.41000e-03 
 75-3.96552        8.25550e-01        -8.24400e-01        5.04400e-03        4.14000e-03        1.88321e-02        2.75480e-02        6.57000e-04        1.55000e-03 
 76-2.93103        8.27930e-01        -8.27220e-01        5.46200e-03        3.53900e-03        2.00407e-02        2.52464e-02        6.21000e-04        1.70500e-03 
 77-1.89655        8.30490e-01        -8.30120e-01        5.91700e-03        3.10400e-03        2.13254e-02        2.34284e-02        5.86000e-04        1.84000e-03 
 78-0.86207        8.33100e-01        -8.33000e-01        6.40000e-03        2.77600e-03        2.26264e-02        2.19701e-02        5.50000e-04        1.95800e-03 
 79 0.17241        8.35520e-01        -8.35690e-01        6.86100e-03        2.45300e-03        2.37731e-02        2.03359e-02        5.15000e-04        2.08300e-03 
 80 1.20690        8.38270e-01        -8.38660e-01        7.40600e-03        2.17500e-03        2.51176e-02        1.87906e-02        4.79000e-04        2.20700e-03 
 81 2.24138        8.41350e-01        -8.41880e-01        8.04900e-03        1.95800e-03        2.66635e-02        1.75032e-02        4.40000e-04        2.31900e-03 
 82 3.27586        8.43950e-01        -8.44520e-01        8.65200e-03        1.80300e-03        2.79650e-02        1.65339e-02        4.03000e-04        2.40900e-03 
 83 4.31034        8.48180e-01        -8.48810e-01        9.58300e-03        1.61000e-03        3.00737e-02        1.51804e-02        3.59000e-04        2.53200e-03 
 84 5.34483        8.53570e-01        -8.54090e-01        1.08300e-02        1.48600e-03        3.27612e-02        1.43249e-02        3.08000e-04        2.63700e-03 
 85 6.37931        8.72880e-01        -8.73060e-01        1.51570e-02        1.28200e-03        4.16833e-02        1.28096e-02        1.92000e-04        2.88700e-03 
 86 7.41379        8.92130e-01        -8.91760e-01        1.98220e-02        1.14700e-03        4.87740e-02        1.17767e-02        8.30000e-05        3.11600e-03 
 87 8.44828        9.17360e-01        -9.16020e-01        2.50640e-02        9.92000e-04        5.31945e-02        1.04181e-02        2.00000e-06        3.41900e-03 
 88 9.48276        9.42910e-01        -9.40410e-01        3.17040e-02        8.85000e-04        5.85499e-02        9.42477e-03       -1.00000e-06        3.70700e-03 
 8910.51724        9.64800e-01        -9.61630e-01        4.02300e-02        7.96000e-04        6.64893e-02        8.47323e-03       -2.00000e-06        3.96100e-03 
 9011.55172        9.86420e-01        -9.82570e-01        5.11880e-02        7.23000e-04        7.76623e-02        7.65452e-03       -2.00000e-06        4.20700e-03 
 9112.58621        1.00657e+00        -1.00210e+00        6.43270e-02        6.71000e-04        9.20001e-02        7.06023e-03       -2.00000e-06        4.43100e-03 
 9213.62069        1.02475e+00        -1.01984e+00        7.93340e-02        6.16000e-04        1.09051e-01        6.35528e-03       -1.00000e-06        4.64000e-03 
 9314.65517        1.04370e+00        -1.03850e+00        9.84840e-02        5.79000e-04        1.31195e-01        5.91001e-03       -1.00000e-06        4.84500e-03 
 9415.68966        1.06004e+00        -1.05467e+00        1.18503e-01        5.43000e-04        1.54410e-01        5.44594e-03       -1.00000e-06        5.02500e-03 
 9516.72414        1.07448e+00        -1.06905e+00        1.39604e-01        5.14000e-04        1.78759e-01        5.05912e-03       -1.00000e-06        5.18500e-03 
 9617.75862        1.08720e+00        -1.08175e+00        1.61656e-01        4.93000e-04        2.03997e-01        4.79726e-03       -1.00000e-06        5.32500e-03 
 9718.79310        1.09867e+00        -1.09324e+00        1.84226e-01        4.68000e-04        2.29525e-01        4.45243e-03       -1.00000e-06        5.45500e-03 
 9819.82759        1.10970e+00        -1.10430e+00        2.08500e-01        4.51000e-04        2.56774e-01        4.24858e-03       -1.00000e-06        5.57800e-03 
 9920.86207        1.11936e+00        -1.11397e+00        2.32097e-01        4.34000e-04        2.83065e-01        4.03443e-03       -1.00000e-06        5.69000e-03 
10021.89655        1.12815e+00        -1.12274e+00        2.54679e-01        4.14000e-04        3.07965e-01        3.77358e-03       -1.00000e-06        5.79400e-03 
10122.93103        1.13774e+00        -1.13227e+00        2.78750e-01        4.00000e-04        3.34530e-01        3.60784e-03       -1.00000e-06        5.90600e-03 
10223.96552        1.14721e+00        -1.14164e+00        3.02299e-01        3.84000e-04        3.60352e-01        3.41109e-03       -1.00000e-06        6.01800e-03 
10325.00000        1.15816e+00        -1.15244e+00        3.27151e-01        3.68000e-04        3.87710e-01        3.21949e-03       -1.00000e-06        6.14600e-03 
10410.00       -  Re
105aoa             Ue_Vinf_SS          Ue_Vinf_PS         Dstar_SS           Dstar_PS           Delta_SS           Delta_PS           Cf_SS              Cf_PS
106(deg)           (-)                 (-)                (-)                (-)                (-)                (-)                (-)                (-)
107-5.00000        8.19760e-01        -8.18060e-01        4.17800e-03        4.54900e-03        1.65706e-02        2.88150e-02        6.56000e-04        1.23100e-03 
108-3.96552        8.21540e-01        -8.20450e-01        4.52500e-03        3.74000e-03        1.76308e-02        2.59028e-02        6.23000e-04        1.39100e-03 
109-2.93103        8.23580e-01        -8.22970e-01        4.89400e-03        3.21700e-03        1.87333e-02        2.38284e-02        5.91000e-04        1.51700e-03 
110-1.89655        8.25560e-01        -8.25320e-01        5.25400e-03        2.85300e-03        1.97567e-02        2.22669e-02        5.60000e-04        1.62100e-03 
111-0.86207        8.27870e-01        -8.28060e-01        5.67900e-03        2.46600e-03        2.09522e-02        2.03860e-02        5.28000e-04        1.74400e-03 
112 0.17241        8.30330e-01        -8.30840e-01        6.14400e-03        2.18100e-03        2.22219e-02        1.88758e-02        4.96000e-04        1.84900e-03 
113 1.20690        8.32880e-01        -8.33650e-01        6.64800e-03        1.94100e-03        2.35312e-02        1.74735e-02        4.63000e-04        1.94900e-03 
114 2.24138        8.35130e-01        -8.36090e-01        7.13000e-03        1.75100e-03        2.46910e-02        1.62700e-02        4.31000e-04        2.03800e-03 
115 3.27586        8.39970e-01        -8.41060e-01        8.09900e-03        1.56800e-03        2.72181e-02        1.50508e-02        3.88000e-04        2.14300e-03 
116 4.31034        8.50470e-01        -8.51560e-01        1.01990e-02        1.37300e-03        3.25448e-02        1.36378e-02        3.18000e-04        2.29400e-03 
117 5.34483        8.64450e-01        -8.65280e-01        1.32660e-02        1.23700e-03        3.92329e-02        1.26866e-02        2.31000e-04        2.45100e-03 
118 6.37931        8.78610e-01        -8.79110e-01        1.65810e-02        1.08900e-03        4.49765e-02        1.14397e-02        1.47000e-04        2.62200e-03 
119 7.41379        8.91030e-01        -8.91080e-01        1.96290e-02        9.93000e-04        4.89936e-02        1.06282e-02        7.60000e-05        2.76500e-03 
120 8.44828        9.08900e-01        -9.08620e-01        2.35230e-02        8.71000e-04        5.22284e-02        9.45732e-03        2.00000e-06        2.96800e-03 
121 9.48276        9.32700e-01        -9.30700e-01        2.84210e-02        7.79000e-04        5.52443e-02        8.61055e-03       -0.00000e+00        3.20000e-03 
12210.51724        9.51380e-01        -9.48770e-01        3.46600e-02        6.96000e-04        6.05165e-02        7.64709e-03       -1.00000e-06        3.39700e-03 
12311.55172        9.71740e-01        -9.68450e-01        4.35850e-02        6.37000e-04        6.90670e-02        6.98615e-03       -1.00000e-06        3.59500e-03 
12412.58621        9.91260e-01        -9.87290e-01        5.44080e-02        5.84000e-04        8.03205e-02        6.33577e-03       -1.00000e-06        3.78700e-03 
12513.62069        1.00996e+00        -1.00542e+00        6.74960e-02        5.36000e-04        9.47613e-02        5.73102e-03       -1.00000e-06        3.97000e-03 
12614.65517        1.02771e+00        -1.02275e+00        8.31660e-02        5.06000e-04        1.12645e-01        5.35979e-03       -1.00000e-06        4.13700e-03 
12715.68966        1.04427e+00        -1.03905e+00        1.00836e-01        4.71000e-04        1.33082e-01        4.88548e-03       -1.00000e-06        4.29600e-03 
12816.72414        1.06019e+00        -1.05485e+00        1.21136e-01        4.45000e-04        1.56673e-01        4.55077e-03       -1.00000e-06        4.44600e-03 
12917.75862        1.07407e+00        -1.06868e+00        1.42220e-01        4.22000e-04        1.81035e-01        4.24533e-03       -1.00000e-06        4.57900e-03 
13018.79310        1.08623e+00        -1.08087e+00        1.64037e-01        4.01000e-04        2.06006e-01        3.94306e-03       -0.00000e+00        4.69600e-03 
13119.82759        1.09748e+00        -1.09215e+00        1.87080e-01        3.86000e-04        2.32142e-01        3.76503e-03       -0.00000e+00        4.80500e-03 
13220.86207        1.10794e+00        -1.10267e+00        2.10804e-01        3.67000e-04        2.58816e-01        3.50553e-03       -0.00000e+00        4.90800e-03 
13321.89655        1.11776e+00        -1.11253e+00        2.35256e-01        3.54000e-04        2.86067e-01        3.34709e-03       -0.00000e+00        5.00500e-03 
13422.93103        1.12664e+00        -1.12138e+00        2.58366e-01        3.43000e-04        3.11568e-01        3.20986e-03       -0.00000e+00        5.09600e-03 
13523.96552        1.13635e+00        -1.13106e+00        2.83067e-01        3.28000e-04        3.38816e-01        3.02058e-03       -0.00000e+00        5.19400e-03 
13625.00000        1.14573e+00        -1.14034e+00        3.06604e-01        3.16000e-04        3.64612e-01        2.86692e-03       -0.00000e+00        5.29100e-03 Observer Positions

The number and position of observers is set in the file ObserverLocations, which is explained in Section The positions must be specified in the OpenFAST global inertial frame coordinate system, which is located at the tower base and has the x-axis pointing downwind, the y-axis pointing laterally, and the z-axis pointing vertically upward. A scheme of the coordinate system for the observers is shown in Fig. 4.26.

Reference system for the observers

Fig. 4.26 Reference system for the observers

The International Energy Agency Wind Task 37 land-based reference wind turbine, which is shown in Table 4.2, has a hub height of 110 meters and a rotor radius of 65 meters, and has the International Electrotechnical Commission 61400-11 standards compliant observer located at:

x = 175 [m]

y = 0 [m]

z = 0 [m].

An example of a file listing four observers located at a 2-meter height is shown here:

14 NrObsLoc - Total Number of observer locations
2X Observer location in tower-base coordinate X horizontal (m), Y Observer location in tower-base coordinate Y Lateral (m), Z Observer location in tower-base coordinate Z Vertical (m)
3-200  -200  2
4-200  +200  2
5+200  -200  2
6+200  +200  2 Turbulence Grid

When the flag TICalcMeth is set equal to 1, the grid of turbulence intensity of the wind \(TI\) must be defined by the user. This is done by creating a file called TIGrid_In.txt, which mimics a TurbSim output file and contains a grid of turbulence intensity, which is defined as a fraction value. The file defines a grid centered at hub height and oriented with the OpenFAST global inertial frame coordinate system; see Fig. 4.26. A user-defined number of lateral and vertical points equally spaced by a user-defined number of meters must be specified. Note that an average wind speed must be defined to convert the turbulence intensity of the wind to the incident turbulent intensity \(I_{1}\). An example file for a 160 (lateral) by 180 (vertical) meters grid looks like the following:

 1Average Inflow Wind Speed
 3Total Grid points In Y (lateral), Starts from - radius goes to + radius+
 5Total Grid points In Z (vertical), Starts from bottom tip (hub-radius)
 7Grid spacing In Y (lateral)
 9Grid spacing In Z (vertical)
110.1200 0.1200 0.1200 0.1200
120.1100 0.1100 0.1100 0.1100
130.1000 0.1000 0.1000 0.1000