Warning: Turning off Unsteady Aerodynamics because polar has constant data.

[Laurens09]

Dear all,

I have run a simulation with OLAF module and dynamic polars (AFAeroMod = 2 and UAMod = 4). The output give me 3 warnings:

Warning: Turning off Unsteady Aerodynamics because polar has constant data. (node 1, blade 1)
Warning: Turning off Unsteady Aerodynamics because polar has constant data. (node 1, blade 2)
Warning: Turning off Unsteady Aerodynamics because polar has constant data. (node 1, blade 3)
Dvr_InitCase:ADI_Init:AD_Init:Init_BEMTmodule:BEMT_Init:UA_Init:UA_SetParameters:UA_ValidateAFI:Th
e separation function f_st does not reach 1 in
"D:\Documents\POLIMI\Tesi\Simulazioni\Modello-OC6.2\Modello-OC6.2.17\Modello-OC6.2.17.2.4\WTM_10MW
_350\./Airfoils_v3/_coarseMod/airfoilEL_5.dat". max(f_st)=0.44237. Check the calculation or
provide f_st in the input file.
UA_ValidateAFI:The separation function f_st does not reach 1 in
"D:\Documents\POLIMI\Tesi\Simulazioni\Modello-OC6.2\Modello-OC6.2.17\Modello-OC6.2.17.2.4\WTM_10MW
_350\./Airfoils_v3/_coarseMod/airfoilEL_5.dat". max(f_st)=0.45089. Check the calculation or
provide f_st in the input file.
UA_ValidateAFI:The separation function f_st does not reach 1 in
"D:\Documents\POLIMI\Tesi\Simulazioni\Modello-OC6.2\Modello-OC6.2.17\Modello-OC6.2.17.2.4\WTM_10MW
_350\./Airfoils_v3/_coarseMod/airfoilEL_5.dat". max(f_st)=0.69899. Check the calculation or
provide f_st in the input file.
UA_SetParameters:UA_ValidateAFI:Large value of C_lalpha in "D:\Documents\POLIMI\Tesi\

Could you explain me which are the possible reasons why Openfast give me this warning: Turning off Unsteady Aerodynamics because polar has constant data?

Why f_st parameter have to reach 1? How can I control its value?

Below you can see Aerodyn input file and OLAF.dat file

Thank you
Best regards

Matteo

AERODYN FILE

------- AERODYN v15.04.* INPUT FILE ------------------------------------------------
Polimi Wind Turbine Model
======  General Options  ============================================================================
False         Echo               - Echo the input to "<rootname>.AD.ech"?  (flag)
"default"     DTAero             - Time interval for aerodynamic calculations {or "default"} (s)
          3   WakeMod            - Type of wake/induction model (switch) {0=none, 1=BEMT}
          2   AFAeroMod          - Type of blade airfoil aerodynamics model (switch) {1=steady model, 2=Beddoes-Leishman unsteady model} [must be 1 when linearizing]
          0   TwrPotent          - Type tower influence on wind based on potential flow around the tower (switch) {0=none, 1=baseline potential flow, 2=potential flow with Bak correction}
          0   TwrShadow          - Calculate tower influence on wind based on downstream tower shadow (switch) {0=none, 1=Powles model, 2=Eames model}
False         TwrAero            - Calculate tower aerodynamic loads? (flag)
False         FrozenWake         - Assume frozen wake during linearization? (flag) [used only when WakeMod=1 and when linearizing]
False         CavitCheck         - Perform cavitation check? (flag)
False         Buoyancy           - Include buoyancy effects? (flag)
False         CompAA             - Flag to compute AeroAcoustics calculation [only used when WakeMod=1 or 2]
"unused"     AA_InputFile - Aeroacoustics input file
======  Environmental Conditions  ===================================================================
      1.225   AirDens            - Fluiddensity (kg/m^3)
    1.45e-5   KinVisc            - Kinematic viscosity (m^2/s)
        335   SpdSound           - Speed of sound (m/s)
     103500   Patm               - Atmospheric pressure (Pa) [used only when CavitCheck=True]
       1700   Pvap               - Vapour pressure of fluid (Pa) [used only when CavitCheck=True]
======  Blade-Element/Momentum Theory Options  ====================================================== [used only when WakeMod=1]
1             SkewMod            - Type of skewed-wake correction model (switch) {1=uncoupled, 2=Pitt/Peters, 3=coupled} [used only when WakeMod=1]
"default"     SkewModFactor      - Constant used in Pitt/Peters skewed wake model {or "default" is 15/32*pi} (-) [used only when SkewMod=2; unused when WakeMod=0]
False         TipLoss            - Use the Prandtl tip-loss model? (flag) [used only when WakeMod=1]
True          HubLoss            - Use the Prandtl hub-loss model? (flag) [used only when WakeMod=1]
True          TanInd             - Include tangential induction in BEMT calculations? (flag) [used only when WakeMod=1]
True          AIDrag             - Include the drag term in the axial-induction calculation? (flag) [used only when WakeMod=1]
True          TIDrag             - Include the drag term in the tangential-induction calculation? (flag) [used only when WakeMod=1 and TanInd=TRUE]
      5E-05   IndToler           - Convergence tolerance for BEMT nonlinear solve residual equation {or "default"} (-) [used only when WakeMod=1]
      10000   MaxIter            - Maximum number of iteration steps (-) [used only when WakeMod=1]
======  Dynamic Blade-Element/Momentum Theory Options  ====================================================== [used only when WakeMod=1]
2             DBEMT_Mod          - Type of dynamic BEMT (DBEMT) model {1=constant tau1, 2=time-dependent tau1} (-) [used only when WakeMod=2]
2             tau1_const         - Time constant for DBEMT (s) [used only when WakeMod=2 and DBEMT_Mod=1]
======  OLAF -- cOnvecting LAgrangian Filaments (Free Vortex Wake) Theory Options  ================== [used only when WakeMod=3]
"OLAF.dat"      OLAFInputFileName  - Input file for OLAF [used only when WakeMod=3]
======  Beddoes-Leishman Unsteady Airfoil Aerodynamics Options  ===================================== [used only when AFAeroMod=2]
4             UAMod       Unsteady Aero Model Switch (switch) {1=Baseline model (Original), 2=Gonzalez's variant (changes in Cn,Cc,Cm), 3=Minemma/Pierce variant (changes in Cc and Cm)} [used only when AFAeroMod=2]
True          FLookup     Flag to indicate whether a lookup for f' will be calculated (TRUE) or whether best-fit exponential equations will be used (FALSE); if FALSE S1-S4 must be provided in airfoil input files (flag) [used only when AFAeroMod=2]
0             UAStartRad  - Starting radius for dynamic stall (fraction of rotor radius) [used only when AFAeroMod=2]
1             UAEndRad    - Ending radius for dynamic stall (fraction of rotor radius) [used only when AFAeroMod=2]
======  Airfoil Information =========================================================================
          2   AFTabMod           - Interpolation method for multiple airfoil tables {1=1D interpolation on AoA (first table only); 2=2D interpolation on AoA and Re; 3=2D interpolation on AoA and UserProp} (-)
          1   InCol_Alfa         - The column in the airfoil tables that contains the angle of attack (-)
          2   InCol_Cl           - The column in the airfoil tables that contains the lift coefficient (-)
          3   InCol_Cd           - The column in the airfoil tables that contains the drag coefficient (-)
          4   InCol_Cm           - The column in the airfoil tables that contains the pitching-moment coefficient; use zero if there is no Cm column (-)
          0   InCol_Cpmin        - The column in the airfoil tables that contains the Cpmin coefficient; use zero if there is no Cpmin column (-)
          39  NumAFfiles         - Number of airfoil files used (-)
"Airfoils_v3/_coarseMod/airfoilEL_1.dat"
"Airfoils_v3/_coarseMod/airfoilEL_2.dat"
"Airfoils_v3/_coarseMod/airfoilEL_3.dat"
"Airfoils_v3/_coarseMod/airfoilEL_4.dat"
"Airfoils_v3/_coarseMod/airfoilEL_5.dat"
"Airfoils_v3/_coarseMod/airfoilEL_6.dat"
"Airfoils_v3/_coarseMod/airfoilEL_7.dat"
"Airfoils_v3/_coarseMod/airfoilEL_8.dat"
"Airfoils_v3/_coarseMod/airfoilEL_9.dat"
"Airfoils_v3/_coarseMod/airfoilEL_10.dat"
"Airfoils_v3/_coarseMod/airfoilEL_11.dat"
"Airfoils_v3/_coarseMod/airfoilEL_12.dat"
"Airfoils_v3/_coarseMod/airfoilEL_13.dat"
"Airfoils_v3/_coarseMod/airfoilEL_14.dat"
"Airfoils_v3/_coarseMod/airfoilEL_15.dat"
"Airfoils_v3/_coarseMod/airfoilEL_16.dat"
"Airfoils_v3/_coarseMod/airfoilEL_17.dat"
"Airfoils_v3/_coarseMod/airfoilEL_18.dat"
"Airfoils_v3/_coarseMod/airfoilEL_19.dat"
"Airfoils_v3/_coarseMod/airfoilEL_20.dat"
"Airfoils_v3/_coarseMod/airfoilEL_21.dat"
"Airfoils_v3/_coarseMod/airfoilEL_22.dat"
"Airfoils_v3/_coarseMod/airfoilEL_23.dat"
"Airfoils_v3/_coarseMod/airfoilEL_24.dat"
"Airfoils_v3/_coarseMod/airfoilEL_25.dat"
"Airfoils_v3/_coarseMod/airfoilEL_26.dat"
"Airfoils_v3/_coarseMod/airfoilEL_27.dat"
"Airfoils_v3/_coarseMod/airfoilEL_28.dat"
"Airfoils_v3/_coarseMod/airfoilEL_29.dat"
"Airfoils_v3/_coarseMod/airfoilEL_30.dat"
"Airfoils_v3/_coarseMod/airfoilEL_31.dat"
"Airfoils_v3/_coarseMod/airfoilEL_32.dat"
"Airfoils_v3/_coarseMod/airfoilEL_33.dat"
"Airfoils_v3/_coarseMod/airfoilEL_34.dat"
"Airfoils_v3/_coarseMod/airfoilEL_35.dat"
"Airfoils_v3/_coarseMod/airfoilEL_36.dat"
"Airfoils_v3/_coarseMod/airfoilEL_37.dat"
"Airfoils_v3/_coarseMod/airfoilEL_38.dat"
"Airfoils_v3/_coarseMod/airfoilEL_39.dat"
======  Rotor/Blade Properties  =====================================================================
False          UseBlCm            - Include aerodynamic pitching moment in calculations?  (flag)
"AERODYN_Blade.dat"                 ADBlFile(1)        - Name of file containing distributed aerodynamic properties for Blade #1 (-)
"AERODYN_Blade.dat"                 ADBlFile(2)        - Name of file containing distributed aerodynamic properties for Blade #2 (-) [unused if NumBl < 2]
"AERODYN_Blade.dat"                 ADBlFile(3)        - Name of file containing distributed aerodynamic properties for Blade #3 (-) [unused if NumBl < 3]
======  Hub Properties ============================================================================== [used only when Buoyancy=True]
0.0   VolHub             - Hub volume (m^3)
0.0   HubCenBx           - Hub center of buoyancy x direction offset (m)
======  Nacelle Properties ========================================================================== [used only when Buoyancy=True]
0.0   VolNac             - Nacelle volume (m^3)
0,0,0 NacCenB            - Position of nacelle center of buoyancy from yaw bearing in nacelle coordinates (m)
======  Tail fin Aerodynamics ======================================================================== 
False         TFinAero           - Calculate tail fin aerodynamics model (flag)
"unused"      TFinFile           - Input file for tail fin aerodynamics [used only when TFinAero=True]
======  Tower Influence and Aerodynamics ============================================================= [used only when TwrPotent/=0, TwrShadow=True, or TwrAero=True]
         1    NumTwrNds         - Number of tower nodes used in the analysis  (-) [used only when TwrPotent/=0, TwrShadow=True, or TwrAero=True]
TwrElev        TwrDiam        TwrCd          TwrTI			 TwrCb !TwrTI used only with TwrShadow=2, TwrCb used only with Buoyancy=True
(m)              (m)           (-)
1              1.0            1.0            0.1			 0.0
======  Outputs  ====================================================================================
False         SumPrint            - Generate a summary file listing input options and interpolated properties to "<rootname>.AD.sum"?  (flag)
          9   NBlOuts             - Number of blade node outputs [0 - 9] (-)
          1,2,3,4,5,6,7,8,9    BlOutNd             - Blade nodes whose values will be output  (-)
          0   NTwOuts             - Number of tower node outputs [0 - 9]  (-)
          1   TwOutNd             - Tower nodes whose values will be output  (-)
                   OutList             - The next line(s) contains a list of output parameters.  See OutListParameters.xlsx for a listing of available output channels, (-)

"RtAeroMxh, RtAeroFxh, RtFldCp"

END of input file (the word "END" must appear in the first 3 columns of this last OutList line)
---------------------------------------------------------------------------------------

OLAF.dat FILE

--------------------------- OLAF (cOnvecting LAgrangian Filaments) INPUT FILE -----------------
Free wake input file for the Helix test case
--------------------------- GENERAL OPTIONS ---------------------------------------------------
default IntMethod          - Integration method {1: RK4, 5: Forward Euler 1st order, default: 5} (switch) 
default DTfvw              - Time interval for wake propagation. {default: dtaero} (s)
default FreeWakeStart      - Time when wake is free. (-) value = always free. {default: 0.0} (s)
default FullCircStart      - Time at which full circulation is reached. {default: 0.0} (s)
--------------------------- CIRCULATION SPECIFICATIONS ----------------------------------------
default CircSolvMethod     - Circulation solving method {1: Cl-Based, 2: No-Flow Through, 3: Prescribed, default: 1 }(switch)
default CircSolvConvCrit   - Convergence criteria {default: 0.001} [only if CircSolvMethod=1] (-)
default CircSolvRelaxation - Relaxation factor {default: 0.1} [only if CircSolvMethod=1] (-)
default CircSolvMaxIter    - Maximum number of iterations for circulation solving {default: 30} (-)
"./Helix_PrescribedGamma.csv"  - PrescribedCircFile File containing prescribed circulation [only if CircSolvMethod=3] (quoted string)
===============================================================================================
--------------------------- WAKE OPTIONS ------------------------------------------------------
------------------- WAKE EXTENT AND DISCRETIZATION --------------------------------------------
480     nNWPanels          - Number of near-wake panels (-)
480     nNWPanelsFree      - Number of free near-wake panels (-) {default: nNWPanels}
1364    nFWPanels          - Number of far-wake panels (-) {default: 0}
800     nFWPanelsFree      - Number of free far-wake panels (-) {default: nFWPanels}
default FWShedVorticity    - Include shed vorticity in the far wake {default: False}
------------------- WAKE REGULARIZATIONS AND DIFFUSION -----------------------------------------
default DiffusionMethod    - Diffusion method to account for viscous effects {0: None, 1: Core Spreading, "default": 0}         
3       RegDeterMethod     - Method to determine the regularization parameters {0:  Manual, 1: Optimized, 2: Chord, 3: Span, default: 0 }          
default RegFunction        - Viscous diffusion function {0: None, 1: Rankine, 2: LambOseen, 3: Vatistas, 4: Denominator, "default": 3} (switch)
3       WakeRegMethod      - Wake regularization method {1: Constant, 2: Stretching, 3: Age, default: 3} (switch)
3       WakeRegFactor      - Wake regularization factor (m or -)
3       WingRegFactor      - Wing regularization factor (m or -)
700     CoreSpreadEddyVisc - Eddy viscosity in core spreading methods, typical values 1-1000 
------------------- WAKE TREATMENT OPTIONS ---------------------------------------------------
default TwrShadowOnWake    - Include tower flow disturbance effects on wake convection {default:false} [only if TwrPotent or TwrShadow]
default ShearModel         - Shear Model {0: No treatment, 1: Mirrored vorticity, default: 0}
------------------- SPEEDUP OPTIONS -----------------------------------------------------------
default VelocityMethod     - Method to determine the velocity {1:Segment N^2, 2:Particle tree, 3:Particle N^2, 4:Segment tree, default: 2}
default TreeBranchFactor   - Branch radius fraction above which a multipole calculation is used {default: 1.5} [only if VelocityMethod=2,4]
default PartPerSegment     - Number of particles per segment {default: 1} [only if VelocityMethod=2,3]
===============================================================================================
--------------------------- OUTPUT OPTIONS  ---------------------------------------------------
default WrVTk              - Outputs Visualization Toolkit (VTK) (independent of .fst option) {0: NoVTK, 1: Write VTK at VTK_fps, 2: Write VTK at init and final, default: 0} (flag)
default nVTKBlades         - Number of blades for which VTK files are exported {0: No VTK per blade, n: VTK for blade 1 to n, default: 0} (-) 
default VTKCoord           - Coordinate system used for VTK export. {1: Global, 2: Hub, 3: Both, default: 1} 
default VTK_fps            - Frame rate for VTK output (frames per second) {"all" for all glue code timesteps, "default" for all OLAF timesteps} [only if WrVTK=1] 
0       nGridOut           - Number of grid outputs
GridName  GridType  TStart   TEnd    DTGrid   XStart  XEnd   nX   YStart   YEnd   nY   ZStart   ZEnd   nZ
(-)         (-)      (s)     (s)      (s)       (m)    (m)   (-)   (m)     (m)    (-)   (m)     (m)    (-)
===============================================================================================
--------------------------- ADVANCED OPTIONS --------------------------------------------------
===============================================================================================

[jjonkman]

Dear @Laurens09,

Can you also share airfoilEL_1.dat and airfoilEL_5.dat, which are the airfoils triggering these warnings and errors?

Best regards,

[jjonkman]

Dear @Laurens09,

I have not reviewed your airfoil data enough to know what needs to be changed. But the the calculation of the separation function based on the Cl data in the HGM model is documented in Appendix C.2 of the following AeroDyn implementation plan: https://openfast.readthedocs.io/en/main/_downloads/ac04f454598248483d3a339d96dcd4fd/AeroLin_2019-12.pdf. And you can find this method implemented in SUBROUTINE CalculateUACoeffs() of source file AerofoilInfo.f90. And the error that is triggered because your Cl data does not lead to a value of f_st close to unity at any angle of attack appears in SUBROUTINE UA_ValidateAFI() of source file UnsteadyAero.f90.

Best regards,

[Laurens09]

Dear @jjonkman,

I have calculated the separation function for airfoilEL_5.dat according to the Method 1 of Appendix C.2. My calculations show that the separation function reaches 1 for at least one alpha value. (I have used central difference method to calculate Cl_α). Could you suggest me any other way to understand what's wrog whit airfoilEL_5.dat?

Thank you
Best regards

[jjonkman]

Dear @Laurens09,

I would suggest compiling in debug mode and stepping through this part of the solution in the debugger to see how the internal variables are being set and how these differ from your own calculations.

Perhaps others, such as @ebranlard could provide additional guidance.

Best regards,

[Laurens09]

Dear @jjonkman,

I have tried to follow the 2 suggested modes. Both of them doesn't work.
Could you give me any suggestions to make them work?

1. OpenFAST in debug mode
I have run the line command
cmake .. -D CMAKE_BUILD_TYPE=Debug
but it says that cmake is not recognised as internal or external command.

2. Debugger through Visual Studio Code
I have followed all the procedure (https://openfast.readthedocs.io/en/dev/source/dev/debugging.html#debugging-on-linux-and-macos), but when I launch it the "DEBUG CONSOLE" gives me this error:

Could not start debugger process, does the program exist in filesystem?
Error: spawn gdb ENOENT

This is the launch configuration that I have used

{
    "version": "0.2.0",
    "configurations": [

         {
            "name": "AOC_WSt",
            "type": "gdb",
            "request": "launch",
            "printCalls": false,
            "showDevDebugOutput": false,
            "valuesFormatting": "prettyPrinters",
            "gdbpath": "gdb",
            "target": "c:/OpenFAST/AeroDyn_Driver_x64_OpenMP",
            "cwd": "${workspaceRoot}",
            "arguments": "${workspaceRoot}/AERODYN_Driver.dvr"
        }
    ]
}

Best regards

[andrew-platt]

Dear @Laurens09,

Regarding method 1, there is a typo in your cmake command. There should not be a space between the D and the rest of the command. Could you try:
cmake .. -DCMAKE_BUILD_TYPE=Debug

Regards,