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Questions about 15MW Spar-type Model #3370

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@Yangtze20

Dear developers,

I am currently using an unofficial model of a 15 MW Spar-type wind turbine. The specific geometry of the model can be found in the literature (https://www.sciencedirect.com/science/article/pii/S0029801824019504). I have been running some simulations with OpenFAST 3.5.0 and have encountered the following issues:

  1. In the HydroDyn module, when I do not use potential flow theory and the substructure is treated as Morison members, the simulation runs normally without errors. However, when I enable PotMod, errors occur. I believe that for a Spar-type wind turbine model, the potential flow theory solution should be the correct approach, but I am currently unsure how to modify the model. I am attaching the input files for the HydroDyn and MoorDyn modules below and would appreciate your guidance.

  2. When I run step wind simulations with wind speeds from 3 to 25 m/s, I find that the simulation fails when the wind speed exceeds the rated wind speed. The error seems to be caused by large blade deflections leading to tower strikes. How should I handle this, and what settings should I focus on?

The error message for the first issue is as follows:

 ROSCO Warning: Did not find VS_PwrFiltF in input file.  Using default value of    0.0000000000000000     
 ROSCO Warning: Did not find SD_CornerFreq in input file.  Using default value of    0.0000000000000000     
Generator speed:    5.0 RPM, Pitch angle:   0.0 deg, Power:     0.0 kW, Est. wind Speed:   3.0 m/s

 FAST_Solution:CalcOutputs_And_SolveForInputs:SolveOption2:AD_CalcOutput:RotCalcOutput:BEMT_CalcOut
 put(node 49, blade 1):UA_CalcOutput:UA_BlendSteady:Temporarily turning off UA due to high angle
 of attack or low relative velocity. This warning will not be repeated though the condition may
 persist.

 Warning: SkewedWakeCorrection encountered a large value of chi (90.24 deg), so the yaw correction
 will be limited. This warning will not be repeated though the condition may persist. See the AD15
 chi output channels, and consider turning off the Pitt/Peters skew model (set SkewMod=1) if this
 condition persists.


 FAST_Solution:CalcOutputs_And_SolveForInputs:SolveOption2:AD_CalcOutput:RotCalcOutput:BEMT_CalcOut
 put(node 14, blade 3):UA_CalcOutput:Mach number exceeds 0.3. Theory is invalid. This warning will
 not be repeated though the condition may persist.


 FAST_Solution:FAST_AdvanceStates:ED_ABM4:ED_CalcContStateDeriv:SetCoordSy:Small angle assumption
 violated in SUBROUTINE SmllRotTrans() due to a large blade deflection (ElastoDyn SetCoordSy). The
 solution may be inaccurate. Simulation continuing, but future warnings from SmllRotTrans() will
 be suppressed.
  Additional debugging message from SUBROUTINE SmllRotTrans(): 7.95 s

 The BEM solution is being turned off due to low TSR.  (TSR = -1.4597). This warning will not be
 repeated though the condition may persist. (See GeomPhi output channel.)

 FAST_Solution:CalcOutputs_And_SolveForInputs:SolveOption2:AD_CalcOutput:RotCalcOutput:BEMT_CalcOut
 put(node 41, blade 1):UA_CalcOutput:Mach number exceeds 1.0. Equations cannot be evaluated.

 OpenFAST encountered an error at simulation time 7.96 of 600 seconds.
  Simulation error level: FATAL ERROR

  Aborting OpenFAST.

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