Simulation errors of MIT NREL TLP (Test 23)

Discuss theory and modeling of wind-turbine structures.

Moderator: Bonnie.Jonkman

Yajun.Ren
Posts: 37
Joined: Mon Jan 21, 2019 6:54 am
Organization: The University of Edinburgh
Location: UK

Simulation errors of MIT NREL TLP (Test 23)

Postby Yajun.Ren » Thu Jun 04, 2020 2:28 pm

Dear all,

I was trying to run the simulation using Test 23 files and got some problems.

I used the environmental condition used for model validation in https://www.nrel.gov/docs/fy10osti/45891.pdf (Denis's PhD thesis): 11 m/s hub-height wind speed, 10-m significant wave height and Tp of 17.64s. Based on the inital files, I made the following modifications:

In ElastoDyn, I disabled all the other DoFs except for the last six for the platform motion. RotSpeed was set to zero and BlPitch(i) were set to 90 in order to model the parked turbine state.
In HydroDyn, I changed WaveHs to 10 and WaveTp tp 17.64 and WaveDir to 0.
In AeroDyn, I raised the first aerodynamic node to 10m above the SWL and set WakeMod to zero.
In ServoDyn, I turned off the generator.
Besides, I extend the simulation time in fst file and HydroDyn file to 10800 s (3h) and increased Dt to 0.25.

I got the following error messeges:
FAST_Solution:CalcOutputs_And_SolveForInputs:SolveOption1:ED_HD_InputOutputSolve:HydroDyn_CalcOutp
ut: Angles in GetSmllRotAngs() are larger than 0.4 radians.
ED_HD_InputOutputSolve:HydroDyn_CalcOutput: Angles in GetSmllRotAngs() are larger than 0.4
radians.


FAST_Solution:CalcOutputs_And_SolveForInputs:SolveOption2:InflowWind_CalcOutput:CalcOutput:IfW_Uni
formWind_CalcOutput:GetWindSpeed:Height must not be negative.
IfW_UniformWind_CalcOutput: Error calculating the wind speed at position (-4.31086E+09,
2.42859E+09, -4.99252E+09) in the wind-file coordinates
CalcOutputs_And_SolveForInputs:SolveOption1:ED_HD_InputOutputSolve:HydroDyn_CalcOutput: Angles in
GetSmllRotAngs() are larger than 0.4 radians.
ED_HD_InputOutputSolve:HydroDyn_CalcOutput: Angles in GetSmllRotAngs() are larger than 0.4
radians.

FAST encountered an error at simulation time 7.75 of 10800 seconds.
Simulation error level: FATAL ERROR

Aborting FAST.


I think FAST is capable of simulating the model under the environment I used since this has been done according to the previous published work. Could you give any suggestions about correcting the input files? I would appreciate your kind help.

Best regards,
Yajun

Jason.Jonkman
Posts: 4952
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Simulation errors of MIT NREL TLP (Test 23)

Postby Jason.Jonkman » Thu Jun 04, 2020 3:47 pm

Dear Yajun,

Increasing the time step to DT=0.25 s is likely leading to a numerical instability in the FAST solution. While you have disabled structural DOFs, one or more of the remaining 6 DOFs platform frequencies is likely high enough that a smaller time step is required. My rule of thumb for selecting the time step for the structural module is given in the following forum topic: viewtopic.php?f=4&t=351&p=1025.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov


Return to “Structural Analysis”

Who is online

Users browsing this forum: Google [Bot] and 1 guest