How to add rigid tower element in FAST v.8.16??

Wind & Water Computer-Aided Engineering Software Tools
1

Hello!!

I am working on adding rigid tower elements to my Floating offshore wind turbine model. From the attached photo, the red hatched part is the rigid tower element I wish to add. I tried to add this rigid part by including elements in TwrFile with very small mass density (I don’t want the mass of the total system to change by adding these elements) and very high stiffness. However, after running the simulation under irregular waves simulation crashed. The warning and error messages are as shown below.

[code]FAST_Solution:FAST_AdvanceStates:ED_ABM4:ED_AB4:ED_RK4:ED_CalcContStateDeriv:SetCoordSy:Small
angle assumption violated in SUBROUTINE SmllRotTrans() due to a large platform displacement
(ElastoDyn SetCoordSy). The solution may be inaccurate. Simulation continuing, but future
warnings from SmllRotTrans() will be suppressed.
Additional debugging message from SUBROUTINE SmllRotTrans(): 1.00000E-02 s
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:SolveOption1:MAP_CalcOutput:MAP_FATAL[40] : Number
of function calls has reached or exceeded INNER_MAX_ITS. Line segment 1.
MAP_FATAL[40] : Number of function calls has reached or exceeded INNER_MAX_ITS. Line segment 2.
MAP_FATAL[40] : Number of function calls has reached or exceeded INNER_MAX_ITS. Line segment 3.
MAP_

FAST encountered an error at simulation time 0 of 100 seconds.
Simulation error level: FATAL ERROR

Aborting FAST.[/code]

Can you please help me solve this issue?? I would be really appreciate.

Thank you

Danupon

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125514136_3403044863124781_2898220047956275054_n.jpg729×961 18.1 KB

2

Dear Danupon,

This is actually easy to do. The TowerBsHt input parameter in ElastoDyn defines the tower base–i.e., the elevation of the tower (for the undisplaced structure) from which the flexible tower with distributed mass and stiffness are defined. That is, HtFract = 0 in the ElastoDyn tower input file is at an elevation of TowerBsHt and HtFract = 1 corresponds to an elevation of TowerHt. Any mass of the tower lower than TowerBsHt in elevation should be lumped into the platform mass, center of mass, and inertias in ElastoDyn.

Best regards,