Simulation with a tilted tower

Wind & Water Computer-Aided Engineering Software Tools
1

Dear Bonnie,

Please is there a way to simulate bottom fixed wind turbines with tilted towers (which could be as a consequence of some sort of earth movement near a wind farm) using FASTv8?
I want to run a simulation that will enable me compare the power generation and tower stresses between a slightly tilted turbine and an upright one.

Regards.

Michael Olatunde.
MSc. Student, Offshore Engineering,
Newcastle University,
United Kingdom

2

Dear Michael,

You can model a slightly tilted tower in FAST v8 by keeping the platform DOFs disabled, but setting PtfmRoll and/or PtfmPitch nonzero in ElastoDyn.

Best regards,

3

Dear Jason,

Sorry I have not been on the forum for a while. Thank you for your reply.
I am actually simulating a jacket supported wind turbine in 40m water depth using the NREL 5MW baseline turbine. I intend to simulate at 0.25, 0.5, 1.0 and 5.0 degrees of tilt to identify differences in tower top displacement and generator power in different see sates with wind speed below rated speed, as well as overall structure displacement in extreme wind speeds. I have already scaled and transformed the jacket coordinates as required, I have also incorporated apparent fixity at the base.
I would like to know if there would be any consequence as a result of disabling the platform DOFs. I would also like to know if adjusting the platform pitch will change the inclination of the rotor with respect wind direction as well?

Regards.

Michael.

4

Dear Jason,
In addition to my previous questions, I would also like to know if giving a value to the platform pitch/roll adjusts the tower, nacelle and rotor positions as well.
Regards.
Michael

5

Dear Michael,

Yes, assigning a nonzero value for the platform pitch or roll will tilt the tower, yaw axis, nacelle, and rotor from vertical. The rotor can be tilted back to horizontal (or whatever angle is desired) by setting a nonzero value for the shaft tilt (ShftTilt) within ElastoDyn.

Best regards,

6

Hi, Jonson

I need some help from you, we are currently working for a floating WT with 25° tilted tower.
Can OpenFast simulate such high tilted tower? And we also considered applying pre-tensioned cables to stable the tower.
Is the pre-tensioned cables also simulated in OpenFast?
Thanks for your answers in advance.

7

Dear Bingkun,

You can’t use the approach described above to model a wind turbine with a heavily tilted tower.

But we recently introduced the ability in OpenFAST to model the support structure for floating offshore wind turbines with the SubDyn module enabled. There is no restriction in SubDyn that the tower (beam elements) be vertical. Moreover, the recent upgrade also introduces pretensioned cable elements in SubDyn, which also sound relevant to the system you want to model. However, AeroDyn has not yet been upgraded to model the aerodynamic loads on tilted towers. Regardless, you can find more information in the following forum topic: How to apply icedyn to floating turbines in FAST - #2 by Jason.Jonkman.

Best regards,