Questions about wind turbine tower base moment

Wind & Water Computer-Aided Engineering Software Tools
1

Hi everyone,

I am now doing the simulation of OC3Hywind wind turbine and wanna calculate the stress on the tower base. However, I feel confused with some questions:

  1. I have set the directions of wind and waves for 0 degree that means along the X axis. But I find that the output of the wind speed does not equal to 0 (for Y and Z directions). I used kaimal spectrum to generate the wind files.
  2. The bending moment of tower base for X direction does not equal to 0. (I think if wind and waves are aligned with X axis, the bending moment for X axis should be 0)

Many thanks
Jerome

2

Dear Jerome,

Here are my answers to your questions:

  1. By “Kaimal spectrum”, I assume you mean that you are using TurbSim. Even if the mean wind speed propagates along the global X-axis, TurbSim will include lateral wind fluctuations (horizontal and vertical), whose mean is zero, but whose variations are not.
  2. The lateral wind fluctuations will bring about tower-base bending moments about the x-axis. Moreover, the torque generated by the rotor will result in tower-base bending moments about the x axis (including a nonzero mean).

Best regards,

3

Hi Jason,

Thanks for your kindly help. I just did another simulation. I have set the wind type for steady with a very small wind speed (0.00001m/s) and I also changed the wave file for the still water. Then I got a figure for the x axis bending moment which is attached in the topic. Do you think it is feasible for the tendency of the bending moment? why does the bending moment not equal to a constant?

Many Thanks
Jerome

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4

Dear Jerome,

I can’t seem to view your image, so, I can’t really comment.

Best regards,

5

Hi Jason,

I mean is it possible to change the wind speed to 0m/s to investigate the wave induced stress on the wind turbine?

Kind Regards
Junyi

6

Dear Junyi,

If you don’t want aerodynamic loads, it is better to disable the aerodynamics calculations all together by setting CompAero to 0 in the FAST primary input file, rather than by setting the wind speed to zero.

Best regards,