IEA 15 MW and Thrust

1

Hi everyone,

For semisub floating turbines, I am trying to estimate the influence of a platform pitch angle on the turbine power.
Paramount to that is the accuracy of the rotor thrust as it will directly impact the platform pitch.
In Fig 3.1 of the IEA15MW report (available at : https://www.nrel.gov/docs/fy20osti/75698.pdf), a steady-state value of ca. 1,500kN thrust at 6.98m/s. According to my calculations, this would result in a Ct of 1.11 whereas a Ct of 0.80 is reported. Am I misunderstanding something here?

Further, the DTU report of the IEA15MW (available at https://corewind.eu/wp-content/uploads/files/publications/COREWIND-D1.1-Definition-of-the-15MW-reference-wind-turbine.pdf?v20200617) also reports thrust in Fig. 7. At a similar wind speed of ca. 7m/s, I read a thrust around 1,000/1,100kN which would therefore induce a lower platform pitch.

Is this considerable difference in thrust due to different elastic models being used in the two cases? If so, are you aware of any validation against experimental data of the different elastic models?

Thanks in advance for your help,

Bruno.

2

Hello, @Bruno.Nguyen

If I am not mistaken, the larger value of thrust reported in the IEA15MW report includes not only the aerodynamic load, but also the weight of the rotor (similar to what is explained in this post NREL 5-MW reference turbine - CP, CQ, CT Coefficients - #33 by Jason.Jonkman), while the one from DTU is only the aerodynamic force. You can check that the difference between these two values is the weight of the rotor times the sine of the tilt angle.

BR,
Lucas

2 Likes
3

Hi Lucas,

Thanks for the explanation, this does indeed explain the offset in thrust :slight_smile:
Have a nice day!
bruno

1 Like