Negative Tower Fore-aft deformation at Cut-in wind speed

Wind & Water Structural Analysis
#1

Hello everyone,
I am studying the response of the 15MW model under different loading conditions. The steady-state tower fore-aft deformation at the cut-in wind speed (3 m/s) has a value of -0.38m.
I could not understand why this value is negative. If someone could explain the mechanics behind this, it would be really helpful.

Thanks,
Shubham

#2

Dear Shubham,

My guess is at this low wind speed, the moment from the overhanging weight of the rotor-nacelle assembly, which causes the tower to deflect upwind, is larger than the moment caused by the rotor thrust to deflect the tower downwind.

Best regards,