I just want to ask for the clarification of the local tower load output. I output tower loads at the specific tower sections. TwHt1FLxt, TwHt1FLyt, TwHt1FLzt TwHt1MLxt, TwHt1MLyt, and TwHt1MLzt are requested to be output. However, I am doubtful about the definition of these parameters. According to the “OutListParameters.xlsx”, TwHt1FLxt is “Local tower roll (or side-to-side) force of tower gage 1”. TwHt1FLyt is “Local tower pitching (or fore-aft) force of tower gage 1”. TwHt1FLzt is “Local tower yaw (or torsional) force of tower gage 1”. TwHt1MLxt is “Local tower roll (or side-to-side) moment of tower gage 1”. TwHt1MLyt is “Local tower pitching (or fore-aft) moment of tower gage 1”.Finally, TwHt1MLzt is “Local tower yaw (or torsional) moment of tower gage 1”.
However, I am not quite sure if these parameters refer to the local axis. I checked by running simulations with no external conditions (no wind and wave, only static equilibrium) but many nacelle yaw directions. For the case of nacelle pointing at 0 degree, TwHt1MLyt is larger than TwHt1MLxt which makes sense and I understand that the Fore-aft moment is TwHt1MLyt while the Side-side moment is TwHt1MLxt. However, when the nacelle yaw direction is at 90 degree, TwHt1MLxt is larger than TwHt1MLyt. So, TwHt1MLxt is the Fore-aft Moment which is strange to me because the local axis in my understanding should rotate as nacelle rotates and the fore-aft moment should always be TwHt1MLyt.
So, could you please clarify?