I set an monotower structure with SNL13.2-00 blade in FAST. The hub height is 127.73m above MSL with water depth 30m. I tried to get some info regarding the tower base moment and associated stress.
Firstly I ran this model with all DoFs off and wind speed 72 m/s. Up to now, I did not include any loads from wave and current.
I ran 100s simulation and output the last 10s results. I did not pitch the blade so that it represents one of the most severe situation.
TwrBsMyt: 1,084,000 (kNm)
TwrBsMxt: 50,760 (kNm)
RotThrust: 7,562 (kN)
I tried to correlate these three outputs but the problems are,
- RotThrust * (HH above mud line) (1,192,754) is not equal to 1,084,000 (kN*m);
- Why is there a TwrBsMxt: 50,760 (kN*m)? I am still feeling confused about the reason for side-side moment. Is it from the non-symmetry?
- In FAST, TwrBsMyt is calculated based on what consideration? Which one is better choice for analyzing the bending stress level in tower design?
- Is the rotor load too high that the blades DoFs should be on in my tower design analysis?