Page 333 - Wind Energy Handbook
P. 333
TOWER LOADING 307
450
Wind speed = 8 m/s nS(n) for tower base fore-aft
400
Integral length scale = 73.5 m bending moment divided by
Turbulence intensity = 20% hub height, H
350 Von Karman spectrum
Power spectral density nS(n) (kN) 2 250 Tower natural frequency = 1.16 Hz
300
Rotational speed = 0.5 Hz
Damping ratio = 0.022
200
150
100
nS(n) for Thrust x 10
50
0
0.01 0.1 1 10
Frequency (Hz, logarithmic scale)
Figure 5.44 Power Spectra of Rotor Thrust and Resultant Tower Base Fore–aft Bending
Moment for Three-bladed, 40 m Diameter Turbine
500
450 nS(n) for tower base fore-aft
Wind speed = 8 m/s bending moment divided by
Integral length scale = 73.5 m
400 Turbulence intensity = 20% hub height, H
Von Karman spectrum
Power spectral density nS(n) (kN) 2 300 Tower natural frequency = 1.16 x (1.225/1.5) Hz
350
Rotational speed = 0.5 x 1.225 Hz
Damping ratio = 0.022
250
200
150
100 nS(n) for Thrust x 10
50
0
0.01 0.1 1 10
Frequency (Hz, logarithmic scale)
Figure 5.45 Power Spectra of Rotor Thrust and Resultant Tower Base Fore–aft Bending
Moment for Two-bladed, 40 m Diameter Turbine
