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subtracted, producing the variable flap moment history labeled “Test Data” in Figure 11-5.
The calculated flap moment load at 20 percent of span, again with the average removed, is
also plotted in Figure 11-5, permitting a comparison of the blade's flapping response to grav-
ity, tower shadow, and average wind shear.
The test and calculated wave forms are very similar in Figure 11-5, indicating a
validated computer model for this turbine. However, another HAWT would require a
similar test/calculation comparison for validation of its structural, aerodynamic, and wind
input data. These data are an integral part of the blade load analysis model, and as critical
to validation as the basic equations of motion.
Figure 11-5. Sample comparison between calculated and measured flapwise moment
loads.
The test turbine is the 10.1-m diameter
Grumman
prototype HAWT. [Thresher
et
al.
1986]
Current and Future Developments in Structural-Dynamic Modeling
The demands placed on structural dynamics models are becoming more severe as
turbine designs evolve. Models are being asked to account for more-complex phenomena,
including the following:
-- non-steady air flow
-- blade-to-blade interactions
-- yaw and pitch motions of the nacelle and tower
-- blade pitch control
-- teetering motion
-- variable-speed
-- startup transient
-- shutdown and braking transients
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