flow near an F-15 vertical tail develops nearly periodic velocity fluctuations.
frequency corresponding to these velocity fluctuations is linear with velocity.
reduced frequency can be defined to show the frequency/velocity/model size
excitation frequencies can be predicted for different model sizes and flow
empirical reduced frequency variation can identify the tuning of velocity
fluctuations to given tail structural modes.
test data should be reviewed to identify test conditions where predicted
flow excitations tune to full scale tail structural modes.
F-15 Tail Buffet Alleviation
Velocity Spectra Frequency
vs. Velocity Reduced Frequency
F-15 Torsion 4.7% F-15
Bending Empirical Prediction
vs. Test Data
flights need to be run at conditions which predict flow/structure tuning.