Table of contents

1 Summary

2 Acknowledgments

3 Introduction

3.1 Flutter

3.2 In-flight flutter testing

3.2.1 Current methods of exciting airframes

3.2.1.1 Pyrotechnics

3.2.1.2 Aerodynamic excitation

3.2.1.3 Mechanical excitation

3.2.1.4 Control surface excitation

3.3 Mathematical methods used

3.3.1 Spectral analysis and the power spectral density function

3.3.2 Source-sink panel method

4 Wind tunnel balance calibration

4.1 Method

4.1.1 Loadcell calibration against voltmeter readings

4.1.2 Digital acquisition system calibration against voltmeters

4.2 Generating a calibration matrix

4.3 Errors

4.4 Discussion

4.4.1 Combined loadings

4.4.2 Accuracy

5 Aerodynamic testing

5.1 Equipment used

5.2 Method

5.3 Results

5.4 Discussion

5.4.1 Mechanical vibration of the model

5.4.1.1 Inertial excitation due to cylinder vibrations

5.4.1.2 Vibration modes of the model

5.4.2 Power supply interference

5.4.3 Noise due to cyclic loading

5.4.4 Low signal

5.4.4.1 Excessive gap in the rotating cylinder

5.4.4.2 Excessive gap between the plate and cylinder

5.4.5 Wall effects and blockage

5.4.6 Errors

6 Computational Modelling

6.1 The wake deflection model

6.1.1 Model creation

6.1.2 Results

6.2 The rear plate model

6.2.1 Model creation

6.2.1.1 Variations on the model

6.2.2 Results

6.2.2.1 Lift curve slope

6.2.2.2 Effect of the main plate

6.2.3 Discussion

6.2.3.1 Lift curve

6.2.3.2 Relative effect of main and rear plates

6.2.3.3 Plate gap spacing

6.3 The split cylinder model

6.3.1 Model creation

6.3.1.1 Variations

6.3.2 Results

6.3.3 Discussion

6.3.3.1 Relative effect of upper and lower exciter vanes

6.3.3.2 Effect of the model upon the results

6.3.3.3 Design parameters

Planform dimensions

Vane spacing

Cylinder radii

6.3.3.4 Effectiveness of the split cylinder concept

7 Conclusion

8 Recommendations

8.1.1 Design recommendations

9 References