an acoustic countermeasure to supercavitating torpedoes

290 Pages·2009·14.77 MB·English

AN ACOUSTIC COUNTERMEASURE TO
SUPERCAVITATING TORPEDOES
A Thesis
Presented to
The Academic Faculty
by
Peter J. K. Cameron
In Partial Fulfillment
of the Requirements for the Degree
Doctor of Philosophy in the
School of Mechanical Engineering
Georgia Institute of Technology
May 2009
Copyright (cid:13)c 2009 by Peter J. K. Cameron
AN ACOUSTIC COUNTERMEASURE TO
SUPERCAVITATING TORPEDOES
Approved by:
Dr. P. H. Rogers, Committee Chair Dr. M. K. Smith
School of Mechanical Engineering School of Mechanical Engineering
Georgia Institute of Technology Georgia Institute of Technology
Dr. A. A. Ferri D. Trivett
School of Mechanical Engineering School of Mechanical Engineering
Georgia Institute of Technology Georgia Institute of Technology
Dr. M. Ruzzene Dr. B. T. Zinn
School of Aerospace Engineering School of Aerospace Engineering
Georgia Institute of Technology Georgia Institute of Technology
Date Approved: May 11, 2009
ACKNOWLEDGEMENTS
I would like to express my gratitude to Professor Peter H. Rogers, who, as my advisor,
has guided me through and supported my research work. It has been a privilege to
be his student and to be able to benefit from his expertise, experience, and insight.
I would also like to thank my other committee members, Dr. Aldo A. Ferri, Dr.
Massimo Ruzzene, Dr. Marc K. Smith, Dave Trivett, and Dr. Ben T. Zinn for their
input and suggestions.
I wish a special thanks to John Doane for countless and invaluable discussions,
advice, and ideas throughout the duration of my dissertation work.
Many thanks also go to Dave Gifford for his input, advice, help, and experience
with various aspects of my experimental work.
I am also very grateful to others in our research group for their interest in my work
and the resulting discussions: Jayme Caspall, Jim Martin, Gregg Larson, Francois
Guillot, and Michael Gray.
I would like to thank my friends for support in all aspects of life as a gradu-
ate student: James Hamlin, Suzanna Sayre, Melissa Deen Hallow, Rebecca Burnos,
Kacey-Jane Ivey, Stephen Steinmann, Laura Stiltz, Nick Krizan, Eric Stockwell, Shai
Birmaher, Gerald Lopez, Mike Leclerc, Mark Kiefert, Mark Gertrudes, and Neil
Ferrier.
I can not thank my family enough for their love and support: my parents, of
course, Kenneth and Marie, and my three brothers, Kim, Jamie, and Michael.
This work was entirely supported by Professor Peter H. Rogers through the Rae
and Frank H. Neely Chair.
iii
TABLE OF CONTENTS
ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x
LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xii
LIST OF SYMBOLS OR ABBREVIATIONS . . . . . . . . . . . . . . . . . . xvii
GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii
SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii
I INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Background and Motivation . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Introduction to Cavitation and Supercavitation . . . . . . . . . . . 2
1.3 Current Torpedo Countermeasures . . . . . . . . . . . . . . . . . . 5
1.4 Thesis Hypothesis: An Acoustic Countermeasure . . . . . . . . . . 6
1.5 Research Questions and Objectives . . . . . . . . . . . . . . . . . . 6
1.6 Research Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
II BACKGROUND AND SURVEY OF RELEVANT WORK . . . . . . . . 9
2.1 Supercavitation of Free Projectiles . . . . . . . . . . . . . . . . . . 10
2.1.1 Analytical Models for Cavity Prediction . . . . . . . . . . . 11
2.1.1.1 Garabedian’s Supercavity Shape Prediction Model 13
2.1.1.2 Logvinovich’s Supercavity Prediction Model . . . . 14
2.1.1.3 Some Other Supercavity Prediction Models . . . . 16
2.1.2 Numerical Modeling for Cavitation and Supercavitation . . 18
2.1.2.1 Boundry Element Methods . . . . . . . . . . . . . 19
2.1.2.2 Slender Body Theory . . . . . . . . . . . . . . . . 19
2.1.2.3 Computational Fluid Dynamics (CFD) . . . . . . 20
2.1.3 Projectile Dynamics . . . . . . . . . . . . . . . . . . . . . . 22
2.1.3.1 Forces on a Disk Shaped Cavitator . . . . . . . . . 23
iv
2.1.3.2 Forces on the Projectile Tail . . . . . . . . . . . . 26
2.1.3.3 Projectile Trajectory . . . . . . . . . . . . . . . . . 29
2.1.3.4 Projectile Dynamics Simulations . . . . . . . . . . 32
2.1.4 Experimentation . . . . . . . . . . . . . . . . . . . . . . . . 34
2.2 Focused Acoustics in Water . . . . . . . . . . . . . . . . . . . . . . 36
2.2.1 Focused Signals . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.2.2 Acoustic Cavitation in Water . . . . . . . . . . . . . . . . . 38
2.2.2.1 Experimental Findings and Cavitation Theory . . 40
2.2.2.2 Detection of Acoustic Cavitation . . . . . . . . . . 42
2.2.3 Properties of Bubbly Water . . . . . . . . . . . . . . . . . . 44
2.2.4 Time Reversal Acoustics . . . . . . . . . . . . . . . . . . . . 47
III SIMULATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
3.1 Modeling the Supercavity Shape Around the Projectile . . . . . . . 51
3.2 Supercavitating Body Dynamics Simulation . . . . . . . . . . . . . 54
3.3 Effects of Imposed Pressures on A Supercavity . . . . . . . . . . . 62
3.3.1 Relevant Work in the Literature . . . . . . . . . . . . . . . 62
3.3.2 Investigation of an Externally Imposed Acoustic Signal . . . 64
IV EXPERIMENT DESIGN AND TESTING . . . . . . . . . . . . . . . . . 68
4.1 Apparatus Design . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
4.1.1 General Approach . . . . . . . . . . . . . . . . . . . . . . . 69
4.1.2 Water Tank . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.1.3 Firing Mechanism . . . . . . . . . . . . . . . . . . . . . . . 70
4.1.4 Projectiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.2 Experimental Measurements . . . . . . . . . . . . . . . . . . . . . . 78
4.2.1 Photography: Imaging and Measurement . . . . . . . . . . . 78
4.2.1.1 Photography: Imaging . . . . . . . . . . . . . . . . 78
4.2.1.2 Photography: Speed Measurement . . . . . . . . . 82
4.2.1.3 Photography: Cavity Shape Measurement . . . . . 82
v
4.2.2 Projectile Speed Measurement Using Electromagnetic Induc-
tion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
4.2.3 Measurement of Impact Location . . . . . . . . . . . . . . . 89
4.3 Apparatus Testing and Control Experiment Data . . . . . . . . . . 91
4.3.1 General Flight Characteristics . . . . . . . . . . . . . . . . . 92
4.3.2 Projectile Trajectory Data . . . . . . . . . . . . . . . . . . . 93
4.3.3 Projectile Speed Data . . . . . . . . . . . . . . . . . . . . . 99
4.3.4 Cavity Geometry . . . . . . . . . . . . . . . . . . . . . . . . 103
4.3.5 Summary of Control Shot Statistics . . . . . . . . . . . . . . 106
4.4 Acoustic Array Design and Sound Field Measurements . . . . . . . 107
4.4.1 General Array Design . . . . . . . . . . . . . . . . . . . . . 108
4.4.1.1 Geometric Configuration . . . . . . . . . . . . . . 108
4.4.1.2 Source Transducer Characterization . . . . . . . . 110
4.4.1.3 Power Supply . . . . . . . . . . . . . . . . . . . . . 113
4.4.2 Triggering the Acoustic Signal . . . . . . . . . . . . . . . . . 114
4.4.3 Sound Field in a Free Field Environment with a Low Ampli-
tude Sound Pressure . . . . . . . . . . . . . . . . . . . . . . 115
4.4.3.1 Geometric Array Symmetry . . . . . . . . . . . . . 116
4.4.3.2 Measure of Array Focus and Tuning . . . . . . . . 117
4.4.3.3 Sound Field . . . . . . . . . . . . . . . . . . . . . 120
4.4.4 Sound Field in the Confined Environment with a Low Am-
plitude Sound Pressure . . . . . . . . . . . . . . . . . . . . 125
4.4.4.1 Configuration . . . . . . . . . . . . . . . . . . . . . 127
4.4.4.2 Sound Field . . . . . . . . . . . . . . . . . . . . . 128
4.4.5 Summary of Sound Field Results for Linear Acoustic Ampli-
tudes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
4.4.6 Sound Field in the Confined Environment with a High Am-
plitude Sound Pressure . . . . . . . . . . . . . . . . . . . . 138
V EXPERIMENTS AND RESULTS . . . . . . . . . . . . . . . . . . . . . 147
5.1 General Overview of Experiment Cases . . . . . . . . . . . . . . . . 148
vi
5.2 Notes on Statistical Measures and Inferences . . . . . . . . . . . . . 150
5.2.1 Target Impact Location Analysis . . . . . . . . . . . . . . . 150
5.2.1.1 Inferences Based on Coordinate Direction Standard
Deviation . . . . . . . . . . . . . . . . . . . . . . . 150
5.2.1.2 Inferences Based on Circular Error Probable . . . 151
5.2.2 Projectile Speed Analysis . . . . . . . . . . . . . . . . . . . 151
5.3 Experiment Description and Results Presentation . . . . . . . . . . 152
5.3.1 Experiment Description and Results: Varying Signal Ampli-
tude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
5.3.1.1 Experiment Description . . . . . . . . . . . . . . . 152
5.3.1.2 Sound Pressure Recordings . . . . . . . . . . . . . 154
5.3.1.3 Imaging . . . . . . . . . . . . . . . . . . . . . . . . 157
5.3.1.4 Cavity Dimensions . . . . . . . . . . . . . . . . . . 159
5.3.1.5 Target Impact Location . . . . . . . . . . . . . . . 166
5.3.1.6 Projectile Speed . . . . . . . . . . . . . . . . . . . 167
5.3.2 ExperimentDescriptionandResults: VaryingSignalFrequency171
5.3.2.1 Experiment Description . . . . . . . . . . . . . . . 171
5.3.2.2 Sound Pressure Recordings . . . . . . . . . . . . . 172
5.3.2.3 Imaging . . . . . . . . . . . . . . . . . . . . . . . . 172
5.3.2.4 Cavity Dimensions . . . . . . . . . . . . . . . . . . 173
5.3.2.5 Target Impact Location . . . . . . . . . . . . . . . 181
5.3.2.6 Projectile Speed . . . . . . . . . . . . . . . . . . . 183
5.4 Interpretation of the Experiment Results . . . . . . . . . . . . . . . 188
5.4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 188
5.4.2 Further Investigation of the Results . . . . . . . . . . . . . . 189
5.4.3 Hypotheses . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
5.4.3.1 The Hypothesis that Changes in Cavity Geometry
Adversely Affect Projectile Accuracy . . . . . . . . 197
vii
5.4.3.2 TheHypothesisthatAcousticCavitationAltersthe
Medium and Thus Adversely Affects Projectile Ac-
curacy . . . . . . . . . . . . . . . . . . . . . . . . . 198
VI CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
6.1 Summary of the Work . . . . . . . . . . . . . . . . . . . . . . . . . 207
6.2 Discussion of the Research Questions . . . . . . . . . . . . . . . . . 208
6.3 Thesis Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . 210
6.4 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
6.4.1 Developments of the Current Work . . . . . . . . . . . . . . 211
6.4.1.1 Conducting Experiment Cases with a More Com-
prehensive Range of Amplitudes . . . . . . . . . . 212
6.4.1.2 Conducting Experiment Cases with a More Com-
prehensive Range of Frequencies . . . . . . . . . . 212
6.4.1.3 Subjecting the Cavity to an Asymmetric Pressure
Field . . . . . . . . . . . . . . . . . . . . . . . . . 215
6.4.1.4 Optimization and Enhancement of the Effect . . . 215
6.4.2 Suggested Research Directions . . . . . . . . . . . . . . . . 216
6.4.2.1 Work Towards a Practical Application . . . . . . . 216
6.4.2.2 Fluid Models and Experiments . . . . . . . . . . . 218
APPENDIX A LOGVINOVICH’S MODEL FOR CAVITY SHAPE PREDIC-
TION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
A.1 Logvinovich: Energy Approach . . . . . . . . . . . . . . . . . . . . 220
A.2 Logvinovich: Newtonian Approach . . . . . . . . . . . . . . . . . . 222
APPENDIX B PROJECTILE TECHNICAL DRAWINGS . . . . . . . . . 226
B.1 Projectile Design Used in the Experiments . . . . . . . . . . . . . . 226
B.2 Projectile Designs Tested but not Used in This Work . . . . . . . . 226
APPENDIX C DRAG COEFFICIENT DATA FROM KICENIUK 1954 FOR
DISK CAVITATORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
APPENDIX D HYDROPHONE CALIBRATIONS . . . . . . . . . . . . . 235
D.1 ReciprocityCalibrationfortheHydrophone: B&K8103(SN:2206083)
236
viii
D.2 Comparison Calibration for the Hydrophone: B&K 8100 (SN:1216465)240
D.3 Hydrophone Polarization . . . . . . . . . . . . . . . . . . . . . . . . 240
D.4 Hydrophone Calibration Curves Provided by the Manufacturer . . 242
APPENDIX E ITC 6135-1 TRANSDUCER TRANSMITTING VOLTAGE
RESPONSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
APPENDIX F SAMPLE CONSECUTIVE FRAMES FROM A TYPICAL
SHOT WITH NO IMPOSED ACOUSTIC PRESSURE . . . . . . . . . . 247
APPENDIX G SAMPLE CONSECUTIVE FRAMES FROM A TYPICAL
SHOT WITH AN IMPOSED ACOUSTIC PRESSURE . . . . . . . . . . 248
APPENDIX H ACOUSTIC PRESSURE SIGNALS . . . . . . . . . . . . . 249
APPENDIX I TARGET IMPACT LOCATIONS . . . . . . . . . . . . . . 257
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
ix
LIST OF TABLES
1 Statistics of manufactured projectile mass and dimensions . . . . . . 78
2 Polynomialcoefficientsforbestfitlinesandtheoreticalcurvesinfigure29105
3 Summary of control sample statistics . . . . . . . . . . . . . . . . . . 106
4 Summary of the array focal region in a free-field environment . . . . . 138
5 Approximate typical amplitudes for the attenuation levels discussed in
the text. For plots of typical pressure measurements for each case see
appendix H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
6 Average values of the measurements of cavity radius at the projectile
tail that are presented in figure 57 . . . . . . . . . . . . . . . . . . . . 161
7 Measures of projectile accuracy for the experiment cases with ranging
pressure amplitude at a signal frequency of 12 kHz . . . . . . . . . . 167
8 Drag coefficients calculated from measured speeds for the varying am-
plitude experiments at 12 kHz . . . . . . . . . . . . . . . . . . . . . . 168
9 Summary of the experiment cases done . . . . . . . . . . . . . . . . . 171
10 Average values of the measurements of cavity radius at the projectile
tail that are presented in figure 63. . . . . . . . . . . . . . . . . . . . 178
11 Average values of the measurements of cavity radius at the projectile
tail that are presented in figure 64. . . . . . . . . . . . . . . . . . . . 178
12 Measures of projectile accuracy for the experiment cases with medium
level acoustic pressure amplitude and ranging signal frequency . . . . 182
13 Measures of projectile accuracy for the experiment cases with low level
acoustic pressure amplitude and ranging signal frequency . . . . . . . 182
14 Drag coefficients calculated from measured speeds for the varying fre-
quency experiments at medium amplitude . . . . . . . . . . . . . . . 184
15 Drag coefficients calculated from measured speeds for the varying fre-
quency experiments at low amplitude . . . . . . . . . . . . . . . . . . 187
16 Summary of the projectile accuracy results. . . . . . . . . . . . . . . 188
17 Measurements of circular error probable (CEP) for shots identified to
have or not have an incidence of tail-slap in the recorded view. Exper-
iment cases with an acoustic signal frequency of 12 kHz and at high,
medium, and low amplitude. . . . . . . . . . . . . . . . . . . . . . . . 190
x