Marine vessel wave wake

243 Pages·2012·2.61 MB·English

by  Gregor Macfarlane

Marine Vessel Wave Wake:
Focus on Vessel Operations within Sheltered Waterways

Gregor J Macfarlane, B.Eng. (Hons), M.Phil.

Submitted in fulfilment of the
requirements for the Degree of
Doctor of Philosophy

Australian Maritime College, University of Tasmania

5 June 2012
Declarations

Declaration of Originality

This thesis contains no material which has been accepted for a degree or diploma by
the University or any other institution, except by way of background information and
duly acknowledged in the thesis, and to the best of my knowledge and belief no
material previously published or written by another person except where due
acknowledgement is made in the text of the thesis, nor does the thesis contain any
material that infringes copyright.

Authority of Access

This thesis may be made available for loan and limited copying and communication
in accordance with the Copyright Act 1968.

Gregor J Macfarlane
5 June 2012
Abstract

This thesis reports on an investigation into the characteristics of the wave wake
generated by vessels that typically operate within sheltered waterways. It is well
known that these waves can result in issues for other users of the waterway and the
surrounding environment. These issues include erosion of the surrounding banks,
damage or nuisance to moored vessels and other maritime structures and endanger
people working or enjoying activities in small craft or close to the shore.

A review of the wave patterns generated at sub-critical, trans-critical and super-
critical depth Froude numbers has been conducted, with an emphasis on those craft
that commonly utilise sheltered waterways, namely small commercial vessels and
recreational craft. Particular attention was given to planing and wakeboarding
vessels, given the large and increasing number of these craft. One of the major issues
often confronted is that of bank erosion and a study was conducted to determine
which measures of erosion potential are the most descriptive in these circumstances.

Over recent decades it has been common to quantify a vessel’s wave wake using the
characteristics of just a single wave within the entire wave train, usually the highest.
However, in this study it has been shown that this is generally inadequate when
considering craft operating at trans-critical or super-critical speeds. Three significant
waves of interest were described and quantified in this study.

A comprehensive set of model scale experiments was conducted to investigate the
effect that water depth, hull form and vessel speed has on the waves generated by
nineteen different hull forms, including a mixture of typical monohulls and
catamarans. Four primary measures were quantified for each of the three key waves,
including wave height, wave period, decay rate and wave angle.

The results from the experiments were used to develop an empirical tool to provide
wave wake predictions and to investigate the effect that water depth, hull form and
vessel speed has on each of the four primary wave measures. Predictions from the
tool were validated against measured data from several independent full scale trials.

A wave wake regulatory criterion, suitable for the operation of typical recreational
craft and small commercial vessels operating in sheltered waterways, was proposed

and incorporated within the prediction tool.
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Acknowledgements

Many people provided assistance during the course of this study, but special thanks
are due to:

Prof. Neil Bose, supervisor of both my PhD research and my ‘day job’, firstly for his
encouragement and support that has allowed me to undertake this project and for his
valuable guidance along the way.

Dr. Jonathan Duffy, not just for his valuable experience and contribution as co-
supervisor, but also for the splendid job he did while taking over my day job for over
12 months to allow me the opportunity to undertake this rewarding challenge.

My colleagues within the team at the AMC Towing Tank and Model Test Basin,
especially Tim Lilienthal, Kirk Meyer, Drew Honeychurch, Liam Honeychurch and
Shaun Denehy, for their assistance while my attention regularly strayed between my
day job and PhD.

My colleagues and fellow post-graduates within the AMC National Centre for
Maritime Engineering and Hydrodynamics. A special thank you goes to Prof. Martin
Renilson for over 20 years of encouragement and advice.

Friend and fellow PhD candidate, Dr.* Alex Robbins, for countless discussions
related to boats and wave wake, most of which ended off-topic and in fits of laughter.
(*to be confirmed in the near future!).

Various key participants from industry for their valued input, especially naval
architect Greg Cox, geomorphologist Jason Bradbury and cruise vessel
owner/operators Troy and Guy Grining.

My wife, Leanne, and children, Lachlan, Callum, Bethany and Ainsley, for their
support, encouragement and understanding over the past few years while I have tried
(and often failed) to find the right balance between work, study and family. Special
thanks also to my mother, father and two sisters – for similar reasons, but over a
much longer timeframe.

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Table of Contents

Abstract ...................................................................................... i

Acknowledgements ................................................................... ii

List of Figures ......................................................................... vii

List of Tables ............................................................................ xi

Nomenclature .......................................................................... xii

1. Introduction .......................................................................... 1

1.1 Definition of the Problem ............................................................................ 1
1.2 Hypothesis and Research Questions .......................................................... 6
1.3 Overview of Thesis Structure ..................................................................... 6
2. Vessel Generated Waves ...................................................... 9

2.1 Vessel Wave Patterns .................................................................................. 9
2.1.1 Introduction ............................................................................................ 9
2.1.2 Sub-Critical Speeds (Fr < 0.75) .......................................................... 10
h
2.1.3 Trans-critical Speeds (0.75 < Fr < 1.0) ............................................... 12
h
2.1.4 Critical Speed (Fr = 1.0) ..................................................................... 12
h
2.1.5 Super-Critical Speeds (Fr > 1.0) ......................................................... 13
h
2.1.6 Wave Height Constant .......................................................................... 14
2.1.7 Wave Angles ........................................................................................ 16
2.1.8 The Effect of Manoeuvring (Turning) .................................................. 21
2.1.9 The Effect of Propulsors ....................................................................... 22
2.2 Propagating Wave Phenomena ................................................................ 24
2.2.1 Dispersion ............................................................................................. 24
2.2.2 Attenuation ........................................................................................... 26
2.2.3 Wave Energy and Power ...................................................................... 29
2.3 Vessel Speed Regimes ................................................................................ 31
2.3.1 Displacement Speed ............................................................................. 32
2.3.2 Semi-displacement Speed ..................................................................... 32
2.3.3 High Speed (Planing) ........................................................................... 33
2.4 High Speed Planing Vessels ...................................................................... 34
2.4.1 Introduction .......................................................................................... 34
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2.4.2 Hull Resistance Components ................................................................ 35
2.4.3 Planing Action ...................................................................................... 36
2.4.4 Planing Forms and High-Speed Vessel Wave Generation ................... 39
2.4.5 Wake Boarding ..................................................................................... 41
2.5 Sheltered Waterways ................................................................................. 46
2.5.1 Regions ................................................................................................. 46
2.5.2 Types of Bank ...................................................................................... 47
2.5.3 Restricted Waterway Effects ................................................................ 48
2.5.4 Wind Waves ......................................................................................... 50
3. Quantifying Vessel Wave Wake and Bank Erosion ....... 53

3.1 Introduction................................................................................................ 53
3.2 Relevant Wave Wake Characteristics ..................................................... 53
3.3 Wave Measures used in This Study ......................................................... 58
3.4 Quantifying Bank Erosion due to Vessel Wave Wake ........................... 63
3.4.1 Background .......................................................................................... 63
3.4.2 Bank Erosion Studies in Sheltered Waterways .................................... 63
3.4.3 Bank Erosion Studies on the Gordon River, Tasmania ........................ 66
4. Wave Wake Prediction Techniques .................................. 75

4.1 Introduction................................................................................................ 75
4.2 Literature Review ...................................................................................... 76
4.2.1 Prediction of Wave Wake - Experimental Measurement ..................... 77
4.2.2 Prediction of Wave Wake - Computational Methods .......................... 80
4.3 Concluding Remarks on Prediction Techniques .................................... 85
5. Wave Wake Experiments .................................................. 86

5.1 Introduction................................................................................................ 86
5.2 Test Variables ............................................................................................. 87
5.2.1 Ship Models .......................................................................................... 87
5.2.2 Water Depths ........................................................................................ 88
5.2.3 Vessel Speeds ....................................................................................... 90
5.3 Experimental Equipment and Procedures .............................................. 91
5.3.1 Equipment ............................................................................................ 91
5.3.2 Instrumentation ..................................................................................... 93
5.3.3 Test Procedure and Data Acquisition ................................................... 94
5.4 Analysis Process ......................................................................................... 94
5.4.1 Analysis of the Time Series Data ......................................................... 94
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5.4.2 Analysis of Data for Each Ship Model ............................................... 102
5.5 Effect of Vessel Speed and Water Depth ............................................... 102
5.5.1 Wave Height Constant,  .................................................................... 103
5.5.2 Normalised Wave Period, T’ .............................................................. 112
5.5.3 Wave Decay Rate, n ........................................................................... 117
5.5.4 Wave Angle,  .................................................................................... 122
6. Wave Wake Prediction Tool ........................................... 127

6.1 Introduction.............................................................................................. 127
6.2 Development of the Prediction Tool ....................................................... 129
6.2.1 Method of Operation .......................................................................... 129
6.2.2 Limitations and Assumptions ............................................................. 132
6.2.3 Verification ......................................................................................... 136
6.3 Effect of Hull Form .................................................................................. 137
6.4 Application of the Wave Wake Predictor ................................................ 144
6.5 Validation of the Wave Wake Predictor .................................................. 150
6.5.1 Introduction ........................................................................................ 150
6.5.2 Conduct of Full Scale Wave Wake Trials .......................................... 150
6.5.3 Results: 24 m Catamaran .................................................................... 156
6.5.4 Results: 29 m Catamaran .................................................................... 162
6.5.5 Results: Ski Boats ............................................................................... 166
6.5.6 Results: Additional Vessels ................................................................ 170
6.5.7 Concluding Remarks on Validation ................................................... 172
7. Wave Wake Regulatory Criteria .................................... 174

7.1 Introduction.............................................................................................. 174
7.1.1 The Need for Wave Wake Criteria ..................................................... 174
7.1.2 Criteria Requirements ......................................................................... 176
7.1.3 Review of Recent Developments ....................................................... 177
7.1.4 Wave Energy or Power? ..................................................................... 181
7.2 Proposed Regulatory Criteria ................................................................ 182
7.2.1 The Wave Wake Rule .......................................................................... 182
7.2.2 Benchmark Values of Wave Height and Period ................................. 183
7.3 Use of the Wave Wake Predictor with the Wave Wake Rule .................. 185
8. Conclusions, Recommendations and Further Work .... 191

8.1 Conclusions and Recommendations ....................................................... 191
8.2 Further Work ........................................................................................... 196
v
References ............................................................................. 198

Appendix A ............................................................................ 216

Ship Model Body Plans ...................................................................................... 216
Appendix B ............................................................................ 221

Typical Vessel Operations in Australian Sheltered Waterways .................... 221
Appendix C ............................................................................ 223

Use of Spectral Analysis ..................................................................................... 223
Appendix D ............................................................................ 226

Uncertainty Analysis .......................................................................................... 226

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List of Figures

Figure 2.1 Kelvin wave pattern ....................................................................... 11
Figure 2.2 Wave wake patterns ....................................................................... 13
Figure 2.3 Wave height as a function of lateral distance from the sailing line . 16
Figure 2.4 Wave angle  as a function of Fr .................................................. 17
h
Figure 2.5 Wave propagation angle  as a function of Fr .............................. 18
h
Figure 2.6 Aerial photograph of Kelvin wave pattern ..................................... 19
Figure 2.7 Experimental results for leading wave angles ................................ 21
Figure 2.8 Deep water wave dispersion, for different lateral probe positions .. 25
Figure 2.9 Wave decay exponent as a function of Fr (Robbins et al. 2007) ... 29
h
Figure 2.10 Vessel speed regimes ...................................................................... 33
Figure 2.11 Relationship between fully-planing speed and vessel displacement 37
Figure 2.12 Change in dynamic waterline length – pre-planing speed .............. 38
Figure 2.13 Change in dynamic waterline length – planing speed ..................... 38
Figure 2.14 Idealised planing hull form for maximum efficiency ...................... 41
Figure 2.15 Effect of hydrofoil ........................................................................... 44
Figure 3.1 Maximum wave height as a function of slenderness ratio .............. 55
Figure 3.2 Maximum wave height as a function of vessel displacement ......... 55
Figure 3.3 Wave period / L1/2 as a function of length Froude number ............. 56
Figure 3.4 Wave height, period, energy and power as a function of Fr .......... 57
L
Figure 3.5 Example wave profile time series (Waves A, B and C) .................. 61
Figure 3.6 Example wave profile time series ................................................... 62
Figure 3.7 Elevated turbidity as a function of maximum wave height ............. 73
Figure 3.8 Elevated turbidity as a function of wave period .............................. 73
Figure 3.9 Elevated turbidity as a function of wave energy ............................. 74
Figure 3.10 Elevated turbidity as a function of wave power .............................. 74
Figure 5.1 Typical vessel operations within Australian sheltered waterways .. 90
Figure 5.2 Layout of hydrodynamic test basin ................................................. 92
Figure 5.3 Example of analysis of a single wave elevation time series ........... 98
Figure 5.4 Example of wave angle analysis ..................................................... 99
Figure 5.5 Example of analysis of wave height constant, wave decay and
wave period (for Wave A) ............................................................ 100
Figure 5.6 Example of output file from analysis spreadsheet ........................ 101
Figure 5.7 Wave height constant for Wave A,  , as a function of Fr .......... 104
A h
Figure 5.8 Wave height constant for Wave A,  , as a function of Fr ......... 104
A L
Figure 5.9 H/L as a function of y/L: Wave A, h/L = 0.56 ............................. 106
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Figure 5.10 Crest angles of Wave A, y as a function of downstream distance . 107
Figure 5.11 H/L as a function of y/L: Wave A, h/L = 0.19 .............................. 108
Figure 5.12 Wave height constant for Wave B,  , as a function of Fr ........... 110
B h
Figure 5.13 Wave height constant for Wave B,  , as a function of Fr ........... 110
B L
Figure 5.14 Wave height constant for Wave C,  , as a function of Fr ........... 111
C h
Figure 5.15 Wave height constant for Wave C,  , as a function of Fr .......... 111
C L
Figure 5.16 Normalised wave period for Wave A, T ’, as a function of Fr .... 113
A h
Figure 5.17 Normalised wave period for Wave A, T ’, as a function of Fr .... 113
A L
Figure 5.18 Normalised wave period for Wave B, T ’, as a function of Fr .... 115
B h
Figure 5.19 Normalised wave period for Wave B, T ’, as a function of Fr .... 115
B L
Figure 5.20 Normalised wave period for Wave C, T ’, as a function of Fr .... 116
C h
Figure 5.21 Normalised wave period for Wave C, T ’, as a function of Fr .... 116
C L
Figure 5.22 Wave decay exponent for Wave A, n , as a function of Fr .......... 118
A h
Figure 5.23 Wave decay exponent for Wave A, n , as a function of Fr ......... 118
A L
Figure 5.24 Wave decay exponent for Wave B, n , as a function of Fr .......... 119
B h
Figure 5.25 Wave decay exponent for Wave B, n , as a function of Fr .......... 120
B L
Figure 5.26 Wave decay exponent for Wave C, n , as a function of Fr .......... 120
C h
Figure 5.27 Wave decay exponent for Wave C, n , as a function of Fr .......... 121
C L
Figure 5.28 H/L as a function of y/L: Wave A, comparison with Doyle (2001) 122

Figure 5.29 Wave angle for Wave A,  , as a function of Fr .......................... 124
A h
Figure 5.30 Wave angle for Wave A,  , as a function of Fr .......................... 124
A L
Figure 5.31 Wave angle for Wave B,  , as a function of Fr ........................... 125
B h
Figure 5.32 Wave angle for Wave B,  , as a function of Fr .......................... 125
B L
Figure 5.33 Wave angle for Wave C,  , as a function of Fr ........................... 126
C h
Figure 5.34 Wave angle for Wave C,  , as a function of Fr .......................... 126
C L
Figure 6.1 Prediction tool Input Worksheet..................................................... 133

Figure 6.2 Prediction tool Output Worksheet.................................................. 134

Figure 6.3 Example of prediction tool output:  as a function of L/V1/3......... 138

Figure 6.4 Example of prediction tool output: T’ as a function of L/V1/3....... 139

Figure 6.5 Example of prediction tool output: n as a function of L/V1/3......... 139

Figure 6.6 Example of prediction tool output:  as a function of L/V1/3......... 140

Figure 6.7 Example of prediction tool output:  as a function of L/B............. 142

Figure 6.8 Example of prediction tool output:  as a function of L/d ............. 142
.
Figure 6.9 Example of prediction tool output:  as a function of B/d ............. 143
.
Figure 6.10 Example of prediction tool output:  as a function of i ................ 143
E
Figure 6.11 Example of prediction tool output: H as a function of Fr ............. 145
h
Figure 6.12 Example of prediction tool output: T as a function of Fr ............. 145
h
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