Further development of ship added resistances in head waves

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FURTHER DEVELOPMENT OF SHIP ADDED RESISTANCES IN HEAD WAVES

IWAN ZAMIL BIN MUSTAFFA KAMAL

A dissertation submitted in partial fulfillment of the requirements for the award of the degree of Master of Engineering (Marine Technology)

Faculty of Mechanical Engineering Universiti Teknologi Malaysia

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ABSTRACT

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ABSTRAK

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TABLE OF CONTENTS

CHAPTER TITLE` PAGE

SUPERVISOR’S DECLARATION i

TITLE PAGE ii

DECLARATION iii

DEDICATION iv

ACKNOWLEDGEMENT v

ABSTRACT vi

ABSTRAK vii

TABLE OF CONTENTS viii

LIST OF FIGURES xii

LIST OF TABLES xvi

LIST OF NOMENCLATURE xvii

LIST OF APPENDICES xx

1 INTRODUCTION 1

1.1 Background of Study 1

1.2 Problem Statement 2

1.3 Objectives of the Research 2

1.4 Scope of the Research 3

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2 LITERATURE REVIEW 6

2.1 Regular Waves 6

2.2 The Velocity Potential 9

2.3 Pressure Contours and the Surface Profile 10

2.4 Energy in a Regular Wave 15

2.5 Encounter Frequency and Heading 17 2.6 Axes and Ship Motion Definitions 19 2.7 Simplified Equations of Ship Motion 23 2.8 Added Resistance and Involuntary Speed Loss

in Waves

19

2.9 Simple Theory for Added Resistance in Regular Waves

24

2.10 Korvin-Kroukovsky’s and Jacob’s Strip Theory

32

3 METHODOLOGY 34

3.1 Introduction 34

3.2 Experiment apparatus and facility 34

3.2.1 Towing Carriage 34

3.2.2 Wave Generator 39

3.2.3 Data acquisition and analysis system (D.A.A.S.)

40

3.2.4 Model Test Preparation 42

3.2.5 Model Test Particulars 43

3.3 Experiments Setup 45

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3.5 Theoretical Prediction 49 3.5.1 Added Resistance in Regular Waves

– Momentum and Energy method

49

3.5.2 Strip Theory 53

3.5.2 Calculation of the Coupled Heaving and Pitching Motions by Strip

Theory

55

3.5.2.1 Basic Force Equation 58

3.5.2.2 Applied Force Equation 47

3.5.2.3 Motion Equation 60

3.5.2.4 Solutions of Equation of Motions

66

3.6 Computational Software method – Seakeeper® 68

3.6.1 Coordinate System 69

3.6.2 Computational Methods 70

3.6.3 Limitations and Guidelines of Seakeeper®

71

3.6.3.1 Underlying Assumptions 71

4 TOWING TANK EXPERIMENTS 73

4.1 Model Experiments 73

4.2 Blockage Correction 74

4.3 Experiment Results 77

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5.1 Obtaining added resistance values from Seakeeper ®

81

5.2 Added Resistance Computations in Seakeeper®

91

6 PROGRAM DEVELOPMENT USING FORTRAN 77

94

6.1 Program Development 94

6.2 Mathematical formulation used in the program 98

6.3 Simpson Rules in the Program 98

6.4 Input and Output Results 106

7 RESULTS AND DISCUSSIONS 111 7.1 Added resistance in waves results from

experimental works

112

7.2 Comparison of Added Resistance between Experiment and Theoretical Results

117

7.3 Ship Generated Waves Results 126

8 CONCLUSIONS 131

8.1 Recommendations 134

REFERENCES 135

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LIST OF FIGURES

FIGURE NO. TITLE PAGE

1.1 Research Project Flow Chart 4

2.1 Regular Waves 7

2.2 Constant pressure contour beneath a regular wave 11 2.3 Constant pressure contours beneath a 100 m wave: depth

100m

13

2.4 Regular waves pictured in space and time 14

2.5 Kinetic energy in a regular wave 16

2.6 Heading definitions 18

2.7 Axes and ship motion definitions 20

2.8 Definition of added resistance in waves 24 2.9 Added resistance response curve for a fast cargo ship in

regular waves

27

3.1 Towing Tank Basin 35

3.2 Towing Carriage 35

3.3 UTM Marine Technology Laboratory Layout Plan 36 3.4 A tanker model locked to gimbals during towing 39

3.5 Wave generator flap 40

3.6 Data Acquisition and Analysis System 42

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3.8 The arrangement of air struts and towing guide with ship model

46

3.9 The block diagram of Data Acquisition Analysis System (DAAS)

47

3.10 Representation of underwater hull section shapes by an infinite cylinder

54

3.11 Seakeeper® User Coordinate System and view Windows are the same as for Maxsurf®

69

3.12 Wave direction is measured relative to the vessel track and is given the symbol μ. Thus following waves are at μ = 0°; starboard beam seas are 90°; head seas 180° and port beam seas 270°.

70

4.1 Towing Tank and Model Dimensions 75

4.2 Sample of results obtained from DAAS for total resistance of the model for certain speed.

78

4.3 Experiment results for five Froude number before correction

79

5.1 Bodyplan of the Product Tanker 7698 82

5.2 Size surfaces window 83

5.3 Frame of reference window 84

5.4 Finished Section, Buttocks and Waterline plotted in Maxsurf® viewed in Perspective, Profile, Plan and Body

85

5.5 Input data window 86

5.6 Measure hull window 87

5.7 Mappings for model 7698 87

5.8 Input Data window for Vessel Type 88

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5.10 Damping factors window 90

5.11 Environment window 90

5.12 Analysis method window 92

5.13 Graph window showing the added resistances result in Seakeeper®

93

6.1 Program displaying the data for selecting the added mass coefficient and amplitude ratio

97

6.2 The cross section showing the waterlines and the axes of z and y.

98 6.3 The distance y1, y2 and y3 shown from the axis to the

curves.

100

6.4 The breadth y1, y2, y3, y4, y5 and yn at each section from

1, 2, 3, 4, 5… n.

101

6.5 The breadth y1, y2 , y3,y4 at each section at an equal

interval, h.

103

6.6 Example of using Simpson’s first rule and second rule for 9 and 7 ordinates.

104

6.7 An example of an input data created in Notepad based on 7698 Tanker offset data.

108

7.1 Experiment results of Added resistances for five Froude number after correction

113 7.2 Theoretical results from Seakeeper® using Gerritsma and

Beukelman I

114

7.3 Theoretical results from Seakeeper® using Gerritsma and Beukelman II

115

7.4 Theoretical results from Seakeeper® using Salvesen method

116

7.5 Theoretical results using Joosen method 117

7.6 Comparison of experimental and theoretical added resistance at Froude number 0.166

118

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120

121

122

7.11 The wave profile in time histories for wave length 1.688 m and speed 0.9096 m/s

126

7.12 The energy dissipated by ship waves at speed 0.9096 m/s 127

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LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Salient characteristics of waves 8

2.2 Three linear displacements notation, units and position 21 2.3 Three angular rotations notations, units and positions 21

2.4 Three locations for axes for rolls, pitches and yaws 22

3.1 Model no. 7698 Main Particulars 44

6.8 Comparison result between FORTRAN 77 and Microsoft Excel.

105

7.1 Corrected Froude number 113

8.1 Percentage difference of added resistance value between experimental and theoretical

133

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LIST OF NOMENCLATURE

Symbols

yy

A - Coefficient of added mass moment of inertia for pitching

motion

a - Virtual mass, or virtual mass moment of inertia

z

a - Added mass for heaving

B

- Coefficient of pitch damping moment

n

B - Waterline breadth for nth section

b - Coefficient for damping force or damping moment

n

b - Damping coefficient per unit length

C - Coefficient for pitch restoring moment

c - Coefficient for restoring force or restoring moment

E - Wave energy per unit area of free surface

w

h - Height of wave

yy

I - Mass moment of inertia for pitching

k - Wave number

yy

k - Radius of gyration for pitching

LBP - Length between perpendiculars

w

L - Wavelength from crest to crest

s

L - Length of ship equivalent to LBP

AW

R - Mean resistance increase in waves, that is, resistance in

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e

T - Period of encounter

w

T - Wave period

z

T - Natural period (in smooth water) for heaving θ

T - Natural period (in smooth water) for pitching

φ

T - Natural period (in smooth water) for rolling

u - Horizontal component of water velocity vertical component

of water velocity w

V - Wave velocity or celerity

z - Heaving motion

a

z - Heaving amplitude

β - Sectional area coefficient

ε - Phase angle between motions and waves

1

ε - Phase angle between wave motion and exciting force (or

moment) 2

ε - Phase angle between exciting force (or moment) and motions

ζ - Instantaneuous wave elevation

a

ζ - Wave amplitude

a

ζ - Apparent wave amplitude

θ - Pitch angle

a

θ - Pitch amplitude

μ _- _{Heading angle}

e

ω - Frequency of encounter

w

ω - Wave frequency

z

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LIST OF APPENDICES

APPENDIX TITLE PAGE

A Resistance test results obtained from DAAS 138

B Resistance Test Summary Tables 164

C Offsets and Input data 169

D Program Strip Theory Flow Charts 171

E Wave data, Added Mass Coefficient and Amplitude Ratio Input Data

189

F Added mass coefficients for two-dimensional floating bodies in heaving motion

192

G _{Amplitude ratios}A for two-dimensional floating bodies in heaving motion

194

H Program ‘STRIP THEORY’ Result 196

I Program ‘STRIP THEORY’ Source Codes 205

J Photo shots during model test 228

K Wave surface profile time histories 236

L Table of wave amplitude averages 289

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N Mathematical formulation used in the program – an example on Coupled heaving and pitching motion calculations in regular waves using strip theory.

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INTRODUCTION

1.0 Background of Study

Added resistance in waves is another component of ship’s resistance. It is

sometimes being misunderstood as wave making resistance. Basically, added resistance

in waves is another partial component of the resistance that responsible for speed

reduction in a seaway especially in high seas condition. Therefore added resistance

prediction represents an important challenge for ship-owners due to its economic

implications in terms of choice of engines, fuel consumption and route-time evaluation.

Design offices should consider seriously this problem already in the early stages of the

design.

Usually, the performance evaluation of a ship in a seaway is primary based on the calm

water resistance without properly considering the weather conditions prevailing on the

operating route. Even if the calm water resistance is used as a first estimation of the

power required, an allowance is added to this value of the resistance to consider the

effect of the environment. Therefore in this study it is aim to look into the comparison of

the various theoretical method with the towing tests method as a continuous effort from

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In carrying out these experimental and theoretical predictions, several issues will

be addressed as follow:

i. What is the influence of the ship speeds and the wave frequencies on the

added resistances in waves?

ii. How accurate is the present method of theoretical prediction of added

resistance in waves? Is it reliable?

iii. What is the relationship of ship generated waves to the added resistance in

waves? If there is any, can we use this relationship to predict the added

resistance in waves?

3.0 Objectives of the research

The research work is carried out in order to achieve the following objectives:

i. To evaluate the difference and accuracy of added resistance prediction of a 100

m product tanker between theoretical and model experiment.

ii. Develop a computer program in order to calculate the added resistances in waves

using FORTRAN 77.

iii. Investigate the influences of the following parameters to added resistance due to

waves either from the speed of the vessel and the also the wave frequencies

(wave length)

iv. Investigate the relationship of ship generated waves with the added resistance in

waves as ship dissipates energy to the waves created by it at aft and energy is

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be used as to compare the results obtained experimentally and validate the

computed results.

4.0 Scopes of the research

The scope of the research is listed as follows:

i. Conduct literature research on ship added resistances due to head waves mainly

on the familiarization on the Strip Method and Potential Flow Theory.

ii. Develop a computer program to calculate the ship added resistance in waves

using strip theory to generate the hydrodynamic coefficients, ship’s heave and

pitch motion and using momentum and energy method or radiated energy

method in order to get the added resistance values.

iii. Conduct experiments using the tanker model in a towing tank for calm water

resistance test.

iv. Conduct experiments using the tanker model in a towing tank in regular waves.

v. Determine added resistance due to waves by subtracting resistance in waves to

the resistance in calm water

vi. Familiarization of Maxsurf software namely Maxsurf Pro® for inputs of

linesplan and hulls particulars and Seakeeper® for predicting added resistances

due to waves.

vii. Estimate added resistance due to waves by using theoretical method using

SEAKEEPER namely Gerritsma and Beukelman’s method and Salvesen’s

method.

viii. Validate the theoretical prediction results with the model experiment test results.

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This topic discusses the approach of the project that has been taken to ensure the

objectives of the project will be achieved. It also presents the project flow chart.

Basically the project begins with deciding the objectives and the scopes. This is done by

having discussion with the project supervisor namely, Ir. Dr. Mohamad Pauzi Abdul

Ghani.

Figure 1.1: Research Project Flow Chart

Calm Water Theoretical Method Literature Review Deciding Objective and Scopes

Estimating Added Resistance in Head Waves

Start

Total Resistance of Model, RT Added Resistance

due to Waves, RAW using strip theory

Salvesen Gerritsma & Beukelman Seakeeper® Subtracting Model Experiments Experiment Apparatus

i. Towing Tank

ii. Towing Carriage iii. Ship Model iv. Resistance Type Probe

Computer program Calculation using momentum and energy method Regular Waves

Total Resistance of Model, RTW

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review are done to select and pinpoint the approach of on how the research to be done.

Basically, as agreed in this research project, there are two approaches in determining the

added resistances of a ship in head wave, which are experimentally and theoretically. In

experiment works, both resistances are taken in calm water and in regular waves, and

concurrently the ship generated waves are taken by using resistance probe.

Theoretically, few methods are chosen to predict the added resistances in head waves,

and here two approach are determined which is using computational software namely

Seakeeper® and also a program will be developed using one of the method in predicting

added resistances in waves.

The flow chart of this research project is available in figure 1.1. The

experimental or theoretical prediction works will be repeated if any discrepancy found