Basic Ship Theory Vol.1 Tupper, Notas de estudo de Engenharia Naval

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Basic Ship Theory

Butterworth-Heinemann Linacre House, Jordan Hill, Oxford OX2 8DP 225 Wildwood Avenue, Woburn, MA 01801- Adivision of Reed Educational and Professional Publishing Ltd

Amember of the Reed Elsevier plc group

First published by Longman Group Limited 1968 Second edition 1976 (in two volumes) Third edition 1983 Fourth edition 1994 Fifth edition 2001

# K.J. Rawson and E.C. Tupper 2001

All rights reserved. No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1P 0LP. Applications for the copyright holder's written permission to reproduce any part of this publication should be addressed to the publishers

British Library Cataloguing in Publication Data Rawson, K.J. (Kenneth John), 1926± Basic ship theory. ± 5th ed. Vol. 1, ch. 1±9: Hydrostatics and strength K.J. Rawson, E.C. Tupper

1. Naval architecture 2. Shipbuilding I. Title II. Tupper, E.C. (Eric Charles), 1928± 623.8^01

Library of Congress Cataloguing in Publication Data Rawson, K.J. Basic ship theory/K.J. Rawson, E.C. Tupper. ± 5th ed. p. cm. Contents: v.1. Hydrostatics and strength ± v.2. Ship dynamics and design. Includes bibliographical references and index. ISBN 0-7506-5396-5 (v.1: alk. paper) ± ISBN 0-7506-5397-3 (v.2: alk. paper)

1. Naval architecture I. Tupper, E.C. II. Title.

VM156 .R37 2001 623.8^0 1±dc21 2001037513

ISBN 0 7506 5396 5

For information on all Butterworth-Heinemann publications visit our website at www.bh.com

Typeset in India at Integra Software Services Pvt Ltd, Pondicherry, India 605005; www.integra-india.com

...............................Introduction

Symbols and nomenclature..............................

.......................................1 Art or science?

......................................... 1.1 Authorities

................................ 2 Some tools

....................................... 2.1 Basic geometric concepts

2.2 Properties of irregular shapes.................................

..........................................2.3 Approximate integration

..........................................2.4 Computers

2.5 Appriximate formulae and rules..............................

.......................................2.6 Statistics

...................................................2.7 Worked examples

........................................2.8 Problems

........................................... 3 Flotation and trim

...................................... 3.1 Flotation

..................................................3.2 Hydrostatic data

...................................................3.3 Worked examples

........................................3.4 Problems

........................... 4 Stability

.............................................. 4.1 Initial stability

...................................................4.2 Complete stability

..................................................4.3 Dynamical stability

...............................................4.4 Stability assessment

........................................4.5 Problems

.................................. 5 Hazards and protection

............................................. 5.1 Flooding and collision

.................................................5.2 Safety of life at sea

...............................................5.3 Other hazards

..................................................9.10 Human factors

.........................................9.11 Problems

................................ Bibliography

........................................Answers to problems

................... Index

Forewordto the ®fth edition

Over the last quarter of the last century there were many changes in the

maritime scene. Ships may now be much larger; their speeds are generally

higher; the crews have become drastically reduced; there are many di€erent

types (including hovercraft, multi-hull designs and so on); much quicker and

more accurate assessments of stability, strength, manoeuvring, motions and

powering are possible using complex computer programs; on-board computer

systems help the operators; ferries carry many more vehicles and passengers;

and so the list goes on. However, the fundamental concepts of naval architec-

ture, which the authors set out when Basic Ship Theory was ®rst published,

remain as valid as ever.

As with many other branches of engineering, quite rapid advances have been

made in ship design, production and operation. Many advances relate to the

e€ectiveness (in terms of money, manpower and time) with which older proced-

ures or methods can be accomplished. This is largely due to the greater

eciency and lower cost of modern computers and proliferation of information

available. Other advances are related to our fundamental understanding of

naval architecture and the environment in which ships operate. These tend to

be associated with the more advanced aspects of the subject: more complex

programs for analysing structures, for example, which are not appropriate to a

basic text book.

The naval architect is a€ected not only by changes in technology but also by

changes in society itself. Fashions change as do the concerns of the public, often

stimulated by the press. Some tragic losses in the last few years of the twentieth

century brought increased public concern for the safety of ships and those

sailing in them, both passengers and crew. It must be recognized, of course,

that increased safety usually means more cost so that a con¯ict between money

and safety is to be expected. In spite of steps taken as a result of these

experiences, there are, sadly, still many losses of ships, some quite large and

some involving signi®cant loss of life. It remains important, therefore, to strive

to improve still further the safety of ships and protection of the environment.

Steady, if somewhat slow, progress is being made by the national and interna-

tional bodies concerned. Public concern for the environment impacts upon ship

design and operation. Thus, tankers must be designed to reduce the risk of oil

spillage and more dangerous cargoes must receive special attention to protect

the public and nature. Respect for the environment including discharges into

the sea is an important aspect of de®ning risk through accident or irresponsible

usage.

A lot of information is now available on the Internet, including results of

much research. Taking the Royal Institution of Naval Architects as an example

xi

Acknowledgements

The authors have deliberately refrained from quoting a large number of refer-

ences. However, we wish to acknowledge the contributions of many practi-

tioners and research workers to our understanding of naval architecture, upon

whose work we have drawn. Many will be well known to any student of

engineering. Those early engineers in the ®eld who set the fundamentals of

the subject, such as Bernoulli, Reynolds, the Froudes, Taylor, Timoshenko,

Southwell and Simpson, are mentioned in the text because their names are

synonymous with sections of naval architecture.

Others have developed our understanding, with more precise and compre-

hensive methods and theories as technology has advanced and the ability to

carry out complex computations improved. Some notable workers are not

quoted as their work has been too advanced for a book of this nature.

We are indebted to a number of organizations which have allowed us to draw

upon their publications, transactions, journals and conference proceedings.

This has enabled us to illustrate and quantify some of the phenomena dis-

cussed. These include the learned societies, such as the Royal Institution of

Naval Architects and the Society of Naval Architects and Marine Engineers;

research establishments, such as the Defence Evaluation and Research Agency,

the Taylor Model Basin, British Maritime Technology and MARIN; the

classi®cation societies; and Government departments such as the Ministry of

Defence and the Department of the Environment, Transport and the Regions;

publications such as those of the International Maritime Organisation and the

International Towing Tank Conferences.

xiii

Introduction

In their young days the authors performed the calculations outlined in this

work manually aided only by slide rule and, luxuriously, calculators. The

arduous nature of such endeavours detracted from the creative aspects and

a€ected the enjoyment of designing ships. Today, while it would be possible,

such prolonged calculation is unthinkable because the chores have been

removed to the care of the computer, which has greatly enriched the design

process by giving time for re¯ection, trial and innovation, allowing the e€ects of

changes to be examined rapidly.

It would be equally nonsensical to plunge into computer manipulation with-

out knowledge of the basic theories, their strengths and limitations, which allow

judgement to be quanti®ed and interactions to be acknowledged. A simple

change in dimensions of an embryo ship, for example, will a€ect ¯otation,

stability, protection, powering, strength, manoeuvring and many sub-systems

within, that a€ect a land architect to much less an extent. For this reason, the

authors have decided to leave computer system design to those quali®ed to

provide such important tools and to ensure that the student recognizes the

fundamental theory on which they are based so that he or she may understand

what consequences the designer's actions will have, as they feel their way

towards the best solution to an owner's economic aims or military demands.

Manipulation of the elements of a ship is greatly strengthened by such a `feel'

and experience provided by personal involvement. Virtually every ship's char-

acteristic and system a€ects every other ship so that some form of holistic

approach is essential.

A crude representation of the process of creating a ship is outlined in the

®gure.

xiv

Economics of trade or Military objective

Volume Hull shape^ Weight

Resistance & Propulsion Dimensions

Safety

Architecture

Structure

Manoeuvring Production Choice of machinery Flotation & stability

Design

In the following notes, the SI system of units is presented brie¯y; a fuller

treatment appears in British Standard 5555. This book is written using SI units.

The SI is a rationalized selection of units in the metric system. It is a coherent

system, i.e. the product or quotient of any two unit quantities in the system is

the unit of the resultant quantity. The basic units are as follows:

Quantity Name of unit Unit symbol

Length metre m Mass kilogramme kg Time second s Electric current ampere A Thermodynamic temperature kelvin K Luminous intensity candela cd Amount of substance mole mol Plane angle radian rad Solid angle steradian sr

Special names have been adopted for some of the derived SI units and these

are listed below together with their unit symbols:

Physical quantity SI unit Unit symbol

Force newton N ˆ kg m=s^2 Work, energy joule J ˆ N m Power watt W ˆ J=s Electric charge coulomb C ˆ A s Electric potential volt V ˆ W=A Electric capacitance farad F ˆ A s=V Electric resistance ohm ˆ V=A Frequency hertz Hz ˆ s^1 Illuminance lux lx ˆ lm=m^2 Self inductance henry H ˆ V s=A Luminous ¯ux lumen lm ˆ cd sr Pressure, stress pascal Pa ˆ N=m^2 megapascal MPa ˆ N=mm^2 Electrical conductance siemens S ˆ 1 = Magnetic ¯ux weber Wb ˆ V s Magnetic ¯ux density tesla T ˆ Wb=m^2

The following two tables list other derived units and the equivalent values of

some UK units, respectively:

Physical quantity SI unit Unit symbol

Area square metre m^2 Volume cubic metre m^3 Density kilogramme per cubic metre kg=m^3 Velocity metre per second m=s Angular velocity radian per second rad=s Acceleration metre per second squared m=s^2

xvixvi IntroductionIntroduction

Angular acceleration radian per second squared rad=s^2 Pressure, stress newton per square metre N=m^2 Surface tension newton per metre N=m Dynamic viscosity newton second per metre squared N s=m 2 Kinematic viscosity metre squared per second m 2 =s Thermal conductivity watt per metre kelvin W=(mK)

Quantity Imperial unit Equivalent SI units

Length 1 yd 0.9144 m 1 ft 0.3048 m 1 in 0.0254 m 1 mile 1609.344 m 1 nautical mile (UK)

1853.18 m

1 nautical mile (International)

1852 m

Area 1 in^2 645 : 16  10 ^6 m^2 1 ft^2 0 :092903 m^2 1 yd^2 0 :836127 m^2 1 mile 2 2 : 58999  106 m^2

Volume 1 in^3 16 : 3871  10 ^6 m 3 1 ft^3 0 :0283168 m 3 1 UK gal 0 :004546092 m 3 ˆ 4 :546092 litres

Velocity 1 ft=s 0 :3048 m=s 1 mile=hr 0 :44704 m=s ; 1:60934 km=hr 1 knot (UK) 0 :51477 m=s ; 1:85318 km=hr 1 knot (International) 0 :51444 m=s ; 1:852 km=hr

Standard acceleration, g 32 :174 ft=s^2 9 :80665 m=s^2 Mass 1 lb 0 :45359237 kg 1 ton 1016 :05 kg ˆ 1 :01605 tonnes

Mass density 1 lb=in^3 27 : 6799  103 kg=m 3 1 lb=ft^3 16 :0185 kg=m^3

Force 1 pdl 0.138255 N 1 lbf 4.44822 N

Pressure 1 lbf=in 2 6894 :76 N=m 2 0 :0689476 bars

Stress 1 tonf=in^2 15 : 4443  106 N=m^2 15 :443 MPa or N=mm^2

Energy 1 ft pdl 0.0421401 J 1 ft lbf 1.35582 J 1 cal 4.1868 J 1 Btu 1055.06 J

Power 1 hp 745.700 W

Temperature 1 Rankine unit 5 =9 Kelvin unit 1 Fahrenheit unit 5 =9 Celsius unit

Note that, while multiples of the denominators are preferred, the engineering

industry has generally adopted N=mm 2 for stress instead of MN=m 2 which has,

of course, the same numerical value and are the same as MPa.

Introduction xvii

Of particular signi®cance to the naval architect are the units used for dis-

placement, density and stress. The force displacement , under the SI scheme

must be expressed in terms of newtons. In practice the meganewton (MN) is a

more convenient unit and 1 MN is approximately equivalent to 100 tonf (100.

more exactly). The authors have additionally introduced the tonnef (and,

correspondingly, the tonne for mass measurement) as explained more fully in

Chapter 3.

EXAMPL ES

A number of worked examples has been included in the text of most chapters to

illustrate the application of the principles enunciated therein. Some are rela-

tively short but others involve lengthy computations. They have been deliber-

ately chosen to help educate the student in the subject of naval architecture, and

the authors have not been unduly in¯uenced by the thought that examination

questions often involve about 30 minutes' work.

In the problems set at the end of each chapter, the aim has been adequately to

cover the subject matter, avoiding, as far as possible, examples involving mere

arithmetic substitution in standard formulae.

REFERENCES AND T HE INTERNET

References for each chapter are given in a Bibliography at the end of each

volume with a list of works for general reading. Because a lot of useful

information is to be found these days on the Internet, some relevant web sites

are quoted at the end of the Bibliography.

Introduction xix

Symbols andnomenclature

GENERAL

a linear acceleration A area in general B breadth in general D, d diameter in general E energy in general F force in general g acceleration due to gravity h depth or pressure head in general hw , w height of wave, crest to trough H total head, Bernoulli L length in general Lw ,  wave-length m mass n rate of revolution p pressure intensity pv vapour pressure of water p 1 ambient pressure at in®nity P power in general q stagnation pressure Q rate of ¯ow r, R radius in general s length along path t time in general t^ temperature in general T period of time for a complete cycle u reciprocal weight density, speci®c volume, u, v, w velocity components in direction of x-, y-, z-axes U, V linear velocity w weight density W weight in general x, y, z body axes and Cartesian co-ordinates Right-hand system ®xed in the body, z-axis vertically down, x-axis forward. Origin at c.g. x 0 , y 0 , z 0 ®xed axes Right-hand orthogonal system nominally ®xed in space, z 0 -axis vertically down, x 0 -axis in the general direction of the initial motion. angular acceleration speci®c gravity  circulation  thickness of boundary layer in general  angle of pitch  coecient of dynamic viscosity  coecient of kinematic viscosity  mass density  angle of roll, heel or list  angle of yaw ! angular velocity or circular frequency r volume in general

xx

PD delivered power at propeller PE e€ective power PI indicated power PS shaft power PT thrust power Q torque R resistance in general Rn Reynolds number RF frictional resistance RR residuary resistance RT total resistance RW wave-making resistance sA apparent slip ratio t thrust deduction fraction T thrust U velocity of a ¯uid U 1 velocity of an undisturbed ¯ow V speed of ship VA speed of advance of propeller w Taylor wake fraction in general wF Froude wake fraction Wn Weber number appendage scale e€ect factor advance angle of a propeller blade section  Taylor's advance coe€.  eciency in general B propeller eciency behind ship D quasi propulsive coecient H hull e€. O propeller e€. in open water R relative rotative eciency  cavitation number

SEAKEE PING

c wave velocity f frequency fE frequency of encounter Ixx, Iyy, Izz real moments of inertia Ixy, Ixz, Iyz real products of inertia k radius of gyration mn spectrum moment where n is an integer ML horizontal wave bending moment MT torsional wave bending moment MV vertical wave bending moment s relative vertical motion of bow with respect to wave surface S (!), S(!), etc. one-dimensional spectral density S (!,), S(!,), two-dimensional spectral etc. density T wave period TE period of encounter Tz natural period in smooth water for heaving T natural period in smooth water for pitching T natural period in smooth water for rolling Y (!) response amplitude operatorÐpitch Y (!) response amplitude operatorÐroll Y (!) response amplitude operatorÐyaw leeway or drift angle R rudder angle " phase angle between any two harmonic motions  instantaneous wave elevation

xxii Symbols and nomenclature

A wave amplitude w wave height, crest to trough  pitch angle A pitch amplitude  wave number !E frequency of encounter  tuning factor

MANOEUVRABILITY

AC area under cut-up AR area of rudder b span of hydrofoil c chord of hydrofoil K, M, N moment components on body relative to body axes O origin of body axes p, q, r components of angular velocity relative to body axes X, Y, Z force components on body angle of attack drift angle R rudder angle  heading angle !C steady rate of turn

STRENGTH

a length of plate b breadth of plate C modulus of rigidity " linear strain E modulus of elasticity, Young's modulus  direct stress y yield stress g acceleration due to gravity I planar second moment of area J polar second moment of area j stress concentration factor k radius of gyration K bulk modulus l length of member L length M bending moment Mp plastic moment MAB bending moment at A in member AB m mass P direct load, externally applied PE Euler collapse load p distributed direct load (area distribution), pressure p^0 distributed direct load (line distribution)  shear stress r radius S internal shear force s distance along a curve T applied torque t thickness, time U strain energy W weight, external load y lever in bending  de¯ection, permanent set, elemental (when associated with element of breadth, e.g. b)  mass density v Poisson's ratio  slope

Symbols and nomenclature xxiii