Principles of Naval Architecture Second Revision Volume II @BULLET Resistance, Propulsion and Vibration PDF

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P r in c ip le s of N a v a l A r c h ite c tu r e S e c o n d R e v is io n Volume I I • Resistance, Propulsion and Vibration Edward V. Lewis, Editor Published by The Society of Naval Architects and Marine Engineers 601 Pavonia Avenue Jersey City, NJ Copyright @ 1988 by The Society of Naval Archite...

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Principles of Naval Architecture Second Revision

Volume II • Resistance, Propulsion and Vibration

Edward V. Lewis, Editor

Published by The Society of Naval Architects and Marine Engineers 601 Pavonia Avenue Jersey City, NJ

Copyright @ 1988 by The Society of Naval Architects

and Marine Engineers.

It is understood and agreed that nothing expressed herein is intended or shall be construed to give any person, firm, or corporation any right, remedy, or claim against SNAME or any of its officers or members.

Library of Congress Catalog Card No. 88-60829 ISBN No. 0-939773-01-5 Printed in the United States of America . First Printing, November, 1988

ii

Preface The aim of this second revision (third edition) of the Society's successful Principles of Naval Architecture was to bring the subject matter up-to-date through revising or rewriting areas of greatest recent technical advances, which meant that some chapters would require many more changes than others. The basic objective of the book, however, remained unchanged: to provide a timely survey of the basic principles in the field of naval architecture for the use of both students and active professionals, making clear that research and engineering are continuing in almost all branches of the subject. References are to be included to available sources of additional details and to ongoing work to be followed in the future. The preparation of this third edition was simplified by an earlier decision to incorporate a number of sections into the companion SNAME publication, Ship Design and Construction, which was revised in 1980. The topics of Load Lines, Tonnage Admeasurement and Launching seemed to be more appropriate for the latter book, and so Chapters V, VI, and XI became IV, V and XVII respectively, in Ship Design and Construction. This left eight chapters, instead of 11, for the revised Principles of Naval Architecture, which has since become nine in three volumes. At the outset of work on the revision, the Control Committee decided that the increasing importance of high-speed computers demanded that their use be discussed in the individual chapters instead of in a separate appendix as before. It was also decided that throughout the book more attention should be given to the rapidly developing advanced marine vehicles. In regard to units of measure, it was decided that the basic policy would be to use the International System of Units (S.I.). Since this is a transition period, conventional U.S. (or "English") units would be given in parentheses, where practical, throughout the book. This follows the practice adopted for the Society's companion volume, Ship Design and Construction. The U.S. Metric Conversion Act of 1975 (P.L. 94-168) declared a national policy of increasing the use of metric systems of measurement and established the U.S. Metric Board to coordinate voluntary conversion to S.I. The Maritime Administration, assisted by a SNAME ad hoc task group, developed a Metric Practice Guide to "help obtain uniform metric practice in the marine industry," and this guide was used here as a basic reference. Following this guide, ship displacement in metric tons (1000 kg) represents mass rather than weight, (In this book the familiar symbol, A, is reserved for the displacement mass). When forces are considered, the corresponding unit is the kilonewton (kN), which applies, for example, to resistance and to displacement weight (symbol ~ where W = pAg) or to buoyancy forces. When conventional or English units are used, displacement weight is in the familiar long ton unit (2240

(Continued) Hi

PREFACE

lb), which numerically is 1.015 X metric ton. Power is usually in kilowatts (1 kW = 1.34 hp). A conversion table also is included in the Nomenclature at the end of each volume The first volume of the third edition of Principles of Naval Architecture, comprising Chapters I through IV, covers almost the same subject matter as the first four chapters of the preceding edition. Thus, it deals with the essentially static principles of naval architecture, leaving dynamic aspects to the remaining volumes. Chapter I deals with the graphical and numerical description of hull forms and the calculations needed to deal with problems of flotation and stability that follow. Chapter II considers stability in normal intact conditions, while Chapter III discusses flotation and stability in damaged conditions. Finally, Chapter IV deals with principles of hull structural design, first under static calm water conditions, and then introducing the effect of waves which also are covered more fully in Volume III Chapter VIII, Motions in Waves. For Volume II it seemed desirable, on the basis of subject matter and space requirements, to include Chapter V, Resistance, Chapter VI, Propulsion and Chapter VII, Vibration. The first two of these were covered in a single chapter in the preceding edition. The new chapters have been extensively revised, with considerable new material, particularly dealing with high performance craft and new propulsion devices. Chapter VII, Vibration, which is the third in Volume II, has been almost completely rewritten to take advantage of new developments in the field. May 1988

EDWARD

V.

LEWIS

Editor

iv

Table of Contents Volume II Preface ....................................

Chapter 5

Page iii

Acknowledgments ..........................

RESISTANCE

J.D. VAN MANENand P. VAN OOSSANEN,Netherlands Netherlands 1 1. Introduction ........................... 2. Dimensional Analysis ....... , .......... 5 7 3. Frictional Resistance .................. 15 4. Wave-making Resistance .............. 27 5. Other Components of Resistance ......

Chapter 6

Maritime Research Institute, Wageningen, The Uses of Models........................ Presenting Model Resistance Data .... Relation of Hull Form to Resistance .. Advanced Marine Vehicles ............

53 62 66 93

Maritime Resarch Institute,

Wageningen,

The

6. 7. 8. 9. 10. 11.

Geometry of the Screw Propeller ..... Cavitation ............................. Propeller Desi~ ...................... Ducted Propel ers ..................... Other Pro£ulsion Devices ............. Ship Stan ardization Trials ............

164 171 183 213 225 240

4.

Criteria, Measurement, Post Trial Correction ...........................

306

VIBRATION

WILLIAMS. VORUS,Professor, University of Michigan 1. Introduction ........................... 255 2. Theory and Concepts .................. 257 3. Analysis and Design................... 279 Nomenclature ................................... Index ............................................

6. 7. 8. 9.

PROPULSION

J.D. VAN MANEN and P. VAN OOSSANEN,Netherlands Netherlands 127 1. Powering of Shi~s ..................... 131 2. Theory of Prope ler Action ............ 143 3. Law of Similitude for Propellers ...... 4. Interaction Between Hull and 145 Proreller ....... : .................... 153 5. Mode Self-propulsIon Tests ...........

Chapter 7

Page vi

317 322

v

Acknowledgments The authors of Chapters V and VI, J.D. van Manen and P. van Oossanen, wish to acknowledge their indebtedness to the author of Chapter V in the preceding edition, Frederick H. Todd. Extensive use has been made of the original text and figures. The authors also wish to recognize the assistance provided by U. Nienhuis of the Maritime Institute Netherlands in working through the entire text a second time, making additions and corrections whenever necessary. And valuable ideas and suggestions regarding high-speed displacement and planing hulls in Section 9 of Chapter V were provided by Daniel Savitsky, Director of the Davidson Laboratory and are acknowledged with thanks. The author of Chapter VII, William S. Vorus, expresses his appreciation of the pioneering work of Frank M. Lewis, as distilled in Chapter X of the preceding edition of this book, which provided a foundation for the new chapter. He appreciates the reveiw and comments on early drafts by Edward F. Noonan, of NFK Engineering Associates, Inc., and John P. Breslin of Stevens Institute of Technology. The Control Committee provided essential guidance, as well as valuable assistance in the early stages. Members are: John J. Nachtsheim, Chairman Thomas M. Buermann William A. Cleary, Jr. Richard B. Couch Jerome L. Goldman Jacques B. Hadler Ronald K. Kiss Donald P. Roseman Stanley G. Stiansen Charles Zeien Finally, the Editor wishes to thank all of the authors for their fine work and for their full cooperation in making suggested revisions. He acknowledges the indispensible efforts of Trevor Lewis-Jones in doing detailed editing and preparing text and figures in proper format for publication. May 1988

vi

E. V. LEWIS Editor

CHAPTER

J. D. van Manen P. van Oossanen

I

V

Res·.stance

Section 1 Introduction 1.1 The Problem. A ship differs from any other large engineering structure in that-in addition to all its other functions-it must be designed to move efficiently through the water with a minimun of external assistance. In Chapters I-III of VoL I it has been shown how the naval architect can ensure adequate buoyancy and stability for a ship, even if damaged by collision, grounding, or other cause. In Chapter IV the problem of providing adequate structure for the support of the ship and its contents, both in calm water and rough seas, was discussed. In this chapter we are concerned with how to make it possible for a structure displacing up to 500,000 tonnes or more to move efficiently across any of the world's oceans in both good and bad weather. The problem of moving the ship involves the proportions and shape-or form-of the hull, the size and type of propulsion plant to provide motive power, and the device or system to transform the power into effective thrust. The design of power plants is beyond the scope of this1 book (see Marine Engineering, by R.L. Harrington, Ed., SNAME 1971). The nine sections of this chapter will deal in some detail with the relationship between hull form and resistance to forward motion (or drag). Chapter VI discusses propulsion devices and their interaction with flow around the hull. The task of the naval architect is to ensure that, within the limits of other design requirements, the hull form and propulsion arrangement will be the most efficient in the hydrodynamic sense. The ultimate test is that the ship shall perform at the required speed with the minimum of shaft power, and the problem is to attain the best combination of low resistance and high propulsive efficiency. In general this can only be attained by a proper matching of hull and propeller. Another factor that influences the hydrodynamic design of a ship is the need to ensure not only good

1

Complete references are listed at end of chapter.

smooth-water performance but also that under average service conditions at sea the ship shall not suffer from excessive motions, wetness of decks, or lose more speed than necessary in bad weather. The assumption that a hull form that is optimum in calm water will also be optimum in rough seas is not necessarily valid. Recent research progress in oceanography and the seakeeping qualities of ships has made it possible to predict the relative performance of designs of varying hull proportions and form under different realistic sea conditions, using both model test and computing techniques. The problem of ship motions, attainable speed and added power requirements in waves are discussed in Chapter VIII, VoL III. This chapter is concerned essentially with designing for good smooth-water performance. Another consideration in powering is the effect of deterioration in hull surface condition in service as the result of fouling and corrosion and of propeller roughness on resistance and propulsion. This subject is discussed in this chapter. As in the case of stability, subdivision, and structure, criteria are needed in design for determining acceptable levels of powering. In general, the basic contractual obligation laid on the shipbuilder is that the ship shall achieve a certain speed with a specified power in good weather on trial, and for this reason smoothwater performance is of great importance. As previously noted, good sea performance, particularly the maintenance of sea speed, is often a more important requirement, but one that is much more difficult to define. The effect of sea condition is customarily allowed for by the provision of a service power margin above the power required in smooth water, an allowance which depends on the type of ship and the average weather on the sea routes on which the ship is designed to operate. The determination of this service allowance depends on the accumulation of sea-performance data on similar ships in similar trades. Powering criteria in the form of conventional service allowances for both

2

PRINCIPLES

OF NAVAL

sea conditions and surface deterioration are considered in this chapter. The problem of controlling and maneuvering the ship will be covered in Chapter IX, Vol. III. 1.2 Types of Resistance. The resistance of a ship at a given speed is the force required to tow the ship at that speed in smooth water, assuming no interference from the towing ship. If the hull has no appendages, this is called the bare-hull resistance. The power necessary to overcome this resistance is called the towrope or effective power and is given by P _ R V (1) E T a where PE = effective power in kWatt (kW) RT = total resistance in kNewton (kN) V = speed in m / sec

ARCHITECTURE

The importance of the different components depends upon the particular conditions of a design, and much of the skill of naval architects lies in their ability to choose the shape and proportions of hull which will result in a combination leading to the minimum total power, compatible with other design constraints. In this task, knowledge derived from resistance and propulsion tests on small-scale models in a model basin or towing tank will be used. The details of such tests, and the way the results are applied to the ship will be described in a later section. Much of our knowledge of ship resistance has been learned from such tests, and it is virtually impossible to discuss the various types of ship resistance without reference to model work. 1.3 Submerged Bodies. A streamlined body moving in a straight horizontal line at constant speed, deeply or ehp = RT Vk / 326 (lb) immersed in an unlimited ocean, presents the simplest where ehp = effective power in English horsepower case of resistance. Since there is no free surface, there Rr = total resistance in lb is no wave formation and therefore no wave-making Vk = speed in knots resistance. If in addition the fluid is assumed to be .. without viscosity (a "perfect" fluid), there will be no To conyert f~om horsepower to SJ .. umts there ~s frictional or eddymaking resistance. The pressure disonly a slIght dIfference between EnglIsh and metrIc tribution around such a body can be determined thehorsepower: oretically from considerations of the potential flow and hp (English) X 0.746 = kW has the general characteristics shown in Fig. l(a). hp (metric) X 0.735 = kW Near t~e nose, the pressure is .increased above the Speed in knots X 0.5144 = m / sec hydrostatIc pressure, along the mIddle of the body the pressure is decreased below it and at the stern it is . again increased. The velocity distribution past the hull, This total resistance is made up of a number of by Bernoulli's Law, will be the inverse of the pressure different components, which are caused by a variety distribution-along the midportion it will be greater of factors and which interact one with the other in an than the speed of advance V and in the region of bow extremely complicated way. In order to deal with the and stern it will be less. question more simply, it is usual to consider the total Since the fluid has been assumed to be without viscalm water resistance as being made up of four main cosity, the pressure forces will everywhere be normal components .. to the hull (Fig. l(b)). Over the forward part of the (a) The frictional resistance, due to the motion of hull, these will have components acting towards the the hull through a viscous fluid. stern and therefore resisting the motion. Over the (b) The wave-making resistance, due to the energy after part, the reverse is the case, and these compothat must be supplied continuously by the ship to the nents are assisting the motion. It can be shown that wave system created on the surface of the water. the resultant total forces on the fore and after bodies (c) Eddy resistance, due to the energy carried away are equal, and the body therefore experiences no reby eddies shed from the hull or appendages. Local sistance.2 eddying will occur behind appendages such as bossIn a real fluid the boundary layer alters the virtual ings, shafts and shaft struts, and from stern frames shape and length of the stern, the pressure distribution and rudders if these items are not properly streamlined there is changed and its forward component is reduced. and aligned with the flow. Also, if the after end of the The pressure distribution over the forward portion is ship is too blunt, the water may be unable to follow but little changed from that in a perfect fluid. There the curvature and will break away from the hull, again is therefore a net force on the body acting against the giving rise to eddies and separation resistance. motion, giving rise to a resistance which is variously (d) Air resistance experienced by the above-water referred to as form drag or viscous pressure drag. part of the main hull and the superstructures due to In a real fluid, too, the body experiences friction~l the motion of the ship through the air. resistance and perhaps eddy resistance also. The flUId The resistances under (b) and (c) are commonly immediately in contact with the surface of the body is taken together under the name residuary resistance. Further analysis of the resistance has led to the identification of other sub-components, as discussed subThis was first noted by the French mathematician d' Alembert in sequentIy. 1744, and is known as d'Alembert's paradox. 2

RESISTANCE

3

ually entering undisturbed water and accelerating it to maintain the boundary layer, this represents a continual drain of energy. Indeed, in wind-tunnel work the measurement of the velocities of the fluid behind a streamlined model is a common means of measuring the frictional drag. If the body is rather blunt at the after end, the flow may leave the form at some point-called a separation point-thus reducing the total pressure on the afterbody and adding to the resistance. This separation resistance is evidenced by a pattern of eddies which is a drain of energy (Fig. 1(d). 1.4 Surface Ships. A ship moving on the surface of the sea experiences frictional resistance and eddymaking, separation, and viscous pressure drag in the same way as does the submerged body. However, the presence of the free surface adds a further component. The movement of the hull through the water creates a pressure distribution similar to that around the submerged body; i.e., areas of increased pressure at bow and stern and of decreased pressure over the middle part of the length. But there are important differences in the pressure distribution over the hull of a surface ship because of the surface wave disturbance created by the ship's forward motion. There is a greater pressure acting over the bow, as indicated by the usually prominent bow wave build-up, and the pressure increase at the stern, in and just below the free surface, is always less than around a submerged body....