Principles Of Naval Architecture Vol II - Resistance, Propulsion and Vibration

Principles Of Naval Architecture Vol II - Resistance, Propulsion and Vibration

(Parte 1 de 10)

Principles of Naval Architecture

Second Revision

Volume 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 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. 8-60829

Printed in the United States of America First Printing, November, 1988

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 1, 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 W, whereor to buoyancy forces. When conventional or English units are used, displacement weight is in the familiar long ton unit (2240

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 I considers stability in normal intact conditions, while Chapter II 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 I Chapter VI, Motions in Waves.

For Volume I 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 VI, Vibration, which is the third in Volume I, has been almost completely rewritten to take advantage of new developments in the field.

May 1988 EDWARD V. LEWIS Editor

Table of Contents Volume I

Preface3
Acknowledgments10
CHAPTERV

Resistance J. D. van Manen P. van Oossanen

Section 11
Introduction1
1.1 The Pro blem1
1.2 Types of Resistance12
1.3 Submerged Bodies12
1.4 Surface Ships13
Section 213
Dimensional Analysis13
2.1 Genera l13
2.2 Dimensional Homogeneity14
2.3 Corresponding Speeds15
2.4 Extensio n of Mode l Results to Ship17
Section 317
Frictional Resistance17
3.1 General17
3.2 Froude's17
3.3 Two-dimensional Frictional Resistance Formulations18
3.4 Development of Frictional Resistance Formulations20
3.5 The Work of the Towing Tank Conferences2
Section 425
Wave-Making Resistance25
4.1 General25
4.2 Ship Wave Sys tems25
4.3 Wave-Making Resi stance of Surface Ships27
4.4 Theoretical Calculation of Wave-Making Resistance29
4.5 Interference Effects32
4.6 Effects of Viscosity on Wave-Making Resistance34
4.7 Scale Effect on Wave-Making Resistance36
Section 537
Other Components of Resistance37
5.2 Air and Wind Resistance39
5.3 Added Resistance due to Waves4
5.4 Appendage Resistance4
5.5 Trim Effects51
5.6 Shallow-Water Effects52

5.1 Eddy Resistance, Viscous Pressure Drag, Separation Resistance and Wave-breaking Resistance.37 5.7 Resistance increase due to leeway and heel, with................................................................................60

The Uses of Models for Determining Ship Resistance63
6.1 Historical63
6.2 Modern Facilities63
6.3 Model Testing Techniques64
6.4 Calculation of Effective Power67
Section 772
Methods of Presenting Model Resistance Data72
7.1 General72
7.2 The CTRn Presenta tion72
7.3 Design Presentations72
7. 4 TheSystem73
7.5 The R / W vs. Fn or Rw /W vs. Fn system73
7.6 The RT/W vs. Fn Sy stem73
7.7 Conversion Factor for Speed and Resistance Coefficients73
Section 876
Relation of Hull Form to Resistance76
8.1 Choice of Ship Dimensions76
8.2 Choice of Form Coefficients7
8.3 Design Data81
8.4 Model Resistance Data Sheets81
8.5 Methodical Series Experiments81
8.6 Taylor’s Standards Series81
8.7 Series 6084
8.8 Other Methodical Series of Merchant Ship Models87
8.9 Bodies of Revolution, Deeply-Submerged (Submarines)8
8.10 Effect of Bulbous Bows on Resistance89
8.1 Cylindricaland Elliptical Bows.................................................................................................96
8.12 Statistical Analysis of Model Data98
Section 9103
High-Speed Craft and Advanced Marine Vehicles103
9.1 Round-Bilge Semi-Displacement Craft104
9.2 Plan ing Craft109
9.3 Catamarans115
9.4 Small W aterplane Area118
9.5 Hydrofoil Craft120
9.6 Air-Supp orted Craft126
References128

Propulsion J. D. van Manen P. van Oossanen

Section 1136
Powering of Ships136
1.1 His torical136
1.2 Types of Ship Machinery137
1.3 Definition of Power138
Theory of Propeller Action140
2.1 Momentum Principle140
2.2 General Discussion of Propeller140
2.3 The Momentum Theory of Propeller Action141
2.4 The Momentum Theory142
2.5 Blade Element Theory of Screw Propeller144
2.6 Circula tion Theory o f Screw Prope ller150
Section 3152
Law of Similitude for Propellers152
3.1 Dimensional analysis152
3.2 Open water tests154
Section 4154
Interaction Between Hull and Propeller154
4.1 Genera l154
4.2 Wake154
4.3 Real and Apparent Slip Ratio160
4.4 Relative Rotative Efficiency160
4.5 Augment of Resistance and Thrust Deduction161
4.6 Hull Efficiency161
Section 5162
Model Self-Propulsion Tests162
5.1 Methods of Conductin g Experimen ts162
5.2 Standard Procedures for Performance Predictions164
5.3 Values of Wake167
Section 6173
Geometry of the Screw Propeller173
6.1 General Characteristics173
6.2 Geometry of Helix173
6.3 Propeller Drawing174
6.4 Constructional Details of Marine Propellers176
Section 7180
Cavitation180
7.1 The Nature of Cavitation180
7.2 Types of Cavitation182
7.3 Law of Similitude for Cavitating Propellers184
7.4 Cavitation Tests With Model Propellers185
7.5 Presentation of Data187
7.6 Detrimental effects of cavitation187
7.7 Criteria for Prevention of Cavitation190
Section 8192
Propeller Design192
8.1 Methods of Propeller Design192
8.2 General Propeller Design Philosophy192
8.3 Propeller Design From Methodical Series Charts195
8.4 Application of Circulation Theory to Propeller Design213
8.5 Service Power Allowances221
Section 92
9.2 Accelerating nozzles224
9.3 De celerating nozzle s230
Section 10234
Other Propulsion Devices234
10.1 General234
10.2 Jet Propulsion234
10. 3 Pump Jets237
10. 4 Paddle Wheels237
10.5 Vertical-Axis Propellers237
10.6 Controllable-Pitch Propellers239
10.7 Tandem and Con trarotating Propellers240
10.8 Super-Cavitating Propellers242
10.9 Overlapping propellers246
10.9 Overlapping propellers246
10.10 Partially Submerged Propeller247
10.1 Other Devices247
Section 1249
Ship Standardization Trials249
1.1Purpose of Trials ........................................................................................................................... 249
1.2 General Plan of Trials249
1.3 Measurement of Speed250
1.4 Analysis of Speed Trials253

Vibration William S. Vorus

Section 1264
Introduction264
1.1 Genera l264
1.2 Basic Definitions265
Section 2266
Theory and Concepts266
2.1 Continuous Analysis266
2.2 Discrete Analysis274
2.3 Propeller Exciting Forces280
Section 3288
Analysis and Design288
3.1 Introduction288
3.2 Approximate Evaluation of Hull Girder Natural Frequencies291
3.3 Hydrodynamic Added Mass293
3.4 Approximate Evaluation of Superstructure Natural Frequencies295
3.5 Main Thrust Bearing Foundation Stiffness297
3.6 Diesel Engine Excitation298
3.7 Propeller Excitation300
Section 4315
Criteria, Measurements, and Post-Trial Corrections315
4.1 Criteria of Acceptable Vibration315
4.2 Vibration Measurement317
Volume I Nomenclature326
Resist ance, propulsion a nd vibrat ion326
Vibration Symbol Subscripts327
Greek Symb ols327
Special Symbols328
Froude's "Circle" Notation328
Vibration Symbols328
Mathematical S ymbols328
Internati onal System of Units329

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 E. V. LEWIS Editor

J. D. van Manen P. van Oossanen Resistance

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-I 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 500,0 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

1Complete 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 VI, Vol. I. 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 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. I. 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

PE = RTV (la) where PE = effective power in kWatt (kW)

RT = total resistance in kNewton (kN) V = speed in m / sec

orehp = RTVk/S26 (1b)

where ehp = effective power in English horsepower

RT = total resistance in lb Vk = speed in knots

To convert from horsepower to S.I. units there is only a slight difference between English and metric horsepower:

hp (English) x 0.746 = kW hp (metric) X 0.735 = kW Speed in knots x 0.5144 = m/sec

This total resistance is made up of a number of different components, which are caused by a variety of factors and which interact one with the other in an extremely complicated way. In order to deal with the question more simply, it is usual to consider the total calm water resistance as being made up of four main components. (a) The frictional resistance, due to the motion of the hull through a viscous fluid. (b) The wave-making resistance, due to the energy that must be supplied continuously by the ship to the wave system created on the surface of the water. (c) Eddy resistance, due to the energy carried away by eddies shed from the hull or appendages. Local eddying will occur behind appendages such as boss- ings, shafts and shaft struts, and from stern frames and rudders if these items are not properly streamlined and aligned with the flow. Also, if the after end of the ship is too blunt, the water may be unable to follow the curvature and will break away from the hull, again giving rise to eddies and separation resistance. (d) Air resistance experienced by the above-water part of the main hull and the superstructures due to the motion of the ship through the air.

The resistances under (b) and (c) are commonly taken together under the name residuary resistance. Further analysis of the resistance has led to the identification of other sub-components, as discussed subsequently.

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 immersed in an unlimited ocean, presents the simplest case of resistance. Since there is no free surface, there is no wave formation and therefore no wave-making resistance. If in addition the fluid is assumed to be without viscosity (a "perfect" fluid), there will be no frictional or eddymaking resistance. The pressure distribution around such a body can be determined theoretically from considerations of the potential flow and has the general characteristics shown in Fig. l(a).

Near the nose, the pressure is increased above the 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, by Bernoulli's Law, will be the inverse of the pressure distribution—along the midportion it will be greater than the speed of advance V and in the region of bow and stern it will be less.

(Parte 1 de 10)

Comentários