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# 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

Preface | 3 |

Acknowledgments | 10 |

CHAPTER | V |

Resistance J. D. van Manen P. van Oossanen

Section 1 | 1 |

Introduction | 1 |

1.1 The Pro blem | 1 |

1.2 Types of Resistance | 12 |

1.3 Submerged Bodies | 12 |

1.4 Surface Ships | 13 |

Section 2 | 13 |

Dimensional Analysis | 13 |

2.1 Genera l | 13 |

2.2 Dimensional Homogeneity | 14 |

2.3 Corresponding Speeds | 15 |

2.4 Extensio n of Mode l Results to Ship | 17 |

Section 3 | 17 |

Frictional Resistance | 17 |

3.1 General | 17 |

3.2 Froude's | 17 |

3.3 Two-dimensional Frictional Resistance Formulations | 18 |

3.4 Development of Frictional Resistance Formulations | 20 |

3.5 The Work of the Towing Tank Conferences | 2 |

Section 4 | 25 |

Wave-Making Resistance | 25 |

4.1 General | 25 |

4.2 Ship Wave Sys tems | 25 |

4.3 Wave-Making Resi stance of Surface Ships | 27 |

4.4 Theoretical Calculation of Wave-Making Resistance | 29 |

4.5 Interference Effects | 32 |

4.6 Effects of Viscosity on Wave-Making Resistance | 34 |

4.7 Scale Effect on Wave-Making Resistance | 36 |

Section 5 | 37 |

Other Components of Resistance | 37 |

5.2 Air and Wind Resistance | 39 |

5.3 Added Resistance due to Waves | 4 |

5.4 Appendage Resistance | 4 |

5.5 Trim Effects | 51 |

5.6 Shallow-Water Effects | 52 |

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 Resistance | 63 |

6.1 Historical | 63 |

6.2 Modern Facilities | 63 |

6.3 Model Testing Techniques | 64 |

6.4 Calculation of Effective Power | 67 |

Section 7 | 72 |

Methods of Presenting Model Resistance Data | 72 |

7.1 General | 72 |

7.2 The CTRn Presenta tion | 72 |

7.3 Design Presentations | 72 |

7. 4 TheSystem | 73 |

7.5 The R / W vs. Fn or Rw /W vs. Fn system | 73 |

7.6 The RT/W vs. Fn Sy stem | 73 |

7.7 Conversion Factor for Speed and Resistance Coefficients | 73 |

Section 8 | 76 |

Relation of Hull Form to Resistance | 76 |

8.1 Choice of Ship Dimensions | 76 |

8.2 Choice of Form Coefficients | 7 |

8.3 Design Data | 81 |

8.4 Model Resistance Data Sheets | 81 |

8.5 Methodical Series Experiments | 81 |

8.6 Taylor’s Standards Series | 81 |

8.7 Series 60 | 84 |

8.8 Other Methodical Series of Merchant Ship Models | 87 |

8.9 Bodies of Revolution, Deeply-Submerged (Submarines) | 8 |

8.10 Effect of Bulbous Bows on Resistance | 89 |

8.1 Cylindrical | and Elliptical Bows.................................................................................................96 |

8.12 Statistical Analysis of Model Data | 98 |

Section 9 | 103 |

High-Speed Craft and Advanced Marine Vehicles | 103 |

9.1 Round-Bilge Semi-Displacement Craft | 104 |

9.2 Plan ing Craft | 109 |

9.3 Catamarans | 115 |

9.4 Small W aterplane Area | 118 |

9.5 Hydrofoil Craft | 120 |

9.6 Air-Supp orted Craft | 126 |

References | 128 |

Propulsion J. D. van Manen P. van Oossanen

Section 1 | 136 |

Powering of Ships | 136 |

1.1 His torical | 136 |

1.2 Types of Ship Machinery | 137 |

1.3 Definition of Power | 138 |

Theory of Propeller Action | 140 |

2.1 Momentum Principle | 140 |

2.2 General Discussion of Propeller | 140 |

2.3 The Momentum Theory of Propeller Action | 141 |

2.4 The Momentum Theory | 142 |

2.5 Blade Element Theory of Screw Propeller | 144 |

2.6 Circula tion Theory o f Screw Prope ller | 150 |

Section 3 | 152 |

Law of Similitude for Propellers | 152 |

3.1 Dimensional analysis | 152 |

3.2 Open water tests | 154 |

Section 4 | 154 |

Interaction Between Hull and Propeller | 154 |

4.1 Genera l | 154 |

4.2 Wake | 154 |

4.3 Real and Apparent Slip Ratio | 160 |

4.4 Relative Rotative Efficiency | 160 |

4.5 Augment of Resistance and Thrust Deduction | 161 |

4.6 Hull Efficiency | 161 |

Section 5 | 162 |

Model Self-Propulsion Tests | 162 |

5.1 Methods of Conductin g Experimen ts | 162 |

5.2 Standard Procedures for Performance Predictions | 164 |

5.3 Values of Wake | 167 |

Section 6 | 173 |

Geometry of the Screw Propeller | 173 |

6.1 General Characteristics | 173 |

6.2 Geometry of Helix | 173 |

6.3 Propeller Drawing | 174 |

6.4 Constructional Details of Marine Propellers | 176 |

Section 7 | 180 |

Cavitation | 180 |

7.1 The Nature of Cavitation | 180 |

7.2 Types of Cavitation | 182 |

7.3 Law of Similitude for Cavitating Propellers | 184 |

7.4 Cavitation Tests With Model Propellers | 185 |

7.5 Presentation of Data | 187 |

7.6 Detrimental effects of cavitation | 187 |

7.7 Criteria for Prevention of Cavitation | 190 |

Section 8 | 192 |

Propeller Design | 192 |

8.1 Methods of Propeller Design | 192 |

8.2 General Propeller Design Philosophy | 192 |

8.3 Propeller Design From Methodical Series Charts | 195 |

8.4 Application of Circulation Theory to Propeller Design | 213 |

8.5 Service Power Allowances | 221 |

Section 9 | 2 |

9.2 Accelerating nozzles | 224 |

9.3 De celerating nozzle s | 230 |

Section 10 | 234 |

Other Propulsion Devices | 234 |

10.1 General | 234 |

10.2 Jet Propulsion | 234 |

10. 3 Pump Jets | 237 |

10. 4 Paddle Wheels | 237 |

10.5 Vertical-Axis Propellers | 237 |

10.6 Controllable-Pitch Propellers | 239 |

10.7 Tandem and Con trarotating Propellers | 240 |

10.8 Super-Cavitating Propellers | 242 |

10.9 Overlapping propellers | 246 |

10.9 Overlapping propellers | 246 |

10.10 Partially Submerged Propeller | 247 |

10.1 Other Devices | 247 |

Section 1 | 249 |

Ship Standardization Trials | 249 |

1.1 | Purpose of Trials ........................................................................................................................... 249 |

1.2 General Plan of Trials | 249 |

1.3 Measurement of Speed | 250 |

1.4 Analysis of Speed Trials | 253 |

Vibration William S. Vorus

Section 1 | 264 |

Introduction | 264 |

1.1 Genera l | 264 |

1.2 Basic Definitions | 265 |

Section 2 | 266 |

Theory and Concepts | 266 |

2.1 Continuous Analysis | 266 |

2.2 Discrete Analysis | 274 |

2.3 Propeller Exciting Forces | 280 |

Section 3 | 288 |

Analysis and Design | 288 |

3.1 Introduction | 288 |

3.2 Approximate Evaluation of Hull Girder Natural Frequencies | 291 |

3.3 Hydrodynamic Added Mass | 293 |

3.4 Approximate Evaluation of Superstructure Natural Frequencies | 295 |

3.5 Main Thrust Bearing Foundation Stiffness | 297 |

3.6 Diesel Engine Excitation | 298 |

3.7 Propeller Excitation | 300 |

Section 4 | 315 |

Criteria, Measurements, and Post-Trial Corrections | 315 |

4.1 Criteria of Acceptable Vibration | 315 |

4.2 Vibration Measurement | 317 |

Volume I Nomenclature | 326 |

Resist ance, propulsion a nd vibrat ion | 326 |

Vibration Symbol Subscripts | 327 |

Greek Symb ols | 327 |

Special Symbols | 328 |

Froude's "Circle" Notation | 328 |

Vibration Symbols | 328 |

Mathematical S ymbols | 328 |

Internati onal System of Units | 329 |

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

or | ehp = 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)