Proceedings of the 12th International Towing Tank Conference, ITTC’69

ARCH1EF

OFFICE

OF NAVAL

RESEARCH

BRANCH

OFFICE

LONDON

ENGLAND

THIS REPORT IS ISSUED FOR INFORMATION PURPOSES ON THE UNDERSTANDING THAT IT IS NOT A PART OF THE SCIENTIFIC LITERATURE AND WILL NOT BE CITED ABSTRACTED OR REPRINTED

Lab.

v. Scheepsbouwkunde

Technische Hogeschool

Delft

ONR LONDON CONFERENCE REPORT

C-18-69

UNITED STATES OF AMERICA

HIS DOCUMENT HAS BEEN APPROVED FOR PUBLIC RELEASE AND SALE; ITS DISTRIBUTION IS UNLIMITED.

TWELFTH INTERNATIONAL TOWING TANK CONFERENCE, ROME, ITALY, 22-30 September 1969

By PHILIP MANDEL

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TABLE OF CONTENTS

I. Introduction 1

II. Summary of Contributions to Seakeeping Session 2

Proposed Standards, New Techniques and New

Facilities for Seakeeping Tests 2

Theoretical Prediction of Motions in Waves 5

Characteristics of a Seaway 6

Propulsive Performance in Waves 8

Prediction of Sustained Sea Speed 9

III. Summary of Contributions to Maneuvering Session 12

Definitive Maneuvers 12

Maneuvering in Restricted Waters: Tests,

Theory and Facilities 15

Effect of Wind on Maneuverability 18

Mathematical Simulation of Maneuvers 18

Rudder Hydrodynamics 19

Correlation of Maneuvering Results: Model to

Full Scale, Different Model Techniques,

Different Facilities 19

Appendix A - Number of Written Contributions and Committee Memberships by Nation

and by Committee 21

Appendix B - List of Written Contributions to the

12th ITTC 23

Resistance Committee (II) 23

Performance Committee (III) 25

Propeller Committee (IV) 26

Cavitation Committee (V) 27

Seakeeping Committee (VI) 29

Maneuvering Committee (VII) 30

Presentation Committee (VIII) 32

2.

5%.

1.

-Participating in the Executive Committee or in the Technical Sessions of the

12th ITTC 33

Appendix D Alphabetical List of Contributors

from Japan to the 12th ITTC 42

Additional Foreign Distribution for Report 44

TWELFETH INTERNATIONAL TOWING TANK CONFERENCE, ROME, 23-30 September 1969

I. INTRODUCTION

The Twelfth triennial International Towing Tank Conference (ITTC) was

held at Rome, Italy on 23-30 September 1969. The statistics of the

Con-ference give some idea of its international scope and of the level of ship

research activity in the various countries of the world. There were

approxi-mately 166 engineers and scientists in attendance representing 29 different nations. Soviet bloc nations included the USSR (10 participants) and East Germany (two participants). Poland's delegate and mainland China's two delegates failed to arrive. The United States sent 17 delegates and eight observers while the host country, Italy, had eight delegates and 21 observers. Significant technical contributions to the Conference were made by 16 nations with Japan, US, USSR, Sweden, UK, and West Germany submitting more than ten contributions each. Complete statistics concerning technical contributions and committee memberships are given in Appendix A.

The work of the Conference was divided among eight committees. An

executive committee organized the Conference and made the necessary admin-istrative decisions. There are five technical committees covering the traditional technical fields of Resistance, Propulsion, Cavitation, Sea-keeping and Maneuvering. Another technical committee handles the problems of Power Performance which is defined as the whole area of predicting ship powering including model tests, expansion procedures, full scale trial

procedures and correlations between model and full scale results. (This

committee was created by the 10th ITTC to insure that the basic problem which gave rise to the ITTC would be in the hands of a single committee

instead of being divided among the three technical committees dealing

with resistance, propulsion and cavitation.) Finally, there is a

Presenta-tion Committee which deals with the tasks of recommending common symbols to be used by the towing tanks of the world and of recommending common modes of presentation of data for ease of comparison of results between

tanks. In addition it is charged with keeping an up-to-date catalog of the various towing tanks, seakeeping basins, circulating water channels, cavitation tunnels and maneuvering facilities throughout the world.

The amenities of the Conference were handled in a most admirable fashion by the several Italian organizations who hosted the Conference. The Conference was held in the Istituto per la Recostruzione Industriale

building on Via Veneta, conveniently close to downtown Rome. The official

language of the Conference was English, but simultaneous translation facilities were available for anyone desiring them.

This Conference Report summarizes in detail only the technical con-tributions made at the Seakeeping session and at the Maneuvering session. However, a complete list of written contributions to all Committee

sessions submitted prior to or at the Conference are included in

Appendix B which is organized by Committee and by various topics within each Committee's perview. This information is not available elsewhere at this time as far as this writer knows. A list of the organizations participating in the Executive Committee and in the technical sessions

-of the Conference is included in Appendix C. Because of the very large number of technical contributions from Japan, the reader may find the

alphabetical list of contributors from Japan contained in Appendix D

useful.

II. SUMMARY OF CONTRIBUTIONS TO SEAKEEPING SESSION

In accordance with the instructions of the 11th ITTC, the work of the Seakeeping Committee of the 12th ITTC was divided into the following

five areas:

Proposed Standards, New Techniques and New Facilities for Seakeeping Tests

Theoretical Prediction of Motions in Waves Characteristics of a Seaway

Propulsive Performance in Waves Prediction of Sustained Sea Speed

This subject breakdown is followed in this report.

1. Proposed Standards, New Techniques and New Facilities for

Seakee in Tests

Goodrich in Appendix I of the Seakeeping Committee Report proposes

certain standards for seakeeping experiments in regular and irregular, head and following seas. These cover:

Details of model characteristics and construction:

Shipis longitudinal and transverse gyradius should be simulated (if unknown, latter is to be 0.25 L and the

former 0.4 B, L = model length, B = model beam).

Model should include all upper works and appendages. Dimensions of model should be such that wave wall inter-ference effects should be avoided. Goodrich includes a

diagram giving values of

A/

as a function of tank

breadth to model length ratio and of Froude Number, below which interference effects are insignificant;

( - wave length, L = model length).

* For a list of all contributions to the Seakeeping Session by title,

author and organization, see Appendix B, part VI of this report.

-1)

2)

C-18-69 3

b) Quantitites That Are Usually Measured and Recorded in Seakeeping Tests:

Pitch vi) Wave Height

Heave vii) Propeller Revolutions

Vertical Acceleration viii) Propeller Torque

Relative Bow Motion ix) Propeller Thrust

Phase Angles

c) Details of Experiments in Regular and Irregular Waves

If self propelled, model (not ship) self-propulsion point should be used.

For tests in regular waves, at least ten runs should be made at each speed covering a range of wavelengths from 0.5L to 2.0L or up to wavelengths beyond the resonant condition of the model.

For tests in irregular waves, if results are desired in spectral form, at least 200 wave encounters are needed.

If only mean values of motion and wave amplitude are desired, 80-100 encounters are sufficient.

The problems associated with the joining and analysis of multiple runs needed to achieve the requisite number of wave encounters need further study.

d) Presentation of Results of Regular Wave Tests:

i) All quantities measured in (b) should be presented as functions

of

LA

in non-dimensional form using wave slope, wave

amplitude, gravity acceleration, model beam, model length,

fluid mass density and propeller diameter as non-dimensionalizing parameters as necessary.

e) Presentation of Results of Irregular Wave Tests:

i) If results are recorded digitally, presentation should be in

the form of response operators as functions of encounter frequency.

If results are obtained with an analogue, records should be analyzed to give the statistics of both the motions and the water surface in terms of the average of the 1/3 highest double amplitude or root mean square values.

iii) Alternatively, results can be presented as histograms.

) v), -iii

-In the discussion of Appendix I, Tasaki confirms the validity of the

wave-wall interference effect diagram given by Goodrich. In their

dis-cussion, Svensson and Wahl:

Suggest that several values of longitudinal gyradius between 0.23L and 0.27L be tested since the gyradius does vary with ship type and loading and since it does have a large effect on results.

Question the necessity for "complete" models with upperworks in the linear range of responses.

In connection with standard c) ii of Goodrich's Appendix,

Svensson and Wahl suggest that 6-10 runs are sufficient for commercial work but that 15-20 runs are needed for research experiments.

Suggest that results be presented as functions of

J/L

rather

than L4 (see standard d) 1).

In their contribution, Motora and Fujino describe the new Seakeeping Basin at the University of Tokyo. The principal dimensions are 50 x 30 meters, 2.5 m deep with a channel approach to one corner of the basin that is 30 m long and 3.5 m wide. The basin is equipped with an X-Y dual carriage that is used as a reference level for the model and carries the cables necessary to power the model and to take out signals from the model. A 50-m-hydraulic wavemaker is fitted to the long side of the basin.

Models of 2 to 2.5 m in length can be tested. Completion of the facility

is scheduled for February 1970.

Yamanouchi and Matsumoto's contribution describes two encounter

wave recorders, one for use with models and the other for use with

full-scale ships. The elements used in both recorders are: An artifical horizon controlled by a gyro, A wave height sensor, and

A horizontal accelerometer,

all mounted on the end of a beam projecting forward of the stem of the model or ship. For the model, the wave height sensor is a non contact, capacitance type sensor composed of two 10 cm-square plates, 20 cm apart kept in the horizontal plane. For the ship, the wave height sensor utilizes

radar.

Loukakis' contribution, based on his experience in the MIT Towing Tank makes the following points:

a) The wave form generated in the towing tank has to be ergodic

and random if results are to be accurately presented in spectral form. If the wave form is composed of discrete harmonic components, its spectral

form is a series of spikes; and results of tests in these waves cannot yield many of the statistical results sought in seakeeping tests.

C-18-69 5

b) The characteristics of the wavemaker as a filter must be compensated

for, if specified spectra are to be reproduced.

c) The standards suggested by Goodrich concerning required number of

wave encounters can be misleading if applied indiscriminately. In lieu of

the standards suggested by Goodrich, Loukakis suggests the following test

durations:

One half hour (full scale) if only RMS values of linear responses are desired,

Two hours (full scale) for prediction of added resistance in waves,

Five hours (full scale) for prediction of number of slams, Ten hours (full scale) for prediction of the average of the 1/100 highest values of any response.

d) Small changes of two input spectra having the same RMS value can

cause very large changes in responses. Loukakis suggests that if standard

spectra cannot be reproduced in a tank with confidence, it is preferable to

obtain results by conducting regular wave tests and by superpositioning the results.

e) Favors a two parameter standard sea spectrum of the kind suggested

by S.T. Mathews (NRC)* (see part 3 of this section).

2. Theoretical Prediction of Motion in Waves

Appendix 1I by Tasai and AppendiXIII by Grim are survey papers. Tasai reports the progress in the improvement of the linear theory of ship responses in longitudinal waves, while Grim reports progress in the non-linear case. Appendix TV by Yamanouchi is an original contribution based on a paper he presented to the Joint US-Japan Seminar on Applied Stochastics in September 1968 and a paper published by the Society of Naval Architects of Japan in June 1969.

Abkowitzts contribution shows the rationale for the choice of axis

system for ship maneuvering on one hand (axes fixed in the ship) and for

seakeeping on the other hand (axes fixed in the earth). Vugts applies strip

theory to compute coupled roll, sway and yaw in oblique waves. Tagaki and

Ganno try to improve strip theory by considering three dimensional effects,

non-linear effects, viscous effects, etc. Tamiya modifies the roll equation

to include some non-linear effects essential for treating the extreme case

of capsizing. Manx develops an interpolation theory that leads to the same

* See Appendix C

)

.

iv)

results as slender body theory at low frequencies and to the same results as strip theory at high frequencies.

Hwang's contribution gives values of the calculatedoadded Rass for

chine shaped sections as a function of deadrise angle (0 to 45 ), sectional

area coefficient (0.50 to 0.90) and beam draft ratio. Results are valid only for very small motions at very high frequencies.

3. Characteristics of a Seaway

The 11th ITTC recommended the adoption of an Interim Standard Spectrum (ISS) to be used for model tests in irregular seas provided that the experi-menter had no knowledge of a "better" spectrum. By "better" was meant a spectrum that was known to be more representative, than the 1SS, of the

actual seaway that the tests were supposed to simulate. Abkowitz in

Appendix V, as well as the contributions by Lofft and Cummins, summarizes experience with the 11th ITTC spectrum and makes recommendations for the

future.

The 11th ITTC ISS is a single parameter spectrum requiring only specification of a characteristic wave height,

'1%T' for its complete

definition. Cummins in his contribution states his belief that the stan-dard spectrum should require specification of at least two parameters for its definition and following S.T.Mathews (NRC), he suggests specification of a characteristics wave period Tw as well as a characteristic wave height,

Cummins points out that although in reality there are an infinity of

spectra for any specified values of the two parameters, T 1

w, it

9

nevertheless seems reasonable to choose a single spectrum to represent any

pair of values, Tw and.

Cummins makes the further point that if enough is known about the

sea state that is to be simulated, it is possible to determine_the probability

density function that the spectrum corresponding to any pair, Tw and '3w

will occur. This probability can then be used in computing the probability of occurrence of the responses, if certain simplifying assumptions are made. In recognition of the great usefulness of these data, Cummins shows a

rough estimate of the probability density function for a specific set of environment data given by N. Hogben and F.E. Lumb (NPL). He also con-ditionally offers to make a more precise estimate of this function for

another very complete set of wave data based on the well-known W.J. Pierson (NYU) hindcast.

Cummins' proposal is, of course, of little value, unless sufficient environmental data is available to compute the probability density function for the occurrence of spectra. Nevertheless, his contribution has the merit of offering a standardized procedure for calculating the responses

to a very high level of synthesis in the event that complete environmental data is available, whereas the 11th ITTC specification suggests no such procedure.

C-18-69 7 In the event that the available environmental data were not sufficient to compute the probability density functions suggested by Cummins, but some data were available, it would seem desirable to use Mathewls (NRC) suggestion to determine a two parameter spectrum rather than use the 11th ITTC ISS.

The procedure for determining Tw would then depend on having sufficient data available concerning the sought after sea state to determine Mathewts parameter, k, where: 2

T/

w 2 / k2 w fully developed 2/ W fully developed

The current ISS corresponds to k = 1 and to a constant value of

. If no data were available concerning the sea

state to be simulated, the 11th ITTC ISS could obviously still be used. Lofft shows that for the North Atlantic, 44% of some 356 measured spectra correspond to 0.9< k <1.1, whereas 74% lie between 0.8<k <1.2, the lower value representing seas not yet fully arisen and the high value indicating

decaying seas with considerable swell component. Thus Lofftts contribution

concludes that the ISS as it stands is reasonably representative of the most probable spectrum in the North Atlantic.

All of the preceding assumes unidirectional seas. Cummins notes,

unhappily, that the lack of realism arising from this assumption is over-riding with respect to all other deficiences, including the ones he has discussed. Abkowitz, Appendix V, recognizes this fact and suggests that the most commonly used spreading function be adopted as an interim

stan-dard. This function is: 2

2

cosw

1r

0.

where -9015,q1.5 + 90 is the angle between the predominant wind direction and the direction for which the component spectrum is desired.

The values of the ordinates of the spectrum of the unidirectional sea are multipled by the spreading function in order to obtain the ordinates of the directional spectrum.

In his contribution, Norrbin analyzes some visually observed wave records off the Swedish Coast and separates the records into conditions of

increasing wind, steady wind and abating wind, He shows that the

character-istics of the records corresponding to the first and last condition, being of relatively narrow frequency band, correspond to predictions from the Rayleigh theory, whereas the record corresponding to steady wind, covering as it does a relatively wide frequency band, deviates somewhat from the Rayleigh theory predictions.

=

-or'

-4. Propulsive Performance in Waves

Todd's Appendix VI is based largely on model and ship work by

Gerritsma, et al., on the liner MAASDAM and on work by Ochi, NSRDC. As

far as predictions of added power consumption in waves are concerned, Todd considers that

Agreement is good between results of tests in irregular waves and computed results for irregular waves based on linear superpositioning of results obtained in regular waves.

Agreement between results obtained by either of the above two methods and full scale measurements (as obtained on the MAASDAM) is good.

Prediction of response functions for increased power on the basis

of tests in irregular seas is not possible. This is contrary to response

functions for motions which can be obtained from irregular sea tests. Theoretical prediction of the response functions for increased power in waves is not as accurate as theoretical prediction of response functions for motions.

It should be noted that these conclusions are valid for fine ship forms (CB 5 0.65) and may not be valid for full hull forms.

Nakamura's, et. al. contribution pertains to the last conclusion by

Todd. Their carefully conducted correlation between theory and experiment (not only their own experiments but also those of Sibul, UCB) shows what appear to

be

significant errors both in motions and in added resistance. Whether these errors are significant in a practical design sense could be determined only by reference to design goals.

Aertssen's (UGh) contribution pertains to Todd t conclusion (b). For long crested seas, Aertssen's data superficially confirms Todd's

con-clusion because the average difference between full scale observations and results predicted from superpositioning regular wave results comes to zero for the seven cases reported by Aertssen. However, the range of data was from -6% (observed power lower than predicted) to +13% (observed power higher). For short crested seas, the observed power is substantially

lower than the predicted power, averaging about -6% for modest sea states and to -10% for severe sea states.

Lewis' contribution points out correctly that the response function for added power in waves should be determined by combining two other

response functions, added propeller revolutions in waves and added

torque in waves. Prediction of power in irregular waves by using a single

response function related to added power alone was shown to be incorrect

by Gerritsma, et. al. (DSL).

Steven's Appendix VII discusses the many, very serious problems associated with the testing of high speed craft, particularly planing

craft, in waves. It has long been realized that even in calm water, the

-C-18-69 9 water resistance of a planing craft, unlike that of an ordinary surface ship,

cannot be properly treated in isolation from all cf the other forces acting on the boat -- that is, hydrodynamic lift, buoyancy, weight, thrust, aero-dynamic lift and drag. These same complications hold true in rough water. Stevens, contribution suggests some practical palliatives which are important

to use until a broader approach to the problem is available. However, in

the end, only the sophisticated techniques used for predicting total

air-craft performance will suffice for planing air-craft; the techniques ordinarily

employed for surface ships, which Stevens tries to adapt to planing craft, are quite inadequate.

5. Prediction of Sustained Sea Speed

This topic, initiated by the 11th ITTC, was considered of utmost importance by the Seakeeping Committee since it is the final objective of seakeeping research. In the Committeels words it is a surprising fact that research in seakeeping has found little application in the approach to ship design." Gerritsma in Appendix VIII provides a partial answer to this question and at the same time gives an excellent summary of the state of the art of predicting sustained sea speed.

The prediction of sustained sea speed involves consideration of two

speed domains, the involuntary and the voluntary. In the involuntary

speed domain, the ship proceeds at the maximum speed permitted by its

engines in the environmental situation in which it finds itself. It also

proceeds on the most direct course to its destination. In the voluntary

speed domain, the speed and course at which the ship is driven is deter-mined by the captain or deck officer based on what he considers the maximum safe speed and safa.couvso to be

:in

view of t.1:10,oxistihiwbather,And/or-othor hazardous conditions. In the involuntary speed domain, tho following elements are needed to predict sustained sea speed:

I. Involuntary Speed

Domain:

Available power

Smooth water resistance Added resistance due to wind

Added resistance due to roughness and fouling Added resistance due to waves

Added resistance due to rudder action and yawing Smooth water propulsive efficiency

Change in propulsive efficiency due to 3), 4), 5) and 6). 1)

.2)

.6)

7)

(It might be noted that the subject of the previous section, "Propulsive Performance in Waves" included elements 2), 5), 7), and part of 8), whereas elements 2) and 7) are also included in the considerations of the Resistance,

Performance, Propeller and Cavitation Committees. However, elements 3),

4), 6), and most of 8) are considered only under Sustained Sea Speed.) In the voluntary speed domain the elements needed to predict sustained sea speed are as follows:

II. Voluntary Speed Domain:

Deck wetness index of performance as a function of sea state, ship speed and course

Slamming index of performance as a function of sea state, ship speed and course

Screw racing index of performance as a function of sea state, ship speed and course

Seasickness index of performance as a function of sea state, ship speed and course

Vertical acceleration index of performance as a function of sea state, ship speed and course

Rolling motion index of performance as a function of sea state, ship speed and course

0004 0000

000000

other possible indexes of performance

n) 00 0000

Accepted critical values of each of the preceding indexes of performance, above which value the captain voluntarily elects to slow the ship or change course Determination of the governing index of performance from among the list 1) through n), using (n+1).

For any given ship type and condition of loading, all of the indexes of performance that are likely to be governing Lsee Element II (n+21/ will be known and the number of these indexes which it is necessary to

consider will rarely exceed two or three.

Gerritsma points out that substantial knowledge exists for all elements in both the voluntary and involuntary speed domains except for Element (n+l) of the voluntary domain. This element involves subjective human judgments which are not only not easy to assess, but are difficult

5)

'6)

7)

C-18-69

ii

to substantiate. It is easy to infer from Gerritsma,s Appendix that if more were known concerning Element II (n+1), the research in seakeeping would have

long since found greater practical application.

Nevertheless, Gerritsma cites impressive evidence to refute those

who would deprecate seakeeping research. One example he points out, based

on work by Tasaki (SRI), concerns the relationship between sustained speed and ship freeboard, assuming that Element II 1 is the governing index of

performance (for many ship types this is commonly the case). For Element II

(n+1), Tasaki assumes that if the probability that the ship will ship green

water over the bow exceeds 5%, the ship captain will reduce speed until

that probability is 5%. Using the sophisticated techniques developed during the past two decades of seakeeping research, Tasaki shows that for the particular ship he considered, the sustained speed of the ship could be increased by 3.5 knots in the sea state, corresponding to Beaufort Wind Scale 6-7, by simply increasing the freeboard of the design by 1.5 meters. Considering that this sea state is exceeded a majority of the time in the winter North Atlantic, such a minor change in ship dimensions could have a

major effect on the shipis earning power. This is convincing evidence that

application of seakeeping research to ship design can pay impressive divi-dends.

Tasai,s (KU) contribution concerns Elements II 1 and II 2 of the voluntary speed domain. Tasai shows that in computing the occurrence of a deck wetness, it is very important to take account of the dynamic swell up

of the water due to ship motions. If account is taken of this in the

theoretical calculations, these agree with experimental observations. Tasai also shows that the critical threshold vertical velocity associated with the occurrence of a slam is not a fixed quantity as suggested by

Ochi (NSRDC) but is rather a function of ship speed and decreases as ship speed increases. Tasai defines a slam in terms of:

the character of the impact pressure vs time function, the peak value of the impact pressures,

the longitudinal extent of the peak pressures.

Tasaki,s contribution concerns Element I 3 of the involuntary speed domain. He verifies both the crucial important of wind resistance in

relation to wave resistance as well as the importance of accurate measure-ments of wind resistance.

AertssenTs contribution concerns Element II (n+1) of the voluntary

domain about which the least is known. He suggests, for example, that the

captain of a tanker or ore carrier may be willing to accept a deck wetness frequency of occurrence of 10-12 per 100 oscillations, whereas the captain

of a fruit carrier will not accept afrequency of more than 5-7. To reduce

the subjective elements concerning acceptable levels of the slaming index of performance, Aertssen suggests the installation of slam severity measurement devices aboard ship. If the captain is told by the ship design engineers

what levels should not be exceeded on this meter, the necessity for him to make subjective decisions is removed. This approach could conceivably be used for many of the performance indexes.

Svensson and Wahl shed light on Element I 1 of the involuntary speed domain. They show that on a diagram of power versus speed, with sea state as a parameter, the available power as well as the required power are both functions of speed. Though not mentioned by Svensson and Wahl, the nature of this function for the available power depends on the kind of engine used to drive the ship. For example, with a diesel engine the available power decreases significantly with speed, whereas with a steam or gas tur-bine, the available power is more nearly a constant with speed.

III. SUMMARY OF CONTRIBUTIONS TO MANEUVERING SESSION

The work of the Maneuvering Committee as determined by the 11th ITTC concerned the following topics:

Definitive Maneuvers: Review the choice, definition and methods of measuring the quantities and qualities that must be considered in defining the maneuvering properties of a ship

Maneuvering in Restricted Waters: Emphasize model techniques

and prediction methods in the field of maneuvering in restricted waters

Correlation of Maneuvering Results between Facilities: Attempt

to explain reasons for discrepancies in results from different laboratories Model-Full Scale Correlation: Collate data on the correlation between model test and ship trial results

Scale Effect: Collate scale effect on model appendages as it affects maneuvering qualities.

For the purposes of this report, the latter three topics are com-bined into a single topic (No. 6) and three new topics are added to take

account of all of the contributions to the maneuvering sessions. These

three new topics are:

3. Effect of Wind on Maneuverability

4, Mathematical Simulation of Maneuvers

5. Rudder Hydrodynamics

1. Definitive Maneuvers

Several new definitive maneuvers were proposed at the 12th ITTC that are more suitable for unstable ships than the existing standard definitive

maneuvers specified by previous ITTC,s. This is currently an urgent problem

largely because of the advent of the large, full form tankers which have mostly been found to be unstable in straight line motion in deep water.

C-18-69 13 One of the most interesting of the proposed definitive maneuvers is

the Reversed Spiral Test originally proposed by Bech (HyA)* in 1967 and reported by L. Wagner-Smitt (HyA). In this test the average rudder angles needed to maintain a specified turning rate (yaw angular velocity) are

determined for a range of turning rates to port and to starboard. This is

the reverse of the usual Spiral Test where the turning rate is measured as a function of specified rudder angles. The latter tests require an extra-ordinary amount of searoom and take a lot of time, particularly for unstable

ships. Furthermore, for unstable ships, the relationship between rudder angle and turning rate cannot be uniquely determined at small rudder angles with the ordinary Spiral Test because for unstable ships there are a wide

range of equilibrium turning rates for any given small rudder angle (at

zero rudder angle this range corresponds to the height of the Dieudonne spiral loop).

By a trial and error process, it is, of course, possible to determine the range, average and mean rudder angles needed to maintain any specified

turning rate, even turning rates within the unstable range. This is the

Reversed Spiral Test. The advantages claimed for the Reversed Spiral Test compared to the ordinary Spiral Test are:

It defines the angular velocity-rudder angle relationship in the most interesting region of small angular velocities and small rudder angles where the ordinary Spiral Test fails to define the relationship.

It takes less time and less sea room than the ordinary Spiral Test. In a restricted sense, it simulates practical course changing

maneuvers.

In spite of these advantages, adoption of the Reversed Spiral Test as a standard definitive maneuver by the Maneuvering Committee was post-poned pending further study. This action was taken because of concern

that unsteady effects might be contaminating the results of these tests. In an effort to strengthen the case for the Reversed Spiral Test, the contribution by Nomoto** describes the analogy between the results of a Reversed Spiral Test conducted for an unstable ship and the results of an

ordinary inclining experiment for a ship that is in unstable equilibrium in the upright position (such a ship is, of course, in stable equilibrium at some modest heel angle). This analogy is a familiar one having been

introduced by M.A. Abkowitz (MIT) many years ago. In this writer's opinion, this analogy strengthens the case for adopting the Reversed Spiral Test as a standard maneuver.***

* See Appendix C.

** For a list of all contributions by title, author and organization to the

Maneuvering Session, see Appendix B, part VII of this report.

*** Further theoretical justification of the Reversed Spiral Test is given by Strandhagen and Sharpe, "Spiral and Reversed Spiral Tests - Handling Qualities of Ships," Second Ship Control Symposium, Annapolis, Md., Nov. 1969 r 4 -a) c)

-The Modified Zig Zag Maneuver described by Motora and Fujino in their contribution represents a minor modification of the standard Zig-Zag

Maneuver specified by an earlier ITTC. The latter maneuver has in the past called for the execute yaw angle,'1'; , to be equal to the execute rudder angle,

k,

. For stable ships, the overshoot yaw angle, which is

one of the desired results of the Zig-Zag test, approaches zero as the

execute rudder angle and yaw angle simultaneously approach zero. However,

for ships that are unstable in straight line motion, it has been found that the stipulation of So= Po, results in the overshoot yaw angle

increas-ing with decreasincreas-ing values of/. and The Modified Zig Zag Maneuver

overcomes this difficulty by specifying that the execute yaw angle,

t

,

should be less than the execute rudder angle,

A.

Computed results by

Motora and Fujino show that if is taken as much less than

tio,

the

over-shoot yaw angle does decrease with decreasing ip, even for unstable ships,

until a lower limiting value of

Lis

reached when the overshoot yaw

angle begins to increase again. Values of this lower limiting rudder

execute angle as a function of for a particular unstable ship are as

follows.

to

Lower Limiting Rudder Execute

AngleA

0.2 40 0.4° 6o 0.6 8o 1 0.8 0o 15°

It is interesting to note that these values have operational

signifi-cance. If the sensitivity of the instrument display and other data avail-able to the helmsman allow him to detect yaw angle errors no smaller than

0.2o, he will need to use rudder angles larger than + 4o t8 his

heading. If the minimum detectable pw angle error

Is

0.4°, he will need

to use rudder angles larger than + 6 , etc. These results thus make clear,

in operational terms, what the coRsequences of instability in straight line motion are.

Two other new definitive maneuvers, the Pull Out and the Weave

Maneuver, are discussed in Appendix I of .the7-ComMittee Repatt

by Nomoto and Norrbin. These were devised by R.K. Burcher (AEW). The

Pull Out Maneuver determines the range of yaw angular velocities on either side of zero within which an unstable ship is in unstable equi-librium at zero rudder angle; that is the height of the Dieudonne' spiral

loop. The Weave Maneuver determines the range of rudder angles on either

side of zero within which an unstable ship may not respond, that is, has zero,yaw angular velocity. It thus determines the width of the Dieudonne spiral loop for unstable ships.

maintain

C-18-69 15

The Pull Out Maneuver is a pair of maneuvers in which the rudder is abruptly brought back to zero deflection after steady turning has been

achieved at some specified initial rudder angle -- one maneuver is from port and the other maneuver is from starboard. If the ship is stable, the terminal yaw rate (usually a small, non-zero value caused by a dynamic asymmetry such

as an odd number of propellers or by any number of uni-rotating propellers)

will be the same for both the port and starboard initiated turns. If the ship

is unstable, the terminal yaw angular velocity from the starboard turn will be to starboard and that from the port turn to port -- the difference between the two terminal rates being the height of the Dieudonne spiral loop.

The Weave Maneuver is basically a Modified Zig Zag Maneuver conducted with a variety of execute rudder angles and execute yaw angles all of

relatively small magnitude. By a trial and error procedure the lower

limit-ing values of the rudder execute angle as a function of (see table of

values from Motora-Fujino report given earlier), can be determined with a full scale ship or with a free running model. Extrapolation of these

values to zero gives the half width of the Dieudonne spiral loop. In the

case of the Motora-Fujino data this half width would be 2 .

Of the proposed new definitive maneuvers, the Pull Out seems the

simplest and easiest to conduct, yielding useful information. The end

results sought by the Weave Maneuver and the Revised Spiral Test are also very useful theoretically and operationally, but the maneuvers themselves would seem to require considerable time to conduct even though these times may be less than that demanded by the ordinary Spiral Test.

2. Maneuvering in Restricted Waters: Test, Theory and Facilities

A distinct change in emphasis has taken place with regard to

maneuvering in restricted waters in recent years. The closing of the

Suez Canal in conjunction with the enormous increase in the size of

tankers (which has made them incapable of transiting any existing canals) has shifted the emphasis from ships operating in waters restricted in both depth and width (as in canals) to waters restricted only in depth* (as in ports or bays in general). While this represents a large simplication in the basic problem the remaining problem is, nevertheless, very acute for large tankers because:

* Exceptions to this shift in emphasis are work carried out by H. Eda, C.J. Henry and G. Fridsma (DL) under the sponsorship of the United States Atlantic-Pacific Interoceanic Canal Study Commission, reported in

"Application of a Simulator for Ship Maneuvering in Restricted Waters," Second Ship Control Symposium, Annapolis, Md., Nov. 1969 (A brief excerpt of this work was presented at the ITTC by D. Savitsky, DL) and the work by Fujin° reported in Appendix II, Part 2 of the Maneuvering Committee Report discussed subsequently.

The proportion of total operating time that they spend in what might be called hydrodynamically shallow water, that is bottom clearance/ship

draft ratio, (h-T)/T<3.0, is greater than for smaller ships (h = water depth; T = ship draft).

In common with all ships, the hydrodynamic side forces and moments acting on the shipfs hull tend to be greater in shallow water than in deep.

This factor in conjunction with the huge size of these ships renders control by tugs much more difficult than for the usual size ship.

Primarily as a result of b) the inherent turning ability of

ships (without tug assistance) tends to degrade in shallow water compared

to deep.

While the turning ability of tankers in relation to their length

even in shallow water may be better than many ships in deep water, their

enormous length necessitates very large sea room for any maneuver.

0

The propulsive power available for stopping tankers has grown at

a far slower rate than the increase in size. For collision avoidance, both stopping and turning ability are essential and a deficiency in one can

often be compensated for by a gain in the other. If both are deficient,

collisions are more likely.

The paper by Tuji et al. gives experimental results for a particular

tanker form* that are needed to evaluate quantitatively b) and c)

above. Presented are measured values of the lateral force, Y, and the

yawing moment, N, (about the ship c.g.) as a function of attack

angle,"

and bottom clearance/draft ratio (h-T)/T for

0<4<

180° and 0.1.(

(h-T)/T<6.0. While the latter parameter is not significant at values greater than about 3.0, the values of the lateral force and yawing moment

at (h-T)/T= 0.1 are almost five times those at (h-T)/T = 3.0 for all

values of angles of attack. Limited results (0 = 90° only) are also given for waters restricted in clearance on one side (as alongside a pier) as well as restricted in depth. Forod = 90°, these results show that bottom clearance has a larger effect than side clearance on the lateral force. However, a clearance of 20% of the ship beam on the side in conjunction with a clearance of 20% of the ship draft on the

bottom has more than twice the effect of the latter alone. On the other

hand, a 50% clearance on the side in conjunction with a 50% bottom

clearance has only 1.5 times the effect of the latter alone.

* The characteristics of the form are: length/beam, L/B, ratio = 6.5, beam draft, B/T, ratio = 2.5 and block coefficient, CB = 0.815.

.e)

C-18-69 17

Appendix II, Part 1 of the Committee Report by Norrbin summarizes

developments in the theoretical prediction of restricted water effects since the 1966 ITTC. These developments include papers by E.O. Tuck (NYU), N.J. Newman (MIT), M. Kan (SRI) and T. Hanaoka (SRI). The theoretical predictions of the latter two authors are compared to experimentally derived turning rates (obtained by N. Koseki et al. SRI) in Appendix II, Part 2 of the Com-mittee Report by Motora. This comparison shows that both theory and experi-ment predict a severe degradation in turning ability as bottom clearance is

reduced. With a bottom clearance of 20% of the draft, the turning diameter is 50% larger than the deep water turning diameter for a wide variety of ship models as well as according to the theory of Kan and Hanaoka.

The Appendix by Motora also includes data on the stability in straight line motion of tankers in shallow and in deep water obtained by Mori and

Fujino using constrained model tests. These data show that while tankers

are unstable in straight line motion in deep water they become stable in shallow water, and the shallower the water is the more stable the ships become. This model result is confirmed by the full scale spiral tests of a Great Lakes steamer whose results were originally published by Motora and R.B. Couch (UM) in 1961.

Data obtained by Fujino in waters restricted in both depth and width (canals) are also presented in Motora's appendix. These data show the expected result that as the canal width becomes narrower the directional stability with controls fixed is severely impaired and that ships that are quite stable in waters, unrestricted in width, become very unstable even in relatively wide canals. However, a relatively simple automatic control system based on yaw angle deviation renders a ship that is mar-ginally stable in unrestricted waters, directionally stable with controls working in narrow waters at least down to canal widths that are 5- times

the ship width (side clearance/beam ratio = 2.25).

Appendix II Part 3 by Norrbin discusses various test facilities and prediction methods that are available for predicting confined water

per-formance in the presence of currents, wind and waves. Included in this

discussion are descriptions of special shallow water facilities at the Versuchsanstalt ftir Binnenschiffbau (VBD), Duisburg, W. Germany;

Nether-lands Ship Model Basin (NSMB), Wageningen, NetherNether-lands; Naval Ship

Research and Development Center (NSRDC),Cartlerock, Md., USA; National

Physical Laboratory (NPL), Feltham, UK; Chalmers University (CTH),

Gothen-burg, Sweden; Paris Model Basin (PMB), Paris, France; Gdansk Shipbuilding Institute (SRIG), Gdansk, Poland and University of Tokyo (UT), Tokyo,

Japan. Not included in this discussion but described in the separate contribution by Firsoff, Nikolaev and Pershits is the new rotating arm, rotating beam facility at the Kryloff Ship Research Institute (KSRI), Lenin-grad, USSR. This facility, 70 meters in diameter and capable of propelling a 2-meter model at 52 meter/sec. or a 6-meter model at 15 meters/sec., is apparently not yet equipped for restricted water work.

Norrbin also discusses the use of "image" models to study the effect of tank width on resistance tests and discusses the effect of confined

rise to important scale effects for models tested at Froude speed which Norrbin believes may be reduced by the injection of polymer additives to the tank water. However, he states that not enough is yet known about this subject to make a recommendation possible at this time.

The subject of simulation of full scale ship handling in confined waters by means of small scale model tests is also covered in Appendix II, Part 3 by Norrbin. He recommends that the guidance of free running model tests in confined waters should not be done by a human operator but rather should be done by means of an automatic control that simulates the human

behavior with the full scale ship as closely as possible. Valid,

quantitative comparisons among different full scale ships under manual control are difficult enough to make in confined waters; such comparisons with models under manual control are even more difficult to make.

3. Effect of Wind on Maneuverability

The two papers on this topic presented at the Conference by Takaishi and Tsjui and by Ogawa are complementary. The first describes the towing tank with wind blower used at the Ship Dynamics Division, Ship Research Institute, Tokyo for testing models subjected to wind forces, and presents

some results on wind forces and moments. The second uses these and other captive model test data in association with the non-linear equationsof motion to predict the motion of a typical 900-ft-long tanker in a uniform wind and current. The results show for various combinations of wind and

current speeds and directions:

The minimum ship speeds needed to maintain a straight course within the constraints of a maximum allowable rudder angle and drift angle of

10 , and

The trajectories of the turning maneuver to port and starboard,

for full load and ballast condition for 35 rudder angle.

The straight course computations in a) show that a minimum ship speed

of about 9 knots is needed to maintain a straight course within the stated constraints for a wind speed of 60 knots blowing directly off the beam.

With both a 60 knot wind blowing at 90 to the ship's velocity and a two

knot current at an angle of 150 to the ship's velocity, this minimum speed

increases to almost 16 knots.

4. Mathematical Simulation of Maneuvers

Both Norrbin and Nomoto introduce various approximations to the complete, non-linear, second-order differential equationsof motion by

neglecting certain, not too significant, hydrodynamic terms and by express-ing the rudder angle for automatic steerexpress-ing as a function of yaw rate, yaw acceleration, etc. Nomoto compares his linear and non-linear simulation

to the observed MARINER zig zag test results. Norrbin uses his

approxima-tion to study the reversed spiral as well as the time history of the yaw rate and pivot point position during an out-to-out maneuver as well as

C-18-69 19 show that the pivot point is somewhat forward of the bow during a steady turn but that it varies from plus infinity (forward) to minus infinity (aft)

during an out-to-out maneuver. Norrbin's time history of the yaw rate

during a pull out maneuver is of particular interest.

Stuurman in his contribution defines a mathematical model describing the behavior of a helmsman steering a ship along a straight course. No results are given.

Rudder Hydrodynamics

In the lone contribution to this topic made at the ITTC, Rakamaric and Korlevic describe experiments to determine the possibility of simulating higher Reynolds number for rudder hydrodynamic tests by increasing the

sur-face temperature of the rudder. In the very limited range of temperature and Reynolds number within which they could experiment, the confirmed this possibility.

Correlation of Maneuvering Results: Model to Full Scale, Different Model Techniques, Different Facilities

All of the contributions to this topic are appendices to the official report of the Maneuvering Committee and were prepared in response to

recommendations of previous ITTC's. Gertler's contribution covers results of captive model tests from different establishments, while Suarez deals

with results of free running tests from different establishments. Suarez's

report includes the results of 16 different size models of the MARINER class merchant ship ranging in length from 1.2 to 7.0 meters, submitted by 16 different testing establishments from seven different nations

(France 1, Italy 1, Japan 8, Poland 1, UK 2, USA 2, Yugoslavia 1). Gert-ler's report (including late results submitted by R.K. Burcher (AEW) includes results from straight line, rotating arm and Planar Motion Mech-anism tests of 12 different models submitted by 11 different establish-ments from eight different nations (Denmark 1, East Germany 1, France 1,

Japan 3, Netherlands 1, UK 1, USA 3, USSR 1).

Suarez's summary leads to no definite conclusion except a recommended curtailment in the extent of theoresults sought in this correlation program

to rudder angles greater than 15 and to steady turning diameter only.

The Maneuvering Committee's own evaluation of Suarez's results is as follows: "The Committee has not yet had sufficient time to conclude its

investigation of the considerable differences that exist and recommends that examination of the discrepancies between the various free model data should continue with a view to establishing agreed standard test techniques."

Gertler's report, while indicating very large differences in results between establishments, notes that captive model testing is still in its infancy (in contrast to free running tests) and that these techniques

will in all likelihood gain widespread use in the future. Gertler as

well as the Committee as a whole recommends that the first phase of the ITTC Standard Captive Model Test Program which concerned correlation of

of the values obtained by various facilities of specific derivative and hydrodynamic coefficients (for ultimate use in the equationsof motion)

be ended and that the second phase be undertaken. The second phase is

concerned with:

Correlation of trajectories obtained directly from free running model tests with trajectories computed using data derived from captive tests of the identical model.

Correlation of trajectories obtained from a full scale ship with trajectories computed using data derived from captive model tests of that ship adjusted to take account of actual full scale conditions.

In addition Gertler recommends that sensitivity studies be carried

out to determine how much individual hydrodynamic coefficients could be

changed without affecting the trajectories significantly.

Appendix IV by Vosper on full scale-model correlation presents results

submitted by the UK, Japan and France but leads to no firm conclusions. The

Committee's recommendation on this topic is that in view of the importance

of the correct understanding of model-ship correlation, the members of the

ITTC should once again be urged to supply the Committee with data. Appendix V by Thieme discusses scale effect in its correct context

as being only one of the very many factors that enter into the question of

model-full scale correlation of maneuvering results. Like Suarez, Thieme

suggests that for the study of scale effect alone, only steady turning

results be used, since in transient turning many significant factors are perforce, dissimilar between model and full scale.

APPENDIX A

NUMBER OF WRITTEN CONTRIBUTIONS' AND COMMITTEE MEMBERSHIPS BY NATION AND By COMMITTEE

Belgium Denmark4.,r France Germany (W.) Israel Italy Japan Korea (S.) NetherlandS Norway Spain Sweden

1 II III IV V VI Exec, Resist. Perform, Propeller CaVit., Seakeeping 00,0, 5* 1 12*

*

1 OI On114 4 '

1*

2*1

*

_lo*

2*

Jot

41-

11.4

1*

1

1*

1*

4wr _ '2' 4 1* 2* ,

1*

intim

11*

2*

-=

3 yc

1*

1 &w. 133 1* 1* 3 3 101

1

1 44' 5. 13.

1

5 7 3 4 2. 3 VII VIII Written Committee Maneuv. Present. Contr. Membership Nation.

Committee Number and Name

Total

*

--2 1

*

*

*

--*

1*

*

7* 7 1 --1* --1 1 4*

Signifies one or more Committee Members

1

Submitted prior to or at Conference;

includes appendices to Committee Reports

UK US USSR Yugoslavia (7) 2* 3* 5 1 31(7) 2* 1* 2 21(8) 1 8* 4 16(4) 7* 3* 1 18(7) 3* 6* 29(5) 2* 2* 1 1 19(6) 1* 4(8) 10 28 13 5 138 6 8 3 1 (52)

C-18-69 23 APPENDIX B

List of Written Contributions' to 12th ITTC

Committee II. Resistance

1. Experimental Determination of the Components of Resistance

"Techniques for Measuring the Components of Resistance for Ship Models," - J.R. Shearer, NPL* (App. II to Com. Rep.)

"Determination of Wave and Viscous Resistance from Wave and Wake Field behind Model," - V.J. Tkachev, KSRI

"Experimental Results concerning Interaction between Ship Waves and Boundary Layer," - F. Mildner, VWS

"On the Wavebreaking Resistance of Full Hull Forms," - S.D. Sharma, ISU

"New Component of Viscous Resistance," - K. Taniguchi i E. Baba,

MHI 2. Flow Studies

"Boundary Layer Measurements on a Double Model," - K. Wieghardt, ISU "Investigation of Boundary Layer Turbulence Stimulation," - L.F. Kozlov, UKSSR Academy of Sciences, Kiev, USSR

"Measurement of Boundary Layers of Ships," - Group of 20 authors, KU and Kagoshima Ufliversity, Kagoshima, Japan

"Velocity Distribution and Local Skin Friction in Boundary Layer with Pressure Gradient," - H. Sasajima, I. Tanaka, Y. Himeno, OU

"Modern Means to Control Flow Separation on Full Model Forms," -Y.S. Bazilevsky, A.F. Poostoshniy, V.M. Stumpf, KSRI

0

"Comparison of Velocity Distribution in Boundary Layers on Ship and Model," - K. Taniguchi, T. Fujita, MHI

3. Wave Resistance

a) "Wave Resistance Review," - J.K. Lunde, SMTT (App. III)

Submitted prior to or at conference; includes appendices to Committee

Reports

* For alphabetical key to list of organizations see Appendix C.

)

)

"Contributions on Wave Resistance," - Y.Y. Wu, CIT

"Local Wave Influence on Longitudinal Wave Cut Analysis," -K.W.H. Eggers, ISU and H. Kajitani, UT

"Michell Resistance of Taylors Standard Series," - C.C. Hsiung and J.V. Wehausen, UCB

"Sheltering Effect of Complicated Hull Forms," - T. Inui and H. Kajitani, UT

0

"Longitudinal Cut Method of Wave Analysis," - S.D. Sharma, ISU "Bow Wave Analysis of Simple Hull Forms," - T. Inui and

H. Kajitani, UT

"Some Consideration on Truncation Error in Wave Analysis, H. Tanaka and H. Adachi, SRI

"On the Longitudinal Cut Method of Wave Analysis," - H. Maruo and M. Ikehata, NUY

4. Viscous Resistance

"Viscous Resistance Review," - L. Landweber, IIHR (App. D) "Criticism of Uberoi Approach," - W.B. van Berlekom and G. Dyne, SSPA

5. Towing Tank Procedures

"Measurement of Residual Current in a Towing Tank," - R. Tasaki and H. Kitagawa, SRI

"Repeated Resistance Tests of Standard Model," - K. Yokoo, Y. Kawakami, and H. Kitagawa, SRI

"Application of Filtering to Resistance Curve Smoothing," -M. Sambolek, BI

"Automation and Processing of Results of Model Tank Experiments," - V.P. Boltenko, KSRI

6. Towing Tank Water Conditions

"Change of Roughened Surface Friction Drag in Dilute Polymer Solutions," - W.B. Amfilokhiev and A.M. Ferguson, UG

Friction Reduction of Flat Plates by Polymer Solutions," -T. Tagori and I. Ashidate, UT

,a) -b) a) -) -a)

C-18-69 25 "An Examination of Some Towing Tank Algae," - J.W. Hoyt, NURDC "Drag Reduction in a Developing Boundary Layer with Polymers," -M. Poreh, ITT

7. Added Drag in Waves

a) "Effect of Pitching and Heaving on Ahead Resistance," - K. Ueno, KU

Committee III. Powering Performance Model and Full Scale

1. Performance Prediction Factors

"NPL Performance Prediction Factors," - J. Dawson, NPL (App. III) "Note on Ship-Model Performance," - W. Graff, VBD (App. IV)

"Service Performance at Sea," - G. Aertssen, UGh (App. V) "Correlation Factors of Recent Hi-Speed Liners," - D.I. Moor, VSG (App. VI)

"ITTC Questionnaire on Model Correlation Factors," H. Lindgren, SSPA (App. II)

"Analysis of Ship Trial Results," - H. Lindgren and E. Bjarne, SSPA "Model-Full Scale Correlation of Full Form Tanker," - K. Yokoo, SRI and H. Takahashi, T. Ueda and H. Okamoto, KD

"A New Representation of Propulsion Test Results of Full Ship Models," - H. Sasajima and C. Oh, OU

"Effect of Fouling on Margin," - A. Yazaki, SRC and T. Iwata, DA "Model-Full Scale Power Correlation," - I. Antunovic and

A. Gamulin, BI

"Prediction of Ship Performance in Calm Water," - R. Brard and M. Aucher, PMB

1) "Model-Full Scale Wake Correlation on Full Tankers," - S. Sudo, HS EC

"References Relating to Performance since 1966," - M.C. Jordain, IRCN "Wake Fraction Estimates for Full Ships," - A. Yazaki, SRC

"Roughness Trial Results," - T. Tsuda, HSEC

L a)

,e)

g) -i)

-r

k) --, c)

2. Model Geosim Test Results

,"Scale Effect Experiments Shapes," - K. Yokoo, SRI, "Combined Effect of Model Propulsion Factors," - K.

on Tanker Models with Different Stern H. Takahashi, KD and Y. Kawakami, SRI Size and Propeller Load on Self

Yokoo and Y. Kawakami, SRI

c) "Scale Effects on Planing Craft," - J.B. Hadler, W.C. Moore, NSRDC

3. Model Propulsion Test Techniques

"B.I. Equipment for Propulsive Experiments with Submerged Bodies," -M. Feric, I. Modlic, BI

"Unstable Phenomena in the Self Propulsion Tests of Full Ship Models," - K. Taniguchi and K. Watanabe, MHI

"Errors in Self Propulsion Tests due to Model Acceleration," -T. Jinnaka, IHHI

Committee IV. Propeller

1. Wake Velocity Measurements

"On Velocity Wake Measurements," - H.M. Chang and J.B. Hadler, NSRDC "New Means for Measuring Unsteady Wake," - Y.P.'Otlesnov, KSRI

"Wake Surveys in Air and Water for Series 60 Models," - H.M. Chang and J.B. Hadler, NSRDC

2. Subcavitating Propeller Design Methods

"State-of-the-Art, Subcavitating Propellers," - G.G. Cox, NSRDC (App. II)

"Ratio of Projected to Expanded Areas of a Propeller Blade," -K.E. Schoenherr, Consultant, Wash., D.C., USA

3. Propeller Behavior in Inclined Flow

a) "State-of-the-Art, Propeller in Inclined Flow," - G.G. Cox, NSRDC (App. III)

4. Supercavitating Propeller Design Methods

"State-of-the-Art, Supercavitating Propellers," - G.G. Cox, NSRDC (App. IV)

Vibratory Propeller, Appendage and Hull Forces and Moments

a) "State-of-the-Art, Propeller Excited Vibration," - J. Breslin, DL (App. V)

a)

-c) . -5,

a)

C-12-69 27

"Investigation of Effect of Cavitation on Fluctuating Pressures around Propeller," - H. Takahashi and T. Ueda, SRI ti KD

"Rheoelectric Analogy for Investigating Propeller Vibrating Forces," - N.N. Pavlov, I.A. Titov, KSRI

"Calculation of Pressure Fluctuation around Propellers," -C.A. Johnsson, SSPA

6. Waterjet Propulsion

a) "Waterjet Propulsion," - V.E. Johnson, Jr., HI (App. VI)

7. Lateral Thrusters and Ship Stopping

"State-of-the-Art Lateral Thrusters," - H. Schwanecke, NSMB "Stopping of Ships using Propellers," - E.P. Lover, AEW 8. Ducted Propellers

a) 'Method of Investigation into the Efficiency of Ducts," - V.S. Shpakoff, V.K. Turbal, KSRI

9. Cycloidal Propellers

a) "Features of Cycloidal Propeller Performance," - T.B. Ibragimova and A.A. Roussetsky, KSRI

Committee V. Cavitation

Conditions Governing Natural and Ventilated Cavities

a) "Environmental and Body Conditions governing Inception and Development of Natural and Ventilated Cavities," - P.

Eisenberg, HI (App. I)

Cavitation Phenomena in Non-Uniform Flows

"Cavitation Phenomena in Non-Uniform Flows," - H.P. Rader, HSV (App. II)

"Interaction between Cavitating Propeller and Hull," - Y.N. Prishchemikhin, KSRI

"Experimental Procedures for Determining Cavitation Phenomena on Propellers in Non-Uniform Flows," - H. Lindgren, SSPA

.1,

2.

)

-3. Ship-Model Cavitation Correlation

"Comparison between Model and Ship Cavitation," - S. Bindel, PMB (App. III)

"Full Scale and Model Observations on Propeller Cavitation," -T. Ido, H. Kadoi, SRI and -T. Kondo, HIJ and H. Okamoto, KD

4. Struts and Foils in Fully Cavitating or Ventilated Flows

"Testing of Hydrofoils and Propellers for Fully-Cavitating or Ventilated Operation," - W.B. Morgan, NSRDC (App. IVA)

"Strut Ventilation," - W.B. Morgan, NSRDC (App. IVB)

"Ventilation Index and the Gravity Effect," - G.F. Dobay, NSRDC "Strut Ventilation," - R. Rothblum, NSRDC

"Determination of Gas Requirements for Ventilated Cavities," -F.R. Schiebe and J.M. Wetzel, SAFHL

0

"Procedure for Investigating Forces and Vented Heaving Hydrofoils," -I.T. Egorov and J.M. Sadovnikov, KSRI

e) "Pressure Measurements of Fully Cavitating Wedge with and without Flap," - M.C. Meijer, DSL

5. Cavitation Inception on Head Forms

"Cavitation Inception on Head Forms," - C.A. Johnsson, SSPA (App. V) "Streamlines and Isobars for ITTC Standard Headform," - F.R. Schiebe, SAFHL

6. Cavitation Testing Techniques

"Cavitation Tank with Remote Testing Operation," - Y.N.

Prischemikhin, KSRI

"Characteristics of Five Hole Pitot Tube," - H. Takahashi and T. Ueda, SRI KD

"ITTC Standard Screw Cavitation Tunnel Tests at BI," -I. Bujos, BI

-C-18-69 29

Committee VI. Seakeeping

1. Proposed Standards, New Techniques and New Facilities for Seakeeping Tests

"Proposed Standards for Seakeeping Experiments," - G.J. Goodrich, USh (App. I to Committee Report)

"Tank Wall Interference Effects on Seakeeping," (Discussion of Appendix I), - R. Tasaki, SRI

"Discussion of Appendix I," - G. Svensson and G. Wahl, SSPA "New Seakeeping Basin of University of Tokyo," - S. Motora and M. Fujino, UF

"An Encounter Wave Recorder," - Y. Yamanouchi and N. Matsumoto, SRI

0

"Proper Application of Random Process Techniques to Seakeeping,"

-T.A. Loukakis, MIT

2. Theoretical Prediction of Motions in Waves

"Improvements in Theory of Ship Motion," - F. Tasai, KU (App. II) "Non-linear Phenomena in Ship Motions," - 0. Grim, ISU (App. III) "Application of Multiple Input Spectra to the Analysis of Ship Responses," - Y. Yamanouchi, SRI (App. IV)

"On the Axis Systems in Seakeeping and Maneuvering, M.A. Abkowitz, MIT

"Coupled Roll-Sway-Yaw Motion in Oblique Waves," - J.H. Vugts, THD "Accuracy of Strip Method for Predicting Ship Motion," - M. Takagi and M. Ganno, HSEC

"Calculation of NonLinear, Nonsymmetric Rolling of Ships," -S. Tamiya, UT

"Interpolation Theory for Oscillating Slender Ships," -H. Maruo, NUY

"Added Mass of Twodimensional Cylinders of Chine Form Sections," -J.H. Hwang, SNU , ) c) d) e)

-4)

f g) -. L

-3. Characteristics of a Seaway

"11th ITTC Standard Spectrum - An Evaluation," - M.A. Abkowitz, MIT (App. V)

"ITTC Wave Spectrum," - R.F. Lofft, AEW

"Multiparameter Standard Wave Spectra," - W.E. Cummins, NSRDC "Characteristics of a Seaway from Visual Observations," -N.H. Norrbin, SSPA

4. Propulsive Performance in Waves

"Ship Power Prediction in Waves," - F.H. Todd, NSRDC (App. VI) "Propulsive Performance of High Speed Craft in Waves,"

-M.J. Stevens, BHC (App. VII)

"Propulsive Performance of Series 60 CB= 0.70 Model in Waves," -S. Nakamura, OU, R. Hosoda and -S. Shintani, DA

"Discussion of Appendix VI," - G. Aertssen, UGh "Discussion of Appendix VI, 7 - E.V. Lewis, WINA

5. Prediction of Sustained Sea Speed

"Sustained Sea Speed," - J. Gerritsma, DSL (App. VIII)

"On Deck Wetness and Slamming of Full Ship Forms," - F. Tasai, KU "Increase of Power due to Wind and Waves - Discussion of

Appendix VIII," - R. Tasaki, SRI

"Discussion of Appendix VIII," - G. Aertssen, UGh

"Discussion of Appendix VIII," - G. Svensson and G. Wahl, SSPA Committee VII. Maneuvering

1. Definitive Maneuvers

"Reversed Spiral Test Analogy," - K. Nomoto, OU

"Modified Zig-Zag Maneuver," - M. Fujin() and S. Motora, UT "Method of Defining and Measuring the Maneuverability of Ships," - K. Nomoto, OU and N.H. Norrbin, SSPA (App. I)

a)

b)

-a)

c)

d)

-a).

-C-18-69 31

2. Maneuvering in Restricted Waters: Test, Theory and Facilities

"Water Forces acting on Ship in Oblique Flow in Restricted Waters," - T. Tuji, N. Mori and Y. Yamanouchi, SRI

"New Results related to Restricted Water Maneuvering," -N.H. Norrbin, SSPA (App. II, Part 1)

"Japanese Studies of Restricted Water Maneuvering," - S. Motora, UT (App. II, Part 2)

"Test Techniques and Prediction Methods in Restricted Waters," - N.H. Norrbin, SSPA (App. II, Part 3)

"New Tank for Studying the Maneuverability of Ships," -G.A. Firsoff, E.P. Nikolaev and R.J. Pershits, KSRI

3. Effect of Wind of Maneuverability

"Experimental Measurements of Effect of Wind," - Y. Takaishi and T. Tsuji, SRI

"Calculated Effect of Wind on Maneuverability," - A. Ogawa, SRI

4. Mathematical Simulation of Maneuvers

"Analysis of the Pull Out Maneuver," - N.H. Norrbin, SSPA "Approximate NonLinear Analysis of Steered Motions," -K. Nomoto, OU

"Modelling the Helmsman," - A.M. Stuurman, RNN

5. Rudder Hydrodynamics

a) "Effect of Temperature and Reynolds Number on Rudder Hydrodynamics," - M. Rakamaric and J. Korlevi; BI

6. Correlation of Maneuvering Results, Models to Full Scale, Different

Model Techniques, Different Facilities

"First Analysis Phase of Free Model Maneuvering Tests," -A. Suarez, DL (App. III, Pt 1)

"Final Analysis of ITTCCaptive Model Test Program," -M. Gertler, NSRDC and R.K. Burcher, AEW (App. III, Pt 2) "Correlation between Model Tests and Ship Trials Data," -A.J. Vosper, AEW (App. IV)

"Scale Effects on Maneuverability," - H. Thieme, ISU (App. V) a) ) c) ) -a) -b) -)

Committee VIII. Presentation of Results

1. Contributions to the Presentation Committee

"On Propulsive Performance Measures of Unconventional Devices and Ships," - H.M. Chang, NSRDC

"Proposed Standard Procedure for Presentation of Regression Functions," - M. Schmiechen, VWS

"Representing Test Results of Propellers," - H. Tanaka, DA "Contribution to Committee Report," - E. Castagneto, IAN

a

C-18-69 33

APPENDIX C

Alphabetical Key to Organizations Participating in the Executive Committee or in the Technical Sessions of the 12th ITTC

AEW

Admiralty Experiment Works Haslar

Gosport, P012 2AG, Hampshire, United Kingdom AICN

Asociacion de Investigacion de la Construccion Naval Escuela T.S. de Ing. Navales

Ciudad Universitaria Madrid-3 Spain

BHC

Experimental and Electronic Laboratories British Hovercraft Corporation

Osborne Works

East Cowes, Isle of Wight, United Kingdom

BI Brodarski Institute W. Froude 1 P.O. Box 02-237 Zagreb, Yugoslavia BS RA

The British Ship Research Association Wallsend Research Station

Wallsend, Northumberland, United Kingdom CEH

Canal de Experiencias Hidrodinamicas El Pardo, Madrid, Spain

CET

Centro Esperienze.idrodinamiche Maricominav, Rome, Italy

--.. aid

CIT CTH DA DL DSL FA GDQ HI HIJ

California Institute of Technology Pasadena, California 91109, USA

Inst. for Skeppshydromekanik Chalmers Tekniska H8gskola S-402 20, G8teborg 5, Sweden

Defense Agency Tokyo, Japan

Davidson Laboratory

Stevens Institute of Technology 711 Hudson Street

Hoboken, N.J. 07030, USA

Delft Shipbuilding Laboratory Technological University Mekelweg 2

Delft, The Netherlands

Fishing Boat Laboratory Fisheries Agency

Kachidoki-5-5-1

Chuo-Ku, Tokyo, Japan

General Dynamics/Quincy U.S.A. Division

97 East Howard Street, Quincy, Massachusetts 02169, USA

Hydronautics, Inc. Pindell School Road Howard County

Laurel, Maryland 20810

Harima Industries Japan

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HSEC

Hitachi Shipbuilding& Engineering Co. Ltd. 47, 1-chome

Edobori, Nishi-ku, Osaka, Japan HSV

Hamburgische Schiffbau-Versuchsanstalt 2 Hamburg 33

Bramfelderstrasse 164 Germany

Hydro-og Aerodynamisk Laboratorium Hjortekaersveg 99

DK-2800, Lyngby, Denmark

Istituto di Architettura Nayale Universita degli Studi

P. le V. Tecchio 80125 Naples, Italy

Ishikawajima-Harima Heavy Industries Co. Ltd. Shin-Nakahara-machi

Isogo-ku, Yokohama, Japan

Iowa Institute of Hydraulic Research State University of Iowa

Iowa City, Iowa 52240, USA

Technion

Israel Institute of Technology Hydraulics Laboratory

Technion City, Haifa, Israel INS EAN

Istituto Nazionale per Studi ed Experienze di Architettura Navale

Via Corrado Segre 60 Rome, Italy HyA IAN IHHI II HR IIT