Proceedings of the 7th International Conference on Ship Hydrodynamics, Scandinavia, 20-31 August 1954

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STATEN S SKEPPSPROVNINGSANSTALT

(PUBLICATIONS OF THE SWEDISH STATE SHIPBUILDING EXPERIMENTAL TANK)

Nr 34 GOTEBORG 1955

SCANDINAVIAN TOWING TANK CONFERENCE

PUBL. NO. 1

SEVENTH

INTERNATIONAL CONFERENCE

ON

SHIP HYDRODYNAMICS

SCANDINAVIA, 20-31 AUGUST, 1954

INTERNATIONAL COMMITTEE REPORTS

DISCUSSIONS AND CONCLUSIONS

EDITED BY

ti. F. NORDSTROM AND HANS EDSTRAND

To be purchased, either directly or through any bookseller, from GUMPERTS FORLAG, GOTEBORG, SWEDEN

Forts. A ornslagets 3:dje sida [Continued on inside back cover]. FRAN

STATENS SKEPPSPROVNINGSANSTALT

Nr Pris Kr.

Statens Skeppsprovningsa,nstalt (Historik, allmän planering, kostnader;

Principer, allmAn beskrivning; NAgra synpunkter pa byggnadsproblemet;

RAnnans konstruktion och utförande; Den instrurnentella utrpstningen; Den elektriska utrustningen; Uppgifter, organisation) [Summary in

Eng-lish], av HUGO HAMMAR, H F NORDSTROM, M. WERNSTEDT, SVEN HUL-TIN, R. RöDSTROM, KARL TISELIUS, 1942 5: Förstik med fiskebittsmodeller [Tests with Fishing Boca 1VIodels, Summary

in English], av H. F. NORDSTROM, 1943 2:

Experiments with Bulbous Bows, av ANDERS LINDBLAD, 1944 2:

Propellers with Adjustable Blades, av H. F. NORDSTROM, 1945 Nogle Praktiske og Teoretiske Undersogelser orn Modelpropellere [Some Practical and Theoretical Investigations of Model Propellers, Summary in

English], av JORGEN MARSTRAND, 1945

The Effect of the Air Content of Water on the Cavitation Point and upon

the Characteristics of Ships' Propellers, av HANS EDSTRAND, 1946 4:

Modellförsök med en färja [Model Tests with a small Ferry, Summary in

English], av H. F. NORDSTROM och E. FREIMANIS, 1947 1: 50

Further Experiments with Bulbous Bows, av ANDERS LINDBLAD, 1948 2:

Screw Propeller Characteristics, av H. F. NORDSTROM, 1948 2-Some Systematic Tests with Models of Fast Cargo Vessels, av H. F.

NORD-STROM, 1948 3:

II. The Electrical Equipment of the Swedish State Shipbuilding Experimental

Tank, av KARL TISELIUS, 1949 4:

The Resistance of a Barge with the Bottom Air Lubricated, av HANS

EDSTRAND och KAGNAR RöDSTROM, 1949 2:

Medstromskoefficientens Afhmngighed al Rorform, Trim og Hkbolge [The Dependence of Wake on Shape of Rudder, Trim. and Stern Wave,

Summary in English], av SVEND AAGE HARVALD, 1949 5:

Further Tests with Models of Fast Cargo Vessels, av H. F. NORDSTROM,

1949 2:

Cavitation Tests with Model Propellers in Natural Sea Water with Regard

to the Gas Content of the Water and its Effect upon Cavitation Point

and Propeller Characteristics, av HANS EDSTRAND, 1950 7:

Systematic Tests with Models of Cargo Vessels with 4 = 0.575, av

H. F. NORDSTROM, 1950 2: 50

Propulsion Problems Cormected with Ferries, av H. F. NORDSTROM och

HANS EDSTRAND, 1951

Model Tests with Turbulence Producing Devices, av H. F. NORDSTROM

OCh HANS EDSTRAND, 1951 10:

Some Tests with Models of Small Vessels, av H. F. NORDSTROM, 1951 5:

Model Tests with Icebreakers, av H. F. NORDSTROM, HANS EDSTRAND

FRAN

STATEN S SKEPPSPROVNINGSANSTALT

(PUBLICATIONS OF THE SWEDISH STATE SHIPBUILDING EXPERIMENTAL TANK)

Nr 34 GOTEBORG 1955

SCANDINAVIAN TOWING TANK CONFERENCE

PUBL. NO.

SEVENTH

INTERNATIONAL CONFERENCE

ON

SHIP HYDRODYNAMICS

SCANDINAVIA, 20-31 AUGUST, 1954

INTERNATIONAL COMMITTEE REPORTS

DISCUSSIONS AND CONCLUSIONS

EDITED BY

H. F. NORDSTROM AND _{HANS EDSTRAND}

To be purchased, either directly or through any bookseller, from GUMPERTS FORLAG, GOTEBORG, SWEDEN

\c3z4-_3_

MEDDELANDEN

111

knit

Front Row Mr. F. S. Burt Mr. M. St. Denis Dr. A.A. Tovvnsend Mr. T. Stephanson P rof. E. G. E. Hogner Prof. J. K. Lunde Sir Thomas H. Havelock Dr. F.H. Todd

Prof. L. Troost

Prof. F. Horn

Dr. . K. S. M. Davidson Prof. G. Kempf Dr. H. F. Nordstrom Mr. M. L. Acevedo Dr. J. F. Allan Prof. C.W. Prohaska Prof. J. J. Rahola Dr. H. Edstrand Dr. G. Vedeler Dr. R. W. L. Gawn

Prof. E.V. Telfer

Prof. M. Yamagata

Prof. S.J. Palmer

f e

Delegates outside Statens Skeppsprovningsanstalt, GOteborg, Sweden

Key to Photograph (Reading from Left to Right)

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Second Row Mr. C.D. Lövsta Mr. J. R. Getz Mr. L. Mazarredo Mr. D.I. Moor Mr. L. Pehrsson Mr. E.G. M. Petersohn R. Adm. J. Dieudonné Dr. K.E. Schoenherr Prof. G. S.J. Aertssen Mr. K.C. Barnaby Dr. J.D. van Manen Dr. H. W. Lerbs Prof. A. M. Robb Mr. W.P. Walker Captain W.H. Leahy Mr. P. R. Crewe Mr. E.S. Turner Dr. V. G. Szebehely Prof. H. Rouse Prof. H. Amtsberg Dr. S. Schuster Mr. K. Taniguchi Preface

At the Sixth International Conference of Ship Tank Superintendents in Washington, 1951, it was decided that the seventh conference should be held in Scandinavia during 1954.

A Scandinavian Management Committee (S. M. C.) was formed to organize this seventh conference. The S. M. C. decided to hold the conference in Oslo (Norway), Goteborg (Sweden) _{and KfSbenhavn} (Denmark). For many reasons it seemed desirable to change the previous name of the conference. The S.M.C. therefore proposed to the Conference Standing Committee a change of the name to

"International Conference on Ship Hydrodynamics (Formerly Int. Conf. of Ship Tank Superintendents)"

and this name was adopted by the Standing Committee and was also thoroughly used during the conference.

The present Conference, however, did not accept this name, but adopted instead the name "International Towing Tank Conference"

for the future conferences.

In order to avoid confusion the name "Seventh International Conference on Ship Hydrodynamics" has been used in the headings and in the text of this publication.

Seventeennations were represented at the Conference. All delegates were personally invited. In total 77 delegates and 4 visitors attended the Conference. They were accompanied by 44 ladies and_{3 children.} In this publication are recorded, in full, the technical _{committee reports and the contributions to} the formal discussions. The free discussions which followed the prepared contributions at each

session, have been given in summarized forms, revised and approved by_{the secretaries of the} respective sessions.

It is stressed that, in accordance with the prescriptions _{given in the Second Circular, published in} January 1954, all contributions have been assumed to be in their final form for printing. This being so, no responsibility can be accepted for any inconsistencies in nomenclature or for original printing errors in the contributions. Thus it is to be expected thata certain amount of

non-uni-21100 e D. S. A. }Is#1.4.1d

P404; '0.'15. A. van Lammeren

aft/W.' A.E erson

VC:010'. Mr.

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Dr. JArre. Conn

Mr. N. C. Astrup Mr. R. H. S. ROcistrOm Mr. K. S. Larsen

Dr. J. Marstrand

Mr. S. T. Mathews Mr. H. B. Lindgren Mr. Y.K. Vuori Mr. J. -E. Jansson Prof. M. Abkowitz Mr. C. H. Hancock Prof. H. Voelker Prof. S. ilovie Dr. E. Castagneto Mr. A. B. Murray Dr. O. Grim Mr. L. Kretschmer

Prof. L.P. Maillard

Prof. J. L. Taylor Prof. G. Weinblum Mr. A. Voll Dr. G. Hughes

Mr. J. F. Fatur

Dr. J. Balhan

formity in nomenclature will be evident, since contributions come from various authors using different symbols for the same quantity. However, in some cases, even the same author has not been strictly consistent.

The Conference has been economically supported by the Governments in Denmark, Finland, Nor-way and Sweden. The S. M. C. further acknowledges with thanks the gene-ous support contributed

by:

Det Norske Ventas A/S Akers Mek. Verksted

A/S Fredriksstad Mek. Verksted, Fredrikstad A/S Framnaes Mek. Vaerksted, Sandefjord Kaldnes Mek. Verksted A/S, T6nsberg A/S Bergens Mek. Verksteder, Bergen A/S Rosenberg Mek. Verksted, Stavanger Nylands Verksted

Marinens Hovedverft, Horten

Kristiansands Mek. Verksted A/S, Kristiansand S A/S Moss Vaerft & Dokk, Moss

Sarpsborg Mek. VerkstedA/S, Gre&ker Glommens Mek. Verksted A/S, Fredrikstad A/S Langesunds Mek. Verksted, Langesund A/S Pusnes Mek. Verksted, Arendal Haugesund Mek. Verksted A/S, Haugesund A/S Stord, Stord

A/S Trondhjems Mek. Verksted, Trondheim Trosvik Verksted A/S, Brevik

Drammen Slip & Verksted, Drammen Porsgrunds Mek. Verksted, Porsgrunn A/S Seutelvens Verksted, Fredrikstad Norges Rederforbund

Den Norske Amerikalinje A/S Den Norske Ingeni6rforening

AB Karlstads Mek. Werkstad Kristinehamn

The City Council of Göteborg Sveriges Varysindustriförening Statens Skeppsprovningsanstalt

Tekniska Samfundet

Eriksbergs Mek. Verkstads AB AB G6taverken AB Lindholmens Vary Mölnlycke Vg.fveri AB Angfartygs AB Tirfing Oslo 16tebo rg

Danmarks tekniske H0jskole Dansk Ingeni0rfo rening

A/S Burmeister & Wain Skibs- og Maskinbyggeri Helsingr Skibsvaerft 11, Maskinbyggeri A/S, He1sing4r Den Kongelige Porcelainsfabrik

Tekrdllinen korkeakoulu - Tekniska HOgskolan Tekniikan EdistamissaatiO - Stiftelsen ftir Teknikens

Beframjande Oy Valmet Ab

Oy Tampella Ab, Tampere

In close connection with the Conference, and under the sponsorship of Den Norske IngeniOrfore-nings Skipsgruppe and Det norske Ventas, general lectures within the field of the conference were held in Oslo on the 19th - 20th August. The lectures and the following discussions_are published separately by the Norwegian Ship Model Basin (Slcipsmodelltanken), Trondheim.

List of Delegates

Country and Name _Address

Austria

Kretschrner, Dipl. Ing. Leopold _{Schiffbautechnische Versuchsanstalt, Wien 20} Belgium

Aertssen, Prof. Gregoire S.J. 41 Courte rue d'Argile, Antwerp Canada

Mathews, Mr. Sydney Thomas Turner, Mr. Ernest S. France

Dieudonné, R. Adm. Jean Maillard, Prof. Louis Paul Germany

Amtsberg, Prof. Dr. Ing. Hans Grim, Dr. Ing. Otto

Horn, Prof. Dr. Ing. Fritz

Kempf, Prof. Dr. Ing. Grinther Schuster, Dr. Ing. Siegfried Weinblum, Prof. Dr. Ing. Georg Great Britain

Allan, Dr. James F.

Barnaby, Mr. Keruieth Coules Burrill, Prof. Lennard C.

Burt, Mr. Francis Stanley Conn, Dr. J. F. C.

Crewe, Mr. Peter Rowland Emerson, Mr. Arnold Ferguson, Mr. John Miller Gawn, Dr. Richard William Lewis Havelock, Sir Thomas Henry Hughes, Dr. George

Moor, Mr. David Ian Palmer, Prof. Sidney John

Robb, Prof. Andrew Mc. Cance Smith, Dr. Stanley Livingston Telfer, Prof. Edmund Victor Townsend, Dr. Albert Alan Walker, Mr. William P. Wigley, Mr. Cyril

K0benhavn

Helsinki

National Research Council, Montreal Rd, Ottawa 2. Ontario

National Research Council, Montreal Rd, Ottawa 2, Ontario

4 Square Latour Maubourg, Paria (7)

Bassin d'Essais des Carènes, 6 Brd Victor, Paris (15) Technische Universitat, Berlin- Charlottenburg

Berlinertor 21, Hamburg 1 Laehrstr. 28, Berlin-Zehlendorf Berlinertor 21, Hamburg 1 Uhlandstr. 54/55, Berlin W. 15 Berlinertor 21, Hamburg 1

National Physical Laboratory, Teddington, Middlesex Abbeymead, Hamble, Southampton

34, Elmfield Road, Gosforth, Newcastle-on-Tyne 17, St. Leonards Road, Claygate, Surrey

15, Radnor Road, Twickenham, Middlesex Rornola, High Street, Freshwater, Isle of Wight 34, Grosvenor Road, Newcastle-on-Tyne 2 23, Earlbank Avenue, Scotstoun, Glasgow W. L. Admiralty Experiment Works, Haslar, Gosport, Hants 8, Westfield Drive, Gosforth, Newcastle-on-Tyne 3 National Physical Laboratory, Teddington, Middlesex Ship Model Experiment Tank, St. Albans, Herts Royal Naval College, Greenwich, London S. E. 10 The University, Glasgow

ChesterfieldGardens, Curzon Street, London W 1 54, Ewell Donns Road, Ewell, Surrey

209, Gilbert Road, Cambridge

Wm. Denny fk Brothers Ltd., Leven Shipyard, Dumbarton Charterhouse Square, Plat 103, London E. C. 1

Holland

Balhan, Dr. Jacques

van Larnmeren, Prof. Dr. W. P. A. van Manen, Dr. Jan Dirk

India

Voelker, Prof. Dr. Ing. Helmut Italy

Castagneto, Dott. Ing. Emilio Japan

Taniguchi, Kogakushi Kaname Yamagata, Prof. Dr. Eng. Masao Jugo-Slavia

Silovi6, Prof.Ing. Stanko

Spain

Acevedo, Mr. Manuel L. Mazarredo, Mr. Luis United States

Abkowitz, Prof. Martin

Davidson, Director Kenneth S. M. Hancock, Director Clifford Harold Leahy, Captain William H. Lerbs, Dr.Ing. Hermann W. Murray, Asst. Dir. Allan B. Rouse, Prof. Hunter

Schoenherr, Dr. Karl Ernest St. Denis, Naval Architect Manley Szebehely, Dr. Victor G.

Todd, Dr. Frederick H. Troost, Prof. Laurens

Scandinavia

Denmark

Harvald, Dr. Techn. Svend Aage Larsen, Civ. ing. Kai Stundsig Mar strand, Dr. Techn. JOrgen Prohaska, Prof. Dr. Techn. C. W. Finland

Jans son, Techn. Lic. Jan-Erik Rahola, Prof. Dr. Sc. Jaakko J. Vuori, Dipl. ins. Y rjana Kristian Norway

Astrup, Sen. Sc. Off. Nils Chr. Getz, Overing. Jan Reidar Lunde, Prof. Johannes K. Morgenstierne, Lab. ing. Gert Taylor, Prof. John Lockwood Vedeler, Dr. Georg

Voll, Lab.ing. Arne Sweden

Edstrand, Dr. Hans Hogner, Prof. Einar G. E. Lindblad, Prof. Anders Lindgren, Civ. ing. Hans Bertil Liljekvist, Captain P. Gösta V. NordstrOrn, Dr. H. F.

Oldenburg, MarinOverdir. Ivar Pehrsson, Civ. ing. Lennart Petersohn, Civ. ing. Erik G. M. ROdstrOm, Civ. ing. Ragnar H. S.

Nieuwelaan 76, Delft Haagsteeg 2, Wageningen Haagsteeg 2, Wageningen

Indian Institute of Technology, Kharagnur E. Ry. Vasca Nazionale, Prati di S. F tolo, Roma

Motoharacho, 1 - 371, Nagasaki-shi

Faculty of Engineering, University of Tokyo, Bunkyo-ku,

Tokyc

Karadziceva 1, Zagreb

Canal de Experiencias Hidrodinimicas, El Pardo, Madrid Canal de Experiencias Hidrodinimicas, El Pardo, Madrid 79 Templeton Parkway, Watertown, Mass.

1201 Park Avenue, New York 28, N. Y. Newport News Shipbuilding and Dry Dock Co.

Nevrport News Va. 116, Sumrnerfield Road, Chevy Chase 15, Md. David Taylor Model Basin, Washington 7, D.C. 246, Gramercy Place, Glen Rock, N. J.

Iowa Institute of Hydraulic Research, State University of Iowa, Iowa City, Iowa

712 Wilson Boulevard, Mishawaka, Indiana David Taylor Model Basin, Washington 7, D. C. David Taylor Model Basin, Washington 7, D. C. David Taylor Model Basin, Washington 7, D.C. 420 Memorial Drive, CambridLe 39, Mass.

Solvaenget 22, Kgs. Lyngby Ibstrupvaenget 2, Gentofte

SpSn der sirSve j 36, Gentofte

Juul Steens allé 9, Hellerup Albertsgatan 21 C, 17 Helsingfors Tekniska HOgskolan, Helsinki Eerikin_k. 12 C, Turku

Persaunet Hageby 21, Trondheim

Skipsteknisk forskningsinstitu,t, Innherredsveien 7 D, Trondlieim

Skipsmodelltanken, Trondheim Skipsmodelltanken, Trondheim

Norges Tekniske HOgskole, T rondheim Gullerasvei 3, Slemdal, Oslo

Skipsmodelltan.ken, Trondheim Raketgatan 10, GOteborg C bregrundsgatan 6, Stocicholm Geijersgatan 5, GOteborg S

Statens Skeppsprovningsanstalt, Göteborg 24 K. Marinförvaltningen, Stockholm 80 Gibraltargatan 14, Göteborg C K. MarinfOrvaltningen, Stockholm 80 Lambergsgatan 27 A, Karl stad

Flygtekniska FOrsöksanstalter, Ulvsunda 1 KutterspS.nsgatan 10, GOtebori

Name Address Visitors

Fatur, Mr. J. F. Lovstad, Mr. C.D.

Stephanson, Tekn.lic. Torsten Warholm, Civ. ing. Axel O.

Opatija, Dra/ica 4, Jugo-Slavia

Skip steknisk for skningsinstitutt, Trondheim, Norway Karlstads Mek. Werkstad, Kristinehamn, Sweden Statens Skeppsprovningsanstalt, Goteborg 24, Sweden

Committees,

which organized and prepared the Conference Scandinavian Management Committee Chairman: Dr. H. F. Nordstrom (Sweden)

Dr. C. W. Prohaska (Denmark) Prof. J. J. Rahola (Finland) Dr. G. Vedeler (Norway) Secretary: Dr. H. Edstrand (Sweden)

Conference Standing Committee Chairman: Dr. H. F. NordstrOm

Prof. G. Kempf Mr. M. L. Acevedo Dr. K. S. M. Davidson Vice Adm. E.G. Barrillon Dr. J. F. Allan

Secretary: Dr. H. Edstrand Conference_ Secretary

Dr. H. Edstrand

Conference Technical Committees

Subjects 1 and 5. Scale Effects on Propellers and on Self-Propulsion Factors Chairman: Dr. J. F. Allan

Mr. R. B. Couch

Prof. W. P. A. van Lammeren Prof. E.V. Telfer

Prof. C. W. Prohaska

Subjects 2 and 4. Skin Friction and Turbulence Stimulation Chairman: Dr. F. H. Todd

Dr. G. Hughes Prof. J. K. Lunde Dr. K. S. M. Davidson Prof. G. Kempf

Subject 3. Comparative Propeller Tests Chairman: Dr. R. W. L. Gawn

Prof. W. P.A. van Lammeren

Mr. L Pehrsson

Prof. L. C. Burrill Dr. H.W. Lerbs

Subject 6. Seagoing Qualities of Ships Chairman: Dr. G. Vedeler

Mr. W.P. Walker Mr. C.H. Hancock Captain R. E. Brard

Subject 7. Presentation of Resistance and Propul3ion Data Chairman: Capta.in H. E. Saunders

Mr. M. L. Acevedo Mr. J.M. Ferguson Dr. H. F. Nordstrom Dr. J. F. C. Conn

Programme

The table on page 9 gives an abstract of the Conference Programme .ncluding Programme of the preceding Meeting in Oslo.

Special programmes for ladies were arranged in Oslo, Kristinehamn, Göteborg, Malmo and KOenhavn.

Programrne including Lectures in Oslo Place Date Morning Afternoon Oslo Thursday 19 August Opening of Meeting Weinblum: Recent Progress in Theoretical Studies on the Behavior of a Ship in a Seaway Szebehely: On Slamming

Lunch on board the In. s. "Oslofjord" by invi- tation of the Norwegian America Line Townsend: On Turbulent Frictional Resistance Dinner by invitation of the Norwegian Reception Committee

Friday 20 August

Inui: On Japanese Progress in Calculation of Wave Making Resistance Hogner: A Complementary Method for Evaluating Ship Wave Resistance Theodorsen: On Propeller Theory

Lunch by invitation of the Norwegian Ship

-owner's Association Visit to Viking Ships, Kontiki Raft and Arctic Exploring Ship "Fram" (with ladies)

Friday 20 August

Meetings of the Technical Committees

Kristinehamn Saturday

21 August

Visit to the Cavitat on Tunnel

Lunch by invitation of the Karlstads Mek. Werkstad

Götebo r g

Sunday 22 August

Opening Ceremody Reception by invitation of the City of Goteborg

Monday 23 August

Subjects 2 and 4 (Skin Friction and Turbulence Stimulation)

Tuesday 24 August

Subject 3 (Comparative Propeller Tests)

Visit to the Statens Skeppaprovningsanstalt

Performance in the Cabaret Hall at Liseberg Amusement Park. Supper by invitation of the Statens Skeppsprovningsanstalt and Tekniska Samfundet

Wednesday 25 August

Subjects 1 and 5 (Scale Effects on Propellers and

on Self-Propulsion Factors)

Thursday 26 August

Subject 6 (Seagoing Qualities of Ships)

Lunch by invitation of AB Götaverken and Eriksbergs Mek. Verkstads AB

the Götaverken' e Ship Yard

Visit in two groups to

the Eriksberge's Ship Yard

Dinner by invitation of the Swedish Shipbuilders' Association

Friday 27 August

Subject 7 (Presentation of Resistance and

Propulsion Data)

Malmti/ KObenhavn Saturday 28 August

Visit to the Kockurn's Ship Yard, Malmo

Lunch by invitation of the Kockum's Ship Yard, Malmo

Reception in KObenhavn by invitation of the Minister of Commerce, Industry and Shipping at Christiansborg Castle Fireworks at the Tivoli

Kyibenhavn

Sunday 29 August

Bus excursion for delegates and ladies to Kronborg Castle and Frederiksborg

Castle

Tea at Marienlyst

M da

ony

30 August

Meetings of the Technical Committees Lunch by invitation of the Dansk IngeniOr- forening Appointment of committees. Conference business

Tuesday 31 August

Summaries and Decisions

Quick lunch by invitation of the Danmarks Tekniske 1-10jskole

Address of Welcome

by the Chairman of the Scandinavian Management Committee, Dr. H. F. Nordstrom Mr. Vice Chairman of the City Council,

Ladies and Gentlemen,

It is a great pleasure to me to extend to you, on behalf of the Scandinavian Management Committee, a hearty welcome to the proceedings of the Seventh International Conference on Ship Hydrodyna-mics here in Goteborg (or Gothenburg as its international name is). It is a great honour to us that the conference should be held in Scandinavia this time. I should like to include in that

wel-come my own personal good wishes and I shall be very happy to show you our experiment tank here in GOteborg and its facilities.

Seventeennations are represented here today. Some of them have not been represented before and a special welcome is extended to our new colleagues.

One of the grand old men of our science, General Giuseppe Rota, has lied since the last con-ference. The memory of his name and his work will always live among us.

We regret very much that Admiral E. G. Barrillon, Dr. Fr. Gebers, Mr. J. L. Kent and Captain Harold Saunders are not with us today. They were invited as senior workers but have not been able to come.

As the number of member nations has increased, the number of delegstes has naturally also in-creased. This gives us great satisfaction, for although the personal ccntact between the delegates will be somewhat less than in the past, we are sure that our new colleauges will contribute greatly to the value of our work.

This conference is the seventh of its kind. We trace its ancestry from the conference in the Hague in 1933, but it must be remembered that its real origin was the meetirg on "Hydromechanische Probleme des Schiffsantriebs" which was held in Hamburg in 1932.

As you will have noticed, the name of the conference has been changed. This was desirable for many reasons, but the change of name does not imply any change in the character of the con-ference.

For practical reasons only, English has been chosen as the conference language. Unfortunately, this will be a great handicap for all or most of those delegates who do not have English as their mother tongue. It is often observed that it is easier to understand a foreign language when it is presented by a person not using his own mother tongue. Perhaps this rlay serve as a reminder to all English speaking delegates to speak as slowly and as clearly as possible.

The aim of the conference is to discuss all questions connected with ship resistance, ship pro-pulsion and ship performance, with particular reference to investigations carried out in experi-ment tanks and cavitation tunnels. Although we know a great deal about these questions, there are still many unexplained facts and many problems awaiting solution. I have just mentioned that this is the seventh such conference. In looking back over the results of the previous six conferences, we are entitled - I believe - to state that step by step we have made satisfactory progress. I am glad to say that the research within the highly specialized field of our conference has been very intensive since the last conference in Washington. Especially, we can note creditable attempts to elucidate the problems of friction and frictional resistance

When the current problems are solved, new problems will appear as in all research work. We cannot see the end, but we are convinced that we are on the way towards a better understanding of all questions connected vrith ship resistance, ship propulsion and sh-p performance.

Finally, I should like to remind you of the proposal made at the conference in Washington for a Memorial to William Fraude. I am quite sure that we have all noticed with satisfaction the ini-tiative taken since then by the Institution of Naval Architects. As you must already know, the unveiling of the William Fraude Memorial will take place in Torquay next month (21st September) in coruiection with the Autumn Meeting of the Institution. We shall then have an excellent oppor-tunity of making a pilgrimage to Torquay, the birthplace of our science, our Mecca.

Ladies and Gentlemen,

L Subjects i and 5

Scale Effects on Propellers and on Self-Propulsion Factors

Chairman: Dr. K. S. M. Davidson

Reporter: Dr. J. F. Allan

Secretary: Prof. W. P. A. van lammeren

Report

This subject combines Items 1 and 5 of the Sixth Conference in Washington.

Having regard to the conclusions stated by that Conference under these items the following may be taken to indicate the field of interest of the Committee.

1. It is possible by the use of available model facilities and analysis methods to design ship propellers and predict performance with practical accuracy, but more lcnowledge of scale effects in propellers and propulsion factors is required.

2. Investigations along the following lines are indicated: Experiments with propeller geosims.

Experiments with blade sections at high Reynolds numbers. Investigations of surface roughness effects on the foregoing.

Study of the extent of laminar flow and the effect of turbulence stimulation on the foregoing.

Experiments with self-propelled geosim series to cover a wide range of ship types. Experiments with model propellers operating behind solids of revolution, including pressure and wake velocity measurements, on various scales.

3. Development of theoretical approaches to the subject.

4. Comparative study of parallel work in the fields of hydraulic machinery.

5. Since the scale effects under discussion are all of small magnitude, emphasis is given to the need for the utmost accuracy in geometrical details of hull and propeller, in the control of test conditions and in measurements and observations, both model and full-scale. 6. Standardisation of methods of carrying out self-propulsion experiments is highly desirable. A meeting of the Committee was held in Wageningen, Holland, in September, 1952, when reports were given by the members on work on hand in their respective areas. These reports referred to research on hull model series and propeller model series and also to plans for more extensive and large-scale research in several directions.

It was agreed that the results of these various researches when they become available will be of great value in relation to the problems before the Committee. In the meantime itwas decided to collect information on details of self-propulsion methods in use in various establishments, and to arrange for these establishments to take part in a co-operative self-propulsion test on an accepted design. The design subsequently adopted for this work was the

"Victory" Ship which is the basis of the extensive research programme being carried out by the N. S. P.

Table 1 summarises the position as regards self-propulsion methods so far a, information was received. Apart from the question of the method used for surface friction correction (a major issue but covered by another Committee)., there is the British method of cove ring a range of thrust loading by a number of spots at each speed of advance and the Continental method of single

spots at one selected loading at a larger number of speeds. The difference is not fundamental but the British method has the advantage that subsequent analysis can be made at different loading if

required.

The great majority of tanks use the thrust identity basis for wake determination, but "open" water propeller tests are sometimes made at constant speed and sometimes at constant R. P. M. At Haslar and Brown's the self-propulsion test is used to obtain the hull fa :tors only and large-scale open propeller data are used to calculate efficiency. This method helps to reduce propeller scale effect, which is an advantage especially in fine-lined twin-screw ships where the wake is small and wake scale effect is therefore unimportant. The case is different for full cargo ships. The particulars of the Victory Ship used for the comparative tests are:

Length B. P. 436.5 ft. (133.0 m.)

Moulded breadth 62.0 ft. (18.90 m.)

Moulded draft 28.0 ft. ( 8. 53 m.)

Extreme ciisplacement 14,922 tons S.W. Level trim. Propeller diameter 20. 5 ft. (6.25 m. ) No. of blades 4 Pitch, max. 22.9 ft. (6. 8 m.) Pitch, mean 22.5 ft. (6.16 m.) B. A. R. 0.497

The same model propeller was used in the following tanks: Nos. 1,

2, 4, 7,

11, 13 and 15. Tables 2 to 5 and Figs. 1 to 5 summarise the results of the self-propulsion tests on the Victory Ship model. It should be noted these are calculated on the same basis throughout, so that the differences are not due to variations in method of test or analysis.

Table 2 and Figure 1 show the comparison of E. H. P. (Froude) and © (Froude) respectively. There is agreement within ± 2% between most of the results on a 1/23 or 1/24 scale, but there are several outstanding exceptions. On a Froude S. F. C. basis one would expect the small model result to give a high EHP and in this respect No. 9 result is odd.

Figure 2 shows the results of the 1/23 and 1/24 scale models plotted on a function of the ratio cross section of model to cross section of tank, and there is a definite indication of same in-fluence from this factor.

Figure 3 shows the resistance coefficient Ct

-2

plotted on a bas, of Reynolds number and s v

compared with the slope of the Schoenherr line. Some of the results on a 1/24 scale have been omitted for the sake of clarity. In this plot and in Table 2 and Figure 1 the No. 16 result is very high. It may be argued that these results indicate a rather steeper slope in ternis of Reynolds number than that of the Schoenherr line.

Tables 3 and 4 show the wake and thrust deduction fractions respective: f, and the agreement among most tanks is good. It should be noted that the results given are all for similar scales. The low wake and thrust deduction of No. 11 is probably due to the method of test which was the old

Froude system with the propeller carried independently. The low thrust deduction in No. 10 can-not be explained.

Figure 4 shows a comparison of Q. P. C. from the various tanks, and the variation of the results is about twice that of the resistance results. It is a reasonable deduction that this is due to in-accuracy of torque measurement. Figure 5 shows the DHP comparison and indicates the combined effect of the variations in EHP and QPC.

Table 5 shows the comparison of ship RPM deduced from the model tests at the point corre-sponding to ship self-propulsion (Froude S. F. C. ). These are in reasonable agreement but it should be remembered that a 1% discrepancy in RPM gives 3% to 4% discrepancy in power.

These results indicate the extent of agreement among the tanks, and it must be admitted this is not so good as one might expect, especially as regards the QPC. From the standpoint of small

"scale effects" in propeller performance and propulsion factors it is Lndicated that a useful accuracy will only be achieved by concentrating particular projects in one establishment and obtaining the greatest possible accuracy in that establishment.

Table 6. Trial Result of Victory Ship "Bluefield Victory" Displacement: 14,840 ton

Weather: Fine

The trial results of the "Bluefield Victory" given above have been supplied by T. M. B. , and are of

some interest. There is some doubt regarding the exact identity of the lines of this vessel with those used in the foregoing tests but any small differences would not influence the results to a material extent. The 3% allowance for tail shaft losses is a standard N.P. L. practice.

Comparing the D. H. P. of Table 6 with the results in Figure 5, the results for the ship are very low. Using No. 2 as a standard instead of using Froude E.H.P. direct it is necessary to apply a factor 0.84 to 0.88 to obtain agreement with the ship result. This is in line with several results recently obtained in the U. K. for flush welded hulls and published by the Institution of Naval Architects, Spring 1954.

Conclusion

Note is talcen of the large amount of propeller and propulsion scale effect research on hand or planned by almost every establishment. This work is largely unco-ordinated, but even so, when all the results are available and are reviewed against the background of theoretical con-siderations, it should be possible to agree on practical methods of allowing for these scale effects.

Note is taken of the comparison of S. P. methods in use in the various tanks. It is proposed that the Conference considers the possibility of adopting an international standard in this matter. Attention should also be given to the various additional allowances used in predicting actual

ship power.

Note is taken of the results of international self-propulsion tests on the "Victory" Ship models. These results do not show a satisfactory level of agreement, and attention is particularly directed to the indication that torque measurement is the least satisfactory.

To study the small "scale effects" under consideration the highest possible accuracy is essential, both as regards the geometry of the models and the measurements. Particular projects should be concentrated in one establishment.

It is desirable to agree on practical methods of allowing for propeller scale effect, wake scale effect, and if necessary, thrust deduction scale effect. In view of the many researches on hand this should be possible within a reasonable period of time.

It is appreciated that the whole question is allied to the method of allowing for surface friction scale effect and is further influenced by necessary allowance for surface roughness.

James F. Allan

Chairman, International Committee on Scale Effects on Propellers and on Self-Propulsion Factors.

Speed (knots) 11.92 14.63 16.57

S. H. P. (Ford meter) 1732 3444 5768

Table 1. Methods of S. P. Analys s Tank No. Turbulence Device Method of

S.P. Test

Loading Wake

Method of "Open" Tests

Trondheim

1

Trip wire

Continental

Froude S. F. C.

From Thrust Identity

Constant R. P. M. Froude N. P. L. 2 Trip wire British Froude S. F. C. + 10% (C)

From Thrust Identity

Constant Speed Froude Wageningen 3 Trip wire Continental Froude S. F. C.

From Thrust Identity

Constant R. P. M. Froude GOteborg 4 Trip wire Continental Froude S. F.C.

Mean of Thrust and Torque Identities

Constant R. P. M. Froude Paris 5 Nil Continental Froude S. F. C.

From Thrust Identity

Froude

Tokyo

6

Trip wire

Continental

Froude S. F. C. + Experience Factor

Froude Denny 7 Trip wire British Froude S. F. C. + 10% (C)

From Thrust Identity

Constant Speed Froude Madrid 8 Trip wire Continental Froude S. F. C. Froude Stevens Institute 9 Trip wire -Schoenherr Rome 10 Nil Continental Froude S. F. C. Froude John Brown 11 Trip wire British Froude S. F. C.

From Froude and Troost Charts

Froude Ottawa 12 Trip wire -Froude Vickers Armstrong 13 Trip wire British .k. rouge o. r . ,.,.

t

Hull Allowance

From Thrust Identity

Constant Speed Froude Hamburg 14 Sand strips Continental Froude S. F. C. Constant R. P. M. Fronde Haslar 15 Studs British

-From Thrust Identity

From Series Charts

Froude Michigan 16 Trip wire

-From Wheel Data

-Schoenherr T. M. B. 17 Trip wire Continental Schoenherr S. F. C.

From both Thrust and Torque Identities

Table Z. Froude Effective Horse Powers

Table 3. Taylor Wake Fractions

Table 4. Thrust Deduction Fractions

Tank No Model Scale E. H. P. at Speed in Knots

12 131 15 16 17 Trondheim 1 1/24 1660 2370 3320 4100 5270 N. P. L. 2 1/24 1590 2410 3300 4160 5390 Wageningen 3 1/23 ₁₆₂₀ 2370 3300 4190 5330 Goteborg 4 1/24 1650 2430 3290 4170 5300 Paris 5 1/24 1660 2390 3320 4160 5350 Tokyo 6 1/24 1680 2370 3340 4170 5430 Denny 7 1/24 1660 2430 3360 4210 5390 Madrid 8 1/24 1610 2440 3450 4360 5360 Stevens Institute 9 1/80 1650 2480 3310 4230 5540 Rome 10 1/23 1690 2440 3400 4260 5470 John Brown 11 1/24 1710 2420 3370 4260 5520 Ottawa 12 1/30 1700 2500 3480 4300 5420 Vickers Armstrong 13 1/24 1700 2530 3460 4310 5560 Hamburg 14 1/30 1710 2530 3570 4440 5710 Haslar 15 1/24 1770 2550 3520 4360 5620 Michigan 16 1/48 1850 2650 3720 4720 6060 wT at speed in knots Tank No. _{12 131 15 16 17} 1 0.35 0.34 0.33 0.34 0.33 2 0.33 0.33 _{0.32 0.30 0.28} 3 - - - -4 0.31 0.31 0.29 0.29 0.28 5 - - - -6 - - - - -7 0.33 0.32 0.32 0.32 _0.32 8 - _ _{- -} _ 9 - - - - -10 - - - -11 0.27 0.26 0.26 0.25 _0.24 12 - - - -13 _{0.34 0.33 0.32 0.32 0.31} 14 0.34 0.34 0.33 0.34 0.34 15 _{0.36 0.36 0.36} 0.35 0.35 16 -

-Tank No. "t" at speed in knots

12 131 15 16 17 1 0.25 0.24 0.24 0.26 0.26 2 0.23 0.23 0.24 0.25 0.26 3 - - - -4 0.21 0.21 0.23 0.21 0.22 5 6 - - -7 0.22 0.20 _{0.23 0.22 0.23} 8 - - -9 -10 0.16 0.18 0.21 0.20 0.20 11 0.17 0.14 0.15 0.15 0.14 12 - -13 0.28 0.26 0.24 0.23 0.22 14 0.23 0.21 0.21 0.23 0.22 15 0.21 0.18 0.20 0.21 0.21 16 - - -

-ApReJlcli3E

Research Work in Various Establishments Table 5. Ship R.P. M. Deduced from Model Tests corresponding to ship propulsion point with no aLlowance

Establishment N. S. P. Sweden (Göteborg) Denmark Stevens T. M. B. Haslar B. S. R. A. N. P. L. Project

Victory Ship geosims and large- sc le S. P model Victory Ship full-scale tests.

Rhine Tanker series.

Propeller series in hand and large-scale -programme planned.

Proposal to test propeller ahead f Icebreaker. Full-scale tests on Tug.

Small propeller research. Full-scale tests on Tug. Tests on 12 ft. propeller. Propeller geosim tests. Full-scale tests on ship. Tests on 20 inch propellers.

Study of laminar flow on model piopellers Blade section research in air at ligh R. N Laminar flow on model propeller. Propeller geosim tests.

Wake scale effect studies up to high R.N. Tank No. ₁₂ R.P. M. at speed in knots_{131 15 16 17}

1 53 60 67 73 78 2 53 60 67 72 78 3 60 67 72 78 4 53 60 68 73 79 5 - - -6 52 59 67 72 78 7 53 61 68 74 80 8 53 60 67 73 79 9 10 53 61 68 73 79 11 54 60 67 73 80 12 _ _ 13 54 61 68 73 79 14 53 61 68 74 80 15 54 61 69 75 81 16 - -

-FIG. 1.

FROUDE © FOR SHIP

.8 .7 .6 .8 6 .7 o_

.4

_ _ -3 1 A

E

-

0 0

IW"--15

_____---8 4 _ _

r

---.

18 11 12 13 14 15 16 17

SHIP SPEED IN KNOTS 8

.7

FIG.2.

EFFECT OF TANK DIMENSIONS ON RESISTANCE

I TH

O O 24 SCALE MODEL

Th1 _LTH

+ - SCALE MODEL CORRECTED TO a4 SCALE BY SCHOENHERR S.F.0

4 6 8 10 12

MODEL BEAM X MODEL DRAFT _{X 103} TANK WIDTH X TANK DEPTH

..._ tal r,, _{:--. I--}

.

_{_} O o 0 °...1_____.Sl_i 0 t

..,

0

00

0+

I

ll

0

IUIU

t

0

I

0 -u 7 16 18

FIG.3.

MODEL RESISTANCE PLOTTED AS Ct TO BASE OF LOG Re

6.0 5.5 5.0 4.5 3.5 3.0 LO Re s bf C k,

0

d

Illitillilll

.111UPP'

uni

S

CyLU

z.../.?---12 _,.. 13

...,

8 ,... 5? . io 10 . 6.0 61 6.2 6.3 6.4 6.5 6.6 6.7 68 6.9

FIG. 4. QUASI PROPULSIVE COEFFICIENTS

.85 -70 .85 .80 -70 : io 14 11 , 1 13

----

4

,

_,

N _ 12 13 14 15 16 17

2000 2000 2000

FIG.5. ESTIMATED D.H.P.

/.

A:00:17...

A.

...

NKrFrA

..

A

e

A

i'M

,,Ammtwil

.,,,Apic

A

OWE%

wry

A

..

A

t

..

w.

."'

A

ip

12 13 14 15 16 17

Formal Discussion

Dr. J. F. Allan

The Sixth International Conference in 1951 laid emphasis on the necess:ty of a means of visibly demonstrating the type of flow over a propeller blade. Until this was dcne, the interpretation of model screw results in the light of laminar or turbulent flow was rather conjectural. In view of this, a method has been devised at the National Physical Laboratory to give a visual indication of the boundary layer flow.

To demonstrate flow, Gutsche (ref. 1) used a viscous dye in drops and streaks on the blade sur-face, giving patterns of the flow and of separation. Perring at the Fifth International Conference 1948 gave photographs of the effect on oil streaks on a rotating aircraft propeller, and also of a chemical method of indicating the flow whilst in flight. These showed tlat there were areas of laminar flow at the tips on both sides at RT., = 3 million. At the N. P. L. a dissolving chemical (hydroquinone diacetate) was tried but due to the complex velocity variations over the surface the results of tests were impossible to interpret. More successful was an adaptation of the method used in reference 2 of releasing ink streams into the boundary layer. For tests with a propeller, an aqueous solution of dye was exuded from several fine holes drilled in the blade faces. The holes were connected by interior channels to the screw boss and thence by a rotating seal to a dye reservoir above water. By this means the rate of the flow could be controlled whilst it was possible to measure thrust and torque at the same time. The resulting flow patterns produced during a test were observed by means of stroboscopic lighting. Since tle patterns are best formed with the minimum quantity of dye ejected, the amount was regulated by hand for observation of individual holes, thus ensuring that the dye entered the boundary layer only.

The propeller used in these initial trials was a 3-bladed Troost Series B design, diameter 0.75 feet, pitch 0.86 feet, and blade area ratio 0.488. The dye holes were drilled on arcs at 0.3, 0.4, 0.5 and 0.7 radius of the blade and at 10%, 50% and 90% chord from the leading edge. The propeller was tested on the standard N.P.L. open water propeller dynamometer and observations by stroboscopic lighting were made over a range of slips for each.set of constant revolutions, covering 200 to 600 R.P. M.

There were two main types of dye pattern. The more obvious type showed as a plume of dye spreading fanwise across the blade and outwards. This type occurred at all holes at the lowest revolutions, but ceased to form at the outer radii with increased revolutions, but ceased to form at the outer radii with increased revolutions up to 600 R. P. M. These traces observed with a minimum dye flow had distrinct outlines and two traces could overlap. Fig. 1 gives some typical photographs of the dye plumes on the back of the blade, No. 3 showing near the tip a plume cut off by flow acro ss the blade. The second type of flow consisted of a rough-edged narrow trace almost following the helical arc across the blade. It occurred only at the higher revolutions and at the outer radii when a plume would not form. At speeds where normally a particular hole would show a plume, if a suitable trip wire was fixed in front of it, the indication uould cha.nge to a helical trace across the blade and even with reduction of the dye flow to minute amounts, a plume would never form.

It is suggested that the two types of pattern demonstrate the existence of laminar and turbulent flow respectively for this reason amongst others, that with the known differences between the velocity gradients of laminar and turbulent flow in a boundary layer, a mach greater outward flow due to the centrifugal field would be expected of a laminar layer than of a turbulent one, as suggested by Perring. Photograph No. 6 is included to show separation at the root where oil drops on the blade fillet have flowed forward, outwards, and then aft.

Using the above definitions of visual laminar and turbulent flow on the propeller blade, it was apparent that below 300 R. P. M. (Ft, = 0. Z million where Reynolds numoer is calculated usingthe

relative velocity at 0.7 radius) the flow at all holes on the face and back was laminar. Increasing the revolutions up to 600 R. P . M. showed some turbulent flow appearing on the outer half of the back, while the face remained laminar. To stimulate turbulent flovv, a 0.005 inch trip wire

(calculated from the curve in ref. 3) was cemented at 5% chord on the back and face and running from root to tip. This caused transition to occur at a lower R and resulted in the flow on both faces turning from laminar at 200 R. P. M. to turbulent at 400 R. P. M. and upwards.

Observations were also made on the bare screw behind a model hull of bi ,ck coefficient 0.71. Here the blade back showed only turbulent flow, while the face was mainly laminar with some

turbulent flow at the outer radii. As might be expected, this demonstrated the increased incidence of turbulent flow in the "behind" condition as compared with the open, but showed that laminar flow could still exist on the screw of a self-propelled model.

Forces on the model propeller were measured over a range of slips at constant revolutions of 500 R.P.M. both with bare blades and with the 0.005 inch wires on faces and backs The curves are given in Fig. 2 corresponding to 110 of 0.33 million, and show a small i.ecrease in thrust and an

the condition of part turbulence on the back and all laminar flow on the face changed by the wires to turbulent flow on both face and back. A tentative determination of the extra torque due to the wire drag has shown it to be only of a small order and so far has been neglected.

Analysing the results in Fig. 2 by the method given by Lerbs (ref. 4), two points are plotted on the skin friction chart (Fig. 3) corresponding to minimum drag of the screw sections at a Reynolds number of 0.33 million. The lower point gives the bare screw result with laminar flow on the face and part turbulence on the back and lies between the two friction curves. The higher point

represents turbulent flow on face and back of blades and includes the corrections as given by Lerbs for pressure gradient, etc. , and is above the Schoenherr turbulent friction line. Also plotted on the chart are curves of minimum drag of circular back sections of 5% and 10% thickness-chord ratios plotted from results given in R & M 2301. From the typical shape of these curves it may be inferred that in the region of R 0.3 million there was considerable laminar flow and that not until Rn = 4 million could one be fairly certain of full turbulent flow. The relative positions of the two analysis points suggests for the lower one a measure of laminar flow and for the higher point complete turbulence stimulation.

In conclusion, it appears that in normal work with model screws at Reynolds numbers between 105 and 106 there is a large amount of laminar flo..v, but a trip wire will stimulate turbulence above a minimum Rn. In the region of 110 = 105 the analysis of results yielding minimum profile drag coefficients which lie near the turbulent friction curve may give rise to false conclusions since they may possibly be due to laminar flow with separation. Behind a hull, the screw showed more turbulent flow than in open water but as it was not completely turbulent, it suggests that for complete stimulation something more effective than turbulent water ahead of the screw is needed. These remarks concerning a particular propeller are in general agreement with other similar work which is continuing at the Laboratory.

References

Reference 1 F. Gutsche Versuche an umlaufenden Flagelschnitten mit abgerissener Str8mung.

Jahrbuch der Schiffbautechnischen Gesellschaft 1940. Reference 2 J. F. Allan & Effect of Laminar Flow on Ship Models.

J. F. C. Cono Trans. I.N.A. 1950.

Reference 3 Bryant & Control Testing in Wind Tunnels. Garner R & M 2881.

Reference 4 H. W. Lerbs On the Effect of Scale and Roughness on Free-running Propellers.

CD J=c) 8 RPM = 100

J= 0.8

R.P M = 200

)J=08

R = 400

FIG.

1.

BOUNDARY LAYER FLOW ON PROPELL_ER BLADES

® J=0'8

R.PM = 300

® J

1 2 R . P. M = 400

©

= R.P.M 400

FIG.2. SCREW RESULTS WITH & WITHOUT

WIRES

AT 500 R.P.M.

0.8 0.7 0-6 0.18 0.16 0.10 0 035

WITH BARE BLADES

- - WIRES ON FACES &

BACKS

0.030 KQ 0.025 0020 070 075 0.80 0.85 0-90 0.95 10 0.14 KT 0-12

0.015 0.016 0.014 0.012

000

000

FIG.3.

PROFILE DRAG COEFFICIENTS OF

SCREW & CIRCULAR BACK SECTIONS

+

1 I 1 1 % 1 i v .9,

+

v

+ +

1C% 5% THiCKNESS RATIO v t % % \

hiSCREW

\SCREW

II.,

1 WITH WITH TRIP WI BARE BLADES ES % i \

I

.`

Niq

.. ,.? 4.1 os 4 6 8 106 2 3 4 6 8 107 REYNOLDS NumBER CD

000

Professor A. Robb

In the Report on "Reynolds Number for Model Propeller Experiments" presented at the Sixth International Conference Scale Effect is defined as "variation in the value of KT and Kg with change in An of geometrically-similar propellers at consta.nt J or slip value". The definition is satis-factory in so far as it implies that constancy of J value, or of slip, is the extension from geometrical similarity to operating similarity. It is satisfactory also in so far as it associates values of KT and Kowith a speed-dimension relation. It thus implies that results which are not associated with a speed-dimension relation are not properly comparable; it implies that results for 16-inch propellers advancing at 5 knots are not properly comparable with results for 10-inch propellers advancing, at 3 lcnots, and neither set of results is comparable with those for 9.5 inch propellers run at a constant speed of 450 rev, per min. The definition is not, however, satis-factory in so far as the chosen speed-dimension relation is open to question.

By associating constancy of KT and Ko with constancy of Reynolds number the definition implies that constancy of the thrust and torque constants, excluding any correction for scale, should be associated with constancy of the product VD; it is here assumed that the density and the viscosity are constant and that the speed of advance and the diameter are respectively the representative speed and the representative dimension. Is there, however, any evidence to show that the results for a propeller 1.33 ft. in diameter run at 5 knots can conveniently be related to the results for a propeller 0.8 ft. in diameter run at 8.33 knots, the product VD being the same in both cases? Is there even any evidence to show that the results for a 4-ft. aerofoil tested at 20 ft. per sec. can conveniently be related to those for a I-ft. aerofoil tested at 80 ft. per sec?

It iE true that the Committee responsible for the definition of scale effect recommended that several "scale-effect" series of propellers should be tested. The Committee did not, however, submit any details, and it is doubtful if the members appreciated the implications of their

definition and recommendation. For the extensive Taylor series of propellers the product VD was 6.667 in knots and ft. For the Froude propellers the product was 2.369. It is doubtful whether any dynamometer in existence can function at a product of, or much above, 10. On the other hand, for quite a small ship the product VD may be 75, and from that low value the product may range up to about 600. Hence the adoption of the Reynolds speed-dimension relation involves very extensive extrapolation, with attendant doubt.

The very extensive extrapolation to which objection should properly be taken can be avoided if the propeller speeds are proportional to the square roots of the diameters, in accordance with the

Newton Law of Mechanical Similitude. There is here no argument that compliance with the Newton Law is necessarily more important than compliance with the Reynolds number relation. The argument is more simple. It is that compliance with the Newton Law is not wrong in principle: that there is some evidence to show that there are definite trends in KT and Ko with variation in V/Vb; and that the adoption of the Newton speed-dimension relation very considerably reduces the range of extrapolation. With regard to the last point the value of V/ Vi5 for the Taylor propellers was 4.3, whereas the upper limit of the value is possibly about 15; the advantage of such a restricted range of extrapolation should be obvious.

There are other considerations in favour of the adoption of constant values of VV-175 as the condition for experiments on propellers. Propulsion experiments involve expansion of thrusts as the cubes of the diameters, and this is permissible only if V varies as

vr).

Moreover, under this condition the cavitation number reduces to the simple relation (p-e)/D, whereas if V varies inversely as D, in accordance with the Reynolds speed-dimension relation, the cavitation number takes the form (p-e) x D2, and equality of number involves the pressure varying inversely as the area.

Incidentally in his contribution to the discussion on the Report which has been under consideration Professor Telfer went some distance along the road which has been indicated above, in so far as he referred to experiments carried out under the condition that nVT) is constant. This condition is merely an alternative form of the condition that V/VTD is constant. Both forms of the condition involve the proposition that "corresponding" speeds are in the ratio of the square roots of the dimensions, the proposition which affors the basis for experiments on model hulls and should also afford the basis for experiments on model propellers.

Professor M. Yamagata

1. Experiments with "Hakubasan Maru"

Since 1950, under the financial assistance of Ministry of Education, the Experiment Tank Committee of the Society of Naval Architects of Japan has carried out the extensive experiments with a single-screw cargo ship "Hakubasan Maru" and her models, to investigate the scale effects on the resistance and propulsion of ships. The first report, entitled "Trial Results of Hakubasan Maru" was published in 1951, and its abstract was given in "Abstract Notes and Data Concerning the Subjects at the Sixth International Conference of Ship Tank Superintendents, 1951", which was distributed at the Conference. A copy of the second report, entitled "Report of the Experiments on theHakubasan-Maru Models", which the Experiment Tank Committee of Japan has prepared for the Seventh International Conference on Ship Hydrodynamics, 1954, is to be distributed to each delegate at the coming Conference. I believe that it will serve as a

good reference to discuss the present subjects, and also subjects 2 and 4. 2. Experiments with "Ya_yoi Maru"

Under the financial assistance of Ministry of Transportation, the Shipbuilding Research Association of Japan has completed the full-scale experiments with a single-screw small training ship "Yayoi Maru" of the University of Mercantile Marine, and with her models, to investigate

the scale effects on the resistance, wake, propeller performance, and other self-propulsion factors,

the effect of bottom fouling on the resistance, wake, and propulsive performance of the ship, the effect of propeller fouling on the propulsive performance of the ship, and

the combined effect of bottom and propeller foulings on the propu_sive performance of the ship.

Her principal particulars are

Length B.P 18.288m

Breadth including skin 4.284m

Depth 2.414m

Draught from bottom of keel 1.934m

Displacement 78.7t

Main engine ...

200 B.H.P. x 380 R.P.M. diesel engine

Propeller 3-bladed solid type

Diameter I. 625m

Pitch (constant) 0.983m

"Yayoi Maru", which had been carefully repainted with commercial pa_nt at the end of June of 1952, was moored in Orido Bay of Shimizu. About ten series of measurements having been made, the whole test scheme with the full-sized ship was accomplished at the begiruiing of June of 1954. The measurements consisted of

the measurements of resistance and wake with "Yayoi Maru", towe 1 by a ;ingle-screw tug, and

the measurements of the thrust, torque and revolutions of a propeller of "Yayoi Maru'', moored to the quay, as well as self-propelled under the conditions of running freely and towing sea-anchors.

The model tests, corresponding to these measurements, have been carried out at Experiment Tank and Wind Tunnel of Transportation Technical Research Institute. in Tokyo.

The tests results obtained with both "Yayoi Maru" and her models are now under analysation, and the final conclusions will be drawn by the end of 1954. I believe that they may throw light on the scale effects on propellers and self-propulsion factors, and also on the problems of skin friction.

3. Scale effect on a propeller with air-drawing_phenomenon

For a propeller which is deeply immersed, and free from cavitation or air-drawing phenomenon, the scale effect on its characteristics is mainly due to the viscosity of water, and is believed to disappear practically at Reynolds numbers higher than a certain critical value.

The characteristics of a propeller, which works near the surface of water and air is sucked down, are considered as a function of not only advance constant and Reynolds number, but Froude and Weber numbers. However, since Reynolds and Weber numbers have little effect on the characteristics of a propeller with air-drawing phenomenon, its characteristics may be represented by the expression

V

VD

CT, CQ and Tip = fk n

g-).

According to Shiba's experimental results, the influence of Froude number n VD/g disappears practically when its value reaches about 3, which means that air cacity takes an ultimate form at this value. With most full-sized marine propellers, their Froude numbers for ordinary working conditions are within 1.0 to 1.4, so at the open-water tests with model propellers after air is sucked down Froude number should be chosen the same as for the working conditions of their full-sized propellers.

The critical advance constant, J,, where a marked fall in charactezistic curve takes place due to the occurrence of air-dravring phenomenon, are also considered as a function of the three

numbers quoted above. But, as Reynolds and Froude numbers have little effect on the critical advance constant, it may be deal with as a function of Weber number only, namely,

'Ter f 13),

where S is the surface tension of water. Shiba's experiments show that the critical value of Weber number at which its influence practically disappears is about E8x102. In general, Weber numbers for ordinary working conditions of most marine propellers are much higher than this critical value. Therefore, if we want to predict the accurate value of the critical advance constant of a full-sized propeller, it is absolutely necessary to choose Weber number higher than 1.8x102 at its model-propeller open-water test.

Dr. R. W. L. Gawn

The Committee's report covers a wide range and one of the proposals is that the Conference con-siders the possibility of adopting an international standard for self-propulsion tests. Agreement on essentials in this respect would be a valuable step forward.

Some of the differences in procedure are brought out in the report as a result of the co-operative tests on the Victory ship models. It so happens this was the first commercial ship model to be tested at Haslar with inner drive apparatus although such models have been tested in the more or less distant past with outer drive apparatus. The method and apparatus was exactly as in the tests of warship models for the Admiralty. Merchant ships are generally fuller than warships and the wake and augmented resistance are greater. Additionally the speed of advance and shaft speed are less than for warship models. It is therefore a matter of some interest to determine the extent to which the methods which have proved so trustworthy for warship tests will meet the requirements for merchant ship tests.

Briefly records were taken at each speed of advance over a range of shaft speed from well belovv ship self-propulsion point to well above model self-propulsion point. The model propeller was also tested in open water over an equally wide range of speed and shaft revolutions. The dynamo-meters were tested on the turbine brake as usual to determine the small correction to be applied to the recorded torque and thrust on account of friction of shafts and gearing. The speeds of advance of the model corresponded to 12, 14, 16 and 18 knots respectively. Results are shown on Figure 1 for 16 knots only to indicate procedure. Figure 2 shows the derived hull efficiency elements for the same speed and Figure 3 the faired variation with speed.

Developed horsepower was deduced from the recorded torque and shaft speed at ship propulsion point and full particulars of this and other factors are in the Committee's report, including effective horsepower derived from measurement of resistance of the model hull. Relevant results at 16 knots are in the appended table under the heading Method 1.

Predictions for warships are made not from the developed horsepower deduced as above, but from the hull efficiency elements appropriate to model self-propulsion point and propeller efficiency determined from methodical series propeller results. The quasi propulsive coefficient is determined from the product of propeller efficiency, hull efficiency and relative rotative efficiency divided by the appendage coefficient (ratio of resistance of naked hull including appendages to that of naked hull alone). This is multiplied by a factor derived from the results of speed trials of similar ships to determine the propulsive coefficient and thence the shaft horse-power from the effective horsehorse-power of the naked hull. In effect the factor includes a margin for wind resistance, shaft friction and any error in scale corrections. The value for warships generally is 0.9 to unity. No information is available at Haslar as to the appropriate value of the factor for the Victory ship but 0,95 was assumed as an arbitrary taken figure, largely as an indication of the method rather than as a serviceable prediction of performance. Appendage co-efficient was assumed as 1.03. Results are in the appended table under heading Method 2. This method is found to give more reliable and consistent results for warship predictions, one consideration being that scale effect is reduced if not eliminated and in any case the basis of reference for propeller efficiency is consistent and independent of the size of model under test. The taken shaft horsepower at 16 knots deduced by the Haslar method, namely 6250, agrees fairly well with the results for s. s. Tervaete given in Reference 1 but is considerably in excess of the figure of 4,800 for Blue Field Victory interpolated from the results in the Committee's report. The developed horsepower by Method 1 is also in excess of the trial results for the latter *ship. The hulls of both ships are flush welded and although the results for the former were obtained during voyages these were shown in the paper to be comparable with the measured mile trial results. Correlation with model results is complicated by the marked ship to ship difference for which weather and the condition of hull surface including fouling may be in part responsible. In

order to explore this it would be helpful if the Committee would add the shaft speed and the shaft thrust to the trial data given in their report.

The essential feature of the test procedure described is the wide range of propeller loading covered at each speed of advance. It is hoped that the advantages will be clear from the description given. Subsequent analysis can be made for a different ship loading and this is particularly

im-portant for multi-screw ships. The appendage resistance for such ships s greater than for the special case of the single screw ship considered and the appropriate scale correction is on a different basis or at least of a different order than for the hull proper. It may be mentioned too that it is frequently the practice to test warship models at two conditions of hull loading so that a wide range of information is available to cover the operational requirements of the ship. The practice of deducing propeller efficiency from large scale methodical series propeller data is also commended to the Conference. The data for this particular estimate wz.s that given in reference Z. It was shown in the 1952 paper the scale effect is very small if not negligible. However in the particular case of the Victory ship the difference is not very important as may be apparent from the propeller efficiencies quoted in the appended table, namely 0.67 from the tests of the model of the "as fitted" propeller and 0.66 from the methodical series.

The analysis has brought out the rather wide difference in results if huil efficiency elements are interpreted at ship self-propulsion point in lieu of model self-propulsion point. This is especially the case for the thrust deduction factor which at 16 knots is 0.21 for slip self-propulsion and 0.16 for model self-propulsion. The difference is generally not so marked for warships and the model self-propulsion values are adopted at Haslar as these are experimental facts. The ship values are subject to uncertainty not only due to direct scale effect but also indirectly on account of any error that may be involved in the scale correction for hull resistance. It is sug;ested that the Conference would do well to seek agreement as to the presentation in this respect.

On the general question of scale effect the report mentions the relevance of experiments on geometrically similar model propellers. The importance of scale was brought out in reference 2 and a value suggested on good evidence for the critical Reynolds' number. A fairly wide range of tests on accurate models of three parent forms, has also been carried out both in ship tanks and in tunnels under the guidance of the Cavitation Committee. It is hoped that the Scale Effect Committee will not overlook these investigations in planning any furthe, programme they may consider advisable.

The Committe's report mentions that the agreement between the tanks participating in the self-propulsion tests is not so good as might be hoped for, especially as regards quasi propulsive coefficient. Seeking to learn from the degree of agreement rather than the reverse, it is pertinent to note that the alignment of the results between 12 of the 15 tanks is fairly close at high speed, both as regards quasi propulsive coefficient and developed horsepower. This may have a bearing on scale effect as the Reynolds' number is greater.

References

1 Sea Trials on a Victory Ship AP. 3 in normal merchant ship service Professor G. Aertssen.

I.N.A. 1953. Fig. 15.

2 Effect of Pitch and Blade Width on Propeller Performance. Dr. R. N L. Gown. I.N.A. 1952.

Victory Ship Model, 16 knots, Self-propulsion tests

Item Method 1 Method Z

Wake fraction - Taylor 0.298 0.305

Thrust deduction fraction 0.209 0.176

Hull efficiency 1.13 I. 18

Relative rotative efficiency 1.02 1.01

Propeller efficiency - open 0.674) _{0.66 (methodical series)} Propeller efficiency - behind 0.687)

Quasi propulsive coefficient 0.77 0.77

Effective horsepower 4340 4540

Developed horsepower 5600 6250 (shaft horsepower)

Revolutions per minute 74.4 75.0

Propeller thrust, tons 50.2 50.7

Note: 1. Propeller items in Method 1 are derived from model results al ship self-propulsion point. Effective horsepower is for model resistance corrected by Froude's skin friction co-efficient and to 59 degrees Fahrenheit temperature (as agreed by the Conference). Hull efficiency elements in Method 2 are for model self-propulsi,n point. Propeller

efficiency is from methodical series results. Quasi propulsive c )efficient and shaft horse-power are derived as in Haslar method described in text. Effective horsehorse-poweris from

model results with Froude skin friction corrected to 55 degrees Fahrenheit temperature and with small correction for standard model as usual.

Relevant model results are in Figures 1, 2 and 3. Froude wake and augmentation of resistance per cent have been converted to Taylor wake and thrust deduction respectively in above table.

qnclo sures:

Figure 1. Inner drive propulsion 16 knots. Figure 2. Hull efficiency elements. 16 knots.

INNER DRIVE PROPULSION. SPEED 16 KNOTS.

DISPLACEMENT 14848 TONS LEVEL TRIM.

320 400 SCALE' OF R P M. FIGURE I.

A

ip.,,

Ill

2 A

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r

A

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ri,

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HULL EFFICIENCY ELEMENTS.

SPEED 16 KNOTS.

DISPLACEMENT 14848 TONS LEVEL TRIM.

43 40 25 06 1,4 FIGIJRZ 2. 380 400 SC.44.."ft: 0F M. WAKS 0 Ot CES'T

eAuGmENT PER CRIIr

PROPwLS SI.-HI. SELF ON

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VARIATION OF HULL EFFICIENCY ELEMENTS WITH SPEED. DISPLACEMENT 14848 TONS LEVEL TRIM.

MODEL SELF - PROPULSION POINT.

moDEL. SELF PROPULSION

SNIP SELF PROPULSION

FIGURE 3.

I 0

la 13

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t 5 16

SPEED IN KNOTS

Dr. E. Castagneto

As it is perhaps remembered by the Superintendents of ship-tanks, comparative tests like the ones on the "Victory" ship model, now under examination, were carried out in 1939 by

suggestion of late Gen. Giuseppe Rota. That research concerned a twin-screw ship, 112 m. in length, and 4900 T. of displacement. The results were forwarded to :he various establishments in due course, but they were never discussed, as the Conference in prcgramrne did not take place on account of the war.

It may be now useful to know that the agreement among the results of tank establishments was then less good than at present: the differences were mainly It 3,0% in EHP and ± 4,5 in DHP. The results obtained through comparative tests with the model of "Vi,tory" ships show a progress, and I think that with a finer and faster ship the agreement would have been still better.

The experimental study of the scale effect on self-propulsion factors requires the utmost accuracy in tests. In this connection, it seems to me necessary to call attention to two points: a) Measurements of the thrust, b) Experimental arrangement for tests in open.

a) In open thrust is generally referred to the propeller hub, and it does not include the resistance of the screw supporting shaft and of the hub itself. In self-propulsion tests with models, and on ships, thrust is measured on thrust block. If the saaft is not level, but falling sternwards as is generally the case, the thrust on the thrust block is less than that on the propeller hub, by an amount equal to the component, in direction of che axis, of the weight of the line shafting and of the propeller. The difference may even reach 10% and more at lower speed. In the same way the direction according to which the thrust is measured on model must be considered.

The tank of Rome, in its standard routine, does not introduce any corrections and I don't Icnow which practice is followed by other establishments.

b) In open tests the propeller shaft is either freely revolving in water, or enclosed in a bossing, as may be seen from fig. I a) b) c); in the second case the diameter of the body after the propeller model is usually larger, and may be equal to that of the '3ropeller hub.

Careful experiments made at Rome tank (see for instance fig. 2) have made it clear that, with increasing diameter, there is an increase of thrust, torque and efficiency. Besides, with equal diameter, the thrust with a shaft revolving in water, is si .ghtly :ess than that with an enclosed shaft.

An agreement on the ways to be followed as regards these two points would be desirable.

FIG.1

3