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VWS Mitt. 58 (2002): Rational Evaluations of Ship Speed Trials

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Rational Evaluations of Traditionaland Quasisteady Ship Speed Trials

Michael Schmiechen

Published on the occasion of the 23rd ITTC Venice 2002 andof the Centenary of VWS, the Berlin Model Basin, in 2003

VWS Mitteilungen Heft 58, post mortem

Berlin 2002

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in memoriam

Versuchsanstalt fr Wasserbau und Schiffbau, Berlin

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VWS Mitt. 58 (2002): Rational Evaluations of Ship Speed Trials 2

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Versuchsanstalt fr Wasserbau und Schiffbau,VWS: the Berlin Model Basin,

Mller-Breslau-Strasse (Schleuseninsel)

10623 Berlin, Germany,started operation in 1903 and

ceased to exist at the end of 2001

Bibliographical reference:

Michael Schmiechen:Rational Evaluations of Traditionaland Quasisteady Ship Speed Trials.

Berlin: VWS Mitteilungen Heft 58 (2002)

Author, editor and publisher:

Michael Schmiechen, Bartningallee 16,10557 Berlin (Tiergarten), Germany

Phone: +49 / 30 / 3 92 71 64e-mail: [email protected]

website: http://www.t-online.de/home/m.schm

Full version: 10 Euro / U.S. $ , short version: free

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Rational Evaluations of Traditional

and Quasisteady Ship Speed Trialswithout reference to model test results

and other prior information, as it should be

Michael Schmiechen

Abstract

The present volume contains selected documents concerning the most recent developmentsand results, essentially over the last five years, of the rational theory of ship hull-propellerinteraction, which the author has

suggested more than twenty years ago,

developed in a number of fundamental projects and worked examples and

promoted in many papers and lectures, all to be found on his website.

The recent developments and results, having been triggered by the Japanese proposal of anISO standard for the evaluation of traditional ship speed trials, concern

the rational evaluation of traditional ship speed trials at 'steady' conditions and the

reduction to the condition of no wind and no waves, both without any reference to modeltest results and other prior information, as it should be, and

the rational evaluation of quasisteady ship speed trials, including thrust measurements,resulting in a complete powering performance analysis over a wide range of propellerloads, again without any reference to model test results and other prior information, as itshould be.

The test cases,

the example data of ISO 15016: 2002-06 and

the example data of a single quasisteady 'model' run,

published in VWS Report No. 1100/87, respectively, are suggested to be used in benchmarktests of further developed and/or alternative procedures following the Guidelines forBenchmarking, ITTC Recommended Procedure 4.0-01, discussed in the Final Report of theQuality Systems Group to the 23rd ITTC (Proc. Vol. I, 288-292). While the example data ofthe ISO standard are readily available the VWS Report No. 1100/87 quoted is included in thisvolume, the data file being available on request.

Only at this stage, after

adequate powering models, local wake and thrust deduction axioms based on propellerloading measured in terms of the ideal efficiency in particular, and

reliable methods for the identification of their parameters model and full scale have been

established,

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the problems of scale effects and scaling (extrapolation) may be reconsidered following theprinciples set forth and using the power tools developed. The volume contains details of thedevelopments together with a re-evaluation of the METEOR data and thus, for the first timeever, scale effects in wake and thrust deduction determined directly and reliably.

In view of the difficult problems to be solved, of the rapid developments in computationalfluid dynamics to be matched and, last but not least, of the demands of clients to be satisfied,experts will finally have to realise that the community can no longer afford to ignoredevelopments and results based on advanced methods of knowledge and systems engineering,which are long established and common practice in other fields. After the ground work hasbeen done the problem is no longer to try and 'disprove' the methods proposed, but tounderstand the simple principles and boldly apply the new power tools.

Contents

Subject File content file_name short

Preliminaries Title, abstract, relations to ITTC workand basic work, rational evaluations,

work still to be done

vws_m58.pdf

vws_m58.htm

x

Evaluation oftraditional trials

Cover letter concerning ISO/CD15016

trl_cov.pdf x

Written Discussion of the Report ofthe SC on Trials and Monitoring to the

22nd ITTC

ittc_dsc.pdf

Final evaluation of the ISO 15016example after correction of a misprint

iso_10.pdf

St. Petersburg paper 2001 lav_pap.pdf

Presentation of the results lav_prs.pdf x

Evaluation ofquasisteady trials

Evaluation of 'model' data taken fromVWS Report No. 1100/87

mod_eval.pdf

Presentation of the results mod_pres.pdf x

Investigation of wake axioms as wellas re-evaluation of the METEOR data hpi_wka.pdf

Letter to ITTC Committees concernedasking for co-operation

ittc_com.pdf x

VWS Report No. 1100/87 with basicdata of run 8 with VWS Model 2491

and Propeller 1340 R

rep_1100.doc

Partial solutionconcerning modelwake from steady

overload tests

Proceedings of the 4th ITTC Berlin1937, report by Horn and contribution

by Troost

Mitteilungender VWS,Heft 32.

Berlin 1937.

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Thefile_names in the table of contents identify the .pdf files on the author's website. In thesefiles plots of data are distinguished by colour, while in this volume only black and whitecopies are reproduced. A short version of this volume contains only the documents checked.

The individual files may be accessed directly under website/file_name, but more conveniently

via the .htm version of this introductory file (vws_m58.htm) containing live links not only tothe documents listed, but to all the background material quoted.

Further work on propulsion by the author, all in .pdf format, can be accessed via annotatedlinks in the following hypertext files on the website:

Bibliography on propulsion (bibl_prp.htm),

Recent papers on propulsion (pap_prp.htm)

What's new? (news.htm).

In case of the evaluations, all in Mathcad 8 Professional, readers interested in doing their ownnumerical exercises and joining further developments of the procedures described are invitedto request the original .mcd files together with the respective data files, if any.

Relations to work of ITTC Committees

The present collection of documents is a contribution to the Report of the SpecialistCommittee on Speed and Powering Trials to the 23rd ITTC at Venice (Proc. Vol. II, 341-367).The SC Report covers only, though in great detail, the traditional procedures for theevaluation oftraditional trials. 'The use of [model scale] propeller open water characteristicsis the basis for four of the correction methods studied by the SC'. In view of earlier geosimtests, the METEOR tests and most recently in view of the section on [model] screw propeller

scale effects in the Final Report and Recommendations of the Propulsion Committee to the23rd ITTC (Proc. Vol. I, 113-115) this basis is more than suspect.

The present collection of documents concerns the most recent developments and results,essentially over the past five years, of the rational theory of ship hull-propeller interaction.The work reported is part of a long term project addressing all fundamental problems of thepowering performance analysis and prediction of full scale ships under service conditions,avoiding most of the problems encountered in the traditional approaches. It addressesproblems and solutions not mentioned in the SC Report although all intermediate and finalresults have been brought to the attention of all ITTC Committees concerned.

Though they have 'nothing' to do with the traditional trials only the Proceedings of the 2nd

International Workshop on the Rational Theory of Ship Hull-Propeller Interaction and itsApplications held at VWS, the Berlin Model Basin, in 1991 are being listed in the SC Report.That workshop had been devoted to the quasisteady 'trials' with the German research vesselMETEOR under service conditions in the Arctic Sea and the complete powering performanceevaluation. But this problem has not yet been addressed by the Specialist Committee on Speedand Powering Trials and its predecessors.

The work on the complete powering performance analysis is documented in the second part of

this accountof recent developments and results of the rational theory of ship hull-propellerinteraction. Triggered by a seminar held at the Gdansk Ship Model Basin in January 2002 a'model' test of 1987 has been successfully evaluated and the METEOR data have been re-evaluated, the results demonstrating that the development has now reached a certain stage ofmaturity.

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In the first part of this accountof recent developments and results of the rational theory ofship hull-propeller interactionthe rational evaluation of traditional speed and powering trialsbased on the full scale propeller behind characteristics is documented. The work, a by-productof the METEOR project, has been triggered by the Japanese working draft ISO/WD 15016 of

1998, which is now a standard proper: ISO 15016: 2002-06.Already in the discussion of the Report of the SC on Trials and Monitoring presented to the22nd ITTC 1999 it has been shown that the traditional procedure proposed in the ISO standardprovides inconsistent results. Further it has been shown that the inherent problems leading tothe unacceptable results can easily be removed, if adequately addressed. The progress of thiswork, mostly in terms of worked examples, has been published routinely as soon as finishedon the author's website. The development has reached a state of maturity documented in apaper presented at St. Petersburg in June 2001.

Relations to basic work published earlier

In the METEOR project it has been shown that the complete powering performance of fullscale ships can be determined from quasisteady speed trial provided not only torque butreliable thrust measurements have been performed. The results of the METEOR project havebeen subject of the 2nd International Workshop on the Rational Theory of Ship Hull-PropellerInteraction and its Applications at VWS, the Berlin Model Basin, in June 1991.

The essential parts of the Proceedings published in the Mitteilungen der VWS are to be foundon the author's website under the Recent papers on propulsion (pap_prp.htm), in particular theMETEOR report (int_rep.pdf) and the BASIC programs (int_bas.pdf) as well as the oraldiscussions (int_orl.pdf) and the written discussions (int_wrt.pdf).

The model underlying the evaluation of the METEOR data 'suffered' from a 'global' wakeaxiom, the lost power axiom (hpi_lpa.pdf), resulting in an involved and sensitive method forthe determination of the wake fraction, which has been shown to be plausible, but has alwaysbeen found to be unreliable in applications and thus felt to be inadequate.

After much deliberation, lasting over fifteen years, much simpler and more adequate localwake axioms (hpi_wka.pdf) have recently been 'dreamt up' during a vacation on Cyprus andshown to result in a very robust identification of the wake fraction. The method avoids the'dangerous' extrapolations to the states of vanishing advance ratio, or rather vanishing idealefficiency, and vanishing thrust, it is based on local values only, as it should be. TheMETEOR data have been re-evaluated accordingly.

These robust wake axioms permit to return to a thrust deduction axiom proposed in the 1987paper on 'Wake and Thrust Deduction from Quasisteady Ship Model Propulsion Tests Alone'.nstead of correlating with the 'artificial' hull advance ratio it is now possible to correlate withthe 'natural' ideal or jet efficiency as measure of propeller loading, assuming constantdisplacement influence ratio in the limited range of data and of interest.

The values of the energy wake fraction determined at the model and at the METEOR suggestthat the frictional torque in the shaft, in the stern bearing in particular, may in future need tobe identified separately.

Under the Recent papers on propulsion (pap_prp.htm) a whole section is devoted to thedevelopment of thrust deduction and wake axioms. Two papers deal with the thrust deduction

axiom. The first is a rather theoretical comparison (hpi_thd.pdf) of the proposal of the authorwith Kracht's proposal, the second, part of the author's winter semester 97/98 lectures held at

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the Technical University Berlin shows the plausibility (hpi_tha.pdf) of the proposal of theauthor.

While the robust procedures presented concern full scale ship speed trials in particular

Horn's earlier partial solution limited to the determination of the model wake, and Kracht's recent partial solution limited to the determination of the model thrust deduction

based on steady overload tests at given speeds are essentially limited to model scale. Furtherthese methods include 'extreme' flow conditions, typically down to zero thrust, which may beas inadequate for a rational analysis of the powering performance as are flow conditions atmodel hull towing and model propeller open water tests.

To the limited knowledge of the author Horn was the first and the only one to try and getalong without model propeller open water tests. He introduced the concept of equivalentpropellers, but wanted to 'construct' them in detail. This unnecessary complication and all thetechnical limitations at his time finally forced him to resort to model propeller open water

tests again. Horn's (1937) report to the 4th ITTC, held at the Versuchsanstalt fr Wasserbauund Schiffbau in 1937, is included in this volume for ready reference. Publications on Kracht'swork are readily available (1999), a more recent one being quoted in the SC Report.

The recent developments of robust procedures for the evaluation, not only of traditional speedtrials but of quasisteady speed trials, have been triggered by the Japanese proposal of an ISOstandard for the evaluation of traditional ship speed trials. A letter to the convener of April 15,1998 (trl_cov.pdf) together with an alternative draft ISO '98 proposal (trl_prp.pdf) marks thestart of the development. A letter to the ITTC Committees concerned (ittc_com.pdf),suggesting co-operative testing of the procedures, as was done with Horn's procedure in thethirties, marks the end of this development.

Rational evaluation of traditional ship speed trials

Under the Recent papers on propulsion (pap_prp.htm) a large number of worked examplesand discussions are to be found corresponding to the state of the development at the time ofthe respective exercises. Thus most of the examples are now of 'historical' interest only.Further papers concern the full scale tests with an air cushion vehicle, the SES CORSAIR,with partially submerged propellers, where traditional methods fail altogether.

Closely related to these successively improved evaluations are the written discussion(ittc_dsc.pdf) and its presentation (ittc_prs.pdf) on the Report of the Specialist Committee onTrials and Monitoring to the 22nd ITTC, held at Seoul and Shanghai in 1999. Particularly for

the German colleagues the explanations (trl_erl.pdf) of the rational procedure have beenprepared.

The updated draft ISO '00 proposal (trl_pro2.pdf) of the earlier ISO '98 Proposal, an alterna-tive for the working draft ISO/WD 15016, became necessary due to the successful inclusionof the identification of the required power and the subsequently possible reduction to the nowind and no wave condition (iso_fin8.pdf). As is the first proposal, this draft is just a sketchyoutline, to be updated and upgraded in due course, maybe on the basis of the six newprocedures on Speed/Power Trials recommended for adoption by the ITTC in the SC Reportto the 23rd ITTC (Proc. Vol. II, 365).

In the meantime the EVEREST data produced by Tamura (1999) had been used in Japan as atest case and the rational procedure proposed had been 'proved' to be inadequate. Conse-quently the EVEREST data have been analysed in detail (everest.pdf) and, after the detection

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of systematic inconsistencies in the artificial data, the EVEREST data have been furtherscrutinized (everest8.pdf) and finally been discarded as inadequate for the purposes at hand.

At this stage the ISO/DIS 15016 example has been revisited, which does not suffer from thedefects of artificial data. In the 'final' evaluation of the ISO/DIS 15016 example (iso_10.pdf) a

'random' inconsistency in the data has been removed as well as inconsistencies in theseakeeping model and the corresponding program.

As can be seen from the comparison of evaluations (iso_fin8.pdf) the mistake in the dataupsets the method of Kracht et al. (Nicolaysen, 1998), which happens to 'settle' on the 'wrong'behind condition nstead of eliminating it. In the meantime the misprint suspected in theISO/DIS example had been confirmed, details to be found in the correspondence fullydocumented in the recent papers on propulsion (pap_prp.htm).

The latest developments (lav_pap.pdf) concerning the evaluation of traditional ship speedtrials have been summarized in the paper presented (lav_prs.pdf) and discussed during theLavrentiev Lectures Saint-Petersburg 2001, at the International Symposium on Ship Propul-sion, held on June 19-21, 2001 at the Saint-Petersburg State Marine Technical University. Onthe author's website there is also to be found a hypertext version of the St. Petersburg paperwith live links (lav_pap.htm) to all the basic material.

Lectures (on_trls.pdf) on the rational evaluation of ship speed trials have been held in fall andwinter 1999/2000 at the Universities Berlin, Duisburg, Hamburg and Rostock. And a furtheradvanced presentation (trl_tuhh.pdf) has been prepared in German and presented at theArbeitsbereiche Schiffbau Hamburg-Harburg and, via video link, at the Institut fr Schiffs-technik Duisburg in January 2002.

Rational evaluation of quasisteady ship speed trials

In a seminar at the Gdansk Ship Model Basin in January 2002 not only the evaluation of shipspeed trials but of ship model tests has been treated in detail. While the rational evaluation oftraditional trials has 'nothing to do' with ship theory, but is a matter of elementary mechanicsand of craftsmanship, the rational evaluation of the ship powering erformance on model andfull scale requires some ship theory as well as additional thrust measurements at quasisteadyconditions.

To demonstrate the potential of the methodology the re-evaluation of a quasisteady 'model'test (mod_eval.pdf) has been undertaken, which had been published earlier (1987). As hasbeen mentioned before the original program and data files are available on request. A copy ofthe paper, which is identical with VWS Report No. 1100/87, is included in this volume. Thecopy includes the data of run 8 with VWS hull model 2491 and VWS propeller model 1340R, but does not include the obsolete results of the former evaluation. Essential parts of thisreport (rep_1100.doc) have also been scanned and can be accessed on the author's website.

The goal was to study the impact of the insights gained over the past fifteen years and toprovide an adequate basis for the development of a rational scaling procedure, which has beenfelt missing in the discussions in Gdansk. During this work the document on wake axioms(hpi_wka.pdf) has been updated, including the re-evaluation of the METEOR results.

In a letter to ITTC Committees concerned (ittc_com.pdf), the Powering, the Trials and theProcedures Committees as well as the Quality Systems Group, the results obtained so far have

been brought to the attention of the groups considered to be most interested in the recentdevelopments and in joining future developments of a corresponding scaling procedure.

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Subsequently a sign error (sign_err.pdf) had been detected in the re-evaluation, after thecorrection of which the 'rational' results became even closer to the traditional results thanbefore. Consequently the scaling can be done as before, although the author feels that it needsto be reconsidered ab ovo as has been done with the conduct and evaluation of full scale sea

trials and of model tests.In order to spread the gospel a presentation of the results (mod_pres.pdf), dedicated to theCentenary of VWS, Berlin, 2003, has been prepared and updated after presentation anddiscussion at the Gdansk Ship Model Basin in July 2002. In particular it has been noted, thatISO/DIS 15016 has in the meantime been published as a standard proper: ISO 15016: 2002-06despite repeated qualified demonstrations of inherent inconsistencies. And not only 'Germanyhas agreed'.

Work still to be done: on scaling

The axiomatic frame work and the procedures based on it provide a coherent representationspace of single sets of coherent data and thus a very sharp tool. If this power tool is beingapplied to quasisteady model runs at various speeds it permits to distinguish betweenReynolds effects of laminarity in propeller operation and between Reynolds and Froudeeffects in hull resistance and wake.

The data of the other runs of the 'model' test are no more available and the author cannotperform new tests. But somebody else will perform these simple tests and study the results indetail, maybe with the assistance of the author. In any case such basic tests will be necessaryfor the development of a rational scaling procedure. The need for this development alreadyfelt by Horn is strongly supported by the section on [model] screw propeller scale effects inthe Final Report and Recommendations of the Propulsion Committee to the 23rd ITTC (Proc.

Vol. I, 113-115).

The development includes the solution of the question, what frictional deduction shall beapplied in model tests. The feeling of the author is: in principle none, as it 'only' changes thepropeller loading and thus the hull advance ratio, the operational conditions of the hull-propeller system, which contrary to the traditional trials are determined in a wide range ofadvance ratios. The problem is in any case to estimate the resistance of the full scale ship. Ofparticular interest in this connection are the sections concerning the future friction line and theform factors in the Final Report and Recommendations of the Propulsion Committee to the23rd ITTC (Proc. Vol. I, 106-112).

It is to expected that this work will again require painful departures from long cherished

professional beliefs and traditions.

References

Achkinadze (2001), A. S. (Editor): Proceedings of the International Symposium on ShipPropulsion. The Saint-Petersburg State Marine Technical University, June 19/21, 2001.Dedicated to V. M. Lavrentiev.

Horn (1937), F.: Bestimmung des Mitstroms durch Versuch Modell mit Schraube. Vorbemer-kungen, Bericht. Anhang I: Genderte Auswertung von Schraubenversuchen. Anhang II:Auswertung von effektiven Nachstrom-Mittelwerten nach der Methode von Horn-

Dickmann: (Troost). In: Weitbrecht (1937) 54-63.

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Kracht (1999), A. M. and H.-J. Stitterich: Power Predictions of Single-Screw Ships Based onComparable Trial and Model Test Results. Trans. SNAME 107 (1999) 193-212.

Nicolaysen (1998), K.-H.: Rationalisierung der Auswertung von Probefahrten. VWS BerichtNr. 1282/98. FDS Bericht.

Schmiechen (1987), M.: Wake and Thrust Deduction from Quasisteady Ship Model Propul-sion Tests Alone. VWS Report No. 1100/1987. Published on the occasion of a visit toKorean and Japanese ship research institutes and the 18th ITTC at Kobe 1987 and incommemoration of the 4th ITTC at Berlin in 1937.

Schmiechen (1991), M.: 2nd INTERACTION Berlin '91, the 2nd International Workshop onthe Rational Theory of Ship Hull-Propeller Interaction and its Applications. VWS, theBerlin Model Basin, June 13 - 14, 1991. Proceedings. Mitteilungen der Versuchsanstalt frWasserbau und Schiffbau, Heft 56, 1991.

Schmiechen (2001), M.: Evaluating Ship Speed Trials: Identifying Parameters of Powering

Models. In: Achkinadze (2001) 143-152.

Tamura (1999), K.: An Appraisal of Correction Methods of Wind and Tidal Current Effectson Speed Trial Results of a Ship. Transactions West-Japan SNA (1999) No.97, 11-24

Weitbrecht (1937), H. M. (Editor): Proceedings of the 4th ITTC Berlin 1937. Mitteilungen derVersuchsanstalt fr Wasserbau und Schiffbau, Heft 32, 1937.

The Specialist Committee on Speed and Powering Trials: Final Report and Recommendationsto the 23rd ITTC Venice 2002. Proc. Vol. II, 341-367.

The Propulsion Committee: Final Report and Recommendations to the 23rd ITTC Venice2002. Proc. Vol. I, 89-151.

The Quality Systems Group: Final Report and Recommendations to the 23rd ITTC Venice2002. Proc. Vol. I, 285-297.

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