on evident principles of quasi-steady ship powering trials ... · 3.1 procedure aimed at 8 3.2...

Michael Schmiechen

On evident principles of quasi-steady ship powering trials and monitoring

Additional contributions to the discussion of talks by Mr. Froitzheim und Dr. Schulze delivered at the 13. SVA-Forschungsforum 'Theoria cum praxi' on January 30, 2020

PREFACE In addition to a very short oral remark and further written remarks in

German (See_the_future.pdf) this paper is a detailed contribution to the dis-cussion of talks by S. Froitzheim und Dr. Reinhard Schulze, delivered at the 13. SVA-Forschungsforum 'Theoria cum praxi' on January 30, 2020.

The following text is my substantially amended mail sent to Dr. KarstenHochkirch DNVGL the day after the meeting at the SVA Potsdam. To pro-vide for ease of accessing and grasping the essentials, headings and detailed arguments, respectively, have been added.

The latter are based on my long personal experience concerning many as-pects of trials and on ongoing related in-depth disputes with Dr. Klaus Wag-ner. During translation the original German draft has been reduced to the bare essentials, thus providing a concise tutorial concerning quasi-steady trials, precepts of what to do and what not to do.

Abstract This short paper is itself an abstract. It is a concise, of course personal ac-

count of the basic ideas and the conceptual, experimental and numerical tools, underlying my continued work over the past forty years dedicated to developing a rational theory and practice of trustworthy ship powering trials on full scale.

Efficient, reliable trials are necessary and urgently required to validate in-dividual predictions in delivery trials and to validate methods of powering prediction in general. Different from all traditional procedures the rational procedure developed avoids any confusion with issues of prediction, as mandatory for scientific purposes and trustworthy results.

The few parameters of the few simple conventions adopted are reliably identified using established methods of systems identification. Various heu-ristical approximations, used to cope with the non-linearity of the conven-tions, have finally been abandoned.

http://m-schmiechen.homepage.t-online.de/HomepageClassic01/See_the_future.pdf

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Contents 1 Introduction 3

1.1 Problems ahead 3 1.2 Early attempts 3 1.3 Limited goal 4 1.4 Top-down approach 4

2 Theory of theories 5 2.1 Evident principles 5 2.2 Pragmatic meta-principle 5 2.3 Model based conventions 6 2.4 Mathematical routines 6 2.5 Conceptions understood 7

3 Quasi-steady tests 8 3.1 Procedure aimed at 8 3.2 Tests conducted 8 3.3 Data analysed 9 3.4 Quintessence 9

4 Steady states analysed 11 4.1 Started as intermezzo 11 4.2 Power conventions 11 4.3 Power supplied 12 4.4 Powers required 13 4.5 Traditional trials 13

5 Conclusions 14 5.1 Implications 14 5.2 Further problems 14

6 References 15 6.1 Talks delivered 15 6.2 My related papers 15 6.3 My bibliographies 15

7 Author 15 7.1 Contacts 15 7.2 Website 15

8 Notes 16

Principles of ship powering trials and monitoring

Copyright Michael Schmiechen 2020

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" ... always remember that it is impossible to speak in such a way that you cannot be misunderstood: ... If greater precision is needed, it is needed because the problem to be solved demands it."

Sir Karl Popper: Unended Quest. 1974. 5

1 Introduction 1.1 Problems ahead

From: Michael Schmiechen Sent: Friday, January 31, 2020 9:15 PM 10 To: Karsten Hochkirch Cc: Klaus Wagner Subject: See (!) the future!

Dear Dr. Karsten Hochkirch, 15 followig the proposals of Dr. Reinhard Schulze you may no longer require

my trustworthy analyses of trials. But why did not you have any questions yesterday?

Following the very general talk of Dr. Thomas Rüggeberg concerning the drastical changes of problems to be solved and the resulting compulsion to 20 cooperate, the subsequent, detailed presentation of the research and develop-ment projects of SVA by Dr. Christian Masilge has been felt not to respond to the perspective of the future outlined. 1.2 Early attempts

Of course I appreciate, that finally the aims are followed, which I have de-25 fined and consistently followed since 1980. But as I mentioned, the talks con-cerning trials indicated, that the work reported is totally different from my work, that the problem to be solved has still not been understood.

So far my repeated invitations jointly to solve the problems faced, found no response except for ritual repetitions of misjudgements. Once and again un-30 qualified and inexperienced beginners have been charged to study the prob-lem of trials, with youthful courage coming up with outlooks on future devel-opments. Formerly the fundamental problems addressed have been of concern to the 'superintendents' themselves at leading model basins. No further com-ments! 35

The basic work of Fritz Horn in the 1930s, discussed at the 4th ITTC at Berlin in 1937, to overcome the evident deficiencies of Froude's historical approach, suffered from the lack of adequate conceptual, instrumental and computational tools, and was disrupted by the war.

Post-war attempts at Wageningen and Berlin to cope with the propeller per-40 formance in non-uniform wakes behind hulls, to get rid of the disturbing rota-

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tive efficiency, still suffered from the lack of adequate tools. But although these limitations no longer exist, the tools now available are still used in the spirit of our great-grandfathers! 1.3 Limited goal

If only the performance at steady states is of interest, inertial effects have to 5 be avoided as far as possible. Due to the resulting rates of change of the ki-netic energy even very small, unavoidable accelerations on full and model scale have to be monitored; details to be discussed further down.

So I am still wondering, what may be the purpose of unsteady hull towing and propeller open water tests, to increase the inertial effects and study them 10 at considerable waste of resources?

Such non-sensical exercises, which have even been subject of a STG paper, remind me of the re-calculation and re-publication of the table of logarithms at the Harvard University, when the first digital computers became available. 1.4 Top-down approach 15

In view of my theories, methods and results the 'incredible' state of affairs and the resulting incoherent discussions, hopelessly confusing all issues, are no longer acceptable. Hence I once again repeat the very simple basic ideas and principles, underlying trustworthy ship powering trials and monitoring.

The top-down approach adopted permits to highlight and understand the es-20 sentials, without distraction by the often rather involved logical, mathematical and technical problems, grossly underestimated by traditionally trained naval architects.

In particular I encourage young, interested colleagues, still curious and in-quisitive, and urge them to study the state of development and to dare and 25 think themselves, sapere aude.

But the top down approach is evidently not possible in terms of the simple minded traditional jargon of naval architects, which is conceptually not rich enough, neither for discussing the essential aspects nor for the purposes of efficient research and development. 30

In the revised edition of the 'ITTC Symbols and Terminology List, Version 1993' (sat_93.pdf) I have explicitly addressed this problem. And in the first file of the analysis of my 'model' trial of 1986 I have provided rule driven symbols necessary for handling the sufficiently rich formal system of

35 concepts and conventions proposed.To follow my arguments requires only some curiosity and concentration.

In the current PISA Report and in a recent edition of the ‘MIT Technology Review’ I read, that only few people still listen and read. And that of those few 20 % do not understand, what they hear or read, respectively. In any ca-

40 se the 'absence' of concentration has been identified as reason of this most disturbing fact, not limited to fifteen years old pupils.

http://www.m-schmiechen.homepage.t-online.de/HomepageClassic01/satl_93.pdfhttp://www.m-schmiechen.homepage.t-online.de/HomepageClassic01/Quas-steady_model_trial_1986.pdf



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2 Theory of theories 2.1 Evident principles

All our 'sound' inter-subjective, alias 'objective', knowledge is based on coherent (!), shared 'principles' (Bertrand Russell, 1912), i. e. on 'prejudices', as Mark Twain aptly noted in 1900. As their name and usage implies, not only 5 in the bible ("In principio Deus creavit …; In principio erat verbum …"), 'principles' are 'beginnings' 'origins', 'basic sentences' or 'axioms' of formal languages, depending on contexts.

Thus, if people jointly want to discuss and solve problems in an 'educated', efficient fashion, they only need to 'convene', i. e. come together, and agree on 10 their prejudices and on the rules of a sufficiently rich language to be used. In terms of the theory of science axiomatic systems based on 'evident principles' are nothing else but coherent 'conventions'.

Accordingly the title of my paper of 1980 came to mind: 'Eine axiomatische Theorie der Wechselwirkungen zwischen Schiffsrumpf und -propeller.' (Fritz 15 Horn zum 100. Geburtstag gewidmet. Schiffstechnik 27 (1980) 2, 67-99).

Any things else are logical and mathematical 'exercises', to be discussed further down. This approach reminds of course of Isaac Newton's 'Principia mathematica' and of Claude Shannon's use of George Boole's algebra.

Logicians tell us, that principles do not need to be 'evident'. But for the 20 communication in teams of problem solvers and with their clients, evidence on the level agreed upon, is of course prerequisite and efficient. 2.2 Pragmatic meta-principle

The meta-principle underlying my work since 1980 avoids any inherited superstition. In accordance with 'naked' pragmatism trustworthy trials are to 25 be based solely on few simple principles, the few parameters of which can be identified reliably.

The title of Dr. Schulze's talk 'Sea Trial Auswertung mit eingeschränkten Informationen und Instationaritäten' explicitly states, that the purpose of tri-als, validation of predictions independent of prior data, has still not been 30 understood. If the performance of a ship is of interest, we have solely to talk to the ship!

To introduce ever more complex models with increasing numbers of pa-rameters, 'coefficients', that cannot be identified, does not make sense, if 'properties' of real systems in terms of adopted conventions are of interest. 35 The values of the additional parameters have to be determined using addi-tional principles, their parameters to be looked up, e. g. in tables, they are not 'properties' looked for.

The case in question is validating powering predictions for contractual and/or scientific purposes. And the traditional approach reminds me of the old 40 lady, who knew, that the Earth rests on a turtle, and who on further question-

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ing replied: 'On turtles all the way down!' And I repeat the question 'At whom are we laughing?' of Mara Beller dis-

cussing Sokal's hoax (1999). I am not laughing at the old lady, but at physi-cists and cosmologists talking about gravity and at naval architects talking about trials. 5

For readers not (yet) used to lateral thinking I add, that the story of the old lady is not a joke, but an important parable, an example of Gödel's fundamen-tal proof, that no 'end' will be reached with additional conventions.

Thus naval architects could continue their way of 'research' forever, 'all the way down', if not somebody cuts off their support. I remember a former Di-10 rector at the Ministry of Research, who understood the parable of the old lady. 2.3 Model based conventions

As has been mentioned, conventions are ideally axiomatic systems devel-oped ad hoc. But to be useful for the treating real systems they cannot be pulled out of the hat. And sufficiently intricate formal systems cannot be in-15 duced from data, they have to be based on sufficiently rich models.

The case in question is the fundamental difference of displacement and en-ergy wakes behind ship hulls, impossible adequately to be dealt with in terms of the traditional frame work of conceptions and procedures.

Horn already adopted the model of an ideal propeller, an actuator disc, in 20 uniform wakes. This model permits to deduce the non-linear thrust deduction theorem (!) and a much simpler thrust deduction 'law', a 'nearly perfect' heu-ristical approximation (hpi_tha.pdf).

Both, the theorem and the 'law', clearly show, that traditional procedures and historical data are hopelessly inadequate for the analysis of trials. 25 2.4 Mathematical routines

And as shown by the analysis of my quasi-steady 'model' trial, the conven-tions adopted can only be handled using rule based symbols and correspond-ing programming systems.

Professional solutions require thorough understanding of the basic numeri-30 cal routines, particularly if advanced professional systems are being used. Thus the development of advanced numerical routines necessary requires co-operation with experts.

When trying to solve the system of non-linear equations in the final analy-sis of my 'model' trial a mathematician had to tell me, that I had grossly un-35 der-estimated the difficulty of the problem and to indicate the way out, to find the appropriate start values required.

One of the fundamental routines frequently required is solving systems of ill-conditioned linear equations. More than fifty years ago I have developed and since promoted a routine closely resembling today's standard, using SVD, 40

http://www.m-schmiechen.homepage.t-online.de/HomepageClassic01/hpi_tha.pdf



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singular value decomposition, i. e. 'analysing' the data in terms of ortho-normal functions constructed ad hoc.

But I still meet people, who are using hopelessly inadequate do-it-your-self routines based on Gauss' 'integrating' normal equation, filtering out all inter-esting information. Similarly Fourier transforms are often used ignoring the 5 conditions to be met, thus resulting in systematic errors.

Since many years I am using and recommending the intuitive Mathcad Pro-fessional environment, meeting all logical and mathematical requirements, including the transparent documentation, Claims to the contrary are based on plain ignorance of the problems faced in developing and testing involved rou-10 tines.

A further, important advantage of Mathcad is the ease to perform necessary and/or requested plausibility checks at any stage of an analysis. Procedures of trials analysis are not working like toasters, where the 'raw data' are put in and 'perfect results' come out. 15 2.5 Conceptions understood

Further details, e. g. my few conventions, are not of interest in the present context aiming at clear conceptions and understanding of problems and solu-tions, 'Anschauung' in Goethe's spirit, necessary to direct research worth that name. 20

Froude's naïve conceptional model of propulsion is not only inadequate for the purpose at hand, but the procedures to identify the values of the few pa-rameters suffers from the fact, that it is not applicable on full scale, Hull tow-ing and propeller open water tests are impossible at service conditions.

The only way out is to conceive conventions replacing hull towing and pro-25 peller open water tests. Until I came up with the conclusive solution I have tried different approaches based on heuristic approximations, which are now only of historical interest. Subjects of discussions are only my most recent procedures and results.

Twenty years ago, when the standard ISO 15016 was under discussion, I 30 have, based on a half-sentence in my METEOR Report, conceived very sim-ple conventions, applicable on model and full scale in the same way. In the past decades these conventions have been developed to maturity and success-fully applied in many delicate cases, most of them permitted to be published in papers, in lectures and on my website. 35

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3 Quasi-steady tests 3.1 Procedure aimed at

From the beginning the goal of my work has been to provide a procedure to identify the powering performance of full scale ships using very short tests during trials and monitoring at any service condition. without any body notic-5 ing, that such tests are being performed, as has been the case during the METEOR tests at heavy sea states, mostly in the November darkness at the Arctic Circle.

The first rule has already been mentioned: If the performance is to be iden-tified at a given state, only small, quasi-steady oscillations around that state 10 have to be performed. Large, fast oscillations cause problems that cannot and need not be solved.

Ideally the same procedure has to be performed on model scale, if scale ef-fects are under investigation. This rule has been observed in the METEOR project. 15

The analysis of the quasi-steady tests with the METEOR in the Greenland Sea and the discussion of the project have been published in the now histori-cal Proceedings of the 2nd INTERACTION Berlin 1991, all related files to be found in the Section 'Ship powering trials' on my website.

The quasi-steady 'model' trial, performed at VWS in 1986, to demonstrate 20 the feasibility of the procedure, has conclusively been evaluated only in 2019! The conceptual and numerical problems faced turned out to be much more intricate than expected.

The ten files, published on my website (Quasi-steady model_trial 1986.zip), provide the common thread for following discussions and may be considered 25 as stepping stones for further developments and future standards.

Of particular Interest for the complete analysis of hull-propeller interactions is the possibility to identify the thrust, which routinely cannot reliably be measured on full scale. 3.2 Tests conducted 30

Quasi-steady propulsion tests on full scale take place in noisy environ-ments at controlled rates of shaft revolutions.

In order reliably to identify the powering performance under these condi-tions, more or less random test variations of shaft revolutions, independent of the noise, have to be performed and recorded. If these requirements are ig-35 nored, the data of the tests are definitely useless, the tests have to be re-peated correctly!

In order to avoid systematic mistakes due to feed back of noise all data measured have to be correlated with the test variations superimposed. Hence on full scale the analysis has to be based on results of these correlations. 40

http://m-schmiechen.homepage.t-online.de/HomepageClassic01/news_flash.htm#interact



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This procedure has been applied in the METEOR project. But at that time the test variation used was only a single saw tooth. As discussed in the follow-ing, repeated oscillations are necessary.

The quasi-steady 'model' trial, freely moving under the towing carriage, manually controlled to avoid collisions with the boundaries, permitted to de-5 velop a general evaluation procedure, independent of special properties of the test variations.

By the way, after expensive 'automated' collisions, we at VWS had earlier turned to manual control of quasi-steady tests, e. g. at manoeuvring tests in restricted waters in and around the model basin and at sea-keeping tests with 10 hydrofoil-boats in transient waves. 3.3 Data analysed

The essential steps in analysing the data, i. e. in case of full scale tests the measured data correlated with the test signal, have been demonstrated in the analysis of the 'model' trial: 15

to identify the steady states passed and to be analysed for the currentprevailing and the propeller performance (mod_5_stat_rev6.pdf) and

to identify the propulsive efficiency from the data between the steadystates passed (mod_6_prop_rev6.pdf),

Essential for these procedures is the perfectly reliable differentiation routine 20 developed and published among many others (mod_3_rout_rev6.pdf).

At the model trial the values of the acceleration were less than 10^-4 g, far from being negligible in view of the large inertia of the model, resulting in values of rates of change of the kinetic energy, large enough to upset any bal-ance of powers, if not properly accounted for. 25

Quasi-steady tests on full scale are necessary as no other 'well defined' forces except inertial forces can be applied. The problem is evidently not to estimate the very small value of the longitudinal hydrodynamic inertia, but reliably (!) to estimate the value of the total inertia of the vessel at the given service condition. So far I do not see a way to identify that value on full scale. 30 3.4 Quintessence

The quintessence of the method described is the possibility to identify in very short time a considerable number of steady states passed and in addition to identify the propulsive efficiency.

At the 'model' trial ten steady states have been passed during two minutes, 35 crudely corresponding to half an hour on full scale. Hence the belief, that the 'gain in time' is due to 'acceleration' happens to be plain superstition. While the steady states passed are rather randomly distributed in time, on the plots of results they look nicely threaded.

Evidently the STAimo procedure, using the model propulsive efficiency as 40

http://m-schmiechen.homepage.t-online.de/HomepageClassic01/mod_5_stat_rev6.pdfhttp://m-schmiechen.homepage.t-online.de/HomepageClassic01/mod_6_prop_rev6.pdfhttp://m-schmiechen.homepage.t-online.de/HomepageClassic01/mod_3_rout_rev6.pdf

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joker, and adopted by Full Conference of the ITTC 2014 at Copenhagen is not acceptable for purposes of validating powering prediction methods.

Very short quasi-steady tests, permitting to identify or monitor the power-ing performance in every detail, can of course be repeated for many purposes, not only to establish the repeatability, but to identify the influences of trim, 5 draught, speed and sea state, etc, etc, …



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4 Steady states analysed 4.1 Started as intermezzo

Only in 1998, during discussions of drafts of the standard ISO 15016 I started to think about the analysis of traditional powering trials. My hope was, that my solution of this much simpler problem, would be more acceptable for 5 the community than quasi-steady trials,

My proposed alternative draft (trl_prp.pdf) has been filed as 'Informative' by the Japan Marine Standards Organisation (JMSA) under ISO/TC8/SC9/WG2/N28 dated 1998-06-23.

In the 'Bibliography on ship powering trials the entry 'Contributions con-10 cerning the proposed ISO Standard 'Guidelines for the assessment of ship speed and power performance by means of speed trials'' provides links to all documents related to the early discussions and developments.

My proposal was in fact already rather detailed and theoretically solidly founded and has since been successfully developed to maturity and applied in 15 a number of delicate cases, two of them published in my METEOR Festschrift 'From METEOR 1988 to ANONYMA 2013 and further' calling for: 'Future Ship Powering Trials and Monitoring Now!'

The ANONYMA and the Post Anonyma Trials Evaluations (PATEs), per-mitted to be published in every detail, are to be found in the first two volumes 20 of thFestschrift (Festschrift_1.pdf; Festschrift_2.pdf). A recent, much simpler example of my procedure is the re-evaluation of the REGAL trial (REGAL_trial_6.pdf).

But only during the advanced evaluation of my model test of 1986 I real-ised, that the procedure was also instrumental for 25

reliably evaluating the steady states passed during quasi-steady trialsand subsequently for

rigorously scrutinising traditional trials procedures, all of them sufferingfrom problems caused by ignoring the simple principle stated. Theseproblems cannot be solved by the methods, which have caused them!30 As has been mentioned, 'adding turtles all the way down' is not a ra-tional procedure.

4.2 Power conventions The conventions, proposed twenty years ago and developed to maturity dur-

ing a number of successful applications, consist conveniently of two separate 35 parts. In both parts the values of the few parameters are obtained as solutions of systems of linear equations. Not only in these two cases have the residua to be monitored by checking their normal distributions.

The first part permits jointly to identify the parameters of the conven-tion concerning the current prevailing during the test, and thus to deter-40

http://m-schmiechen.homepage.t-online.de/HomepageClassic01/Festschrift_1.pdfhttp://www.m-schmiechen.homepage.t-online.de/HomepageClassic01/Festschrift_2.pdfhttp://m-schmiechen.de/HomepageClassic01/REGAL_trial_6.pdfhttp://m-schmiechen.homepage.t-online.de/HomepageClassic01/trl_prp.pdf

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mine the velocity through the water, and of the parameters of conven-tion concerning the power supplied by the shaft relative to the water.

The second part permits to identify the parameters of the conventionsconcerning the powers required for the propulsion of the vessel underinvestigation in water, wind and waves.5

As all conventions, those mentioned are not 'true', but acceptable working hypotheses, and useful for the purposes at hand. Hence I have tested and ap-plied mine, to demonstrate, that they are in fact useful for the analysis of the steady states identified in quasi-steady and in traditional trials. 4.3 Power supplied 10

My procedure to identify the current, in the meantime applied by some in-stitutes, is in fact the only meaningful in the coherent context. It works relia-bly at any service condition, gets along without expensive additional instru-ments and measurements and, most important, without any 'extra' calibration.

Although twenty years ago my method has put an end to the invention of 15 instruments, that cannot be calibrated, development proposals and projects concerning such inventions are irresponsibly still being advocated by 'peers'. The president of the Max-Planck-Gesellschaft with more than ninety research institutes has recently in an interview acknowledged deficiencies in evaluating

20 research proposals and results due to inbreeding (DIE ZEIT 74 (2019) 52, 40). The convention concerning the shaft power supplied implies the losses in

the shaft. Thus these losses need not to be 'guessed', this 'turtle' is not re-quired, different from traditional procedures. Thus, to be precise, my term 'propeller performance in the behind condition' requires the addendum 'includ-ing the shaft losses'. 25

The procedure has been stable and sensitive from the beginning, ready to be adopted as standard. Thus it permits to scrutinise the data! In case of the stan-dard ISO 10916 even a misprint in the data underlying the example has been revealed. And the very small tidal drift in the towing tank at the model during the 'model' trial has reliably been identified. 30

On full scale the measurement of the shaft power cannot properly be cali-brated, it has is based on additional conventions with parameters taken off the shelf. This fact implies systematic errors up to two per cent in the fundamen-tal magnitude! To my knowledge 'precise' instruments are marketed without mentioning this inherent uncertainty. 35

In the METEOR project the hollow shaft had been calibrated as six-component balance accounting for all cross-talks in the full range of service loads. Only in this exceptional case the additional conventions mentioned have not been necessary.



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4.4 Powers required The conventions concerning the powers required for propelling a vessel in

water, wind and waves are purposely simple. While the speed through the water can be identified reliably as has been discussed, observations of wind and wave are usually very crude, thus data available for the identification of 5 the relative speeds through wind and waves are particularly poor.

In case of the wind measurements are performed using anemometers cali-brated in uniform wind. But the data obtained are sufficient to identify the only parameter in question. These can not only be used to derive the no wind condition, but to account for different wind conditions. 10

In case of waves the situation is much worse, but any information concern-ing the sea state available can be used, as has been done in various test cases.

In both cases monitoring the residua is mandatory. Deviations from the normal distribution may simply be reduced by modifying the conventions, which are working hypotheses. 15 4.5 Traditional trials

As has already been mentioned traditional trials suffer from serious defi-ciencies, 'starting' with the use of arithmetical averages of the short time aver-ages recorded. But thoughtlessly taking 'ordinary' averages is often in princi-ple utterly wrong! 20

The slim volume 'Wer falsch rechnet, den bestraft das Leben' (Christian Hese, 2014) provides a number of very instructive examples. As I experienced long ago, while testing my procedure, values at steady states had to be used in order to avoid systematic errors due to rates of change of the kinetic energy.

A closer look at data of traditional trials (and model tests) revealed, that 25 such trials are not steady at all. And due to the very large values of inertia involved even very small values of accelerations are causing 'considerable' values of the rates of change of the kinetic energies, upsetting any power bal-ance, if not accounted for appropriately.

Even worse is the fact, that the steady states determined from very trials 30 taking very much time at changing conditions, are representing a set of states rather 'far away from' the (contracted) state under investigation, in terms of statistics belonging to different ensembles, e. g. at runs up and down wind.

In case of the quasi-steady trials promoted the steady states identified from tests of very short duration are representing a cluster of states very close to the 35 state under investigation, belonging to an ensemble proper permitting the ap-plication of the elementary theory of samples.

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5 Conclusions 5.1 Implications

The preceding exposition of principles permits to discuss the importance of trustworthy trials for the different purposes of

validating contracted predictions and5 validating prediction methods in general.

The first case is of 'interest' in view of contractual penalties. The STAimo procedure currently 'legalised' by IMO, is essentially MARIN's misleadingly so called 'direct power method', which is based on the propulsive efficiency determined from results of model tests. In view its regress on model data, the 10 STAimo procedure does not meet scientific standards.

According to the rules of standards organisations, e. g. DIN, ISO, standards do not need to meet the state of research, but represent the consensus on the practice to be followed in groups 'interested' in a standard. No further com-ment! 15

As I have shown in quasi-steady trials the propulsive efficiency can be de-rived from the ratio of the values of the power required and the power sup-plied between the steady states passed. 5.2 Further problems

The work so far does of course not solve all problems, but the paradigmati-20 cal solution of the 'model' trial provides a solid basis for solving further prob-lems.

Based on the experience with the quasi-steady 'model' trial a quasi-steady full scale trial has to be performed as has repeatedly been proposed, e. g. to the project manager of MARIN's JIP 'JoRes'. Further the method of quasi-25 steady monitoring the propulsive performance under service conditions has to be developed to maturity.

Another problem is model testing of very large, very slow 'steaming' ves-sels. If the values of wave resistance of hulls are small compared to the values of the frictional resistance the traditional model testing is no longer appropri-30 ate. Following your experience I have already investigated systematic errors resulting in predictions (On_power_predictions.pdf).

Most efficiently all the problems ahead can be solved in cooperation, end-ing up in consensus on lasting standards meeting scientific standards. But despite the existence of ITTC member organisations tend to adhere to the 'in-35 credible' doctrine 'Not invented here!' and to forget, that who reads and under-stands what he reads is in advantage.

With kind regards yours, Michael Schmiechen.



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6 References 6.1 Talks delivered

at the 13 Forschungsforum of SVA, and referred to: Froitzheim, S., SVA: Instationäre Modellversuche Gegenwart und Zukunft. Masilge, Christian, SVA: Vorstellung der aktuellen Forschungsprojekte der 5

SVA. Rüggeberg, Thomas, BMWi: Maritime Forschungsstrategie des Bundes. Schulze, Reinhard, SVA: Sea Trial Auswertung mit eingeschränkten Infor-

mationen und Instationaritäten. 6.2 My related papers 10

…referred to and to be found on my website in the 'News flash' or in the pertinent Sections, in their Bibliographies in particular, or directly accessed via the links provided.

For convenient reading the present paper, as many others, has been de-signed to be printed and bound as DIN A5 (21 x 15 cm) brochure 15 6.3 My bibliographies A complete coverage of published explanatory papers and letters up to mid

2014 with links is to be found in the pertinent Sections on my website and in my opus magnum, so that there is no need for repetition.

More recent, even up-to date are the entries in the section ‘The 3rd, virtual 20 INTERACTION 2017 cont'd’ of the ‘News flash’.

The URL ‘http://d-nb.info/1078156735’ leads to my Catalague entries atDeutsche Nationalbibliothek and thus in future, after I passed away, tomy permanently archived website. Recently introduced links to papersusing the URL http://m-schmiechen.homepage.t-online.de/ will then ofcourse no longer work.

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7 Author 7.1 Contacts

30 apl. Prof. Dr.-Ing. Michael Schmiechen Bartningallee 16 10557 Berlin Germany [email protected]

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7.2 Website www.m-schmiechen.de

http://m-schmiechen.deMichael SchmiechenDurchstreichen

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8 Notes

on evident principles of quasi-steady ship powering trials ... · 3.1 procedure aimed at 8 3.2...

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