Proceedings of the Symposium Aspects of Navigability of Constraint Waterways, Including Harbour Entrances, Volume 4, Delft, The Netherlands

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Amine

ro.

SYMPOSIUM

aspects of Vol .4

navigability of

constraint waterways,

including

harbour entrances

TECHNISCHE UNIVERSITEIT

Laboratorium voor

Scheepshydromechanica

Archief

Mekelweg 2, 2628 CD Delft

Tel.: 015 - 786873 - Fax: 015_{- 781836}

delft 1978

delft,the netherlands,april 24 -27,1978

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lume

--gmceed

nga

delft 1978

-aspects of

navigability of

constraint waterways,

including

harbour entrances

delft ,the netherlands,april 24-27,1978

volume 4

late papers

discussions

final session

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-SYMPOSIUM

aspects of

navigability of

constraint waterways,

including

harbour entrances

- Section on Maritime Hydraulics, both of International

Association for Hydraulic Research Organized by:

- Delft Hydraulics Laboratory - Netherlands Ship Model Basin

Symposium Committee

M. Hug President of IAHR

Willems President of PIANC

M. Oudshoorn Rijkswaterstaat (Public Works

Department)

J. D. van Manen Netherlands Ship Model Basin

J. E. Prins Delft Hydraulics Laboratory

Scientific Committee

L. A. Koele

B. M. Knippenberg

J. P. Hooft

J. J. van der Zwaard J. W. Koeman G. Abraham J. P. Lepetit Organizing Committee C. H. de Jong M. W. C. Oosterveld L. R. de Vlugt

Rijkswaterstaat (Public Works Department)

Rijkswaterstaat (Public Works

Department)

Netherlands Ship Model Basin Delft Hydraulics Laboratory

Delft Hydraulics Laboratory

IAHR (Section en Fundamentals JAHR (Section on Maritime Hydraulics)

Rijkswaterstaat (Public Works

Department)

Netherlands Ship Model Basin Delft Hydraulics Laboratory

(4)

Opening by M. Hug (IAHR)

Dear President, dear colleagues

I feel greatly honoured to be invited to open this

symposium concerning the "aspects of navigability

of constraint waterways, including harbour

en-trances". I assume this honour to be mainly due to

my present quality of president of IAHR but I want

to express the personal pleasure to be with you to

day and to explain the reasons of my particular

sensitivity to the invitation of the organisers: the

Delft Hydraulics Laboratory and the Netherlands

Ship Model Basin. Although my initial education

was civil engineering-orientated, I have later

spent many years in various aspects of hydraulic

machinery. During this very interesting period of

my life I was fascinated by the possibilities

offered at the intersection of two disciplines:

civil engineering and mechanical engineering

specially when considered from a double view

point: research and engineering pratice. I think

that this symposium offers a good example of such

possibilities. The intersection between two

disci-plines, here civil engineering and naval

architec-ture is expressed between the two organisers and

the double view point is emphasized by the fact

that this symposium has been initiated through a

joint proposal of the Committee on Fundamentals

and the Committee of Maritime Hydraulics of IAHR.

The Committee on Fundamentals fosters the basic

research approach and the Committee of Maritime

hydraulics bridges the gap between applied

re-search and engineering practice. In that respect

a special mention has to be made of the

cosponsor-ship of PIANC. I appreciate very much the

inte-rest shown by PIANC in this symposium and thank

the president Willems for being also with us to day.

When one wants to make progress in a given field,

three main means of action can be used

simultane-ously or one by one. These are:

observation of natural full scale conditions

physical modelling

mathematical modelling.

Both physical and mathematical models are

as-sumed to be satisfactory when their results check

against the results of natural conditions

observa-tion. From then on they are used to test new

de-signs or new operational rules. In the particular

case of navigability in constraint waterways, I

want to emphasize the difficulties attached to each

of the three main means of action I was pointing

out:

Observation of natural full scale conditions:

Data on the behaviour of large ships in

con-straint waterways are very scarce due to the

difficulty of measuring techniques. The human

element does not make field measurements any

easier. The very high operational cost of large

ships leaves little hope of a rapid increase of

such data. The range of such data will in any

case stay limited because of the impossibility

of varying the geometry.

Physical modelling: The validity of physical

modelling is limited by low Reynolds numbers

and the associatial large scale effects on drag

and shear forces.

Mathematical modelling: A purely theoretical

approach of navigability in disturbed shallow

water does not seem realistic. Simplifying

hypothesis can be used and empirical

expres-sions derived. They may lead to numerical

mo-dels which will suffer from limitations

corres-ponding to the simplifications made. I must by

the way apologize to those who would use in

such a case the word "semi-empirical". For the

sake of a certain logic I have always been

in-clined to follow those who thought that there is

no such thing as a semi-empirical approach.

This very short survey convinces me that only a

coordinated effort along those three lines can

produce real progress towards a better knowledge

and I hope that the present symposium will add a

significant step in that direction to meet the need

of reliable tools for simulating the various factors

involved.

The need for such tools can be appreciated,

accor-ding to the papers presented here, along three

lines:

harbour design - how to minimize the cost of

the project and at the same time ensure

maxi-mum harbour accessibility and operational safety?

navigation aids - how far can one hope to

pro-gress in that direction? Is a fully automatic

control advisable? Is it possible? At which cost?

Would a significant increase of operational

safety be achieved?

pilot training - on this subject I would like to

underline the good crossfertilization that has

been achieved between research, engineering

and pilot practice. The close association with

pilots is a guarantee that any new development

will have a higher practical efficienty because

the attention of the design engineer is then

properly focussed on operational experience.

(6)

The importance of the human factor in this case

is so great that the interaction between daily

practice, engineering and research has to be

stimulated even further.

I do not think necessary to insist upon the

im-portance of human factors. I would nevertheless

like to make another remark which goes far beyond

the scope of this symposium. Whatever the field

of action .. politics, economics, health,

archi-tecture, engineering, ... a man (or woman) has

to make decisions. The easy ones are those

founded on tested knowledge, there are also

de-cisions that must be made even though all factors

may not be completely mastered. I have the

im-pression this kind of decision becomes more and

more difficult to make for various reasons:

In-creasing sensibility of the public opinion to the

drawbacks of new projects, increasing necessity

of proving beforehand that public safety will not

suffer from such projects.

The borderline between tested and untested

know-ledge is not necessarily clearly defined. When

a decision implies factors lying on this

border-line, one must initiate,by the most appropriate

research, progress in the direction needed.

At the same time action should not be to much

de-layed, the full dignity of man may very well reside

in the readiness to take risks. Today on difficult

subject matters, the individual knowledge and

responsibility has less meaning. What is of greater

significance is the knowledge of teams of scientific

or engineering bodies. The responsibility of those

teams and bodies in using acquired knowledge and

defining acceptable risks has replaced to some

extent the individual responsibility. To that extent,

the efficiency of an organisation to stimulate the

exchange of knowledge, to define knowledge

boun-daries and need for progresses, has become an

important factor to make sure that all available

knowledge has been or will be used and the

re-maining risks correctly assessed.

This is, in my opinion, the very reason why the

human aspects of a meeting between people

wor-king in various disciplines with different

view-points towards a common goal has become more

and more important.

The present symposium is a good example of such

a meeting and will play an important role for

engineering and research decision making. In

that respect I want to point out the outstanding

contribution of the scientific committee which will

be presented in a few minutes by Dr. Abraham.

This introduction is an effort to clarify the scope

of the symposium and provide guidelines for

ex-changes between participants. It will undoubtedly

increase very much the efficiency of this

sym-posium. I am very sensitive to this effort and as

president of IAHR, I express the wish that this

introduction be used as a model for similar

meetings.

I give now the chair to Prof. Willems, President

(7)

Opening by prof. Willems (PIANC)

Dear President, Dear Colleagues

It is for me an honour and a pleasure, to take the

floor, on behalf of the members of the Permanent

International Association of Navigation

Congres-ses.

The Permanent International Commission of our

Association was very much in favour of the

co-sponsorship of the Symposium on "Aspects of

Navigability of constraint waterways, including

harbour extrances". It is the second time that

PIANC co-sponsors a Symposium of this

Asso-ciation. The 1st time was for the Symposium on

River and Ice, held in Budapest in 1974 and which

was a great success.

This second joint Symposium of the International

Association for Hydraulic Research and of our

Association fits very well within the framework

of the activities of both Associations. In this

connection it is important to stress that during our

XXI Vth Congress at Leningrad in 1977, the

dis-cussion of Subject 2 of Section II - Ocean

Navi-gation: "Improvement and maintenance of navigation

channels and control of the regime in estuaries

in relation to the energy due to tidal movement,

waves and swell at the extrance" lead to the

con-clusion that it is necessary to conduct further

comprehensive research aimed at the development

of unambiguous scientific recommendations on all

aspects linked with design and operation of sea

routes. The most complete and reliable results

can be obtained by use of field and model

investi-gations. Physical and mathematical simulation

should be based on field data. These model

inves-tigation and simulation tests will be dealt with

during this Symposium, and we do hope that it

may stimulate continuous collaboration, between

the institutes using simulators and engineers who

need the results to design navigation channels.

There are a lot of problems which call for a

scientific based solution. Since about twenty

years, the International Association of Hydraulic

Research has been invited to request its members

to furnish papers for PIANC's Quadriennal

con-gresses and to send an official observer to these

congresses. Similarly, the colloboration of

mem-bers of your Association is at present appreciated

in PIANC's International Study Commissions,

such as:

the International Commission for the study of

Waves;

the 1st and 2nd International Oil Tankers

Commission;

the International Commission for the Reception

of Large Ships.

At present one can no longer conceive any

reali-zations in the field of Hydraulics without a

funda-mental contribution from the Hydraulics

Labora-tories, within the framework of:

the design of maritieme ports;

the improvement of free flowing rivers;

the construction of canals;

the filling and emptying of lock chambers with,

inter alia, the phenomena of cavitation;

-the bottom and surface flow of movable barrages,

etc..

On behalf of the members of PIANC, I sincerely

thank our sister Association IAHR to have taken

the initiative of this joint-symposium and I do

be-lieve that a close collaboration between our two

organisations is the best guarantee to enable us

to solve all hydraulic problems. May I

congratu-late the Organizing Committee i.e. The

Rijks-waterstaat, the Netherlands Ship Model Basin,

and the Delft Hydraulics Laboratory for the

per-fect organization of this symposium. With such an

interesting program and a series of excellent

scientists and engineers taking the floor, this

im-portant scientific event will certainly be

success-ful.

(8)

Discussion on the Introductory remarks on investigational

techniques by the Scientific Committee

Question asked by H. Velsink, NEDECO.

Question: Clearly the state of the art regarding

the navigability of constraint waterways has

pro-gressed in the past years. It appears worthwhile

to reflect this progress in new and more elaborate

guidelines to be drawn up under the auspicies of

IAHR/PIANC.

A certain reluctance and scientific reservation is

quite well understood, as the extent of

present-day knowledge is still small as compared to the

vast area of unknowns.

However, still todate and particularly in the

developing world, harbours are being built - and

often at the expense of considerable national

fi-nancial sacrificies - that demonstrate a

discon-certing abscence of insight in the basic criteria

for navigability and in the limitations of

manoeu-vrability of ships.

Question asked by I .W. Dand, National Maritime

institute (UK).

Question: I would like to ask the author what force

is propelling the ship in figure 17?

None is shown and it is stated that F5=0.

Surely in such a case the ship would not move

forward and A h would certainly be zero? Should

a thrust from the propeller be shown which

approximately balances out the drag force (not

shown in figures 16 or 17) so that a situation

simi-lar to that shown in figure 16 results? Has the

author any experimental data to support his

con-tention that it is "the towing force which causes

the difference in water level fore & aft of the ship"?

In many instances time and funds for proper

inves-tigations are non available and/or the

understan-ding for their necessity are non-existent.

In this context the existing guidelines from an

authoritive body like PIANC already serve a

use-ful purpose.

But a further elaboration and updating appears

desirable at this stage - notwithstanding the

dangers involved in the generalization processes

involved in setting out any and all guidelines.

Would the scientific committee agree and take the

necessary steps?

Discussion on the General lecture by P.A.Kolkman

Answer:fig.17: There is no external force. The

ship propeller induces a force equal to the

resis-tance force, so the total ship + propeller system

does not exert any force on the water.

Experimental verification shows the absence of

long waves ( except during acceleration) of

self-propelled ships and the occurence of waves at

towed tests. An exact verification of the cases of

fig. 16 and 17 is difficult because they treat

stationnary conditions and an extreme long testing

canal is needed. Fig. 25 and 27 however show

qualitive agreement with tests. Parts of the theory

have been set up during preparation of this lecture

and quantitative comparison with experiences still

have to be done. It was not my intention to present

ready applicable rules, but I wanted to show

or-ders of magnitudes which result from thought

ex-periments.

(9)

Question asked by L. Ribadeau Dumas, Service

des phares et balises, France.

Question: I believe necessary to have an idea on

the magnitude of errors resulting from linear or

other approximation and also from errors between

mathematical models and actual ships.

We need to know this magnitude for adopting

secu-rety margins when designing a port.

Why this practical point of view could be inserted

in mathematical study?

Answer: I agree on the need of knowledge about

accuracy of used methods, mathematical and scale

models. When errors are found, the causes must

be analyzed; non-linearities which were not

in-cluded in computations, effects of density

strati-fications etc. can play, but also whether the exact

boundary conditions were introduced is an utmost

important point. In general it is difficult to obtain

enough data from prototype to arrive to a detailed

analysis, so mainly comparison scale models

ver-sus hydraulic models is done. An advantage of the

mathematical models is that the gouverning

para-meters (roughness, eddy viscosity, wind effect,

coriolisforces, boundary conditions) can be easily

varied around the assumed values, and when the

result is very sensitive to those variations the

results should be used prudently.

There is a difficult point in organizing a

systema-tic evaluation of used methods in view of a really

occuring condition; when there is no set-up of a

new project no money is available and the best

thing to do should be to rebuild or adjust a model

such that all geometry and boundary conditions

are fullfilled.

I am afraid that remarks like Mr. Ribadeau Dumas

makes will be heard also in the future, on which

the researcher will answer that he feels his

methods are reliable because his basic

assump-tions are logic and emperical coefficients used

are verified under schematized test conditions.

Question asked by N. King, U.S.A.

PMS 304/DTNSRDC

(Concerned with mathematical modeling of

back-ground flow pattern or "environment" in confined

waters -scale effects- as it affects ship designs

(maneuvering aspects)).

Question: In design of harbors and/or studies of

flow patterns resulting from ships in restricted/

confined waters (e.g. channels), how critical a

parameter is time - in modeling - time with respect

to kinematic scaling and to "memory effects" of

local flow?

In a busy harbor, ships maneuvering (and their

associated disturbances) should affect

"back-ground patterns" for other ships. In confined

waters are the disturbances of passing and past

ships important to ship maneuvering studies?

Are memory effects important? In the design cycle?

Answer: The mathematical modeling of the non

stationnary geometry (ship boundarys moving

to-wards the fixed waterway boundaries) is just at

the beginning, where till now only the potential

flow method is used (see paper 28 of Yeung) and

this calculation does not comprise memory effects.

In my used example of a sudden narrowing of a

canal profile (fig. 28) or the transverse harbour

(fig.30) it is shown that waves are produced, and

those waves reflect and come back on a later

moment. Eddies can remain a long time and those

are still not or poorly reproduced in mathematical

models.

Comment, given by J.P.Lepetit, L.N.H. Chatou.

I am more optimist than the author about the

capability of 2-dimensional math.models to

re-produce large eddies. Several laboratories,in

particular ours, have succeeded in reproducing

such eddies without adjusting carefully the eddy

viscosity coefficient with a good agreement

com-pared to field data.

Question asked by D. Jose Pulido Ortiz (Ph.D)

California Institute of Technology.

Question: Before a hydraulic model is designed

what will be the main consideration and the

selec-tion of appropiate scale for a waterway

between two rivers in my country:

Grijalva-Coatzacoalcos in the Gulf of Mexico distant apart

230 kms. if that distance is parallel to the coast

in alluvial ground? and how will be approximately

the cost for a study in a hydraulic model?

and other question: should be better that the canal

works the water of both rivers, or owing to the

fact that the canal projected is close to the sea,

can be worked with the seawater, taking in

account that there are close to the coast about

4 lagoons that runs parallel to the coast an their

main dimensions are also parallel and can be used

as tanks of equilibrium for maintain a level

con-stant?

Answer: A question of choosing a scale for a

model and costs involved can only be done when a

complete analysis of the problems is made based

on complete data. A new canal of 230 km, filled

from rivers or from seawater: one should spend

5 - 15% of the execution costs anyhow to design

and research, one good idea can safe already a

lot of money. Experiments in models are not

al-ways needed and before considering them a lot of

thinking and designing must be done already. That

is one of the reasons that institutes like the Delft

Hydraulics Laboratory does also hydraulic

con-sulting, literature documentation, hydrographic

survey, to assist also in preliminary stages

of a

project.

(10)

Question asked by J . A. Svendsen, ISVA,

Institute of Hydrodynamics and Hydraulic

Engin-eering, Lyngby, Denmark.

Question: Asked for canonical studies of the

problem of change in ships head (sailing direction)

at the entrance of harbour entrances with cross

current outside.

Answer: The most systematic studies are done

with help of the ship manoeuvring simulator of the

NSMB at Wageningen, using the restricted depth

manoeuvring coefficients of VLCC's. These studies

have been done for several harbours. My personal

impression is that when the background flow

pattern is given (and not too unevenly distributed

in vertical sense) that these manoeuvring

coeffi-cients remain valid at harbour entrances. The

determination of the flow pattern however will for

those conditions need a hydraulic model on an

appropriate scale.

Discussion on the General lecture by A.J.Hermans

Question asked by W. Beukelman, Delft University

of Technology.

Question: Why does the author expect that strip

theory may be applied for vertical motions in

shallow water, but not for lateral motions (page 7,

lines 57-60)?

Viscous influence might be more important for

vertical than for lateral motions for the case of

normal wave frequencies.

Answer: The remark on the applicability of strip

theory to the lateral motions concerns the fact

that in shallow water with small draft and depth

ratio, the effect of blockage is important. The

water is forced to flow around bow and stern

in-stead underneath the ship; therefore the basic

asumptions about the order of magnitude of the

velocity components as mentioned on this page are

not fulfilled and strip theory cannot be applied.

Nevertheless it is expected that potential theory

gives fairly good results as has been shown by

Van Oortmerssen. On the other hand friction

effects may be larger for heave than for sway.

Question asked by E. Tesaker, VHL, Trondheim,

Norway.

Question: In the lecture, reference was made to

the Europoort Study where self-propelled models

were used to some extent in a distorted model.

Where the ships also distorted?

Answer: In the distorted Europoort model no

self-propelled ships were used. A towed plate in the

dimensions of a distorted ship was used for

quali-tative comparison of geometries and flow patterns.

This was done before by means of forces

calcula-ted by using the lift coefficient of ships plus that

the angle between flow and ship was determined

from the flow patterns. Both methods agreed

qua-litatively and the plate tests permitted a quicker

analysis.

Question asked by C.L. Crane Jr., Exxon

Inter-national Co. New Yersey, U.S.A.

Question: Are you aware of experimental or

theo-retical determinations of forces on ships hull in

a 2-layer water current? (Shallow water currents

from different directions).

Answer: This is an interesting problem raised

by Mr. Crane. The_only results for a ship sailing

in a layered medium I know of, are experiments

carried out of a ship sailing in a shallow layered

medium at rest. These tests are carried out for

the Hoek van Holland entrance. I did some

theore-tical work for the influence of a layered medium

on squat. It turned out that the application of

slender body theory as explained in my paper is

possible. These results will be published in the

near future. I did some quick calculations for the

interesting case of different velocities as Crane

mentioned, however, with identical directions.

My first indication for squat is that the same

re-sults can be used as described in the paper using

a modified Froude number. I am sure that the

in-fluence of current from different directions can

be determined as well. The influence on the

manoeuvering coefficients will be considered in

(11)

Question asked by Prof. R.W. Yeung, Mass.

Inst. of Technology.

Question: Two comments I would like to make on

references quoted. First, there is a physical

explanation for the "wild" behaviour of added mass

for a ship oscillating near a wall. This maximum &

minimum behaviour is associated with a "resonant"

motion of the "well of water" between the ship hull

and the wall. The second remark is fig. 19 of the

lecture is extracted from the preprint of the Tuck

& Newman paper of the 10th ONR Symposium. The

original calculations had some error, the

correc-ted version is given in the final proceedings of

the Symposium.

Answer: His comment on the wild behaviour of the

added mass for a ship oscillating near a wall is

correct. Therefore it is hard to believe that these

results are useful for ship manoeuvering, because

in that case the physical phenomenon is quite

dif-ferent and a difdif-ferent procedure has to be followed

to determine the added mass term. Van

Oortmers-sen applied his results to the case of the

oscilla-tory motion of anchored ships. In that case the

physical circumstances are similar as those of the

tests to determine the coefficients.

Figure 19 has been extracted from the preprints

of the Tuck and Newman paper indeed. The

correc-ted version can be found in the final proceedings

of the 10th Symposium on Naval Hydrodynamics.

Discussion on the General lecture by

C.L.Crane,Jr.

Question asked by Ronald Gress, US Coast Guard.

Question: In your paper you discussed combining

techniques to create a new "hydrid" technique or

approach (e.g. a hydraulic model and a computer

simulated control function).

What about the approach of using one or more of

the techniques you identified in succession, using

a full computer simulation for example to increase

the experimental design efficiency when going to

"more accurate" and more expensive techniques

such as a ship simulator or ship trial? With regards

to "figures of merit" perhaps no single approach

is the best. Comment?

Answer: Mr. Gress makes an excellent point in

suggesting that full computer simulation might be

used as a first stop before going to a "more

accu-rate" technique such as a real-time simulator,

hydraulic model, or ship trial. In this

way the

be disposed of, allowing greater

_{concentration of}

time and funds on more critical questions. A

rela-tively great number of parametric

_{variations could}

be made in this manner, hopefully high-lighting

the main concerns, where human factors

_or

com-plex hydraulic phenomena are not adequately

represented in the full computer simulation.

(12)

Discussion on the General lecture by G.Wiedemann

Question asked by 1 . A. Svendsen , I.S.V.A.

Denmark.

Question: Why fig. 11 seems to show a gradual

decrease in width of the navigation channel as the

depth has increased over the years.

Answer given by G. Wiedemann.

Answer: In headlines the chances in the geometry

of the underwater profile -see Fig. A- of the

navigation channel are the result of a combination

of several groups of factors. Besides important

detailing factors in the sphere of coastal

engin-eering there are also the more functional directed

factors regarding the operations to be performed

for the assurance of safe and expeditious

VLC-channel-transits of course still in relation with

the occuring relevant navigational circumstances,

the available instruments and the existing

confi-guration of the underwater channel. Shortly three

detailing factorgroups are distingued:

A grow in operational experience as available

in the navigation area; the effects of this experience

is partly documented as derived and evaluated

from measurements and observations in nature in

foregoing project stages. In a lot of cases the

interpretation of these data could be founded by

means of the results of basic research.

The

com-bination of documented experience and verificated

results of laboratory tests regarding possible

future states was still input for the design

propo-sition of the next configuration of the navigation

channel to be realised in the project.

A stepwise realisation of additional

"instru-ments" for the executions of the several operational

tasks during VLC-channel-transits. The

develop-ments of some of these tools and improvedevelop-ments

in

the functioning of it were prepared via research,

design and experiments in nature during the time

intervals between the different realised channel

configurations.

Again data about the functional contribution to

VLC-channel-transit operations were collected in

the stages after realisation as described

under

point 1.

Examples are the Holland Chain positioning system,

the provisional hydro meteo expectation system,

improved and more pronounced procedures for the

different operational tasks, the trainingsystem

for experienced pilots, information text

books.

Developments in the available operational

capacity. Besides an increase in the required

capacity especially developments in the available

operational capacity -in terms of proper

human

activities among others in bridge control, in

shore-based pilot assistance and in coordination

of the

different traffic operations- using more

know-ledge (1) and improved instruments (2) make it

possible that over the years more, bigger and

deeper draught tankers enter the harbour area

via navigation in a gradually decreased underwater

channel geometry. Again in principle the effect

of all these efforts could be measured in practise

during the progress of the project and documented

in terms of a rate of effectivity in which all

functioning provisions contribute in integrating

form to the safe and expeditious fullfilted harbour

area bound traffic in this intermediate stages.

This information could be an input for the work

in a next project stage among other to eliminate

possible undesired and dangerous effects of

interacting factors.

So also in the post project years a lot of work

had to be done among others in the attemps to

decrease the rate of complexity in the realisation

of the operations.

Finally a more complete inventarisation and

eva-luation of the project research is in a final stage.

And it is only in the context of a more

compre-hensive description of all working factors in their

mutual consistency that the more specific factors

can be isolated and formulated explaining the

reasons why such a gradual decrease in channel

geometry was possible to restrict project costs

as well as possible.

(13)

Question asked by J.C. Baril, Port of Le Havre

Authority.

Question: What are the current and swell conditions

limiting the entry of the VLC's in Europoort? Are

there time schedules depending on the tide time?

Answer given by G. Wiedemann.

Answer: In the final state of the project in

prin-ciple there are no specific limitations for the

execution of VLC-channel-transit operations with

regard to current patterns occuring in the

diffe-rent phases of the tidal motion. Of course pilots

prefer -from a point of view of the amount of work

to do in bridge control in avoiding dangerous

situations- the more favourable ones especially

in bad weather and specific sea and traffic

con-ditions.

A threshold value for limiting swell conditions is

taken into account in the operational planning of

the VLC-transits via the informations of the hydro

meteo expectation system. This value regards the

occurance of swell in the channel area with

spec-tral density values in order of 150 cm2 of wave

energy in the period range exceeding 8 sec.

Data about swell occurance refer to both "expected

swell" as well as to "real time values measured

in the considered area". In time and place the

occurance of swell in the area has a stochastic

character.

By means of this way of working uncertainties in

the execution of the different operational tasks

with regard to "bottomcontactsafety aspects" are

eliminated. As a matter of verification recordings

over the last seven years of the project show:

1. from a point of view of safety:

delay times occured for incoming VLC's varying

from 1 to 12 hours;

no bottomcontacts occured during transits;

2. from an economic point of view delay times

regarded ca. 20 tankers, that is to say < 1% of

the total amount of incoming VLC's carying more

than 0,5.109 tons of oil, ore and grains, the

latter from a social point of view.

As been outlined in section IV of the paper, till

the end of the project realisation in 1977 transit

schedules of the deeper draught tankers are also

bound via the tide time information on tidal phases,

assuring the desired underkeelclearances during

the availability of the relatively higher waterlevels

around high watertop in the actual tidal curve over

the whole channel traject from sea uptill the

spe-cific terminal locations in the Europoort-harbour

area.

Cross section Eurochannel underwater profil

MSL 1800m

Tidal range

formal channel bottom level

1200 m

real isatiori state 1969

realisation state 1971

realisation state 1976

(14)

Discussion on Paper No. 1

Question asked by A. Burgers, Hydronamic,

Netherlands.

Question: The calculation of the drag forces is

carried out by an integration alongside the ship.

(FT=

Fi)

(MT= k2 yFixi).

How do you determine the coefficients for this

calculations?

I think that this method is very complicated and

that the drag can be better determined directly

for the whole ship.

Espicially in shallow water the current pattern

around the ship is such, that the coefficients

alongside the ship will vary very much.

Further-more, I do not understand how these coefficients

could be measured.

Please your comments.

Related to the above is the next question:

You solve the equation for the rotation of the

ship by introducing the calculated moments (by the

rudder, resistance, etc.). I think that this is a

complicated method. It is also possible to solve

the rotation-equation as far as possible, and than

not introducing the moments but the

rotation-velocity when this has became constant, and the

time-constant before reaching this constant

rota-tion velocity (e.g. as defined by Nomoto).

Please your comments.

Answer: 1.the coefficients Cx and k2 introduced

in the expression of the drag forces

1

[Fi = -

S Cx(Vicosxj)2,

FT

= 7

Fi and MT = k2 7 FiCqj

do not vary from a strip of the ship's hull to the

other. The value of C(1.5) corresponds to the

drag coefficient for a flat plate and the value of

k2 (k2=0.52) is deduced from the correct

repro-duction of turning tests (beginning of turn and

steady radius) for the full scale model.

The velocity Vi is the velocity relative to the

wa-ter of the strip i. This velocity is not constant

alongside the ship due to the ship's rotation and

the fact that the flow pattern encountered by the

ship is not uniform. So it can exist large gradients

of cross currents alongside the ship and in this

case we cannot compute the drag force directly

for the whole ship.

2. this method is not complicated and allows to

compute all transient motions.

Question asked by C.L. Crane Jr., Exxon

Inter-national Co.

Question: The presentation method for showing

computed motions of the vessel in the motion

pic-ture would be very helpful to persons making

decisions based on the results. Was the same

method used by the shiphandlers in the course of

making the maneuvers?

Answer: Not presently; the computer gives to the

pilot on a printer the ship's coordinates and

heading and from that the position of the ship is

manually drawn on a millimeter paper reproducing

the harbour layout and the navigational channel

geometry. To day we are improving the

presen-tation method by developing a real time cathodic

rays screen.

Question asked by Ron Gress, US Coast Guard.

Question: You indicate in your paper that the

model can be used to determine the probability of

failure when entering a harbor. Your work until

now, although using an actual pilot in the control

loop,presents the pilot with information far

diffe-rent from that which he would have in an actual

ship. What affect does this have on the probability

of failure? What plans are there in the future with

respect to improvements in this area? If images

are to be presented to the pilot, how are they to

be generated?

Answer: It is true that the information presently

given to the pilot by the mathematical model is far

different from that which he would have in an

actual ship and it is difficult to estimate the

influence of these limitations on the statistical

results. To day we are improving the presentation

method by developing a real time cathodic rays

(15)

Question asked by P.A. Kolkman, Delft Hydraulic

Lab.

Question: 1. Is it right that in the mathematical

description of the forward resistance, the

influ-ence of ship rotation and of Vi is not included?

2. What is the mathematical description of the

helmsman?

Answer: 1. No; in the forward resistance formula

the velocity V represents the component X

along-side the ship of the relative velocity to the water.

So the influence of ship rotation and of Vi are

included in the water forward resistance but only

the longitudinal component is taken into account;

the transverse component is taken into account in

the drag force.

2. There is no description of the helmsman. The

pilot gives direct orders to the propeller and

rudder. These orders (number of propeller

revo-lutions, rudder angle) are introduced at fixed

time intervals (about 80 s to avoid excenively long

experiments); during each time step the pilot's

orders are not changed.

Question asked by Nils H. Norrbin, SSPA,

Gbteborg.

Question: This study contains a number of good

ideas, which should be read with interest. Other

are more doubtful, such as the inclusion of

cross-flow drag forces while linear terms are ignored.

The "curve-fitting" demonstrated in Fig.3

dis-closes a systematic divergence, which would be

likely to spoil the results alltogether, if a larger

change of heading were to be considered.

As a ship model basin man I feel compelled to

advise the authors on the existence of an

inter-nationally recognized nomenclature to be applied

when dealing with problems of ship motions, i.e.

that of ITTC (the International Towing Tank

Con-ference); this should be available from NMI in

London.

Answer: The beginning of your question is rather

a comment; about the question concerning the

figure 3 it is true that there exists a small

diffe-rence between the steady rate of turn between

prototype and mathematical model. But we think

it is better to. Well reproduce the initial variation

of rate of turn than the steady one because during

approach manoeuvres large changings of heading

are not frequent.

About nomenclature I will say that we are not

regular customers of ITTC but sure we shall look

carefully at the mentioned proceedings.

Question asked by H.A. Nuhoff, Dutch Ministry

of Transport, Rijkswaterstaat.

Question: The problem of the out-lay of the

har-bour of the Verdon is a shallow water problem.

You have calibrated your model by full scale tests

with a large tanker. Were those tests done on

shallow water?

Answer: The full scale tests with the 213 000t

"MAGDALA" supertanker have been carried out in

deep and shallow water but the underkeel clearance

has never been less than 30% of the ship's draught;

moreover the accuracy of the measurements is not

sufficient to quantify the effect of shallow water.

In fact in the case of LE VERDON harbour, the

underkeel clearance is very small only at low tide.

So most entrance manoeuvres are carried out

with a clearance more than 15%.

Question asked by L. Wagner Smitt, Danish Ship

Research Laboratory.

Question: In the paper hull forces due to sideship

and yawing are expressed by cross-flow drag

terms only, whereas the usual linear terms

(Yvv, Nrr etc) have been omitted. Nevertheless

a good reproduction of the manoeuvres used for

calibration has been achieved. I would suggest,

though, that the inclusion of linear terms may

significantly improve the mathematical model

with-out introducing undue complications.

Answer: Thank you for your suggestions.

Question asked by R.W. Yeung, MIT, U.S.A.

Question: There are several questions that I

would like to ask.

In the resistance formula given in Fig. 1, what

does the coefficient Cs represent; the residual

resistance?

Would you explain in a more detailed fashion how

the quantity Cx, which is assigned a value of 1.5

in Fig. 1, was arrived at? This value should also

be dependent on the water depth, was this for

one

specific water depth?

The results of the simulation shown in the

movie during the presentation indicated that in

many occassions, the ship is extremely close to

the side bank. In such situations, hydrodynamic

interaction forces due to the bank also existed.

Were these accounted for in the mathematical model?

The authors have chosen to study the effects of

ship motions for the special case of 450 stern

seas.

I would like to hear from the authors the rationale

for making such a choice.

(16)

Answer: 1. the coefficient Cs in the resistance

formula represents the effect on the friction force

of the wake of the ship whose shape differs

sub-stantially from that of a flat plate.

the starting value of Cx (1.5) corresponds to

the mean value of the drag coefficient of a wide

flat plate in deep water; a corrective factor of

0.52 has been added during calibration in the

ex-pression of moments.

the effect of hydrodynamic interaction forces

due to the banks is not taken into account in the

mathematical model. In the movies we have

pre-sented "half-successful" tests to have a more

impressive show. When the entrance manoeuvre

is "successful" the ship must navigate far from

the banks, so the interaction effect remains small.

Discussion on Paper No. 2

Question asked by Nils H Norrbin, S SPA,

Gateborg.

Question: The authors present the application of

a technique, which might be of some value for

identifying critical phases of an harbour approach.

Surely the authors need not to be told that the ship

model ( and in particular the screw and rudder)

are "on the small side". Scale effects may add to

each other, or they may cancel to some extent.

From one of the slides shown I noticed that the

rudder was made to scale using the prototype

streamline profile. To retain normal low-incidence

lift characteristics down below Rnc=5.104 (or say

at model speeds corresponding to any prototype

speed less than 20 (!) knots) it will probably be

better to use a plate type rudder. In such a case

the stall may also be delayed to somewhat larger

helm angles than is otherwise possible; the

CLmax may be 0,3, say, instead of 0,7 for the

streamlined model rudder, which value should

still be compared with 1,1, say, for the prototype.

(Based on "effective" flow velocity)

Answer: Different opposite scale effects can

change the rudder action on the small scale ship

model but the reproduction on the model of the

turning conditions of the real ship has shown that

it was not necessary to distort the shape and the

area of the rudder. We notice your comments on

the way how to increase the lift force of a reduced

scale rudder by using a flat plate instead of the

normal streamline profile.

the paper presents the results of the calculation

of the ship vertical motions for the case of 45°

stern seas.

This case corresponds to the orientation of the

designed Grionde channel respective to dominant

waves but we have also computed the ship motions

for another waves directions.

Question asked by H.A. Nuhoff, Dutch Ministry

of Transport, Rijkswaterstaat.

Question: 1. What criteria are used deciding the

tests are "successes" or "half succes"?

2. Do you have done studies on your statement on

p.6 of your paper that the simulation is to be

con-sidered pessimistic compared with full-scale

trials? It seems to me that it is right the opposite:

in reality the movements of large tankers can not

be seen by the pilots than by the use of instruments.

Answer: 1. The test is "half successful" when the

ship succeeds in entering the harbour but with a

trajectory with a point too close to channel banks

or harbour structures (less than 50 m). The test

is "successful" when the trajectory is good and

when the ship can stop in the turning area.

2. As regards the second part of your question

perhaps we are wrong but perhaps you are also.

In fact it is very difficult to determine if the

scale model conditions of piloting are more or less

difficult than in nature.

(17)

Question asked by G.A. Pickering, WES, U.S.A.

Question: In calibration of the small scale model

was consideration given to reducing the angle of

attack of the rudder to reduce the model ship

response so that a more realistic prototype

response would be simulated?

Answer: The answer is the same than the one

given to N.H. Norrbin.

Question asked by I .A. Svendsen, ISVA,

Copenhagen.

Question: In most harbour places (and in this

as-well) one sees a turning circle for the ships in

question drawn inside the harbour. This

apparent-ly illustrates the area required for part of the

ship manoeuvres and in most cases requires

con-siderable excavation to establish and maintain.

Hence it represents an appreciable proportion of

the expenses of the harbour.

In my opinion this evaluation of the highly

suffis-ticated manoeuvre simulations is too crude to be

accepted when the economical consequences are

Discussion on Paper No. 3

incl. additional contribution by T.F.D.Sewell

Contribution to the Discussion, by T.F.D. Sewell,

Director, Maunsell Consultants Limited.

In the techno-economic study of the Suez Canal,

refered to at the beginning of Dand and Whites

Paper, I had the priviledge and pleasure of being

Project Director for Maunsell Consultants Ltd. In

that position I had good cause to be grateful for

the research work which we commissioned from

the U.K. Hydraulic Research Station and the

National Maritime Institute.

In addition to the studies described in this Paper

research was also directed to the problems of

siltation and w.4v

disturbance in the approaches

to Port Said(1)kZi and the likely changes in the

adjacent beach regime(3) following construction of

the planned new by-pass to the east of Port Said.

A mathematical model(4) was also constructed by

HRS to study the variations in salinity and tidal

currents that will take place when the Suez Canal

is enlarged.

The results of these studies indicated that only a

relatively short rubble mound breakwater, 2 km

long, is needed to protect the eastern side of the

new approach channel, and beach erosion and

accretion can be controlled by means of a groyne

250m long installed to the west of the channel and

similar groynes spaced at 500m intervals to the

east of the new breakwater.

apparently so severe. The more so as a rational

estimate, on the basis of the manoeuvre analysis,

almost invariably would lead to entirely

different-ly shaped manoeuvre areas, even when suitable

reserve manoeuvres are included. Hence one may

ask: is this circular area included as a

conse-quence of traditions or is there a deeper and

rational explanation?

Answer: The turning circle diameter of the new

outer harbour of Dunkirk is 1200 m long. This

manoeuvring area is mainly designed to allow a

300 000t ship entering the harbour at 6 knots to

stop without tugs with the maximum safety. This

area must be also wide because when the

propul-sion machinery runs astern the rudder action is

poor and so the stopping trajectories are very

scaltered.

The presence of a circle on the figures is perhaps

the consequence of traditions but in fact the sizes

of the manoeuvring area are designed as a function

of stopping distances and lateral dispersion of

stopping trajectories.

The tidal current study showed that currents in

the southern part of the Canal will increase by

at least 20% at the end of the present phase of the

development and even more on completion of the

overall plan. This is of particular significance

when considering the safety of navigation and the

problems of stopping VLCC's in emergency. This

latter problem is of great importance in the future

operation of the Suez Canal and I shall be

re-ferring to this in the discussion following Messrs.

Parthiot and Sommet's Paper on the Stopping of

Supertankers in the Canal.

Siltation in Port Said Approach Channels.

HRS Report No. EX 751. 1976

Coastline near Port Said and Port Foaud.

HRS Report No. EX 766. 1977

Wave Disturbance in Northern Approaches.

HRS Report No. EX 771. 1977

The Effect of Deepening and Widening the

Canal on Tidal Currents.

HRS Report No. EX 731. 1976

(18)

In this general connection I should explain that

Sogreah of Grenoble were appointed by the Suez

Canal Authority to do a similar, almost parallel

study to ours and it is interesting to note that in

essentials the findings of both groups were very

similar thus enabling the SCA to proceed with

confidence in continuance of their development

plan.

I should now like to return to Dand and White's

Paper and place this research in the context of

the Study as a whole. The terms of reference for

our assignment were very wide and comprehensive,

requiring a team of engineers, economists,

mathe-maticians, scientists, mariners and dredging

con-tractors.C5) Apart from examining the

consider-able civil engineering aspects, navigation aids,

radar surveillance, pilotage, pollution and

fire-fighting, we were principally required to

deter-mine the optimum development strategy for the

forseable future.

Accordingly we had to study the likely future

growth in world demand for oil and non-oil

pro-ducts, taking account of the differing growth rates

of the principal regions of the world and, against

this background, to forecast the potential traffic

through the Suez Canal. The actual traffic had

then to be forecast and this depends mainly on the

size of the Canal and the charges levied on those

wishing to use it. In addition, the attractiveness

of the Canal varies according to the current state

of the shipping market and vessel costs. The

attractiveness of the Canal route also depends on

the capacity of the Canal to handle the traffic and

the capacity and congestion aspects were a

parti-cular feature of the Maunsell report because it

became clear that unless the Suez Canal Authority

improves the present operational methods, delays

due to congestion will become very large very

soon after the present development scheme comes

into operation. Operational improvements were

put forward and discussed in detail in the Report

but ultimately it will be necessary to increase the

number of by-passes in the Canal to reduce

pro-gressively the restrictive one-way lengths of

Canal, until eventually there are two separate

channels from Port Said to Suez. This Master

Plan was submitted to the SCA and has now been

adopted as official policy.

The phases leading to this ultimate development

were examined in considerable detail with the

aid

of a computer, to test the sensitivity of our

pre-dictions to variations in assumptions regarding

world trade trends, shipping costs and the like.

This sensitivity analysis showed that the best

strategy is for the Canal to be expanded to take

vessels of 53 foot draught and then, as soon as

revenue is coming in from this development,

the

Authority should proceed to 67 or 68 foot draught

vessels, that is, 250,000dwt. tankers fully

loaded. Associated with this expansion would be

the progressive increase in by-passes and the

improvement of operational systems.

So, what is the significance of the research work

done on channel design and described in the Paper?

Firstly, there is the economic significance. In the

first phase of development, if the designed section

were, say, only 5m wider than necessary, this

would result in over $18 million of unnecessary

dredging. Secondly, there is the safety of

navi-gation. Determination of an adequate lane width;

limiting wind conditions for a safe transit; the

optimum intervals between vessels; these factors

all formed part of the comprehensive investigation

into the Suez Canal's future but I would add the

all-important point that research and design can

be as sophisticated as time and money will allow

but all is wasted if it is not matched by good

mana-gement and good seamanship so the emphasis must

be on continuous training and updating in the light

of operational experience.

I should like to conclude by summarising my

re-marks in the form of a few slides.

5. "Factors Involved in Developing the Suez

Canal". PIANC Bulletin Vol. III No. 28

(19)

o 40 35 Lu

2

30 Lu

Z

25 (3 2.-D cc 15

0

U_ 10

a-Source . COOPERS 8 LYBRAND

DISTRIBUTION BY DRAUGHT OF THE EXISTING AND ON ORDER WORLD TANKER FLEET

1. Onorder fleet

ROUTE COSTS 67 46. 53 56' 60' 66 V 01 ROUTE CHOICE -85': 4m DWT FLEET MIX CANAL TRAFFIC (POTENTIAL) (ACTUAL)TRAFFIC (ACTUA CANAL 1,0 120

FIXED CONVOY CYCLE

100 TIME OF 24 HOURS BO VARIABLE START 60 TIME 40

20

30 40 50 60 70 so 90

AVERAGE TOTAL NUMBER SHIPS PER DAY EFFECT OF CONVOY CYCLE TIME

3. Cycle time

V

TRADE FLOWS

15

;SEA DI STA NC ES /fCANALTARIFF

/fLOAN

TERMS

SHIP CANAL TRANSIT WORLD FLEET TRADE CANAL CANAL

COSTS REGULATIONS CHARACTERISTICS FORECASTS CAPACITY EXPANSION_COSTS

2. Sea Route Model

TRAFFIC AND REVENUE FINANCIAL AN FINANCIAL ANALYSIS

fiEl>1"

a.,

(20)

4. Master Plan

16

SUEZ CANAL MASTER PLAN

9. Canal sections compared

EVENTUAL SECOND CHANNEI.

CONSTRUCTED IN STAGES

TO SUIT TRAFFIC GROWTH

CANAL EXPANSION

1869

1939

1959

1980

4

3-

2-14 SHIRSREED 14km/Hp 13 12 10 4 5 6 7

AREA RATIO AT TRANSIT

SOURCE: HRS

ANALYSIS ON NON COHESIVE SEDIMENTS OF

EQUIVALENT DIAMETER 0-25mm

(21)

7. VLCC helm changes

*10111.1116

6. Drawdown

8. V LCC at Toussoum

Proceedings of the Symposium Aspects of Navigability of Constraint Waterways, Including Harbour Entrances, Volume 4, Delft, The Netherlands

Amine

SYMPOSIUM

aspects of Vol .4

navigability of

constraint waterways,

including

harbour entrances

Laboratorium voor

Scheepshydromechanica

Archief

Mekelweg 2, 2628 CD Delft

delft 1978

delft,the netherlands,april 24 -27,1978

lume

--gmceed

nga

delft 1978

-aspects of

navigability of

constraint waterways,

including

harbour entrances

delft ,the netherlands,april 24-27,1978

volume 4

late papers

discussions

final session

-SYMPOSIUM

aspects of

navigability of

constraint waterways,

including

harbour entrances

- Section on Maritime Hydraulics, both of International

Delft Hydraulics Laboratory

Contents

Opening by M. Hug (IAHR)

Dear President, dear colleagues

I feel greatly honoured to be invited to open this

symposium concerning the "aspects of navigability

of constraint waterways, including harbour

en-trances". I assume this honour to be mainly due to

my present quality of president of IAHR but I want

to express the personal pleasure to be with you to

day and to explain the reasons of my particular

sensitivity to the invitation of the organisers: the

Delft Hydraulics Laboratory and the Netherlands

Ship Model Basin. Although my initial education

was civil engineering-orientated, I have later

spent many years in various aspects of hydraulic

machinery. During this very interesting period of

my life I was fascinated by the possibilities

offered at the intersection of two disciplines:

civil engineering and mechanical engineering

specially when considered from a double view

point: research and engineering pratice. I think

that this symposium offers a good example of such

possibilities. The intersection between two

disci-plines, here civil engineering and naval

architec-ture is expressed between the two organisers and

the double view point is emphasized by the fact

that this symposium has been initiated through a

joint proposal of the Committee on Fundamentals

and the Committee of Maritime Hydraulics of IAHR.

The Committee on Fundamentals fosters the basic

research approach and the Committee of Maritime

hydraulics bridges the gap between applied

re-search and engineering practice. In that respect

a special mention has to be made of the

cosponsor-ship of PIANC. I appreciate very much the

inte-rest shown by PIANC in this symposium and thank

the president Willems for being also with us to day.

When one wants to make progress in a given field,

three main means of action can be used

simultane-ously or one by one. These are:

observation of natural full scale conditions

physical modelling

mathematical modelling.

Both physical and mathematical models are