The relation between motions of moored ships due to wake wash of passings vessls and the hindrance thereof

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Date Author Address

January 2009

Luth, H., 3. Bos, J.A. Keuning and I. _{van der Hout} Deift University of Technology

Ship Hydromechanics Laboratory

Mekelweg 2, 2628 CD Deift

TU Deift

Delftluniversityof Technology

The reIation between motions of moored ships

due to wake wash of passing vessels and the

hindrance thereof

by

H. Luth, J. Bos, '.A. Keuning & I. van der Hout

Report No. 1630-P ₂₀₀₉

Proceedings of International Conference on Innovation

in high speed marine vessels, 28-29 January _2009, Fremantle, Australia, The Royal Institution of Naval

Architects, RINA, ISBN: 987-1-095040-54-4

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Numerical Simulation Of Ships In High Seas Using A Coupled SPH FE

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P Groenenboom, ESI Group, THE NETHERLANDS

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A Practical Technique For Assessing The Likelihood Of Surf-Riding Of A High-

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Speed Craft In Following And Following Quartering Seas

A Maid & N Umeda, Osaka University, JAPAN

MRenilson, Australian Maritime College, AUSTRALIA

Experiences From Design, Construction And Operation Of CFRP Sandwich

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Ships And Boats

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Developments In Fire Safety For FRP Composite Vessels

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Gyro-Stabilised High Speed Trimarans

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T Perez, University of Newcastle, AUSTRALIA

On The Resonance-Motion-Free Swath As An Ocean-Going Fast Ship

31

M Yoshida, Kyushu University, JAPAN

Station Keeping Of HighSpeed Ferries

39 D Sadovnikov, AMOG Consulting, AUSTRALIA

The Relation Between Motions Of Moored Ships Due To Wake Wash Of Passing

49 Vessels And The Hindrance Thereof

JA Keuning, DeW University Of Technology, THE NETHERLANDS

J Bas, Netherlands Organization For Applied Scient/ic Research,

THE NETHERLANDS

C Boots, Province Of Zuid-Holland, THE NETHERLANDS,

HR Luth, Damen Shipyards Gorinchem, THE NETHERLANDS

The Identification And Protection Of Intellectual Property For The High Speed

57 Craft Industry

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The Reconfigurable Hull Form Concept For High Speed Operations

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A Gazal & M Renilson, Australian Maritime College, AUSTRALIA

S Cannon, Defence, Science And Technology Organisation, AUSTRALIA

'Greener' High Speed Vessels - Options For The Future

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THou, Del Norske Veritas, Australia Branch

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Cogeneration Systems Aboard High-Speed Ferries

JPeterseim, ERK Eckrohrkessel Gmbi, AUSTRALJA

UK

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Giobal And Slam Load Model Testing To Support Developing HS1'W Operations

In Severe Sea Conditions

MDavis, WAmin, JLavroff& D Holloway,, University Of Tasmania, AUSTRALIA

G Thomas & S Matsubara, Australian Maritime College, AUSTRALIA

Slamming Quasi-Static Analysis Of An Incat 98 M HighSpeed Wave Piercing

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Catamaran

WAmin, MDavis & D Holloway, University Of Tasmania, AUSTRALIA

G Thomas, Australian Maritime College, AUSTRALIA

The Hydro-Elastic Behaviour Of Flexible Panels With Inhomogeneous Material

113

Properties And Added Restraints

MPitman & A Lucey, Curtin University, AUSTRALIA

Hull Structure Monitoring For The Armidale Class Patrol Boat

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C Gardiner, P Vincent & A Wilson, Defence Science And Technology Organisation,

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D Elleiy & NA Armstrong, Austal Ships, AUSTRALIA

Presentation: 50 Years Of Hovercraft Development

129

B Russell, The Hovercrafl Society, UK

Authors' Contact Details

136

* Paper not available at time of print

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International Conference on Innovation in High Speed Marine Vessels, Fremantle, Australia

THE RELATION BETWEEN MOTIONS OF MOORED SHIPS DUE TO WAKE WASH OF

PASSING VESSELS AND THE

D RANCE THEREOF

H Luth, Damen Shipyards Gorinchem, the Netherlands

J Bos, Netherlands Organisation for Applied Scientific Research, TNO Human Factors, the Netherlands J Keuning, 'Deift University of Technology, the Netherlands

I van der Hout, Maritime Research Institute Netherlands, the Netherlands SUMMARY

After the introduction of Fast Ferry public transport in the Netherlands a number of complaints about wake wash

induced hindrance onboard moored vessels appeared. It was already possible to calculate the wake wash characteristics

of fast sailing vessels, the progress of these waves in a waterway and their effect on moored vessels. This paper

describes the full scale tests carried out to develop the missing relation between the wash induced motions of a moored vessel and the hindrance thereof. Many different combinations of moored ships, passing ships and shore configurations have been realised. An expert panel scored the hindrance due to the motions of the moored vessel. A guideline for maximum ship motions is developed from the results. With this guideline, it can be determined prior to the introduction

of a new innovative vessel with reasonable accuracy if its wake wash will remain within acceptable limits.

1. INTRODUCTION

A number of rivers in the Netherlands are intensively

used by inland vessels for cargo transportation across the

country and towards Germany. A rich variety of

maritime activities can be found along the borders of these rivers, such as loading and unloading of cargo vessels, ship repair and maintenance and recreational harbours. Immediately after the introduction of Fast

Ferry public transport in the Netherlands in the nineties

of the past century, a number of complaints appeared

about Fast Ferry wake wash induced hindrance to

moored inland cargo ships. These have been solved by improving mooring methods and reducing the speed of the Fast Ferries when passing vulnerable areas. To date,

these speed restrictions are still in place and have a noticeable negative influence on the sailing time on

various routes. Hindrance of wash in the form of shore erosion as found in many other locations worldwide is

not a big issue in the Netherlands due to appropriate

sheet piling of most busy trajectories.

Requests for introducing new vessels on the inland waterway system come from two directions. First, a

reduction of wash hindrance from vessels on the present

routes is desired. Second, there is

a market for

transportation at higher speeds on new and existing

routes. New vessels are allowed on the rivers only when

they do not cause hindrance to other vessels. At the moment this can be demonstrated only by full scale

trials, as the ability to predict

the hindrance by

calculations or simulations does not exist. As figure 1 shows, the wash produced by a vessel, the progress of

wash waves in a waterway and the effect of the wash on

moored vessels can be predicted with existing design

tools. The missing link

is the relation between the

motions of a moored vessel and the perceived hindrance on its onboard activities.

This situation imposes difficulties for the introduction of new fast ferry designs. Both the ship owner and the ship

builder cannot afford to

take the responsibility of

financing a new fast ferry building if it is not certain that the vessel can sail on the intended route. Furthermore, in

the present situation it is difficult for the authority to

judge the correctness of complaints on hindrance.

To change the present situation, the Province of South Holland (the Netherlands) initiated a study to investigate the relation between wash induced ship motions and the hindrance thereof. The full set of results is presented in [I] and [2].

Safety + performance "down time" =

Knowledge is available Goal of the study

Hindrance versus motion Knowledge is not available

of moored vessel

Figure 1: Wave hindrance components and goal of study

2. PREVIOUS RESEARCH RESULTS

Before commencement of the full scale tests, two desk

studies have been carried out:

a survey of past studies carried out into the effect of fast vessels on other ships in the Netherlands inland

waterways;

a survey of filed complaints and police reports witha

number of interviews with involved persons.

The survey of past studies revealed that most of the

reports on waterborne fast passenger transport iscussed

(7)

concerning fast vessels.

In most of these

studies, hindrance is mentioned only occasionally.

The approach to avoid hindrance of fast vessels up to

now has been that a fast vessel should not produce higher

waves than already present on the inland waterways due to wind and other vessels. Although it was argued that

the period of the wash wave is of importance as well, this

approach has been quantified into a maximum wave

height of 0.30 m. With the addition of a measurement distance of 35m from the vessel, this rule has been used

since in the Netherlands. It is argued also that fast vessels

should not cause more hindrance than already present on the inland waterways due to wind and other vessels. It was recognised that, since it is difficult to develop an

all-covering rule, fast vessels should take their responsibility

in avoiding complaints of other inland waterway users. If they do not do this, the authority may make additional

reservations.

It was also reported that hindrance is difficult to quantify,

and that it is a subjective experience also influenced by other effects than the motions only. Jerky ship motions

and excessive

noise due

to (sub-optimal) mooring arrangements determine to high extent the level of the

hindrance.

Filed complaints and police reports have been

investigated. In general, the police only work on cases where damage has occurred. It is apparent that after the

introduction of Fast Feny passenger transport in the

Netherlands, hindrance occurred. However, after

improving mooring methods, sailing schedules and a period to get used to Fast Ferry transport, today the

hindrance due to Fast Ferries seems to be not more than that of other vessels. Another result of this study is that other vessels, such as fishing vessels, police and patrol

boats, speed boats and jet skies also cause significant

hindrance. Governmental bodies seem to see more risk in

the visibility, and hence safety, of high speed transport than in hindrance due to wake wash.

Based on the literature research and interviews, the

following has yet been concluded:

hindrance due to wake wash is an issue for existing fast ferry lines. The absence of a criterion is an issue

for starting up new fast ferry lines;

most of the complaints are related to commercial

activities situated on the main transportation routes,

therefore, yachting and house boats will not be

considered in this study;

a recommendation exists to limit wake wash to 30

cm in

height, however this is

not a general

applicable criterion;

essential information is available on the

hydrodynamic aspects of wake wash and their effect on moored vessels;

a workable definition of hindrance due to wake wash

is not available; Figure 2: Aerial pictures of test locations with location of moored vessel indicated (from Google Earth)

2OO9: The Royal Institution of Naval Architects

A

City Type of mooring Moored vessel Number

of runs Bolnes Open jetty along

channel 28.0 x 8.2 m Bunkership 23 Putters-hoek

Quay along channel and in short perpendicular harbour 43.5 x 8.0 m cargo vessel 17+15

Velsen Open jetty along channel 43.5 x 8.0 m inland cargo vessel 27 Rotter-dam Semi-open jetty along channel 67.0 x 7.2 m inland cargo vessel 25 the relationship between motions of a moored vessel

and the hindrance to activities onboard is not known;

there is no objective wake wash hindrance criterion

available for all ship types and all circumstances.

In the present study e) and f) have been investigated and

a recommendation on g) has been made.

3. TEST SET-UP

The goal for the test set-up has been to realise as many different combinations of moored ships, passing ships and shore configurations as possible, within the budget restraints of a project incited by the province of South

Holland, the Netherlands. The target of the test set-up has

been to have a wide variety of ships passing by a couple

of representative moored vessels in a controlled way,

while a panel of experts would judge the hindrance of the

motions, of the moored vessel.

3.1 LOCATIONS

Tests have been carried out at 4 locations

in the

Netherlands, see Table I and Figure 2. These include two

open jetty moorings in a channel, a semi-open jetty

mooring partly protected by moored barges, a quay along

a channel and a quay in a short perpendicular side

harbour.

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3.2 SHIPS

To get an as wide as possible moored vessel motion

range, a number of moored platforms has been used and the tension on the mooring ropes of the vessels has been

varied during the tests. An overview of the moored vessels is given in Table 1. The size of the vessels is

typical for smaller inland vessels in the Netherlands.

On all locations, as many as possible passing vessels

have been used to generate wash waves. These included small water taxis, fast patrol boats, catamaran type fast ferries, hydrofoil type fast ferries, tugs and inland cargo

vessels, see Figure 3. Tests have been carried out at a

variety of ships speeds, passing distances, water levels and current directions. The passing ships have been used merely as moored vessel motion generators. Although of scientific value, the waves of these vessels have not been

measured. In this project the only goal has been to

quantify the relation between the motions of the moored vessel and the hindrance thereof.

Figure 3:

Selection of vessels used

in study for

generation of wash waves

3.3 PANEL

An expert panel consisting of persons with experience in

the maritime sector has been selected to judge the

motions of the moored vessel. Panel members were male persons between 27 and 71 years old and were delegated

by the most important interest groups involved, both authorities and waterway users. Some were captains,

some former captains and some held shore based

positions. Most of the panel members have been involved

in or have experienced wash wave induced hindrance

onboard moored vessels.

A panel of 9 to 11 persons has been onboard the moored vessel during the tests. As not all panel members were

available for all tests, in total 19 persons participated.

To avoid any prejudice against the passing vessel, panel members could not see or hear the passing vessels, see

Figure 4. Panel members were seated with their backs

towards the sailing route and sight was blocked by high

screens around the panel seating area. Headsets with

microphones were worn to block engine noise of passing

vessels and to communicate with the test coordinator.

Panel members were asked not to communicate with

each other during or between test runs about their task.

Panel members were informed that cross-check

measurements could be carried out without a passing

vessel.

The test procedure was as given in the table 2.

Table 2: Test procedure

LAJ!

_TT

-'

LL]

Figure 4. Impression of expert panels at work

3.4 MOTION SENSORS

Ship motions can be quantified by a

variety of

parameters. Accelerations have been measured because

accelerations result in a force on an object and can be

"felt" by a person. Accelerations and angular velocities have been measured in three directions x, y and z in the

neighbourhood of the expert panel to determine the

accelerations and motions at issue.

The measured acceleration data showed some noise and

peaks. Filtering the signals resulted in a much more

consistent relationship between accelerations and

hindrance scores (see below). All acceleration signals

have accordingly been filtered using a 1 Hz low-pass

filter (3 order Butterworth). The effect of this filtering is

that large scale motion amplitudes are emphasized more

than small scale motion amplitudes.

The accelerations in the three directions have been

combined to one amplitude using vectorial addition: Av

= SQRT( Ax2 + Ay2 + Az2). The maximum of this

amplitude has been determined over the relevant time

interval and related to the measured hindrance.

Phase Action

Start test Panel members mount headsets Ship is passing Panel members use PDA to score if

and what level of hindrance could occur

Ship has passed

After sign of test-leader, panel member dismount headset and fill-out scorecards

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Both the applied low-pass filtering and the summation of individual accelerations to one combined amplitude are

in line with the ISO 263 1-1 norm, in which the effects of

motions on humans are described.

The displacement of a moored vessel

can cause hindrance as well. For instance, excessive gangway motions can make it impossible for people to board a vessel and unexpected ship motions during a crane

operation can cause damage to the lifted object. For this reason, the displacements of the vessel in the horizontal plane (surge and sway) have been measured with wire

sensors, see Figure 5.

- ,...

.p

Figure 5. MARIN's Marine Quality Kit used to measure

accelerations and rotations (left) and wire sensors for

measurement of displacements (right).

3.5 HINDRANCE

A definition of hindrance has been formulated. The

starting point is that hindrance is the answer to a given question. The question determines what hindrance is, and the person that answers the question determines the level of hindrance. The question that was posed is: Hindrance

to onboard activities can be caused by ship motions

induced by (amongst other things) wash waves ofpassing

vessels. Which of the qual/Ications given in the table

below apply during the ship motions?

Table 3. Hin

The panel members scored the hindrance during and after the tests. During the tests, panel members continuously scored the hindrance level as indicated in Table 3 on a personal digital assistant (PDA). Every panel member

used his own PDA, programmed with buttons that

indicated the second column of the table above. All

PDA's were wirelessly connected to the data measuring unit that simultaneously captured the motion signals. The

PDA based hindrance score is called

the global

hindrance, because no relationship is made between

hindrance and a specific onboard activity.

After each tests,

a questionnaire was deployed to

determine the level of hindrance for twelve specific on-board activities: painting, engine room activities, work on shore facilities, boarding and un-boarding, hoisting activities, computer work, manual lifting and carrying of goods, keeping balance, other handwork, mooring and loading and unloading of cargo on decks and in holds. Every activity was scOred on the same 1 to 5 scale. This hindrance per activity is called the spec/lc hindrance. Panel members have been instructed to assure that their worst global hindrance score equalled the worst specific

hindrance score.

S

I tt7M

Figure 6. PDA with 5 preprogrammed hindrance level

buttons (left) and a headset for communication (right).

2OO9: The Royal Institution of Naval Architects

Hindrance

Level

Hindrance

qualification

Work Materials

No hindrance Can continue Do not shift 2 Some Hindrance Can continue, but one should be prepared Do not shift 3 Hindrance Should be stopped for some seconds Do not shift 4 High Hindrance Should be stopped for a longer time Are shifted 5 Unacceptable hindrance -Can not be continued (directly) after an incident Are (most likely) damaged

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4. RESULTS AND DISCUSSION

As was expected, not all panel members have been

scoring the same hindrance levels for specific test-runs. The average hindrance score of all tests for a single panel member ranged between 1.7 and 3.5. The variation of all:

tests appeared to be about the same for all panel

members, with a standard deviation of 1.2 +1- 0.3. Yet, there were test runs with unanimous zero and unanimous

maximum scores. It has been concluded that trends in

individual scores are so similar, that an average

hindrance score over all panel members provides a good representation of the expected hindrance.

'C_.9

2

0.5 I 1.5

o0,

Figure 7. Average hindrance as function of displacement (upper row) and accelerations (lower row) and locations (colour of marker)

Figure 7 presents

all measured data. Note that no

displacement measurements have been performed at the

locations Bolnes and Velsen, and that the

vertical

displacement could not be reconstructed accurately at Bolnes. The measured x- and y-displacement of the different locations do not match well with the average

hindrance score. The difference in the mooring layouts could have caused this. The vertical displacements of all

locations do show a consistent relationship with the

hindrance score and has been used for further analysis. The measured accelerations in all directions also show a consistent relationship with the hindrance. Because there

is no reason to assume that hindrance is caused by the

acceleration in one direction more than that in another

direëtion, the overall combined acceleration has been

used for further analysis. The relation between the

vertical

displacement and the

overall accelerations

showed to be too scattered to use only one of the two in the furtheranalysis.

2OO9: The Royal Institution ofNavalArchitects 53

2' E

Eu

E

>0

<O) 0 'I 40 40 it)

0-fl

0 0.5 1 1.5 z (m)

Figure 8. Examples of histograms (bars) and fitted

lognormal distributions (shaded) for hindrance scores 4

(upper) and 5 (lower) as function of vertical displacement.

For the generation of a criterion, it is of importance to know the distribution of the hindrance scores over the

panel members. A log-normal distribution showed a

good representation of this variance; see Figure 8 for an

example.

The next step was to construct an 'average" function

through all measured data; see Figure 9. The following

function has been chosen: h = 5 - 4 e

-b (u-u0)

This

function scores between 1 and 5, incorporates the initial

relation between hindrance and displacement or

acceleration with the steepness parameter b and includes a lower motion limit below which no hindrance is found

with the parameter uij. Furthermore, this function

represents the saturation of hindrance that occurs at

larger motions oraccelerations.

Bolnes Phoek = Velsen R'dam - = fit 0.2 0.4 0.6 0.6 I 1.2 1.4 1 6

Figure 9. Average maximum hindrance score as function of total acceleration and location (colour of marker) and theapplied average fit (bold continuous line)

With the now available "average" relationship between displacement, acceleration and hindrance a maximum allowable limit can be chosen, for instance a hindrance level below 3 ("no hindrance") what implies that work

may still be interrupted

for some seconds.

This

corresponds with a vertical displacement of about 0.30 m and a total acceleration of about O4 mis2. Motions and accelerations above these values are then regarded as not

acceptable. However, it can be argued that with the

0.5 n (n,)

1.0

0.5 1 1.5

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observed log-normal distribution in the hindrance scores,

still 50% of the measured motions are above this

criterion. Another approach could be to state that not

more than 10% of the measured motions should be above

the maximum level. When this

is applied to the

hindrance level of 3, only very small motions and low

accelerations are acceptable (around 10 cm and 0,1 m/s2).

When, however, this approach is applied to a hindrance

level 4 ("high hindrance") the results coincide

surprisingly well with the above presented average

values of a hindrance level below 3.

In the Netherlands, the fast ferry operator "Waterbus by" has implemented speed reduction and minimum passing

distance procedures to avoid hindrance on the most

vulnerable locations along the route between Dordrecht and Rotterdam. All tests performed with the vessels from Waterbus have been analysed separately in addition. This separate analysis showed that all tests with ship speed

and passing distance according to existing procedures giving no hindrance were also within both the "new" amplitude and acceleration criteria. This implies that

when "hindrance level below 3" is adopted as the

criterion, this matches well with the present situation in

the Netherlands.

Finally, the specific hindrance scores have been analysed for the various activities. This analysis showed that the

activities can be grouped in two main categories: the

critical "(un-)loading activities" (including the most

stringent activities crane hoisting and (un-)boarding) and the least critical activity "manual work" (including the least stringent activity computer work). The difference between the two groups is a factor 1.5, see figure 10. As

the maximum values of the specific hindrance scores

correlate well with the global hindrance, the threshold

value for "manual work" can be chosen as 1.5 that of

"(un-) loading".

Handwork

Figure 10. Examples of specific hindrance scores of (an-)

loading activities (left) and handwork (right) versus

vertical acceleration.

Based on the above sections,

the following wash

hindrance guideline is recommended to be used for manual work. To avoid excessive hindrance of wash

waves, the motions of moored vessels should be

restricted to:

a vertical displacement of 0.45 m; and a total acceleration of 0.6 rn/s2.

For activities related to loading and unloading (for

instance hoisting by crane and boarding and unboardmg

a vessel) it is recommended to restrict the motions to:

a vertical displacement of 0.30 m; and a total acceleration of 0.4 m/s2.

This guideline is developed only for activities onboard

commercial vessels in major waterways in the

Netherlands and is not applicable to recreation and

houseboats. Hindrance is defined as the situation where

work should be stopped for some or more seconds.

Materials do not shift yet.

It should be noted that:

despite the above mentioned guideline, a certain spreading in the perception of hindrance always

exists;

horizontal displacements and accelerations can be

reduced by increasing the tension on mooring lines;

acceleration can be reduced with proper (pneumatic)

fenders;

the use of spud-poles or other special mooring

arrangements can be used to restrict motions of

moored vessels;

this guideline should not be used too rigidly.

the guideline is context dependent. Due to

differences in infrastructure and culture, different

limiting values may be applicable in other countries.

5. APPLICATION OF GUIDELINE

The developed guideline can be used prior to

the

occurrence of hindrance, for instance for the evaluation of existing and new public fast ferry services or for the development of new ships types. It can also be used after the occurrence of hindrance, for instance to judge a filed

complaint by the governmental officers.

The scheme for using

the guideline prior to the

occurrence of hindrance, or actually to prevent the

occurrence of hindrance, is as follows. First, a list of

locations where hindrance could occur should be drawn up. For each location, the passing distance, sailing speed, water depth, sort and location of onboard activities and other relevant parameters should be gathered. Onboard

activities should be classified in "handwork" and

"(un-)loading activities" for evaluation against the proper

criteria. For each condition, the displacements and

accelerations should be determined by calculations,

model tests or full scale tests. Finally, the motions and acceleration should be evaluated against the guideline. When the proposed values are not exceeded, it is likely

that hindrance will remain within acceptable levels. When the values are exceeded, measures should be evaluated to reduce the moored vessel motions and

accelerations, for instance improving the mooring system

or changing the sailing schedule.

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International Conference on Innovation in High Speed MarineVessels, Fremantle, Australia

Using the guideline after the

filing of a hindrance

complaint is not straightforward, as motions and

accelerations of the vessel where hindrance occurred,_are

not known. A theoretical analysis of the ship motions could assist in this case When hindrance occurs more

often at the same location, it could be useful to measure

motions and accelerations at the moored vessel to

evaluate the correctness of the complaint, to identify the cause of the hindrance or to improve the mooring system

of the vessel. When a specific ship type is associated

with the generation of the hindrance inducing wash, full

scale tests with this type could be used to develop

hindrance avoiding sailing strategies.

6. CONCLUSIONS

Because a good correlation has been found between

hin4rance and displacements and accelerations, it seems to be possible to define a guideline to avoid hindrance

due to wash. Intuitively, a limit defined as "stopping

work for some seconds" seems appropnate. By definition this is "hindrance", is in rank between "some hindrance"

and "high

hindrance". When the

limit

"no high

hindrance" is chosen and the observed distribution in

scores is taken in to account, the same critical motion and

acceleration levels are found for "no hindrance". The adopted limits correlate Well with the implemented

hindrance avoiding measures that are presently used in

fast ferry operations the Netherlands. The rounded limited values suggested by this study are 0.3 m for

vertical displacement and 0.4 mIs2 for the overall filtered acceleration. This criterion implies that hindrance can not

be avoided completely. A certain distribution in the

perception of hindrance is always present and excluding hindrance in for instance 90% of all cases would result in unpractical low limiting values.

When specific hindrance is analysed, two categories can be defined: the critical category "(un-)loading activities" (including the most stringent activities crane hoisting and

(un-)boarding) and the least critical category "manual work" (including the least stringent activity computer

work). The difference between the two groups is a factor 1.5. As "(un-)loading" activities score in the same range of the global hindrance as "manual work", the threshold

value for "manual work" can be chosen as 0.45 m and

0.6 m/s2.

It should be noted that the results of this study are a

random indicatiOn. Different investigations mto the

hindrance of fast ferries have showed that some sort of

"getting used" to the motions is found over time.

Therefore, it could be possible that the suggested criteria should be adjusted in the future. Furthermore, this study has delivered an enormous amount of detailed data that has not been analysed in-depth. A more detailed analysis of the results in future could also result in adjustment of the proposed values. For-now, it yet seems that with the

suggested values a new and more reliable criterion to

avoid hindrance is posed. Although it could be difficult to use the criterion for the judgment of actual occurrence

of hindrance by governmental officers, it can be used

well to judge predicted vessel motions in the design stage

of a new vessel and for tender procedures for new fast

ferry lines.

7. ACKNOWLEDGEMENTS

This study was made possible by a financial contribution

of the Province of South Holland, Province of North

Holland and the Ministry of Transport, Ptthlic Works and Water Management of the Netherlands. Making available

ships, material

and much personal

effort

of the

employees of the many other parties involved in the

study was of invaluable help.

8. REFERENCES

BOS, J.E., VAN DER HOUT5 I.E. and KEUNING,

J.A., 'Golfhinder: een relatie tussen bewegingeng en

hinder op afgemeerde schepen', TNO report TNO-DV

2007 C461, December 2007.

BOS, i.E., LUTH, H.R., and KEUNING, J.A.,

'Gebruikershandleiding toepassing golthindernorm',

TNO report TNO-DV 2008 Cl 74, April 2007.

9. AUTHORS BIOGRAPHY

Robert Luth holds an MSc in Ship Hydromechanics

from the DeIft University of Technology. He worked for

12 years in the field of motions of moored and free

sailing vessels. Since 3 years he is working at the Damen

Fast Ferry department as a Fast Ferry designer.

Jelte Bos holds an MSc in physics, and a PhD in

medicine Since 15 years now he is working on effects of motions on humans, with a focus on motion and attitude

perception and motion sicknçss.

Lex Keuning graduated in 1977 on the Delfi University

of Technology in Ship Hydromechanics. In 1994 he obtained his Doctors title at the same University. At

present he is Associate Professor in Ship hydromechanics

at the Department of Maritime Technology at the DeIft

University of Technology.

Ivo van der Hout holds an MSc in Ship Hydromechanics from the Deift University

of

Technology. Since 4 years he is working at the MARIN