Ing. W. Beukelman
Papers. on
Shiphydrornechanics
VôI.'V
CONTENTS
Reports of:
Deift University of Technology,
Shiphydromechanics Laboratory,
Mékelweg 2, 2628 CD Deif t, the Netherlands.
by: W. Beukelman.
Volume I
Bepaling van het verband tussen golfhoogte, periode en
pompstand van de golf opwekker..
W. Beukelman
April 1960,. Rapport No. 65.
Voortstuwing in regelmatige. en. onregelniatige langsscheepse.
goiven.
J. Gerritsma, J.J. van den Bosch en W. Beukeirnan. Juli 196.1, Rapport No. 17-P.
iJking van golfopwekker nieuwe verlengde tank. W. BeukeIrnan.
Augustus 1961, Rapport No. 78.
Excitatieproef met zevendelig model flOo 41. W.. Beukeitnan.
December 1962, Rapport No. 107.
Over de bepaling van de demping van iangscheepse bewegingen. Yu.A. Necwetajef. Vertaling: W. Beukeiman.
Februari 1963, Rapport No. 99.
Distribution öf dantping and addes mass along the length of a shipmodel.
J. Gerritsma and W. Beukelman. February 1963, Report No. 21-P.
The influence of
a bulbous bow on
the motions and the
propulsion in longitudinal waves. J. Gerritsma and W. Beukeirnan..
April 1963, Report No.. 20-P.
Een systeein van vergelijkingen voor scheepsbewegingen., die rekening houden met de koppeling tussen de domp-, verzet- en
rolbewegingen.
L.i. Pletneva-Machabeli.. Vertaling: W. Beukelman.
Oktober 1963, Rapport No. 108.
De analyse van de zig-zagproef volgens Nomoto..
W. Beukelman.
Oktober 1963, Rapport No. 10.9.
Over dè
opwekkende krachten die op het schip werken
inregelmatige--go1ven.
B.E. Tosjef_enW.A.Tjoetskewi.ta._ver.talig:w._Beukelman.
Volume I (continued)
The distribution of the hydrodyna.mic forces on a heaving and pitching shìpmodel in stIll water.
J. Gerritsrna and W. Beukelinan. June 1964, Report No. 22-P.
Comparison of calculated and measured heaving and pitching
mötions of a series 60, CB = .70, ship model in regular
longitudinal waves.
J. Gerritsma and W. Beukelxnan. October 1966, Report No. 139.
Bewegingen van een schip in goiven
(md.
dwarskracht enbuigend moment).
Beschrijving van prograimna I-143 3/Bertens -BeukeÏman.
W. Beukeixnan.
Januari 1961, Rapport No. 168-M.
Analysis of the modified strip theory for the cälculation of ship motions and wave bending moments.
J. Gerritsma and W. Beukelman.
June 1967, Report No. 177.
Berekei'ing van de bewegingen, dwarskrachten: . en..: buigende momenten van. een schip. in onregelmatige. golven met de:
prograinma's JS-3509. en JS-4282.
W. Beukelman.
Juni 1968, Rapport No. 206-M.
Computed. results, of ship. motions: of .a fast. f ruitcarrier...
W.. Beukelman.... .
November. 1968:,. Report No. .223-M...
Weerstandsmeting van twee f inn-jolien. W. Beukelman.
Juni 1969, Rapport No. 242-M.
Pitch and heave characteristics of a destroyer.
W. Beukeiman.
August 1970, Report No. 257-P.
Stability of beamtrawlers in following seas. W. Beukelman and A. Versluis.
January 1971, Report No. 295.
Resistance increase of a fast cargo ship in regular waves.
J. Gerritsma and W. Beukelnian.
June 1971, Report No. 313-P.
Hydródynamic forces on a surface piercing flat plate. J.B. van den Bnlg, W. Beukelman and G.J. Prins.
August 1971, Report No. 325.
Volume II (continued)
Analysis of the resistance increase in waves of a fast cargo ship.
J. Gerritsma and W. Beukeiman. September 1972, Report No. 334-P.
Description of a program to ca1ciate the behaviour of a ship
in a seaway (named: Trial).
W. Beukelman and E..F. Bijisma.
August 1973, Report No. 383.
Full scale measurements and predicted seakeeping performance of the containership "Atlantic Crown".
W. Beukelman and M. Buitenhek. November 1974, Report Ño. 388-P
Drag and sideforce measurements with à 1/6 scale model of the yacht !'Antjope.!t
W. Beukelman and A. Huijser. March 1974, Report No. 395.
The effects of beam on the hydr,odynamic characteristics of
ship hulls.
J. Gerritsma, W. Beukeiman and C.C. Giansdorp. June 1974, Report No. 403-P.
Zeiìprestaties van de ocean cruiser 16. W. Beukelman.
Juni 1974, Rapport No 404.
Comparison cf seakeeping prediction methods for diffèrent
ships.
W. Beukeìman.
June. 1975, Report No.. 420..
The ïnfluence of fin keel sweep-back on, the performance of sailing, yachts.
W. Beukelman and J.A. Keuning. November 1975, Réport No. 445-P
Variation of parameters determining seakeeping. W. Beukeiman and A. Huijser.
December 1976, Report Ño. 443-P.
Handleiding voor het gebruik van het scheepàbeweg±ngen progra.na voor 6 graden van vrijheid.
W. 'Beukelman..
April 1977, Rapport No. 449-M.
Bottom inpact préssures due to forced oscillation. W.. Beukelman,.
February 1979, Report No. 4,79-P.
Hydrodynamic coefficients of rectangular barges in shallow
water. -
--J.A. Keuning and W. Beukeiman.
Volume III
Seakeeping trials ith HNLMS "Tydeman1t.
J. Gerritsma and W. Beukeiman.
March 1980, Report No. 494.
Added resistance and vertical .hydrodynamic coefficients of
oscillating cylinders at speed. W. Beukelman.
September 1980, Report No. 510..
Forced oscillation experiments with a segmented model in
shallow water.
J. Gerritsma and W. Beukeirnan. November 1980, Report No. 513-P.
Thé distribution of hydrodynamic mass and damping
of an
oscillating shipf arm in shallow water.. W. Beukelman and J. Gerritsma.
March 1982, Report No. 546-P.
De verdeling van de hydrodynamische. massa en demping over een in ondiep water oscilierend ;scheepsmodel.
W. Beukelman en J. Gerritsma.
Maart1982, Rapport No. 546-A.
The 1ongitudnal. distribution of low frequency hydrodynainic derivatives for lateral motions in shallow water.
W. Beukeiman and J. Gerritsma. September 1983, Report No. 562-A.
Calculation methods of hydrodynamic coefficients of ships in
shallow water.
W. Beukelman, R.H.M. Huij emane and P.J. Keuning. November 1983, Report No.. 571-P.
Vertical motions and added . resistance of a rectangular and
triangular cylinder in waves. W. Beukelman.
July 1983, Report No.. 594.
On sway damping .and added mass. in shallow water. W. Beukelman.
September 1984, Report No.. 603-P.
Seakeeping calculations for high speed round bilge
displace-ment ships sub-series 1. W. Beukeiman.
April 1984, Report No. 616-O.
Trial, a computerprogram to calculate the behaviour of a ship
in regular and irregülar longitudinal waves. J.M.J. Journée and W. Beukelman.
Value IV
The high-speed displacement ship systematic series hull
forms - seakeeping characteristics. J..J. Blok and W. Beukelman..
November 1984,, Report No. 675 - P.
Semi -pianerende vaaEtuigen in zeegang, pred'ictie van inzetbaarheid.
W. Beukelman.
Maart 1985, Rapport No. 658-0.
Ontwerp serie modellen ter bepaling van de jnzetbaarheid op
de Noordzee.
W. Beukelman.
April. 1985, Rapport No. 6.64-0.
Snelle deplacementsschepen in zeegang. W. Beukelman.
April 1985, Rapport No. 754-P.
Comparison of seakeeping cal,culátion methods f or.model 9 of the high speed displacement ship series.
W. Beukelman.
September 1985, Report No. 689 -0.
Semi-planing vessels in a seaway, comparative prediction of
operability.
-A. M. van Wij ngaarden and W. Béukelman.
October 1985, Report No. 755-P.
Seakeeping calculations for high speed round bilge
displace--ment ships series of. 20 models.
W. Beukelma.n and J.A. Keuning. .
-
INovember 1985, Report No. 696-0.
Volume y
Prediction of operability of faSt semi-planing vessels in a
seaway.
W. Beukelman.
January i986, Report No. 700P.
Bepaling van de inzetbaarheid op de Noordzee van een serie
semi-planerende vaartuigen. W. Beukelman en F. de Beer. April 1986, Rapport No. 706-O.
Zeegangsgedrag als ontwerpparalneter.
W. Beukelman en J.A. Keuning. Nei 1986, Rapport No. 709-P.
High speed displacement hull form series.
Calculated influence, of the pitch gyradius on seakeeping for the parent model..
W. Beukelman.
Volume V (continued)
S1axndrukken op cylindervlakken bij gedwongen oscillatie.
W. Beukeirnan.
November 1986, Rapport No. 728.
longitudinal distribution of drift f orces for a ship model W. Beukeiman.
December 198:8 Report No. 810.
Koersstabïliteit voor een ro-ro schip als funktie van waterdiepte, trim en sneiheid.
W. Beukelman.
Juni 1989, Rapport No. 83:0-O.
DiStribution of drift, forces at 90 degree drift angle. W. Beukelman.
July 1989, Report No. 839-O.
Cross flow drag on a segmented model.
W. Beukeirnan.
OctOber 1989, Report No. 831-P.
De invloed van trim op de richtingsstabiliteit van een Ro-Ro
schip op ondiep Water.
W. Beukelxnan.
Januari 1990, Rapport No. 854-P.
Added resistance and vertical oscillations for cylinders, at
forward speed in still water and waves. W. Beukelman.
Augst 199C,.. Repor.t No. 873-P.
Slamming on forced oscillating wedges at forward speed.
Part I: Test results. W. Beukelman.
May 1991, Report No. 888.
Slamming simulation on penetrating wedges at forward spéed.
W. Beu'kelman and D. Radev.
October 1991, Report No. 888-P.
Hydromechanic aspects of marine safety. W. Beukeiman.
June 1992, Report No. 921-P.
Hydrodynainic aspects of ship safety.
W.. Beukelman.
024B25
TECHNISCHE HOGESCHOOL DELFT
AFDELING DER MARITIEME TECHNIEK
LABORATORIUM VOOR SCHEEPSHYDROMECHANICA
-PREDICTION OF OPERABILI!Y 0E FAST SEMI - PLANING VESSELS IN A SEAWAY
by W. Beukeiman Reportno 700
Lecture for Unive rs'itt Duisburg, January 1986
Deift Unversityof Technology
Ship Hydromechanics Laboratory Mekelweg2
2628CD DELFT
TheNetherlands
Contents
introduction
Calculation of, vertical motions
Experiments and correlation to calculations Prediction of operability
4.1. Relevance for design 4.2. Procedure
Parameter studhies
5.1. Description of projects 5.2. Results
Discussion of the resluts Recommended further research
Conclusions and recommendations. References
Nomenclature li. Figures/Tables
1. Introduction
To use strip theory for the prediction of. the operability of fastsemi - planing vessels it is essential to show
firstthat vertical ship motions and in particular the vertical accelerations may satisfactorily be predicted by
this theory. This holds especially with respect to the high forward velocity in combination with different values of L/B ratio's as usual far these ship types. For thjs reason reference is made to experiments in waves with fast displacement ship'swith a normai [i] and low L/B - ratio
[ 2 ] . Comparison is made with calculated resiit? in which the speed influence is täken into account in two ways. The agreement appeared to be satisfactory in particular for
the verticaL accelerations.
Afterwards a. procedure has been deveÏoped' to determine the
operability of .a ship in head waves dependeton some
pro-posed vertical, acceleration criteria and an ass.ume.d wave
climate. , .
The operability of ship and crew i reduced significantly' long before. the s'hip'smoti,ons become excessive. From this
insight the desirability has emerged in recent years to treat sea'keepin'g as an objective parameter in' pre.limi.nary
ship design.
The design information on se'akeeping is needed already in
the very' first stage where some freedom is. still 'present. in the selection of main dimensions and hull form.
The effects of key design variables on the cperabiiity has
been in.vestigated by systematical variation of. some main
-parameters such as length, beam and draught for a North Sea wave climate as presented in [3].
The choice of the wave climate,, the acceleration criterion
and its location of applïcation is left to the designer.
I.t is discussed that the operability percentage with respect to the assumed acceleration level i's a relative measure of
merit whIch,. can be applied for comp arison with other ship' s to promote the possibility fo the designer.to make a choice.. It might, however, be very weil possible in the 'future, th'at
in :sOme cases -ct'Ier -phenomena. repre sent 'the:. 1eading 'fac .tor
fOr the determin'at±on of the operability auch as slamming, rolling', shipping of green water or the available power on board of a Ship.
in 7,8,9 J
-2-2. Calculation of vertical motions
Prediction of the vertical motions and added resistance in waves is based on the well - known strip theory.
For the determination of the two .- dimensional added mass: and damping of ship like cross sections,, as required by the strip method, the ship section is conforinally mapped
to the unit circle and a distribution of muitipoles is used for the solution as proposed by Urseli in [4]
For the vertica1 motions this number of multipoles is
usually restricted to 5.
The. mapping is done by the following general transformation
formula:
w=a{E+
an=O 2n+1
-(2n±1)
}
in which represents a point on the. unit circle and w represen.ts.apoint on the ship's section.contour..
(w and E are complex coordinates)
For n 1 the so called Lewis - transformation.,is obtained.
which in general provides sufficient accuracy for most ship.
sections
This Lewis - trans formation determine s .the ship : section:- by.
the breadth/draught ratio. and the ship sectional area
coef-ficient. .
A procedure of this transformation for ship like cross -sections has been presented by Tasai [5] and Grim [6].
A more accurate approach of the ship section may be obtaifled by the. "close - fit" transformation for which case in formula
(1) n > i
A conclusion of the. study in [i] was that for these ship types hardly any, improvement can be achieved with a close - fit
transformation of the ship section.
After determination of the hydrodynamic coefficients for each
section the values for the whole, ship are obtained by integra tion over the .ship' s length according to the method presented
For different frequencies or wave lengths and forward speeds the response functions may be determined for the vertical motions, accelerations and added resistance in waves.
-3-- version 1, sometimes called the ordinary strip method (OSM) leads to a set of motion equations which lack some of the symmetry relations in the mass coupling coefficients and some additional terms in other hydrodynamic coefficients. For vesion i the speed influence is taken into account only for the derivative of the sectional added mass with respect
to the ship length. In such a way,. only terms are introduced with:
- version 2 also takes into account the speed influence related to the derivative of the damping coefficient N' with respect.
to the ship length and so terms are introduced with:
dm' dN'
V and V
in this way the mentioned symmetry relations are present. in the
hydrodynamic coupling coefficients and so the presentation agrees
with [8]. .
The added resistance may be caicu1ated according to the method: of Gerritsma and Beukeimar as developed in [io]. . Theirmethod ith
based ön the relation between the radiated damping energy as
cal-culated by the. strip method and the added resistance in waves
accounting forthé relative motion of the ship with respect td the
water surface. ..
Generally it is stated that the next assumptions mean. a
restric-tion of thé strip theory:.
i the ship form should be slender with graduai change of this
form in longitudinal direction.
.2. the frequency of motion should not be too low or too high.
-4-Experiments and correlatión to calculations
In the past special experiments have been performed to gather more information about the limitations of strip
theory as mentioned ïn chp. 2.
With respect to the first restrictioñ reference is made to [7] in which investigations are described related to the ship's slenderness. The surprising result was that even for L/B = 4 the calculated responses in head waves show a good agreement with the experimental ones for normal ship
speeds.
Very high forward speeds have been considered with respect tó the round bilged NS systematIc Series of High Speed Displacement Hull Forms as reported in [i] and [iii .
Cal-culated and measured results for 6 models of this series
including the parent model ( L/B 8, B/T = 4, Cß = 0.4) have been presented in [iJ for two fórward speeds viz. Fn = 0.57 and 1.14 and areshown in flguie..1.and.2..
From thé correlatiôn of measurement to computation related.
to the trans:fer.functions of heave, pitch,' vertical.
.acceie-ration and wave added- resistance it was concluded.in [i]
that:
version 2 generaiIy showed too high values
the differences between calculations according to version 1 and "close fit" are negligible.
the agreement between measurement and calculation is
satisfactory for heave, pitch 'and vertical acceleration
for both speeds and for this parent model up to Fn = 0.57
also for the added resistance in waves.
For the highést speéd, Fn = 1.14, the deviation between experiment and calculation is strong for the added
resistance in waves.
Within framework of the project model - experiments have been carried out in irregular seas for different average periods
and for different significant wave - height to check the.
5
-Very recently it appeare from comparison of calculations and measurements for 20 models of the above mentioned series that up to Fn i the agreement is satisfactory for the absolute
vertical motions and acceierations,.
FOr the relative motions and added resistance in waves this
agreement is absent,, especially, at high speeds. This
consider-able lack of agreement might be due to the significant infiuence of the ship's own wave system and dynamic swell up phenomena
which are appreciable at these hig.h speeds.
Another experiment at high speeds has been carried out by the Ship Hydromechanics Laboratory of the Deift University of
Technology for the Ñational Foundation for the Coordination of Maritime Research (CMO) in The Netherlands.
This test has been performed in framework of a: project to pre-dict the operability of semi - planing vessels with
systemati-cally vared main parameters as reported in [2].
The experiment was reiated to the wide. beamed parent modél of
this series with LIB = 4.66, BÍT = 3.48, CB = 0.38 and has been carried out in regular and irregular wavs at forward speeds
Fn 0.724 and 0.905 which agree with respectively 20 and 35 knots for the ship.
Thé results of: 'the experiments together with the strip theoy' calcuiations are s:hown in the figures 4 and 5 for heave, pitch,
the accessory phase lags and the vertical acceleration at station 12.
Also for. thIs wide beamed model at high speed it appears that
the agreement between experiment and calculaticn is satifactory for the absolute motions heave and pitch and the vertical
accele-rations.
Relative motions had not been taken into consideration for this test.
The measured and calculated results in an irregular Piexson -Moskowitz wave spectrum háve been determined for the. same..two
speeds, two peak periods viz. T = 4.8s and 8.8s and a signifi-cant wave héight i/3 = im.
These results TaIso: presented in figure '5 are not sò òonTïtant
as for the response functions.
The agreement between prediction and experiment is in general
-6-with. T = 8.8s aidfor the pitchïng motion and
vertiçalaccele-ration at the lowest, speed with T = 4.8s..
Looking at these deviations one should keep in mind that measu-ring at high speed in a wave spectrum requires a good number of
runs because of the short measuring time per run.
For .each condition 5 runs heave been carried out what might have been too low. .
4. Predidtlon of operabïlity
4. 1 Relevance for design
The performance of a ship in a seaway is especially regarding the crew strongly dependent on the arise of motion sickness which in particular is related to the
vertical accelerations.
For this reason performance dependent on vertical,
acce-lerations determines to a great extent the operability
of a ship.
The operability is defined here as the annual time per-centage in which for a vessel, travelling at a given
speed in head waves, a specified acceleration criterion at a certain locatiön ön board is not exceeded.
it is easily understood. that in recent years seakeeping became more and more an objective parameter in prelimi-nary ship design.. The behaviour of a ship in a seaway
is dependent on a number of parameters. The speèd of
the shp and the main dimensions (volume,, length,, beam, draught) are of prime interest.
The undérwater hull form parameter's and the weight dis-tributiön are for these fast semi-planing' ships of
secondary importance. A detailed description of the wave
climate to be ericounterd is indispensable. .General]y it is represented by wave spectra chàracterized by .signif
i-cant wave heights and wave periods.
The choice of an acceleration criterion and its location
of appiicat.iòn is up. to the 'designer. The effects of key
design variables (speed and main - dimensions) on the
operability shÒuld: be investigated by parameter studies, which are 'Suitable for interpolation by the ship designer.
One of the firt quantities to be limited in ship design is the displacement. in theory, the distribution of a fixed volume over main-dimensions and hull-form is free. The selection of main-dimensions can now also be
judged from a seakeeping point of' view.
4.2 Procedure
7
-8-acceleration it is essential first to formulate for one
or more locations an acceleration criterion and secondly
to choice a relevant sea area for which the wave climate
is known., Mostly this wave climate is presented in tables
on seasonal or annual base showing the joint probability
of wave period and waye height observation classes.
An example, shown for Area 4 of the North Sea ( see
Figure 6
).from the NATO wave and wind atlas,, compiled
by S.L. Bales
ai [3]
,is dnionstrated in Table i on
annual base.
Afterwards the significant acceleration amplitudes are
calculated for the locations considered. in case of a unit
-significant wave height of i metre.
Figure 7 shows for a fast semi - planing ship with
dif-ferent lengths the significant acceleration arnp]itude
dependent on -the longitudinal, position..
The significant acceleration amplitudes per unit wave
he ight' are computed for a series of: moda-I.
or average.
wa-ye periods, as denoted in the wave 'cli.'rnate' table and
with respect. to the speeds considered-..
These acceleration values. may be presented. in. a table,
for inst'an'ce-table.'21 ,in...,cas,e of three. locations and, ...6.
forward- speeds;
The tables are suitable to. use for wave spectra with
different average ormodal wave periods.
Assuming a linear relation. between wave height and
re--sponse the acceleration results for each wave period are
obtained after line-ar multiplication by the- significant
wave heights classified according to th'e wave climate
table. For those combinations of wave period arid' wave
height where the maximum allowable significant
accelera-tion amplitude was not'exeeded, the percentages of
occur-rence presented in the wave climate table are added.
'The total sum of these percentages gives the, probabilistic
standard of operability, expressed- as a percentage of the
seasonal o.r annual wave occurrences -in the -sea area under
consideration.. In table i an example of an operability
calculation 'is presented.
In this table the values within the thick line indicate
5. Parameter studies
5.1 Description öf projects
As already mentioned in chp. 3 parameter studies for the
operability of high speed semi - planing vessels have been carried out for the National Foundation for the Coordination of Maritime Research (CMO) [2 J..
The widé beamed parent model(L/B 4.66, BIT 3.48,,
CB = 0. 38) is a Dutch designed and built hard - chined patrol vessel.
Two clusters f seven ships were created by variation of the main dimensions. See Figure 8.
The small vessel series (ship length arOund 20 metres)
was studied by the Deift University of Technology (PUT), the large vessels (ship length around 35 intres} were
covered by the Maritime Research Institute Netherlands (MARIN.).
The block coefficient and the longitudinal location of
the centre of b.uoancy were kept çonstant throughout the
whole series. In each cluster one of the main dimensions
(L, B or T) was varied twice while the other two main':
dimensions remained constant. Under these restrictions the displacement varied proportionally to the variable
main dimension.
The two clusters of variations in Figure .8 are connected along, the length axis (ship nos. 7 and 8).
The differènce in displacement however is such, that each
cluster should 'be' considered separately.
The parent of the second group (no.11) was a re-scaled
35m long. version of the actual parent form,, no.3.
The ship speeds were chosen in coherence with. the ship lengths. The small vessels (L = 15 - 25 ni) can becompared
at 15, 20 and 25 knots, for the. longer vessels (L = 25 -.45 m) speeds of 20, 25 and 30 knOts were selected.
Moreover, for each ship the calculations were performed
for a number of intermediate speeds.
Their çhoice enabled. a: comparison at, two 'constantFroudeT -number values, viz. 0.724. and 0.905, for-t'he---ent'i-re ship
- lo
In total the systematical series of 14 ships covers ship lengths from 15 - 45 metres, displacements from 33 up to
286 tons and a speed, range from 15 to 35 knots.
The responses of all ships in irregular long crested head waves were computed by the strip theory computer
program TRIAL of the Deift University.
Version 1 for the speed influence and the Lewis -
trans-forinatiön of the ship section to the unit circle have
been used,. See chp.2.
-For the determination of the response amplitude operators a total of 33 wave length - ship length atios wer intro-duced in the program. The longitudinal radius of gyration
kyy was fixed at O.25L.
The Bretschneider formulation was chosen to describe the
wave spectra and. applied for Area 4 of the North 'Sea as denoted in chp.4.2 and [3}..
The significant vertical, acceleration amplitudes .were.
calculated' at unit 'significant wave héight for a w-ide.
range of modal wave periods;:
= 3.2 - .1.6.4 Seé table' 2..
The results were collected in tabular form and as an
example for ship no.11 shown ïn table 2.
For each ship the accelerations were calculated at the following longitudinal location:s: .0.00 L, O..5i2.LW,L and 0.939 'WL from the aft. point at WL.
The following combinations of acceleration criterion and
its lo.catiön of appiïcation have been considered: - For thé small veései. (L = 15 - 25m) by DUT:
- a1!3 O..5g at 0.939' Lçq
- a1!3 O..5g at 0.512 LW.L
- For the longer vessels (L = 25 - 45m) by MARIN:
- 5 0.3g at 0.512 LWL a1/3 O.5g at 0.512 - a113 S 0.5g at 0.939 LWL
On small fast vessels the. bridge and accomodation are
often located near midships. Therefore the criterion /
location combination of. O.3g at 0.512 L or 0.434 .LWL
yields the most realistic option' for design operation.
5.2 Results
For all ships .a number pf. operability percentages is
cal-culated at several speeds and acceleration limits.
A relation 'between operability and main dimensions has
been illustrated in figure 9 for the grd.upof small
vessels (L = 15 - 25m) in case of y =. 20 'and 25 knots"
two Foude numbers Fn = 0.724 and Fn = 0.90.5 and a13' 0..4g at 0.4.34 LWL.
The same relation has been demonstrated in figure 10 for
the longer. vessel..qoup (L 25 - 45m') in case of 0.3g at 0.512 LWL.
From all computations and figures in general it appears that operability increases with length especially at the
lower speeds, while' it slightly decreases on base of dimensionless speed, the Froude number. Moreover it. has been, shown that increáse of beam slightly improves the
operability while draught does not almost effect the
operability. Ali these results are based on, linear varia-tion. of one main dimension sothàt the volume also varies linear with this dimension.
Figure 1.1 shows the 'operability on volume basis for the
group of longer vessels in case of V = 20 and 30 knots
and i/3 0...3g at 0.512 L. From this figure 11 it also becomes clear that volume variation by means of draught
does 'not influence the operability.. Most effect on thé operability is demonstrated with length and.be:am yariation
for the lower speed (V = 20 kn) at the_hi.ghervoiume.sand
12 -6. Discussion of the results
Correlation of measurement to computation related to the
motions of, fast semi - planing ships in waves yield that
at iet for the vertical motions and accelerations the
agreement is satisfactory. For the relative motions and the added resistance such an agreement could not be established. In generai it appeared that version 2 delivered too high values while hardly any improvement could be obtained by the close - fit transformation.
For these reason's preference should be given to ver.ion 1 of the strip theory.
The computed operability results obtaïned by means of the parameter studie's may be judged. on twö aspects':
i. Variation of one main dimension with the same linear
variation of the volume.
2. Variat'ion..,,of.one.or,'more:maindimêns'ions on base of
a constant volume.
In the present study. the first mentioned, aspect .is. mainly: emphasiz'èd'., althOugh. some. comparisons ;Ofl, base': of' 'constant:
volume.' have 'been', made. '('f igure iL) ..
Looking 'at thé first aspeòt it generally appears that on
base ' of constant shIp length increáse of beám reéui.ts in improvement of the opérabïlity with an' average of 4% per
metre.' See' figure 9 and lo.
However this trend Should not be pursued beyond realistic hull shape limits.Stretching the beam for instance decrea-ses' the de'ad rise angle 'and hénce 'increáses the sensitivity
to bottom slamming and the 'still water resist'ancè.
The trend with length 'increase at cons:tant beam is generally
beneficiai for smaller vessels (about 1% per metre).
There is also a clear effect of speéd in relation to length.
It appeárs that increase of leigth improves thé 'operability
especially at lower speeds and slightly decreáses on base
of Froude number. See figure 9.
- 13
been changed by the predominant presence of short wave periods.
The e.ffects of draught changes at constant length. or breadth are marginai as shown in.the figures..
Looking at the second aspect with variation of one or more main dimenions on base of constan,t volume (figure 11) it is shown that for the wave conditions considered improvement of operability may be achieved with length and beam variation
in case. òf lower speeds at relatively hi gh volumes and for
the higher speeds at the lower volumes.
The resulting operability percentages show considerable differences dependent on the accuracy and refinement of the
presented wave stat±stics..
Therefore it must be concluded tha.t the operability figures
Should be regarded as a relative measure for the prediction of performance.
The more. refined wave height intervals and wave periods may
be used for the. prediction of the operability, the more the:...
absolute measure is approached..
Nevertheless, by means of, the comparative prediction method
a useful tool is supplied to the designer to determine and improve the seákeeping behaviour.
It should., however, be kept in mind, that.. both physical an'd.
practical limitation's exist resultin into reâlistic
para-meter combinations dependent on ship length and speed for these rela.tiveIysmall semi - planing vessels.
14 -7. Recommended further research
In the foregoing sections a number of limitation's of the current investigations have been 'indicated.
Future research will be aimed at reducing these limitation's.
in a first analysis the seakeeping behaviour of small semi-planing vessels has been regarded to be dependent on main
dimensions', ship speed,, wave climate and the chosen combi-nation acceleration / location criterion.
In generai it is known that the vertical acceleration
ampli-tude level is representative for the operability of ship and crew. However, human performance degradation is also
depen-ding on the frequency of ship motion [12].
This aspect is very important in relation to the chosen wave
climate and the forward speed of the ship.
Further investigation is needed with respect to this pheno-menon. PredIctions of the operability should also be
perfor-med for wave climates, with different average 'wave 'periods
and direction's:.
Therefore .a reliable, and detailed statistical description of the..wave climate is indispensable.
Another important:limitation for the operability. to. be. taken.; into account. might ,be,. the,..availab1e power ,'of'. the, ship..
In this respect the added resistance in waves and the stili water resistance should be determined. The safety of a vessel
is ultimately affected by extreme responses. Harmonic motions and accelerations can be predicted with a reasonable degree of accuracy, but insufficient progress has been made so far
in .accurate predictions of peak values and slamming phenomena.
Further refinement of the operability prediction.could be achieved by adding the effects of the underwater hull form parameters. It is advised to carry out such calculations in
a parameter study at constant displacement.
Finally it should be mentioned that it might be worthwile to account in future research also for deck wetness, horizontal and rolling motions and accelerations. In this respect it should be emphasized that for the prediction of deck wetness
15
-8. Conclusions and recommendations
From the investigations presented in this study the following
conclusions may be derived:
- Comparison of experimental and calculated results with respect to the motions of fast semi - planing ships in waves showed that striptheory may be used mainly for the prediction of the vertical motions, heave and pitch and the vertical accelerations.
Preference is given to version 1 of the striptheory above
version 2, while it has been shown that a Itciose - fit"
transformation did not yield significant improvement.
- Operability calculations showed that a beam increase
re-sulted in an improvement. A slight beneficial trend with length was found, only valid for the chosen North Sea
wave climate.
The effects of draught were marginal.
Increase of speed reduced the operability percentage.
- Provisionally the operability figures should be regarded as a relative measure for the prediction of seakeeping performance in ship design.
It can only become an absolute measure when the prevailing wave conditions can be specified sufficiently accurate and when other phenomena limiting the operability can be
taken into account.
- These other phenomena also determining the operability which should be investigated in.the future are:
- formulation of the vertical acceleration criterion both for amplitude and frequency related to human performance
degradation.
- the effect of added power in waves in relation to the available power of the ship and hence the prediction of the relative motions in a seaway.
- the prediction of acceleration peak values all or not
-16-- the influence 6f under water hull. form parameters..
- extension of the ópe±abïlity prediction procedure with deck wetness, wave direction, horizontal and rolling motions..
9. References
Biôk, J.J and Beukelman, W.,
"The High - Speed Displacement Ship Systematic Hull
Forms - Seakeeping Characteristics",
Transactions SNANE, New York, November 1984
Wij:ngaarden van, A.M. and Beukelman, W.,
"Semi - Planing Vessels in a Seaway, Còmparitive
prediction of operability",
MARIN Workshop on Deeiopments in Hull Form Design,,
session 5, Wageningen, October 1985,.
BaIes, S.L., Lee, W.T. an:d Voelker, J.M.,
"Standardized Wave and Wind Environments for. NATO
-Operational Areas ",
Report no. DTNSRDC/SPD - 0919 - 01,, DTNSRDC, Bethesda,, July 1981.
Ursell, F.,
"On the vïrtual, mass and damping öf :fio.atinig bodies
at zero speed ahead",
Symposium on the Behaviour of Ships in a Seaway,
Wageningen,, 1957.
Tasai, F.,
"On the damping. force of added mass of ships heaving and pitching",
Reports of Research Institute for Applied Mechanics, Kyusha UrJversity, Japan, 1960.
Grim, O.,
"A method for a more precise computation of heaving
and pitching motions, both in smooth water and in waves", Third Symposium on Naval Hydrodynamics, Schevenigen, 1960.
Gerritsma, J., Beukelman, W. and Glansdorp, C.C.,
"The effect of beam on the hydrodynarnic characteristics of ship hulls",
17
18
-Salvesen, N., Tuck, E..O.. and Faltinsen, O.M., "Ship motions and sea loads",
Transactions SNAME,, vol.79, New York, 1970
Beukeiman, W., Huysmans, R.H.M. and Keuning, P.J.., "Calculation methods of hydrodynamic coefficients of ships in shallow water",
Ship Hydromechanics Laboratory, Deift Hydraulic Laboratory,, Maritime Research Institute, Report nb. 571-A, 1983..
Ge'rritsma, J. and Beukeiman, W.,
"Analysis of the resistance increase in waves of a
fast cargo ship",
international Shipbuilding Progress, 197:2
Oossanen. van.,. P. and Pieffers, J.B.M.,
"NSMB'Systematic Series of High.- S.peed.dispIacement
Ship Hull Forms",.
Paper. 1, Ses'sion.IV, MARIN Workshop on Developments
in Hull Form Desï.gn, Wageningen,'October..:1.9.85:...
12]i Pàyne, P.R.,
"On Quantizing Ride Comfort and AlÏowable Accelerations",
AIAA/SNAME Advanced Marine Vehicles Conferences,
10. 'Nomenclature a al /3 B C,B. Fn g H113 k L, LWL N' T T V w x,y, z z E e X V p 19 -transformation coefficient
significant acceleration amplitude beam, on waterline
biockcoe f ficient
Froude number = V/
L
acceleration due to gravity significant wave hight
wave nuinber= 2rt/X pitch gyradlus
ship's length on the waterline sectional added mass
sectional damping coefficient' ship's draught
average wave period
modal or peak period
förward speed
point on the ship section
right hand coordinate system fixed to :the ship
with the origin situated in the waterline and the port side. 'positive
heave displacement
displacement of water surface point on the uni,t circle
phase lag pitch angle.
wave length
displacement of, model or ship
Cs 1.5 1.0 (s I-fl m P.1 05 O
t
1.0 Q5 10 15 .7 5i 0;5 10 15 vt?çCorrelatlon!ofmeasurement.to computatlonforpltchtransfer Correlation of:measurement io computation for wave added functions.
' resistance transfer functions
- Systematic:SiesHùIÌForm .:
-MODEL 5 Fn 0.570 VERSiON 1 2 Flit EX9 VERSION CLOSE MARINo
-MODEL 5 Fnfl 0.570 'VERSiON' 1 2 FIT EXP VERSION -.-- CLOSE o MARINr'
I \: 0/ ' 0/ MODEL 5 Fn = 0.570 'VERSION' 1 2 FIT EXR' --- VERSION._.CLOSE
0 MARIN MODEL 5 Fn=O.570 VERSION 1 2 Flit 'EXP VERSION CLOSE MARIN 05 10 1.5Correlation of'measùrementto'computátionfor heave transfer
functions
0 05 10
vc7 1.5
Correlatlonofmeasurementtò cornputatIonforaccèIeration transfer ftìnctlons:
15
O
75
50
Systematic Series Hull Forms
-Figüre 2 [ii
MODEL VERSION i
---VERSiON 2
---CLOSE FIT
En: 1.140 0 MARIN EXP
f-'
0/\
.bk
o o o o MODEL 5 Fn: 1140 VERSION 1 2 VERSION\\ /
MODEL 5 Fn,: 1.140 VERSION 1 2 FIT 'EXP VERSIONt MARIN...CLOSE
\
MODEL 5 Fn: 1.140 VERSION. 1 2 FIT EXP VERSION CLOSE o MARIN. t.'I'
I Op ¡ o cXj O 0./r\
k ot'!
05 io 15 05Vx
1.0 15Correlation of measurement to computation for heave transfer Correlatlon:of measurement tocomputatiòn for acceleration
functions transfer functions
0 05 10 15
Correlationlof measurement to.computation for pitch transfer functions
05 1.0
f
15Correlationof measurement to'computatIonfor wave added resistance transfer functions
1.0 (5 1.0 (5 I.', (5 o 05 15 lo N C) o. -j 5
1.5 10 (s 0.5 300 200 _J (s 100 o 1
Correlation of irregular transfer functibns measuredand computed for pitch
SystematIcSeriesHujiliorms: 75 0.3 o o 3 2
Corrélätion of Irregular transfer functions measured and computed for accelerations
2 3
IL/f 2
Correlation of Irregûìar transfer functions measured and computedfor wave added resistance
MODEL 5 Fn = 0570 VERSION 1 2 FIT EXP _VERSi0N CLOSE MARIÑ MODEL 5 Fn. 0.570 VERSION 1 2 FIT EXP VERSION -.-.- CLOSE - MARIN MODEL 5 Fn 0.570 VERSION .1 2 FIT EXP - VERSION CLOSE MARIN MODEL 5 Fn = 0570 VERSION 1 2 F'I EXP ---VERSION ---.- CLOSE MARIN L/2 2 3
Correlation of irregular transfer functions measured and computed for heave
0L Ca 2.5 1.5 1.0. 0.5 0 .calc. O exp. model no. 3 calc. -Ø exp. model no.,3 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4'
Figure 4..
o 2.0' 1.5 eaL. Ca 1.0 0.5 -80 -120 -160- CeC -200' 24O -sha-ilowl -280. ,ater1 caic. shal1oÇ,. water i2uence ..._. calc-o exp. model. no.3' o 0 0.2 0.4 0.6 .0.8 1.0 1.2 1.4 Fn 0.905 o model no.3 V7x V7A 1.6 .0 0.4 0.8 1.2 yTx2 shallow water Fri 0.724 1/3 1a a L a 200 150 50 Zi, 81, al
f
i1 m,degr. ,m/s' o o 0,. 4 1.2 1.6 o 0.4 0.,8 1.2 1.6 L/k 5 10 15 o s 10 15 s O heave p O heaveA pitch calc. A pitch
calc. O acceleration Q acceleration
at ord.12 f at ord.12
heave heave
A pitch, exp. A pitch exp.
fl acceleration i acceleration
60°
300
Figure 6. Selection of representative: areas in the North:
Atlantic Basin.. [3]
Annual wave' climate. statistics: for: 'Area 4 (North: :Saa...,
from.DTNSRDCReportSPD -09l9 - 01
Table i. Example of an operability calculation for the North Sea area. Results for schip no.11 at 30
knots speed and acceleration criterion ai13 < 0.3g at 0.512 LWL. [3] ' SP6
cj
o*i
-W1.
o o °2
..
f's. 'A.
I0.8
rv
I t1rjc°:eo O .017
0
No. sec. freq-uency of nil3 opera-bility ft113 (metres) 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 1 3.2 2.4 2.4 ' 2.41- - - -2 4.8 3:.5' 3.5 1.8 1.7 - - - -3 6.3 11.0 10.8 3.4 7.4 0.2 - - - -4 7.5 14.3 10.8 4.2 6.6 3.6 - - - -5 8.8 13.3 6.8 3.2 3.6 5.6 0.9 - - - -6 9.7 ' 17.6 7.1 3.7 3.4 5.3 4.6 0.5 - - - - -710.9 1.1 4.3 2.1 2.2 1.6 1.8 2.0 0.4 - - -8 112.4 9:.8 4.3 2.1 2'.2 1.1 0.9 1.2 1.6 Ó.'6 0.1 - -913.8 5.2 3.3 1.3 1.3 0.7 0.5 0.3 0.1 0.3 0.3 0.1 -. 10 15.0 8.7 6.,7 3.4 2.1 1.2, 0.8 0.3 0.2 0.2 0.2 0.2 0.1 11 16.4 3.7 2.8 0.8 0.8 0.7 0,5 0.3 0.2 0.1 0.1 0.05 0.1 Total ' 99.6 62.8 000 600 300 W 0° E 30° 70° Na.113 t 7 5 4 3 2 1 0
Tab le f icant erticai, ácce iéral±ion amplitudes,
ád
Location Ship speed . Modal wave period T (s. )
(knots.J
p 3,2 4,8 : 6,3 7,5 8,8 9,7 1O..9 12.4 13,8 . 15,0 16.4 0.00 L.,L 15OO 0,415 1,566 H 1,634- 1.379 1,214 1,024 0,835 Ó,698 O,6ÒS 0,516 20,00 O;442 1,684 I 2,108 1,963. 1,682 1,409 1,261 1,030 0,861 0,746 .0,636 25,00 0,418 1,728 2,344 2,255 1,969 1,756 1,496 1,228 1,1029 0,892 0762 26,08 30,00 32,60 0,408 0,353 0,308 1,730. .1,720 1,7.02 2,385 ', 2,510 H .2,57,3 2,311 2,495 2,600 2,627 2.223 2,342 1,811 2,000 2,116 1,546' 1,71.7 1,824 1,270 1,416 1,509. 1,065 1,191. 1,271 0,923 1,034 1,105 0,789 0,884, 0,945 35,00 0,265 1,682 2,621 2,687 2,443 ' .2,216 1,910' 1,592 1,343 1,168 '1,000 0,512 L' 15,00 0,200 0,926' 1,27.6 ' 1,1235 1,080 0,976 0,839 10,695 0,587 0,512. 0,440' 2000 0 191 0983 1 501 1 510 1 357 1 227 1 060 0 881 0 745 0 649 0 558 25 00 0 187 0987 1 644 1. 714 1 575 1 437 1 252 1 045 0886 0774 0 665 26,08' 0,187 0,977 ''1,666 1,751 1,617. 1,478 1,289 ' 1,078 0,915 0,799 0,667 3000 0181 0953 1729 1866 1 752 1613 1416 1 190 '1012 0855 076232,60 'o','iiI 0,933 ' 1,757 ' 1,929 1,830 1,693' 1e492 H 1258 1'e072 0,939 .0,809
'35,00 0,158 0,912 ' 1,775 1,980 1,896 1,762 1,559 H 1,125 0,986 0.650, 0,939 i11,His,00 0,547 2,135 2,610 2,403 2,040 1,759 1,509 1,223 1,017 0877 0745 20,00 '0.505 '2,074' i 2,750 2.632 2,284' 2029 1,721 1,405 1,173 1,013 0,662 '25,00 26,00' 0,474 0,461 . 1,969 1,944 . 2,812 1 2,815 2,769 : 2,791 2,453 2,043 2,200 2,231 1,802 1,912 h 1,546 1,573' ! 1,296 1,320 1 1,122 1,143 0,1958 '0,976 '30,00 0,396 1,055 ' 2,816 2,056. 2,579 2,332 2,01.1 ' 1,663 ' 1.399 1,214 1,038 'i 32e6O ' Q.344 1,797 2,000 2,000 2,633 2,391 2,070 ' 1,71.7' ' 1,440 .1,258 1,076 35.00 0,296 H 1,747 2,796 2,913 2,670 2,442 2,121 1765 1,490, 1,296 1,110 0 8 10 12 14 .16 18 .20 22 24 ORD.No Figure 7.
'Q
Model No. Parent model T. THD '7 \ N N\3 \\
V4 MARIN\
N' vsFigure 8. Overview of the variations in main dimensions for the
model series of semi-planing vessels in a seaway. For ail models CB O. 38 and LCB = 46 i.% L.. ,[2}
Parameter Symbol Dimension
Index -1' L 2. 3 4 5 6 7 Volume . L m3 32,0 44,0 48,2 53,3 154,1 215,7 277,4 Length waterline L rn 15,0 20,6 25,0 35,0 45,0 'Beam waterline B n 4,42. 4,,85 5,36 7,51 9,65' T m 0,92 '1,27 154 2,16 2,79 Draft
>. 80 a 60 o ft 60 40 40
Figure 9. Operability as a
function of'
main dimens ions and ship speed.The
criterion is
5 0.. 4g at
O .434L. B 4.42 m T = 1.27 m 25 20 kn (Fn (Fn = = 0.724) 0.905) L B = 20.6 4.42 in in 25 kn >1 .i '-4 -I -a a) I.1 80 En = 0.724 B = 4.42 m T = 1.27 in - -- En = 0.905 >, i -I -4 -'-4 .0 a) o 80 60 draft (m)©
1.27©
1 '54©
20 kn (En (Fn = 0.724) 0.905) L T = 20.6 m 1.27 ¡n --- 25 'kn 40442 beam, (m)©
4 . 85 5.36©
5 length (m) 20.6 25100
r.:
5.36 40 25 Ship 8,9,10 154 Brn Cm) 3 Volurno Cm 7.51 Length (ml 35 Shi1p u 215 9.66 B = 7.51 T = 2.16 Ship 12.13,14 277 0.512Figure 10. Operability as a function of main
dimensions and ship speed The criterion
IS
< 0.3g at 0.512 LWL. [2] 80 60 80 1 -4 -4 60 40 150 200 Volume (in3) 3 Volume Cm 250 250 300 300Figure 11. Operability as a function of volume. For all ships CB=O.38 and LCB=46.1% LWL. [2] V = 20 kn. a113 < 0.3 g at 0.512 L
O
Ship No. Length Beame
Gf.
-Lenqth \o
/.
/_
Beam - -V=3Okn. a1,,3 < 03 at 0 512 g 100 80 60 40 1 100 80 60 4O = 20 kn. 30 kn. L = B = 35.0 7.51 56 Drift (m) - - 2 16 2.76 L = T 35.0 2.16 B 7.51 ; T = 2.16 Length-variation L 35.0 ; T = 2.16 Beam -variation L 35.0 ¡ B = 751- Draft -variationBEPALING: VAN DE INZETBAARHEID OP DE .NOORDZEE
VAN EEN SERIE SEMI_PLANERENDE VAARTUIGEN.
Rapport no 706-O
Opdracht no: 5H-O-2285 Ari1 1986
Gerapporteerd door: W. Beukelman en F.. de Beere
Onderzoek uitge.voerd in opdracht van: de Di recteur_Generaal: Scheepvaart en
Mari tieme Zaken te Rijswij.k Z..H.
onder kontrakt DGSM nr 242 (1:985 art. 81-2 nr IO.)
*) Dienst Vaartuigen, Afdél iing Projecten
Rapporten betreffende opdrachten, kenbaar aan de
letter t101! achter het rapportnuimner, zijn uit-sluitend besternd voor de opdrachtgever en mogen niet a'an anderen ter inzage worden gegeven.
Deift University of Technology
Ship Hydromechanics Laboratory
Mekelweg 2
2628 CD DELFT
The Netherlands
Phone 015-786882
Deift University of Technology
Ship Hydromechanics Laboratory
Vakgroep Hydronautica
r.J. Gerritsma,
Inhoud: Inleiding Mode ifami i je Zeegangscriteria Inzetbaarheid 4.1. Algemeen 4.2,. Methodiek Onderzoek 5.1. Condities 5.:2. Presentatie resultaten
Discussie van de resultaten
6.1. Berekeningen van de inzetbaarheid: 6.2. Aigernene tendensen 6.3. Beperkingen Conciusies en aanbevelingen Symbolen Referenties Tabellen U. Figuren Bi:jlage i
1.. Inleiding
Bi j het ontwer:p van klei:ne en snelíi!e vaartuigen is er een toenemende behoefte
aan gegevens waarmee de Lnzetbaarheid van ship en bemanncing in zeegang beoor-deelid kan worden.
De inzetbaarheidswaarde kan een be1:ang'rijke factor worden binnen het
toetsings-proces van operatio.nel:e eisen tot instrument vaartuig, zowel technisch, sociaal
als financi eel/economi sch gezien.
Inzetbaarheidswaardefl maken het rnogelijk reeds in het voorontwerpstadium verband
te leggen tussen de uit te voeren taken van een vaa:rtuig èflerzijds en
investè-ri ngskosten/expioitatiekos ten van een vaartuig anderzijds.
De inzetbaarheidswaarde dient zich te ontwikkelen als een .maat voor onderlinge verge1i.jking van varianten in het scheepsvoorontwerp.
Hat uiteindelijike doe] is de verheffing van het begrip toelaatbaar
zeegangsge-drag:tot een cbjectieve maatstaf bij hetontwerp van, vaartuigen.
Het doe 1 van het ui tgevoerde ondé;rzoek i s orn de invloed van de bastsparamete.rs,,
zoals hoofdafmetrig van een vaartui,g, Vo:rmcofficiênten en scheepssneihei:d, Cp
de inzetbaaheid zichtbaar té maken.
Gekozen is voor een modélserie van semi-planerendé vaa:rtuigen met een vaargebied. op de Noordzee;
2.. Modelfarnilie
Ce modeifarnil je is gebaseerd op een studie uitgevoerd door de Dienst Vaartuigen
[i) .
Deze studie ornschrijft een ontwerpmethodiek waarbij gebieden van pararnetercombi'-naties te identificeren zijn.
Het gaat orn gebieden waarbinnen de ontwerppararneters van een: vaartuig zich
be-vinden gebaseerd op een aantal uitgangspunten zoals type en soort vaartuig,
snel-heidsgraad en rnateriaalkeuze.
De gebieden worden bepaald coq. begrensd door veiligheidsvoorschriften,
hydro-dynamische aspecten en technische rnogeliikheden.
De studie richt zich op parametercornbinati:e-gebieden van r&Iatief klein maar snelle (patrouille)vaartuigen.
De parameters van de mode1fami1ie zijn za gIçozen dat zu vallen binnen deze
ge-bieden, zodat gesteid kan worden dat het onderzoek zich richt op zo reëe.1
moge-luke ontWerpparameters-c.q. vaartuigen.
Uit onderzoek [2) van de Dienst Vaartuigen:, maar ook uit vroegere:'parameter studies [.3) biijkt dat de scheepsiengte als beliangr1jste parameter .gezien kan worden met betrekking töt. invioed Op het zeegangsgedrag.
-Het adviesvan:de Dienst Vaar.tui:gen volgend uit bovengenoemde ontwerpmethodiek."
[i] , is weergegeven in tabel i en 2 van bijiage i. Dit adviesis -gebaseerdop
3 verschiliende scheepsiengten nL L 15, 25 en 35 m en verwerkt in [4]
0m te kamen tot een gewenste lineaire breedte- en diepgangvariatie behorende bij
el k van drie genoemde scheepsiengten, is de minimum en maximum breedte gekozen
voor de gemiddeide diepgang als aangegeven in figuur
if
Hieruit voigt dat voor elk van de drie beschouwde scheepsiengten 5 modellen zijn berekend ter bepaling van het zeegangsgedrag. De gegevens van deze 15 modellen zijn weergegeven in de tabellen 1, 2 en 3.
De bij elk van de 3 scheepsiengten behorende basisvonu is bepaald met behuip van een compûterprograma van de vakgroep Hydronauti:ca (THD) waarbij is uitge-gaan van een modern semi-planerend scheepstype met getwist viak.
Met getwist viak wordt bedoeld dat de hoek tussen sectiecontour en wateriijn
( de zg. "dead rise" ) per sectie kan variëren. De lijnentekeningen voor deze
basismodeilen zijn gepresenteerd in de figuren 2,3 en 4 voor resp. model 2, 7
en 12.
De gegevens .voo,r de. overiEge modellen zijn bepaald door iineaire .veranderiflg van
resp. de breedte en diepgang waardoor de blokcofficiënt Cß geiiik b.iijft en hat
depi acement eveneeris lineair varieert met resp. de breedte en diepgang. Uit tabel 1, 2 en 3. b1ijk.t dathet minimum eñ maximum depitacement voor zowel de breedte- als de diepgangsvariatie per beschouwde scheepsiengte ongeveer geiik
3. Zeegangscri'teri a
Een vaartuig' wordt in het algemeen ontworpen, op basis van een aantal nauwkeuri.g omschreven operationel.e- c.q stafeisen.,
Wat betreft het zeegangsgedrag van een vaartuig wordt echter ai te vaak volstaan met de omschrijving: Het vaartuig dient een goed zeegangsgedrag te bezitten.
De laats.te tijd 'blijkt heel dûideii'jk dat vooral voor relatief kleine., maar snelle vaartuigen, het vaststelien van zeegangscri'teria een belangrijke ontwerp-parameter kan zijn.
Vooral' bij patrou'i'llevaartuigen kunnen dergel ij:ke zeegangscri tena van zeer grote
en zel.fs -van bepalende invloed zi,jn op het uitei;ndelijke ofltwerp..
Het steT len van d'ergelijke criteria vraagt wel naar een zeer duid'eii:jke
omschrij-ving van het vaartuig als instrument, op basis van de uit te voeren taken c.q.
werkzaamhedefl op het water.
In de studie (2J vanj de Dienst Vaartuigen 'wordt aanbevoen orn de verticale
s'igni-f i'can.e versnelling ä113 ais. zeegangscrirteriiim' te hanteren' zolanggeen nauw-keuriger of 'andere' cri'teria zijn ontw.ikkeTd.
De verticalé significante .ver.sneiling dient zo mogel ijk per sc'heepsordinaat.
'be-paald te worden orn het criteri:um op verschillende plaatsen-in rekening:te kunnen brengen, bijv. in verband met de te kiiezen pl aats van bijv. het stuurhÌiis'.'. De te gebrui ken criteiia kunnen óvereenkomstig'de aanbeveiingen :fl j 2 ais voigt'
geintrodûceerd' Wo'den:
- de verticale significante versnelling in het stuurhuis of rnidscheeps mag niet meer bedragen dan 0.35 g d.,w.z.:
a173 t..oV. stuurhuriS of midsc'heeps 0.35 g
- de Verticale significante versnel"iing op 10% achter de voorloodlijn (VLL) mag' niet meer bedragen dan 0.5 g,, d.w.z.:
a113 op 0.1 L achter VLL50.5 g
Er heeft zich echter nog geen' eendui'dige richtl tin voor een toelaatbare maximum
waarde van de verticale versneili'ng ontwikkeld. Daarom zal voorlopig een ontwerper
de vrijheid moeten word'en gegeven orn zeif een criterium en locatie, te kunnen
bepaien, naast de keuze van belangrijke ontwerpparameters ais zeegebied,
vaar-sneiheid en scheepsafmetiingen.
Voor dit onderzoek zijn de bovengenoemde twee zeegangscriteria gehanteerd daar
het niet gaat 0m absolute waarden te geven, maar modellen onderling te
verge-lijken.
Een voorbeeld van de iflvi'oed van de bewegingen en inzondérheid de verticale ver-snellingen op de rnenselijke prestaties is te zien in fi:guur 5 en 6.
De infonnati e uit fig. 5 geeft aan dat ;bi.j significante versnel lingen van 0.5
â 0.55 g de menselijke prestatie is teruggelopen tot i0%
Uit fï:guur 6 blijkt duidelijk dat de frequentie c.q. ontmoetingsfrequentie ook een zeer belangrijke rol speelt..
Op kleine vaartuigen worden deze waarden al gauw overschreden, los gzi:én van het felt, dat de maximaal optredende versnellingen 2 a 3x hoger kunnen zijn dan
de significante versnell ingen.
Andere criteria dan die gebaseerd op de verticale significante versneiiing.-kunnen tot nu toe niet gehanteerd worden voor snelheden boyen En = 0.6, zoals
blijkt uit een gezamenlij'ke studie van MARIN en THD naar het gedrag van snelle deplacementsvaartuigen in zeegang [5 en 6). 'Deze studie toont namelij:k aan,, na vergelijking van berekende en gerneten resultaten, dat bij snelheden boyen Eh =
0.6 wel goede overeenkomst blijft bestaan voor de absolute bewegingen als stampen, dompen en de verticale versnellingen, maar dat deze ofltbreekt voor de relatieve bewegingen, weerstandstoename in golven etc.
De voor de criteria voorgesteide verticale significante versneïlingen hebbeh
alleen betrekking op de. harmonische bewegingen ten g,evolge van zeegang. Deze
zullen vooral van belang zijn in verband met het optreden van zeeziekte.
Versnellingen als gevoig van g,olfpieken of "siamming zijn nog moeiiijk in
re-kening te :brengen voor betrekkelijk snelle vaartuigen..
Verder onderzoek zal hiervoor eerst nodig
zi:fl
omdat deze verschijnselen ook maatgevend kunnen zijn met betrekking tôt toelaatbaar zeegangsgedrag.Daarnaast moet gesteld worden dat ondanks dat de hevigste reacties optreden in
het verticale scheepsvlak in kopgoiven, andere responsies bij een afwijkende golfrichting oak gróte invloed kunnen hebben op de menseiijke prestatie.
Slingerbewegingen en laterale versnellingen bereiken lin het àlgemeen de grootste
4. Inzetbaa rheid
4.1.' Algemeen
Het onderzoek richt zich op de 'materiëie inzetbaarheid van. een serie modellen
van semi-pianerende vaartuigen ais functie van vaargebied en gesteide
zee-gangs criteria.
De invloed van veil igheidsvoorschriften c..q. t steilen Windkrachtbéperkingen
is bu i ten beschouwi ng geaten.
De inzetbaarheid van een vaartuig geeft aan de theoretische maximale inzet
van een vaartuig uitgedrukt in een % van de tijd.
De inzetbaarheid voor het onderzoek zal hier ais voIgt gedefinieerd wOrden:
De inzetbaarheid geeft het (jaarlijks) percentage tijd aan, waarbij a.an boord van een vaartuig., dat met een zekere snel!heid in recht voorinkomende gol ven vaart, een gesteld versneii i ngscri terium niet wordt. overschreden.
Aan de waarde van de .verkregen inzetbaarheidsfactor/percentage: 'mag geen
,ab-solute betekenis worden gehechtdaar het inzetbaarhedsniveau. zeer sterk
af-hankeiiJk is van de betrouwbaarheid en :g,edetaill.eerdheid' van des.tatistische. gol finformatie van het betrokken vaargebied.... . .
De inze.tbaarheid van de modellen is bepaald door de maximaal toela'atbare golf-hoogte als functie van' de golfperiode bepaald op basis van optredende ver-snellingen getoetst aan hetgestelde versneil'ingscriterium, te projecteren op
het gekozen .golfmili'eu.
Een voorbeeld hiervan is gegeven in. d "Wave scatter-diagrammen" als. getoond in de figuren 8, 9 en .10.
DUidel ijk is te zien de invioed van, de scheepssneliheid en de scheepsiengte
op het inzetbaarhei'dspercentge.
Daarnaast dient te worden gesteid dat de verkregen inzetbaarheidswaarden
voor-al'snog moeten worden gezien: als .een goede maat voor onderl inge vergeii.jkir'g
van de scheepsmodelien.
4.2. Methodiek
0m voor een bepaald vaargebied de inzetbaarheid van eefl schip te kunnen be-pal en dient het percentage of promillage 'voorkornen per tijdseenheid van de significante-gol fhbogten per karakteristieke periode bekend te zi in.
In fig. 8 en 9 is dit in de vorm van een wave scatter diagram weergegeven
v.00r resp... het kustgebi.ed t.p.v. :het meetpunt Goeree, ca. 10 mijl uit de kust (bron Rijkswatersta'at Deitadienst) en het midder. van de Noordzeef 7j als promiîi.age voorkomen per jaar van de significante goifhoogten opilopend met
0.5 m op basis van de gemiddeide nuidoorgangs-goif-periode 12. Zie voor het
rni:dden van de Noordzee "area 4" fn fig. 7 uit
[7:J
Indien voor de verschiliende ,sneìhedefl de. verticale versneiling per eenheid van significante gol fhoogte berêkend i s. voor de te beschouwen, lokatie kan
per nuldoorgangsperiode de 9ptredende verticale versneiiingen voor de diverse
voorkomende s igni:ficante goil fhoagten. bepaai:d worden door vermenig.vuldig,i ng
met deze golfhoogte.
Uitgaande van een aangenomen versneliingscriterium voor de beschouwde .1okatie kan nu v.astgesteld worden bij welke significante. golfhoogte dit criterium wordt overschreden,. Op deze wijze kan voor elke snel,heid door een iijn de
grens worden aangegeven waarondèr het gestelde .criLterium niet wo.rdt over schreden. Zie als voorbeéid fig. 8 en. 9.
Door sommatie van aile promillages onder zulk een g.rens}ijn kan het percen-tage.inzetbaarheid gevondenwo.rden. Voor bepaalde promlilages in het
grens-gebied is interpol atie toegepast.. Eén .voorbeél.d orn met behul p van een
corn-puterprogramma de inzetbaarheid te. bepalen ais de verticale versnellingen: be-kend zijn is gegeven in tabel no 4 en 5 voor elk van de beide versneili'ngs.-criteria.
5. 'Onderzoek
'5.1. Cohditïe's' . ' .
De berekeningen van de response fûflctTies n het gedrag 'fl: onregelmatige
golven zijn voor de modélien i tIm 15 als aangegeven in figuur 1, 2, 3 en, .4
uitgeoerd met het computerprogramma "TRIAL" [8] van het Laboratorium voor
Scheepshydrornechanica. (TH-Deift').
Hi.erbij is gebruik, gemaakt van de strip.theorie weike voor de absoii.ite verti-cale bewegingen aanvaardbare resultaten geeft voor dit .scheepsype en 'bi:j
snelheden zoal s aangetoond is in [ 9] .
De volgende condities zijn beschouwd:
1. 6 snelhedenn.I. V = 15.5, 1'9.4, '20.0, 23.7', 25.0 en 29.6 knopen Waarifl beg'repeñ 'Eh = 0.657 en En =0.821 voTgens onderstaandel tabel.
Langsscheepse massatraagheidsstraal k, = 0.25 L
Uit berekening is gebleken dat deze coëfficiënt 00k voor rel'ati:ef kleine
schepen toe te passen is.
' q V in knopen . . . a L rn En = 0.657 Fn = 0.821 15 15.5 ' ' 19.4 25 20.0. 25.0 35 .23.7 29.6
2. Voorinkomende golven d:.w..z. gol.fric'htingshoek a = 18O.
3. Golfiengte-scheepsiengte verhoudingen: aantai' 35
AIL 100, 50, 30, .20, 16, 12, iO, 8, 6,' 5.5., 5.0, 4.8, 4.6, 4.4, 4.2, 4.0, 3.8, 3.6, 3.4, :3.2, 3.0, 2..8, 2.6,. 2.4., .2.2,, 2.0, 1.8., 0.2..; 1.6., 1.4, 1.2,. 1.0., 0.8, 0.6, 0.4,
ii Pierson-Moskowitz goifspectra met significante gpifhoogte H1,3 ='.
1 m.en de. volgende nuldoorgang,speriodén ii:
2, 3, 4,
5:, 6, 7, 8, 9, 10,,
1.1, 12;Voor aile 20 ordi1naten Z:fl voor elk .goTfspectrurn bepaald:
i. de significante absollute, verttcaiie beweging
2., de significante verticale versneiling
i/3
dé significante rei atieve bewegiing..
de significante golfhoogten H113, die overeenkomen met de vo'l.gende versnei'iingen a1,3,:
0.30 g, 0.35 g, 0:..4b g, 0.45 g, 0.50. g, 0.55 g, 0.60
g,'0.65 g,, 0.70 g;
Daarna is met de methode, als aangegeven onder 4.2 de inzetbaarheid voor
el k van de 15 beschouwde modellen 'bepaald voor zowel het kustgebied 10
miji uit dé kust bij Goeree als het mid'den Van de Noòrdzee met betrekking
tot d'e voigende sneTheden:
Hierbij '.zijn versneiliingscriteria gehanteerd als aangegeven in hfdst,. 3 d.'w.z.:
a1,3 t.p.v. midscheeps (ord. 10)
0.35 gen p 0.05 L achter VLL(ord. 19) 0.5 g
Ilierbij 'kan opgemerkt worden dat 5,% achter VLL,(ord. 20)' g,l:obaal overeenkomt
t. = 15: m y = 15,5 , 19.4. 25 knopen Fn = 0.65.7 Fn = 0.821 L = 25 m V 20.0 25. Q 29.6 knopen Fn = 0.657 ' Fn = 0.821 L = 35 m V = 20..0 23..7 29.6 } ,knopen Fn = 0.657 Fn. := 0.821.
5.2. 'Presentatie resu I taten
De percentages inzetbaarheid .z.ijn voor het kustgebied en midden van de Noordzee met betrek:king tot de h.iervoor genoemde sneiheden als voigt gepresenteerd:
a113 op ord 10 0.35 g
L = 15 m op basis van de breedte voor de. modellen no 1, 2 èn 3
in figuu'r no il
L '= 25 m idem voor de modellen no 6, 7 en 8 in figuur no 12
3. L = 35 m idem voor de modellen no 1, 12 en 13. in figuur no 13
L = 15 m op basis van de diepgarig voór de modeiien:no 4,, 2 én. 5
in figuur no 14. .
5.. L = 25' rn idem voor de modellen no 9', 7 en 10. in figuur no 15.
6 iL. = 35: rn i.dem«voor de modellen no 14, 12 en .15 liA; figuur. no16.
7. op basi!s van de scheepsiengte voor Fn '= 0.65.7 en Fn = 0.821 in
figuur no 17 uitgaande van de modellen 2., 7 en .12.
a1,3 op ord. 19 0.5 g
op basis van de breedte voor de model Ten no 1, 2 en 3
in fi.guur no 18 :
idem voor de modellen no 6, 7 en 8 in figuür no 19
idem voor de modellen no 11,, 12 en 13 in figuûr no 20
'op basis van de diepgang voor demodeilen no 4, 2 en 5
in fi'guur 'no' 21 8. L = 15 rn
9. L = 25 .m
i0 L = 35 rn
L = .25 rn
idem voor de modellen no 9, 7 en 10 in figuur no 22
L 35 rn idern. v.00r de modelièn no 14, 12 en 15 in fi.guur no. 23
op basis van de schee,pslengte voor Fn = 0.657, Fn = 0.821 en V = 20 kn in fi:guur no 24 u.itgaande van dé modellen no 2 7 en 12
In figuu:r no 8 is voorhet kustgebjed en in figuur nO 9 VOO:r het rni'dden van de Noordzee als voorbeeid in een zgn. uwa,ve scatter" diagram met ]ijnen voor
de verschi'llende snei:hedew de grens aangegevenì voor de i,nzetbaarheidt in het
geval van model no 1. . .
In figuur no 10 z.ijn deze grenzen aangegeven voor het kustgebied met
betrek-king to.t de 3 beschouwde. scheepsliengten voor het geval de snel heid 20 knopen bedraagt.
De daarvoor benodi gde 'computerberekeningen n voor de eerste twee geval ien
als voörbeeld gepresenteerd in tabe.l no 4 en 5.
Tenslotte zijn in de figure.n no 25, 26:en .27 .de verticaie versnellingsamp'iituden
voor 1 rn golfamplitude op basis van de gol'fperiode gepresenteérd voor elk van
de basismode;lien van L = 15, 25 en 35 m metbetrekking to.t. de aangegeven snèl-heden, terwij1 figuur no 28 :deze parameter weergeeft voor de 3 basisrnodeT1en met betrekkin tot een .sn'elheid van.20 knopen.
In deze figuren is ookaangegevendLm.v. een dikke streep waar de meest voor-komende nuidoorgangsperiode 12 voor het kustgebied ligt n o 1. 12 = 3.5' sec. en voòr thet midden van de Noordzee n .1. T2 = 6.5 sec.
breedte vartatie
Voor kustgebied 'geringe to,éname van inzetbaarhejdL = 15: m ' (±7%
p .n'. )'
Fig'.
l8
'Voormidden Noo'rdzee vooral toename voor V = 20 kialS B' 3.764.13 m met ±27% 'p.m.
'enVoor 'V = 15 kn toename v'an ±28% p.m. als B =' 3:.39+3..76 m.
L 25 rn toename voora]: op rniddén Nöòrdzee voor alle sneTheden
:Fig. 19 met ±11% p.m.
L 35 m toèname voorail 'ap' mddén Noordzee 'voor ai le snel heden
Fig:. 20 met ±6% p.m.
dtepgang-variade wetnig invloed van de' diepgang,; soms toename; vrij sterk
L = voor het midden van de Noordzee met '50% p.m:. als
Fig. '21
1 =0.901.00 rn.
L = 25 m weinig i:nvloed van de diepgang; alleen tameli'jk' stetke
F;jg. tôenañïe vah ±25%' p.m. vobr V ' 29.6 kn op :IIét rntddefl'
van de Nôordzee als T = 1.50 1.70 m.
lengte variatie
op basis vanj Fn toename v'an de' inzetbaarhèid met dFig. 17
lengte vooral tri het kusgebied.
Voor rni:dden Noordzee toename met± 0.6% p.mo
snelheidsihvloed toename van de tnzetba'arheid ais de snelheid afneem't.
Fig'. il-17
Dit, effect is voor het midden van de :Noordzee meestalveel groter
an voor het kustgebied; voor' L = 15en 35 m ils dit ongeveer een factór 3.
Voor het kustgebied is de sne1heidsinvioed verwaar-loosbaar voor L = 15 en, 35 m, maar voor L = 25 m
t-s de toename ±20% als de snelhetd a'neemt, van Fn =
0.8210.657.
Voor de hoogste sneiheid ts d toename ±1.8% p.m.
als, L =i535 rn en voor de laagste
snei;heid (Fn = 0.657)i's de toename ±1.4% p.m. als L = 1525 m.
