Full scale trials with MS Hollandia. Part V: A comparison of the 1978 speed and power predictions with the experimental results

TECHNISCHE HOGESCHOOL DELFT

AFDELING DER SCHEEPSBOUW- EN SCHEEPVAARTKUNDE LABORATORIUM VOORSCHEEPSHVDROMECHANICA

FULL SCALE TRIALS WITH m.v. HOLLANDIA

PART V: A COMPARISON OF THE

1978

SPEED

AND POWER PREDICTIONS WITH THE

EXPERIMENTAL RESULTS.

by: Ir. J.M.J. Journée

September

1980.

Report no. 508

Deif t University of Technology Ship HydrornechanicsLaboratory Mekelweg 2 2628CD DELFT The Netherlands PhoneO15 -786882 t

Prediction of speed, r.p.m. and power.

Comparison with experimental results.

Conch:sions. .. . . 5'. cknowiedgement. 6. References. Figures. Tables. 23

Appendix . i Prediction..of. the stili Water. r,esitance.

Appendix II : Ptedïction.Òf the wind .resi:stance'.

Appendix III: .Pre'dicibn ôf. the áddèdreitànce diie to waves;

Appendix. IV : Prediction. 'of'. thepropuas ion:characterïstics

Appendix y : R.M.S. values of the, deviations, taking. into

account the width of the wave spectrum.

i

7

i. Introduction.

At het Ship Hydromechanics Laboratory of the Deif t University of Technology a computer program has been developed to. predict speed,

power and behaviour of a ship in a seaway [i] . For each engine

setting the program calculates the speed of t'he ship, the r.p.m..

of the propeller, the delivered engine power, heave and pitch

motions, vertical acceier:ations,.the probabilities of shipping

green water forward,, slamming and racing o the propeller.

This calculation method has been used in 1978 to determine a spéed-r.p.m.-power data-base for an Operational Performance System, to be installed ,on shioboard of a containership [s]

A body plan of this ship, m.v. Hollandia owned. by the Royal

Netherlands Steamship Company, is given in figure 1. The O.P.S

project is an investigation,, financed jointly by the Netherlands

Maritime institute, Lloyds Register of Shipping and Applied Dynamics Europe. The aim of the project is to investigate the

feasibility of a computer based shipboard monitoring and pre- V..

diction system to ensure safe and economic ship operation.

During two voyages in 1979 and 1980 the Delft Ship Hydromechanics

'Laboratory assisted to this project by measuring among others the.

sea and windcondïtions [2] and the sIiip's speed, the r.p.m. of

the propeller-, the delivered engine power and the fuel consumption:

[3] , to verify the delivered data-base..

In this report a comparison is made between the 1978 prediàtions and the 1979 and 1980 experimental results. A preliminary pre-dcti,on is head waves has been given in 1978 in reference [4]

It may be noted that these predictions are. given for normalized

sea and wind conditions, at three typical loading conditions.

2. Prediction of speed., r.p.m. and power. .

The propeller, behind a ship can be considered as an energytrans-former.: torque with engine speed will be transformed into thrust

with a speed of advance of .hé propeller,. relative to the mean

velocity of the incoming water. At a constant setting of the

engine there shouldbe an equilibrium between. the egine speed

ipust be in equilibrium with the torque dêiive.red, by the engine. WIth the1 computer program ROUTE the speed-r.p.m.-power relation has been calculated from these two conditions of equil.ib'riuni:

R(VìVriOEti/3i Ï21 T) = T(V,'N,w). { i - t(V,N):]

0rne ,N). m = Q'(V,,N,.w)

in which:

R total resistance of the ship

T thrust delivered by the propeller

me torque delivered by the main engine

Q torque required by the propeller

mec'ha'n.icaì: ef:ftciêncy Of thè sha'f:t.-.bea.r.'i'ngis.

c engine setting±: V Ship. speed' N eng;ine.' sped t thrus:t' déd.uc.tionf.ractïon, wkè f±ác'tìbn. V

relative windsed

relative wind direction

11,3signific'ant wave height

T2 average zero-crossjn wave, period

dominant wav.e direction

The total resistance of the ship has been split up into three

parts:

i. The resistance in stll water.

This part of the total resistance 'haspatly been determined from the results of model experiments 'nd partly from

empiri-cal methods' given in ,lttera.ture. The predictions, for the three

'loading, conditions have been described in detail in appendix I. The resistance input data for the program are given a,t

speed intervals f 4 knos' in table I '- III. For 'intermediate

speeds a second degree Lagrange interpolatiOn procedure is

The wind resistance.

The. windresistance has been estimated in appendix II by an

empirical method; see figure II-1. in the predictions a

fixed relation between the sign'ifïcart,t wave height and the.

absolute wind speed is assumed, together with the assumption

that waves and wind have the saine direction.

Added resistance due to waves.

The relative motions of the ship. with respect to,the water

surface, caused by the waves, cause an dded resistance. The

transfer functions of the added resistance from regular waves

to irregular waves are, dependent on the wave direction, partly

based on theory and partly on experiments with a model of a very like containership.

The wave energy distribution is described by a modified. Pierson-Moskowitz spectrum with a cosiné-squared directional spreading. The significant wave height 1/3 is based on the

spectral area and the period

2 is the average zero-crossing

peri.od.

The predictions are given in appendix. III and .showzin' the

figures III-2-b, III-3-b and III-4-b.

Thrust and torque of the propeller ar estimated by using poly-nomials of the Wageñingen B-propeller series., These polypoly-nomials,

valid for open water model propellers, _{are corrected for scale}

effect and the "behind condition'!. This has been described in appendix Iv. Also. the wake fraction and the thrust deduction fraction data are discussed. in that appendix.

Sorne typical magnitudes for the different loading conditions are

given i,n table I.

in be1iaif of the Operational Performance System these _{speed, r.p.m.}

and power calculations have: been carried out at the, loading

conditions 16,9 and 19 for 'all combinations of the next range

of paraineters of ideal defined wave spectra with a

cosine-squared directional spreading: .

..

- dominant wave direction:. .

= 0(15) 180 degrees off bow . .

- significant wave height: . .

For e'acii spectrum the next magnitudes have been calculated: - the ship's speed at:

100 (-15) 25 percent of 29000 mhp

- the ship's speed at an -engine' speed of 122 r.p.m. - the engine speed at:

100 (-i5) 25'percent of 29000 mhp

- the required engine power at. an engine' speed of 122' r.p.m.

in total 72072 datahave been delivered to the data base of the Operational Performance System. For interned'ate values the sysem uses a linear interpolation procedure.

3. Comparison with experimental results'.

In the figures 2 and 3 th measured and predicted engine speed

-ship speed and engine power' ship speed relations re compared..

it may' be noted here that small deviations ar.e :present': 'between the

draughts during the-experiments and one of the'three' draughts used for the 'predictions 'in still water.

The.'pre'dicted values 'f'òr.Ioadin'g.'conditiön 1:6'..are.t'oohigh,..

especially in' the high speed' range. The'pre'dictedvalues- for

loading condition 9 are too high in the high speed range and too

low in the lower speed range.

The. figures s'how the need of c'ar'rying out experiments _{in 'still}

water at different loading conditions to get reliable predictions

for the ship in a seaway.

For the experiments in a seaway a comparison has been made between

the 1978 predicti'onsand the 1979 and. 190 _{experimental results.}

'The predicted values a'e _{'erivd f-m 'the data-base by a linear} s

interpôlation. No interpolation has been used for the loading

conditions. 'The loading conditions 9 and 16' have' been compared

with the 1979 and ì980' experimental _{results re.spectivély. The}

used wave buoy results for the different _{runs are given -in the}

figures 4-a,b,c,d,e,f,g. '

The còmparisons are shown in t'he tables _{II, III and IV in the}

- N and

me at measured V.

- V and P at measured N.

me

- V and N at measured

For the predictions of the use 'of fuel per hour the experimental

determined relation between the specific fuel consumption and the

delivered power [ 3] has been used here:

f = 0.19 + 0.0001645

me ton/hour

In tablé V the measured fuel consumption ¿ata are compared with predictions derived from the measured ship speed, engine speed

and engine power.

In these tables the absolute and relative differences are given..

The meaning of the symbol OSR ïn these tables is outside range of data-base. The Root-Mean-Squares values of these deviations during all experiments in a seaway are shown in the next table:

To get a real impression about the reliability of the predictions

it is necessary to use the most accurate measured, value as a startirg value. When not doing this the deviations are increased. by deviations of the starting, value itself. The engine speed is.

the most accurate measured value. The maximum possible deviation of the mean value of the measured engine speed is less than

0,02 r.p.m. ,

Starting from this very accurate measured engine speed the next. R.M.S. values of the deviations between the predictions and

R.M.S. tV N: P' Af kn r.p.m. mhp t/h 0 5.0 2550 0.44 0.8 0 1250 0.18 0.8 2.6 0 0.08 % %

%

O 4.3 12.0 11.6 4.6 0' 6.5 5.2 5.8 2.4 0 2.5

- fuel consumption: 5.2 percent

With regard to these R.M.S. values some rémarks have to be made with respect to the accuracy of the measurements:

i. As has been discusse6 in reference[ 3] the ship's speed through

the water is measuréd in the boundary-layer of the ship, So ship motions ±n a seaway, which wIll affect the boundary-layer, have

an1 influènce on the measured speed.

in still water it appeared in 1979 that the measured speed deri\ed from the speed indicator was about 4 percent too high.

T1-ie real accuracy of the measured speed during the 1977 triai,

upon. which corrections for the. still water resistance have been

based, is unknown.

As the predicted engine power varies with the third power of

the speed, speed- d!e,viatiors will result in relative iargepoWer.

de-vations; R.M.S. values of the deviations of Ï2 percent when starting from the measured .speed;

2.. In reference [3]. it has been estimated that. the accuracy:

of the power meásur.ementsTis. in. -the order- .of 4-5. percent. 3. No data are available .abou;t the:.açcuraôy. of the fueL meter.

Besides - this., the specific fuel consumption has been estimated in re.Ïation to the delivered engine power. This means that

rela-tive deviations of the predicted use of fuel are in the same order as deviatiQns of the predicted delivered power,

-Deviations of the prédictions for still water will increase the deviationof the predictions for the ship in a seaway. Starting from the measued speed -the deviations of the power have been corrected for this deviating still water power. Table Vi shows that the R.M.S. value décreases from 12 percent to 9 percent. The measured windspeed is about 20 percent lower than the

assumed windspeed.. This is shown in figure 5. This disagreement will cause deviations too.

Another very important factor Is the assumed ideal wave spectrum with a cosine squared spreading. in figures 4-a,b,c,d,e,f,g It

has been shown that theactual frequency dependent spectral form can differ consideràbiy from the ideal form. This is of importance

speed :

engine power:

use of fuel.:

for the accuracy of the predicted added resistance due to waves; see figure 6 and table VII. The R.M.S. value of the deviations is about 11 percent of the tätal resistance. No significant difference appears between the resuls with unidirectional

waves and the waves with a cosine-squared directional spreading

of the energy. It may be. noted that these comparisons cannot give an idea about the reliability of the, prediction method of the

added resistance. Itself. For this, calculations have to be carried

out starting from the measured spectrum. These calculations will be carried out and preseñted in a separate report.

Taking ail these factors into accunt.it has to be concluded that there is a good agreement between the predictions and the

measure-ments. . . .

.

By Lloyds Register of Shipping a somewhat different definition of the significant wave he.ight has been used for the o..s..[

s]

This other definition ii113 _{takes into account the width of the}

spectrum. When using this definition it appeared that the

R.M.S. values of the deviations hardly change, they increase à little bit. This is shown 'in appendixV.

4. Conclusions.

Starting from: the accurate measured engine speed the _{R.:M.S. values}

of the deviations between predictions and measurements are: 4.6(4.7) percent

r

'

6;5 (7.8) percent.

[iIa

_{(H113 4}

5.2 (6.5) percent

The values between the .pärentheses _{are those derived with the}

significant wave height _{which takes the width of the rave}

spectrum intó account. The results derived with the significant

wave. height _{l/3 based on' the spectralarea are somewhat better..}

Because of its simplicity this definition is adviced here. Taking into account the accuracy of the measurements the predIctions can

be classified as good..

It may be noted however, tht the experiments have not been

carried out under extremewea.ther conditions. Under _{more. extreme.}

circumstances. larger deviations can be expected..

The accuracy of this kind of predictions will mainly be dependent

5. AáknowJ.édgement.

The co-operation with Mr. A. Hancock BSc of Lloyds Register of Shipping, in particular his delivering of the interpolated values

from the 1978 data-base is very much appreciated.

6...ferences.

[1]J.M.J. Journée,

r.ediction of speed and behaviour bf a ship in a seaway, Delf't Ship Hydromechanics Laboratory,

Report no. 427, 1976.

[2]; J.M.J. Journée» and M. Bui»tenhek,

Full scale tia1s with rn.v. Hoilandia, PartI: Wave and wind measurements.,

Delft Ship Hydrome'chanic:s Laboratory,

Report No. 492, 1980.

JM.J. Journée and M. Buitenhek,

-Full scale. triais with m.v. Hoilandia,,

Part II: Speed, power and fuel consumption measurements,

Delft Ship Hydromechanics Laboratory, Report No. . 507, .,198;0.

[ jJ.M.J. Journée,

Predictions of speed and behaviour of in.v. Hollandia in,

headl seas,,

/

Deif t Ship Hydromechanics Laboratory,

Report no. 472, 1,978.

[5.] A. Hancock and K.V. Taylor,

Evaluation o.f the: operatiónal performance a.nd surveillance

system as installed on the xn.v, 'Hollandia,'

Lloyds Register of Shipping., Section Specialist Servicés,

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22éôa l2Voo 74.3êôa HL8

¿9

2a

/2/ é /J5.5i3.9 ,i.j/

foSo JV2ôo i6o

25

-Table III. Predicted and measured ship speed and power at a

fixed engine speed.

___

..

m-I

ffS.3

kn

V,ed

k/

_m/

ered.

»'

.

%

mh

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Table IV. Predicted and measuredship speed and engine speed at a fixed power.

:

#;hì

ka.

kiz.

%

jb.m.

tfrm.

/m.

Yo

I

225o

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ß #.g #3.3

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- 27 -

Table V. Predicted and measured fuel consumption.

ThI?

:

ê

éoh/hoQ pi-ed. ¿1 reo9

:roil1

&

,9

ed

.îP

.

//

%

'h

%

I

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3.55

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t/

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fa.o2J.3

5

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3.36

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3.

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69

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to.32

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398

to.of

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Table VI. Predicted and measured power including

corrections for deviating still water predictions.

m

-

_4/a

a _s -i

'-14'5o

,

-

i_

_'3350

'--

s j,

g ,

_--I

8

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2co it39oo ,'-.555o -f 50

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_{3o5o fc95a}

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_/é50

- 29 -.

Table VII. _{Predicted and measured added resistance due to}

waves. iiW?

"

r j CQ/ j (Ofl cosfr'e

-.5'Qciped

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i J? ¿0/2 to#2

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f

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Until now it has not been possible to make theoretical _calculations

of the ship's resistance in stil,i water. For the estimation of the

required power in a design state, use must be made _{of model} experiments or empirical methods given in the _literature.

The model experiments are carried out in a towing tank and the experimental results are extrapolated to full scale _{by techniques} based on physical laws and experience. The _{taccuracy of the achieved}

results is generally acceptable. During the ship's _{triaI this} pre-diction can be checked by measuring the _{ship's speed and power.}

In literature numerous empirical methods can be found to estimate the still water resistance. All these methods are based on model-experiments and trial data and are usually _{suitable for fully}

loaded ships. It may be noted that _{for high breadth-draught ratios,} as found with gas tankers and ships in ballast _{condition, these}

methods can give less accurate results.. _{Also the effect of trim}

and bulbous bows at several draughts _{cannot be accurately taken}

into account.

To predict the still water resistance of m.v. Hollandia over the

entire speed range,, _{se has been made of the results of model}

experiments, carried out at H.S.V.A.., _{and some empiricalme:thods.}

The model experiments have been carried out at three different draughts. (10.0, 9.0 and 6.1meter, _{see table I) in the high speed} range. The results are shown _{in table I-I. The next definitions}

are used here:

RV

p E 75 R C ° T ½Pv2s C 0.075 F (Lògfle-2)2 VL' dwL where: effective power '(mhp)

total resistance coefficient

frictional resïstance coefficient

still water reistarice

V speed of the ship

S _{wetted surface of the ship's hull}

Ldwi ength at desIgn waterline

P dens ity of water

1/2

-The res;istance coefficients, derived from the H.S.V.A. experiments,

are shown in the figures 1, 2 and 3' for the three loading

condi-tions.

On 22 March 1977 full scale trials were carried 'out in the Northern zone of the Gulf of Gdansk. The ship was sailirig in a ballast

condition with a mean draught of 6.1 meter with a trim of 2.6 meter.

The sea and wind were described by Beaufort 1. The speed 'has been

'measured by a radio location method. The measured data of r.p.m.

(N), speed (V) and power

me during four runs and the mean values

are given in table I-II.

The mean measured pr during the trials was 22015 mhp. By using the H.S.V.A. resistance data for the ballast condition the speed

and r.p.m. at this power 'has been calculated with program ROUTE[1].

The, calculated speed was '4.2 percent higher at a 0..4 percent lower

value of the calculated engine speed. If 10.8 percent is 'added to

the 'H.S.V.A. resistance data anda ì.0.percent lower diame'er of

the propeller (to ignore scale èffect)' Is used in the 'calculations

the calculation procedure:: gives, the required measured: ship' s speed.

and engine speed. '

These two corrections in' the cal'cu1aiohs;'de'rived 'from the _trials

in ballast condition, are maintaïned for 'the 'other loading

condi-ti,ons too, so':

R0 --- R + 10.8%

D -- D

- 1.0%

In _{hi.s way the still water resistance in the high speed range is}

known. At lower speeds an estirrat'ion hás to be made.

'For the full load condition (T = 10.0' rn) the resistance curve

m

has been estimated by two methods given ir literature:

- the method of Lap [ I-], I-2 ]

. '

- the methdd 'of Guidhammer and Harvald [I-3 j

Figure'I-1 shows the mean value of the results of these two empi-rical methods, which has been maintained in the lower speed range.

So for the fully loaded ship the piediction 'of the still water

res:istance is based on:

- co-rected results of model experiments for speeds higher than

18 knots '

or:

where:

a nod'ifiêd Adrniralty-"constant" has been used:

2. R = a. ( '7 )

'i..

R o '7FULL °FULL 2/ _SFULL a ( ..). S FULL.. FULL,

The auxiliary resistance coefficient a has partly been derived

from the H.S.V.A. results. and partly by á 'somewhat moderate inaccurate extrapolation. This. is shown in figure I-4.

The resistance curves for the 9.0 and 6.1 meter draughs, derived in this way are shown in the figures I-2 andI-3.'

In the same way, as shown for the 9.0 and 6.1 meter draughts,

predictions, can be made for the loading conditiohs 16, 9 and 19.

The values of the auxiliary resistance coefficient a has beén found by a linear interpQlàtion betweèn those of the' 9.0 arid the 10.0 or 6.1 meter draughts (see figure I-5 and table.

An assumption has to be made for fouling of,the ship's'hulI.

Mi estimation, given by Schenzie, Boese and Bl.ume:[ I_4.] is ued

here: ,

= 0'.3m +

o 6+m

20m

age of the ship in months

months since the last docking

By using this approximation the. increase of the _frictional

resistance during the winterseason 1978 _{- 1979.,will be in th'e}

order of 15 percent. This has been' included in the calculations.

Figure I-5 show _{the resistance coefficients and f Igure I-6 shows} the still water resistance for the three loading _{conditions (both}

including fouling) . The still water' resistance data, to be used as

an input in the computerprogram ROUTE, are given in table I-III.

CF

m

o

1/4

-References.

'[i-i]. A.J.W. Lap

:D±agrams for determining the resistance of single screw

ships.

International Shipbùilding Progress, Volume 1,

No. 4, 1.954.

[I_2J W.H. Auf "rn Keiler,

Extended. diagrams for d'eterminin the resistance and

required power for single screw ships,,

international Shipbuilding Progress, Volume 20,,

No. .2.25, 1973.

;[I-3] H.E. Guidhammer and Sv.Aa. ffarva'i.d

Ship resistance; effec.t of form and principal dimensions, Akademisk Forlag, Coenhagen., .1974.

P. Schenzle.,. PB.oese.an,d .P..B:iume.,

Ein .Piogramm"System.:.zur. 'B.erechungder Schiffsgeschw±n'dig-kei.t. unter.Dienstbed'i'ngun'qen.,

Institut ...fr.Schif.fbäu....der....Univer.sität.Harnburg. BerichNr'; 30s3.'1974..':

¡

OCT

3

lo C

3

2

f

Q

:

:

:

____

R

: :

RU

_

lui_ klullI:.Hll

_{RU___}

_RU

_RU

°

RU

u.

U

RU

__

RU

RU

RU

RU

RU

UU

: : : :

RU

I

U

RU

RU

RU

RU_

Q

Io

Lo

(kn)

Figure I-1. Resistance coefficients at the 10.0 meter

4

3

oCF

3

2

I

1/6

(kn)

Figure I-2. _{Resistance coefficients at the 9.0 meter}

draught. e I I

Iri

1Î

::.::. :i

::::I:.::::::

: ...

_

:

.::.

_:i

.! :::

:: -

-.

..-. :.: -:: :

.: -

::!::::::

________

.::::.

IIL.

--- I ... : .-:

---

-.--

___s . o .--: ::: -

:;: .::

r ...::

-°!

':.: ---

: I ::_ . , I

IL

- ,- -

--.-.. i .-

::;.

i

--I L

guui

p

u

iìì

HfH:!..H.

i _.: :- ... :r

.:: ::::t.

:i:.

-

:J.::

-- .::::.1

.::::..

..z.r ----1.. :::.: -:1:: r:...:. - ... .1:::. --- : - ... I...:... .-I ..::.L :.: :.:;::: : r --- - --- .---

.:::

.-.

.::

Q

_io

2

I

Q

Q

(kn)

_V

Figure I-3. _{Resistance coefficients at the 6.1 meter}

draught.

±

i

H:

.:

. : : .

::

: II

I:i

.

l

:H :: :

--_i_

aa

H : t, H -' 1 : _: '

:

i

:i :

. :::-:- '

::f:

___i

--:

:-

.

:j: W:---::

0

_O

u

::

!1I!_: í

Ì

«:

;i: : ::::

::,

;

'i:

:L I :' iii:: r :. ±

.-r - :L:r::: - ---.-r:. I -4 -1 I J -i--r:: ::: r:: :::: : I L: I -I IOCT i c?Cr

L

Q,5

o

1/8

---i

_I

! ' i: iI

::

i:

Ii!111n1

1i:

¡ii

_{._}

'u

:I!: :i:.:

:

I

I

-

-1--1

u

--

I a a

fl;i

: 1 :1 ::I

:i:!:q

i:

: : i.

-

: ' i- --

:'

o0

:.

lu

_:::::L:.. IH iH ::!:::J:: :::: :: :::::: : :L:: : -I I:: : .:.: .-: ::

J:- --:--- .--

I : -- :::,::: :----.::. --- ::::: : _____I :_ .

H- - :::::.:: :::: ; - _- ::j

:i:::

iiiiii_ii EiL:: _i

: I

-I

-i 1 -I I

:l::::;T::::.:: :::::

i:iii uRupul

-I.-__

1i

f

Q

_lo

(kn)

2oc,

(ion)

400

50

o

1 -.-.-;----I

=

I

-i

_ t . - - .1 :..

I: T

_Ii

:::

_H' Ï

:

!

HL

-

'J

_aTm812m

_J_ H I

-j

::: : I

*:

H- i:

_{:: ,::}

:::,. ::::: ::::::::

::::::::::::::: _::::I::::::: ::::

:::: ii::: :::

:::::. -

.:..:: :.:

I : :::::T

[

1:I:lTIi1

:

::::::::::

_{: :} I _i_

:::::: :

:::: :: EI :: : -

:::h::: I:H

:

_-:

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i

i:

_L

L±L

E1

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= :1:: --- :::i::: j :r_---: -- --- :: : :: 1: - : :::::::::::: :L::±: T:::

::

:::::::: --- ;::

::i

:: ::: ::::I:::: I

V

I :: o---J :: -- - -- -I- -

-i'L

:

a

lo

30

-vo

Figure I-6. Predicted still water resistance for

Table I-I. Experimental results in sti1Ïwater.

(23

2fòc

il:e

/m mp kn.

JJ6

/13

22ôS

V193

122ß5

22o/5

2V9

2x87

,2,:6:9

Table I-Ii. Available data from the ship's trial.

/9

fo5o

925o

fo5o M8O

24'o

2W

2237

2229 3.o)Y

0. 94',

0.92/

i32

2o

/2/So

2/

/525o /2550 /3 Voo. 2528

12V

ô

d

a 995 i33

22

tê6so IVioc /53oo

2ß 2!2/.

2.995 072

_fV

2

2275o l&5 1)'ìo .2 ß'o

.

5«

. o.82

ô49

/5V

21/ 235o 232oof2o5O 3o37 29V 3.009

3.qs

0.927 //oJ

25

Table I-IiI.

Predicted resistance in still water.

1/12

-\/

_Io3r

,Cinc/

/'oIIin

/j

(étn)

8/9 f68 f1.9/éJ!

/9

4'

f78 2332 fooc' Hco /ß/ 2518

2773

22

22/

7y'}/éS

319

3.27V

3.3%'ß

/5.7

J.3

¿.9

38

.15a

g«9

¿31

a.9

/5

3/

7

S

6o

_2.353

_i000

/1cc

Uoo

:

13/V

/31V

/9/

2.59t

2t78

/2

/52 2W7

255ê

/.cc6

9g

,

,y,

2

1,3V

/Vo.3

27H

3 3

a9«

t'99V

/o//

92

/2oÌ

11037

29/2

3 558

299

3378

33o

3 5/5

/c98

/33?

9%é

/Wo

iiV

1559

24'

of cargo on deck, such as containerships, the wid resistance

can be large. A reliable method for estimating the wind resistance was developed by Isherwo9d [II_i] . He has analysed the results

of wind resistance experirnen,ts _{carried out at different}

labora-tories with models coveringa wide ra'ngeof merchaht ships. He gives empirical formulae for the determinion of the two

horizon-tal .corrponents of the wind force and the wind-induced yàwing

moment on any merchant ship form for a wind from ay direction. Figure II-1 shows the wind resistance coêfficients according to

Isherwood for the three loading conditions, consideredhereof

m.v. Hollandia.

For the calculations in a seaway the following relation between the absolute windspeed and the significant _{wave height, bse on} the I.T.T.C. recommendations, has been used:

Vw = 10

1/3

with V in knots and _i in meters.

w /3

It is assumed here that the wind direction is equal _{to the dominant} wave direction.

Reference:

[1.1_i] R.M. Isherwood,

Wind resistance of merchan.t ships,

(X

.5

o

o

(Qcj.

o?g?

6)

c4

I/t7?he/-

O/ca

_CCcu/,e/

Wo

992

_L

2

.3

///

2

2

3

3

Figure II-1. _{Wind resistance, according}

11/4

cause an increase of the ship's resistance. In head to beam waves

this added resistance can be calculated with he method of

Gerrjtsma and Beukeiman [iii-i]. This method is based on the re--lation between the radiated energy of the damping waves and the

added resistance. In regulär waves this relation results into the next definition of the dimensionless tansferfunction:

a -kcosi-i L 2

-

gB2/L 2w b V dxb

where:

p density of water

g acceleration of gravity

regular wave amplitude

B breadth of thd ship

L length of the ship

k wave number

p wave direction (degrees off stern)

We frequency of encounter

b' sectional damping coefficient

Vza amplitude of the sectional vertical effective relative velocity

Xb coordinate in length

This method is used in the program ROUTE.

A close agreement is shown between theory and model experiments

in head to beam. regular waves. In quartering and following wa1ves,

however, the agreement is rather poor , probably as a result of

inaccurate values for added mass and damping at low frequencies,

For these wave directions Boese's method [III-2] ca-n be used. He calculates the added resistan6e from the water pressures on

the hull caused by the relative moLions in regular waves.

However, in 1978 this method was not inserted in the program ROUTE.

Use has beenmade of published results of experiments with a model of a very like continership [III-3]

The experimental results are given In figure III-1 for two speeds: Fn = 0.15 and Fn = 0.25. It is assumed here that the added

resistance at zero speed can beneglected. At the choosen speed HR

111/2

-values the added resistance has been found by interpûlation

and extrapolation. Because the added resistánce in quartering and following Seas is of minor importance this moderate approxi-mation can be used here. Table III-I sho»s a scheme of the

determination of the added resistance in regular waves.

The dtermination of the added resistance is based on the assumption of linearity of the ship's respons.

The added resistance varies with the wave amplitude squared. The cálculation in irregular waves is based on the superposition principie for the componnts of the wave and resistance spectra. This leads to the following formula for the calculation of the mean added resitance in a given unidirectional wave spectrum..

co

RAW = 2p g 2/L

f

I

Rwi

S (w). dw

When using a òosine-squared function for the directional spreading of the waveenergy this reìaktionwi-ii be:..

with: where: (w) A -B = exp (;;-i;-1.2 41T1/.3 2 496

andB

=

-2

if

/2

The wave energy has been,défined..'by :arì:idéai wave spectrum., a modified .Piers:on-Moskbwitz. spectrum:.

H113

T2 ₌

_{2v -}

average zero-crossing period

The spectral moments2are defined

by:

co

m

= f S(w,)

.w .dw

where:

w circular wave frequency

As the spectral values varies with the significant wave

amplitude squared t'he added resistance can be given by

RAW/Hi!3 versus T2.

The predicted added resistance' data for the three loading

conditions in a seaway without and with an assumed

cosine-squared directional spreading are shown in thç figures III-2-a,b,

4\/'

significant wave height

(w) dw}cos.2OdO

References:

[iii-i] J. Gerritsma and W. Beukelinan

Analysis of the resistance increase in waves of a

fast cargo ship,

International Shipbuilding Progress, Volume 18,

No. 217, 1972.

[III-2] P. Boese,

Eine einfache Methode zur Berechnung der Widerstands-erhöhung eines Schiffes im Seegang,

Institut für Schiffbau der tJniversitt Hamburg, Bericht Nr. 258, 1970.

[III-3] S. Nakamura,

Added resistance and propulsive performance of

ships in waves.

International Seminar on Wave Resistance, the Society of Naval Architects of Japan, 1976.

Figure III-1. Measured added resistance of a model

LIIII1IIIIH

..

:

,ff

.: lì

«:.

L.HL:ii1±4Lu

i

11111111

14'

ii

i

J!/L"

L

iii:iii : 4'j II

iT1'

iiiuiuiiiuiriíáiiiri

:

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fl

IIIIIIIIIIII II

IIIIIIUÌU

H-IUIIII!IIIIIPÌ4IIIU'

/

i

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4IiIiVdi

J0

i

.IL 411111'

L 1'

iiiiiiI iiw

m

-IIIIÍ

J i L

III1IIIIUti

-UuIih

resistance for load nr. 16. wave energy spreading)

i-III-lI

!

fi1

INIHI

1:

41!

IAiIHI

Ì

i

Ii!iIiV

J

11111

1ii_Iw/.1

L

fliUUiTiIPJi

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UI

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kJÎ1UiiI4J4

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kilUIflItlU

r

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:

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lillA

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iuiuuu

Predicted added resistance for load nr. 9. (cosine-squared wave energy spreading)

k.

110ml. :

....

.

..1lI__

.

A

b 4W

0001 uii!

m::mmmimuw

.IflhlllI_il.. li

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i

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IRRT URtI

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an Ahi. =o

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.

0

Hill

. .

fl

1111111

..

Irin

..'fl

1H 0H11H11

1K 1001kO .010111

r

u.

4. i

u.uiauuu al

il

WArf'

i !U!U! 11

I

ut

u

Predicted added resistance for lòad nr.

LE4:

CAL

LATD

r.Ñ.GERI4AEELMAÑ. METWOo

DETERM INE

FRONt XPER IME ÑTOF..FA a.:

STERM:IHE

Table III-1. _{Scheme of the determination of the. added resistance}

in regular waves.

know

. :.

. 75

45 42

1S j

ii:

Q.

F---...

F-

----F--

...F... -...

.--.---

/.--g

_F-

_{F--- F}

16--

C

-p

- F--...

F

----F---- 2e--....

'.c

F---F...

F--

F-range are usually given by the thrust constant KT and the torque constant KQ as a function of the speed ratIo J:

T

- pDn

-KQ - PD5n2 X) F a nD In these definitions:

T thrust delivered by the propeller

Q torque required by the propeller

P denity of water

D diameter of the propellér n rev/sec of the própeller

Va relative speed of advance

These characteristics depend on the number of propeller blades,2 the pitch ratio and the expanded blade are ratio and cai be, obtained by means of open-water model experiments. Results of such experiments with systematically varied propeller series can be found in various publications. One of the best known is the Wageningen B-propeller series of the N.S.M.B.[ Iv-i]

Over 120 sysiematically varied propeller models have been _tested and the results are given in polynomials, together with a

correction for scale effect. These experimental _{results are} used in the program ROUTE. The results _{are valid for the} open-water condition. For the "behind the ship condition" the torque must be divided by the relative rotative efficiency,

_which

_has

been set up at 1.045.

The speed of the water into the propeller disc _{Va is not equal}

to 'the ship's speed V:

V = V(i-w)

The wake fraction will hardly be affected by an increased loading of the propeller in a seaway. It has been determined

IV/2

-from ,modelexperiments and information given in literature in.

relation to the mean draught Tm (see table 1)

The thrust delivered by the propeil.er.T 'is not equal to tI.e ship's resistance R:

R = T(1-t

The thrust deductiQn fraction to in stili water for the ship

with a clean hull has been determined from rnodeiexperiments and information given in, literature in relation to the mean

draught Tm (see table I). This fraction, however, will decrease with increased loading of the propeller. In the bollard

pull-condition for instance this fraction will be about 0.03 to 0.05. From model experiments it appeared that, for practical purposes, it can be assumed that the thrust deduction fraction decreases

linearly with the' speed to zero at aconstant number of. revolu-tions of the propei:ier..and.an increasing:

lòadinThese.'.pr.oper-ties have:been included. in. the calculations;'.

The influence on' the efficiency of oscillations of .the...prope'i.1er: behind...:a ship. in: waves can b.e neglected fOr practical .purpos.es:.

The relation between the delivered torque of the engine and the engine speed at a constant setting and an increased loading in a seaway is also important. For preparing this typical data hase these relations are very well defined:

- starting from fixed power values the torque-engine speed

relation is of a hyperbolic type..

- starting from fixed engine speed values the torque can be calculated at this fixed value.

The mechanical efficiency of the shaft bearings

m ha's been estimated at 0.98 for these predictions.

It may be noted hOwever, that during the analyses of the fu scale experiments [3 ] it was realized that this value probably has been underestimated. During the analyses of the experimental results an efficiency of 0.99 has been asumed.

[iv-i] M.W.C. Oosterveld and P. van Oossanen,

Further computer-analysed data of the Wageningen

B-screw series,

International Shipbuilding Progress, Volume 22; No. 251,

-H113 =

4V

Taking into account the width of the spectrum the significant wave height is given by:

F

/

where:

m

= f

w. S(w). d

This definition which has been used in the

O.P.S,-requires higher accuracies in the high frequency part of the

spectrum.

From the wave measurements, given in reference [ 2] , it appeared,:

- *

Hi3

= 0.883 H1,3

In the tables V-I, V-II, v-III and V-IV a new comparison has been:

given between predictions an-d experiments for ship speèd, engine

speed, engine power and fuel consumption. In these tables the symbol OSR means outside range of data-base.

In the next table a survey is given of the R.M.S. values of the

deviations when using and _1/3

R.M.S. values ff1 (Hl/3) AV AN AP Af kn r.p.m. nthp t/h O 4.4 (5.0) 2650 (2550) 0.44 (0.44) 0.8 (0.8) 0 1550 (1250) 0.22 (0.18) 1.0 (0.8) 3.1 -(2.6) 0 0.08 -(0.O8) %

.-%_

% 0 3.9 (4.3) 13.0 (12.0) 12.3 (11.6) 4.7 (4.6) 0 7.8 ( 6.5) 6.5 ( 5.2,) 6.4 (5.8) 2.9 (2.4) 0 2.5 ( 2.5) 4V (m0 + m22/m4)

The. ra1ues between pàreheses are those, given in ciaap.ter 3.

and are based' on _'1/3

It appears thatth simple expresion of Ii1/3 givès .somewha

better result.

v/2-Table V-1. _{Predicted and measured engine speed and power at a}

fixed ship speed and with H113

k,.

,..,,,

-/

f8

_22g'

Z

1/ cl

223oo

3

/9

2185e

I

2o.o

1/ c if6

.i /2

_{,208so 2o.2oo}

_-

6so

-

_a.,

5

f

f/:4 ffß- f5

-

/3

_{2o.'5o/4e-2Oo- 9}

6 f9

/122 52

-

W

2/!o / .25

-

_-

_{/9. 8}

8

.5

-

.3co 825e L/050

11.3

a

ii.9

889

o

Boo

43.2

i9

. /2/.! ,

.ß

_{, .3.2}

o90 22Voo -/t5c

33

/9.0

1/

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-

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00 .00

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1/6.5

-

1.0

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9

_{/000 /995 -lOSo}

- LO

.35

IV /

2 OSR

_9és

3

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_{iéso ¿$R}

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i59

2/4'sû

230

56

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_{t/1.Q/o5co/25o}

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ge.:

_9.

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_{/Vo 92oo -2'o}

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59

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581 oi

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_{e55 O$R}

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65

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9

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3050 «3'OO tX25D t

.

2650 1.3.0