Preliminary estimation of some ship manoeuvring characteristics on the basis of systematic model tests

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HMCC 'e3

_{SMSSH 83}

12-bER H8Y-EHO - MeT000norMYeckMR

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- 19. - 23. ceHTRÖpR 1983

12-1H SCIENTIFIC AND _{METHODOLOGICAL SEMINAR ON SHIP}

HYDRODYNAMICS VARNA, BULGARIA

_{- SEPTEMBER 19. - 23. 1983}

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PROCEEDINGS VOLUME

OF SHIPS

MARINE STRUCTI

PeDakTop

_{CT,H,C, nA. 5OFO2HOB,}

3acJlykeHHbIR OeRTeJm _TeXHL4kII EDITOR IN CHIEF _{DR, PA. BOGDANOV, HONOURED SCIENTIST}

irc

E3SHC

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PBLIMIJARY ETIMATIO 0F SORE SHIP

_{JJOJVRIJG dHARAcTI2TI}

OS THE BASIS OP SYSTEMATIC MODEL TESTS E. Milanov, M. Lefta.rova, Tz. _Stanev

(us of

ths methods for _obtaining structural exprenniona for tb. dependency

Of ship's manosuvring chrecteristica as a

function cf hull main dimenuions _and _the

operationaJ. parano ters of the control de-vices, is the regression analysIs of elpe-rimentul date of systematic model tests.It

is necessary for the purpose, to choose

properly the combinations of _Indesibent

variables, to draw a plan for their varia-tions and finally, to have adequate number

of nLrew8nts for the basic

characteris-tíos.

The present report s.ake8 an attempt

on the bases of accumulated _experimental

data from systematic tests with

free-ran-ni ship models at BSHC, to give

expres-sions allowIng exprass evaluation of tha

basic indIces of Ship'S ourvilinear motion:

the non-dimensional dIameter

D-

and

the non-dimennional linear veiocttyV

-at steady turn.

Z. CHOICE Q?

I.NPEDES

VJ'RIASIj.EO'

ÇITIO

Iiortant step when obtaining the

structural expressions descrIbing the

in-vesttgated dependences, is the ahojo. of

these independent variables which _cause

eons idol-able inílusnce on the manceuvring

ualit1ea of the ship. This analysis is

based on the following main aasumptions[1 - In. ship steering at first approximation, the positional and rotary derivatives _and ths resulting manoeavrabllity characteris-tics appear linear functions of aspect

ra-tio of flat plate, equivalent to bull;

- Ship's steering is strongly _influenced

by hull fullness;

- The presence of developed deadwood at

stern causes considerable stabIlizing

of-feat. The formation of deadwood _{at etrn,}

is connectad with transformation from

J-to V-shaped form of the frame _sections; - A certaln influence cf the centre of ou-oyancy on ship's steering, is supposed. _to exist as well.

On the basis of the above-atzted

as-sumptions, the following set of

indepen-dent variables is chosen:

A

_i-V

_X0

5

J where:

21

-- -

aspect ratio of flat plate equivalent to hull princi-pal plane of symmetry; - Block coefficient;

- Number of the rrume from

which the tranformaton

from U-

o V-8beped

section

begins;

- Non-dimensional abscissa aT the centre of buoyancy; - angle of rudSer deflection.

3. LLN

_{RISTICS OF TH}

TESTE.D MODELS

The experimental test results from a basic aeri.s of free-running models

char-actorized by high values of the block

co-efficient

C,

are being proceesad. These

resulta aro supplemented oy data of

ana-loous individuai, teats for four _2odels, whose characteristics arc within the

gao-nstry of the basic series. The

_wldend

series thus received, consisting _of 10

nodels are characterized bd th. following set of inequalities: 0.113 -s _{A -} _0.135 0.71.8

C8081i

0001.5

XÇ 0.031

1 _¡u-v ₄ _350 . .

35°

08 'U-v

xc

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1l modele are eingle-ecr.w with c1ocwime

rotation.

hTJL IIT ÁhD

VU.P2

O.?

QB-The development of the triematica].

mciela describing the dependoncee:

SD-f(C.?.xc

HUV.R)

V -f(CB

. XC. U-V' R) (4.1)

is realized with the linear _regression

analyCiO method.

or this parpoee, the arproximation

depandences of the nodimennional turn

diameter and linear speed on the rudder

angle, ar initially obtained in the forza:

S-cA+a25R+a3

(4.2)

2R

>2

The coefficients O and obtained,

are reprementod in th. form of secozid dog-ree polynomials as a function OX' the

re-aini.r.g

independent

vriablee:

1. 1. 01(C .X )

Co s L C

X1< X j-1 <j-1 (4.3)

d,x)-do+

_dx+

dkiXkXi j-1 k,j-1 1k<))

The vector for the co.fficicnte C

i

-

Ci

_(xTX) XT

_(4,4)

C3

and analogous or't

The adeuateneae of equations (4.2)

and (4.3) for the obtained vectors C

andO

is establiahed on the oasis of the

inequa-lity reeuJ.ting from the usage of yisher

crttcrion

F:

F>F1(0.k1 k2)

(4.5)

where:

F - actual valuo of the criterion:

F-

R2(N-k)

₍₄₆₎

(1-R2)(k-1)

R -

multiple correlation coefficisct;

N -

number of ziessureziente for each

characterie tics;

k-

number of coefficients in the

equations;

FT- tabulated value of the

coeffici-so l:vel of significance;

k1-N-1

k2-N-k

5. REJLT$

After processing of the experimental

data following the above-descibed way,

for the ship's zianceuvring tudicos the

following structural expressions are

re-ceived:

D-a1

+Q32

(4.7)

c -Cj s .

c

+ C2 k k .k (Ak) +C23

_{A su-v}

_:

_(4.8)

Qj-00

Ci C + C23Ak+ C3 ''u-v k k +C12Jc (Ak + C3 CB _{. EU-V} V .2 (410) + d1 Ak + d2 . -v d3 + d Ak HI.VI 's- d13 X' where:

- the symbols,S' _{and ,,F} _refer _to

the values of the quantities at _e:arboard

(O>O)

and portboard (R<° turn respectively;

- the index

k'

_{denotes YaluOa} _of

the indsoendeut variables, calculated by

the formulae:

0k

_°B°7875

0.0235

Ak

A-01240

0.0110 (4.12)

.k

_i-2,75

1.25

s a result of the analySis, the

va-rlablo _{is excluded from the set of}

an-dependent variables due to ita ineign.ifi-cant in.flaence on the investigated charac-tena tics.

'l'ne values of coefficients C and d in equations (4.b), (4.9) and (4.11), are gi-ves in Table 1

Figures 1 _{to 4 represent in graphical}

form the approximations obtained by

for-mu.lae (4.7) + (4.21), compared with the

baaic experimental data. The results are

satisfactory - the m.x1mum relative _error being, for SD'clO% and 17<7%, which is a good validity of the obtained rogressional

expreso ions.

I. Sobolev B.V., 'Ship Steer:ng and

Automation of Handling', Sdostroenie,

Le-nIngrad, 1976.

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g 11 -30 -20 - 10 -30 -20 -10 SD L SD

Fi.1

20 -°]

N9 H 6[01 0 10 20

_[O]

-20 -10 SD L

Fig. 2

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NIV

iii

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Sa L

g-MODEL N91 5

20 ä[°]

-30 -20 -10 o SD L O 10 -30 -20 -10 -30 -20 -10 10 _{20 ___} 10 20

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-30 -20 -10 0 10 20 V 1.0 V NQIV

- [o]

-30 -20 -10 0 10

20 []

-30 -20 -10 0 10 20 o[°] NVI -30 -20 -10 0 10 20

5[]

1.0 V VO 1.0 a. s N V -30 -20 -10 0 10

20 ö[]

Fg.L.

-30 -20 -10 10

20 ___[oJ

-30 -20 -10 10 20

- O]

-30 -20 -10 10 20 ___[O

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