Measurement of hydrodynamic pressures on two-dimensional ship models heaving and rolling with large amplitudes

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_{Technische Hogescho6r}

Measurement of Hydrodynamic Pressures on Two-Dimtonal Ship Models Heaving and Rolling with Large Arnplitude#

ByKunio

GODA*

Takeshi MIYAMOTO

1. Introduction

Hydrodynamio pressures on two-dimensional ship models were

measured by a forced oscillation test with large amplitude in a

free surface. Main purposes of the test are as follows:

To investigate effect of shipping water on the deck upon the hydrodynamic pressures on the hull surface.

To investigate effect of the bilge keel upon the hydrodyna-mic pressures on the hull surface.

To investigate pressures on the deck due to shipping water.

2. Forced oscillation test

The models used in the test were the cylinder of the square

station 81/2 cross section and the cylinder of the square station 5 (midship) cross section of the ore carrier "KASAGISAN MARTJ". Principal particulars of models and the ship are shown in Table 1. Cross seebions of the models are shown in Fig. 1.

The model of S.S.8'/2*as used for the forced heaving test and the model of 5.5.5 for the rolling test.. The test was carried out in still water of the experimental tank shown in Fig.2.

Mode of oscillation was simple harmonic motion. Mean position of

oscillation was upright position at load draught. In rolling

test axis of rolling through point 0 shown in Fig.1 was fixed in space.

For the purpose (1) previously mentioned, the models were tested

under two kinds of condition. One was the model with the

free-board corresponding to the prototype in which water was -allowed

to ruii over the deck. The other was the model of which sides

were extended upward sufficiently to. prevent water from being

shipped. Besides, for the purpose (2) the model for rolling test

was tested in four conditions; condition I, II, III, and IV as sho-rn in remark of Table 2(b).

Amplitudes and periods of forced oscillation are shown in Table 2.

In Table 2(a), f denotes the freeboard. Period of free rolling

motion of the prototype ship "KASAGISAN MARU" is 11.0 sec.

accor-ding to calculation by Fukuda. Locations of pressure measurement

are shown in Fig.1. In the figures

₉

is angular co-ordinate of

the corresponding Lewis form.

Ship Structure Division, Ship Research Institute, Tokyo, Japan.

This is a summary of paper presented at the 49th Meeting,

November, 1.974, of the West Japan Society of Naval Architects. ** S.S. is abbreviation of Square Station.

# Summarized from the paper (in Japanese) published in

Transac-tions of the West-Japan Society of Naval Architects, No. 49, February 1975.

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In Fig.3 through Fig.11 typical test results are shown; effect of shipping water upon the hydrodynarnic pressures onthe hull are shown in Fig.3 through Fig.6; effect of the bilge keel are shown in Fig.5 through Pig.9; the pressures on the deck due to shipping water are shown in Pig.1O and. Fig.i1.

In the figures, calculatiOns shown together with test results are

ones carried out by tJrsellTasai method. And "critical" means

state in which the relative water elevation on ship side attain just top of the freeboard.

Conclusion

It may be concluded from these test results:

Difference of the hydrodynamic pressure amplitudes and phase angles between cases of "without extended freeboard" and "with extended. freeboard" is slight.

Effect of the bilge keel is remarkable on the phase angles

of the hydrodynamic pressure to rolling motion. In the

case of "without bilge keel" there is little phase diffe-rence between the hydrodynamic pressures on every position

and rolling motion. However, in the case of "with bilge

keel" there.is a certain amount of phase difference between the hydrodynamic pressure on the side and on the bottom. Peak values of pressure on the deck due to shipping water

are aLiiost equal to the experimental values of

_{9o°)- ff}

where

,f?,(9=o')is

the hydrodynamic pressure amplitude on

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Table. 1

Principal particulars

8%e,tI0flI woo.

Table 2

Test programme

(a) Heaving

(b) Rolling

.J I.-,? 1144.1 (Zn. (4*7) (7 ran. 11471 (1401

;,

.: 0.O:.10 C-'l00r00 o

T17ioe:Fo :..

03750

oIo:T.io:.To:.f,...,

UI 0 o. 40 1.1004 (1474 Deal (24.4 (144 .4224 (7.14 0 S.S.81/2

o o:.Ia .o.Io. _i°

i S.S.5

j

1

aEcEn:

FRFFB9RO I PRO. PR(1 i PR PR I PR 2 Pa LW.L Pa 3 PR 6 Pa 7

ITEMS SHIP I2-01ME?CONAL MODEL S.S.8V2 LI #13TH. L 247.00014 0.995 m

m 0.995 LOCAl. 8EM'.l (SES)

8 (5581/2) 40.600 mI:J397 39.460141 0.4027 14 LC.PTI. 0 23.000mL_O.4u90 m 16.000 O.25 m 0.2347 m 0.46334. OTAUGHT. I I.269_ Ei.9975 1.233 0.9760 aLGE XEEL 8REAOTH 0.425141 0.0077 I1 LENGTH 62.320 m FROM 0 FORE 38.32010 FROM 6 AFT 24.000m

SCALE RATIO. I/a 1/54.889 4/98100

.ico .fla aL II.al (444.3

fl. IflflS (Ofle flflE1SO

o

UIUDI

,Jfli]50, 0 C. C C. 0C. C. OC C.C. C.C. C.C. C. C. C.... o o o o 0 0 o 0 0 0 0 0 0 ornoDD9Do 00 o90 0 OO 00

oUmUoIU

_{000 0 0 0 0}

clool

_{O00 0 0}

0 0 0 0 00 0 00 0

-4 'EJ'14n14fl

0 0:0 o:.le.s 14

0 o:s a So ro.5 0

0 0S 0.

PRO PRII PRO PR9 PR8

Fig.1

Cross sections of models and locations

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a14 C a '2 'I 10 8 4 2 6 OL 0 0 -14-: a 12 I J0 6 4 g

Pig.2 Experimental tank

$.S 8V2 e'90 (P115) I I.0cc.(W4IP) 1.111i.c.(L4CIJ HEAVING AITLICE Z. 4 4 6 PERIOO : 11.0 X.c.ISI4IP) l.Iuluc4MOCQ.) * 0 amplitude in heaving 0 Cc) 40 rN o 1b 12 1012 HEAVING AMPIJTtICE 0 0 S.S.81i2

0.50' (PHO) _Fig.3 Hydrodynamic pressure motion, effect of shipping water £ 14 6au T8?Ijr CCIEJ FXI(AORD : CN.TIcA1.

I

V 6 4 0 6 4

:tv

&o. P00: I I.Osec (SHiP) I.IIIseC CM0_) HEAVE AMP.: 4/3f o WITHOUT EXTENDED FREEBOARD

WITH EXTENDED FWCbOAx0

0

60' 90'

0-Pig.4 Phase angle of

hydrodynamic pressure to heaving motion, effect of shipping water S.S8V2 G'7G' (Pu7) PCWO0 lIO,IC.(SHIP) : 1.111 .Ie.LMOL) WT1T CXIUD1 P4EfOARD I: 4 6 0 10 12 14 6cm 4 6 6 I

QI

16.

IAVBG AIJfl SHIP

IWLATNE . WThBJT EXIE.D FREEbOARD WAlER WTR ELEVATON FREEbOARD .YcmOOThAVE

SSLWA 4.WTR ERIE1_FRpoIRD

: CRITICAl.

0 2 4 6 8 0 12

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r S.S.5 e.906P841 P1.1800: I l.Os.c. I I.485.c.C800CI..) a 0 0 10 20 ROLLING AIUTUOC (01.0.) (a) S.S. 5 .4O (Pe)

PERD: IIJO..c. (SHIP)

1.485 ..c.(UOOEIJ

Cc)

10' 20'

ROLLING AMPUTUDE . #. (0(0.)

PUlleD I I.Ol R.i. M *. 24

I. 485..(MOO(IJ r1wITN?TrPC T PD1fi,? I r1.!

ic r

8I18.c _11.0._J 40 60' 70' 83' 90' 6! at I0

Pig.6 Phase angle of hydrodyiiamic

prcssure to rolling motion, effect of shipping water

s.s.5

-O'60'(PRTJ

PCRIOO: 11.0 sec.(SWP)

I.4e5.,c.cIIOCEL)

10' 20'

RGU.ING MlPU1CC fs (O1.GJ

(b)

ss.5 e'20' (PR9) P1.RIO0 : ul.Oi.c.(SHIP) 1.485 ,.c. (uO0L) 0' IC' _20'

ROLLING MLfl.CE. . (DEG.) Cd)

V £

30'

-30

Fig.5 Hydrodynamic pressure crnplitude in

rolling motion, effect of shipping water and bilge keel

.

p.

10

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in at LAbO IE 40° (a)

(C)

PERIOD I I.Osec.(SHIP) 1.485 se.(MODEL) ROLL AMP. 4. 20c

- WITHOUT BILGE I(EEL

WITH BILGE KEEL

S.S. 5 60° PERIOD I I.Osec.(SHIP) L48Ssec.(MODEL) ROLL AMR 4..20 ffiCO : 0.0 .c.(5..PJ I

Fig.7 Phase angle of hydrodynamic

pressure to rolling motion,

o 70 effect of bilge keel

WITH BILGE KEEl

wcA1II

.rr.r xrn

(b)

Fig.8 Vector diagram of hydrodyiiarnic pressure

on bilge part, effect of bilge keel

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is rolling motion, _4' a.gular velocity.)

Fig.9 Simulianeous distribution of hydrodynamic

pressure, effect of bilg& keel

(Shaded part shows effect of bilge keel.)

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MODIOL 212mAq 10 MccCL (0 3 I4 0 I70..c (SHIP)

PERIOD _{p 7I7s1c (IODJ}

-P. P..__ _{- _&___}çOF

r i o-,-,. wrT,.iOuT EXTEICED

/

I 'REEBOARO

P.(09OpgI WITH XTEt,CEO

4 FPELOOARO 2 4 6 8 (0 12 IEAV9G TL Z. (a) 0 2 4 6- 8 ID 1AVINQ AMPUfl.CC z. (c) s.s.5 PERIOD: 11.0 g.c. (SHIP) 1.405 s.c.(MOOft) 20

RCUING AMPLITLGC . . (DEG.)

:

cLcu.ATION: PERIOD 9.0 ..c. (SHIP) 0.909 sic. (MCCCL) P. OF ...p S P. OF P.i CF P-s

R

P.(G.9Digf WITNDJt EiTOFPECUOARO P.(090pqf; WITH EXTEtIOED FE90ARD I.. / .

/

.1/

6 8 10 '2

I

_pry's (4 16an

Fig.11 Peak pressure on deck

due to shiDring water in roiling motion 2 0 9.5p l2 0 11.0 .,. (SHIP) PERIOD : 1.111 src. (MODEL) P.(e9OFpjThiTAi2iOEQ flEOOARO

Ps(G9O)-pgf 4I1W E1EM..D FREEBOARD cALcULAnON:

/

/0

4 6 8 (0 )AV8IG A.JTLCE Z.

(b)

Fig.1O Peak pressure oil deck due to shipping water in heaving motion

(p,ce"to°) is the hydroclynamic

pressure amplitude on the

point Pis .. See P-ig.1.

f is density of water, acceleration of gravity.) LzcRo.u.

4/

(4 lEan .SHIP (4 (Gm 0--- Ps P, F. P. OF OF OF OF P1.0 P...s P..4 P.... (0 8 3 6 4 2 r I0 ₀ 12 (4 1G's