System series model tests in Japan concerning the propulsive performance of full ship forms

System Series Model Tests i n Japan

Concerning tlie Propulsive Performance

of F u l l Ship Forms

lead f r o m the hull form used in No. 41 Research Panel, with nearly same body plan but with a small screw aper-ture f o r supposed adaption to larger ships. The model propeller used in the systematic series model tests at the Ship Research Institute was M . P . No. 457 only and its particulars are shown in Fig. 3. As shown in Table I the model propellers used in N o . 61 Research Panel of Shipbuilding Research .Association of Japan were different f o r each model ship. One e.xample of the results summed up f r o m these systematic series model tests arc shown m F.g. 4 and Fis. 5. Fig. 4 shows the influences of length-breadth ratio L/B, breadth-draft ratio B/d and block coefficient Cn on residuary resistance coefficienl r i , f o r Froude Number of 0.18, and the followings are deduced f r o m this figure:

PRISMATiC CURVE F i g . 2 P r i s m a t i c C u r v e o f JI.S. N o . 1321 DIAMETER 211.0 BOSS .2/0 pircM /62.4 PITCH KATIO .77

fXP/INDED APE A PATIO

MAX. BLADE IVIOrHPAT/O .229 BLADE THICKNESS /fAT/0 .CJO ANOLL OF /?A/fE

/JUt^BEP Of= aLAOES Jl OIPECTIcPM OP TUpwm P/&HT HWCtD

UNIT /A/ 7»m.

F i g . 3 O u t l i n e a n d P r i n c i p a l P a r t i c u l a r s o f M . P . N o . 487

T a b l e 1 M o d e l Ships a n d P r o p e l l e r s Used I n the S y s t e m a t i c Series T e s t s of N o . 61 Re.«earch Panel .M.i5. No. * _{1725 1726 1727 1728 1729} 1730 L / B of the -Model 6.0 CO 5.75 5.75 5.5 5.5 B / d of the Model 2.7G 3.06 2,76 3.06 2,76 3.06 CB of the Model 0.80 0.80 0,80 0.80 0.80 0.80 M.S. Xo. ** _{1.Ï9.3 1661 1660 1659 1658 1657} L / B of the Model G.O 'j.o 5.7,5 5.7,5 5.3 5.5 B / d of the Model 2.76 .3.ÜG 2.76 3.06 3.76 3.06 CB of the Model 0.82 0.82 0.82 0.82 0.82 0.82 Model Prop. No. _{15C2 156.3 1564 1565 1566 1567} Dia ( m ) , D _{0.175 0.I5S 0.183 0.1G5 0.191 0.172} Pitch ( m ) , H _{0.125 0.142 0.117 Ü.135 0.109 0.128} Pitch Ratio, H / D _{0.714 0.899 0.639 (1.818 0.571 0.744}

Boss Patio, C 0.180 _{Angle of Rake}

T?.\-D. Area Ratio 0.67 Number of Blades

Mea.n Width Ratio 0.256 _{Blade Section}

Blade Thickness Ratio 0.0.50

1755 1754 1753 6.00 5.75 5.5 2.46 2.46 2.46 0.80 0.80 0.80 1701 J702 1703 0.198 0.205 0.214 0.104 0.095 0.086 0.531 0.463 0.402 1 0 ° ~ 0 ' 5 M A U Remarks S e L r i n - d t l S ' ' '

'"'''^

'^^"'^ "'^ Ship

lpp.- 6,0000m L.W.L. -6 1500m F.e 0.4851 0.242 ---- (oslOWo Ct) Cs 9 d MARKS 0.80 7.it, 1.1b 3 06' 0.82 j 2.76 1 ' 3.06

_:_

0.006 F i g . 4 E f f e c t of L / B , B / d and on r^. of N o r m a l Bow H u l l F o r m s 0.6

t

0.5 0.4 o.e 0.7 1.1 1.0

FUIL LOAD CONDITION Fn=0,I3

MARKS; -c « = o . e o C l = 0 . 8 2 I L Ce =0.804 0.82' 5.5 6.0 6,5

14

7.0 0.Ó 0.5 ^ I O.e l.l 0.7 1.0 7.5 F i g . 5 E l f e c t of L / B , B / T a n d o n S e l f - P r o p u l s i o n F a c t o r s of N o r m a l B o w H u l l F o r m s , ( B / T = 2 . 7 6 )

( 1 ) Among CB, L/B and B/d, CB is most influential and

B/d is the least.

(2) Tji has a minimum at L/B of nearly 7.3 but its i n -crease due to reduction of L/B is smaller lhan ex-pected even f o r a considerably small L/B.

( 3 ) The infiuence of B/d on r^ is not so apparent as

CB and L/B, but it seems lhat smaller r ^ is obtained

with the smaller B/d f o r the larger L/B and w i l h the larger B/d f o r the smaller L/B.

Fig. 5 shows the influences of L/B and Cj, on self-propulsion factors. The influence of B / d on self-propul-sion factors being very small i n this test range, is shown here only the values f o r B/d of 2.76. This figure shows

that the values obtained by N o . 61 Research Panel are difTerent f r o m those obtained by the other tests, making a step at 6.0 of L/B. The comparatively smaller pro-peller aperture and smaller propro-peller diameter, which re-sulted f r o m the consideration f o r their application to larger ships are considered as major reasons f o r these differences. The problem df separation was also con-sidered as having efi'ect on this large difference, but later studies have shown no marked din"erence i n separation at least f o r the range of ihese model tests. This fact seems lo be endorsed by the results f o r m in Fig. 4. This prob-lem needs further detailed studies i n general. Fig. 5 shows the following results:

(1) Wake fractions w r and thrust deduction coefficients / increase as L/B decreases.

(2) Relative rotative efficiency 17^ has a minimum at

L'B of 7.0 and decreases as L/B increases or

de-creases f r o m this value.

( 3 ) WT and t is larger and 7^ snialler for the larger

in Ihe range of the larger L/B and w is larger, t smaller and r,R remains constant for the larger CB in the range of the smaller L/B.

Since increase of rn and reduction of propulsive co-elficient 7, are small for increase of L/B, an economical .ihip f o r m is likely to be not with larger Ca but with larger B.

In the systematic series model tests of Shipbuilding Research Association of Japan not only the intluence o f ship's principal particulars on the propulsive performance but aiso other miscellaneous items were studied. The ether main results are the better performances of the prismatic curve f o r m having fine entrance at bow even with swelling fore shoulder to some extent, and of suita-ble V shape of frame lines both at fore end aft bodies, and so f o r t h .

•0.

_{Systematic series motJel tests on hull}

forms

M i t h

bulbous bow

While the effect of bulbous bow is doubtful f o r larcer

L/B and at smaller Froude Numbers, it becomes quite

remarkahle f o r smaller L/B and larger even at Froude Number which are not so large. Not only a number of

model tests after Asia-maru have shown the effectiveness of bulbous bow, but al.so the recent theoretical studies of

Prof. Maruo and Prof. Bessho have shown lhat hull f o r m with minimum wave-making resistance has sectional area at the fore perpendicular depending on speed. Therefore, nearly every f u l l ship constructed recently has bulbous or cylindrical bow.

The size of bow bulb has to be decided depending upon ship's principal particulars, speed and load condi-tion and its posicondi-tion as well has a substantial relacondi-tion with the propulsive performance. The choice of suitable hull f o r m with bulbous bow is, therefore, more difficult than that of hull f o r m with normal bow.

The Ship Research Institute has carried out systematic series tests requested by Sascbo Heavy Industries Co., Ltd. on various L/B and o f models with a bow bulb of sectional area of 4Cr of that at midship. Tbe parent f o r m was M.S. N o . 1559 and its body plan, stem and stern contours are shown in Fig. 6. its prismatic curve in Fig. 7. its particulars in Table 2, and the particulars of the model propeller in Table 3.

The most important results of the tests arc shown i n Fig. 8 and Fig. 9, which are showing the influences of

CB find L/B on and self-propulsion factors, at Froude

Number of 0.16 in the former figure and of 0.18 i n the latter, both at the f u l l load condition. The general trend is the same as in case of hull f o r m with normal bow as clearly seen in comparative representation. That is, C

I 1 ! j

; i ! .. , 1

'1.! •;_! 1 ! • • i . 1 1 • : -r-t • _{'• .'!} I A : y y . y rjSi, r ^ ' — - ! ' 5 1

F i g . 6 B o d y P l a n , Stem and S t e r n C o n t o u r s of lAI.S. N o . L5,59

- ^ £ 1 . ^ c I U ?

C , C - C K , C - - D W *

16

F i g . 7 P r i s m a t i c C u r v e o f M . S . N o . 1559

T a b l e 2 P r i n c i p a l P a r t i c u l a r s o f the Model S h i p s w i l h i';'c B u l b

M.S, No. 1559 1561 1563 1558 1520 155C 1557 1560 1562

Lrp ( m ) 6.9000 6.7000 6.5000 6,9000 6.8000 7.0Ü00 6.9000 C.7000 6.5000

7.0945 6.SS9G 0.GS27 7,0938 6.9922 7.1973 7.0935 6.85:92 6.6832

D ( m ) 1.0360 1.0512 1.0672 1,0301 1.0610 1.0160 1.0234 1.03S4 1.0044

Full Load Condition

d Cm) 0.3977 0.403G 0.4097 0.3955 0.4048 0.3901 0.3922 0.39S6 0.4043 V (mO 2.2682 2.2715 2.2733 2.2830 2.3775 2.2720 2.2741 2.2723 2.274.2 Cm=) 10.875 10.728 10.560 11.241 11.045 10.974 11.087 10.748 10 Ö7S Cn 0.798 0.799 O.SOO 0.812 0.809 0.819 0,821 0.819 0.320 CP 0.803 O.804 0.805 0.817 0.814 0.824 0.826 0.825 0.825 CM 0.994 Icb ( % o f L f v ) - 2.12 - 2 . 1 2 — 2.12 - 1 . 9 0 - 2 . 0 6 - 1 . 9 4 — 2.31 - 1 . 9 7 - 1 . 9 9 Bid 2.605 2.605. 2,605 2.605 2.621 2.60Ó 2.609 2.005 2.605 LppjB 0.660 6.374 C.091 6.098 6.409 6,890 6.742 6.452 6.165 C l o.eo 0.82 Ö.82 0.005 P ? , £ S E N T S £ R £ S U T A SR.41 S E R I E S F i g . 8 E f f e c t o f L / B a n d C/j on r n a n d S e l f -P r o p u l s i o n F a c t o r s o f B u l b o u s B o w H u l l F o r m s ( F n = 0 . 1 6 )

has a larger influence than L/B, and rp. increases and l-t and l-wr decrease as Cg increases or L/B decreases. This test, carried out only f o r B/d of 2.76, does not show the influence o f B/d. Since the hull forms with bulbous bow in Ibis series test were a little different front those with norma! bow in the series tests above mentioned strict comparison cannol be made. However, f r o m the fact

fn = O.I8 O.005 É 'd= 2.76 F i g . fl E f f e c t of L / B a n d o n a n d S e l f -P r o p u l s i o n F a c t o r s o f B u l b o u s B o w H u l l F o r m s ( F n = 0 . 1 8 )

that there is a larger difference between the both results than are not attributable to the difference in the hull forms, it may be considered lhal hull forms with bulbous bow give smaller r^, and i?;; and larger l-t than hull forms with normal bow.

The influences of Cn and L/B on the propulsive per-formance are shown in these figures f o r the hull f o r m

T a b l e 3 P r i n c i p a l P a r t i c u l a r s o f M . P . N o . 1.526

Diameter (ni) Ü.1823

Boss Ratio _0.189

Pitch Ratio (constant) _0.730

E.\pandcd Area Ratio _0.575

Blade Thickness Ratio _0.0635

Ancle of Rake _9=—58'

Number of Blades _,')

Blade Section _{M A U Type}

with bulbous bow, but in case of hull f o r m with bulbous bow there .still remain the problems o f bulb's size, shape and position. The results of the studies concernins these problems as well as optimum longitudinal position of

centre of buoyancy which is essential in relation to these are explained below.

The tests were carried out by the Ship Research I n -stitute at the request of Kawasaki Dockyard Co., Ltd. The principal particulars of the model ships used in the tests are shown in Table 4, the body plans, stem and stern contours in Fig. 10 to Fig. 13 and the particulars of niodel propellers in Table 5. M.S. Nos. 1700, 1701 and 1702 are of hull forms with normal bow f o r the study of the infltience of longitudinal position of centre of buoyancy icn. and M.S. Nos. 1703, 1704 and 1705 are of hull forms with bulbous bow for the same purpose. The influences of lm cn and self-propulsion factors for tbe hulf forms with normal bow are shown in Fig. 14 and Fig. 15. and those for the hull forms with bulbous bosv in Fig. 16 and Fig. 17. The optimum values of ICB i n

rR f o r the hull forms with normal bew can bs found only

in case o f Froude Number of 0.17 at the full load con-dition and in the other cases i n increases or decreases

T a b l e i P r i n c i p a l P a r t i c u l a r s o f the M o d e l Ships -M.S. Xo.

1700 1701 1702 1703 1704 170.3 1704A 1704C 1704B 170ij 170GA 1706B Lpp ( m ) L i i i Cm) 3 ( m ) 6.000 6.150 0.9231 Full Load Condition

d T r i m ( m ) F (ni=) _{1.4804 1.4803} S (m2) 8.127 8.1Ö3 Cfl _{0.800 0.800} Cp CM 0.808 0.808 1 CB _{of L p p ) -1.49 -2.45} Bulb Area A s * Length (7r {Vc of \ M ) of L p p ) Imniei-sion C.'J of Ai-cLr.) Ballast Condition d _{Cm) 0.1591} T r i m _{of Lrp)} r 0.6600 0.651.3 S (ni2) .5.891 5.9.3.3 0.3341 0 8.130 O.SOl I.4S17 8.159 0.801 1.4811 1.4825 1.4823 1.4832 1.4840 1,4810 1.4827 1.4855 0.809 0.809 8.197 O.SOO 0.80S 8.164 8.219 O.SOl 0.801 0.809 0.809 0.990 - 3 . 5 1 - 2 . 5 8 8.235 0.802 0.810 -2.04 8.2.50 8.216 8.236 8.269 0.803 0.800 0.801 0.802 0,811 0.808 •2.67 •2.51 0.809 0.810 - 2 . 5 6 - 2 . 6 6 0.35 about 80.0 1.2i 1.85 2.56 15.0 0..50 1.27 about 74.0 2.56 0.1588 2 0.1Ó84

• Shou-s the iinaginaiy area of the bulb at the fore eiul.

5.S96 5.913 5.9,58 5.909 5.971 5.979 5.987 5.908 5.978 5,993

i g . 10 Body P l a n , Stem and S t e m C o n t o u r s o f M . S . Nos. 1700, 1701 and 1702

as longiludinal centre o f buoyancy moves forward. On

the olher hand, optimum position"; of centre of buoyancy

arc clearly shown for llic hull forms wiih bulbous how

depending on Froude Niiinbors at the f u l l load condiiion. Further comparison between Fig. 14 and Fig. 16 shows that the optimum position of centre of biio>r.ncy for moves toward aft with the higher speed, and that oplimum position of centre of buoyancy f o r the hull forms with bulbous bow is more forward than that for the hull I'orms with normal bow. Concerning the influence of Irn on self-propulsion factors, wake fraction « t increases as ICB moves aft, but ihrust deduction coelTicient t and relative

rotative efliciency ' i ^ has no constant trend. The

varia-tion of ! and VJ! due to len I'-'"" the hull f o r m with bulbous

bow is, especially, very small.

TalMe 5 Principal Particulars of -M.P. No. 1526

Diameter (m) 0.1 S23

Boss Ratio 0.IS9

Pitch Ratio (conslunt) 0.730

E.xpnnded .•Xrca Ratio 0.575

lil.Tde Thickness Ratio 0.635

An£lc of Ratio

9'—5S-Niuiibcr of Blades 5

Blade Section M.-\U Tvpe

F i g . 11 Body P l a n , Stem and S t e r n C o n t o u r s of M.S. Nos. 1703, 1704 and 1705

F i g . 12 F^ore B o d y P l a n and Stem C o n t o u r s o f M . S . N o s . 1701,' 1704A. 1704B and 1704C

F i g . 13 F o r e Body P l a n a n d Stem C o n t o u r s of M . S . Nos. 1706, 1706A and 17068

The tesf residts on the variation of bulb's longitudinal position as shown in Fig. 12 for .M.S. No. 1704, whose assumed sectional area of the bulb. AB, at tbe bulb tip is 7.59'r of midship section area A.v. are showt) in Fig. 18 and Fig. 19, and those on Ihe variation of bulb's longitudi-nal posilion as shown in Fig. !3 f o r M.S. N o . 1706 which has the bulb of 15% in above mentioned area ratio are shown in Fig. 20 and Fig, 21, Fig, IS and Fig, 19 show

May 1966

that a protruding bow bulb gives a smaller rn in case of 7,5% bulb with the e,vc\-tion of the low speed at the f u l l load condition and bulbs not protruding so much give a s m ü l e r rji in case of ISTf bulb with the e.xception of the high speed condition. Fig, 19 and Fig'. 21 show that this difference in longitudinal position of bulb has very small influence on self-propulsion factors, and there-fore, rn may be considered in direct relation with D H P .

R - U I O A 3 B A I L A S T M A S K S ; F U I . L O A D BAOAST - 2 , 3 1.1 i-.- O f L M ) F i g . 14 E f f e c t of on m o f N o r m a l B o w H u l l F o r m s o.oos,. 0.00 j L - 2 J l . i Ci C f I p p ) F i g . 16 E f f e c t of IcB on r « o f B u l b o u s B o w H u l l F o r m s F i g . 1.5 E f f e c t o f \VB on S e l f -Propul.sion F a c t o r s o f N o r m a l Bow H u l l F o r m s -2.5 F i g . 17 E f f e c t of len on S e l f -P r o p u l s i o n F a c t o r s o f B u l b o u s Bow H u l l F o r m s

M A S K S ' -M 1 0A D ï* a A 5 T F i g . 18 E f f e c t nf L o n g i t u d i n a l P o s i t i o n of lJulb on ï j i , ( A f l / A , , = 7..5%) ;L 0.005 M A t K S , F U U 1.OA0 B A l l A S t fVi = 0 . ; 0 ' A p p O f IPO) F i g . 2 0 E f f e c t of L o n g i t u d i n a l P o s i t i o n of B u l b on m, (A/i/A_,/ = 1 5 7 ' - ) flAL I O A : » • « A l l A S T

1

1 i

1

1 F" = c n r F i g . 19 E f f e c t of L o n g i t u d i n a l P o s i t i o n of B u l b o n S s l f - P r o p u l s i o n ( A j 5/ A . v = 7 . 5 % ) 0 . Ï C fc _ 0 ? OB -0 6 p 0 5 L f l A l IOAÜ i A l L A S r ' I l i i L , CP t » ) F i g . 2 1 E f f e c t o f L o n g i t u d i n a l P o s i t i o n o f B u l b o n S e l f - P r o p u l s i o n F a c t o r s ( A ^ / A : . v = 1 5 % ) May 1966

' l a o IM'l A l . A - [ . C f F i g . 22 E f f e c t o f B u l b Size on m Pn = g I? \ \ \ f » = 0.50 § = ^ 1

' I

3 o flALlAST 1 F i g , 23 E f f e c t of B u l b Size on .Self-Propulsion F a c t o r s

Fig. 22 shows the result of study on the influence of bulb size on rn for bulb tip distances f r o m the fore per-pendicular of 1.27% and 2.56% of ship's length. I t shows that the larger and smaller protruding distances of bulb have a similar trend and that there is a optimum bulb .size for r,;. which increases with .speed. The variation of ru due to bulb size is more remarkable at the ballast condiiion than at the f u l l load condition. The number of model ships used f o r each case is only three and the precise optimum bulb size cannot be shown. The cross curve o f rit given here is an example of representation. I t

M O c a S H ? N O i70< < f/ocEi « < > E i ; E a r o . 1324 f m LOAD c O f C i n o N — — — l A L l A S T C O i ï l t l l > l SP.'EOOf Sre> K n o r . l V i 10 11 I I 13 U (5 I0 17 ,1 , 1 , 1

4-4

r —1 r I 1 1 1 — 1 — 1 &iO 0.12 0 , 1 * a i 4 0.1a 0 : 0 H O U O E N U W E ! . ^^^^1-^— F i g . 21 D . H . P . Curves o f the 190.5 m S h i p C o r r e s p o n d i n g to iM.S. N o . 1704

can be said, however, that the bulb of 7.5% area ratio was an optimum sire f o r this test range. The influence of bulb size on the self-propulsion factors shown in Fig. 22 is f o r the bulb with protruding distance of 2.56% of ship's length WT increases with bulb size, but f and

Tilt do not show such a trend, varying little with bulb

size.

From the above results, the best propulsive perform-ance f o r such a f u l l ship f o r m as C s is O.SO, L/B 6.5 and B/d 2.76 will be obtained in case where ils ICB is - 2 . 5 % , bulb size 7.5%, and bulb protruding distance 0.5¬

1.0%. It must be remembered, of course, that thess figures varies with ship's principal particulars and speed. For reference the D H P curve of the actual ship corres-ponding to M.S. N o . 1704 is shown i n Fig. 24. Here, the Schoenherr's formula was used in calculating the

frictional resistance, taking A C ^ - o f - 0 . 0 0 0 3 and the scale

effect of wake fraction w was not taken into account.

4. Closing Remarks

What has been explained above is only a part of studies on full ship forms'carried out in Japan and other studies have been made not only in the Ship Research Institute whose acliviiies were explained with emphasis in this report, but a number o f research studies on f u l l ship forms have been made in Mitsubishi Heavy Indus-tries. L t d . , University of Tokyo. University of Yoko-hama and University of Osaka and .so forth! Since it is impossible to report a!! of these studies, only those con-sidered as forming main stream of systematic series model tests have been explained in fhis report.