2 8 AUS. 1983
ARCI-UEF
1\i
1T[t3IS11t 'J'ECI1\J(.L JF iLF11\ No. 154
Hydrodynamic Design and Development of High Speed Craft in MHI
December 1 982
MITSUBISHI HEAVY INDUSTRIES, LTD.
Lab, v Scheepbóuwkunck
' t
I I
ISStJ 054Ci-4Ó9XTechnnuoqeschao t
Hydrodynamic Design and Development of High Speed Craft in MHI
Katsuyoshi Takekuma*
Eiichi Baba*
Owing to the extension of Exclusive Economic Zones up to 200 nautical miles off the Japanesecoast, the area of patrol has ex-panded. High-speed craft offering improved operating-cost and seakeeping qualities in rough seas are required for this purpose. To meet this demand, investigations of various aspects of the hydrodynamic performance of high-speed craft have been performed at
the Nagasaki Experimental Tank. This paper focuses on some recent studies.
Firstly the method of predicting propulsive performance, including the effect of propeller cavitation, as developed at the Nagasaki Experimental Tank is presented together with a discussion of related studies. To aid understanding of seakeeping performance and its relation to hull-form variations, a method of analysing measured ship motions bymeans of Fourier analysis of two or three models running side by side in the seakeeping tank is next proposed. Finally, results of an investigation of roll-induced course instability at
higher speed are given on the basis of a simulation study of sway-roll-yaw coupled motions for semi-displacement craft.
1. Introduction
Owing to extension of Exclusive Economic Zones up to 200 nautical miles off the Japanese coast and in response
to the trend towards high-speed craft for development of
tourism and the Japanese offshore islands, demand for
high-speed craft with a principally ocean-going capability has
mounted. The need for diversification to assure escort
duties for large ships entering and leaving port, to provide
oil recovery services, and to strengthen the fire-fighting
system has also simultaneously arisen.
Mitsubishi Heavy Industries have constructed many tor-pedo boats and patrol craft for the Japanese Defense
Agen-cy and Maritime Safety Agencies. The company has also
recently scored major successes in the development of large high-speed passenger craft operating a variety of services
around the Japanese coast and is currently engaged in a
number of research projects to assure demand for sophisti-cated high-speed craft.
Central to the design philosophy underlying such
high-speed craft are a propulsive performance, seakeeping/ manoeuvring performance, and propeller performance at
Nagasaki Technical Institute, Technical Headquarters
Table i MHI-built high-speed craft
low cavitation numbers sufficient to allow them safe
ocean-going operation at speeds far exceeding those of
conven-tional high-speed cargo ships. Especially in recent years, it
has also become necessary to perform high-level hydro-dynamic evaluations centred on ride comfort, operational
features, carried equipment, stability, and safety.
This paper describes the researches on propulsive-per-formance, seakeeping-perpropulsive-per-formance, and propeller research for design and development of various types of high-speed
craft and also proposes an original method of predicting
propulsive performance which has been developed based on
the analysis of sea trial results for various types of
high-speed craft. Also documented are some investigations cen-tered on evaluation of seakeeping performance, transverse
stability problems encountered during high-speed opera-tion.
2. Building high-speed craft at Mitsubishi Heavy Industries The high-speed craft types reported in this paper have an
operational Froude number v/\/gL of over 0.5 and are
under 100m in length.
Craft I Il III IV V VI VII VIII IX X XI XII
Number constructed 1 2 2 2 2 16 1 5 2 1 1 5 Year of construction 1954 1956 1957 1957/58 1959 1962/65 1962 1962/65 1966 1969 1967 1972/75 Length, oa Ini) 15.00 27.00 21.00 33.50 23.00 8.00 32.00 21.00 26.00 26.00 25.00 35.00 Breadth Im) 4.20 6.75 6.00 7.50 5.50 2.50 8.50 4.80 5.60 5.60 6.20 9.20 Depth Im) 2.20 3.15 2.60 3.50 2,45 1.10 3.40 2.50 2.70 2.70 3.22 3.75 Machinery output hp) 220x2 2000x2 1000x3 2000x3 800x3 280 3140x3 1500 570x2 1100x2
21
3300x2Maximum speed (knots) 20.62 29.95 37.74 33.10 40.36
apx,
450 approx. 23.0 26.76 3195 approx. Hull structure Jightweight (hYdrofoil' (hydrofoiI' lightweightaluminium alloy craft 1 \\craft 1 aluminium alloy
Craft XIII XIV XV XVI XVII XVIII XIX XX XXI XXII XXIII XXIV
Number constructed 10 1 11 1 9 1 1 1 1 1 1 1 Year of construction 1971/73 1971 1974 1977 1978/80 1980 1980 1976 1978 1978 1979 1981 Length, oa Im) 21.00 18.80 26.00 45.00 31.00 48.30 45.00 23.50 23.50 30.00 23.00 27.00 Breadth Im) 5.30 4.20 6.30 7.80 6.30 8.20 7.80 5.00 5.00 6.00 4.80 12.50 Depth rn) 2.70 2.20 3.00 3.90 3.30 3.90 3.90 2.30 2.40 3.00 2.00 5.10 Machinery output hp) 1100x2 1000 1000x3 2206x2 2400x2 2420x2 2420x2 650x2 1125x2 1240x2 673x2 1900x2
Maximum speed (knots) 27.4$ 26.00 22.10 28.75 33.25 29.79 29.46 20.75 27.15 19.21 18.09 20.61
04 0.3 02 e 0.1 3
Fig. i Propulsive performance of various types of
high-speed ships
edhuIl
Lightening of structural weight is a key
performance-related problem in the design of high-speed craft, and, since
construction of the all-aluminium alloy craft Arakaze in
1954, Mitsubishi Heavy Industries are using lightweight
aluminium alloys in most craft today.
MHI-built high-speed craft have so far been of
hard-chine and hydrofoil type, but hovercraft and SWATH ships, etc., have also been constructed. Table i lists the principal particulars, machinery outputs, and speeds of the MHI-built
hard-chine craft addressed in this paper in combination with those for hydrofoil craft and SWATH. Fig. i graphs a
comparison of the propulsive performance of various types of representative European high-speed craft as reported in
paper (1) with comparable craft (the hard-chine ships
ad-dressed in this paper) built by MHI. The A and symbols
are used to indicate the craft built by MHI, whereas the
symbols mark the performance of craft built elsewhere.
Among the MHI-built craft, the symbols
also indicate ship hulls with mild steel structures.Various types of representative ships are pictured in Figs. 2-8. As indicated by these illustrations, high-speed
Fig. 4 Fishery protection boat Fig. 5 Passenger boat Fig. 6 Survey vessel (SWASH) Fig. 7 Escort boat Fig. 8 Firefighting boat
common problems in terms of hydrodynamic performance. A classification of these problems is listed in Table 2.
3. Propulsive performance research
For prediction of the propulsive performance of conven-tional ships, especially those of single-screw arrangement,
an appropriate method was proposed at the 1978
Interna-have become broadly diversified but pose craft applications
Fig. 2 Torpedo boat
Fig. 3 Patrol boat
Table 2 Hydrodynamic problems of high-speed craft Resistance! propulsive performance Propulsor performance Seakeepi ng performance Manoeuvring performance
Variation in wetted surface area due to trim variation and spray generation during
high-speed operation
'Separation of resistance components
Ship!model correlation in propeller cavitatirig condition
Evaluation of effect of propeller cavitation
and shaft inclination on propeller efficiency
and root erosion
Propeller excited pressure fluctuation
Evaluation of performance of various types of
propulsors
Development of nonlinear ship motion predic-tion method
Evaluation of effect of motion accelerations
on human body and shipboard machinery and instruments
Occurrence of broaching during operation in
following seas
Stability during high-speed operation
tional Towing Tank Conference (ITTC). According to this
method, ship hull resistance is divided into various compo-nents, the respective scale effects are considered. The scale
effect on wake fraction in self-propulsive performance is also considered. Then the propulsive performance is pre-dicted by taking into account of the physical properties of
respective elements.
lt is thus hydrodynamically a much more rational meth-od in comparison with the direct scaling-up methmeth-od. In the
case of high-speed craft, however, there are, in addition to
the Froude number and Reynolds number, other physical constants relating to flow phenomena about the ship hull,
such as cavitation number and Weber number, making
direct application of the above-noted method difficult. lt has moreover become necessary to establish a practical method of predicting the propulsive performance of high-speed craft while retaining the rationality of the foregoing
method.
Given below is a brief account of the method originated
by the MHI Nagasaki Experimental Tank for prediction of the propulsive performance of high-speed craft, together with a summary of the research work associated with its
development.
31 Ship hull resistance performance
The total resistance imposed on the hull of a high-speed
craft may generally be broken down into the following
three components: pressure resistance (resistance obtained
through integration of the pressure imposed on the ship hull surface in contact with the water); frictional resistance (resistance obtained through integration of the tangential stress imposed on the ship hull surface in contact with the
water); air resistance (aerodynamic resistance imposed on the ship hull located above the water).
Among these components, pressure resistance may be
thought to consist of the following components: those due
to dissipating gravity waves, breaking waves, spray, and due to defect of pressure recovery by action of viscosity.
The frictional resistance component due to variation in
wetted surface area through spray occurrence is included in frictional resistance as noted above. When small ship models
are used for resistance tests, spray form differences arise
between model and full-scale ship due to the difference of
Weber number.
The running trim angle of high-speed craft is also
differ-ent from that of convdiffer-entional ships. Wetted surface area and water-line length variations are therefore substantial.
To seek the wetted surface area in such circumstances, vari-ous methods are available, such as paint visualization of the wetted surface, observations of the craft bottom through a
transparent hull, or visual measurements of the craft bot-tom and sides. Fig. 9 gives an example of the results of
visual measurements for various types of high-speed craft. Wetted surface area exhibits appreciable variation as ship speed increases. Major differences in this variation are due to the differences of hull forms.
On the basis of the foregoing, it is extremely difficult to
identify and separate the respective hull resistance
compo-nents for high-speed craft. Even during analysis of
resist-ance test results for various types of craft, consideration of variations in wetted surface area and waterline length calls
for a great deal of time and effort. To produce some simi-larity with methods of predicting propulsive performance for conventional ships, it has been necessary, from the
practical viewpoint, to consider methods by making use of still waterline length and wetted surface area.
Ship/model correlation factors have in this case a
physi-cal content differing somewhat from those applied to
con-ventional ships. However, when dealing with craft operating
in semi-planning conditions, it may be considered that the
correlation factors roughly correspond to those for conven-tional ships. Since, in the case of high-speed craft, the
viscous/pressure resistance components are regarded as
be1.4 -1.3 Model 12 0.8 -s 0.7
-Wetted surface area
during operation
\ \
S, Wetted surface ares
0.6 at rest
1 2 3 4
t,, /V
Fig. 9 Variations in wetted surface area during operation of various high-speed craft models
MTB154 December 1982
8
0030
o o'
5 6
8
Light load Design load condition condition
0.025
0,020 1
0.6 0.8 1.0 1.2
Fig. 11 Variation in residual resistance coefficient curves depending on flow pattern around transom stern ing small,
it
¡s thought appropriate to use a two-dimen-sional extrapolation method based on the Froude method.For the new design of a specific type of ship, a type
ship with approximate principal particular ratios is selected, and from experimental tank data of the type ship the resist-ance performresist-ance of the ship hull can be predicted. On the basis of still waterline length LWL, ship breadth 8LWL' and corresponding displacement volume , Fig. 10 graphs the distribution of principal particular ratios for ship types used ¡n resistance tests at the Nagasaki Experimental Tank. The
plot of the points indicates the design load condition.
Re-sistance tests in several different load conditions were also conducted.
During the prediction of approximate values for
resist-ance performresist-ance, it is possible to use a simplechart based
on these experimental tank data. For instance, as the
princi-pal parameters controlling the resistance performance of
high-speed craft, L/B, L/v113, are
select-ed, with application of a method of Rr/
values obtainedthrough non-dimensionalisation of residual resistance
R,-with displacement . This method may be used to predict approximate values of total resistance with special
estima-tion of fricestima-tional resistance. To obtain the performance of
round-bilge semi-planing craft, van Oossanen proposes charts of the same type2
Ship hull resistance performance is largely determined
LwL/B
Fig. 10 Hull principal particulars for resistance tests
0035 B Exp. No. 2 Fv =0.86 Exp. N. 4 Fv=0.9 i Exp. No. 6 F =0.99
Fig. 12 Variation in flow pattern around transom stern
by the principal parameters L/113, L/B, and B/d, but it
is also responsive to the effect of various other elements, such as the frameline form of the ship type, chine breadth
and height, transom stern cross sectional shape, and spray strip arrangement and so on. Hydrodynamic research
focused on resistance performance related to the hull form changes is extremely important. The resistance component
due to breaking of stern waves generated at the transom
stern of high-speed craft is reported by one of the authors3 The relationship between resistance coefficient and flow pattern at approximately the speed where the water surface
at the transom stern is detached is a delicate problem. As shown in Figs. 11 and 12, detailed investigations of this
problem reveal that a cusp is produced on resistance
coeffi-cient curves at boundary (B) in the vicinity of the speed at
which the water surface is totally detached. As far as point
(A) just before total detaching of the water surface by the after part of the transom stern, one part of the breaking
wave slips onto transom. Since the transom sternis
accom-panied
with such disturbed flow,
resistance variations measured by a resistance dyrtamometer become large, asg C)
c R A Transom
I 2PU'A cross-sectiosal area
\\
/ N/ ;i;
¡Triangular OpeimumEIIiptCaI sol atron
Triangular
j-Ç\
Rectangular .5 .5/
'N N
optimum solution Exp. Ne. I 100g \ resista nce variation eFig. 13 Variation in measured resistance depending on flow pattern around transom stern
1 2 3
F,, = U/fgn
Fig. 14 Relationship between transom stern cross-sectional shape and stern wavemaking resistance coefficient
where the wave is totally detached (C).
The relationship between transom-stern cross-sectional shape and wavemaking resistance due to stern waves
gener-ated at the transom stern is presented in Fig. 14 for
theo-retically investigated results. If the transom-stern
cross-sectional shape below a still water surface is fixed, the form
at the point where wavemaking resistance due to stern
waves becomes minimum is of arch shape. That is to say, the wavemaking resistance coefficient increases from
opti-mum to elliptical to triangular and to rectangular shape. Fig. 15 shows breaking stern wave for transom sterns re-spectively having a triangular cross-section and an
arch-shaped cross-section. Stern wave breaking is visibly reduced in the case of the arch-shaped stern.
3.2 Appendage resistance
The appendage resistance of high-speed craft is
respon-Fig. 15 Comparison of stern wave breaking at transom
stern
4
I
Transom stern with triangular cross-section
-ç
-. - STransom stern with arch-shaped cross-section
4-screws
car terry
--MTB154 December 1982
.iR.= R..-R,.-A)ppenduge resistance
F= Wetted surface area of all appendages
P.12= Lateral urea of appendages
3. shafts submarine chaser
(shafts shaft brackets, rudders)
2-shafts destroyer - (shafts, shaft brackets.
rudders, sonar dome)
3shufts torpedo bout
(shafts. shaft brackets, rudders)
sible for a major proportion of total resistance. For
predic-tion of appendage resistance, a rapredic-tional method, as
pro-posed by Hadler, is to sum the resistance of individual
ap-pendag. On the other hand Taniguchi15 has proposed a
simple prediction method for use at the initial design stage. This method is based on results of investigating append-age resistance scale effect on geosims of Lucy Ashton, being
intended for use with the Reynolds number based on the
wetted surface area of appendages. This approach is
illus-trated in Fig. 16. In this method the appendage resistance is expressed in terms of form effect relative to the
calcu-2' 10' 2X 10
6 8 JQx 2 3
R-Fig. 16 Appendage resistance coefficient 4
2 .5
À/L A:L o 0.75 1.50 1.00 o 2.00 o 1.25 - Still water haiL 1/24 1.2 1.4 1.6 1.8 2.0 22 2.4 2.6
Fig. 17 Self-propulsion factors in waves
lated frictional resistance of flat plates. The form effect
determined in tank test is used for the prediction of
ap-pendage resistance of full scale ship with high Reynolds
numbers.
3.3 Self-propulsion performance
For self-propulsion tests of high-speed craft required to
run in high-speed conditions, it is necessary to reduce the weight of the model ship and in particular to lighten the drive motor and self-propulsion test dynamometer. A light weight of 2.8 kg dynamometer for reliable self-propulsion tests was developed in 1950's and many high-speed craft self-propulsion tests have been conducted with its
assist-ance6
In self-propulsion tests, a 3-3.6 m model is generally used, propeller thrust, torque, and rotational speed are measured, and self-propulsion factors are sought. For the
open-water characteristics of the propeller used at this
stage, there is no propeller-shaft inclination, and
non-cavi-tating characteristics are used. The effect of oblique flow on propeller characteristics between model and full-scale
craft and also the cavitation effect are therefore considered
separately.
As is clear from Fig. 17, which presents self-propulsion
factors in waves, it is advisable to use values virtually the
same as those in calm water. 3.4 Propeller characteristics
Since the open-water performance characteristics of pro-pellers intended for high-speed craft also include cavitation
number as one of parameters, extensive series tests and
design charts are necessary if the design data for these pro-pellers are arranged in exactly the same manner as for
con-ventional propellers.
In practice, small numbers of test are conducted, and then from plots of \/KTO/J with a.Ae/Ad arranged along
the horizontal axis and with KT/KTO (being the ratio of
thrust coefficient before and after onset of cavitation) and
efficiency
ratio e/e0 (the subscript O denoting values
prior to onset of cavitation) arranged along the vertical axis,characteristic diagrams excluding the effect of pitch ratio
and developed area ratio can be produced.
Examples are presented in Figs. 18 and 19. Table 3 lists
1.0 0.8 0.6 0.4 02 1.0 09 0.8 0.7 15 20 C,. X Ae/Ad
e9: propeller efficiency in cavitating condition
e90: propeller efficiency prior to onset of cavitation
Fig. 19 Variation in propeller efficiency in cavitating condition
the principal particulars of propellers used in series tests
for high-speed craft.
As previously noted, propeller shafts intended for high-speed craft operate in inclined conditions, and it is
there-fore necessary to take into account of the effect of this
oblique flow. If shaft inclinations are more than 6-8
de-grees, variations in characteristics as shown in Figs. 20 and
21 are observed.
Shaft inclination is also accompanied by the occurrence
of cavitation erosion at the root of the propeller blades7 To counteract this, shaft inclination is reduced, washback
at the blade leading edge is reduced, the radius of curvature
of the blade leading edge is reduced, and the position of maximum blade thickness is wherever possible shifted
to-wards the trailing edge, etc. Where necessary, measures such as perforation of the propeller blades are adopted, though, no specific countermeasures have so far been devised7' 8)
Propeller tip clearance is also a key aspect of design.
Ow-ing to the inhomogeneous nature of stern flow patterns of
conventional ships, excessive vibration due to abnormal
0.4 0.5 0.6 0.7 0.8 0.9 1.0 Q,x Ap/Ad
KT: thrust coefficient in cavitating condition
Kro: thrust coefficient prior to onset of cavitation
cavitation number (P - P)/pv2 Ae/Ad: expanded area ratio
static pressure at propeller shaft centre vapour pressure
propeller forward speed
Fig. 18 Variation in thrust coefficient in cavitating condition o 05 10 25 30 3.5 05 1.0 15 20 25 30 35 1.1 1.0 0.9 a°
.
0.1 o
Q-0,25 E
Ls
t
Table 3 Series tests of propellers for high-speed craft
cavitation phenomena generated at the propeller blade sur-face is imposed on the shell plating.
Since, however, the stern flow patterns of high-speed
craft are relatively homogeneous, it is possible to suppress
excessive propeller excited vibration through the adoption
o 0.04 0.03 0.02 0.01 O MT6154 December 1982
Fig. 21 Cavitation test results in oblique flow (KQ-J)
of a large expanded area ratio and tip clearance. Fig. 22 presents the diagram for prediction of propeller excited
pressure as proposed by Taniguchi. M-3 propeller
Diameter 1mm) 250.0 250.0 250.0 250.0
Pitch ratio 0.8000 1.0000 1.3000 1.6000 0.8000 1.0000 1.3000 1.6000 0.8000 1.0000 1.3000 1.6000 0.8000 1.0000 1.3000 1.6000 Expanded area ratio 0.6000 0.8000 1.0000 1.2000
Boss ratio 0.2000 0.2000 0.2000 0.2000
Blade thickness ratio
tic) 0.7R 004573 0.03430 0.02744 0.02287 Blade form Aerofoil Aerofoil Aerofoil Aerofoil
Blade number 3 3 3 3
Crescent propeller
Diameter 1mm) 230.0 250.0 250.0 230.0
Pitch ratio 1.2000 1.5000 1.8000 0.9000 1.2000 1.5000 0.9000 1.2000 1.5000 1.8000 1.2000 1.5000 1.8000 Expanded area ratio 0.7000 0.9000 1.1000 1.3000
Boss ratio 0.1667 0.1667 0.1667 0.1667
Blade thickness ratio
t./cl 0.7R 0.02864 0.02778 0.01823 0.01542 Blade form Crescent Crescent Crescent Crescent
Blade number 3 3 3 3
SC propeller
Diameter (mm) 250.0 230.0
Pitch ratio 0.900 1.070 1.200 1.200 1.180 1.500 1.286 1.000 1.600 1.286 1.286
Expanded area ratio 0.602 0.602 0.602 0.601 0.600 0.602 0.619 0.619 0.619 0.5141 0.4110
Boss ratio 0.2000 0.1819
Blade thickness ratio
ticl 0.7R 0.0612 0.0612 0.0612 0.0646 0.0855 0.0612 0.0612 0.0612 0,0612 0.0652 0.0709 Blade form Sc SC Blade number 3 3 0.20 025 o 0.15 0.20 0.20 0.10 0.15 o 0.15 0.05 0.10 0.10- 0.15 0 0.05
t
0.05- 0.10 - 0.15 u_ t O - 0.05 - 0.10 0.15 o O - 0.05 - 0.10 O - 0.05Fig. 20 Cavitation test results ¡n oblique flow (KT-J) P. 1329 Ku - J curves J= V/nD
07 0.8 0.9 10 11 12 12 11 10 0.9 0.8 07
j
U ,1) P. 1329 K''- j curves
C-15 Table 4 Analysis of sea trial results of high-speed craft in cavitatinq condition
4. Seakeeping performance research
At the initial design stage, it
is important to perform evaluations of seakeeping performance as well as ofpro-pulsive performance. Since, especially in the case of passen-ger ships, it is necessary to conduct the design process with the objective of suppressing the accelerations of passenger
spaces within constraints allowable through consideration of the sea states occurring in the intended service area, a key aspect is to improve the accuracy of predicting
sea-keeping performance. Date of sea trial Sea state Measured mile
Main machinery output
vs
N9
SHP
Trim Angle
total shaft horsepower
Shaft Torque Q' Erict. Torque Q' Prop. Torque Q=Q'Q pn2D5 K0 J ws e, KT 2T t R8 toR R0=R8toR C0 = R0/(p/2)u2V02 Cro
C =
CoCro Cf = C±(S0IV0213) log10uL/v toCf u = x 0.51444 n =N/60
K0 = erK00 8e = (1w,,,)/)1w5)
2-shaft case o coappendage & wind resistance o
.e co -513
.60
oco o .9 2 o co 0 13 0 E _ a LIC1mean C'1 C,, R,, R8 2T KT w5 K 70 K 00 Kr/Km K0/K00 d(Ae/Ad) mean of ® C'1 = )C + ACf) x S0! V,,213Cn=C+Cro
R8'=R0+LIRJ8=u/nD
from fair curve of w5 in
preceding column
Ji8)1w5)
, .e®
®
KKT = Ke9 =0>
-513 0,0 mO Owow
w . 13 E .t
KTIKTO (Cay. Test)
e/e90 (Cay. Test) KKT Ke9
0 01 02 0.3 04
Tip clearance ratio 4, D
Fig. 22 Relationship between fluctuating pressure amplitude, blade number, and tip clearance
3.5 Ship/model correlation in relation to propulsive
performance
Since, as previously stated, there are various
hydrody-namic problems relating to high-speed craft, it is extremely
difficult to predict propulsive performance with sufficient
accuracy.
lt is nonetheless necessary to develop a practical method
of propulsive performance prediction including the effect
of cavitation for use at the initial design stage. At the
Nagasaki Experimental Tank, analyses of the sea-trial re-sults of high-speed craft in cavitating condition have been performed as shown in Table 4. Ship/model correlation
factors ¿Cf, e1, KKT, Kep have been sought and collected. They include cavitation scale effect, propeller shaft
inclina-tion effect, craft trim variainclina-tion scale effect, etc., where:
LXCf roughness correction factor, being sought on the
basis of wetted surface area in still water conditions
and including the effect of variation in wetted
sur-face area during operation;
e-
(1 - wm)/(1 - w) correlation factor for wake
frac-tion;
KKT = correlation factor including shaft inclination and
cavitation effects with respect to propeller thrust coefficient;
Kep = correlation factor including shaft inclination and cavitation effects with respect to propeller
efficien-cy.
From an assembly of the foregoing correlation factor data, the propulsive performance of high-speed craft in a
cavitating condition can be predicted.
Prediction of the propulsive performance of hydrofoil craft is essentially performed in the same manner as for
conventional high-speed craft, though a special towing de-vice is needed for the experimental procedure. Fig. 23
illus-trates the resistance test towing technique for hydrofoil craft modeIs11. The scale effects of hydrofoils and struts
are individually considered, a method of prediction by
summing of individual resistances being adopted. lt is also
important to evaluate aerodynamic resistance when the craft hull rises during operation in the manner of hydrofoil
1.5 LO E 0,5 O 100 E 50 N p
Significant value of pitch
¡
p
Hwii,'3i (mm)
0 1 2 3
significant wave height Hw(i13) (m)(FuIl scale)
Resistance dyriamometer
p7
Arranged so that
p AB is vertical
H fi
Fig. 23 Resistance test technique for hydrofoil craft
models, with towing device yielding same force and moment as in self-propelled condition
4i Prediction of response features of ship motions
With the aid of the strip method, it is possible to predict
approximately response features of high-speed craft models1t Fig. 24 presents the results of towing tank tests
conduct-ed in regular waves for round-bilge (ship model A) and
hard-chine (ship model B> semi-displacement high-speed craft, together with comparative results calculated by the strip method. The length and displacement of both ship
models was identical, but ship breadth and frameline trend varied. A comparison with test results obtained in irregular waves is given in Fig. 25. Fig. 26 presents a similar compari-son for added resistance in regular waves.
As is evident from these comparisons, application of the strip method in the same manner as for conventional ships
is an effective tool for purposes of comparison of general
seakeeping performance at the initial design stage.
The frameline form n the forebody of high-speed craft
is, however, generally V-shaped, and the motion amplitude is large. Further, the frequency of encounter is high. There-fore a strong nonlinear motion response occurs. As shown
Q - 01 . 0.5 LO 0.5 N 40 60 20 40 -a 20 O Head waves p= 180' Fn0.504 (V,22 kn) 1.0 100 Hv i vi (mm) AIL AIL Vertical acc, at stern - 20 I Axial acc. at cg.
S gnificant value of vertical acc. at stern
Significant valae of vertical acc. at bow
0.5 1.0 15 2.0
200
0 1 2 3
sgrtificant wave height Hwi i3 (m)(Full scale)
2.0 1.0 40 20 40
I
20 MTB154 December 1982 Beam waves P=90' Fn=0.504(V,=22kn) Heave AILVertical acc. at bow
0.5 1.0 1.5 20 I, '2O Axial acc. at cg. Z 0Lu 0.5 1.0 15 20 a I.
Fig. 24 Comparison of calculated and measured ship motions and accelerations in regular waves for round-bilge and hard-chine ship models
Fig. 25
Comparison of calculated and measured ship motions and accelerations in irregular waves for round-bilge and hard-chine ship models Measured caicviarea
Roved bilan (ship nobel A) o
Hard chtrr (she model B)
-r
4
p (deg ) Speed Fu Marks Measured calculated Round bilge 0.504 (V,=22kn)0
-Hard chine o 100 200 100 200 Haci 31 (mm)(Mvdel) 100 200 HW(t vi (mm)(Model) 0.2Significant values of axial accelerative amplitude at c.g I o o 20 1.0 15 1.0 - 0.5 N 0.5 1.0 15 20
05 10 Ruod bilge Hard chine
r
2 3 4 Number of harmonicsdl
Fig. 26 Comparison of calculated and measured added
resistance in regular waves
2 4 5 I 2 3 4
Number of harmonics Number of harmonics
Accelerations in superposed waves p = 180 V, = 22kn equu, A,ÌL=0.40.h,,=5Omm A,ÌL=0.40.hi,,=SOmm -50
N!
o-6- 50 -2- 1.51_0 -n- 0.5 0.5 0.5 - -1.0--ì -50 o 50 2 3 4 5 Number of harmonics p180, A/L= 125, hi,=lSOmm (ship hw=2.l5m. V,=22kn)/\
Ç\ Heave pitch vertical acc at bo N, Encountering \wave J IsFig. 27 Record of ship motions measured in regular waves for round-bilge semi-displacement hull
P=180', AIL 1.25, h,= 150-mm (ship: hu-= 2.l5iml, V, = 22ko>
Heave .-.
Fig. 28 Record of ship motions measured in regular waves for hard-chine semi-displacement hull
A/L= 1.50
2 3 4 5
Number of harmonics
Fig. 29
Comparison of Fourier analysis results for accelerations of round-bilge and hard-chine ship models in Figs. 27 and 28, it does not necessarily follow that, even
in regular waves, the responses will be sinusoidal.
To improve the level of seakeeping performance
evalua-tion methods, consideraevalua-tion must therefore be given to flared forms, chine effect, spray effect, etc., in prediction calculations. Development of a Ship motion calculation method which effectively covers this nonlinearity is
con-sidered as a future research obective.
4.2 Relationship between ship hull form and seakeeping performance
lt is advantageous to use the strip method for prediction
of ship motions at the initial design stage, and the method is also considered fit for use in determination of principal
particulars, etc. Yet to pursue investigation of what are
known as human engineering aspects, which seek to
estab-lish whether differences in hull forms produce any effect
Accelerations in regular waves p = 180, h = 215m V, = 22ko
A/L= 1_00 A/L= 125
1.0
N
,= t8O
Pitch
High-speed ;r
monohull craft /_/ SWATH
1 2 3
AL
Fig. 30 Comparison of experimental results in regular head waves for high-speed monohull and SWASH ship
models
Passenger number XShip speed
Main machinery output
Fig. 31 Economic evaluation of high-speed passenger craft
on ride qualities and operability, we shall have to rely on
experimental research mostly at present.
To investigate the effect of change of hull forms on
ship motion responses, a special care is needed for the
tow-ing tank procedure itself. At the MHI Nagasaki
Experi-mental Tank, two ship models or three ship models have
been run in parallel using the wide seakeeping tank (30 m
wide and 160 m long). The method adopted is to make
comparative measurements or observations of ship motion responses in identical wave conditions.
Measurement results comparing the responses of two round-bilge and hard-chine craft run in parallel in waves have already been obtained, with ship motion amplitudes having been found marginally smaller for the hard-chine
craft. As indicated by the results of Fourier analyses of
response curves of vertical acceleration (Fig. 29), however,
the round-bilge is clearly larger for the first set of Fourier
coefficients, whereas the hard-chine is larger for the second and subsequent sets of Fourier coefficients.
In regard to the human body, the difference of motion
responses indicates that the round-bilge is felt to be softer
and the hard-chine is felt to be harder. Since higher
fre-quency components increase if ship slamming impacts
increase, this is considered to be associated with problems
ot resonance with the structure of the human bc1V, and
MTB154 December 1982
= 1.0 (V1= 44 knl Initial heel angle = 75°
Fig. 32 High-speed operation test of model with heel angle
investigation of this aspect will need to be conducted in
future.
As a means of reducing the motions of high-speed craft
during operation
in waves, the hydrofoil craft and the
SWATH ship have been developed. Fig. 30 presents a
com-parison of the ship motions of a conventional monohull high-speed craft and a SWATH ship during operation in
regular head waves.
Ship hull motions during operation are fairly small,
though, if consideration is given, for example, to a
passen-ger ship in respect of its operational economy in the form of passenger number x speed/main machinery output, the economic performance of the monohull form can be seen
from Fig. 31 to be far more favourable. Therefore, in regard
to application of such a special ship type, adequate
com-parative evaluations of various features including economic performance should
initially be performed before it
iseither adopted or rejected.
4.3 Transverse stability during high-speed operation
During the high-speed operation of semi-displacement type craft with high L/B ratio, yawing occurs as an accom-paniment to roll, being paralleled by generation of course
instability.
Clarification of this problem has, therefore,
become a major research objective for slender craft intend-ed for high-speintend-ed operation.
Ship model tests were conducted at high-speed by giv-Ing them an initial heel angle, with the heeling moments, sway forces, and yawing moments imposed on the ship
hull then being measured. In these experiments, the
above-noted quantities are respectively measured for variations
in the position of centre of gravity, presence or absence of spray strips, etc.
Hydrodynamic coefficients are sought on the basis of
yaw/roll, roll/sway coupling
in conjunction with thesemeasured values. Other coefficients for equations of manoeuvring motions were estimated from existing data, and simulations of sway/roll/yaw coupled motions were
accomplished. Fig. 32 illustrates the circumstances of a model ship operating with heel angle. Simulation results
are shown in Figs. 33 and 34(12)
3
High-speed rnonohull passenger craft with 401 passengers now n service
Fully-submerged passenger
hydrofoil craft with 282
passengers now in service
SWATH passenger ship with 446 passengers
Simulation of course stability test
\
without spray Strips ,p= +20V
ç=
)51 -5
with spray strips
Hull form A (Round-bilge) KG=3.70m GM 105m Vs =4Okn
Rudder angle 00
Initial disturbance of heel po -l-5deg : starboard
xt/L
10
Simulatos of course stability test
/
KG=4.87rn GM =2.22m yiL -5ç+t0
KG 370m GM =3.3gmHull form B (Hard-chine)
Vs=4Okn d=0
Initial disturbance of heel p0= -l-5deg : starboard
Fig. 34 Calculated trajectories of the
hard-chine type hull form B
(Effect of vertical position of
center of gravity)
For simulations involving a round-bilge semi-displace-ment craft with LWL = 52m and i 05m static GM operating at 40 knots, the trend of directional stability loss and mo-tion divergence can clearly be seen in Fig. 33 when spray strips are not attached. When spray strips are present, a tendency for stability to recover is displayed. This
behav-iour differs from the phenomenon of broaching by
conven-tional ships in following seas, though the phenomenon of
rapid loss of directional stability by yawing ships is also
described by Suhrbier as broachi Fig. 34 shows the
ef-fect of vertical position of center of gravity.
Owing to the current experimental research efforts and
improvements in the accuracy of predictions by simulation techniques, a major contribution will be made to
establish-ment of an appropriate GM for transverse stability during high-speed operation as well as the design of spray strips
and stabiliser fins.
5. Conclusions
Within the hydrodyrtamic problems which should be
investigated in developing high-speed craft intended for
ocean-going service, this paper has described the develop-ment of a propulsive performance prediction method con-sidering performance variations due to propeller cavitation together with associated research efforts.
lt has discussed the evaluation of seakeeping
perform-ance and has attempted to grasp the relationship between
differences in ship forms and motion responses by a Fourier analysis of these motion responses. Consideration has also
been given to the phenomenon of course instability as an accompaniment to the roll occurring during operation of
semi-displacement type high-speed craft, the problem being
treated by a method of sway/roll/yaw coupled motions.
Future efforts should include further investigations of 17
(8
(9
(1
References
I Brown D. K. ai.'l Marshall P. D., Small Warships in the Royal
Navy and the Fishey Protection Task, Symposium on Small
Fast Warships and Security Vessels, RINA (1978)
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1 Baba E., Wave Breaking Resistance of Ships. Mitsubishi
Tech-nical Bulletin No.1 10 (1976)
I Hadler J. B.. The Prediction of Power Performance on Planning
Craft, Trans. SNAME Vol. 74 (1966)
1 Taniguchi K.. Model Ship Correlation Method in the Mitsubishi
Experimental Tank, Mitsubishi Technical Bulletin No.12 11963) Taniguchi K. and Watanabe K., New Electric Self-Propulsion
Dynamometers, Symposium on the Towing Tank Facilities, Instrumentation, and Measuring Techniques, Zagreb (1959) I Taniguchi K. and Tanibayashi H., Root Erosion Experienced
on the Propellers of a Destroyer, Journal of the Society of Naval
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I Rutgersson O., On the Importance of Rudder and Hull
Influ-ence at Cavitation Tests of High-Speed Propellers, High-Speed
Surface Craft Conference, Brighton (1980)
I Taniguchi K., Watanabe K. and Tanibayashi H., Compariscn of
Propulsive Performance between Model and Ship of a Hydrofoil Boat, Symposium on Testing Techniques in Ship Cavitation
Re-search, Trondheim (1967)
0) Bessho M., Komatsu M. and Anjo M., Investigation of the
Pitching of High-Speed Craft in Regular Waves, Journal of the Society of Naval Architects of Japan Vol. 135 (1974)
11 Kanda H.. Murayama Y., Tanaka M. and Suzuki K., Ergonomi-cal Methods of Evaluating Repeated Shocks and Vibrations on High-Speed Ships (ist Report), The Journal of Japan Institute of Navigation Vol. 63(1980)
Baba E., Asai S. and Toki N., A Simulation Study on Sway-Roll-Yaw Coupled Instability of Semi-Displacement Type High. Speed Craft, Proc. Second International Conference on Stability
of Ships and Ocean Vehicles, Tokyo 11982)
Suhrbier K. R., An Experimental Investigation on the Roll
Stability of Semi-Displacement Craft at Forward Speed, Sym-posium on Small Fast Warships and Security Vessels, RINA
(1978)
these different problems to assure performance ao/L improvements in ocean-going high-speed craft
for which future demand is expected to be heavy.
Development of the method of predicting the propulsive performance of the high-speed craft
described in this paper was completed by Dr. Tani-guchi during his term as head of the Nagasaki
Ex-perimental Tank and is now in use as the MHI
standard method.
5 Firstly No. 3, Vol. 18, 1981 issue of Mitsubishi
Juko Giho was translated by the United Kingdom
publisher High-Speed Surface Craft and published as the February 1982 issue of High-Speed Surface
Craft. The translation was reviewed and revised
by the present authors and some results of recent studies are added in the present paper.
Fig. 33 Calculated trajectories of the round-bilge type
hull form A (Effect of
spray strips) (1 12 (3 (4 15 (6
