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OCR for page 181
HULL DESIGN by CAD/CFD SIMULATION
Hideaki Miyata and Koji Gotoda
(DepaThrrent of Environniental and Ocean Engineering, University of Tokyo)
ABSTRACT
A CAD ystnm and two CFD sim ration
tech iques are combined to compose a de igm method
for hip hull fomms The first CFD techmiq e is for floe
ship pe fommance in ready straight course, which
provides re i to ce pr pestles,: d it e second lerlnnq e
is for the motion pe fommance in waves, which provides
added resistance and motion prope ties By repeating it e
ycle of CAD CFD procedure the h 51 fomm is
successively improved to meet it e de igm req irement
Since added resistance is also estimated the de igm is
made fiom the viewp int of life-r:ge fuel-consumption
This ystem is iso amplied to it e design of the IACC
class sailing boat wifl the tatishcal wave data of IN
INTRODUCTION
The CFD im Saxon techmique based on
Navier-Stokes eq ah on was fir t ampli ed to the hull -form
deign in 1953 when the T MMAC-IV code was
completed at it e Univer ity of Tokyo :d d sthbuted to
the mater hipbuilfing rU1111/Slllt. Since then a number
of codes have been developed and inhoduced to floe
de ign office b it e past 10 years such CFD ted immR
have been e Fended to it e pianffy mohon and mohon in
waves The use has been made of it e time-marching
solution procedure such as that of the MAC method anc
the technique of c mbimng floe CFD solution wifl floe
solution of the equations of mohon The technic i
fifficulties con i t mo fly in it e heatmnt of the moving
boundaries, flat is floe fiee-suface and floe
body-bounda y of a ship in motion The den ity fl notion
method is often employed for the trongly interachng
free-smface motion :d it e mo ing bounda y techmq r
is well used H wevff it e use of the flved gyid ystem is
used to be more vffsahie when the mohon is e Dressed
by coordinates h:sformahon and inn i accelerations
When the wave spedmm of the sea on which
the hip will be expected to s .1 in her life-range is given
for the estimation of the tot i resistance and the resultant
fuel consmmphon, it e design of hull-fomm is made fl m
the total life- ycle viewp int This means that floe
hull-form design can be made wifl it e prefiddon of it e
OVER il pe formance of it e ship in her life For it e
special case of the design of the h 51-fomm of it e
Intemation i Amenca's Cup Class IMCCI sailing boat
this de igm procedure is very suitably applied Since it e
race area is :nommced about 3 years before, it e
stahstic i wave data can be collected :d then the
CAD uFD de ign moced re above mentioned is
successfllly applied though the tatishcal wind data
plays more important role in the design procedure
In this paper one of it e most advanced design
proced re for hull-form is described especi fly for the
IACC class s fling boat :d another case of the
high-speed forty
HULL DESIGN SYSTEM
Desigm system for Amn ica's Cup 2flflfl
For it e research and devel pment work for it e
30 Amenca's Cup yacht race the technic i team of it e
Nippon Challenge made the CAD plan in 1995
The most scientific CAD work was fir t pursued for it e
race of 1957 by the syndicate at S: Diego, which is
ret owed by Oliver et al This mocedme seams us shll
very used I as fw as the boat hardware design is
concerned However it e computer techmology has made
I rapid progress in it e past 15 years The pe fommance of
the computer has bee r ised by 10000 hmes in 15 years
The pe formance of the first supercomputer of it e
University of it e Tokyo, whi ch was inh oduced in 19 53
and I used for ship wave computation with
TUMMAC-IV method for the second worksh p on wave
resistance computation, is almo t same wifl that of a PC
in 2000 in it e meanwhile the CFD technique also made
rapidprogyess
For it e development and design j ob of Nippon
Challnge Amffica's C p 2000, the proced re described
in Fig I was ad pted, see whcle by Miyata et i, 2000
and a book by Miyata, 2000 The de ign is mo fly d ne
by the redproc i use of CAD :d CFD simulation More
than 200 hulls we desigmed :d thdr pffform:ce is
1
OCR for page 182
i
I D
1 ~
1 1
1 I (--
ALLY FOR DESIGN
. ........
FASISH1P
PPS one paint saying
-
1/7 SCALE NA-D Hawk
{~ NEST
q Arced moment a1diude
UPS
pear ~~I~
PPS 1.3
~~ Sl~LAllO~
~S^^ ~~
^PP~NDA~ES~ TEST
Arch moment grade
DESIGN P~CE~- Or SAILS
D~1C BROPE~lES by
~~E~V~C and WAVE
GOD / SHEATHE
Fig. 1 Design procedure of Hippos Chaben~c 2000.
predicted by the si~ulailon. When can progress is
s~sincd, thrcc to Our 1 /7~models are msnu~c~red ad
served far task test st the U~ivcrsky of Tokyo. Selected
designs me put in10 the neat static of 1/5~ model
experimoD1 ash keel sad added This is repeated several
discs. Thc hull ~~ in 3D dots made by the CAD
software is used by the grid-gener~or as prc-procossing
far CFD simulator. This data is also used ~, Oh
America swing process at ~ modal mature ln
the 1~1er stage Then some gem hull farms are obisined
the race Emulsion ~ pared with the Hind data of
1700 days at Hauraki (Surf of NO Zealand. The data are
given by the measurement on ~ boat far three years Tom
I 995 to 1 997. The Aid probably and rcgrel are
obtained far the En~1 decision of the Go hugs used in
the race.
The most important technology
as 1lIe
pcr~rms~ce prcdic~on simulation (PP(. PPS is
composed of CFD Emblazon technique ad the solution
method of elusions of Blob
Fig.2 Prototypic models ~ the Univcrs1~ Of Ha.
Advanced design system ~~1b wave statistics
The above procedure is mosey based on the
prance of the boat in a steady sleight course.
However the svcragcd added rcsistanoe of thc America's
Cup (AC) boat is spproxim~ely 2() ~ of 1hc rcsi~ancc
on calm isles Therefore the hull ~~ optimization
OCR for page 183
would better be made considering the added resistance.
The CFD simulation technique must be developed for
the condition in waves and a series of simulation in
regular waves provide the response function and the
added resistance on the respective hull are given.
Together with the wave spectrum of the race area the
prediction of total resistance of candidate hulls is made
and the optimum hull of statistically minimum resistance
is selected. Thus the advanced hull design method by
simulation is composed as shown in the flow chart of
Fig. 3.
This method is commonly used for merchant
ships of any kind. The hull of minimum resistance in the
whole life can be designed in the same procedure when
the wave spectrum of the sea she will sail in her whole
life is given. It is said that the life-cycle engineering of a
ship is completed by the CAD/CFD simulation method
from the hydrodynamical viewpoint
In order to complete such computer simulation
technique the CFD simulation of a ship in waves is most
important. In the 1990s the finite-volume method in the
framework of boundary-fitted coordinate system is
extended to the problem of maneuvering motion
(Ohmori 1998 and Izumi et al. 1998) and then to
arbitrary 3D motion (Takada et al.1998 and Sato et al.
1999~. However these works remain to be within
preliminary level. They cannot cope with large
amplitude motion or motion in oblique waves. Further
_
efforts must be devoted to improve the simulation
technique for large-amplitude motion in waves.
| CFD SIMULATION 1 | CFD SIMULATION |
I For MOTION in WAVES I I in STEADY COURSE I
. . . ~
|WAVE SPECTRU1\] ~3 - 43
.4
ADDED RESISTANCE
(PROBABILITY)
1 .
Get:
Fig.3 Flow chart for life-cycle oriented hull-form design
CFD SIMULATION FOR STEADY PERFOR1\IANCE
Performance prediction simulation
The development of PPS was started in 1993
and completed in 1995. The principal technology is the
finite-volume method in the framework of the
body-boundary fitted coordinate system, which is a
well-established technique in the fluid engineering field.
The finite-volume code WISDAM-VI in the O-O type
grid system is combined with the solution method for the
equations of motion (Akimoto 1995 and Miyata 1996~.
The time-marching solution of the Navier-Stokes
equation provides forces and moments in 6 degrees of
freedom and they are put into the equations of motion to
calculate acceleration, motion and trajectories. The
resultant motions, except for the steady advance motion
and rolling motion, are expressed by the deformation of
the grid system. When the hull makes rolling motion, the
body surface slips on the surrounding grids and the grids
are regenerated so that they keep to be fitted to the
body-boundary, see Fig.4.
Two versions of PPS were developed; one is
PPS for the performance in steady straight motion
(Hiroshima 1997~. In the close-hauled sailing simulation
the resistance at a pre-determined boat speed is obtained
as well as the boat attitude such as trim, heel angles and
linkage. All these data are very important for the
improvement of the boat performance. Difference of 0.1
degree of trim angle gives meaningful difference of
performance. The other is the dynamic PPS (Akimoto
1995) in which all 6-degrees of freedom motion are
computed and the boat speed is obtained as a solution of
the translational motion equation. Although the keel and
sail forces are given by model equations, this can give
important information for the polar characteristics and
transient maneuvering motion. However the use of the
dynamic PPS in the design procedure causes difficult
problems, such as too long CPU time for the simulation.
.L~ | - _ ~ _. I - _ I __ ~ _ ~ ~ _,,,,, I ~ I ~ ~ ;~ _ _ ~ _ _
~ r~r.-r-~+r ~.~..-ll--
,a
~ / /
N~
~ 7
~ I ~ —Let I _ I
__ ~
r ~
_
E. 3~l l>~> ~ ~ ~—:, ~ >. CADV <~] C, CFD
e,~ , ~,~ gamer) ~~ ~~l-~<}:)~-~
6;~t~~t ~_! ·
Fig.4 Some drawings of PPS
OCR for page 184
Accuracy problem
The accuracy problem is very important in the
dissemination process of CFD. So-called CFD validation
is a noticeable theme of research. However this seriously
depends on the application technology. The method of
design can determine the role of CFD simulation.
The obtained resistance value for an AC boat by
the WISDAM-VI is usually 10% smaller than the
measured one. Since the goal of resistance reduction is
10%, a designer is liable to be suspicious to the use of
CFD simulation. However most of the design process is
composed of compromise and trade-off, and the most CFD SIMULATION FOR MOTION PERFORMANCE
important decision is made based on comparison. The IN WAVES
accuracy in the relative relation of magnitude is of Grid system for motion in waves
essential value for sound selection of better hull.
The reliability of the CFD simulation by PPS
(WISDAM-VI) during the design procedure with 210
hull forms is, grossly speaking, 75%, which means that
the relative relation between two designed hulls is 75%
correct. The wrong suggestion of 25% used to be
compensated by the empirical knowledge and the
verification by tank test. By use of computer -graphics
the results of simulation provide us a variety of drawings.
These are also useful information to the designers,
especially those with rich physical insight. For example
the contour of wave height is good information to
modify the local hull form.
In the final stage of hull form improvement of
AC boat it was so difficult to attain further reduction of
resistance in the spring of 1998. The CAD/CFD design
work with our designers produced a number of worse
hull forms as shown in Fig.5. And finally about 1% of
resistance reduction was attained. After this final stage
four prototype models of the scale of 1/7th were
manufactured to verify the design and simulation results,
that is, 1% reduction of resistance, and to decide the hull
of the race boat. With the hybrid use of CFD and
experiment 1% reduction of resistance was successfully
attained.
In any ways the CFD simulation can be
efficiently applied to the design of hull form. Nowadays
it takes only 12 hours to complete the process from the
CAD design of hull to the receipt of simulation results,
while it takes at least 60 days when same thing is made
by physical experiment.
)~IN-R.-~ t.~./%lN$~}
(BSr, Sk' TO Atl0}
~ ~ E E E E E E ~ E E E E E r E ~ E ~ ~ E E E
b
Fig.5 Relative magnitude of resistance of AC boats, 20
hulls are designed before 1% reduction was attained.
For the PPS mostly used for steady motion
simulation, the O-O type grid system is used. The
movement of the boat except for the steady advancement
is treated by the deformation of the grid. Therefore only
gentle motion can be treated, although the rolling motion
is allowed making use of the "slip" technique on the hull
surface. In order to complete the motion simulation in
waves, different techniques must be introduced for grids
and motion treatment.
Then, in the framework of the boundary-fitted
grid system all motions except rolling are treated as
external forces in the Navier-Stokes equations, and the
rolling is treated by the rotation of the water-surface
plane about the x-axis. The employed grid system is O-H
type so that wave generation is more rigorously
performed than the O-O type grid system as shown in
Fig.6. Since the resolution on the free-surface is most
important for the ship flow problem, the grids are
clustered to the free-surface, which moves with the
rolling motion. This means that it is a free-surface
adaptive mesh system, as illustrated in Fig.7.
;< ',: I...
- 7
Fig.6 O-H grid system.
OCR for page 185
~ ova:
- -
F1~.7 Frec-sur~ce sdaptivc grid duos,
D
------ 1- -------- -- ~-----------'-------f------^'-^'^^'^^'^^^1^^^^^^^^^^^^^^^^^^^-F-------''^-'''F--'-'- ~ ~
I,,
Fig.8 RcsuI1s of numerical wave generst10n test.
nens~y Wanton metbod Par ~ee-sur~ce motion
We have a lot of methods far the
implemen1~ion of the ~ce-sur~ce condition. {hey have
resp~c~ve sivant~gcs sad disadv=1sgcs, and s most
suitable method must bc chosen ~r rcspec~ve problem.
For the prcsen1 problem in which strong nonlinear Wave
modon is c~pectcd 1be denser ~ncDon method is
supposed 10 bc most subtle, Once one of the ultimate
goal of the Prescott method is 10 simulate slamming
l~OtiO~ in largc-amp~1ude Caves. Boise one of 1hc
dis~dv~nt~g~s of We density Unction method is lower
degree of accuracy this mast be tested. Onc of the test
results is shown in Fig.& far thc case of regular Haves
gun crated by the numchcsT ~ave-msker Ti~o-historic~1
records of Cave hcigh1 arc compared at Eva pointy A to
E in thc lonpitndin~1 direction. It is noted that the
dissipation of wave height is of the sstis~cto~ level
Thea sufficient number of grids arc allocated on the
ee-su~ace.
The [nite-volumo method is employed in the
memo of the sbove-me~boncd add system. The
solution al~or~hm far the ~~icrStokes emotion is of
the (me-marching SAC type. Since the grids are
deformed, the moving velocity vector iS introduced into
the N~vier-StoLcs equation as Pilots,
+~ ~-v~=~+{v ~u+>urp~+K
V u=0
(1)
{2)
Here, u is the velocity veo10~ v is 1be moving velocity
Re is the Remolds Embed aDd ~ is the ext~mal farces.
The Allowing inert farces arc included in K.
~=~xV-~x~x~xr~ ~
Here, the Brat 1crm is Sac Coriolis Cc, the second is
the circum~rcrtid farce, the third is the singular
ccclcr~ion and the Numb is 1be tr~sl~io~1
accclc~ion, where ~ ~ angular Clock vector ~ is the
velocity vector r is the poshion vector and Vs is the
voloci~ of the origin of the body-~xed coordinates.
Ab vec10r vanillas are defined in rho Cartesian
coordins1cs, and 1be velocity components and pressure
are Acrid in the clangored arr~gemcnt. The third order
OCR for page 186
upstream differeneing is used for convective terms and freedom and reliable models of sails and keel. However
the second-order centered differeneing for other the robustness of the code is not very satisfactory in this
differeneing in space. The SOR method is used for the ease. Only 2-degrees of freedom motion is performed for
solution of the pressure. The first-order Euler explicit the first step. The conditions of computation are shown
scheme is used for the time-integration for simplicity in Table 1. The most typical close-hauled sailing
and efficiency. condition, that is 25 degrees of heel angle and 2 degrees
The solution of the Navier-Stokes equation is of leeway (yaw) angle, are assumed and fixed. Therefore
combined with the solution procedure for the equation of heaving and pitching motions are simulated in the
motion as shown in Fig.9. The solution of the equation heading wave condition.
of motion gives the accelerations and the integration of
pressure on hull surface provides forces and moments
for the equation of the motion. Thus the solution of the Grill points
Navier-Stokes equation is combined with the solution of Computation domain L=4.1, Radius=.
the equation of motion in the time-marching procedure. Minimum grid space ~ 3.oxio~3
Reynolds number 1.oxlo6
Froude number 0.366
Time of simulation 19.0
Time for acceleration 1.0
Time of beginnig of making way' 10.0
Maximum of dt 1.0x103
CFL 0.5
Length of Wave 1.0
Height of Wave 0.03843
An incident angle 180.0
Heel angle of Boat 25 0
Leeway angle of Boat 2.0
| S TART |
| Tidal Condition |
l
| lnidal GRll) General|
lime Len r
T=O? _~ RsadRese;~t Data
Update D - sitar Ebacdon and Generate Wam
| Solve E - adion of 1~1icn l
1
`eWator Surfacer| GRlDGeneration |
InertiaF=ce l
. .
Connects Term l
on
.g
En
Turbulencel~del l
. .
Difl~usim Term
Intermediate Vel°QtY I
AS PIUS 1
Update Pressure l
Adore velocity l
H~dro~yna~iic Force Judgment l
~ 3
Fig.9 Block diagram for the motion simulation in waves.
Two-degrees of freedom motion
The most useful simulation results will be
expected when it is conducted with 6-degrees of
Table 1 Condition of computation
The tested model is a typical IACC yacht,
which is 24.5 meter long and about 4.1 meter wide. The
lines are shown in Fig. 10.
:=~-
~-~2~ `" ~\ ~` ~ ~ ,~ / ,~T
Fig. 10 Lines of tested model.
This boat is assumed to be sailing at 9.5 knot
(Fn=0.366) in the regular incident waves of 700mm
height and wave length/ship length ratio of 0.77 and
1.54.
A typical computer-graphics drawings are
shown in Fig. 11 for the ease of 1.54 wave length ratio.
OCR for page 187
Aid. ~ ~ D:~g:~n of res~e due to p~e on the 16~] (~) and waves ~nteraet~ng Wash the 15~t I.
By use of tints s~n method the added
feSIStance on fY~ dIf~-~t hulls are compared On ~e
Same condItIonS Wash the CaSe of FIg. ~ ~ . Th~ total
ancc cOc~nt at two ways Ieng~th condItIo
compared wash the CXperIWe~T fesuttS In Figs.~2 and
~ ~ (~5,70ly~
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ m ~ ~ ~ ~ r ~ ~ ~ ~ ~ g; ~ ~ g ~
kid- 0~5 ~0,5. ~0W0~( t~0 (~70 {~n
50tWecn ~70 Cowls )5 =~=gi~ly (~' ~6 5~5
S £,8.~. p{~>,rIdC ~S,0~.! Newt ~: the
development of ~~t boat in wow is.
TTeal iSoat Scale liL'--~r~/IX.9frn]
[~ }.7i At ~ 8.~;n
OSP-~.Stkilof)
j a cad ~7a,?'~ ~
i........
~.~.~ ~
(} 0~3~)S?49 ,, ...,A. ALA {3 0~3.~:
Fig. ~ ~ co~1'pariSOn Of reSIStance Coc~ can't between
00~320~ 3~] ~~t ]~ ti)0 Sage of O.77
wavelength iat1.~.
0. ~ ~ ~ ~ ~ 3
0.~3~304
0~03
0.~,
0.~!
Reat Bo~ Senile lIL--~[;n]~18.~]
idol., -~3. 7~1t]]l ~ 8.: its.]
851 ''9.Sti~!Ut]
...... _ .... . __
Il In? (l t3~054~R ~ AA A ~ ~ . ~ h Bohr. ': -:7
~ (INS'.! -l
cant iN"xti~e
~ Eve
...... __ _.
lo. ~ ~ 88~0 ~5 Fang ~ ~ 2~ t60 0850 0: ~ 5: \~570_~g't~ ratio,
Three-~S of ~~m motIo~
0~ t60 0~)g~t 00~]gi~ 0: 'are t0~t ~3-~:
· ~~s of ~~ am mot~n sim~i`~ i~ Anew ~~t i~
only surg~g and yawing mot,~3~s are restricted. The boa:
~s ac<~d to the boat specd 9.S knots ~n T.O
110~dI~St£~sCL) ti=C an6 the I~t ~~\rCS a e
`gS~nSe~6 at the :~w bo~y at the :~t at:~0
~ 50 6~e Sat 3.0 non6~3~l '~. i~e Wave ~e~'~
38 700~i~ {~3~^ t~0 t~.~-S63~0 t0~t sang t~0 ~~-~ggl)
3~Ldi~3~3~ th~t iS Oa77~ ~~ ~~ Aid
fih~ ABLY 81~^0 360Y`ilnl ~~ lFitigol4. i37 ~0 Of It;~0
coml3uter-gt-~Cs 6raw~g 2~he Aims p~re ~s creatod
RIl~ O~C 1OSC8~3~S plCtU(C iS S160~ O~ 'ARC ]~ S16C
OCR for page 188
of Fig.14. The Poineare mapping of the time-marching These simulation results imply that the present
records of simulated motion shown on the right side of CFD method can be employed in the CAD/CFD based
Fig. 14 seems to be useful for the understanding of the life-eyele design system for hull forms.
motion characteristics
..
s
.
' '~'''(}~4'- ' t~ l ~ ... 1
-~6 _~1 ~2 ~ ~ 4
~1
. ~ ~
. ~ ~
2 _,
. ~ ~ /
-- -I f....~....~.
·,^ ~4 ~\
.. 4 . ... .. ... .....
. ..................................................
_~ ;
~ ~;.V~.~ ...., i.....
( ~ . ~
. .... ,.~ )
Has'
4,} ~-
-
,:~
- :~_
P"
............ F ,, ~
._ ~
~ ~3h.~b#
~ .~.
Fig.14 Motion and wave pictures and Poineare mapping of pitching and rolling for three wave-length conditions
0.77,1.15 and 1.54 from above. The wave incident angle is 150 degree.
OCR for page 189
CASE OF HIGH-SPEED FERRY DESIGN
TUMMAC-IV method for fast ship
Unfortunately the CFD method above described
is not very appropriate for some group of hull forms
designed at different range of Froude number. Most
suitable CFD method still depends on the ship type.
One case is a high-speed ferryboat, either mono
hull or catamaran, of which design Froude number
exceeds 0.4. Wave generation of the boat is very
remarkable and then accuracy in the wave height is
much more important for these boats. Since the
boundary-fitted grid system results in coarser grid
spacing in the region a little far from the hull surface
where the accuracy in wave height is necessary, the CFD
code based on the rectangular grid system still have
advantages. This is why the TUMMAC-IV code
completed in 1983 (Miyata 1985), is still used by
designers of shipbuilding companies.
The slightly different version of TUMMAC-IV
code is recently developed by the authors making use of
the density function method for the free-surface
condition so that it can cope with wave motions with
higher nonlinearity. Another modification is that the hull
data from 3D CAD are used in the pre-processing
instenr1 of the affect plate
-
__
-
composed of wave resistance is given and optimum
length/beam ratio and block coefficient\ are suggested,
although it is obvious that the larger length beam ratio
and smaller block coefficient leads to smaller
horsepower. Therefore the optimum principal particulars
are determined from other aspects of design.
The TUMMAC-IV code with density function
method can also cope with catamaran hull in case each
demi-hull has symmetric hull form. Then the comparison
between monohull and catamaran can be done from the
resistance point of view.
Fig. 16 Two example of frameline with different block
coefficient.
Fig. 15 A typical wave perspective view for a fast ferry.
Optimization of principal particular
A typical application example is briefly Hull-form optimization
described here. Hull form design is conducted for a fast
ferry of 17000GT, 3400 ton, 35kt. The length is around
200m and the Froude number is about 0.4. From the
harbor condition the maximum draft is limited to 7m and
the beam-length must be greater than 24.5m from the
stability requirement.
By use of the CAD/CFD system the optimum
length/beam ratio and block coefficient was pursued by
successive repetition of CFD computation. The midship
section is shown in Fig. 16 and the computed wave
profiles are shown in Fig.17. By integrating the pressure
on the hull surface the pressure resistance mostly
Cb=0.56
—Cb=0.5 2
Cb=0.47
Fig. 17 Comparison of wave profiles on hull surface at
three different block coefficients.
For the second stage of hull form design the
optimization of the bow bulb is of significant importance.
For low and middle speed ships the bulbous bulb with
sphere-shaped head configuration is no more used but
bulbs with long protrusion and sharp entrance are
designed mostly based on the understanding of the
presence of free-surface shock wave. However for high
speed ships, of which draft changes only slightly, an
old-fashioned cylindrical bulb or so-called SV-type bulb
are efficient to reduce wave resistance.
For the present fast ferry a SV-type bulb as
OCR for page 190
shown in Fig. 18 is employed so that it may well fit to the and chief designer and the second author, a graduate
V-shaped framelines. By the present CAD/CFD system student of the University of Tokyo, as a member of the
the optimum protrusion and volume are pursued as design team. The design work for the two boats JPN44
shown in Fig.19. Since the CPU time for one case of and JPN52 were mostly made by the first version ofPPS
computation is several hours and the hull form for the steady sailing. It may be safe to say that the
modification is made by CAD process with some hours CAD/CFD system was satisfactorily applied to one of
of labor, it may be noted that the hull form optimization the most difficult hull design problem.
is performed very efficiently.
When the accuracy in the relative magnitude of REFERENCES
resistance is checked by experiment for respective hull
and the total design procedure is like that for the IACC J. C. Oliver et al., "Performance prediction for Stars
yacht, such design system will become to be a standard and Stripes", Trans. Soc. Nav. Archit. Mar. Enginrs.,
system. The design by simulation will become more 1990.
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L Bulb 2 Bulb 3 Bulb 4 I H. Miyata et al., "Finite-difference simulation of
nonl~near waves generated by sh~ps of arbitrary
Fig. 19 Comparison of horsepower between hulls without three-dimensional configuration", J. Comp. Phys. 60 (3),
bulb~left) and with three different bulbs. 1985.
Fig. 18 Normal bow and a bow with SV-type bulb.
1 9400
1 9200
1 9000
1 8800
1 8600
1 8400
1 8200
1 8000
17800
1 7600
1 7400
1 7200
P~
CONCLUSION
A very practical application technique of CFD
is presented. Since the fluid motion about a ship is so
complicated the accuracy problem of CFD is not yet
fully solved. However the design problem is essentially
complicated and the introduction of CFD into the
advanced design system leads to fruitful results.
The first author worked for the Nippon
Challenge America's Cup 2000 as a technical director
Representative terms from entire chapter:
hull form
