Esso Osaka - ITTC

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data, forces, rudder, hydrodynamic, model, turning, mean, Figure, using, angle, propeller, motion, were, 23rd, Esso, ship, Osaka, estimated, test, with, results, coefficients, difference, force, sets, each, shown, from, that, different

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23rd International
Towing Tank
Conference
Proceedings of the 23rd ITTC – Volume II 581
1. GENERAL
1.1. Membership and meetings
The Specialist Committee on Esso Osaka
was organized by five members and five
meetings were held.
The membership was
Prof. H. Kobayashi, Japan (Chairman)
Dr. J.J. Blok, Netherlands (Secretary)
Dr. R. Barr, USA
Dr. Y. S. Kim, Korea
Dr. J. Nowicki, Poland
Committee meetings were held five times
in the three years since last conference as
shown below,
1st July 2000 Boston, USA
2nd Nov. 2000 Wageningen, Netherlands
3rd May 2001 Ilawa, Poland
4th Oct. 2001 Tokyo, Japan
5th Feb. 2002 Taejon, Korea
1.2. Task proposed by 22nd ITTC
The studies on the Esso Osaka were carried out in Maneuvering Committee in 21st
ITTC. As a result of studies, following issues
are proposed to continue the analysis of the
Esso Osaka data in the following areas and to
organize a workshop to present the Esso
Osaka benchmark data and the results of the
analysis:
a) Reduce the scatter in existing data either
by eliminating suspect data sets, or by
stimulating new, benchmark quality experiments.
b) Compare propeller and rudder forces and
propeller-hull-rudder interactions.
c) Carry out a systematic series of simulations
using one reference mathematical model
(e.g. MMG with fixed propeller and rudder
forces and interactions) using available sets
of hull damping coefficients (linear and
nonlinear).
d) Compare the results of these systematic
simulations with available track data and
particularly the full scale trials data.
1.3. Use of Esso Osaka trial data as
benchmark
At the first meeting of the Maneuvering
Committee of the 21st ITTC in Trondheim,
Norway, the Committee selected an ITTC
benchmark ship for comparison of various
methods for predicting ship maneuverability.
Ships considered as this benchmark were the
Mariner, which was extensively investigated
by the Maneuvering Committee of the 11th
and 12th ITTC, the Esso Osaka for which unThe Specialist Committee on Esso Osaka
Final Report and Recommendations to the 23rd ITTC
582 The Specialist Committee on Esso Osaka
23rd International
Towing Tank
Conference
usually complete trials results and model test
data were available, Crane (1979a) and Barr
(1993), and a more modern ship form, such as
one of the MARAD Series Models described
by Roseman (1987). The Esso Osaka was selected for the reasons noted in the following
sections.
The primary advantages of Esso Osaka trials data as a maneuvering benchmark were:
1. An unusually extensive set of trials of the
Esso Osaka at full load draft had been
conducted with unusual attention to
measurement accuracy, including correction of trials results for the effects of
ocean current measured during the trials,
Crane (1979a, 1979b).
2. Conduct of trials in deep water and in water depths equal to 1.5 and 1.2 times trials
draft.
3. Captive model tests or free running model
tests of the Esso Osaka had been carried
out by at least 20 different laboratories,
using models with lengths ranging from
1.65 to 8.125 meters.
4. Drawings of the Esso Osaka hull, propeller and rudder, required for the RANS
calculations planned by the Maneuvering
Committee, had been made available by
EXXON.
In addition, a significant body of Esso
Osaka captive model test data had been previously collected for a USA Marine Board study
of ship maneuvering simulators and simulation, Webster (1992), and an analysis of those
data for that study had been reported by Barr
(1993).
The primary disadvantages of the Esso
Osaka as a maneuverability benchmark were:
1. The relative old hull form of a ship
launched in 1973.
2. The conduct of the benchmark trials before the availability of shipboard GPS and
the improved tracking accuracy available
with GPS.
3. The unavailability of good quality resistance or propulsion data, which would
also allow use of the Esso Osaka as a
benchmark for RANS flow calculations or
other ITTC studies.
Data for the Mariner were rejected as a
benchmark, despite the availability of extensive trials data and model test data because
maneuverability of that ship had already been
studied by ITTC Committees and because the
Mariner was an old and very atypical hull
form, and only four ships of the class were
ever built. No other comprehensive source of
ship and model test data for any ships of more
“modern” hull form could be identified by the
Committee.
The shortcomings of the Esso Osaka data
were considered minor when compared with
their advantages, and the Maneuvering Committee selected the Esso Osaka as its benchmark. The number of Ocean Engineering topics and Procedures should be continuously
maintained. A practical solution should be
found.
1.4. Lines on studies in Esso Osaka
Specialist Committee
In first stage of this study, proposed data
which were discussed in Maneuvering committee in 22nd ITTC were examined to know
the detail experimental conditions and analyzing procedures. It was confirmed that there are
mainly two kinds of mathematical models for
expression of ship maneuvering motion. The
proposed data may be different relating to the
mathematical model that is used for expression of motion. Two mathematical models are
selected to discuss the hydrodynamic coefficients and interaction forces. One of them is
MMG model (MMG, 1985), the other is whole
ship model: WSM. The details of the models
are explained in chapter 5 and chapter 6.
23rd International
Towing Tank
Conference
Proceedings of the 23rd ITTC – Volume II 583
In chapter 3 in this report, the reasons of
scatter in proposed data sets are discussed.
There are many kinds of reason which occur
the scattering in measured hydrodynamic
forces and the coefficients. Therefore, in order
to discuss the benchmark data, the data of which
we can know the experimental conditions and
analyzing procedures should be chosen.
In chapter 2, the discussion on proposed
data in 21st ITTC and the scattering are analyzed. The potential reasons of scattering of
hydrodynamic coefficients shown in proposed
data are discussed in chapter 3. In chapter 4,
the proposed test data including full scale trial
tests and free running model tests are summarized. These results are target data of simulation using estimated hydrodynamic forces.
The discussion in chapter 5 and chapter 6 are
main parts of this report. The contents of proposed data are studied for estimation of maneuvering motion of Esso Osaka. The discussions on proposed data are studied based on
MMG model and Whole ship model. Finally,
Benchmark data on hull and propeller and
rudder interaction are proposed in conclusion.
2. A COMPARISON OF MEASURED
DAMPING FORCES
2.1. Sources of hydrodynamic data
Force data for the Esso Osaka were available primarily in the form of hydrodynamic
coefficients derived from captive model test
data. Raw data or published plots of measured
forces versus test variables were available for
only a few tests, and the widely varying drift
angle and yaw rates of the tests made a meaningful comparisons of the force data problematic. 20 sets of hydrodynamic coefficients for
the Esso Osaka obtained by 18 laboratories
were collected and analyzed by the 22nd
ITTC Maneuvering Committee. The present
Committee has obtained four additional sets
of test data relating to WSM from laboratories
in Korea. The present Committee also decided
to eliminate from further consideration four of
the earlier data sets which were judged for
various reasons to be not reliable. As most
data were understood to have been obtained
using models with rudder installed, only those
data were considered. A total of 15 data sets
were therefore considered in order to investigate the scattering of predicted damping
forces and moments.
2.2. Summary of data comparisons
Predicted sway damping forces and yaw
damping moments were compared for data
sets understood to be for tests with rudder installed. In many cases the data source did not
indicate the operating condition of the propeller, or in some cases even if one was installed.
It was assumed that all data were obtained
with a propeller operating at either model or
ship self propulsion point.
Total damping forces and moments were
calculated for combination of five steady drift
angle, β = sin-1(v/U) and six non-dimensional
yaw rate, r' = rL/U. Figures 2.1 and 2.2 compare typical results for an eight degree drift
angle, for tests where a rudder was known or
believed to be installed. These figures show
rather large variations in total forces and moments, although the scatter is not as large as
that found by the 22nd ITTC Maneuvering
Committee due primarily to elimination of
suspect data sets having poor documentation,
apparent inconsistencies and/or highly atypical results. It was not possible to rationally
eliminate other data sets based on the information available.
2.3. Statistical Analysis of data scattering
In view of an inability to obtain data
needed to determining which data sets were
most reliable, it was decided to use a purely
584 The Specialist Committee on Esso Osaka
23rd International
Towing Tank
Conference
statistical approach to select sets of data that
might be assumed most “reliable”. To do this,
the mean value and standard deviation of
sway force and yaw moment were determined
using all data sets of Figures 2.1 and 2.2, for
each of the 29 non-trivial combinations of
drift angle and yaw rate. These values were
used to determine, for sway force and yaw
moment for each of the N data sets and each
combination of drift angle and yaw rate, a difference of the value from the mean value for
all data sets. The “deviation” of a data set was
then defined to be the average, for all combinations of drift angle and yaw rate, of the difference of the values from the mean value,
divided by the standard deviation, or:
Dn={∑m[(Fn(βm,r'm)–Fmean(βm,r'm))/σ(βm, r'm)]}/M
where:
Dn is average deviation of sway force or yaw
moment, F, for test data set n;
Fn(βm,r'm) is force or moment for n-th data set
and m-th set of values of β and r';
Fmean(βm,r'm) is mean value of force for all
data sets for m-th set of values of β and r';
σ(βm,r'm) is standard deviation for all data sets
for m-th set of values of β and r';
M is the total combinations of β and r', considered, M = 29, m = 1, … 29
N is total number of data sets considered, n =
1, … N.
Values of the “deviation”, Dn, for each
data sets were independently calculated both
sway force and yaw moment. Data sets with
average “deviations” of about 1.0 or greater
were eliminated, and this process was repeated with the resulting reduced data set.
Again, data sets with an average “deviation”
of about one or more were eliminated, leaving
only five remaining data sets for both sway
force and yaw moment.
There is no certainty that this statistical
process has identified the most reliable data.
However, it is encouraging to note that the
same data sets were independently selected
for sway force and yaw moment, that the
variations of forces and moments among these
data sets are quite small.
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0.018
0 0.2 0.4 0.6 0.8 1
Non-Dimens ional Y aw Rate - r '
Sw a y F
or ce -
Y
'
1 2 3 6 9 14 15 16
17 18 19 20
Figure 2.1 Sway forces for +8° drift for selected data set.
-0 .0 07
-0 .0 06
-0 .0 05
-0 .0 04
-0 .0 03
-0 .0 02
-0 .0 01
0
0 .0 01
0 .0 02
0 .0 03
0 0.2 0.4 0.6 0.8 1
YAW RATE - r '
YA
W
M
O
M
E
N
T
- N
'
1 2 3 6 9 14 15 16
17 18 19 20
Figure 2.2 Yaw moments for +8° drift for
selected data sets.
3. DISCUSSION ON THE REASONS OF
SCATTERING
3.1. Potential sources of error with tests
PMM Tests
The varying rate of rotation during yawing tests
Inadequate numbers of motion cycles to
23rd International
Towing Tank
Conference
Proceedings of the 23rd ITTC – Volume II 585
eliminate all effects of the starting transient and to permit accurate analysis of
the harmonic test data
Tests at reduced frequencies large
enough to introduce unsteady effects in
damping forces
Rotating arm test
Operation of model in its own wake after one revolution
Requirement to predict acceleration dependant forces which cannot be measured.
Systems identification (SI) of free-running
model tests or ship trials data
Systems Identification results are highly
sensitive to the quality of the data used and
the adequacy of the mathematical model. The
sensitivity of the process is illustrated by the
differences in the four sets of coefficients obtained using different models by Abkowitz
(1984). The validity of SI methods and results
has not in the past generally been established
by using the identified coefficients to predict
maneuvers different than those used for identification.
Model size
Model forces which are valid only for
the conditions (Reynolds number and
ambient turbulence level) of the particular test due to laminar flow (scale effects).
Wall effects when model length is large
compared with tank width or diameter,
particularly for large PMM motion amplitudes or large static drift angles.
It was concluded by the 22nd ITTC Maneuvering Committee that there was not conclusive evidence of significant scale effects in
the available Esso Osaka force data, although
large differences in forces were observed in
coefficients (forces) obtained at BMT using
the facilities and the same test procedures for
tests of 1.65 meter and 3.54 meter long models (Dand & Hood, 1983).
3.2. Potential sources of error of data
analysis methods
Methods used by various laboratories to
analyze captive model test data are rarely described in any detail. These methods can be
carried out using:
Purely mathematical methods, such as
regression analysis, using all test data or
a data set in which only clearly unreliable data points are eliminated.
An empirical approach in which the data
analyst assigns greater or lesser weight
to individual data points based on their
experience and knowledge of test conditions.
Data are analyzed or interpreted using a
particular mathematical model for hydrodynamic forces. Significantly different individual coefficients can thus be obtained when
using the same raw data. Ideally, these coefficients sets will predict similar forces and
moments, at least for drift angles, yaw rates,
rudder angles and propeller loadings which
are most typical of ship maneuvering, although this is by no means certain.
In following parts, the relation among the
experimental conditions and analyzing procedures and estimated hydrodynamic forces and
the coefficients are discussed.
3.3. Experimental conditions
The measured hydrodynamic forces are
changed due to following experimental conditions shown by Yoshimura (2001).
(1) The center of measuring forces
(2) The center of captive motion
(3) The freedom at captive model test
586 The Specialist Committee on Esso Osaka
23rd International
Towing Tank
Conference
(4) Error of towing speed
(5) Experimental condition w/wo propeller
(6) Propeller loading condition
The center of measuring forces
The measured hydrodynamic forces depend on the position of measuring instrument.
Longitudinal force and lateral force are not
affected by measuring position. However,
measured yaw moment is changed by the position of measuring instrument in the model
ship. Generally, motion equations are described based on the center of gravity. However, measuring forces are carried out based
on mid-ship position, because the center of
gravity of model ship is changed due to loading condition. Therefore, motion’s equation
are often described based on the center of
gravity, using hydrodynamic forces measured
at mid-ship position as following. The measured hydrodynamic forces depend on the position of measuring instrument. Longitudinal
force and lateral force are not affected by
measuring position. However, measured yaw
moment is changed by the position of measuring instrument in the model ship. Generally,
motion equations are described based on the
center of gravity. However, measuring forces
are carried out based on mid-ship position,
because the center of gravity of model ship is
changed due to loading condition. Therefore,
motion’s equation often described based on
the center of gravity using hydrodynamic
forces measured at mid-ship position as following,
XXrmvum GGG ==−&
YYrmuvm GGG ==−&
YxNNrI GGZZ −==&
(3.1)
where
X, Y, N: hydrodynamic forces measured at
mid-ship position
xG: distance from mid-ship to the center of
gravity
The relation between the captive position and
the measured hydrodynamic forces
The measuring hydrodynamic forces due
to turning motion are affected by the center of
turning motion where turning motion is activated. Measured forces are affected by experimental condition. Hydrodynamic coefficients are indicated in different values based
on the measuring point of Hydrodynamic
forces and center of enforced motion.
Table 3.1 shows the hydrodynamic coefficients based on different expression.
Table 3.1 Hydrodynamic coefficients acting
on bare hull Esso Osaka (Model ship length
2.5 m).
Motion CG CG Mid ship
Moment CG Mid ship Mid ship
X'vv 0.0218 0.0218 0.0216
X' vr–my 0.1871 0.1871 0.1905
X’rr 0.0062 0.0062 0.0122
X' vvvv 0.2786 0.2786 0.2743
Y'v -0.3901 -0.3789 -0.3786
Y'r–mx 0.0702 0.0556 0.0435
Y'vvv -1.2407 -1.2208 -1.2231
Y'vvr 0.2927 0.2644 0.1485
Y'vrr -0.3387 -0.3190 -0.3070
Y'rrr 0.0594 0.0536 0.0441
N' v -0.1263 -0.1437 -0.1439
N'r -0.0622 -0.0533 -0.0577
N' vvv  -0.0597 0.0115 0.0120
N' vvr -0.2341 -0.2118 -0.2164
N' vrr 0.0994 -0.0795 0.0657
N'rrr -0.0149 -0.0103 -0.0081
The methods of installing model
To measure the hydrodynamic forces on
surge, sway and yaw, the motions on these
directions are fixed. The fixing condition of
other 3 motions such as pitch, roll and heave
23rd International
Towing Tank
Conference
Proceedings of the 23rd ITTC – Volume II 587
affect the measuring hydrodynamic forces in
following cases.
In case of small GM at model test, the big
heeling angle induces the measuring hydrodynamic forces corresponding to that condition.
GM at model test must be same as full-scale
ship. In case of cramping the pitching and
heaving motion, the measuring hydrodynamic
forces are measured under the condition without sinkage. They differ from free running
condition in which sinkage is occurred depending on ship speed.
The experimental condition
When the hydrodynamic forces acting on
hull are estimated, the experimental condition
gives several effects on them. It is proper way
to carry out the captive model test using bare
hull. However, to reduce the experiment numbers, the captive test are carried out with propeller and rudder. And the hydrodynamic
forces acting on hull are estimated by subtracting propeller and rudder forces and their
interaction forces from measured total forces.
The estimated hydrodynamic forces acting on
hull by this way often show difference from
forces by measuring bare hull. As, the flow at
stern is affected by propeller and rudder, they
show difference ones. Especially, the suction
force caused by propeller affect the estimated
forces acting on hull.
The effect of propeller loading condition on
forces acting on hull
The hydrodynamic forces acting on hull
are affected by propeller’s loading condition.
Table 3.2 shows the relation between the hydrodynamic forces acting on hull and propeller loading conditions. The hydrodynamic
forces acting on hull measured in the condition of bare hull and in condition of propeller
and rudder equipped are shown. The propeller
loading are ship point and model point.
Table 3.2 Estimated Hydrodynamic coefficients Esso Osaka (Model ship length 2.5 m).
without
Propeller
Ship point Model point
X'vv 0.0216 0.0401 0.0150
X' vr–my 0.1905 0.1830 0.1946
X’rr 0.0122 0.0138 0.0116
X' vvvv 0.2743 0.1419 0.3172
Y'v -0.3786 -0.3718 -0.3838
Y'r–mx 0.0435 0.0572 0.0613
Y'vvv -1.2231 -1.3804 -1.2312
Y'vvr 0.1485 -0.0341 0.0128
Y'vrr -0.3070 -0.2713 -0.2882
Y'rrr 0.0441 0.0014 0.0092
N' v -0.1439 -0.1432 -0.1456
N'r -0.0577 -0.0560 -0.0578
N' vvv  0.0120 -0.0004 0.0049
N' vvr -0.2164 -0.2534 -0.2407
N' vrr 0.0657 0.0331 0.0341
N'rrr -0.0081 -0.0138 -0.0115
Error of towing speed
When CMT is carried out, the velocity of
each towing carriage is controlled based on
calculated velocity. As the motion characteristic of each towing carriage is different, actual
motion of each carriage cannot realize the calculated motion. Error of towing speed makes
the affect on the measuring hydrodynamic
force.
Figure 3.1 shows one example of the relation between the turn rate and combined speed
of tawing carriage.
Table 3.3 shows corrected hydrodynamic
forces based on the characteristics of towing
carriage motions and measured ones. The hydrodynamic coefficients concerning turn rate
(r) are changed.
588 The Specialist Committee on Esso Osaka
23rd International
Towing Tank
Conference
-0.010
0.00
0.010
0.020
0.030
-25 -20 -15 -10 -5 0 5 10 15 20 25
Rate of turn(deg/s)
Error of towing speed
(m/s)
Figure 3.1 The characteristics of towing carriage in CMT.
Table 3.3 Hydrodynamic coefficients measured by CMT (Model ship length 2.5 m).
Motion: Midship
Moment: Midship
Corrected
Hydrodynamic
Forces
Measured
Hydrodynamic
Forces
X'vv 0.0216 0.0378
X' vr–my 0.1905 0.1834
X’rr 0.0122 0.0178
X' vvvv 0.2743 0.1753
Y'v -0.3786 -0.3793
Y'r–mx 0.0435 0.0331
Y'vvv -1.2231 -1.2419
Y'vvr 0.1485 0.0162
Y'vrr -0.3070 -0.2521
Y'rrr 0.0441 0.0563
N' v -0.1439 -0.1438
N'r -0.0577 -0.0613
N' vvv 0.0120 0.0095
N' vvr -0.2164 -0.2217
N' vrr 0.0657 0.0555
N'rrr -0.0081 -0.0045
3.4. Conclusions
It has not been possible to explain the very
large differences in forces calculated using
hydrodynamic coefficients reported by the
22nd ITTC Maneuvering Committee. There
are many possible sources of differences, but
no primary sources have been clearly identified. 15 to 20 years after most tests Esso
Osaka tests were carried out, raw data are
largely unavailable and many of those responsible for tests and data analysis are no longer
active. It is therefore concluded that the reasons for the large observed data scatter must
remain largely undefined.
4. DISCUSSION ON THE TRIAL AND
FREE RUNNING MODEL TEST
4.1. Full scale trial
The potential inaccuracies of any ship trials data are well recognized. These inaccuracies arise from the difficulty in correcting
measured results for effects of temporally and
spatially varying wind, current and waves and
inaccuracies in basic measurements such as
ship position. The special maneuvering Esso
Osaka trials of 1979 were planned and carried
out with unusual care, but available sensors
technology at that time was relatively unsophisticated, particularly the pre-GPS equipment used to record ship track. Finally, deep
water trials were carried out at a mean water
depth-to-draft ratio of 4.2, where bottom effects could exist, and water depth was not
constant in the shallow water trials despite the
great effort taken to select trials locations
where water depth was nearly constant.
Table 4.1 shows the main contents of sea
trial in deep water conditions. Figure 4.1
shows the turning trajectory with right rudder
angle 35 degrees and Figure 4.2 shows the
results of 10/10 zigzag maneuver.
23rd International
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Proceedings of the 23rd ITTC – Volume II 589
4.2. Free running model tests
The measured turning motion of free running models was used in evaluating the accuracy of simulations. Three sets of free running
model turning motion test results were available to be used. Two sets of tests were carried
out using models of 2.5 m in length and one
was carried out using a model of 4.6 m in
length.
Table 4.1 Main contents of Sea Trial (deep
water condition).
Type of
Trial
Rudder angle or
Rudder/heading angle
(deg)
Speed of
Approach
(knots)
Turning
maneuver
35, left rudder 7
Turning
maneuver
35, right rudder 7,10
Coasting
turning
maneuver
35, left rudder 5
Zigzag
maneuver
20/20 7
Coasting
Zigzag
maneuver
20/20 5
Zigzag
maneuver
10/10 7
Mean trajectories for these 3 models are
shown in Figure 4.3. A mean trajectory was
defined by calculating the mean X position at
every unit position on Y axis or by calculating
mean Y position at every unit position on X
axis. The results for the initial stage of turning
show significant differences, although steady
turning radii are nearly identical, ranging from
2.45L to 2.48L. The reasons for the difference
in initial turning shown in Figure 4.3 are not
clear. Therefore, the mean trajectory of the 3
tests was used as a baseline turning motion for
free running model tests.
0 2 4
0
2
4
X/L
Y/L
Trials
a. The turning trajectory in Trial
0 10 20 30
0
0.2
0.4
0.6
0 10 20 30
0
0.5
1
0 10 20 30
0
10
20
r'(
rL /U
O
)
dr ift
in g an gl e( de g) U
/U
o t'=tUo/L
trials
b. The time history on ship’s speed, drifting angle
and rate of turn
Figure 4.1 The result of turning maneuver in
trial.
590 The Specialist Committee on Esso Osaka
23rd International
Towing Tank
Conference
0 10 20 30
–20
0
20
0 10 20 30
–0.5
0
0.5
0 10 20 30
0.7
0.8
0.9
1
0 10 20 30
–10
0
10
ru dd er a ng le (d eg )
he ad in g an gl e( de g) ra te o f t
ur n (r L/
U
o) U
/U
o dr ift
in g an gl e( de g) t'=tUO/L
trials
Figure 4.2 Zigzag maneuver in Trial (10/10
Zigzag).
0 2 4
0
2
4
mean
2.5m
4.6m
2.5m
X/L
Y/L
Figure 4.3 The turning trajectory in free running model test (rudder angle +35°).
5. SIMULATION STUDIES ON MMG
MODEL
5.1. Mathematical model on MMG
Basic equation of motion
The mathematical model used in this study
is shown below.





−=
=+
=−
YxNrI
Ymurvm
Xmvrum
Gzz &
&
&
(5.1)
where:
the origin of maneuvering motion is at the
center of gravity of the ship;
the origin of hydrodynamic force is at the
midship section on the centerline of the ship.
m: mass of a ship, Izz: moment of inertia of
yawing, X, Y and N are hydrodynamic forces
and moment acting on midship. xG represents
the location of C.G. in x-axis direction from
the midship.
These hydrodynamic forces and moments
can be divided into the following components.





++=
++=
++=
RPH
RPH
RPH
NNNN
YYYY
XXXX
(5.2)
where subscripts H, P and R refer to hull, propeller and rudder, respectively. Interaction
between hull and propeller and among hull,
propeller and rudder are contained in forces
and/or moment with subscript P and R.
Hydrodynamic forces and moment acting on
the hull
Hydrodynamic forces and yaw moments
acting on the hull are as follows:
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Proceedings of the 23rd ITTC – Volume II 591
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vvvv
2
rr yvr
2
vvxH
'v'X'r'X
'r'vm'X'v'XXumX'
++
−++′′′−= )( (0)&
3
rrr
2
vrr
2
vvr
3
vvvxrvyH
'r'Y'r'v'Y'r'v'Y
'v'Y'r'm'Y'v'Y'v'm'Y
+++
+−++−= )( &
3
rrr
2
vrr
2
vvr
3
vvvrvZZH
'r'N'r'v'N'r'v'N
'v'Nr'N'v'N'r'J'N
+++
+++−= &
(5.3)
X(0) are measured from resistance test.
Hydrodynamic forces induced by propeller
The hydrodynamic forces induced by the
propeller are expressed as below:
TPP
KtnDTtX )(1)(1 24 −=−= ρ (5.4)
2
321 JaJaaKT ++= (5.5)
P
P
nD u J = (5.6)
)1( PP wuu −= (5.7)
where t: thrust deduction factor, n: propeller revolution, DP: propeller diameter, J: propeller advance ratio, a1, a2 and a3: constant for
propeller open characteristics
On wake fraction 1−wP, various estimation
formulas are proposed. Following two
mathematical models were used in this study.
[model 1]
2'
2
'
10 )'()'()(11 rlkrlkJww PwPwPPP −+−+−=− ββ
(5.8a)
2
2100 )(1 PwPwwPP JaJaaJw ++=− (5.9)
[model 2]
2'''
0 )''('')1(1 rxvCrxvww PPPPP ++++−=− τ (5.8b)
Hydrodynamic force and yaw moment induced by rudder
The hydrodynamic forces induced by rudder are described below, in terms of rudder
normal force FN, rudder angle δ, and rudder to
hull interaction coefficients tR, aH, xH:
δsin)1( NRR FtX −−= (5.10a)
δcos)1( NHR FaY +−= (5.10b)
δcos)( NHHRR FxaxN +−= (5.10c)
5.2. Hydrodynamic forces acting on hull
As stated previously, hydrodynamic coefficients can have different values as a result of
differences of experimental condition, analysis procedures and mathematical models used.
The effect of these issues on the data being
considered here cannot be quantified. Therefore, it is not meaningful to compare the different sets of data directly.
Data from four sets of tests for which detailed information were available for consideration. The hydrodynamic coefficients obtained from these four sets of tests using different procedures, were unified to a single set
of test conditions and the unified data were
used to simulate maneuvering of the Esso
Osaka.
The experimental conditions for the four
selected tests are shown in Table 5.1. Bare
hull hydrodynamic coefficients derived from
the test results, unified to the same test conditions, are shown in Table 5.2. Longitudinal
hydrodynamic forces for the 4 model ships are
shown in Figure 5.1. Lateral force and yawing
moment are shown in Figure 5.2 and Figure
5.3. In Table 5.2 and in all figures showing
hydrodynamic forces, mean hydrodynamic
coefficients, and resulting mean hydrodynamic forces, calculated using each of the 4
models, are also shown.
Longitudinal forces, X', for the 4 model
shown in Figure 5.1 show similar tendency for
small drift angles and turning rates. With
large yaw rate and drift angle or sway rate, the
hydrodynamic forces show significant differences. Lateral force, Y', shows a similar tendency but with smaller difference than those
for X'. Yaw moment, N', also shows similar
tendency, with the differences between the 4
sets of hydrodynamic forces increase as the
combined yaw and sway rates increase.
592 The Specialist Committee on Esso Osaka
23rd International
Towing Tank
Conference
Table 5.1 Experimental conditions.
Research Institute A B C D
Length of model ship 6.0 m 4.6 m 4.0 m 2.5 m
Kind of test C.M.T. C.M.T. C.M.T. C.M.T.
Model ship speed
Froude Number
0.699 m/s, Fn=0.0912 0.611 m/s, Fn=0.0910 0.400 m/s, Fn=0.0639 0.450 m/s, Fn=0.0911
Revolution of propeller ship point model point bare hull model point
appendages Propeller, rudder Propeller, rudder none Propeller, rudder
Measured items
Hull forces, propeller thrust,
rudder normal forces
Hull forces, propeller
thrust, rudder normal
forces
Hull forces
Hull forces, propeller thrust,
rudder normal forces
Captive point C.G. C.G. C.G. C.G.
The measurement center of
the yaw moment
Mid Ship C.G. C.G. Mid Ship
Freedom of ship motion
Fore: pitching Free
Aft.: pitching & surging Free
Free to pitching, rolling
Free to pitching, heave,
rolling Free to pitching, rolling
Experimental range
O.T: β=±0÷30°
CMT: r'=±0÷1.0
Coupling motion range at CMT
(r'= 0÷0.8, β=-20÷20.0°)
(r'=0÷-0.8, β=-20÷20.0°)
O.T: β=±0÷30°
CMT: r'=±0÷0.5
Coupling motion range at
CMT
(r'= 0÷0.8, β= 0÷30°)
(r'= 0÷-0.8, β= 0÷-30°)
O.T: β=±0÷20°
CMT: r'=±0÷0.8
Coupling motion range at
CMT
(r'=0÷0.8, β=0÷20.0°)
(r'=0÷-0.8, β=0÷20.0°)
O.T: β=±0÷25°
CMT: r'=±0÷0.8
Coupling motion range at
CMT
(r'= 0÷0.8, β= -5÷17.5°)
(r'=0÷-0.8, β=5÷-17.5°)
While the different methods of captive
model test and different analyzing procedures
were done, we can compare the unified values
by coherent converting way concerning the
contents. As a result, it is clarified that the
scattering among them are small. In next section, the effects of the varieties in data on the
estimation of motion are discussed.
0 0.2 0.4 0.6
–0.003
–0.002
–0.001
0
0.001
6.0m 4.6m
4.0m 2.5m
mean data
r' X
' H
=X
H
/0
.5
ρ
L2
U
2
β =0
β =5
β =10
β =15
β =20
β =30
β =25
Figure 5.1 Longitudinal force (X'H).
0 0.2 0.4 0.6
0
0.01
0.02
0.03
0.04
6.0m 4.6m
4.0m 2.5m
mean data
Y
' H
=
Y
H
/0
.5
ρ
L2
U
2
r' β =30
β =25
β =15
β =10
β =20
β =5
β =0
Figure 5.2 Lateral force (Y'H).
0 0.2 0.4 0.6
–0.002
0
0.002
0.004
6.0m 4.6m
4.0m 2.5m
mean data
r' N
' H
=
N
H
/0
.5
ρ
L3
U
2
β =0
β =5
β =10
β =15
β =20
β =30
β =25
Figure 5.3 Yaw moment (N'H).
23rd International
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Proceedings of the 23rd ITTC – Volume II 593
Table 5.2 Hydrodynamic coefficients.
6.0 m 4.6 m 4.0 m 2.5 m Mean data
Motion C.G. C.G. C.G. C.G. C.G.
Moment Mid Ship Mid Ship Mid Ship Mid Ship Mid Ship
Propeller revolution Ship point Model point ― Model point ―
appendages
Propeller &
rudder
Propeller &
rudder
― Propeller &
rudder

X'vv -0.01046 -0.01046 -0.00344 0.00489 -0.00329
X'vvvv 0.33753 0.22216 0.22750 0.33705 0.277875
X'rr 0.00388 0.00337 -0.00962 0.00250 3.4E-05
X'vr+my' 0.19490 0.17073 0.16046 0.24980 0.183616
Y'v -0.33231 -0.37003 -0.36152 -0.38348 -0.3831
Y'r–mx' 0.07543 0.11050 0.06934 0.07330 0.082145
Y'vvv -1.23856 -1.08291 -1.40179 -1.22775 -1.05375
Y'vvr 0.16712 0.40898 0.15960 0.13322 0.59837
Y'vrr -0.37771 -0.48898 -0.39704 -0.29181 -0.25589
Y'rrr 0.02868 -0.11900 0.02742 0.01818 -0.01119
N'v -0.13800 -0.13974 -0.13282 -0.14540 -0.14716
N'r -0.04779 -0.04485 -0.04758 -0.05323 -0.04836
N'vvv 0.02644 0.02736 -0.14675 0.00449 0.053257
N'vvr -0.29422 -0.33238 -0.26843 -0.23498 -0.29699
N'vrr 0.04047 -0.00461 0.02922 0.04983 0.023637
N'rrr -0.01673 -0.02493 -0.01903 -0.01268 -0.01835
Non-dimensional forms: 22
2
1
2
1
LdU/Y'Y,LdU/X'X HHHH ρρ == ,
22dUL
2
1
/N'N HH ρ=
5.3. Estimation on ship’s motion
Estimation using original proposed data
For studying the effect of different hydrodynamic forces acting on hull, the forces
caused by propeller and rudder were estimated
using the following mathematical model, designated PR model-1, and the associated coefficients given in Table 5.3.
Table 5.3 The coefficient in (PR model-1).
1–wP0 τ C'P x'P k ε
0.386 0.871 -0.359 -0.517 0.288 1.420
594 The Specialist Committee on Esso Osaka
23rd International
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Conference
(PR model-1)
2)()(11 'rx'vC'rx'vww 'P
'
P
'
P0PP ++++−=− τ
(5.10)
1)81( 2 −++= J/Kk
u u T
P
R πε (5.11)
)( 'r'l'vv RR += γ (5.12)
)(tan)( 10 RRR uv
−+−= δδα (5.13)
RRRN UfAF αρ α sin2
1 2= (5.14)
2
RRR vuU +=
2 (5.15)
(1) Predicted turning motion
The turning motions estimated using the 4
sets of originally proposed coefficients are
shown in Figure 5.4. Turning trajectories are
shown in Figure 5.4.a and ship’s velocity,
drift angle and non-dimensional rate of turn
are shown in Figure 5.4.b. Mean results from
free-running model tests are also shown in
Figures 5.4.a and 5.4.b. All simulated turning
trajectories are similar, and the simulated initial turning motions are smaller than the
measured initial turning motion. Simulated
advances with the different data sets have differences of –0.5% to 2.7% from that simulated using the mean hydrodynamic coefficients, while estimated steady turning diameters have differences of –0.6% to 3.3% from
those for the mean hydrodynamic coefficients.
(2) Zigzag test
In Figure 5.5, results for a simulated 15-15
zigzag maneuver results and results for this
maneuver obtained from free running tests of
a 6.0 m model are presented. The results include rudder angle, turning angle, ship’s speed
and drift angle. Up to the second overshoot,
all simulated results are similar and all are in
good agreement with the free running test results.
The difference among the results estimated by using data from each institute shows
very small. Concerning the varieties on the
results of free running model test, it is difficult to judge whether the data proposed by
different institute is good or bad.
0 2 4
0
2
4
Free run(mean)
Original data 6.0m
Original data 2.5m
Original data4.6m
Original data 4.0m
mean data
X/L
Y/L
a. The turning trajectory (rudder angle +35°)
0 10 20 30
0
0.2
0.4
0.6
0 10 20 30
0
0.5
1
0 10 20 30
0
10
20
r'(
rL /U
O
)
dr ift
in g an gl e (d eg )
U
/U
o t'=tUo/L
Free run(2.5m)
Original data 6.0m Original data 4.6m
Original data 4.0m Original data 2.5m
mean data
b. The time history on ship’s speed, drifting
angle and rate of turn ( rudder angle +35°)
Figure 5.4 The estimation of turning motion
estimated by using the hydrodynamic coefficients of each institute.
23rd International
Towing Tank
Conference
Proceedings of the 23rd ITTC – Volume II 595
The effect of variety of estimated hydrodynamic forces on motion estimation
It is clarified in previous studies that the
effect of difference of estimated hydrodynamic forces shows small. In this section, the
effect on simulated motions of changes in an
individual hydrodynamic force component, X,
Y or N, is discussed.
0 100
–40
–20
0
20
40
0 50 100 150
–2
0
2
0 50 100 150
0.5
0.6
0.7
0 50 100 150
–10
0
10
ru dd er a ng le (d eg )
ra te o f t
ur n( de g/ se c) sh ip 's v el oc ity
(m /s )
dr ift
in g an gl e( de g) Time(sec)
he ad in g an gl e( de g) Free run(6.0m) 6.0m 4.6m
4.0m 2.5m mean data
Figure 5.5 The Zigzag maneuver estimated
by using the hydrodynamic coefficients of
each institute (15/15 Zigzag).
(1) Effect of individual forces on turning
motion
(A) The effect of difference in longitudinal
force
The effect on simulated results of the difference in the surge force, X, proposed by
each institute was studied by conducting
simulations in which Y and N were defined to
have the mean values for all data. The resulting trajectories are shown in Figure 5.6.a and
time histories of ship’s speed, drift angle and
turn rate are shown in Figure 5.6.b.
0 2 4
0
2
4
Free run(maen)
6.0m
2.5m
4.6m
4.0m
mean data
X/L
Y/L
a. The turning trajectory (rudder angle +35°)
0 10 20 30
0
0.2
0.4
0.6
0 10 20 30
0
0.5
1
0 10 20 30
0
10
20
r'(
rL /U
O
)
dr ift
in g an gl e (d eg )
U
/U
o t'=tUo/L
Free run(2.5m)
6.0m 4.6m
4.0m 2.5m
mean data
b. The time history on ship’s speed, drifting
angle and rate of turn ( rudder angle +35°)
Figure 5.6 The turning motion estimated by
using X'H each institute (Y'H, N'H: mean data
of each institute are used).
596 The Specialist Committee on Esso Osaka
23rd International
Towing Tank
Conference
The differences in X, as shown in Figure
5.1, make no significant difference in turning
motion. The maximum difference of turning
diameter simulated using the four different X
forces and the mean hydrodynamic coefficients, the maximum difference of estimated
diameter of turning circle is 3.2%, it is very
small. For every set of X force data the simulated rate of turn in steady turning motion is
smaller than that measured in the free running
model tests.
(B) The effect of difference in lateral force
The effect on simulated results of the difference in the surge force, Y, proposed by each
institute was studied by conducting simulations
in which X and N were defined to have the
mean values for all data. The resulting trajectories are shown in Figure 5.7.a, and time histories of ship’s speed, drift angle and turn rate are
shown in Figure 5.7.b. The differences in Y, as
shown in Figure 5.2, make no significant difference in drift angle or in turning motion. The
difference of Yv among the institutes are 13.0%
to -0.5% comparing to mean value and the difference of Yr–mx are 15.0% to -35.0%. The
maximum difference of the advances and turning diameters simulated using the four different
Y forces and the mean values of Y are -0.5% to
-0.8% and -0.2% to 0.8%, respectively. For
every set of Y force data the simulated rate of
turn in steady turning motion is smaller than
that measured in the free running model tests.
(C) The effect of difference of estimated
turning moment
The effect on simulated results of the difference in the yawing moment, N, proposed
by each institute was studied by conducting
simulations in which X and Y were defined to
have the mean values for all data. The resulting trajectories are shown in Figure 5.8.a and
time histories of ship’s speed, drift angle and
turn rate are shown in Figure 5.8.b. Although
the differences in N, as shown in Figure 5.3
make no significant difference in turning motion, the turning trajectories show larger differences than do those obtained with different
values of X and Y.
0 2 4
0
2
4 Free run(mean)
6.0m
2.5m
4.6m
4.0m
mean data
X/L
Y/L
a. The turning trajectory (rudder angle +35°)
0 10 20 30
0
0.2
0.4
0.6
0 10 20 30
0
0.5
1
0 10 20 30
0
10
20
r'(
rL /U
O
)
dr ift
in g an gl e( de g) U
/U
o t'=tUo/L
Free run(2.5m)
6.0m 4.6m
4.0m 2.5m
mean data
b. The time history on ship’s speed, drifting
angle and rate of turn ( rudder angle +35°)
Figure 5.7 The turning motion estimated by
using Y'H each institute (X'H, N'H: mean data
of each institute).
23rd International
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Proceedings of the 23rd ITTC – Volume II 597
The difference of Nv among the institutes
are 9.5% to 1.0% comparing to mean value
and the difference of Nr are 7.0% to -10.%.
The maximum difference of the advances and
turning diameters simulated using the four
different Ns and the mean values are -0.6% to
3.0% and -2.3% to 2.8%, respectively.
(2) Effect of individual force on zigzag
motion
(A) The effect of difference of estimated
longitudinal force
In this section, the effects of difference of
longitudinal force X on the zigzag motion estimation are discussed. For this study, the effects
of using the X proposed by each institute are discussed, using the mean values of Y and N. Time
histories of rudder angle, turning angle, ship’s
speed and drifting angle are shown in Figure 5.9.
The use of the different values of X of Figure 5.1
has no significant effect on zigzag motions, and
all results show good agreement with free running model test results up to 2nd overshoot.
Comparing to the estimated 1st and 2nd overshoot angles of 5.4 degree and 10.1 degree obtained using mean values of all hydrodynamic
coefficients, the different values of X gave values of 5.1 to 5.8 degrees for the 1st overshoot
angle and 10.7 to 10.8 degree for the 2nd overshoot angle. These differences are small.
(B) The effect of difference of estimated
lateral force
In this section, the effects of difference of lateral force Y on the zigzag motion estimation are
discussed. For this study, the effects of Y proposed by each institute are discussed. X and N
defined by mean of them are applied. The time
histories of rudder angle, turning angle, ship’s
speed and drifting angle are shown in Figure 5.10.
The difference of estimated Y makes big effects
on the estimation of overshoot angle and drifting
angle. Comparing to the estimated 1st and 2nd
overshoot angle by using mean hydrodynamic
coefficients that are 5.4 degree and 10.1 degree,
the range of estimated 1st overshoot angle is 5.1
to 6.5 degree and the range of estimated 2nd overshoot angle is 9.4 to 12.5 degree.
0 2 4
0
2
4
Free run(mean)
6.0m
2.5m
4.6m
4.0m
mean data
X/L
Y/L
a. The turning trajectory (rudder angle +35°)
0 10 20 30
0
0.2
0.4
0.6
0 10 20 30
0
0.5
1
0 10 20 30
0
10
20
r'(
rL /U
O
)
dr fit
in g an gl e( de g) U
/U
o t'=tUo/L
Free run(2.5m)
6.0m 4.6m
4.0m 2.5m
mean data
b. The time history on ship’s speed, drifting angle
and rate of turn ( rudder angle +35°)
Figure 5.8 The turning motion estimated by
using N'H each institute (X'H, Y'H: mean data
of each institute).
598 The Specialist Committee on Esso Osaka
23rd International
Towing Tank
Conference
0 50 100 150
–40
–20
0
20
40
0 50 100 150
–2
0
2
0 50 100 150
0.5
0.6
0.7
0 50 100 150
–10
0
10
ru dd er a ng le (d eg )
ra te o f t
ur n( de g/ se c) sh ip 's v el oc ity
(m /s )
dr ift
in g an gl e( de g) Time(sec)
he ad in g an gl e( de g) Free run(6.0m) 6.0m 4.6m
4.0m 2.5m mean data
Figure 5.9 The Zigzag maneuver estimated
by using X'H each institute (15/15 Zigzag)
(Y'H, N'H: mean data of each institute).
(C) The effect of difference of estimated
turning moment
In this section, the effects of difference of
turning moment N on the motion estimation are
discussed. For this study, the effects of N proposed by each institute are discussed. X and Y
defined by mean of them are applied. The time
histories of rudder angle, turning angle, ship’s
speed and drifting angle are shown in Figure
5.11. The difference of estimated N shown in
Figure 5.3 dose not make big difference on
zigzag motion and they show similar estimation up to 2nd overshoot. And they show good
agreement to free running model test up to 2nd
overshoot angle. Comparing to the estimated
1st and 2nd overshoot angle by using mean hydrodynamic coefficients that are 5.4 degree and
10.1 degree, the range of estimated 1st overshoot angle is 5.0 to 5.7 degree and the range
of estimated 2nd overshoot angle is 9.3 to 10.5
degree. It is small.
0 100
–40
–20
0
20
40
0 100
–2
0
2
0 100
0.5
0.6
0.7
0 50 100 150
–10
0
10
ru dd er a ng le (d eg )
ra te o f t
ur n( de g/ se c) sh ip 's v el oc ity
(m /s )
dr ift
in g an gl e( de g) Time(sec)
he ad in g an gl e( de g) Free run(6.0m) 6.0m 4.6m
4.0m 2.5m mean data
Figure 5.10 The Zigzag maneuver estimated
by using Y'H each institute (15/15 Zigzag)
(X'H, N'H: mean data of each institute).
As the stability index is defined by certain
Y and N coefficients, the change of Y make the
change of stability index rather than the change
of N. Values of Yv for the four sets of data
differ by 13.0% to -0.5% from the mean
value of Yv and values of Yr–mx differ by
15.0% to -35.0% from the mean value. Values of Nv and Nr differ from the mean values by
9.5% to 1.0% and 7.0% to -10.0%, respectively.
The stability index obtained using the
original hydrodynamic coefficients proposed
by the four institutes differ by 32.0% to -23.0%
from those obtained using the mean coeffi 23rd International
Towing Tank
Conference
Proceedings of the 23rd ITTC – Volume II 599
cients. The range of stability obtained using
only individual values of Y differ widely from
the mean, by 52.0% to -24.0%. The range of
stability indexes due to use of different values
only of N is 0% to -26.0%. Therefore, Y forces
have a significantly larger effect on stability
index than does yaw moments, N. By this reason, the estimated zigzag motions based on the
change of Y show bigger scattering rather than
ones based on the change of N. Figure 5.12
shows the relation between stability index of
bare hull and 1st overshoot angle. The range of
stability index due to use of different Y shows
wider range than that due to change of N. The
accuracy of the Y forces thus has a big effect on
the stability index and the accuracy of simulated zigzag motion.
0 50 100 150
–40
–20
0
20
40
0 50 100 150
–2
0
2
0 50 100 150
0.5
0.6
0.7
0 50 100 150
–10
0
10
ru dd er a ng le (d eg )
ra te o f t
ur n( de g/ se c) sh ip 's v el oc ity
(
m /s )
dr ift
in g an gl e( de g) Time(sec)
he ad in g an gl e( de g) Free run(6.0m) 6.0m 4.6m
4.0m 2.5m mean data
Figure 5.11 The Zigzag maneuver estimated
by using N'H each institute (15/15 Zigzag)
(X'H, Y'H: mean data of each institute).
–0.2 –0.15 –0.1
5
6
7
–0.2 –0.15 –0.1
5
6
7
–0.2 –0.15 –0.1
5
6
7
1s t O
ve rs ho ot a ng le (d eg )
Stability index (bare hull condition)
The hydrodynamic derivatives
1s t O
ve rs ho ot a ng le (d eg )
The derivatives of Y'H prposed by the institute
1s t O
ve rs ho ot a ng le (d eg )
(6.0M)
(mean data)
(4.0M) (2.5M)
(4.6M)
(6.0M)
(4.0M)
(2.5M)
(mean data)
(4.6M)
(mean data)
(4.6M)
(6.0M)
(2.5M)
(4.0M)
Stability index (bare hull condition)
Stability index (bare hull condition)
proposed by each institute
X'H,N'H mean derivatives
The derivatives of N'H prposed by the institute
X'H,Y'H mean derivatives
Figure 5.12 The relation between the 1st
overshoot angle and stability index.
5.4. Hydrodynamic forces due to
propeller, rudder and
hull/propeller/rudder interactions
Formulas on Hydrodynamic forces caused by
propeller and rudder
Several mathematical models for propeller,
rudder and interaction forces have been proposed by different institutes. In this section, the
effect on simulated motions of the mathematical model used to predict propeller, rudder and
interaction forces is discussed. For this purpose, model PR model-1, which was discussed
earlier, and a second model, PR model-2,
which is described below, have been used.
600 The Specialist Committee on Esso Osaka
23rd International
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(PR model-2)
2
210 )()()(11 'rlk'rlkJww
'
Pw '
PwPPP −+−+−=− ββ
(5.16)
2
2100 )(1 PwPwwPP JaJaaJw ++=− (5.17)
)(11)}
8
1({1)(1 2 η
π
η −+−++−=
2
T
R
R
J
K
kw u u (5.18)
2
210 )()(11 'rlk'rlkww
'
Pw '
PwRR −+−+−=− ββ
(5.19)
)(11 00 PR ww −−= ε (5.20)
U
u v RRR δ=− (5.21)
RR δδα += (5.22)
RRRN sinUfAF αρ α
2
2
1= (5.23)
22
RRR vuU += (5.24)
The turning motion simulated using PR
model-1 and PR model-2 are shown in Figure
5.13.a. Maximum advance and steady turning
diameter estimated using PR model-1 are
3.12L and 2.38L, respectively. Those estimated using PR model-2 are 3.01L and 2.71L.
Those measured in free running model test are
2.94L and 2.46L. Figure 5.13.b shows rudder
normal force, longitudinal inflow velocity at
rudder position and effective inflow angle calculated using both models. The initial stage of
turning is estimated different. The differences
in the simulated results are due to both the
details of the mathematical model and the empirical constants used with each model.
Flow straightening constant
One of specific characteristics of MMG
model is to express the hydrodynamic forces
caused by propeller and rudder and interaction
among hull, propeller and rudder correctly
based on the hydrodynamic phenomenon.
There are several constant in the PR model-1
mentioned above. The flow straightening constant γ has an important effect on rudder force.
0 2 4
0
2
4
Free run(mean)
6.0m
2.5m
4.6m
4.0m
mean data
X/L
Y/L
a. The turning trajectory (rudder angle +35°)
0 10 20 30
0
0.2
0.4
0.6
0 10 20 30
0
0.5
1
0 10 20 30
0
10
20
r'(
rL /U
O
)
dr fit
in g an gl e( de g) U
/U
o t'=tUo/L
Free run(2.5m)
6.0m 4.6m
4.0m 2.5m
mean data
b. The time history on rudder normal force,
inflow velocity at rudder and effective rudder
angle (rudder angle +35°).
Figure 5.13 The turning motion estimated by
PR-model-1 and PR-model-2.
23rd International
Towing Tank
Conference
Proceedings of the 23rd ITTC – Volume II 601
0 2 4
0
2
4
Free run(mean) Original (γ =0.4080)
γ =0.4488 (+10%)
γ =0.5304(+30%)γ =0.4896 (+20%)
X/L
Y/L 0 2 4
0
2
4
Free run(mean) original (γ =0.4080)
γ =0.3692 (–10%)
γ =0.2856(–30%)γ =0.3264 (–20%)
X/L
Y/L
a. The turning trajectory (γ increase) b. The turning trajectory (γ decrease)
0 100 200
0
1
2
0 100 200
0.4
0.6
0.8
0 100 200
0
10
20
30
F
N
(k g) u R
(m /s )
α
R
(d eg )
Original γ =0.4080
γ =0.4896 (+20%)
γ =0.4488 (+10%)
γ =0.5304 (+30%)
Time (sec)
0 100 200
0
1
2
0 100 200
0.4
0.6
0.8
0 100 200
0
10
20
30
F
N
(k g) u R
(m /s )
α
R
(d eg )
Original γ =0.4080
γ =0.3264(–20%)
γ =0.3692(–10%)
γ =0.2856(–30%)
time(sec)
c. The time history on rudder normal force,
inflow velocity at rudder and effective rudder
angle (γ increase)
d. The time history on rudder normal force,
inflow velocity at rudder and effective rudder
angle (γ decrease)
Figure 5.14 The estimation accuracy of γ on turning motion.
602 The Specialist Committee on Esso Osaka
23rd International
Towing Tank
Conference
Figure 5.14 shows the relation between the
turning motion and flow straightening constant. Simulated turning trajectories for incremental increases of 10.0% in the value of γ
are shown in Figure 5.14.a and those for
10.0% decreases in the value of γ are shown
in Figure 5.14.b. In Figures 5.14.c and 5.14.d,
the time histories on rudder normal force,
longitudinal flow velocity at the rudder position and effective inflow angle to the rudder
are shown. A change in γ results in a change
in inflow angle and rudder normal force. The
value of γ determines the motion at both the
initial stage and steady stage of turning. The
effect on turning of the investigated changes
of γ is much larger than the effect of the differences in hydrodynamic coefficients.
Constant used with PR model-2
In this section, the effects of element in
(PR model-2) are discussed by following
methods.
(1) (1–wP0): wake fraction at propeller and
propeller loading condition
(PR model-2) express that propeller loading condition affects the change of wake fraction at propeller position. We discussed this
effect provided that other effects are taken
into account. It means that the changes of
wake fraction at propeller and rudder position
are taken into account.
(2) (1–wP): wake fraction at propeller and
drifting and yawing condition
(PR model-2) express that drifting and
yawing condition affects the change of wake
fraction at propeller position. We discussed
this effect provided that the following conditions are taken into account. It means that the
changes of wake fraction at rudder position
are taken into account and wake fraction at
propeller position is not affected by propeller
loading condition.
0 2 4
0
2
4
Free run(mean)
6.0m
2.5m
4.6m
4.0m
mean data
X/L
Y/L
a. The turning trajectory (rudder angle +35°)
0 10 20 30
0
0.2
0.4
0.6
0 10 20 30
0
0.5
1
0 10 20 30
0
10
20
r'(
rL /U
O
)
dr fit
in g an gl e( de g) U
/U
o t'=tUo/L
Free run(2.5m)
6.0m 4.6m
4.0m 2.5m
mean data
b. The time history on propeller thrust, inflow
velocity at rudder and rudder normal force
(rudder angle +35°).
Figure 5.15 The influence of mathematical
model of 1–wP on the turning motion.
23rd International
Towing Tank
Conference
Proceedings of the 23rd ITTC – Volume II 603
Figure 5.15 shows the results of comparison mentioned above. The estimated result
containing all of factors in (PR model-2) is
also indicated in Figure 5.15. Propeller loading condition in wake fraction at propeller affect small change in motion estimation. On
the other hand, when wake fraction at propeller position is assumed as constant during
maneuvering motion, propeller advance ratio
J is constant. Then the rudder effect is
overestimated caused by overestimating
longitudinal inflow velocity at rudder
position: uR. Figure 5.15.b shows these situations.
The change of wake fraction due to maneuvering motion has an important effect on
propeller and rudder forces and on simulated
maneuvering motions.
5.5. Conclusions
The results of available captive model
tests reflect differences in experiment condition, mathematical model used, etc. However
we can compare hydrodynamic forces proposed by different institutes by unifying them
by correcting for differences in test conditions. After such unification, simulated results
with the different data show small differences
in simulated maneuvering motion. The scattering of results is small because the various
institutes understood the concept of the MMG
model and thus carried out coherent experiment and analysis of data.
For the future direction, we would like to
point out that it is important to carry out experiments and data analysis using a unified
approach, and essential to clearly define test
conditions and analysis procedures when attempting to compare results from different
institutes.
6. SIMULATION STUDIES ON WHOLE
SHIP MODEL
As a part of benchmark study, comparative
simulations of Esso Osaka tanker have been
done with selected datasets of ‘whole ship
model’ type mathematical model. There are
many available datasets of whole ship model
type mathematical model which have been
submitted to ITTC committee. But it is found
that most of them are not suitable for simulation study in this time because of insufficient
information on their data and mathematical
model. For full simulation, some need further
data and some mathematical are not clear.
There are also some datasets which are believed to have typographic errors. Therefore,
it is not easy to reproduce same simulation
results with their original results using only
submitted information. For this reason, only
three datasets from KRISO (Korea Research
Institute of Ships & Ocean Engineering),
HSMB (Hydronautics Ship Model Basin) and
SNU (Seoul National University) are selected
as reference datasets.
This section presents the comparison between simulation results by three different
models and full-scale trial data. Hydrodynamic
forces predicted by three models are also compared each other at the range of motion variables experiencing during standard maneuvers.
6.1. Mathematical models and PMM test
results
Mathematical models of ship maneuvering
motion, PMM test conditions and hydrodynamic coefficients from three organization are
summarized here. All definition of notations
and nondimensionalization follows ITTC convention.
604 The Specialist Committee on Esso Osaka
23rd International
Towing Tank
Conference
KRISO
The mathematical model of KRISO are as
follows (Kim, 1988 ).
[ ]
[ ]
[ ]
(Thrust))Resistance(
)1(
)1(
)1(
)(
2
2
2
2
+−
−++
−++
−++
+=−−
rXX
rXX
vXX
vrXuXrxvrum
rrrr
vvvv
vruG
η
η
η
δδηδδ
η
η
&& &
(6.1)
[ ]
[ ]
[ ]
[ ]
[ ]δη
η
η
η
η
η
δηδ
η
η
η
η
η
)1(
||
||)1(
||)1(
)1(
)1(
)1()(
||
2
||||
||||
−++
++
−++
−++
−++
−++
++−+=+−
YY
vrYvrY
rrYY
vvYY
rYY
vYY
rYvYYYrxurvm
vrvrr
rrrr
vvvv
rr vv rvooG &&&& &&
2
|| || vYY vv δδδ δδδ ++ (6.2)
[ ]
[ ]
[ ]
[ ]
[ ]
2
||
||
||||
||||
||
)1(
||
)1(
||)1(
)1(
)1(
)1()(
2
vNN
NN
vrNvrN
rNN
vvNN
rNN
vNNrN
vNNNurvmxrI
vv vrvrr
rrrr
vvvv
rr vvr
vooGz
δδδ
δη
η
η
η
η
η
δδδ
δηδ
η
η
η
η
η
++
−++
++
−++
−++
−++
−+++
+−+=++
&
&&&
&
&
(6.3)
where (Resistance) and (Thrust) are measured
from the resistance test and propeller open
water and self propulsion test.
KRISO has conducted HPMM tests using a
model ship with a length of 6.5 m in the towing
tank whose dimensions are 200 m × 16 m × 7 m.
All the tests were carried out with fully appended model and with the propeller operating
at the ship propulsion point.
Test programs are summarized in Table
6.1 and Table 6.2. Hydrodynamic coefficients
of KRISO are summarized in Table 6.3. Here,
all the force coefficients are taken with the
origin at the ship center of gravity.
Table 6.1 Static Test Program of KRISO.
Type
Drift
Angle
(deg)
Rudder
Angle
(deg)
Model
Speed
(m/s)
η
0 0,±5,±10,15,
20,25,30,35
0.509 1.0
0 0,±5,±10,15,
20,25,30,35
0.364 1.4
0 0,±5,±10,15,
20,25,30,35
0.255 2.0
0 0,±10,20,30 0.364 1.0
0 0,±10,20,30 0.364 0.0
0 0,±10,20,30 0.364 -1.0
Speed
&
Rudder
0 0,±10,20,30 0.364 -2.0
0,±2,±4,6,8,1
2,16,24
0 0.509 1.0
0,±2,±4,6,8,1
2,16,24
0 0.509 0.0
0,±2,±4,6,8,1
2,16,24
0 0.364 1.4
Static
Drift
0,±2,±4,6,8,1
2,16,24
0 0.255 2.0
2 0,±10,20,30 0.509 1.0
4 0,±10,20,30 0.509 1.0
8 0,±10,20,30 0.509 1.0
Drift
&
Rudder
12 0,±10,20,30 0.509 1.0
Table 6.2 Dynamic Test Program of
KRISO.
Type
Drift
Angle
(deg)
Rudder
Angle
(deg)
Model
Speed
(m/s)
η
0 0,±5,±10,15,
20,25,30,35
0.509 1.0
0 0,±5,±10,15,
20,25,30,35
0.364 1.4
0 0,±5,±10,15,
20,25,30,35
0.255 2.0
0 0,±10,20,30 0.364 1.0
0 0,±10,20,30 0.364 0.0
0 0,±10,20,30 0.364 -1.0
Speed
&
Rudder
0 0,±10,20,30 0.364 -2.0
0,±2,±4,6,8,1
2,16,24
0 0.509 1.0
0,±2,±4,6,8,1
2,16,24
0 0.509 0.0
0,±2,±4,6,8,1
2,16,24
0 0.364 1.4
Static
Drift
0,±2,±4,6,8,1
2,16,24
0 0.255 2.0
2 0,±10,20,30 0.509 1.0
4 0,±10,20,30 0.509 1.0
8 0,±10,20,30 0.509 1.0
Drift
&
Rudder
12 0,±10,20,30 0.509 1.0
23rd International
Towing Tank
Conference
Proceedings of the 23rd ITTC – Volume II 605
Table 6.3 Hydrodynamic coefficients of KRISO.
Coefficient Value×105 Coefficient Value×105 Coefficient Value×105
'X u& -138.5 'Yv& -1423.5 'Nv& -29.1
'Yr& 39.7 'Nr& -47.5
'X vv 0. 'Yv -1930.9 'Nv -761.2
'Y |v|v -4368.1 'N |v|v 118.2
'X rr 133.1 'Yr 561.4 'Nr -322.0
'X vr 1530.1 'Y |r|r 206.5 'N |r|r -113.6
'Xδδ -134.0 'Yδ 326.7 'Nδ -147.6
'X vδ -148.6 'Y ||δδ 0. 'N ||δδ 0.
'Yvrr -3428.2 'Nvrr 338.2
'Y |v|r 321.8 'N |v|r -361.7
'Y vvδ -2281.3 'N vvδ -109.9
'Yo 2.0 'No -1.0
'X vvη 0. 'Yvη -349.2 'Nvη -28.7
'Y |v|v η 0. 'N |v|v η 24.1
'X rrη 0. 'Yrη 54.7 'Nrη -9.6
'Y |r|r η 0. 'N |r|r η 0.
'Xδδη -158.7 'Yδη 411.4 'Nδη -163.7
'Yoη 2.0 'Noη -1.0
606 The Specialist Committee on Esso Osaka
23rd International
Towing Tank
Conference
HYDRONAUTICS
The mathematical model of Hydronautics
are as follows (Hydronautics, 1980).
[ ]
[ ]
[ ]
[ ]
[ ]222
222
22
24
32
'
2
2
)1(''
2
'
2
)|sin|'|cos|'('
2
)(
δρ
ηηρ
ηρ
ρ
ββ
ρ
η
RUDp
iii
vvvv
rr uvru
G
XuL
cbauL
vXXL
rXL
vrXXuX
Lrxvrum
+
+++
−++
+
−+
=−−
&& &
&
(6.4)
[ ]
( )
( ) ( )
( )[ ]
[ ]'
2
'
2
)/'(
2
1||'1'
||''
2
||'
1'''
2
||''
2
)(
*
22
2224
||
||2
||
3
||
4
YwL
YuLUvrYL
vvYuvY
vvYuvY
L
rvY
urYurYvY
L
rrYrYLrxurvm
p RUDpvrr
vvv
vvv
rv rrv
rrrG
ρ
δρρ
ηη
ρ
ηρ
ρ
ηη
η
+
++








−+−+
+
+








+
−++
+
+=++
&
&&&
&
&
(6.5)
[ ]
[ ]
[ ]
( )[ ] [ ]'NwLρ'δNuLρ
)'v|v|(ηN
)'uv(ηN'v|v|N'uvN
L
ρ
/U'vrNL
ρ
'|v|rN)'ur(ηN'urNLρ
|)}
rL u |({
'r|r|Nr'N
L
ρ
v'NL
ρ
ur)v(mxrI
*pRUDp
v|v|η
vηv|v|v
Rvrr
|v|rrηr
r|r|r
vGz
2323
3
25
4
5
4
22
1
1
2
2
1
2
2
tanh1212
2
++








−+
−++
+
+
+−++










−+
+
+
=−+
&
&&&
&
&
(6.6)
Hydronautics conducted HPMM tests using a
model ship with a length of about 24 ft in the towing
tank whose dimension is 128 m × 7.6 m × 3.9 m.
All the tests were carried out with fully appended
model and with the propeller operating at the ship
propulsion point.
Hydronautics have carried out HPMM
tests at three depths. But, only the data at deep
water will be shown here. Test programs and
hydrodynamic coefficients are summarized in
Tables 6.4, 6.5 and in Table 6.6 respectively.
Here, all the force coefficients are defined at
the ship center of gravity.
Table 6.4 Static Test Program of Hydronautics.
Type
of Test
Drift
Angle
(deg)
Rudder
Angle
(deg)
Model
Speed
(m/s)
η
Propulsion 0 0
0.557,
0.944
1.0
Static
Drift
-
2,0,2,4,
6,8,12,
16,20
0
0.557,
0.944
0,
1.0,
2.0
Static
Rudder
0
-5,5,10,15,
20,25,30,35
0 ±∞
Rudder
and
Drift
2,4,6,8,
12,16,
20
-35,-30,-25,
-20,-15,-10,
-5,5,10,15,
20,25,30,35
0.944 1.0
Table 6.5 Dynamic Test Program of Hydronautics.
Type
of Test
Drift
Angle
(deg)
Rudder
Angle
(deg)
Model
Speed
(m/s)
η
Propulsion 0 0
0.557,
0.944
1.0
Static
Drift
-
2,0,2,4,
6,8,12,
16,20
0
0.557,
0.944
0,
1.0,
2.0
Static
Rudder
0
-5,5,10,15,
20,25,30,35
0 ±∞
Rudder
and
Drift
2,4,6,8,
12,16,
20
-35,-30,-25,
-20,-15,-10,
-5,5,10,15,
20,25,30,35
0.944 1.0
23rd International
Towing Tank
Conference
Proceedings of the 23rd ITTC – Volume II 607
Table 6.6 Hydrodynamic Coefficients of Hydronautics.
Coefficient Value Coefficient Value Coefficient Value
'X u& -0.00105 'Nv& -0.00025 1a -0.0005844
'X vr 0.0417 'Nr& -0.00091 1b -0.0006599
'X vv 0.0035 'Nr -0.00353 1c 0.001244
1<η<∞
rr'X 0.0003 |'r|rN -0.00069 2a -0.00085
'Xδδ -0.00135 'Nv -0.007867 2b 0.000138
'X vvη 0.0021 'N |v|v 0.0 2c 0.000712
0≤η<1
'Yv& -001746 'Nrη -0.00028 3a -0.00085
'Yr& -0.00071 'Nvη 0.000505 3b -0.00002984
'Yr 0.00595 2vr
N 0.003571 3c -0.0009475
-1≤η<0
|'r|rY 0.0023 'N∗ 0.0 4a -0.0007343
'Yv -0.02048 'Nδ -0.001985 4b 0.0002685
|v|vY -0.03377 |v|'N δ 0.0 4c -0.0007766
-∞≤η<-1
'Yrη 0.00060 |v|r'N -0.0034 d 0.33
'Yvη -0.00105 e 0.32
'Yvvη 0.0 f 0.077
'Yvrr -0.0156 |v|r'Y 0.0075 wa 0.0
'Y∗ 0.0 wb 0.42
'Yδ 0.003953 |v|Yδ 0.0 wc 0.10
Table 6.7 Hydrodynamic Coefficients by SNU.
Coefficient Value Coefficient Value Coefficient Value
'm'X u −& -0.021170 'm'Yv −& -0.033162 'Nv& 0.000127
'Yr& -0.000638 'I'N zr −& -0.001738
'X vv 0.002127 'Yv -0.24418 'Nv -0.007665
'Yvvv 0.095876 'N vvv -0.004756
'X rr -0.002770 'm'Yr − -0.011914 'Nr -0.003774
'Yrrr -0.010450 'Nrrr -0.000594
'm'X vr + 0.028172 'Yvvr 0.024019 'Nvvr -0.021079
'X vvrr 0.033843 'Yvrr -0.010450 'Nvrr 0.002357
'X ee -0.001497 'Y 0 0.005675 'N0 0.000193
'Yδ 0.003908 'Nδ -0.001745
'Yeee 0.000519 'Neee -0.000026
608 The Specialist Committee on Esso Osaka
23rd International
Towing Tank
Conference
SNU
The mathematical model of SNU are as
follows (Rhee, Key. P., et al., 1993).
[ ] [ ]
[ ]
[ ] )()( ResistanceThruste'XcL
2
U/rv'Xr'XL
2
v'XL
2
vrXu'XL
2
)vru(m
2
ee 22
222
vvrr
2
rr 4
2
vv 2
'vru
3
−++
++
++=−
ρ
ρ
ρρ
&& &
(6.10)
[ ] [ ]
[ ] [ ]
[ ] [ ]
[ ]
[ ] [ ]
[ ]
[ ]322
2
0
2
224
23
353
322
34
'
2
})2/)(({'
2
)2/('
2
'/
2
'/
2
'/
2
'
2
'/
2
'
2
'
2
'
2
)(
2
eYcL
crLvccYL
UYLvrYUL
rvYUL
rYULrYUL
vYULvYUL
vYLrYLurvm
eee
Aovrr
vvr
rrrr
vvvv
vr ρ
δδρ
ρρ
ρ
ρρ
ρρ
ρρ
δ
+
+−−−+
++
+
++
++
+=+

&&& &&
(6.11)
[ ] [ ]
[ ] [ ]
[ ] [ ]
[ ] [ ]
[ ]323
2325
2436
433
345
'
2
)2/('
2
'/
2
'/
2
'/
2
'
2
'/
2
'
2
'
2
'
2
eNcL
UNLvrNUL
rvNULrNUL
rNULvNUL
vNULvNLrNLrI
eee
Aovrr
vvrrrr
rvvv
vvrz
ρ
ρρ
ρρ
ρρ
ρρρ
+
++
++
++
++=

&&& &&
))
2
)(({[
2
2
0
'3 δδρ δ c
rL vccNL +−−−+
(6.12)
where
[ ]crLve )2(tan 1 −−= −δ
streamdown far velocity inducedpropeller ;
)1)(1(})1{(
)(8)1()1(
streamdown far velocity inducedpropeller ;
0
222
222
c uRkUuRc
nDKuu
U
prApr
T
A
ωω
πωω
−−++−=
+−+−−=


rppr AAR
D
=
diameterpropeller ;
fraction wake;
racepropeller in rudder of area projected;
rudder of area projected;
ω
p r A
A
velocityinducedpropeller ;
tcoefficienthrust propeller ;
A
AA
T
U
UUk
K
∞=
SNU has conducted HPMM tests using a
model ship with a length of 6.5 m in the towing
tank whose dimension is 200 m × 14 m × 6 m.
All the tests have been carried out with fully
appended model and with the propeller operating at the ship propulsion point. Test programs are almost same with that of KRISO.
Hydrodynamic coefficients of SNU are summarized in Table 6.7. Here, all the force coefficients are taken with the origin at the ship
center of gravity.
Comparison of mathematical model and test
conditions
Mathematical models of KRISO, HSMB
and SNU are basically same. Major differences are just in representing non-linear
damping terms and propeller slip stream effects. SNU adopts cubic forms in representing
non-linear damping terms while KRISO and
HSMB adopts both square and cubic terms.
KRISO models propeller slip stream effects
simply just by introducing a ship propulsion
ratio η. HSMB and SNU use more complicated models to represent propeller slip
stream effects. They use different forms but
basic idea of their modeling is same in that
they model the velocity into the rudder based
on propeller theory.
All three organizations carried out HPMM
tests with a relatively large model and in a
sufficiently large towing tank. So we can assume that all the test results have same scale
effects and blockage effects. But HSMB performs test at the rather higher velocity than
KRISO. So this might give some differences
in force measurements due to Reynolds number effects. Test programs are very similar
except a few tests. HSMB have carried out
rudder and drift test for wider range of drift
angles while KRISO have carried out yaw and
drift test for wider range of drift angles.
23rd International
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Proceedings of the 23rd ITTC – Volume II 609
6.2. Simulations
Using the mathematical models and hydrodynamic coefficients of three organizations
described in the previous section, simulations
of maneuvering have been made for an Esso
Osaka tanker and the results are compared
with trial data.
The results of simulation for 35 degree
starboard and port turning are shown in Figures 6.1÷6.8. The agreement between trials
and simulations by three models is good.
There are some differences in yaw rate at the
early stage of turning where turning rate has a
peak value. Simulation by HSMB predicts
higher yaw rate than the trial data but simulations by KRISO and SNU underpredict. Simulation by HSMB shows higher yaw rate all the
time. HSMB predicts the smallest turning circle and SNU predicts the largest turning circle.
Predicted drift angles show very large differences. SNU predicts final drift angles as 24
degrees but KRISO as 12 degree. At present,
it is not certain which is better prediction. Although the trial data of drift angles are shown
in the figures, they are too contaminated by
current to refer.
The results of simulation for 10o/10o and
20o/20o zigzag maneuver are shown in Figures
6.9÷6.16. Generally simulations by three
models show good agreements with trial data.
Overshoot angles are well predicted although
simulation predicts a little time lagged motion. HSMB predicts much slower drop of
forward speed than trial data. But the original
simulation results made by HSMB shows
much closer results with trial data (Barr,
1993). These differences seem to be errors in
reproducing the simulations done in this
study. Contrast to turning, three models predict drift angles not so different.
To relate predicted motions with hydrodynamic coefficients, predicted forces during
maneuvering motions are examined. Figure
6.17 and Figure 6.18 show typical range of
motion variables during turning and zigzag
maneuvers respectively. A ship experiences
the largest yaw rate and drift angle at the indicated stages shown in these figures. Prediction
of hydrodynamic forces at these stages would
affect the prediction of maneuvering motions
critically. The largest motion can be observed
in the steady stage of 35 degree turning where
the speed drop ratio, the drift angle and nondimensional yaw velocity are 0.35, 18 degree
and 0.9 respectively. In the zigzag maneuver,
the largest motion can be observed at the second phase of 20o/20 o zigzag maneuver.
Figures 6.19÷6.24 show the comparison of
the predicted forces by three models over the
range of turning and zigzag maneuver shown
in Figure 6.17 and Figure 6.18. Generally the
predicted yaw moments by three models show
good agreements compared with side forces.
Over the range of typical zigzag maneuver,
three models predict almost same both side
forces and yaw moments. But predicted forces
show large differences over the range of turning motion. Especially, side forces show
much larger differences. The large differences
of drift angles seen in Figure 6.4 and Figure
6.8 are attributed to these differences.
The main cause of the difference in side
forces at the large yaw rate and large drift angle is can be found in hydrodynamic coefficients, Yvrr, Yv|r|. The values of Yvrr, Yv|r| by
KRISO are –0.03428 and 0.00321 while those
by HSMB are –0.0156 and 0.0075. There can
be many sources making this difference. The
model test conditions of KRISO and HSMB
including the size of towing tank and model,
propulsion condition and test procedure are
very similar. Just the test program for Yaw
and Drift test shows a little difference. KRISO
have carried out this test up to the drift angle
of 16 degree while HSMB up to 12 degree.
And HSMB carried out this test at the higher
speed of 0.944 m/sec while KRISO at the
lower speed of 0.504 m/sec. Analyzing
method would also affect the results. But, unfortunately, all of these cannot be confirmed
further at present because both raw model test
data are not available.
610 The Specialist Committee on Esso Osaka
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Conference
Transfer(m)
A
d va n ce (m )
0 250 500 750 1000 1250 1500
0
250
500
750
1000
1250
KRISO
HSMB
SNU
Trial
35 deg. Starboard Turn (10.0kts)
Figure 6.1 Trajectory for 35o Starboard
turning (V = 10.0 kts).
T im e (se c)
Y
aw R
at e( d eg /s ec )
0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0
0
0 .0 5
0 .1
0 .1 5
0 .2
0 .2 5
0 .3
0 .3 5
0 .4
0 .4 5
0 .5
K R IS O
H S M B
S N U
T ria l
3 5 d e g . S ta rb o a rd T u rn (1 0 .0 k ts )
Figure 6.2 Time history of yaw rate for 35o
Starboard turning (V = 10.0 kts).
T im e (se c)
S
pe ed (k ts )
0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0
0
1
2
3
4
5
6
7
8
9
1 0
K R IS O
H S M B
S N U
T ria l
3 5 de g . S ta rbo a rd T u rn (1 0 .0 kts)
Figure 6.3 Time history of speed for 35°
Starboard turning(V = 10.0 kts).
T im e (s e c )
D
rif
ta n g le (d eg )
0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0
0
5
1 0
1 5
2 0
2 5
3 0
K R IS O
H S M B
S N U
3 5 d e g . S ta rb o a rd T u rn ( 1 0 .0 k ts )
Figure 6.4 Time history of drift angle for 35o
Starboard turning (V = 10.0 kts).
Transfer(m)
A
d va nc e( m )
-1500 -1250 -1000 -750 -500 -250 0
0
250
500
750
1000
1250
KRISO
HSMB
SNU
Trial
35 deg. Port Turn (7.7kts)
Figure 6.5 Trajectory for 35o Port turning
(V = 7.7 kts).
T im e (se c)
Y
aw R
at e( d eg /s ec )
0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0
-0 .3 5
-0 .3
-0 .2 5
-0 .2
-0 .1 5
-0 .1
-0 .0 5
0
K R IS O
H S M B
S N U
T ria l
3 5 d e g . P o rt T u rn (7 .7 kts)
Figure 6.6 Time history of yaw rate for 35o
Port turning (V = 7.7 kts).
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T im e (se c)
S
p ee d (k ts )
5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0
0
1
2
3
4
5
6
7
8
9
1 0
K R IS O
H S M B
S N U
T ria l
3 5 de g. P ort T urn (7 .7 kts)
Figure 6.7 Time history of speed for 35o
Port turning (V = 7.7 kts).
T im e ( s e c )
D
rif
ta ng le (d eg )
5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0
-3 0
-2 5
-2 0
-1 5
-1 0
-5
0
K R IS O
H S M B
S N U
T ria l
3 5 d e g . P o rt T u rn ( 7 .7 k ts )
Figure 6.8 Time history of drift angles for
35o Port turning (V = 7.7 kts).
T im e ( se c )
H
ea di n g A
ng le (d eg )
0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0
-3 0
-2 5
-2 0
-1 5
-1 0
-5
0
5
1 0
1 5
2 0
2 5
3 0
K R IS O
H S M B
S N U
T ria l
1 0 - 1 0 Z ig - Z a g M a n e u v e r( 7 .5 k ts )
Figure 6.9 Time history of heading angles
for 10o/10o Zigzag maneuver (V = 7.5 kts).
T im e (s e c )
Y
aw R
at e( de g/ se c) 0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0
-0 .2
-0 .1 5
-0 .1
-0 .0 5
0
0 .0 5
0 .1
0 .1 5
0 .2
0 .2 5
K R IS O
H S M B
S N U
T ria l
1 0 -1 0 Z ig -Z a g M a n e u ve r(7 .5 k ts )
Figure 6.10 Time history of yaw rate for
10°/10° Zigzag maneuver (V = 7.5 kts).
T im e ( s e c )
S
p ee d (k n o ts )
0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0
4
5
6
7
8
K R IS O
H S M B
S N U
T ria l
1 0 - 1 0 Z ig - Z a g M a n e u v e r( 7 .5 k ts )
Figure 6.11 Time history of speed for 10o/10o
Zigzag maneuver (V = 7.5 kts).
T im e ( s e c )
D
rif
tA ng le (d eg )
0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0
- 8
- 4
0
4
8
1 2
K R IS O
H S M B
S N U
T ria l
1 0 - 1 0 Z ig - Z a g M a n e u v e r( 7 .5 k ts )
Figure 6.12 Time history of drift angles for
10°/10° Zigzag maneuver (V = 7.5 kts).
612 The Specialist Committee on Esso Osaka
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T im e ( s e c )
H
ea d in g A
ng le (d eg .)
0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0
-4 0
-3 0
-2 0
-1 0
0
1 0
2 0
3 0
4 0
K R IS O
H S M B
S N U
T ria l
2 0 -2 0 Z ig -Z a g M a n e u v e r(7 .8 k ts )
Figure 6.13 Time history of heading angles
for 20°/20° Zigzag maneuver (V = 7.8 kts).
T im e ( se c)
N
o n d im en si o n al Y
aw R
at e 0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0
-0 .2
-0 .1
0
0 .1
0 .2
0 .3
K R IS O
H S M B
S N U
T ria l
2 0 -2 0 Z ig -Z a g M a n e u v e r( 7 .8 k ts )
Figure 6.14 Time history of yaw rate for
20°/20° Zigzag maneuver (V = 7.8 kts).
T im e ( s e c )
S
p ee d (k n o ts )
0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0
4
5
6
7
8
K R IS O
H S M B
S N U
T ria l
2 0 - 2 0 Z ig - Z a g M a n e u v e r( 7 .8 k ts )
Figure 6.15 Time history of speed for 20°/20°
Zigzag maneuver (V = 7.8 kts).
T im e ( s e c )
D
ri ft A
n g le (d eg )
0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0
-1 5
-1 0
-5
0
5
1 0
1 5
2 0
K R IS O
H S M B
S N U
T ria l
2 0 - 2 0 Z ig - Z a g M a n e u v e r( 7 .8 k ts )
Figure 6.16 Time history of drift angles for
20o/20o Zigzag maneuver (V = 7.8 kts).
Time(sec)
Y
aw R
at e( d eg /s ec )
0 500 1000 1500 2000
0
0.1
0.2
0.3
0.4
0.5
0.6
Initial Turning Stage
starbd. turn : u'=0.8 ,δ=-35, β=12, r'=0 .6
port turn : u'=0 .8,δ=35, β=-12, r'=-0 .6
S teady Turning Stage
starbd. turn : u'=0.35,δ=-35, β=18, r'=0 .9
port turn : u'=0.35,δ=35, β=-18, r'=-0 .9
Figure 6.17 Typical values of motion variables during turning maneuver.
Time(sec)
Y
aw R
at e( de g/ se c) 0 500 1000 1500
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
1st phase
10/10, u'=1.0,δ=-10, β=3.5, r'=0.15
20/20, u'=0.95.,δ=-20, β=7, r'=0.3
2nd phase
10/10, u'=0.95,δ=10, β=-6, r'=-0.3
20/20, u'=0.8.,δ=20, β=-10, r'=-0.4
Figure 6.18 Typical values of motion variables during Zigzag maneuver.
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r' Y
'
-1.5 -1 -0.5 0 0.5 1 1.5
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
KRISO, δ= -35.0 β= 12.0
HSM B, δ= -35.0 β= 12.0
SNU, δ= -35.0 β= 12.0
KRISO, δ= 35.0 β= -12.0
HSM B, δ= 35.0 β= -12.0
SNU, δ= 35.0 β= -12.0
35o stbd turn, initial stage
35o port turn, initial stage
Figure 6.19 Side forces at the initial turning
stage.
r' N
'
-1.5 -1 -0.5 0 0.5 1 1.5
-0.005
0
0.005
0.01
KRISO, δ= -35.0 β= 12.0
HSM B, δ= -35.0 β= 12.0
SNU, δ= -35.0 β= 12.0
KRISO, δ= 35.0 β= -12.0
HSM B, δ= 35.0 β= -12.0
SNU, δ= 35.0 β= -12.0
35o stbd turn, initial stage
35o port turn, initial stage
Figure 6.20 Yaw moments at the initial turning stage.
r' Y
'
-1.5 -1 -0.5 0 0.5 1 1.5
-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
0.04
0.05
KRISO, δ= -35.0 β= 18.0
HSMB,δ= -35.0 β= 18.0
SNU,δ= -35.0 β= 18.0
KRISO, δ= 35.0 β= -18.0
HSMB,δ= 35.0 β= -18.0
SNU,δ= 35.0 β= -18.0
35o stbd turn,steady stage
35o port turn, steady stage
Figure 6.21 Side forces at the steady turning
stage.
r' N
'
-1.5 -1 -0.5 0 0.5 1 1.5
-0.015
-0.01
-0.005
0
0.005
0.01
0.015
0.02
KRISO, δ= -35.0 β= 18.0
HSM B,δ= -35.0 β= 18.0
SNU,δ= -35.0 β= 18.0
KRISO, δ= 35.0 β= -18.0
HSM B,δ= 35.0 β= -18.0
SNU,δ= 35.0 β= -18.0
35o stbd turn,steady stage
35o port turn, steady stage
Figure 6.22 Yaw moments at the steady turning stage.
r' Y
'
-1.5 -1 -0.5 0 0.5 1 1.5
-0.02
-0.015
-0.01
-0.005
0
0.005
0.01
0.015
0.02
0.025
KR ISO, δ= -10.0 β= 3.5
HSMB,δ= -10.0 β= 3.5
SNU,δ= -10.0 β= 3.5
KR ISO, δ= 10.0 β= -6.0
HSMB,δ= 10.0 β= -6.0
SNU,δ= 10.0 β= -6.0
10o/10o 1st phase
10o/10o 2nd phase
Figure 6.23 Side forces during Zigzag motions.
r' N
'
-1.5 -1 -0.5 0 0.5 1 1.5
-0.005
0
0.005
0.01
KR ISO, δ= -10.0 β= 3.5
HSMB,δ= -10.0 β= 3.5
SNU,δ= -10.0 β= 3.5
KR ISO, δ= 10.0 β= -6.0
HSMB,δ= 10.0 β= -6.0
SNU,δ= 10.0 β= -6.0
10o/10o 1st phase
10o/10o 2nd phase
Figure 6.24 Yaw moments during Zigzag motions.
614 The Specialist Committee on Esso Osaka
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6.3. Benchmark data based on selected
datasets of a whole ship model
As it is shown in the foregoing, the selected three datasets of a whole ship model
gives a reasonable prediction of full maneuvering performance comparable with full
scale trial data. So, their mean value of hydrodynamic coefficients can be proposed as one
of benchmark data for the study of maneuvering performance of Esso Osaka tanker.
Since three datasets are derived based on
different mathematical model and with different analyzing method, all datasets need to be
reanalyzed with same method to have same
expressional forms. To reanalyze three datasets, artificial PMM data are generated using
programs which have been used in comparative study. The ranges of generated datasets
are determined to cover the range of full scale
trials. And, new hydrodynamic coefficients of
three datasets are derived with same analyzing
method. Table 6.8 and Table 6.9 summarize
the coefficients of each dataset and mean
value of them in square form and cubic form,
respectively. Here, the mean values are obtained by analyzing all three datasets together.
The residual errors shown in tables represent
the difference of each datasets from mean
value. These errors can be, therefore, thought
as scattering of hydrodynamic coefficients
among three datasets. Hydrodynamic coefficients concerned with static drift and pure
yaw shows small scattering. But large residual
errors are observed as expected.
Using mean data in Table 6.1 and Table
6.2, prediction of full scale maneuvering performances are made and compared with trial
data. Some other data which are not shown in
tables but necessary data for simulation are
adopted from datasets of KRISO. Figures
6.13-6.16 shows the results. They show reasonable prediction but a little worse results
compared with ones shown in chapter 5.
6.4. Summary
Comparative simulation study of Esso
Osaka tanker have been done using three
datasets of deep water which were derived
based on a mathematical model of a whole
ship model. All the simulation results by three
models generally show good agreements with
full-scale trial data. But it is found that each
model shows much different prediction of hydrodynamic forces for large yaw rate and drift
angles although they predict hydrodynamic
forces almost the same over the typical motion range of turning and zigzag maneuver.
But large difference in predicting side forces
for the large yaw rate and drift angles results
in the large difference of predicting drift angles. To predict the hard maneuvering motion
which may occur either from large deflection
of rudder or the inherent instability of a ship,
more careful experimental design and analysis
of nonlinear coupling hydrodynamic coefficients are required.
As a benchmark data of hydrodynamic
coefficients for whole ship model, mean data
of three datasets are suggested. Simulated
results using benchmark data show reasonable
prediction but a little worse results compared
with ones shown in chapter 5.
23rd International
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Table 6.8 Summary of Hydrodynamic Coefficients for Benchmark data (square form).
Coeffs. KRISO HSMB SNU Mean
Rresidual
(r.m.s)
Residual
(max)
Relative
Error(r.m.s)
Xvv 0.00085 0.00348 0.00255 0.00229 0.00001 0.00017 11.5%
Xrr 0.00133 0.00030 -0.00286 -0.00041 0.00015 0.00245 26.8%
Xvr 0.03347 0.02175 0.02846 0.02789 0.00004 0.00348 6.7%
Xdd -0.00135 -0.00137 -0.00038 -0.00103 0.00002 0.00025 17.7%
Yv -0.01953 -0.02071 -0.02279 -0.02101
Yv|v| -0.04030 -0.03018 -0.02791 -0.03278
0.00003 0.00073 0.5%
Yr 0.00562 0.00595 0.00669 0.00579
Yr|r| 0.00608 0.00230 -0.00204 0.00218
0.00003 0.00029 0.7%
Yd 0.00329 0.00400 0.00382 0.00370
Yd|d| -0.00005 -0.00003 -0.00001 -0.00003
0.00002 0.00025 1.7%
Yv|r| -0.02677 -0.01209 -0.00965 -0.01618
Yr|v| -0.01311 0.00663 0.00599 0.00079
0.00007 0.00739 7.5%
Nv -0.00763 -0.00794 -0.00884 -0.00814
Nv|v| 0.00220 0.00133 0.00353 0.00236
0.00001 0.00017 0.4%
Nr -0.00321 -0.00351 -0.00365 -0.00346
Nr|r| -0.00115 -0.00074 -0.00062 -0.00084
0.00001 0.00008 0.4%
Nd -0.00150 -0.00198 -0.00173 -0.00173
Nd|d| 0.00005 -0.00005 0.00005 0.00002
0.00002 0.00017 2.4%
Nv|r| 0.00275 0.00287 0.00326 0.00296
Nr|v| 0.00048 -0.00290 -0.00567 -0.00268
0.00002 0.00149 4.3%
Table 6.9 Summary of Hydrodynamic Coefficients for Benchmark data (cubic form).
Coeffs. KRISO HSMB SNU Mean
Residual
(r.m.s)
Residual
(max.)
Relative
Error(r.m.s)
Yv -0.02213 -0.02271 -0.02442 -0.02312
Yvvv -0.12176 -0.08995 -0.08511 -0.09791
0.00004 0.00130 0.6%
Yr 0.00608 0.00646 0.00623 0.00632
Yrrr 0.00189 0.00212 -0.00182 0.00188
0.00004 0.00051 0.8%
Yd 0.00328 0.00399 0.00382 0.00370
Yddd -0.00005 -0.00003 -0.00003 -0.00004
0.00025 0.00002 1.7%
Yvrr -0.03165 -0.01367 -0.01044 -0.01867
Yrvv -0.00390 0.02061 0.02172 0.00331
0.00006 0.00608 4.3%
Nv -0.00750 -0.00786 -0.00766 -0.00767
Nvvv 0.00656 0.00390 0.00929 0.00659
0.00001 0.000169 0.4%
Nr -0.00347 -0.00367 -0.00378 -0.00364
Nrrr -0.00105 -0.00068 -0.00058 -0.00076
0.00001 0.00014 0.5%
Nd -0.00149 -0.00199 -0.00172 -0.00173
Nddd 0.00008 -0.00005 0.00008 0.00004
0.00002 0.00017 2.4%
Nvrr 0.00338 0.00358 0.00237 0.00310
Nrvv 0.00222 -0.00917 -0.01954 -0.00891
0.00002 0.00143 1.8%
616 The Specialist Committee on Esso Osaka
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7. CONCLUSION
Esso Osaka Specialist Committee in 23rd
ITTC was requested to discuss the proposed
data estimated by captive model test and to
propose the benchmark data. Committee discussed the reasons of scattering in proposed
data and decided to study the data that we can
know the detail experimental and analyzing
procedures. Committee made several studies
based on simulation on trial and free running
model test. Finally, committee proposed the
benchmark data relating to 2 kinds of mathematical model.
Esso Osaka trial data include some results
in shallow water condition. Committee tried
to discuss the data, but we could not get sufficient data by mean of insufficient information
on experiments and analyzing procedures. Finally, committee concluded to discuss the issues in deep water condition.
For benchmark data the conclusions are:
MMG model
The hydrodynamic forces proposed by different institutes show little difference from
view point of comparing the scattering in results of free running model test. Therefore, we
propose to use the mean data as defines
herein, as a benchmark data set for hydrodynamic coefficients. We cannot make enough
discussion on the forces concerning propeller
and rudder because we can correct small number of them. However, as the estimated results
show good agreement to the results of free
running model tests, we propose the data
shown in this paper as benchmark corresponding to individual mathematical model.
Whole Ship model
The mean value of hydrodynamic coefficients
of three selected data sets, summarized in Table 6.8 and Table 6.9 at chapter 6, are proposed as a benchmark data for the study of
maneuvering performance of Esso Osaka
tanker for a mathematical model with whole
ship model type. On the propeller-rudder interaction model, there might be some arguments but KRISO model is proposed because
it is simpler.
8. REFERENCES
Abkowitz, M.A., 1984, “Measurement of Ship
Hydrodynamic Coefficients in Maneuvering from Simple Trials During Regular
Operation”, Massachusetts Institute of
Technology Report MIT-OE-84-1.
Barr, R., 1993, “A Review and Comparison of
Ship Maneuvering Simulation Methods”,
Transactions of the SNAME, Vol. 101.
Crane, C.L., jr., 1979a, “Maneuvering Trials
of the 278,000 DWT Esso Osaka in Shallow and Deep Water”, Transactions of the
SNAME, Vol. 87, pp. 251-283.
Crane, C.L., Jr., 1979b, “Maneuvering Trials
of the 278,000 DWT Esso Osaka in Shallow and Deep Water”, Exxon International
Company Report EII.4TM.79.
Dand, I.W., and Hood, D.B., 1983 “Maneuvering Experiments Using Two Geosims
of the Esso Osaka”, National Maritime
Institute (NMI) Report No. NMI R168.
Hydronautics, 1980, “Model Test and Simulation Correlation Study Based on the Full
Scale ESSO OSAKA Maneuvering Data”,
Hydronautics report No. 8007-1.
Kim, S.Y., 1988, “Development of Maneuverability Prediction Technique”, KIMM Report No. UCE.337-1082.D.
MMG, 1985, “Prediction of Manoeuvrability
of A Ship”, Bulletin of the Society of Naval Architects of Japan, Published by The
Society of Naval Architects of Japan.
Rhee, K.P., Ann, S.P., Ryu, M.C., 1993,
“Evaluation of Hydrodynamic Derivatives
23rd International
Towing Tank
Conference
Proceedings of the 23rd ITTC – Volume II 617
from PMM Test by System Identification”,
Proceedings of MARSIM ’93.
Roseman, D.P., Editor, 1987, “The MARAD
Systematic Series of Full-Form Ship Models”, Published by the SNAME, New
York, NY, USA.
Webster, W.C., Editor, 1992, “Shiphandling
Simulation − Application to Waterway Design”, Published by the National Academy
Press, Washington, DC, USA.
Yoshimura, Y., 2001, “A study on Hydrodynamic derivatives and interaction coefficients”, Maneuverability Prediction Group
2001, Report No. Map 8-5.
23rd International
Towing Tank
Conference
Proceedings of the 23rd ITTC – Volume III 739
I. DISCUSSIONS
I.1. Discussion on the Report of the 23rd
ITTC Specialist Committee on Esso
Osaka: Manoeuvring in shallow
water
By: Masayoshi Hirano, Mitsui Akishima
Laboratory, Japan
First of all, as a member of former ITTC
Manoeuvring Committee, I would like to congratulate the committee on this fine report.
The committee members must have done very
laborious work. I would like to make a couple
of comments as follows.
1. Theoretical approach
Nowadays CFD technique has greatly
been improved and practical applications are
widely being attempted not only in the area of
resistance and propulsion but also in other
area such as manoeuvring. Such an advanced
technique as CFD may be needed to develop
the benchmark data with more reliability.
2. Manoeuvring in shallow water
From the view point of manoeuvring
safety, ship behaviour in shallow water area is
much more important than in deep water. Although there may not exist sufficient information for Esso Osaka, efforts for the benchmark
in shallow water should be continued by employing such a way as theoretical approach
mentioned above.
I.2. Discussion on the Report of the 23rd
ITTC Specialist Committee on Esso
Osaka: Selection of data sets
By: Marc Vantorre, Ghent University, Belgium, Flanders Hydraulics Research, Antwerp, Belgium
In the first place I would like to congratulate the Specialist Committee with the final
results. The task, which was based on a recommendation formulated by the 22nd ITTC
Manoeuvring Committee, was not an easy one,
taking account of the large scatter in existing data
and the fact that most tests were carried out decades ago. If time allows, I have several questions I
would like to discuss, some of them directly
related to the report, other being of a more
general character.
Reason of data scatter
It was clear that it was an impossible task
to explain the very large differences between
the experimental data sets. A list of potential
sources of errors was given in Chapter 3.
Most of these sources are also mentioned in
the Manoeuvring Captive Model Test Procedure; I would like to suggest to the next Manoeuvring Committee to check whether additional elements mentioned in the Report of the
Esso Osaka Specialist Committee should be
incorporated into the Procedure. I assume the
Committee will agree that it would have been
much easier to identify the sources of scatter
if the tests had been documented in a way
suggested by the Procedure; please consider
The Specialist Committee on
Esso Osaka
Committee Chair: Prof. Hiroaki Kobayashi (Tokyo Univ. Mercantile Marine)
Session Chair: Dr. Georges Thiery (Bassin d’Essais des Carènes)
740 The Specialist Committee on Esso Osaka
23rd International
Towing Tank
Conference
this as a strong promotion for a proper captive
model test documentation system.
It would be useful to have some more detailed explanation with Figure 3.1.
Selection of data sets
In Chapter 2 it is described in which way
data sets were eliminated so that only five remaining sets for both sway force and yaw moment were left. It is not clear whether the four
sets of tests mentioned in Section 5.2 and in
Table 5.1 have any relation with these five remaining sets; some additional information
would be appreciated. If they have, some questions about the reputation of PMM yawing tests
could be raised, as the four data sets in Table
5.1 are obtained by circular motion tests.
Sources of scatter are more numerous in the
case of PMM testing, as the number of test parameters to be selected is larger and nonstationary techniques are used for investigating
quasi-steady phenomena. As the selection of
the test parameters is even more important for
the reliability of PMM tests, an adequate
documentation of the test conditions is, especially for this type of tests, absolutely required.
It should also be mentioned that the first,
“mechanical” generations of PMM systems
were in some cases not able to generate a purely
harmonic yaw motion without inducing drift.
Moreover, only small amplitude motions could
be generated with the first PMM systems, so that
a sufficiently large range of yaw rates could only
be obtained by increasing the PMM frequency.
More recent larger amplitude PMM systems can
only generate purely harmonic yawing motions
if the main carriage speed can be varied during
the test, and if the sway carriage is able to perform non-harmonic motions. If this is not the
case, fluctuations of the longitudinal ship speed
and drift will be induced, and the forces and
moments caused by these parasitic motions will
affect the test results.
Most of these kinematics problems can be
overcome by the use of CPMC type facilities,
if properly controlled.
Shallow water data
One of the primary advantages of the selection of the Esso Osaka for benchmark data
was the availability of trial data at reduced
water depth. Although I fully understand that
the Committee confined its task to deep water
data, this aspect being hard enough already, it
can be regretted that the shallow water trial
data have not been incorporated in the
benchmark data. Therefore, I would like to
ask the Committee’s opinion about a possible
extension of its work to the shallow water
case.
An analysis of available shallow water
data can be expected to be still more difficult.
The number of data sets is not only considerably smaller, and the scatter is certainly not
less, as is illustrated in Figures I.2.1 and I.2.2.
Moreover, in many cases shallow water data
are only available in a format based on the
deep water data. Some sources of scatter are
amplified in shallow water: as an example, the
effect of propulsion on lateral force and yawing moment is much more important in shallow water (Figure I.2.3).
Unified data
In order to compare the four sets of hydrodynamic hull force data in Chapter 5, unified
data were calculated, i.e. instead of comparing
the manoeuvring coefficients, nondimensional forces and moments were calculated for a number of combinations of sway
and yaw velocities. I fully agree that such a
tabular way of presenting results is often
much more useful than a set of coefficients,
especially when the range of validity is not
specified. Therefore, I would like to suggest
promoting this methodology in either the Captive Model Test Procedure or the Validation
of Simulation Models Procedure.
23rd International
Towing Tank
Conference
Proceedings of the 23rd ITTC – Volume III 741
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
-25 -20 -15 -10 -5 0 5 10 15 20 25
Drift angle (deg)
Y'
(-
)
VBD, Duisburg, regression model
WLH, Antwerp, tabular model
BSHC, Varna, regression model
Maximum angle β of model tests:
VBD, [-24deg; 24deg]
BSHC, [-20deg; 8deg], for Fn = 0.0655
WLH, [-180deg; 180 deg]
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
-25 -20 -15 -10 -5 0 5 10 15 20 25
Drift angle (deg)
N
' (
-)
VBD, Duisburg, regression model
WLH, Antwerp, tabular model
BSHC, Varna, regression model
Maximum angle β of model tests:
VBD, [-24deg; 24deg]
BSHC, [-20deg; 8deg], for Fn = 0.0655
WLH, [-180deg; 180 deg]
Figure I.2.1. Esso Osaka, h/T = 1.20: Non-dimensional lateral force and yawing moment due to drift.
742 The Specialist Committee on Esso Osaka
23rd International
Towing Tank
Conference
-0.20
-0.15
-0.10
-0.05
0.00
0.05
0.10
0.15
0.20
-15 -12.5 -10 -7.5 -5 -2.5 0 2.5 5 7.5 10 12.5 15
γ angle (deg)
Y'
(-
)
VBD, Duisburg, regression model
BSHC, Varna, regression model
WLH, Antwerp, tabular model, Fn=0.033
WLH, Antwerp, tabular model, Fn=0.049
WLH, Antwerp, tabular model, Fn=0.066
Maximum angle γ:
VBD, Duisburg, 15 deg
BSHC, Varna, 15 deg
WLH, Antwerp, 50 deg
-0.10
-0.08
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
-15 -12.5 -10 -7.5 -5 -2.5 0 2.5 5 7.5 10 12.5 15
γ angle (deg)
N
' (
-)
VBD, Duisburg, regression model
BSHC, Varna, regression model
WLH, Antwerp, tabular model, Fn=0.033
WLH, Antwerp, tabular model, Fn=0.049
WLH, Antwerp, tabular model, Fn=0.066
Maximum angle γ:
VBD, Duisburg, 15 deg
BSHC, Varna, 15 deg
WLH, Antwerp, 50 deg
Figure I.2.2. Esso Osaka, h/T = 1.20: Non-dimensional lateral force and yawing moment due to yaw.
23rd International
Towing Tank
Conference
Proceedings of the 23rd ITTC – Volume III 743
-6
-4
-2
0
2
4
6
-90 -60 -30 0 30 60 90
drift angle (deg)
Y
/
(0
.5
ρL
TV
2 )
(-
)
n = 0
n = 0.6 nmax
n = 1.0 nmax
Figure I.2.3. Esso Osaka, h/T = 1.20: Non-dimensional lateral force due to drift, effect of propeller rate (Flanders Hydraulics, Antwerp).
II. COMMITTEE REPLIES
II.1. Reply of the 23rd ITTC Specialist
Committee on Esso Osaka to M.
Hirano
No reply by the Committee.
II.2. Reply of the 23rd ITTC Specialist
Committee on Esso Osaka to M.
Vantorre
No reply by the Committee.

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