CAPTIVE MANOEUVRING TESTS WITH SHIP MODELS: A REVIEW OF ACTUAL PRACTICE, BASED ON THE

22ND ITTC MANOEUVRING COMMITTEE QUESTIONNAIRE

Mare Vantorre, University o f Ghent (Department o f Marine Technology), Ghent, Belgiumc/o Flanders Hydraulics, Antwerp, Belgium

Introduction

Captive model test techniques are nowadays commonly used for predicting ship manoeuvring characteristics. A distinction is made between different types of captive tests:(a) stationary straight line tests, which can be carried out in a towing tank;(b) harmonic tests, requiring a towing tank equipped with a planar motion mechanism;(c) stationary circular tests, performed by means of a rotating arm or a x-y carriage in a wide basin.

Harmonic tests (b) were introduced about 40 years ago; the other types are a few decades older. Taking account of the large number of test parameters to be selected and the differences between and evolution of the concepts of the existing mechanisms, at present each institution applies its own test methodology, mainly based on its own experience and semi-empirical considerations.

The International Towing Tank Conference (ITTC) identified an increasing need for guidelines and even standard test procedures for the execution of this type of ship model tests, in order to ensure the quality of the experimental results. The 22nd ITTC Manoeuvring Committee considered a thorough insight in present methodologies for selecting the experimental parameters for captive model tests, being the result of years of experience of many institutions, as a requirement. For this reason, a questionnaire was circulated among 110 ITTC Member Organisations.

Thanks to the satisfactory response, the Captive Model Test Procedure, formulated by the 22nd ITTC Manoeuvring Committee and published in the ITTC Quality Manual in 1999 (Ref. 1), could be provided with quantitative data reflecting the present state-of-the-art.

A summary of the responses to the questionnaire was given in the Report of the Manoeuvring Committee at the 22nd ITTC (Ref. 2). The present paper provides a more detailed overview of actual practice concerning captive manoeuvring tests.

The Questionnaire

The questionnaire consisted of three parts.In part 1, Experimental facilities: main specifications and physical limitations, details were

asked about tank dimensions, ranges of mechanism kinematics and the range of model dimensions.In the second part, entitled Experimental program: actual practice, information was asked

about the number of values and the ranges of the parameters determining the captive model test program. Generally, distinction can be made between three kinds of parameters:

Kinematic parameters, determining the velocity and acceleration components of thedriving mechanism and, hence, the ship model;

Ship control parameters, in most cases limited to propeller rate and rudder angle; Operation and analysis parameters, which may affect accuracy and validity of test

results (e.g. measuring time, number of PMM cycles, waiting time between runs).Part 3 requested for information about Data acquisition and processing.

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A positive and useful answer was received from 37 institutions, covering 58 facilities distributed as shown in Table 1. It can be concluded that a majority of the institutions performing captive manoeuvring tests are able to combine stationary straight-line tests (a) with harmonic tests (b). Facilities for circular motion tests (c) are rather scarce, and it should be mentioned that some of the institutions only seldom make use of it. This is especially the case for rotating arm facilities; recently built facilities for circular motion tests are always wide tanks equipped with a x-y-vy carriage.

Table 1. Number of Facilities and Institutions.(a) only (b) only (c) only (a)+(b)

not(c)(a)+(c) not(b)

(b)+(c) not(a)

(a)+(b)+(c)

total

# facilities 14 - 7 31 2 - 4 58# institutions 3 - 1 23 3 - 7 37

Part 1. Experimental Facilities

Tank DimensionsDistributions of the main dimensions (length, width, depth, length to width ratio) of the tanks

used for the three types of captive model tests are displayed in figure 1. The distributions for tests (a) and (b) are very similar, which could be expected as most facilities are able to perform both types.

Mechanism KinematicsFacilities for executing tests of type (a) are typically towing tanks equipped with a model

connection system allowing measurement of horizontal forces and moments and setting of drift angles. Distributions of the maximum drift angle are displayed in figure 2(a); 60% of the facilities have no restrictions regarding the static drift angle.

Figure 3 gives an overview of the maximum sway (yA) and yaw (\yA) amplitudes of PMM systems used for executing harmonic tests (b). A clear distinction can be made between PMM systems with restricted amplitude ranges, mostly driven by one single motor, and mechanisms with three degrees of freedom, which are mostly computer controlled: about one third of the facilities appear to be equipped with a (large amplitude) x-y-vy carriage. Figure 2(b) concerns the maximum static drift angle.

Model DimensionsFigure 4 presents differential and cumulative distributions of the data obtained on ship model

length. As some answers referred to a range of lengths, while others only gave an average value, it was presumed that for the latter the minimum and maximum values were 33% lower and higher than the mean value, respectively. For test types (a/b), the median value for the model length appears to be 4.5 m, while the distribution reaches a peak at a length of 3.0 m; 95% of all tests are carried out with model length L > 2 m. On the average, circular tests (c) are performed with smaller models: the median length is only 3 m, the peak in the distribution is reached at 2.2 m, and the 95% limit is 1.5 m.

Distributions of ratios of model length to tank dimensions are displayed in figure 5. Most tests (a/b) are carried out in a tank with a length of 35 times the model length L, while the largest dimension of tanks for circular tests (c) is typically 20 L. The median value for the model length to tank width ratio L/W is 0.47 for stationary straight-line tests (a); it is somewhat smaller (0.42) for harmonic tests(b), as PMMs are usually mounted in tanks that are wider than the average towing tank. Tests (c) are executed in circular or wide tanks, leading to a much smaller median L/W (0.09).

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Part 2(a). Experimental Program: Stationary Straight Line Tests

Test TypesAmong tests of type (a), stationary straight-line tests, distinction can be made between:(al) straight towing;(a2) straight towing with rudder deflection;(a3) oblique towing;(a4 ) oblique towing with rudder deflection.

Kinematic and Ship Control ParametersStationary straight-line test conditions are characterised by following parameters: kinematic parameters: ship model (or carriage) speed, drift angle (only for a3, a4); ship control parameters: propeller rate, rudder angle (only for a2, a4);The questionnaire asked for information about the usual number of values and the way of

selecting the values. The response is summarised in figures 6-11, leading to following conclusions: The number of forward speeds depends on the test type (figure 6), although the highest

frequency of occurrence is obtained for only one speed. On the average, more speeds are selected for resistance-propulsion tests (al), as the self-propulsion point has to be determined by this kind of tests. For a2/a3/a4, the median value appears to be 1 or 2.

The majority of the tests is carried out at only one propeller rate (see figure 7), being the (model or ship) self-propulsion point. Straight towing tests without rudder action (al) and rudder force tests (a2) are often carried out at other propeller loading as well.

The number of drift angles applied in tests a3-a4 is on the average smaller for oblique towing tests with rudder action (see figure 8). The highest frequency is observed at 12 angles for type (a3), and 5 angles for type (a4). A similar distribution is obtained for the number of rudder angles at which tests a2/a4 are carried out (see figure 9). The way drift and rudder angles are selected is displayed in figures 10 and 11, respectively.

Operational and Analysis Parameters.Following operation and analysis parameters are considered for tests of type (a): waiting time

between runs, length of acceleration phase, settling phase, steady phase and deceleration phase.An overview of the response is given in Figure 12. Mostly, no distinction is made between the

different types of tests. On the other hand, the length of the steady phase may influence the accuracy of the analysis results; according to Ref. 9, a measuring length of three times the ship model length should be considered as a minimum. Obviously, this condition is fulfilled by a majority of the test runs.

Part 2(b). Experimental Program: Harmonic Tests

General ConsiderationsFollowing tests of type (b), harmonic tests to be performed in a towing tank equipped with a

planar motion mechanism, are considered:(b 1 ) pure sway tests ;(b2) pure yaw tests;(b3) yaw tests with rudder deflection;(b4) yaw tests with drift.Compared to straight-line tests (a), the number of parameters is considerably larger.

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Kinematic and Ship Control Parameters: OverviewThe models kinematics during a test of type (b) is determined by following parameters: the ship models forward velocity component u; for tests (bl): the lateral motion amplitude yoA and oscillation frequency to, determining

the sway velocity amplitude va and sway acceleration amplitude VA :

v A =yoAc ; * A = y 0A2 ( la)or, expressed in a non-dimensional way:

_ VA yOA L , , . , _ VAL y 0A co2 L2 _ , ,2A = -------= ;------------ = yOAw l VA = 9 - yO A w l ( l b )

u L u u 2 L u 2 for tests (b2,b3,b4): the yaw amplitude \\ia and oscillation frequency to, determining the

yaw velocity amplitude rA and yaw acceleration amplitude f A :

rA = M7a - ; fA = ^ Ato2 (2a)u uor, non-dimensionally:

2

*A s = a 1 y '0 A i2 ; *A = T r = V A ',2 * y'oA'l3 (2b)U u 2

The approximations are valid for small yaw amplitudes, and illustrate the indirectinfluence of the lateral amplitude;

for tests (b4): the drift angle .Ship control parameters applied during harmonic tests are usually the propeller rate n and, for

tests (b3), the rudder angle .

Forward SpeedThe number of forward speeds u applied during a harmonic test program is displayed in Figure

13. For a large range of applications, only one forward speed value is selected.

Sway and Yaw Velocity AmplitudeThe number of sway and yaw velocity amplitudes applied during test programs of types (bl)

and (b2), respectively, is displayed in figure 14. This number varies between 1 and 20, 4 being a median value. There is only a slight difference between the distributions for sway and yaw tests, which is remarkable, as generally tests of type (bl) are only carried out for determining the sway acceleration derivatives, while tests (b2 ) also provide data on both yaw rate and yaw acceleration dependent forces and moments. As shown in figure 15, median ranges for non-dimensional sway and yaw velocity amplitudes are [0.1 ; 0.35] and [0.16 ; 0.58], respectively.

As stated above, a sway/yaw velocity amplitude is the result of a combination of sway/yaw amplitude and oscillation frequency.

Sway and Yaw AmplitudeThe number of amplitudes applied in a harmonic sway/yaw test program varies between 1 and

10, 3 being a median value (see figure 16).The lateral amplitude yoA may be restricted due to technical limitations of the driving

mechanism, but even if the lateral motion extends over the full tank width, interference of the model with the tank walls should be avoided. Figure 17 shows that the lateral amplitude typically takes less

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than 10% of the tank width, and that in more than 90% of the cases the swept path does not exceed half the tank width, as recommended in Ref. 3. Concerning harmonic yawing tests, only a limited number of completed questionnaires contained a range of yaw amplitudes, varying between 5 and 35 deg; also for this kind of tests, restrictions to lateral motion appear to be of greater importance.

PMM Oscillation FrequencyThe median number of frequencies selected for PMM tests is 2, as illustrated in figure 18; many

test programs are based on one single value for the test frequency only.For the selection of the values of these frequencies, several authors formulated guidelines based

on non-dimensional expressions for to :

tests lead to compromise values for toi' which are in the range mentioned above for yaw tests (2-4), but which are very low (0.25-2) for sway tests. If sway velocity derivatives are determined by oblique towing, the accuracy of the inertia terms can be improved by increasing the test frequency (Refs. 1 and 9)

Restrictions for 0)2' can be interpreted as measures for avoiding tank resonance. If the PMM frequency equals one of the natural frequencies of the water in the tank, a standing wave system may interfere with the tests. This occurs if the wave length of the wave system induced by the oscillation equals 2W/n (n = 1,2, ...), W being the tank width. In case of infinite depth, the lowest natural frequency (n=l) occurs at to2' = 7iL/W.

Restrictions for 0)3' are imposed for avoiding unrealistic combinations of pulsation and translation; 0)3' should be considerably less than 0.25 during PMM tests (Refs 3, 5 and 10).

In order to compare common practice with these guidelines, the questionnaire requested to specify the method applied for selecting frequencies; unfortunately, only a minority of the answers appeared to be based on non-dimensional values (1 based on toi', 2 on (02', 1 on (03'). In order to convert the responses to non-dimensional values, a Froude number range between 0.05 and 0.3 was assumed unless specified otherwise. The results are summarised in figure 19.

Interaction of yawing with drift (b4) is typically verified at four drift angles, selected in the range between -30 and +30 deg; [0 deg ; 16 deg] appears to be a median range (see figure 20).

Ship Control ParametersHarmonic tests are usually carried out at only one propeller rate (see figure 21), the self-

(3)

Obviously, limitations of toi' are overruled by those of 102' or 103' for larger Froude numbers. Restrictions of toi' can be interpreted as follows. Restriction of the number of oscillation cycles c due to the available tank length Ltank:

(4)

Several authors (Refs 4-7) suggest maximum values for toi' to avoid non-stationary lift and memory effects; typical values are 1-2 for sway and 2-3 for yaw tests. Comparablevalues result from considerations on lateral wake patterns (Ref. 8).

Considerations on the accuracy of the hydrodynamic derivatives determined by PMM

Drift Angles

propulsion point of the ship or the model. Interaction of yawing with rudder action (b3) is typically

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verified at three rudder deviations. No tendency can be observed concerning the selection of the range of rudder angles (see figure 22 ).

Operational and Analysis Parameters.Following parameters do not influence the ships kinematics, but may affect the test results: length of acceleration phase; length (number of cycles) of transient phase; length (number of cycles) of steady phase; length of deceleration phase; waiting time between two runs; number of harmonics considered during analysis.The length of acceleration and deceleration phase is not selected significantly different

compared to stationary straight-line tests. Figure 23 displays the number of cycles skipped in order to obtain a steady state (usually 1 cycle), and the number of cycles considered for analysis (usually 2-3 cycles). Waiting times between tests of types (a) and (b) are comparable (usually 10 to 20 min).

Part 2(c). Experimental Program: Stationary Circular Tests

Test TypesAmong tests of type (c), stationary circular tests, distinction can be made between:(cl) pure yawing;(c2) pure yawing with drift;(c3) pure yawing with rudder action.

Kinematic and Ship Control ParametersSuch tests are determined by following parameters: kinematic parameters: ship model forward speed, yawing rate, drift angle (c2 only); ship control parameters: propeller rate, rudder angle (c3 only).Distributions of the number of values selected for these parameters are shown in figure 24. Due

to the limited number of responses for this test type, no figures concerning the range of these parameters were produced. Following conclusions could be drawn.

Most tests are carried out at only one combination of forward speed and propeller rate. The number of yaw rates varies from 2 to 16, with 4 as a median value. The non-

dimensional values r=rL/u vary from 0.07 to 1, the median range being [0.2 ; 0.75]. Interaction between yaw and drift is evaluated at a number of drift angles varying from

3 to 24, 7 being the median value. The maximum drift angle varies between 10 and 20 deg; an asymmetric range is applied by about 50% of the respondents.

Important spreading is observed concerning the number and range of rudder angles.

Operational and Analysis Parameters:Following parameters are of interest for tests of type (c): waiting time between runs, usually chosen between 10 and 20 minutes (figure 24); length of acceleration, settling, steady and deceleration phases. The number of responses

was very limited; it can be concluded that only a limited fraction of a revolution, typically less than 180 deg, can be used for analysis, as 120 to 180 deg are required for accelerating and about 60 deg for settling.

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Part 3. Data Acquisition and Processing

The respondents were asked which data are always, sometimes or never measured during captive manoeuvring tests. Distinction is made between data concerning the dynamics and kinematics of the ship model, control parameters of the ship model, and control parameters of the mechanism.

The replies are reflected in figure 25, and can be summarised as follows: Hull forces in the horizontal plane are, obviously, always measured. A majority of the respondents always measures following data:

> position and/or speed of driving mechanism;> ship model control settings (rudder angle, propeller rate);> propeller thrust and torque.

A majority of the respondents always or sometimes measures following data:> rolling moment;> rudder forces and moments;> vertical ship motions.

Calibrations are typically carried out before and after a new test program.Sampling rates vary between 4 and 250 Hz, 20 Hz being a median value.

Concluding Remarks

The analysis of the replies to the 22nd ITTC Manoeuvring Committee Questionnaire provides a thorough insight into the present state-of-the-art concerning the methodology for execution of captive manoeuvring tests. Thanks to the satisfactory response and the detailed answers, to be considered as a summary of the experience that has been developed in a large number of institutes for several decades, a solid base was provided for this analysis.

On the other hand, these data and their analysis should be considered with some caution, especially if it is applied as a tool for developing a standard captive model test procedure. Indeed, such a procedure should always take account of the specific conditions determined by:

the characteristics of the experimental facility (e.g. tank and model dimensions, type of PMM facility, range of mechanism kinematics), which may imply restrictions to the selection of test parameters, and result into facility dependent 'optimal' test programs and procedures;

the application domain of the test results, which may require different ranges of test parameters to be investigated (e.g. determining linear manoeuvring derivatives for evaluating the course stability, mathematical model for prediction of standard manoeuvres, input for simulator models including harbour manoeuvring).

The latter explains the large variation in the number and range of selected values of some of the parameters, e.g. drift angles, rudder deflections, forward speeds.

Furthermore, it should be emphasised that test procedures need to be updated permanently; common practice is not necessarily equal to optimal practice. In this respect, it is important to keep in mind the philosophy on which parameter selection criteria are based. Sometimes it was impossible to retrieve this philosophy in the answers to the questionnaire. As a typical example, the selection of PMM frequencies for harmonic tests (b) could be mentioned:

Although harmonic test results used for quasi-stationary purposes should be checked on their frequency dependency, only one frequency is applied in 50% of the test programs.

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In a majority of the completed questionnaires, oscillation frequencies were expressed in absolute figures. Only a few respondents made reference to selection criteria based on non-dimensional values, as recommended by existing guidelines. Moreover, it was shown that the parameter choice often does not follow these guidelines (see figure 19).

Captive model experiments are considered as a major tool in ship manoeuvring research, and will keep fulfilling an important role in determining mathematical simulation models and providing data for validation of numerical calculation methods. Therefore, test procedures should be based on a set of guidelines in order to ensure the quality and reliability of the test results. If handled with caution, the results of the Questionnaire may provide quantitative data for such guidelines.

Acknowledgements

The questionnaire on captive manoeuvring experiments was carried out in the frame of the tasks of the 22nd ITTC Manoeuvring Committee. The author would like to thank all members for their support: Dr. S. Cordier (chairman), Dr. R. Barr (secretary), Dr. G. Capurro, Dr. M. Hirano, Dr. J. Buus Petersen, Prof. K.-P. Rhee, Prof. Zou Z.-J.

On behalf of the Committee, the author would like to express his appreciation to all ITTC Member Organisations that have completed the questionnaire.

References

1. "Manoeuvring - Captive Model Test Procedure" (1999). 22nd International Towing Tank Conference, ITTC Quality Manual, 4.9-03-04-03, 25 pp. Seoul, Korea & Shanghai, China.

2. "Report of the Manoeuvring Committee" (1999). 22nd International Towing Tank Conference, Proceedings, Volume I, pp. 71-118. Seoul, Korea & Shanghai, China.

3. Leeuwen, G. van (1964), "The lateral damping and added mass of an oscillating shipmodel", Shipbuilding Laboratory, Technological University Delft, Publication No. 23.

4. Nomoto, K. (1975), "Ship response in directional control taking account of frequency dependent hydrodynamic derivatives", Proceedings o f the 14th ITTC, Ottawa, Canada, Vol. 2, p.408-413.

5. Wagner Smitt, L. and Chislett, M.S. (1974), "Large amplitude PMM tests and maneuvering predictions for a Mariner class vessel", 10th Symposium on Naval Hydrodynamics, Boston, USA, pp. 131-157.

6 . Milanov, E. (1984) "On the use of quasisteady PMM-test results", International Symposium on Ship Techniques, Rostock, Germany

7. Leeuwen, G. van, 1969, "Some problems concerning the design of a horizontal oscillator" (in Dutch), Shipbuilding Laboratory, Technological University Delft, Report No. 225.

8 . Vantorre, M. and Eloot, K. (1997), "Requirements for standard harmonic captive manoeuvring tests", MCMC'97, Brijuni, Croatia, pp. 93-98.

9. Vantorre, M. (1992), "Accuracy and optimization of captive ship model tests", 5thInternational Symposium on Practical Design o f Ships and Mobile Units, Newcastle uponTyne, UK, Vol. 1, pp. 1.190-1.203.

10. Goodman, A., Gertler, M. and Kohl, R. (1976), "Experimental technique and methods ofanalysis used at Hydronautics for surface-ship maneuvering predictions", 11th Symposium on Naval Hydrodynamics, London, UK, pp. 55-113.

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diff.

dist

ribu

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(-)

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(-) 0.02

0.01

0.00

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J U r 1 W -1 ^ 1

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0.4 .2

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100 200 300tank length (m)

400

0.50

0.30

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0.10

0.000 10 20 30

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0.4 .2

0.2 1 O0

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0.000 20 40 60 80

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T 1t - - 3 -

J0

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8tank length / tank width (-)

Figure 1. Main facility dimensions: differential and cumulative distributions.

090 (deg) 1800

0.1

73

0

(b)

i. io0 90 (deg) 180

Figure 2. Facilities for test types (a) and (b): distributions of maximum static drift angle

5 yA(m)l0 15 0.5 2yA/W (-)

0.05

73

J. J90^A (deg) 180

Figure 3. Facilities for test type (b): distributions o f maximum amplitudes.

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0.5

0.8

0.60.3

0.2 0.4

0.2

0 105 15

c0'SX1 T3

ship model length (m)

Figure 4. Distributions of the length of ship models used for several types of captive model tests.

c_oSX'Bto-3

i

0.8

0.6 0.6 S

0.4 0.4 :

0.2 0.2 3

00 0.1 0.2

0.6 a

0.4 .2

0 0.2 0.4 0.6 0.8ship model length / tank width

1ship model length / tank length

Figure 5. Distributions of the ratios of ship model length to tank length and to tank width.

0 . 4

Q o

0 . 4

1 G1 o o 0.5

0.8 J l 0 .4J3

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0 O

30.8 3 0.8 0.8 0.80.6 0.6 a

0.2 3

2 3 4 5 6 7 8 9 10 Number of propeller rates

2 3 4 5 6 7 8 9 10 Number of propeller rates

Figure 7. Stationary straight line tests: distribution of the number of propeller rates

0.25

0.8 0.2 0.8 x>0.6

0.4

ju 0.05ta

^ r-* oNumber of drift angles

Figure 8. Stationary straight line tests: distribution of the number of drift angles.Number of drift angles

0.8 J 0.25

js 0.2

3 0.15

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oOn ON i/> l/> NO OO1 drift angle (deg)

0.5

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io

i n o i n o i n o i n o i n o i n o r ^ i T f ' O t ' - O v O f N r ^ i i n ' O O O

Figure 10. Distributions of limits of drift angle range applied for stationary straight-line tests

0.5

-40 -30 -20 -10 0 10 20 30rudder angle (deg)

40

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T3

iti3

7 -+-+-+(a4) 1 1 I X, - J y

. ! ^- H H

lc.23XIT3Io0

-40 -30 -20 -10 0 10 20 30 40rudder angle (deg)

Figure 11. Distributions of limits of rudder angle range applied for stationary straight-line tests.

0.2

T3

0 100 5

1

acc. dist. / model length (-) settling dist. / model length

co'SX

MT313

T3

i50

0 10 20 30steady dist. / model length

Figure 12. Stationary straight line tests: distributions of operation and analysis parameters

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0.5co

o

0 10 20 30 40 50100 5decel. dist. / model length W aiting tim e (min)

Figure 12 (cont). Stationary straight line tests: distributions of operation and analysis parameterss o 1!... 06

3 0.4 0.2

teS o

Q 0.0

blu1 _ _1 2 3 4 5 6 7 8 9 10

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0.8 x>0.8 0.8 r9

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0.2 2

0 U0 U

0.8 -2 0.80.8 -g

0.2 3 0.2 2

0 U 0 u

Number of forward speeds1 2 3 4 5 6 7 8 9 10

Number of forward speedsFigure 13. Harmonic tests: distribution of the number of forward speeds.

1 3 5 7 9 11 13 15 17 19Number of sway velocities

3 5 7 9 11 13 15 17 19Number of yaw velocities

Figure 14. Harmonic tests: distribution of the number of sway/yaw velocities

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lower limit

upper limit

(bl)

10.50

lower limit

upper limit

(b2)

0 2Figure 15. Harmonic tests: distribution of non-dimensional sway/yaw velocity amplitude range.

o 0.5

0.2 1 2.5

Vi Vi

0 0

10

10 (O1! 20 co2 0. 4 3

Figure 19. Harmonic tests: distributions of non-dimensional oscillation frequencies, with indication ofempirical guidelines.

s i .2.>0.8

3 0.6

I 0. 4 c

I 0.6 I 0.4

z

2 3 4 5 6 7 9 10

0.8 0.6

_ _ b3 " , , ~

y .. / _-40 -30 -20 -10 0 10 20 30 40

rudder angle (deg)Number of rudder angles

Figure 22. Harmonie yaw with rudder action (b3) : distribution of number and range of rudder angles.

no. o f transient cycles no. o f steady cycles waiting tim e (min)

Figure 23. Harmonic tests (b): operational and analysis parameters.

1 2 3 4Number of fwd speeds

0

1 2 3 4 5 6 7 8 No.of propeller rates

Figure 24.

1 3 5 7 9 11 13 15 Number of yaw rates

6 11 16 211No. of rudder angles

C/53

1 6 11 16 21Number of drift angles

c

te

5 10 15 20 25 30Waiting time (min)

Stationary circular tests (c): test parameters.

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Dynamics and kinematics o f ship model

Longitudinal force Lateral force Yawing moment Rolling moment Propeller thrust/torque Rudder forces/moments Other forces/moments Sinkage TrimRoll angle

Control parameters o f ship model

Rudder angle Propeller rpm Other

Control parameters o f mechanism : test type (a)

Carriage position/speed Drift angle Other

Control parameters o f mechanism : test type (b

Main carriage pos/speed Lateral position Heading angle Other H

Control parameters o f mechanism : test type (c)

Arm position/speed Drift angle Other

0 20Number o f answers

40

I Always 1 Sometimes I Never

Figure 25. Data-acquisition: data measured during captive manoeuvring tests

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