AgileShip Ship Maneuvering Assessment Program … · SMAP uses the Holtrop & Mennen approach to calculate the propulsion characteristics of the ship. ... 6.0 SHIP MANEUVERING ASSESSMENT

AgileShipShip Maneuvering Assessment Program

(SMAP) Version 4.0

Demonstration Program Manual

For product information contact:

Proteus Engineering345 Pier One Road

Stevensville, MD 21666Phone: 410-643-7496Fax: 410-643-7535

Email: [email protected]

Copyright © 1996 Advanced Marine Enterprises, Inc.January 1996

All rights reserved. No part of this publication may be reproduced by any means withoutpermission from AME.

The information in this publication is believed to be accurate in all respects. However, AMEcannot assume the responsibility for any consequences resulting from the use thereof. The

information contained herein is subject to change. Revision to this publication or neweditions of it may be issued to incorporate such change.

SMAP is a trademark of Advanced Marine Enterprises, Inc.

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TABLE OF CONTENTS

1.0 INTRODUCTION .................................................ERROR! BOOKMARK NOT DEFINED.

2.0 RANGE OF APPLICABILITY ............................................................................................2

3.0 HISTORY OF SMAP DEVELOPMENT ............................................................................3

4.0 RANGE OF VALIDATION ..................................................................................................4

5.0 HARDWARE REQUIREMENTS AND INSTALLATION ..............................................5

6.0 SHIP MANEUVERING ASSESSMENT PROGRAM - SMAP........................................6

6.1 EQUATIONS OF MOTION............................................................................................66.2 INPUT DATA FOR SMAP.............................................................................................76.3 RUNNING SMAPDEMO...............................................................................................9

7.0 DEFINITIVE MANEUVERS - DEFM ..............................................................................13

7.1 FAST TIME SIMULATION.........................................................................................137.2 RUNNING DEFM.........................................................................................................137.3 ZIGZAG DEFINITIVE MANEUVER .............................................................................147.4 TURNING CIRCLE DEFINITIVE MANEUVER........................................................187.5 SPIRAL DEFINITIVE MANEUVER............................................................................227.6 CRASH STOP DEFINITIVE MANEUVER..................................................................26

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1.0 INTRODUCTION

Note: Throughout this document, AgileShip is referred to as SMAP (Ship ManeuveringAssessment Program).

The purpose of SMAP is to provide the naval architect with a quick method to make predictionsof the maneuvering characteristics at the early design stage. The program is designed to coverblock coefficients from 0.5 to 0.85 (slender ship forms to full ship forms).

SMAP is composed of three programs. The first program, called SMAP, is used to createa hydrodynamic ship file with linear and non-linear coefficients, to make a power prediction atservice speed, and calculate linear maneuvering criteria including criteria for directional stability.The second program, called DEFM, is used to run definitive maneuvers, which consist of turn,zigzag, stop, and spiral maneuver simulations. All maneuvers can be executed in deep andshallow water. The third program, called IDF32 transfers data from the Interface Definition File(.IDF) generated by marine programs such as FAST SHIP into an SMAP input file.

SMAP uses the Holtrop & Mennen approach to calculate the propulsion characteristics ofthe ship. The hydrodynamic coefficients are calculated by use of a number of different equationsto estimate the coefficients. The equations are based on regression analyses of captive modeltests and sea trials:

• Planar motion test data from Hydronautics for more than 50 model tests were used indeveloping regression for the hydrodynamic coefficients.

• Workshop on Modular Maneuvering Models, The Society of Naval Architects andMarine Engineering, November 13, 1991.

• Assessment and Principal Structure of the Modular Mathematical Model for ShipManeuverability Prediction and Real-Time Maneuvering Simulations, by Dr.Vladimir Ankudinov, Dr. Paul Kaplan, and Bent K. Jakobsen, MARSIM 93.

The program estimates the bare hull coefficients first and then the contributions forappendages are added. The SMAP program produces an output file, OUTPUT1.DAT, and thehydrodynamic ship file, DTRXXX.DAT both of which are ASCII text files.

DEFM reads the DTRXXX.DAT file and commands from the screen, and produces anASCII text file, OUTPUT2.DAT along with an on screen and postscript plot of the desiredmaneuver.

The IDF32 program transfers data from the Interface Definition File (.IDF) generated bymarine programs such as FastShip into a SMAP input file.

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2.0 RANGE OF APPLICABILITY

SMAP was developed for monohull displacement ships with ship length to draft ratios from8.2 to 36.7 and block coefficients in the range of 0.48 to 0.83. The ship speed is limited to Froudenumbers less then 0.5. Barge tows cannot be predicted by this program.

• Bulbous Bow

SMAP allows hull geometry with or without a bulbous bow.

• Skegs

SMAP allows from zero to three skegs in the aft section of the ship.

• Rudders

SMAP allows one or two rudders, which may be located behind the propeller or outsidethe slipstream. The program supports the following rudder types:

(1) Spade rudder

(2) Horn rudder

(3) Becker rudder

(4) Schilling rudder

• Propellers

SMAP allows one or two propellers. The propeller thrust and torque are based on theWageningen B-series. The program supports ducted propellers where the calculationsare based on the B470 with a 19A nozzle. B470 is a four-bladed propeller with a 0.70blade area ratio. The P/D (propeller pitch diameter) ratios cover the range 0.5 to 1.4.The program distinguishes between fixed pitch and controllable pitch propellers.

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3.0 HISTORY OF SMAP DEVELOPMENT

The evaluation of ship maneuvering characteristics is of interest to the designer and navalarchitect. The traditional ship design practice of estimating ship maneuvering performance basedon simplified stability criteria and semi-empirical coefficients derived from past experience may notbe sufficient for optimal design. An accurate and quick assessment of the ship-handlingperformance based on hull geometry, powering and control characteristics is the goal. Captivemodel tests have been performed for decades, and trial data is useful information, but has proven tobe too time-consuming to use at the early design stage.

In 1987 Tracor Hydronautics Inc. was tasked by the U.S.C.G. to develop a general computerprogram based on the database of captive model test results, trial data, and material found in theliterature. The software was developed on a VAX750 computer and delivered to run on U.S.C.G.computer. In 1991 AME bought the rights and ownership to the software. SMAP was then usedfor a number of navy designs adding new features to the program. The regression formulas used forestimation of the hydrodynamic coefficients have been revised and compared with Japaneseformulas as the program was used for more ship types.

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4.0 RANGE OF VALIDATION

SMAP has proven to give good early-stage, predictions for a wide range of ships withLength to draft ratio from 8.2 to 36.7, and block coefficients from 0.48 to 0.83. However, somelimitations have still not been overcome by SMAP.

• The speed effect for frigates and destroyers are not properly accounted for. SMAPassumes the ship turning maneuvers to be independent of the ship speed in thetraditional way. This is not the case for fast ships (ship speeds higher than 20 to 25knots). The SMAP program is designed to cover speeds around 20 knots. At shipspeeds around 30 knots, the tactical turning diameter will be larger than predicted bySMAP.

• The bollard pull for all ships is too large. For normal ship maneuvering this is notimportant. The calculated bollard pull is an integral part of the simplified machinerymodel in use in the SMAP program. This part of the model will be improved bycalculating propeller forces from propeller thrust and torque curves in future versions ofthe program.

• Predictions of tugboat models should be used with care, because there is little model testdata for tugboats, and tugboats have length over beam ratios that are much smaller thanmost ships.

• SMAP is based on existing ship maneuvering data. If ship parameters are selectedoutside this data, the predicted maneuvers should only be used for rough estimating.

• The prediction of maneuvering characteristics should always be compared with existingsea trial data or model tests. The program is best used by first running a known shipdesign with similar characteristics, and then running the prediction of the maneuveringcharacteristics for the new design.

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5.0 HARDWARE REQUIREMENTS AND INSTALLATION

SMAP and SMAPDEMO are designed to run on any PC computer system, 486 or better.The software is written in Microsoft FORTRAN PowerStation version 1, which is a 32-bitapplication that uses a MS-DOS extender. The video display supports VGA, 640 x 480 resolutionand SVGA 1024 x 768 resolution.

The SMAPDEMO installation procedure helps the user install the SMAPDEMO softwareon the hard disk. The procedure creates all the required subdirectories and copies the files. Theuser can specify the hard disk and directory for the installed software.

The following should be implemented prior to installation:

− A backup copy of each distribution disk should be made by using a utility such asDISKCOPY or XCOPY. The originals should be stored in a safe place.

To install the SMAPDEMO software, the following steps should be taken:

− Installation and execution of the SMAPDEMO program should be done from the DOSprompt.

− Insert the SMAPDEMO Installation Disk into the floppy diskette drive and enterA:\INSTALL, substitute A: for the actual diskette drive name, and follow theinstallation instructions displayed on the screen. It will request a confirmation of thedestination disk drive and proceed to install SMAPDEMO.

− SMAPDEMO uses data embedded in the executible file versus data read in from thefiles to ensure its use as a demonstration only program. The calculations are doneidentically to the full-featured version of SMAP based on the embedded data.

− Make certain that the SMAP.cfg file is set to VGA (640x480) or SVGA (1024X768) asappropriate.

− You are now ready to run SMAPDEMO.

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6.0 SHIP MANEUVERING ASSESSMENT PROGRAM - SMAP

The ship is considered a rigid body with only three degrees-of-freedom: surge, sway, andyaw. These motions in the horizontal plane are the most important requirements for shipmaneuvering predictions. The ship motions in the other three degrees-of-freedom (roll, pitch, andheave) do not significantly change the maneuvering performance in the normal speed range.However, the variation of the ship hydrodynamic coefficients, as a function of the static trim andsinkage, are included in the SMAP program.

The model is non-linear which causes the model to differ from a linear model by thefollowing:

• Only the non-linear surge equation contains the non-linear resistance and propulsionterms and viscous loss coefficients due to sway and yaw velocities.

• Quadratic and non-linear cross-coupling sway and yaw terms due to separation losses.

• Interaction between rudder and propeller due to the presence of the ship geometry andmotion parameters.

6.1 EQUATIONS OF MOTION

Ship maneuvering equations are well described in their general form as follows:m * [ u - v * r - x * r ] = X + X + XG

2H P R� (1)

m * [ v + u * r + x * r ] = Y + Y + YG H P R� � (2)

z G H P RI * r + m * x * ( v + u * r ) = N + N + N� � (3)where:

XH, XP, XR surge force components of the ship hull, propeller, and rudder

YH, YP, YR sway force components of the ship hull, propeller, and rudder

NH, NP, NR yaw moment components of the ship hull, propeller, and rudder

Iz ship yaw moment of inertia

m ship mass

xG longitudinal coordinate of the ship center of gravity

u, v, r ship speeds in surge, sway, yaw modes

The above equations refer to a right hand orthogonal system of moving axes, fixed in theship, with its origin located at the center of gravity, C.G., of the ship. The complete set of coupleddifferential equations used in SMAP has been well published and extensively validated for a widerange of ships in deep and shallow water.[1,2]

1Holtrop, J., Mennen, G., “An Approximate Power Prediction Method,” International Shipbuilding Progress, Vol. 29,

No.335, July 19822Ankudinov V. K., Miller E. R. Jr., Jakobsen B. K., Daggett L. L., “ Maneuvering Performance of Tug/Barge Assemblies in

Restricted Waterways,” Proceedings of MARSIM & ICSM 90, Tokyo, Japan, 1990.

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6.2 INPUT DATA FOR SMAP

Input for SMAP must be prepared in the form of a data file: XXXXXX.DAT. TheXXXXXX represents a unique name for an input file for a specific ship design and condition.

A new SMAP input file can be created manually using an existing input file from anothervessel, or by executing the IDF32 program. Manually, an existing SMAP input file can be used as atemplate, and modified according to the new ship data with a text editor. The IDF32 program readsan existing Interface Definition File (IDF) hydrodynamics file and creates a new SMAP input filethat includes data from the IDF file.

The required form of a SMAP input file is shown in Fig. 6.2.1. Lines beginning with anasterisk (*) include comments. Lines beginning with a percent (%) include data section titles.Blank lines mark the end of a data section. All other lines in a SMAP input file consist of acharacter string description followed by a numeric value separated by an equal sign. The numericvalue is entered in free format. Only comments and numeric values should be modified by the userto represent specific ships.

In this report, text between bold horizontal lines indicate program data on the PC monitor.User responses are delineated by single brackets <input>. User responses for using function keysare delineated by double brackets <<Return>> or <<F1>>.

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Fig. 6.2.1 Input File for SMAP

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6.3 RUNNING SMAPDEMO

To run SMAPDEMO:

− change directory to C:\SMAPDEMO

− make certain that the SMAP.CFG file is set correctly (VGA or SVGA)

− type <SMAPDEMO> and press <<ENTER>>.

SMAP presents an introductory screen:

A.M.E. maneuvering evaluation

You can select one of the following three ships:

Containership - 1Tanker - 2

Icebreaker - 3

Type 1, 2, or 3:

Two options are available:

− press <<ENTER>> and the default input file will be used, for (i.e., OSAKA.DAT)

− type the requested input file name, for example <OSAKA.DAT>, and press<<ENTER>>. The input file OSAKA.DAT is shown in Fig. 6.2.1.

SMAP will produce a ship stability evaluation plot on the screen, if you press <<ENTER>>.The plot is also available in the postscript file STAB.PLT which is written to \SMAP_V4\OUTPUTsubdirectory (Fig.6.3.1). It will not appear on the screen, if you type <N >and press <<ENTER>>.In the last step, SMAP creates output file OUTPUT1.DAT and a data file necessary for executionof definitive maneuvers in the \SMAP_V4\OUTPUT directory. Example of OUTPUT1.DAT isshown in Fig. 6.3.2a and Fig.6.3.2b.

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Fig. 6.3.1 Example STAB.PLT

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Fig. 6.3.2a Example OUTPUT1.DAT: LINEAR MANEUVERING CRITERIA

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Fig. 6.3.2b Example OUTPUT1.DAT: LINEAR MANEUVERING CRITERIA

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7.0 DEFINITIVE MANEUVERS - DEFM

7.1 FAST TIME SIMULATION

Fast time non-linear computer predictions provide comprehensive information on howvariations of hull, rudder, and propeller design parameters can affect the ship maneuveringperformance. That information creates a rational basis for preliminary stages of ship design andsafety of navigation studies.

DEFM fast time simulation is implemented as a stand-alone separate program, but it runsthe same non-linear models and the same subroutines as the real-time full bridge shiphandlingsimulators operated by Marine Safety, Inc. Thus, DEFM fast time and the real-time simulationsapply exactly the same hydrodynamic forces, moments, and shallow water effects. The majordifference is the control of the program which for DEFM is done from a keyboard using scriptedcommands. DEFM has the capability to run the following definitive maneuvers:

− zigzag

− turning circle

− crash stop

− spiral

The term “definitive maneuvers” has been adopted to describe a class of maneuversdesigned to reveal objective numerical measures for specific ship handling qualities.[3] Althoughthe maneuvers resemble actual ship operational maneuvers performed by a helmsman, thesemaneuvers are independent of the man-in-the-loop control mechanism. Because of that, themaneuvers objectively define the inherent maneuvering qualities of a vessel as a function of itsdesign.

The following list compiles the types of ship-handling capabilities which ship designerswill try to achieve, and which can be effectively examined by DEFM non-linear fast-timesimulation:

− ability to execute an efficient turn

− ability to maintain steady course with small rudder activity

− ability to initiate and to check a course rapidly

− ability to decelerate or stop rapidly while retaining good control over the ship.

7.2 RUNNING DEFM

SMAP creates the linear and nonlinear coefficients for the non-linear coupled surge, swayand yaw equations for ship maneuvering simulations in the time domain. The coefficients createdby SMAP are used by DEFM to simulate definitive maneuvers of the designed vessel. To runDEFM:

− change directory to C:\SMAPDEMO

3 “Guide for Sea Trials” SNAME Technical and Research Bulletin 3-47, 1990.

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− make certain that the SMAP.CFG file is set correctly (VGA or SVGA)

− run SMAPDEMO for a selected ship. For this example, choose the tanker (2)

− type DEFMDEMO.

DEFM presents an introductory screen:

Enter number code of maneuver1 - zigzag2 - Turn

3 - Crash Stop4 - Spiral

Select one maneuver by typing for example <1> for zigzag, and press <<ENTER>>.Execution of all available maneuvers will be reviewed in the following sections.

7.3 Zigzag DEFINITIVE MANEUVER

The standard procedure for the conduct of the zigzag Definitive Maneuver is as follows:

1. Initially:

− The engine/propeller rpm is adjusted to a predetermined initial ship speed. When a steadyengine/propeller rpm and ship speed are achieved, the throttle settings are not changed for thetime of maneuver.

− The rudder is manipulated as necessary until a “practically” straight course has been achievedand maintained for one minute.

2. After steady propulsive conditions on straight course have been established:

− The rudder is laid to a predetermined angle, say 20 degrees, and held until a predeterminedchange of heading, say 20 degrees, is reached.

− At that point, the rudder is deflected at maximum rate to the opposite (checking) angle of 20degrees and held until the ship passes through its initial course to complete the overshoot phaseof the maneuver.

− The maneuver is continued until a heading of 20 degrees to the other side is reached.Whereupon, the rudder is again deflected rapidly to 20 degrees in the first direction. This cycleis repeated through 3rd and 4th executes.

The standard maneuvers are the 20-20 and 10-10 zigzag, although other combinations arealso used. For example, 5-5 zigzag has been advocated for full-form ships.

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7.3.1 Running Zigzag Simulation

After the zigzag maneuver has been selected, DEFM offers two options: deep water, orshallow water, with deep water as a default:

Do you want shallow water? (y/n) [n]

Press <<ENTER>> for deep water default, or type <y> for shallow water. Lets accept deepwater for this example. If shallow water was selected, the ratio of depth to draft would be requested.Shallow water will tend to have the following effects on the zigzag maneuver:

− overshoots decrease,

− reach and period increase.

Then, DEFM asks what heading change the ship has to reach before the rudder isreversed:

Command heading angle (degrees) =

Type your choice, for example <-10>, if the maneuver is expected to make -10/10 zigzag.Negative value for the ship heading means that the ship will turn first to STARBOARD.

Next question is about the magnitude of rudder deflection that is required:

Main rudder angle (degrees) =

Type your choice. Typically, the same value that was declared for the ship heading changeis used. DEFM will not accept different signs for these two commands because it would mean thatthe ship is expected to react inversely to the rudder. To continue with typical values, type <-10>and press <<ENTER>>.

Then, an initial ship speed must be declared:

Ship speed (knots) =

For example, type <7.7> and press <<ENTER>>.

Typically, the zigzag maneuver is executed with the ship speed and the propeller RPMbeing initially in equilibrium. However, it is not necessary and DEFM asks for initial propellerRPM giving the equilibrium value as a default:

Propeller rpm [40.28] =

Value 40.28 is the equilibrium RPM for the ship speed 7.7 kts as already selected. Typeyour choice and press <<ENTER>>. The default value is strongly recommended for standardmaneuvers.

The last information requested is associated with the test identification in the output filesand plots:

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Enter Simulation Run Identification (50 characters) or abort with Ctrl/Z1234567890 1234567890 1234567890 1234567890 1234567890

Type selected description up to 50 characters, or just press <<ENTER>>. For example, type<ESSO OSAKA - test1> and press <<ENTER>>.

The selected maneuver is executed. The following information appears on the screen:

First overshoot heading angle (degrees) = 6.1Second overshoot heading angle (degrees) = 20.4Third overshoot heading angle (degrees) = 17.3Fourth overshoot heading angle (degrees) = 21.5

Period (seconds) = 1158.3Data are ok, plotting in progressOutput ready on .PLT, Postscript

Do you want to make a color plot (y/n) [y]

If you press <<ENTER>>, the default y is accepted and the plot of the executed zigzagmaneuver will appear on the screen. If you type <n> and press <<ENTER>>, the program isterminated. In both cases, two output files are generated in the OUTPUT directory:

− .PLT contains the plot of executed zigzag as a postscript file

− OUTPUT2.DAT contains data calculated during the maneuver.

Fig. 7.3.1 shows an example of the time history from -20/20 zigzag simulated by DEFMwith ESSO OSAKA super-tanker.

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Fig. 7.3.1 -20/20 zigzag simulated by DEFM with ESSO OSAKA super-tanker

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7.4 TURNING CIRCLE DEFINITIVE MANEUVER

The standard procedure for conducting a Turning Circle Maneuver is as follows:

1. Initially:




− The rudder is laid to a predetermined angle, typically 35 degrees right, and held until a changeof heading of at least 540 degrees has occurred. At that point, the maneuver is terminated.

7.4.1 Running Turning Circle Simulation

After the TURN maneuver has been selected, DEFM offers two options: deep water, orshallow water, with deep water as a default:


Press <<ENTER>> for deep water default, or type < y> for shallow water. Let’s acceptdeep water for this example. If you answer <y>, the program prompts you for the depth of the draftratio, shallow water affects the turning circle maneuver in the following ways:

− Tactical Diameter, Steady Turning Diameter, and Transfer increase,

− Final Drift Angle decreases.

Next, DEFM asks what magnitude of rudder deflection is commanded:


Type your choice. Negative value for the ship heading means that the ship will turn toSTARBOARD. Typically, the hard over rudder of approximately -35 degrees is ordered. Tocontinue with typical values, type <-35 >and press <<ENTER>>.




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Typically, Turning Circle maneuver is executed with the ship speed and the propeller RPMbeing initially in equilibrium. However, it is not necessary and DEFM asks for initial propellerRPM giving the equilibrium value as a default. It is recommended that the default be used forstandard maneuvers.


Value 40.28 is the equilibrium RPM for the ship speed 7.7 kts as already selected. Typeyour choice and press <<ENTER>>.


Enter Simulation Run Identification (50 characters) abort with Ctrl/Z1234567890 1234567890 1234567890 1234567890 1234567890

Type selected description up to 50 characters, or just press ENTER. For example, type<ESSO OSAKA - test 2> and press <<ENTER>>.


Tactical Diameter (m) = 950.5 non-dim = 2.92Static Diameter (m) = 476.2 non-dim = 1.47Advance (m) = 1017.4 non-dim = 3.13Transfer (m) = 451.3 non-dim = 1.39

Speed Loss (%) = 78.7Drift Angle (deg) = 20.9

Data are ok, plotting in progressOutput ready on TURN.PLT, Postscript

Data are ok, plotting in progressOutput ready on TURN_CH.PLT, Postscript


If you press <<ENTER>>, the default <y> is accepted and the plot of the executed turningcircle maneuver will appear on the screen. If you type <n> and press <<ENTER>>, the program isterminated. In both cases, three output files are generated in the OUTPUT directory:

− TURN.PLT Contains the plot of executed Turning Circle trajectory as a postscript file

− TURN_CH.PLT Contains the plot of executed Turning Circle characteristics as apostscript file

− OUTPUT2.DAT data calculated during the maneuver.

Fig. 7.4.1 and 7.4.2 show the turning circle and turning characteristics simulated by DEFMwith ESSO OSAKA super-tanker.

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Fig. 7.4.1 Turning Circle Trajectory simulated for ESSO OSAKA super-tanker

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Figure 7.4.2 Turning Circle Characteristics simulated for ESSO OSAKA super-tanker

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7.5 SPIRAL DEFINITIVE MANEUVER

The standard procedure for conducting the Spiral Definitive Maneuver is as follows:

1. Initially:




− The rudder is laid to 15 degrees right and held until a steady rate of change of heading remainsconstant for one minute (or longer, if required in specific cases such as VLCC’s).

− The rudder deflection is then decreased by 5 degrees and held again until the rate of change ofheading remains constant for one minute.

− The procedure is repeated until the rudder has covered a range from 15 degrees on one side to15 degrees on the other side and back again to 20 degrees on the first side. For 5 degrees oneither side of zero rudder deflection, the intervals are taken in one degree steps.

7.5.1 Running Spiral Simulation

After Spiral maneuver has been selected, DEFM offers the deep water, or shallow wateroptions, with deep water as a default:


Press <<ENTER>> for deep water default, or type< y> for shallow water. Lets accept deepwater for this example. If you answer y, the program will prompt you for a depth to ratio draft.Shallow water affects the spiral maneuver in the following way:

− hysteresis loop is getting smaller (ship’s directional stability improves in shallow water)

− slope of curve decreases which indicates increase in directional stability.

Next, DEFM asks for an initial ship speed:



Typically, the Spiral maneuver is executed with the ship speed and the propeller RPM beinginitially in equilibrium. However, it is not necessary and DEFM asks for initial propeller RPMgiving the equilibrium value as default. It is recommended to use the default value for standardmaneuvers.


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Last requested information is associated with the test identification in the output files andplots:


Type selected description up to 50 characters, or just press <<ENTER>>. For example,type <ESSO OSAKA - test 3> and press <<ENTER>>.


Rudder Angle (degrees) = 25.00Turn Rate (degrees/sec) = -0.189 Non-Dim. Rate (r*L/U) =-0.8907

Final Speed (knots) = 2.33 it = 3347

and is updated for each rudder deflection. When the maneuver has been completed, DEFM displaysthe following information:

Data are ok, plotting in progressOutput is ready on SPR.PLT, Postscript


If you press <<ENTER>>, the default <y >is accepted and the plot of executed Spiral willappear on the screen. If you type <n> and press <<ENTER>>, the program is terminated. In bothcases, two output files are generated in the OUTPUT directory:

− SPR.PLT Contains the plot of executed Spiral as a postscript file

− OUTPUT2.DAT Contains data calculated during the maneuver

Fig. 7.5.1 and 7.5.2 show a Spiral simulated by DEFM with ESSO OSAKA super- tanker asit was demonstrated.

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Fig. 7.5.1 Spiral Test simulated for ESSO OSAKA super-tanker

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Fig. 7.5.2 Spiral Maneuver simulated for ESSO OSAKA super-tanker(non-dimensional Turn Rate)

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7.6 CRASH STOP DEFINITIVE MANEUVER

Standard procedure for the conduct of Crash Stop Definitive Maneuver is as follows:

1. Initially:

− The engine/propeller rpm is adjusted to a predetermined initial ship speed. When a steadyengine/propeller rpm and ship speed are achieved, the initial throttle settings are fixed.



− “FULL ASTERN” engine command is executed. In a standard Crash Stop, the rudder is kept inthe constant course position. SMAP allows the simulation of the rudder being deflected aswell. The throttle is reversed at maximum allowable rate or the automatic control lever ismoved in one motion to FULL ASTERN position.

− The maneuver is terminated, when the ship has slowed down to zero speed.

7.6.1 Running Crash Stop Simulation

After Crash Stop maneuver has been selected, DEFM offers an option to use deep orshallow water, with deep water as a default:


Press <<ENTER>> for deep water default, or type <y> for shallow water. Let’s accept deepwater for this example. If you answer y, the program prompts you for the draft ratio, shallow wateraffects the crash stop maneuver in the following way:

− time to stop ship and transfer are shorter,

− ship heading change is smaller.

Then, DEFM asks what Astern RPM value is commanded to stop the ship:

Enter stop rpm =

Type your choice, for example <-45>. Negative value means Astern RPM.

Next question is about the magnitude of rudder deflection that is required:


Type your choice. Typically, zero value (midships rudder) is declared. To continue withtypical values, type <0> and press <<ENTER>>.

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Typically, the service speed is used. But in our example, type <3.5> and press<<ENTER>>.

Typically, Crash Stop maneuver is executed with the ship speed and the propeller RPMbeing initially in equilibrium. However, it is not necessary and DEFM asks for initial propellerRPM giving the equilibrium value as default. It is recommended that the default be used forstandard maneuvers.





Type selected description up to 50 characters, or just press <<ENTER>>. For example,type <ESSO OSAKA - test 3> and press <<ENTER>>.

The selected maneuver is executed, and the following information appears on the screen:

Time to stop ship (sec) = 707.0Advance in stop (ft) = 681.4 non-dim = 2.10Transfer in stop (ft) = 28.7 non-dim = .09

Final Heading (degrees) = 44.0Data are ok, plotting in progress

Output ready on STOP.PLT, PostscriptDo you want to make a color plot (y/n) [y]

If you press <<ENTER>>, the default <y> is accepted and the plot of executed Crash Stopwill appear on the screen. If you type <n> and press <<ENTER>>, program is terminated. In bothcases, two output files are generated in OUTPUT directory:

− STOP.PLT Contains the plot of executed Crash Stop trajectory as a postscript file

− OUTPUT2.DAT Contains data calculated during the maneuver

Fig. 7.6.1 shows Crash Stop Maneuver simulated by DEFM with ESSO OSAKA super-tanker.

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Fig. 7.6.1 Crash Stop Maneuver simulated for ESSO OSAKA super-tanker

Documents

AgileShip Ship Maneuvering Assessment Program … · SMAP uses the Holtrop & Mennen approach to calculate the propulsion characteristics of the ship. ... 6.0 SHIP MANEUVERING ASSESSMENT