Report No CPO FUNCTIONAL SPECIFICATIONS GRAPHICAL USER INTERFACE SHUTTLE. Version 2.0

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1 MARIN 2, Haagsteeg P.O. Box AA Wageningen The Netherlands Phone Fax Internet Report No CPO FUNCTIONAL SPECIFICATIONS GRAPHICAL USER INTERFACE SHUTTLE Version April 2003

2 Report No CPO 1 FUNCTIONAL SPECIFICATIONS GRAPHICAL USER INTERFACE SHUTTLE Reported by : T.H.J. Bunnik, PhD J.T.M. van Doorn MSc D. ten Hove, MSc

3 Report No CPO 2 TABLE OF CONTENTS Page TERMS AND ABBREVIATIONS INTRODUCTION OBJECTIVE OF THIS REPORT GENERAL STRUCTURE OF THE INTERFACE Introduction How to work with SHUTTLE Shuttle for dummies? General structure of the database GENERIC DATABASES Generic buoy database Generic material database Generic ship database Generic barge FPSO database Generic tanker FPSO database Generic tug database Generic vector tug database Generic weather database COMPOSING A NEW PROJECT FPSO, BUOYS Ship data Contour, bollards and fairleads Reference points Wind coefficients Current coefficients SHIPS AND TUGS HAWSER AND TOWING LINES YOKE SYSTEMS MOORING SYSTEMS Spring Turret Spread moored Lines ENVIRONMENT Waves Swell Current layer 1 (and 2) Wind AUTO PILOT TRACKS OBSTRUCTIONS CONFIGURATION Offloading configuration FPSO/SPM Ships...55

4 Report No CPO Tugs Hawsers and towing lines Yokes Vector tugs Obstructions Configuration visualisation Manoeuvring configuration FPSO/SPM Ship Vector tugs Obstructions Visualisation of configuration Failures RUNS Offloading runs Manoeuvring scenario ANALYSER Analyser functionality Time traces Statistics Movie or track plots List of computed signals... 72

5 Report No CPO 4 TERMS AND ABBREVIATIONS GUI Leaf Node Project Tree view Graphical User Interface Element of the tree view that can be activated, pushing on a leaf will result in an action of the program Element of the tree view (comparable to a directory in the explorer) A set of computations that belong together (not necessarily for one buoy or FPSO). Presentation of the (data) structure of the model (comparable to the windows explorer)

6 Report No CPO 5 1 INTRODUCTION Offloading operations can have a significant impact on the design, economics, operation and safety of FPSO systems, because: Weather downtime of the offloading effects the economic performance of the FPSO. The choice of the offloading system has a significant impact on the capital and operational expenditure. Safe day-to-day operation requires clear procedures and trained personnel. Offloading operations have a large safety impact, because they involve by definition the operation of two or more structures in close proximity. It is for this reason MARIN started a Joint Industry Project (JIP) to develop and validate tools that can assist in the following aspects of offloading operations: The evaluation of the design and operation, The assessment of limiting weather criteria, and The risk assessment of operations. The Scope of work of this JIP contains the following items: Development of a reliable and user-friendly tool named SHUTTLE that can simulate the offloading behaviour of hawser moored shuttle tankers and their approach to the FPSO or buoy. The tool will be developed such that it can be used to support design as well as operational issues (and a combination of both). Wind tunnel tests will be carried out to investigate the important interaction effects in the current and wind loads of two vessels in close proximity. Model tests will be used to validate the developed tool. The first step in the development of the tool is the definition of the Graphical User Interface (GUI) of the program SHUTTLE. With the Graphical User Interface the look and the feel of the Program is defined. This is an important document as it will define the accessibility of the Program by the users. Within MARIN the following persons have contributed to the definition of this GUI: Gerrit de Boer: Experience with the development of similar tools; Bas Buchner: Head of the offshore department, experienced user; Tim Bunnik: Experienced user and experience with the development of similar tools; Adri van Dijk: Experienced user; Jos van Doorn: Project manager; Dick ten Hove: Experience with the development of similar tools; Jaap Koolmees: Software engineer; Rene Teekema: Software engineer. Outside MARIN Hielke Brugts, as chairman of the Offloading Operability JIP, has given his comments and recommendations. Also included are the comments of the participant meeting in Santiago de Compostella.

7 Report No CPO 6 This report is divided in the following chapters: Chapter 2: Objective of this report; Chapter 3: General structure of the interface; Chapter 4: Generic databases; Chapter 5: Composing a new project; Chapter 6: FPSO, Buoys; Chapter 7: Ships and tugs; Chapter 8: Hawser and towing lines Chapter 9: Yoke systems; Chapter 10: Mooring systems; Chapter 11: Environment; Chapter 12: Auto pilots; Chapter 13: Tracks; Chapter 14: Obstructions; Chapter 15: Configuration; Chapter 16: Scenario; Chapter 17: Analyser.

8 Report No CPO 7 2 OBJECTIVE OF THIS REPORT One of the objectives of the JIP is to develop a user-friendly tool (SHUTTLE) that can simulate tankers approaching FPSO s and the behaviour of FPSO s and tandem moored tankers during offloading. The objective of this report is to present to the participants the Graphical User Interface (GUI). The report gives insight in the general principles used in this GUI and shows the various screens to manipulate data. This report will be the input for a next phase, which will be the development of a prototype of the Graphical User Interface. This computational part of the SHUTTLE program is not yet included in this prototype. At time of writing, the prototype has been largely completed. Screens of the prototype have therefore been included in this document. In some cases, example screens have been prepared in EXCEL. These screens still have to be implemented in the prototype. It should be noted that the prototype screens included in this document should not be considered as final. Small changes to the screens will still be possible. It should be noted that the fundamentals of this GUI will be as described in this report but the details of screens and their arrangement might change. However, no changes to the number of screens and their basic functionalities will be made.

9 Report No CPO 8 3 GENERAL STRUCTURE OF THE INTERFACE 3.1 Introduction The shuttle program requires a lot of data as input. In order to be able to implement and simulate a large variety of structures and combinations of structures flexibility is required. On the other hand it should also be possible to set-up a case in relatively short time. Flexibility and user friendliness are difficult to combine. In this set-up we try to achieve this by making the model transparent, one can always see where he is working. The model contains a number of complete data sets, and together with the scaling option the building of new cases becomes relatively easy. When running the program the computer screen is always divided in two parts. The left part shows the tree structure of the model. The functionality of the left part is comparable to the functionality of the Windows explorer. The view presented is the socalled tree-view, which is sub divided in nodes (sub-directories) and leaves (files, in the tree view the files can be activated ) The right part of the screen is the active data screen (activated in the left part). This right part can be used for input data, building up of configurations, definition of scenario s and running the Program. To get insight and some feeling of how the principle of the Program works two prototype screens are shown on the next two pages (note: the final lay-out of the screens might change during the preparation of the final prototype). The first one is a data sheet that will be used to define the FPSO. On the left side, in the explorer, the node (subdirectory) green FPSO is opened in a project tree with the name Offshore field Green FPSO. The explorer side (left) makes it possible to copy information from one project to the other. The right side makes it possible to access the data and change them if required. The different tabs at the top of the screen give access to different aspects of the ship data. The second example shows the definition of the simulations. Environment and offloading configuration are combined; furthermore details are defined regarding start-up time, simulation time and run-id. In this screen the actual simulations are started. Note that one single simulation can be started (run-option) and that a series of runs can be made in batch. The example screens shown and discussed in this document are based on a prototype of the GUI.

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13 Report No CPO How to work with SHUTTLE The purpose of SHUTTLE is the evaluation of FPSO offloading operations. This is a complex operation with many parameters involved influencing the behaviour of the vessels. Parameters like environment, mooring characteristics, hawser characteristics, ship sizes, assistance etc. To get a reliable result it is required to bring in realistic characteristics for each variable. All data required by the model are stored in a database. This is the so-called project database that contains all data required for one specific project. There are some generic databases that can be used as starting point for building up the database. When similar data are used in different projects these data can be copied from one project to the other. Some leaves are protected from copying because they contain links to other leaves in the project. Preparation For the preparation of a project database the following data can be distinguished: Ship, FPSO and buoy data: In principle available in a generic database that is a part of the SHUTTLE model, correct ship dimensions can be obtained through scaling; Towing lines and Hawsers: In principle available in a generic material database that is a part of the SHUTTLE mode; Yoke system: Definition of the force characteristic of a yoke, to be defined by the user. Mooring systems: In principle not available because these are strongly dependent on the local situation. The mooring system can be built up by elements from a generic database. A simple solution to define the mooring system is to give in the spring characteristics in six directions, this is sufficient to run the program; another option is to copy an existing mooring system to the new project. SHUTTLE will contain at least one example of a spread mooring system and one example of a turret mooring system. Configuration: Combining the mooring system, FPSO or buoy, with a shuttle tanker either in an offloading configuration or in an approach manoeuvre. The configuration should be specified by the user within the project. Environment: Specifying combinations of waves, swell, wind and current. Can be copied from other projects or specified by the user. Auto pilots: Definition of auto pilot coefficients, to be defined by the user. Tracks: Approach tracks for ship manoeuvring, should be specified by the user within the project. Simulation For running a simulation the user has to access: Offloading runs: to specify and run a simulation one has to access the leaf Offloading Runs. Some specific settings can be given in, like start up time and simulation time. The user can choose between directly starting a simulation or prepare a number of simulations and run them in batch. Manoeuvring runs: to specify and run a manoeuvring simulation. Failures: to specify failures of mooring lines, hawsers and tugs during the simulation Analyses For analysing a simulation the user can access: Results: this section contains the results of all simulations executed.

14 Report No CPO Shuttle for dummies? One of the questions frequently asked is: How complicated will it be to run SHUTTLE? As already mentioned in the introduction offloading simulation is a complicated subject. However we think that the proposed user-interface in combination with the generic database, the scaling option for the vessels and the examples make it relatively easy accessible. Of course when one needs to add an additional ship model specific hydrodynamic knowledge is required. Also the implementation of a mooring system is relatively complicated. Building up the mooring system using chain and wire is probably the most complicated part of SHUTTLE. However for a specific mooring this has to be done only once, and users can also decide to use the spring characteristics of the mooring system. These are easy to implement. After basic mooring data are inserted, the program is easy to run. 3.4 General structure of the database SHUTTLE is build up of generic, MARIN supplied databases and user-defined projects. Projects and databases are arranged in a Windows-Explorer like format as shown below This structure is referred to as the tree structure of SHUTTLE. Elements (subdirectories in Windows Explorer) of the tree structure are referred to as nodes. Contents of the nodes (files in Windows Explorer) are referred to as leaves. This definition is clarified below:

15 Report No CPO 14 'Offshore field Green FPSO' is the name of a project. This is a node within the tree structure of SHUTTLE. 'Mooring systems' is a node within the project node 'Offshore field Green FPSO'.

16 Report No CPO 15 'Spread1' is a leaf within the mooring systems node. This leaf contains the actual information of the mooring systems and can be edited in the GUI. Eight generic databases are distinguished: 1) Generic Buoy database 2) Generic Material database 3) Generic Tug database 4) Generic Vector Tug database 5) Generic Ships database 6) Generic Barge FPSO database 7) Generic Tanker FPSO database 8) Generic Weather database The format of these databases is discussed in Chapter 4. This particular example shows two fictive user-defined projects: 1) Offshore field Green FPSO 2) Offshore field Red SPM The contents and format of a typical project are discussed in Chapter 5. A specific project can be built by combining a ship, FPSO or buoy and a tug from the generic database (or by defining new ships, FPSOs, tugs and buoys within a project). The

17 Report No CPO 16 generic material database can be used to select material for the mooring system and for the hawsers and towing lines. The contents of the generic databases cannot be changed. The databases can be copied to a project, where it is possible to change the contents of the now local database. Objects (leafs) within a project or from the generic database (read: ships, tugs, buoys, mooring systems etc. or entire projects) can be copied like directories can be copied within Windows Explorer. In this way, entire projects can be built easily out of small building blocks.

18 Report No CPO 17 4 GENERIC DATABASES All generic databases described in this chapter cannot be opened within the GUI. This is done to prevent 'pollution' of the databases. The contents of the databases can be changed with an ASCII editor outside the GUI if necessary. 4.1 Generic buoy database The generic buoy database contains several pre-defined buoys with different diameter to draft ratios. The exact amount of buoys in the database and their particulars still has to be determined. This will be specified in detail in the technical specifications. The database information is subdivided into general buoy data and more buoy data. The contents of these databases are described further in Chapter 6. The contents of the database cannot be changed. Local copies of the database can be made to a project where it is possible to change the contents of the database. 4.2 Generic material database The generic material database contains the particulars of several types of mooring lines/hawsers. The exact contents of the database still have to be determined and can thus be different. A definite list will be included in the technical specifications. The database will contain information on nylon, chain and steel wire.

19 Report No CPO 18 The contents of the database cannot be changed. User-defined material can be added with an editor outside the GUI. 4.3 Generic ship database The generic ship database contains several typical offloading tankers. The set-up of this database is partly equal to the set-up for the FPSO databases. Importance difference is that this ship database also contains information for ship manoeuvring.

20 Report No CPO 19 The exact contents of the database still have to be determined and will be included in the technical specifications. The example above shows one typical ship. The data for each vessel is subdivided into a general data section and a section with more ship data. The latter section contains information that is not changed very often. The data that is contained in the ship database is described further in Chapter 6. The contents of the database cannot be changed. Local copies of the database can be made to a project where it is possible to change the contents of the database. 4.4 Generic barge FPSO database The generic barge FPSO database contains several barge-shaped FPSOs. The set-up of this database is largely equal to the 'Generic Ships Database' and equal to the 'Generic Tanker FPSO database'. The exact contents of the database still have to be determined and will be included in the technical specifications. The example below shows one typical barge FPSO. The data for each vessel is subdivided into a general data section and a section with more ship data. The latter section contains information that is not changed very often. The data that is contained in this ship database is described further in Chapter 6.

21 Report No CPO 20 The contents of the database cannot be changed. Local copies of the database can be made to a project where it is possible to change the contents of the database. 4.5 Generic tanker FPSO database The generic tanker FPSO database contains several tanker-shaped FPSOs. The exact contents of the database still have to be determined and will be included in the technical specifications. The example below shows one typical tanker FPSO. The data for each vessel is subdivided into a general data section and a section with more ship data. The latter section contains information that is not changed very often. The data that is contained in this ship database is described further in Chapter 6.

22 Report No CPO 21 The contents of the database cannot be changed. Local copies of the database can be made to a project where it is possible to change the contents of the database. 4.6 Generic tug database Two types of tugs can be distinguished in SHUTTLE: 1. vector tugs 2. 'ordinary' or hydrodynamic tugs The first type of tug is modelled as a force vector applied to, for example, a shuttle tanker. The second type of tug is modelled including its hydrodynamic properties (wave forces, wind and current forces and resulting tug motions). The generic tug database contains several typical ordinary tugs. The exact contents of the database still have to be determined and will be included in the technical specifications. Below, a typical example of the contents of the database is given. In this example, three tugs are given. The data that is contained in the tug database is described further in Chapter 7.

23 Report No CPO Generic vector tug database The generic vector tug database contains several typical vector tugs. Vector tugs are tugs schematised in a capability diagram. Their performance is depending on type, ship speed, bollard pull and sea-state. Below, a typical example of the contents of the database is given. The exact contents of the database still have to be determined and will be included in the technical specifications. In this example, three typical vector tugs are given. The data that is contained in the tug database is described further in Chapter 7.

24 Report No CPO Generic weather database The generic weather database contains several typical offloading environments for several locations (North Sea, West of Africa). Below, a typical example of the contents of the database is given. The exact contents of the database still have to be determined and will be included in the technical specifications. In this example, two weather conditions are shown.

25 Report No CPO 24 Input from participants is required to build this database. A maximum of two weather database entries is foreseen.

26 Report No CPO 25 5 COMPOSING A NEW PROJECT A new project can be started in two ways: 1) Copying an existing project and changing the name of the project 2) Inserting an empty project template and giving it a name It should be noted that SHUTTLE will contain several examples that can also be used as a starting point for a new project. In both cases, the project tree of the new project contains a number of nodes (subdirectories). The tree-structure of the project is shown below: The following nodes can be distinguished: 1) FPSO, Buoys 2) Ships and tugs 3) Material database - Local project material database. 4) Mooring systems - set of user-prepared mooring systems 5) Towing line and hawsers - set of user-defined hawsers and towing lines build from material in the project material database 6) Yoke - set of user-defined yoke systems (force versus yoke position) 7) Configuration - the way tugs, tankers and FPSO/buoy are positioned and connected (hawsers, mooring system), see chapter 15

27 Report No CPO 26 8) Environment - wind, current, wave and swell properties 9) Auto pilots - auto pilot settings for ship manoeuvring 10) Tracks - set of user-defined tracks for ship manoeuvring 11) Obstructions 12) Offloading runs - a set of user-prepared runs to simulate tandem offloading 13) Manoeuvring runs - a set of user-prepared runs to simulate the approach to the FPSO 14) Results - results of the runs In the next chapters, the input screens for each of the nodes (sub-directories) are discussed. Each input screen will contain a help option which explains the input fields and specifies the input limits.

28 Report No CPO 27 6 FPSO, BUOYS An FPSO (Barge FPSO or tanker FPSO) or buoy node can be created within the project in only two ways: 1) By copying an existing FPSO or buoy node from the generic database or existing projects to the project node 2) By inserting a set of specific SHUTTLE files in the project database of SHUTTLE. The latter option is not further discussed in this document. When the FPSO or buoy node is selected in the project tree structure, two leaves can be distinguished: 1) Ship data 2) More ship data It may be that a separate 'buoy-data screen' is included as well. However, the input required for a buoy is the same as for a ship. The first (ship data) contains data that is likely to be changed often. When the ship data leaf is selected, a tabular screen appears in the Graphical User Interface. The following tabular screens can be distinguished: - Ship data - Contour and bollards - Reference points - Wind coefficients - Current coefficients The content of the Ship data section is discussed in 6.1. The second leave More ship data contains data that is not likely to be changed often, such as hydrodynamic databases. These data are accessed using a normal ASCII editor. Only very experienced users will edit these files. 6.1 Ship data The screen below shows the ship data input screen. Grey fields are fields that are automatically filled by the GUI. White fields have to be specified by the user. The hydrodynamic database belonging to the ship can be scaled by specifying a new LOA (Length Over All). Ship data that are related to the geometry of the ship are scaled to the correct proportions. Note that this means that all data are adapted (including all hydrodynamic and manoeuvring characteristics). By changing the length a totally new ship is created and for running SHUTTLE it is not required to change or fill in other data. The shuttle model will be prepared with a number of ships/buoys in the generic database. The purpose is that with the available generic data and the scaling option it is possible to come close to the required vessel dimensions. For very specific situations it is always possible to import a specific vessel in the generic or project database. It is furthermore possible to specify additional damping values for all the six motions. For buoys, normally only the wave-making damping (potential damping) is included in the

29 Report No CPO 28 hydrodynamic database. For ships and FPSOs, normally the wave-making damping (potential damping) and the Wichers viscous damping model is included. When this is found to be insufficient, the additional damping can be used. A prototype of this input screen has been prepared and is shown below: 6.2 Contour, bollards and fairleads In the contour, bollards and fairleads screen, the position of the bollards and fairleads and the contour of the ship can be specified and visualised. Note that this screen is filled automatically using fixed relations between main dimensions and ship contour and bollards and fairleads. The user can always decide to change these data. The definition of the contour is only used for visual reasons. It has no influence on hydrodynamics, wind loads and current loads.

30 Report No CPO 29 The number of bollards and fairleads is the same. Each bollard belongs to one fairlead. Towing lines and hawsers are running from a bollard through the fairlead, then to another floater, through a fairlead and finally towards the corresponding bollard. This means that the length of the lines on deck has been included. The line force is applied at the fairleads. The numbers of the contour points, bollards and fairleads are shown in the top and side view as well. The data in this screen is scaled when the ship length in the GUI is changed. 6.3 Reference points In the reference points screen, reference points can be specified. In these reference points, the ship motions are computed during the simulation. The reference points can be visualised in a top or side view of the ship, using the contour defined in the previous screen. Note that reference points are not standard included in the ship database. The user has to define these. The motions in the Centre of Gravity of floaters are always computed by SHUTTLE, so this point does not have to be specified. The data in this screen is scaled when the ship length in the GUI is changed.

31 Report No CPO Wind coefficients In the wind-coefficients screen, the surge, sway and yaw wind coefficients of the ship can be specified and visualised. There are three possibilities to specify the wind coefficients: 1. User-defined coefficients 2. Coefficients from wind tunnel tests executed within this Joint Industry Project 3. OCIMF coefficients These data are not sensitive for scaling. When coefficients are used from wind tunnel tests, a sketch is shown of the tested FPSO or tanker showing the deck equipment.

32 Report No CPO 31 When coefficients from the wind tunnel tests are used, the following hull shapes can be chosen by means of a drop-down menu: 1. Barge shaped (ballast or loaded) 2. Tanker shaped (ballast or loaded) Furthermore, the following types of superstructure can be chosen by means of a dropdown menu: - Empty deck - Deck house only - Deck house and partial deck equipment - Deck house and full deck equipment 6.5 Current coefficients In the current-coefficients screen, the surge, sway and yaw current coefficients of the ship can be specified and visualised. There are three possibilities to specify the current coefficients: 1. User-defined coefficients 2. Coefficients from wind tunnel tests executed within this Joint Industry Project 3. OCIMF coefficients These data are not sensitive for scaling. When coefficients are used from wind tunnel tests, a sketch is shown of the tested FPSO or tanker.

33 Report No CPO 32 When coefficients from the wind tunnel tests are used, the following hull shapes can be chosen by means of a drop-down menu: 1. Barge shaped (loaded and ballast) 2. Tanker shaped (loaded and ballast)

34 Report No CPO 33 7 SHIPS AND TUGS Ships and tugs is a separate node in the SHUTTLE program. However the content of the node and the functionality will partially be identical to the node: FPSO, Buoys, see chapter 6. The difference is that for a ship, manoeuvring characteristics can be specified in a special 'manoeuvring data' screen: The following fields can be distinguished: rudder data engine data propeller data Rudder data contains the following fields: - maximum rudder angle [deg] - rudder speed [deg/s] Engine data contains the following field: - maximum power [kw] Propeller data contains the following fields: - maximum RPM (sea speed) - maximum RPM (manoeuvring) - RPM change

35 Report No CPO 34 8 HAWSER AND TOWING LINES Within the hawser and towing line node, multiple hawsers and towing lines can be defined. A hawser/towing line leaf can be created within the project in two ways: 1) By inserting an empty leaf into the hawser and towing lines node 2) By copying an existing hawser and towing line leaf from the generic database or existing projects to the project node When the leaf is activated, a screen appears in the GUI where the hawser/towing line particulars can be edited: The hawser can be defined by the user or by composing it from material selected from the material database. In case of a user-defined hawser, the load-elongation curve, the breaking strength and the unstretched length have to be specified. When a hawser is composed from a material database, the database has to be selected. This can either be a generic (MARIN supplied) database or a user-provided database. The user-defined database has to be prepared outside the GUI. Elements can be added to the hawser. For each element, the following has to be specified: - Length - Material - Specification

36 Report No CPO 35 - Circumference The available material in the database is shown and can be selected by means of a pulldown menu. The same applies to the circumference. When a part of the line is specified, the break load and the stiffness are shown on the screen. The total length of the hawser is computed. Finally, it is possible to make a plot of the load-elongation curve.

37 Report No CPO 36 9 YOKE SYSTEMS Within the yoke node, multiple yokes can be defined. A yoke is modelled as a relation between force and the relative positions of the yoke attachment points on the two vessels that it connects. Only horizontal yoke forces and moments are considered. However, the yoke forces can induce a roll and pitch moment on the Centre of Gravity. A yoke node can be created within the project in only two ways: 1) By copying an existing yoke node from an existing project to the project node 2) By inserting an empty leaf into the yoke node When the leaf is activated, a screen appears in the GUI where the yoke particulars can be edited. The yoke-fixed forces in the two attachment points (point A on the first vessel (vessel A) and point B on the second vessel (vessel B) have to be inserted and depend on the following: - Position of attachment point B (x and y) relative to attachment point A in a coordinate system fixed to vessel A. The origin of this system is in point A. - Relative heading between vessels A and B. Co-ordinate pairs (x,y) have to be defined in a co-ordinate system that is fixed to vessel A and which has its origin in the yoke attachment point. For each co-ordinate pair, the yoke-fixed forces in points A and B have to be defined.

38 Report No CPO 37 The yoke-forces can have a dependence on the relative heading of vessel A and B. Therefore, the not only the co-ordinates have to be specified, but also the relative heading. In the time-domain simulation, the actual position of point B relative to point A and the relative heading of the two vessels are determined. Depending on the actual state, an interpolation is carried out on the inserted data. More details of the modelling can be found in the technical specifications.

39 Report No CPO MOORING SYSTEMS Inside the mooring systems node, several mooring systems can be defined. When a mooring system leaf is selected, a tabular screen appears in the GUI in which the mooring system can be defined. A mooring system leaf can be created within the project in two ways: 1) By inserting an empty leaf into mooring systems node 2) By copying an existing mooring system leaf from the generic database or existing projects to the project node The following tabular screens can be distinguished: - Spring - Turret - Spread moored The tabular screens indicate the various mooring options Spring When the spring option is chosen, a linear stiffness matrix has to be specified for the surge, sway, heave, roll, pitch and yaw motions. This spring matrix is defined with respect to mid ship/centre line/keel. Otherwise, the turret or spread moored system have to be specified in a separate tabular screen Turret When the turret option is activated, the user has to complete the turret screen.

40 Report No CPO 39 The turret mooring system consists of a number of components that have to be specified: - Turret reference position (earth-fixed) - Composition of the mooring system out of a number of pre-defined lines (see section 10.4) - Fairleads of the lines - Details of line allocation To allocate the anchors (to compute the static load of the line), four options are possible: 1) Specify the position of the anchor at the seabed 2) Specify the catenary span (horizontal distance from anchor to fairlead) 3) Specify the pretension at the fairlead 4) Specify the pretension angle at the fairlead The anchor positions are computed at the specified reference water depth and reference draft. In the simulation (when the mooring system is connected to a FPSO/buoy), the water depth and/or draft can be different. However, the horizontal location of the anchor points is fixed. Several visualisation options are available to check the individual lines and the entire turret mooring system. For the individual lines, the following plot options can be selected by means of a pulldown menu: 1) Horizontal displacement versus fairlead tension 2) Horizontal displacement versus fairlead angle

41 Report No CPO 40 3) Horizontal displacement versus anchor tension 4) Horizontal displacement versus anchor angle Furthermore, the static load of the entire mooring system can be shown. For that purpose, the mooring system is connected to a fictive floater. The floater can be rotated and pulled in any direction (not included yet in the prototype screen above). Mooring forces and moments at the keel/mid ship are shown in the static load curve. Finally, a side view of an individual line and a top view of the entire mooring system can be shown Spread moored When the spread-moored option is activated, the user has to complete the spreadmoored screen. The spread-moored system consists of a number of components that have to be specified: - Reference position of centre of spread mooring system (not yet shown in the prototype screen) - Composition of the mooring system out of a number of pre-defined lines (see section 10.4) - Fairleads of the lines - Details of line allocation To allocate the line (to compute the static load of the line), four options are possible:

42 Report No CPO 41 1) Specify the position of the anchor at the seabed 2) Specify the catenary span (horizontal distance from anchor to fairlead) 3) Specify the pretension at the fairlead 4) Specify the pretension angle at the fairlead The anchor positions are computed at the specified reference water depth and reference draft. In the simulation (when the mooring system is connected to a FPSO/buoy), the water depth and/or draft can be different. However, the anchor points are fixed. Several visualisation options are available to check the individual lines and the entire spread mooring system. For the individual lines, the following plot options can be selected by means of a pulldown menu: 1) Horizontal displacement versus fairlead tension 2) Horizontal displacement versus fairlead angle 3) Horizontal displacement versus anchor tension 4) Horizontal displacement versus anchor angle Furthermore, the static load of the entire mooring system can be shown. For that purpose, the mooring system is connected to a fictive floater. The floater can be rotated and pulled in any direction (not included yet in the prototype screen above). However, the horizontal location of the anchor points is fixed. Finally, a side view of an individual line and a top view of the entire mooring system can be shown Lines In the lines screen, the individual lines are defined. The definition of a line can be done in two ways: 1) By defining the relation between the horizontal distance between anchor and fairlead and the pretension angle and pretension at the fairlead 2) By composing a line out of material in a material database

43 Report No CPO 42 When a line is composed out of a material database, it consists of a number of segments. For each segment, the following has to be specified: - Length - Buoy force - Material from the selected material database, selected by means of a pull-down menu (for example steel wire or chain) - Specification, selected from a pull-down menu - Diameter, selected from a pull-down menu The line definition is sketched below:

44 Report No CPO 43 chain segment (3) buoy buoy wire segment (2) chain segment (1) sea bottom The buoy force is added between segments. When a segment has been specified, the break strength, elasticity, submerged weight and the mass in air automatically appear on the screen. When the total line has been specified, the characteristics of the line can be shown, provided that a reference water depth and the height of the fairlead above the seabed are given. The following line characteristics can be shown: - Horizontal distance between fairlead and anchor versus fairlead tension - Horizontal distance between fairlead and anchor versus fairlead angle - Horizontal distance between fairlead and anchor versus anchor angle (not for user-defined line) - Horizontal distance between fairlead and anchor versus anchor tension (not for user-defined line)

45 Report No CPO ENVIRONMENT Within the environment node, the project environmental conditions (waves, swell, current, waves) can be defined. An environment leaf can be created within the project in two ways: 1) By inserting an empty leaf into the environment node 2) By copying an existing environment leaf from an existing project or from the generic environment database to the project node When a leaf within the environment node is selected, a tabular screen appears in the GUI. The following tabular pages can be distinguished: - waves - swell - current layer 1 - current layer 2 - wind 11.1 Waves In the waves tabular screen, the wave conditions can be specified. There are three ways to define a wave: 1) By means of a theoretical wave spectrum 2) By means of a user-defined wave spectrum

46 Report No CPO 45 3) By means of a wave time trace The following theoretical wave spectra are included in SHUTTLE: - JONSWAP - Pierson-Moskowitz - Regular wave - Gaussian These can be selected by means of a pull-down menu. When a wave spectrum is required which is not in this list, it can be defined by means of a user-supplied list of wave frequencies versus spectral densities. A random seed has to be specified to generate the random phase of each wave component. The wave time trace option can be used when a wave measurement is available, for example from a model test or a full-scale measurement. In that case, the significant wave height Hs is computed and shown on the screen. The time trace can be scaled by specifying another significant wave height. The wave direction and the wave height are either fixed or can be varied in time. The characteristics of the wave spectrum, period and shape, cannot be varied in time. The wave direction is shown in a plot with compass directions. When varying in time, the wave direction with the time indication is shown in this plot. Furthermore, a list then has to be specified with time versus significant wave height, wave direction and orientation of change (clockwise or counter clockwise) Swell The swell tabular screen is identical to the waves tabular screen.

47 Report No CPO Current layer 1 (and 2) In the current tabular screen, the current properties are specified.

48 Report No CPO 47 Two current layers can be specified, each with its own effective depth. When the draft of a floater is smaller than the first effective depth, only the first current layer is used to compute the current forces. When the draft of the floater is larger than the first effective depth, the second layer is also used to compute the current forces (proportionally with the part of the vessel draft in each layer). A third layer extends from the bottom of the second layer to the seabed. In this layer, the current speed is zero. The current is spatially (horizontally) constant. The current speeds and direction are either fixed or varying in time. In the latter case, a list has to be specified with time versus current speed, current direction and the orientation of change (clockwise or counter clockwise). The current direction is shown in a plot with compass directions. When varying in time, the current direction is shown which is activated in the table Wind In the wind tabular screen, the wind properties are specified.

49 Report No CPO 48 The wind is assumed to be spatially constant. There are three ways to define the wind: 1) By means of a theoretical wind spectrum 2) By means of a user-defined wind spectrum 3) By means of a constant wind (no gust) The following theoretical wind spectra are included in SHUTTLE: - API - Ochi-Shin - Harris - NPD - Wills - DNV These can be selected by means of a pull-down menu. The wind direction and mean speed are either fixed or can be varying in time. When varying in time, a list has to be specified with the time versus wind speed, wind direction and orientation of change. The wind direction is shown in a compass plot. When the wind direction is varying in time, the wind direction is shown which is activated in the table. A seed is specified to generate a sequence of random phases for each wind frequency component.

50 Report No CPO AUTO PILOT The auto pilot definition is used in the manoeuvring simulation. Auto pilot settings have to be selected for each part of a track definition (see chapter 13). New auto pilot settings can be defined in two ways: 1) By inserting an empty leaf into the auto-pilot node 2) By copying an existing auto-pilot leaf from an existing project to the project node The auto pilot takes as input: Autopilot id Use of the manoeuvring devices rudders [%] power burst [%] main propulsion [%] thrusters [%] tugs [%] Anticipation length Autopilot coefficients 1 coefficient for the forward speed control 5 coefficients for the sideways direction control 5 coefficients for the rotational control Below, a short description of the coefficients is given. The auto pilot name is used to identify the auto pilot and to link it to a track section. One auto pilot can be linked to multiple track sections. The use of the manoeuvring devices is related to the maximum capacity of the related manoeuvring device and is specified as a percentage. For the rudder the related parameter is the maximum rudder angle. The pilot will not use more then the specified percentage of the maximum rudder angle. For the main engine this is the maximum

51 Report No CPO 50 number of revolutions ahead. The pilot will not use more then the given percentage of the maximum revolutions. For the thrusters the related parameter is the maximum thrust force and for the tugs the maximum bollard pull. The power burst is slightly different from the other four. The powe rburst is related to the maximum revolutions of the main engine. The number specifies the percentage of the maximum revolutions of the main engine that can be used for a power burst. No power burst is used if the percentage is lower then the percentage for the normal use of the main engine. Otherwise the specified number of revolutions for the power burst is used (when necessary) and overrules the normal setting for the main engine. The anticipation length is the distance ahead of the ship (relative to the Centre Of Gravity) that is used for control. It can be regarded as the point at which the auto pilot plans to get the ship on the desired track with the desired velocity and course offset. The anticipation length is specified in ship lengths. The auto pilot coefficients are by default set to 1.0. They can be used to make the auto pilot more sensitive to particular deviations. The first coefficient for the forward speed control is only used when a required velocity is specified. The coefficient makes the auto pilot more (or less) sensitive for deviations from the forward speed. The coefficient has no meaning when a required engine setting (rps) is specified. For the other two sets the coefficients are related to the same deviation measures. The first one is for future use and has no meaning. The second one is related to the distance of the origin of the ship perpendicular to the track (the track deviation). The third one is related to the course track error. The fourth coefficient is related to the sideways velocity and the sensitivity for cross current and, finally, the fifth coefficient is related to the rotational velocity (yaw). Changing the coefficients will make the auto pilot more (or less) sensitive to the described deviation measure. The rotational direction control uses all four deviation measures. So, except for the first one, all coefficients are used. The sideways direction control only uses the track deviation and the sideways velocity. So, only the second and fourth coefficients are used. The coefficients for the sideways direction control only have a significant effect when manoeuvring at low (less then 1.0 m/s) forward speed. The coefficients for the rotational control have a significant effect at higher (greater then 1.0 m/s) forward speeds.

52 Report No CPO TRACKS The track definition is used in the manoeuvring simulation. A track is defined by: 1) the distance between the FPSO and approach tanker 2) the speed of the approach tanker at the particular distance 3) the engine setting at the particular distance 4) the control strategy for that part of the track Along the track different control strategies are possible, e.g. strategy for engine use (dead slow/stopped combined with tugs for speed control); number and position of tugs; track control or dynamic positioning. Furthermore in addition to the control strategy, for each part of the track, auto pilot settings have to be specified. This means that the auto pilot settings can be different along the track. The auto pilot settings have to be selected from a pull-down menu, showing all the available auto pilots within the project. The project tracks are defined in the tracks-node. A new track can be defined in two ways: 1) By inserting an empty leaf into the tracks node 2) By copying an existing track leaf from an existing project to the project node Below, an example screen is shown. A GUI prototype of this screen has not yet been prepared at time of writing.

53 Report No CPO OBSTRUCTIONS Within the obstruction node, obstructions (platforms etc.) can be defined. In the configuration screen (see chapter 15) these obstructions can be placed in the neighbour hood of the FPSO or buoy. These obstructions are only used for visualisation purposes. Collision between the obstruction and floaters is not modelled. An obstruction leaf can be created within the project in two ways: 1) By inserting an empty leaf into the obstruction node 2) By copying an existing obstruction leaf from an existing project to the project node The contour points of the obstruction (x and y values) have to be specified. Contour points can be added and removed. The obstruction is visualised (topview) and the numbers of the contour points are shown as well.

54 Report No CPO CONFIGURATION A configuration is defined as a combination of a FPSO/buoy and its mooring system, possibly a tanker and/or tug and the hawsers, towing lines and yokes with which they are connected. The initial position and heading (with respect to North) of each floater is specified as well. Separate configurations exist for offloading simulations and for manoeuvring simulations. Furthermore, a tabular screen is available in which failures can be specified. A new configuration leaf can be created as follows: 1) By inserting an empty leaf into the node 'configuration' It is not possible to copy a configuration leaf from another project since it involves references to other leafs in a project. It is however possible to copy entire projects Offloading configuration The input for the offloading configuration will be divided over two screens. The layout of the first screen is shown below: The layout of the second screen is shown below:

55 Report No CPO 54 The offloading configuration screen is the most extensive screen in the GUI and one of the most important. Several fields can be distinguished in this screen: - FPSO/SPM (with choice of mooring system) - Ships - Tugs - Hawsers and towing lines - Yokes - Vector tugs - Obstructions - Visualisation of configuration It should be noticed that the configuration has to go to equilibrium before the real simulation starts. SHUTTLE has the possibility to define a period of constant average forces on the structures. In this period the configuration can move to an equilibrium position (see also 16.1) FPSO/SPM First, an FPSO or buoy is selected from the available FPSOs and buoys in the project. This is done with a pull-down menu showing all available options. Second, the position and heading have to be specified. Values can be entered in the screens or + and - buttons can be pressed with the mouse to increase and decrease the value. After this is done, the position and orientation of the FPSO or buoy can be visualised on the configuration screen (see section ). Third, a mooring system is selected from the available mooring systems in the project. This is done with a pull-down menu showing all available mooring systems. The position of the mooring system with respect to the floater origin (see technical specifications) has

56 Report No CPO 55 to be specified. For a turret mooring system this is the centre of the chain table. For a spread mooring system, this is the mooring system centre. Finally, green, orange and red sectors can be specified (danger zones). These zones are shown in the top view visualisation. The centre of the zones (FPSO-fixed point) has to be specified as well. The zones rotate and move horizontally together with the FPSO Ships It is possible to select at most one ship. With the 'add' button, a new ship entry is created. With the 'remove' button an entry can be removed. When a ship is added, a ship has to be selected from the available ships in the project by means of a pull-down menu. The position and the orientation of the ship have to be entered on the screen or can be altered by pressing + and - buttons with the mouse. After this is done, the position and orientation of the ship can be shown on the configuration screen (see section ) Tugs It is possible to select at most one tug. With the 'add' button, a new tug entry is created. With the 'remove' button an entry can be removed. When a tug is added, a tug has to be selected from the available tugs in the project by means of a pull-down menu. The position and the orientation of the tug have to be entered on the screen or can be altered by pressing + and - buttons with the mouse. After this is done, the position and orientation of the tug can be shown on the configuration screen (see section ). There are three ways to control the tug: 1) Constant thrust force (earth-fixed) 2) Constant thrust force (tug-fixed) 3) Fixed position The preferred control option can be specified with a pull-down menu. When option 1 or 2 is selected, a secondary screen appears in which the thrust forces/moment (surge, sway and yaw) have to be entered. These stay constant during the entire simulation. When option 3 is selected, the tug stays at its starting position. A hydrodynamic tug can only be used if there are no vector tugs Hawsers and towing lines It is possible to select more than one hawser or towing line. With the 'add' button, a new entry is created. With the 'remove' button an entry can be removed. When a hawser or towing line is added, it first has to be selected from the available hawsers/towing lines in the project by means of a pull-down menu. The hawsers and towing lines are connected from a floater and connected to a floater. These two floaters have to be selected from a pull-down menu, showing all the available floaters in the project. Besides the floater, the bollard on the floater has to be selected as well. This is again accomplished by selecting a bollard from the available bollards in a pull-down menu. When the hawser has been connected, the hawser pretension is computed from the distance between the bollards and shown on the screen. It is possible that the simulation

57 Report No CPO 56 becomes unstable when unrealistically large hawser forces are applied at the start of the simulation. Therefore, when the hawser force is above a certain threshold value it is marked in red, indicating possible difficulties at the start-up of the simulation. It is recommended to position the vessels such that initially, the hawser length equals its unstretched length. It should be noted that when running the model a start-up time can be specified to come to an equilibrium before starting the actual simulation Yokes Yoke systems are inserted similar to hawsers and towing lines. They are used to connect two floaters. It is possible to select more than one yoke. With the 'add' button, a new entry is created. With the 'remove' button an entry can be removed. When a yoke is added, it first has to be selected from the available yokes in the project by means of a pull-down menu. The yokes are connected from a floater and connected to a floater. These two floaters have to be selected from a pull-down menu, showing all the available floaters in the project. Besides the floater, the yoke attachment points on the two floaters have to be specified (floater-fixed point). When the yoke has been connected, the yoke pretension is computed from the distance between the attachment points and shown on the screen. It is recommended to place the vessels such that the initial force in the yoke is as small as possible Vector tugs Besides ordinary tugs (see section ), vector tugs can be applied as well. Vector tugs are modelled as a force vector applied to a bollard or a floater. This implies that, unlike for the ordinary tugs, the dynamics of the tug (equation of motion) are not computed. It is possible to select more than one vector tug. With the 'add' button, a new entry is created. With the 'remove' button an entry can be removed. When a vector tug is added, it first has to be selected from the available vector tugs in the project by means of a pulldown menu. Second, the floater and the bollard have to be selected at which the tug is pushing or pulling. Vector tugs can be applied both to an offloading tanker and to an FPSO. Third, the type of assistance is defined (push, pull or push/pull). Fourth, control strategy is defined (preferred heading of the offloading tanker and/or angle of the hawser). Finally, a control type has to be selected. Two options are possible: 1) Auto pilot 2) Constant force The auto pilot used tugs are modelled with tug capability diagrams. These diagrams cannot be edited in the GUI. When the constant force option is chosen, a constant force has to be specified on the screen. Vector tugs can only be used if there is no hydrodynamic tug Obstructions Obstructions can be placed in the offloading area of the vessels. These obstructions only serve for visual purposes. An impact model will not be implemented.

58 Report No CPO 57 It is possible to select more than one obstruction. With the 'add' button, a new obstruction can be added. With the remove button, an obstruction can be removed. An obstruction has to be selected from the available obstructions within the project. The earth-fixed position and the orientation have to be specified Configuration visualisation Below, the part of the screen is highlighted that visualises the offloading configuration (example only).

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60 Report No CPO 59 N O E The visualisation is a top view intended to provide a visual check of the floater positions, floater headings, the mooring system, obstructions and the hawsers with respect to the global co-ordinate system. The bollards and fairleads are shown as well. The view can updated when changes are made in the GUI to the definitions of the floaters, hawsers, obstructions or mooring system. It is possible to zoom in and out. The red, green and orange sectors are shown as well Manoeuvring configuration The manoeuvring configuration screen is similar to the offloading configuration screen. The differences are that: - Only vector tugs can be defined (no hydrodynamic tug) - No hawsers and towing lines can be defined - A track has to allocated to the tanker The following fields can be distinguished in this screen: - FPSO/SPM - Ship - Vector Tugs - Obstructions - Visualisation of configuration

61 Report No CPO FPSO/SPM First, an FPSO or buoy is selected from the available FPSOs and buoys in the project. This is done with a pull-down menu showing all available options. Second, the position and heading have to be specified. Values can be entered in the screens or + and - buttons can be pressed with the mouse to increase and decrease the value. After this is done, the position and orientation of the FPSO or buoy can be visualised on the configuration screen (see section ). Third, a mooring system is selected from the available mooring systems in the project. This is done with a pull-down menu showing all available mooring systems. The position of the mooring system with respect to the floater origin (see technical specifications) has to be specified. For a turret mooring system this is the centre of the chain table. For a spread mooring system, this is the mooring system centre. Finally, green, orange and red sectors can be specified (danger zones). These zones are shown in the top view visualisation. The centre of the zones (FPSO-fixed point) has to be specified as well. The zones rotate and move horizontally together with the FPSO Ship At most one approach tanker can be selected. The selection is made from the available ships in the project by means of a pull-down menu. Furthermore, an approach track has to be selected. This is again accomplished with a pull-down menu. The definition of the track (see chapter 13) contains no definition of the track (it is just a distance-speed relation relative to the FPSO or buoy). Therefore, the direction of the track has to be specified as well. Also the initial values (position, heading, velocity, rate of turn and rpm) are defined. Finally, a bollard on the FPSO/buoy has to be selected that serves as the

62 Report No CPO 61 set point for the approach tanker. Alternatively, this set point can also be an earth-fixed point Vector tugs In the manoeuvring simulation, only vector tugs can be applied. Vector tugs are modelled as a force vector applied to a bollard of a floater. The vector force is depending on the bollard pull, tug type, ship speed and wave height. This is defined in the so-called capability diagram. The dynamics of the tug (motions) and the towing line are not computed. It is possible to select more than one vector tug. With the 'add' button, a new entry is created. With the 'remove' button an entry can be removed. When a vector tug is added, it first has to be selected from the available vector tugs in the project by means of a pulldown menu. Second, the floater and the bollard have to be selected at which the tug is pushing or pulling. Third, the type of assistance is defined (push, pull or push/pull). Finally, a control scenario has to be selected. Two options are possible: 1) Auto pilot 2) Constant force The auto pilot responds to deviations of the desired track and heading. The control strategy is defined as part of the track. Response of the tug will depend on tug capability diagrams. These diagrams cannot be edited in the GUI. When the constant force option is chosen, a constant force has to be specified on the screen Obstructions Obstructions can be placed in the neighbourhood of the vessels. These obstructions only serve for visual purposes. An impact model will not be implemented. It is possible to select more than one obstruction. With the 'add' button, a new obstruction can be added. With the remove button, an obstruction can be removed. An obstruction has to be selected from the available obstructions within the project. The earth-fixed position and the orientation have to be specified.

63 Report No CPO Visualisation of configuration Below, the part of the screen is highlighted that visualises the manoeuvring configuration.

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65 Report No CPO 64 N O E The visualisation is a top view intended to provide a visual check of the floater positions, floater headings, obstructions and the mooring system with respect to the global coordinate system. The track is shown as well. The view is corrected when changes are made in the GUI to the definitions of the floaters, mooring system, obstructions or track. It is possible to zoom in and out. The red, green and orange sectors are shown as well Failures The following failures can be specified: - Failure of hawsers and towing lines - Failure of mooring lines - Failure of vector tugs - Failure of 'ordinary' tugs (offloading simulations only) - Failure of engine approach tanker (manoeuvring simulations only) - Failure of rudder approach tanker (manoeuvring simulations only) An example input screen has been prepared in EXCEL. A GUI prototype of this screen has not yet been prepared.

66 Report No CPO 65 With each failure it is possible to define the failure response (proceed the approach, stop approaching, proceed offloading, depart).

67 Report No CPO RUNS A run is a combination of a configuration (definition of floaters, mooring system and hawsers see chapter 15), an environment (waves, swell, current and waves, see chapter 11) and the definition of some run-time parameters. It defines the particulars of a single simulation. A new run can be created as follows: 1) By inserting an empty leaf into the node 'offloading runs' or into the node 'manoeuvring runs' It is not possible to copy a run from another project since it involves references to other leafs in a project. It will be possible to copy entire projects. Separate screens exist for the offloading runs and for the manoeuvring runs Offloading runs The screen below shows the particulars of the offloading run screen. First, an offloading configuration has to be selected. This is done by means of a pulldown menu showing all the available offloading configurations in the project. Second, an environment has to be selected. Again, this is done by means of a pull-down menu showing all the available environments in the project. Third, some parameters relating to the length of the simulation have to be specified: - start-up time for constant forces (T1) - simulation time with constant forces (T2) - start-up time for dynamic forces (T3) - simulation time with dynamic forces (T4)

68 Report No CPO 67 The meaning of these parameters is clarified in the figure below: force T1 T2 T3 T4 time This figure shows an example of the environmental force (wind, current, wave and swell forces combined) versus time. A distinction is made between a simulation time with constant forces (no wind gust and only mean wave drift forces) and dynamic forces (so with wind gust, slowly varying wave drift forces). In the first time interval (T1), the environmental forces are built up towards their mean value. In the second time interval (T2), the forces remain constant at their mean level. This second time interval can be used to establish equilibrium before the start of the simulations. So it is not required to position the vessels in an equilibrium position during the preparation of the configuration. It is possible to consider different environmental conditions starting with the same configuration. In the third time interval (T3), the environmental forces build up towards their dynamic value. The final time interval (T4) is the simulation time with dynamic forces. During the start-up time T1, a start-up function is applied to all external forces (hawser forces, yoke forces towing line forces and environmental forces). The start-up force is zero at the start of the simulation (t=0) and increases towards one at t=t1. This makes sure that initially all external forces are zero. Furthermore, the following time steps can be specified (not shown yet in the GUI prototype screen): - Time step for data logging - Time step for generation of first-order wave forces - Time step for generation of second-order wave forces - Time step for generation of wind gust Sensible default values will be available in the GUI. Finally, it will be possible to switch on or off the wind, current and wave shielding predictions separately (not shown yet in the GUI prototype screen). When switched off, the unshielded forces will be used.

69 Report No CPO 68 By pressing the 'run' button, the simulation is started. It is also possible to add the scenario to a batch list of runs. By pressing 'execute batch', all runs in the list are executed. A description or comment field is available for each run Manoeuvring scenario The screen below shows the particulars of the manoeuvring scenario screen. First, a manoeuvring configuration has to be selected. This is done by means of a pulldown menu showing all the available manoeuvring configurations in the project. Second, an environment has to be selected. Again, this is done by means of a pull-down menu showing all the available environments in the project. Third, some parameters relating to the length of the simulation have to be specified: - start-up time for constant forces - time at which approach is started - simulation time after approach is finished In addition to the simulation time it is possible to specify stop criteria, such as a minimum forward speed or a distance to the FPSO (not yet shown in the GUI prototype screen above). The simulation stops if one of these variables is lower than the specified values. In the manoeuvring simulations, only constant forces are used (no wind gust, no varying wave forces). First, the start-up time for the build up of these forces has to be specified. Second, the time has to be specified at which the approach is started. Finally the simulation can be continued after the approach has finished. This enables to simulate the time needed to couple the FPSO to the shuttle tanker. Furthermore, it is possible to specify a time step for data logging (not yet shown in the GUI prototype screen above).

70 Report No CPO 69 Finally, it will be possible to switch on or off the wind, current and wave shielding predictions separately (not shown yet in the GUI prototype screen). When switched off, the unshielded forces will be used. By pressing the 'run' button, the simulation is started. It is also possible to add the scenario to a batch list of runs. By pressing 'execute batch', all runs in the list are executed. A description or comment field is available for each run.

71 Report No CPO ANALYSER With the analyser, the results of the simulations can be analysed. A simulation can be analysed, only after it has finished. The analyser is part of the GUI and has three tabular screens: 1) Time traces 2) Statistics 3) Movie 17.1 Analyser functionality Time traces The screen below shows the particulars of the time traces screen. First, a project and a run have to be selected. This is accomplished by selecting a run in the tree-view of an available project. Then, a signal for plotting has to be selected. A pull-down menu shows all the available signals. A selection can be made from a basic data set (most important signals) and an extended data set (see section 17.2). The plot can be given a name (for export to a file). Zooming is possible. A filter can be applied by specifying the lower and upper frequencies of the filter. All frequencies in between are passed. All other frequencies are filtered from the plotted signal. The following plot options are available: 1) Plot a signal 2) Clear the plot

72 Report No CPO 71 3) Export plot to file (for external use, i.e. reporting) Multiple signals can be plotted in one plot. The signals are cleared from the plot by pushing the 'clear' button. The plot can be exported to a file. Results of several runs can be compared in the plot screen Statistics The screen below shows the particulars of the time traces screen. First, a project and a run have to be selected. This is accomplished by selecting a run in the tree-view of an available project. Then, a signal for statistical analysis has to be selected. A pull-down menu shows all the available signals. A selection can be made from a basic data set (most important signals) and an extended data set (see section 17.2). The statistical table can be given a name (for export to postscript). The values to be computed can be specified. The following options are available: mean value standard deviation maximum value minimum value Furthermore, the lower and upper time level for the statistical analysis can be specified. A filter can be applied by specifying the lower and upper frequencies of the filter. All frequencies in between are passed. All other frequencies are filtered from the signal before the statistical analysis. The number of decimal points can be specified. The table can be cleared and can be exported to an ASCII file.

73 Report No CPO Movie or track plots The screen below shows the particulars of the movie or track plot screen. The movie or track plot shows the vessel contours at a fixed time interval. First, a project and a run have to be selected. This is accomplished by selecting a run in the tree-view of an available project. Then a play ratio has to be selected. A play ratio of 1 means the movie is shown real-time. A play-ratio of 2 means the movie is shown twice as fast as real time etc. This ratio can be altered while the movie is playing. A name can be given to the movie for export to a file (file format has not been decided yet). The following movie options are available: Zoom in (centre of zoom is centre of the mooring system) Zoom out Play Pause Stop 17.2 List of computed signals The set of computed signals consists of two parts: 1) A part which is always available to the user of the analyser 2) A part which is available only after selection by the user of the analyser The first part consists of signals that are of primary interest to the user. The second part consists of signals that are not always of primary interest to the user, and are only necessary when a detailed analysis of the results is required. This approach avoids long lists of signals from which a selection has to be made.