Extreme Seas     Design for Ship Safety in Extreme Seas
 
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Extreme Seas Workplan

Workpackage 1 - Modelling of propagation of extreme waves
Task 1.1 - Detecting and analyzing wave envelopes.
Task 1.2 - Dynamical simulations of intensive waves' growth within the models of different accuracy
Task 1.3 - Fully nonlinear simulations of extreme wave events
Task 1.4 - Comparison of wave simulations with model test results
Objectives:
This workpackage intends to provide a description of the evolution of extreme and extraordinarily large waves in time and space by non-linear solutions and to explain mechanisms responsible for generating of extreme events.
A systematic investigation of extreme waves, in directionally spread seas, when several wave trains are present will be carried out. The mathematical models will allow investigating surface elevations and significance of local interactions.
The formulations developed will be used to generate realistic ocean surface fields for numerical and laboratory model tests with respect to ship structure design. The mathematical models developed will be compared with wave records obtained in WP5 with this specific objective in mind.
Relevant results of the EU projects ADOPT and HANDLING WAVES as well as findings of the ROGUE WAVES 2008 Workshop will be utilized.

Workpackage 2 - Probabilistic description of waves for design
Task 2.1 - Wave statistics from field and model basin data
Task 2.2 - Wave statistics from theoretical model simulations
Objectives:
The aim of the work package is to provide probabilistic description of waves for ship design. This will include mainly short-term statistics. The wave models developed in WP 1 will be used to generate wave records from which statistics of critical wave parameters will be derived. Both time and space statistics will be studied. Short-term sea surface characteristics will be studied based on field data from the North Sea supplied by Metno. The goal is to further validate modern non-linear wave models established in WP 1 and the wave models commonly used for design, by establishing the corresponding probability distributions.
A definition of extreme sea states and of the extraordinarily large or rogue events will be aimed at. Relevant results of the EU projects ADOPT and HANDLING WAVES as well as findings of the ROGUE WAVES 2008 Workshop will be utilized.

Workpackage 3 - Long-term trends and warning criteria for extreme waves
Task 3.1 - Long term wave statistics
Task 3.2 - Warning criteria
Objectives:
The aim of this work package is to understand and define long-term trends of wave data including extraordinarily large wave events and to provide definition of warning criteria for extreme waves for marine structures and to implement them in a weather forecast system.
The majority of today ocean-going ships are designed for the North Atlantic long-term wave climate based on statistics derived from visual observations. The accuracy of these data is not sufficiently adequate. The objective of this WP is to compare this data to long-term wave statistics derived by numerical model hindcasts and existing observations.
Accuracy of the visual observations will be pointed out with emphasis on consequences for design.
A definition of extreme sea states and extreme wave events will be aimed at leading to the different types of warning criteria. Relevant results of the EU projects ADOPT and HANDLING WAVES as well as findings of the ROGUE WAVES 2008 Workshop will be utilized.

Workpackage 4 - Numerical tools for ships in extreme seas
Task 4.1 - Levels of accuracy in a standard nonlinear sea-keeping program
Task 4.2 - Extending capabilities of a time domain strip theory based code
Task 4.3 - Computational system for hydro-elastic response of ships
Task 4.4 - Comparison of numerical and experimental results
Objectives:
Nonlinear waves from WP 1 will be represented with different levels of accuracy in standard types of nonlinear seakeeping programs. The WP 2 results will be utilized. The required domain size in the nonlinear wave simulations in order to facilitate sufficiently long sea-keeping analyses will be studied. The ship responses, such as midship bending moment or slamming load, is calculated by the various nonlinear sea-keeping codes in nonlinear waves. The effect of changing positions in the nonlinear wave field will be assessed. The main goal is to develop an efficient method for the prediction of extreme response events from the nonlinear wave field. This workpackage will collaborate closely with WP 6. When the extreme response event is identified, a fully nonlinear sea-keeping code will be used to get more accurate response calculations. Four ship types will be considered: a modern container vessel, a passenger ship, an LNG carrier and a product or chemical tanker. The vessels of the length between 150m and 200m will be considered as these vessels are more prone to extreme and rogue waves. Some adjustment of a size of the vessels may take place during the project development. Improvements will be verified using existing benchmark cases, and validated using the results of WP 5.

Workpackage 5 - Model tests
Task 5.1 - Generation of Abnormal Wave Sequences and Irregular Sea States
Task 5.2 - Measurements and Analysis of Abnormal Wave Kinematics
Task 5.3 - Construction and Instrumentation of Ship Models
Task 5.4 - Model Tests in Abnormal and Extreme Wave Conditions
Objectives:
The wave structural loads induced on ships by extreme and extraordinarily large waves are dominated by very complex hydrodynamic and hydro-elastic effects. Since the discussion on extraordinarily large wave effects on ship structures is relatively recent, the related phenomena are still largely unknown. Furthermore, due to the complexity of the phenomena, reliable information regarding the structural responses to these waves can only be obtained experimentally.
The experimental data can then be used to update and verify state of the art numerical models. However as existing experimental data of this type is very limited, this workpackage will provide experimental data to validate the theoretical wave models in WP1 and 2. In particular, measurements will be made of wave kinematics as most of the currently available data has concentrated only on free surface elevation. Both deterministic time series with individual large waves and irregular wave time series will be produced.
In this work package experimental tests will be carried out with wave sequences including extraordinarily large waves.
The first part of the tests consists on generating the target deterministic wave sequences with inserted extraordinarily large waves, both long crested and short crested (by TUB) and short crested (by CEHIPAR), and measure the kinematic characteristics of these waves. On the second part of the tests ship models, instrumented to measure motion and structural responses, are tested in the previous wave sequences.

Workpackage 6 - Probabilistic response based design methodology and tools
Task 6.1 - Identification of critical wave scenarios
Task 6.2 - Response based design tools for extreme and extra-ordinarily large waves
Task 6.3 - Simplified approaches for extreme response calculations in extr. & extra-ordinarily large waves
Objectives:
The objective of this work package is to develop response based design methodology and tools for ships exposed to extreme and extraordinarily large waves. The design methodology and tools will use the new wave data and models from the wave work packages 1-3 as well as the analysis tools developed in the ships response work package 4. Short term and long term statistics of vessel response, and characteristic response parameters, will be determined, and implemented in the design tool. The design tool in combination with the wave data and simulation tools will then constitute an integrated package as basis for estimation of the reliability of ships for design.
The model tests carried out by TUB and CEHIPAR provide both partners with valuable information on the seakeeping behaviour and green water on deck of the investigated model ships. Therefore it is necessary that TUB and CEHIPAR will provide their experience and give advice to the corresponding partners of work package 6.
Particular attention will be given to the trade off between analysis accuracy and computational costs for different analysis purposes, i.e. development of cost-efficient procedures for the specific analysis objectives at hand. The WP will further provide simplified recipes for extreme response calculations.

Workpackage 7 - Implementation to ship design procedures
Task 7.1 - Definition of design scenarios
Task 7.2 - Numerical simulation studies
Task 7.3 - Recommendations
Objectives:
Design scenarios will be considered using existing models and tools and the newly develop ones (new wave data and models as well as new ship response simulation and design tools). Consequences for the currently used procedures for ship response analysis will be documented. The North Atlantic wave environment will be used in the analysis as well as areas along the Norwegian coast defined as dangerous areas in Den Norske Los. Recommendations for ship design will be provided. The warning system implemented in WP 3 will be tested on a trial user (passenger ship).

Workpackage 8 - Dissemination and Exploitation
Task 8.1 - Technical management
Task 8.2 - Dissemination
Task 8.3 - Exploitation
Objectives:
This WP aims at dissemination of the results as they become available and the planning of their exploitation after the end of the project. It aims also at technical management of the project related to the role of the Project Coordinator and the Technical Project Manager.

Workpackage 9 - Administrative Management
Objectives:
This workpackage will aim at the management of the project throughout its duration, starting with drafting of a Consortium Agreement at the outset of the project.

 
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