Workpackages

Workpackage 2: Flooding progression modelling

Objectives

The main objective of this Work Package is to extend knowledge about partitions safety concerning flooding effects. This main objective can be split into the following partial objectives:

Partial objective 1:

• Obtaining results of leaking and collapsing structures (partitions) by conducting experimental study with the use of new build mock-up test stand

Partial objectives 2:

• Obtaining results of numerical analyses of leaking and collapsing structures (partitions)
• Development of easy-to-use criteria for the partitions in flooding simulation

Partial objective 3:

• Evaluating water flow characteristics through various openings by experimental means

Partial objective 4:

• Evaluating water flow characteristics through various openings by computational means
• Assessing the ventilation effect related with the flow of air inside the inner structure of the vessel)

Partial objective 5:

• Further insight in water flow around and through typical cruise vessel cabin arrangements
• Insight in required level of detail and scale in the modelling of cabin arrangements in flooding simulation programs

partial objective 6:

• Assessing the sensitivity of flooding simulation tools to variations in the input data (discharge coefficients, critical pressure heads, etc.)

Description of work

Task 2.1 Experiments with leaking and collapsing structures
(Responsible: CTO; STX, MEC, MW, AALTO)

The scope of the first part of the following Work Package includes experimental investigation of leaking and collapsing structures (partitions) with a use of new build mock-up stand. The work is divided into two stages:

Sub-Task 2.1.1 Planning and preparations for the tests
(Responsible: CTO, Participants: STX, MEC, MW, AALTO)

Design of the test stand for static pressure loading of the ship structure mock-ups (e.g. walls with cabin, fire doors or SWT-doors). One of the most important parts of the test stand gains the form of a watertight tank with one exchangeable wall where the structure to be tested are installed. The tank will be fitted with piping system for static pressure adjustment. The other elements of the test stand design include the measurement and monitoring equipment arrangement for stress distribution within the structure and for measuring of the flow rate through the leakages during the structure collapse. The shipyards (and/or their sub-contractors) will provide the ship structure mock-ups which will be selected for testing, as well as the information and data of them in co-operation with the designer and manufacturer of the test stand and the research organisation carrying out the tests.

Sub-Task 2.1.2 Experiments
(Responsible: CTO)

Conduction of the measurements with different types of full size structures. In this case the model basin will be used enabling controlled conditions of water outflow. Furthermore the capabilities provided by the model basin infrastructure enable construction of the static pressure piping installation at least 7 m above the basin bottom level as well as the effective operation of the mock-up. During the measurement the testing stand will be filled with water gradually up to the structure collapse. The tested structure will be monitored with respect to the loading (pressure) and stress distribution. After the structure collapse and the loss of watertight integrity the rate of outflow will be measured. It is planned to conduct a series of 24 tests for particular mock-up arrangement.

Task 2.2 Numerical modeling and criteria for leaking and collapsing structures
(Responsible: MEC)

Sub-Task 2.2.1 Numerical studies and analysis of leaking and collapsing structures
(Responsible: MEC, Participants: CTO)

The aim of second part of this task is to study the failure mechanisms for doors and structural components on the way of numerical simulations. The simulations will be carried out using explicit finite element code LS-Dyna, MSC Patran/Nastran. However the pressure will be applied statically, the structural response might vary significantly over the short duration of simulations time. With respect to these effects the dynamic approach should be used. Moreover explicit code provides much efficient opportunities of modelling of the failure propagation.

It is expected that two main pressure values will describe the failure process. The failure process begins when the structure looses its watertight integrity and starts to leak- this stage is described by the leakage pressure. Failure process continues until the collapse of the structure, which is described by the collapse pressure. At any time, the extent of failure can be described by the area of leakage opening. Computations will be validated with the experiments conducted under Sub-Task 2.1.2.

Sub-Task 2.2.2 Development of easy-to-use criteria for the flooding simulation
(Responsible: STX, Participants: CTO, MEC, MW, NAPA, AALTO)

Based on the experiments and the finite element simulations in Sub-Task 2.1.2 and in Sub-Task 2.2.1, the estimated risk criteria of leakage and collapse of doors and other structural elements will be proposed.

Task 2.3 Experimental studies on pressure losses
(Responsible: AALTO, Participants: STX, MW)

This task will be devoted to hydraulic experiments on specific configurations encountered in the flooding of a large passenger vessel. Special attention is put on the cross-flooding arrangement. The detailed parts of the ship to be tested will be selected. Tests with different modifications of a typical arrangement will be performed in order to derive conclusions on the effects of parameters, such as the number of girders and openings. In addition, doorways, manholes, down-flooding hatches, etc. will be tested. Large scale models will be used in order to minimize the possible scale effects. Measurements will be carried out in dynamic case, which enables the results to be used both in conceptual mathematical models and in the validation of the CFD-codes.

Task 2.4 Computational studies & RANSE CFD
(Responsible: CNRS, Participants: STX, CTO)

Sub-Task 2.4.1 Computational studies
(Responsible: CNRS, Participants: CTO)

This task will deal with CFD computations on detailed parts of the ship among them will be (not exclusively) the configurations chosen in Task 2.1 and/or Task 2.3. These CFD computations will be used to provide a global and simplified flood-simulation tool with unknown coefficients (pressure loss in various openings, for instance). Since the number of configurations of interest is very large, these computations are distributed among two CFD partners, CNRS using their in-house RANSE solver ISIS-CFD and CTO using Fluent. Some cases will also be computed in model scale in order to study the scale effects. Furthermore, two test cases will be computed by both project participants.

Sub-Task 2.4.2 Effects of air compression
(Responsible: CTO, STX)

This task will treat the important and often neglected effects of air ventilation on progressive flooding. A systematic analysis on the ventilation in typical compartments of a modern passenger ship is performed and the effects of air compression in the case of flooding are studied. Furthermore, Dedicated CFD simulations will be carried out by CTO in order to assess the pressure losses in typical air pipes from the voids since the counter pressure of air can have a significant effect on the cross-flooding time. The compressibility of air is taken into account in the computations.

Task 2.5 Model tests for cabin areas
(Responsible: MARIN, Participants: STX, MW, NAPA)

In the EC funded SAFEDOR project flooding in RoPax ferries is investigated by means of model tests on cabin arrangements and simulations for ships. This work focuses on basic cabin arrangements with not too much level of detail. All available results from the previous studies will be used as a starting point for this new study in Task 2.5.

Sub-Task 2.5.1 Flooding tests on detailed cabin arrangements
(Responsible: MARIN, Participants: STX, MW)

Flooding tests on detailed cabin arrangements of a large cruise passenger ship model will be carried out. The arrangements will contain a substantial amount of cabins while the cabins will be modelled in two levels of detail (furniture, doors, etc.).

Sub-Task 2.5.2 Scale effects
(Responsible: MARIN, Participants: STX, MW)

Flooding tests will be performed on two identical cabin arrangements in different scale to investigate scale effects due to different sized openings, Reynolds numbers and air compressibility effects.

Sub-Task 2.5.3 Guidelines
(Responsible: MARIN, Participants: STX, MW, NAPA)

MARIN and NAPA will perform flooding simulations with different detail levels for the modelling of the cabin area. Based on the simulations and model tests guidelines will be derived on how to model cabin arrangements in flooding simulation programs. The guidelines will address issues like required level of detail, recommendations for discharge coefficient values and when and how to include air compressibility effects.

Task 2.6 Sensitivity of simulation model
(Responsible: AALTO, Participants: NAPA)

This Task will consist of simulations with a typical layout of ship. The input parameters of the simulations will be systematically varied in order to assess the sensitivity of the simulation results on these parameters. The sample ship designs produced in the WP1 will be used. Guidelines for the preferred accuracy of the input data along with simple error estimations will be provided.

Deliverables

• D2.1a Description of the mockup and test procedure;list of structures to be tested, month 3 (CTO)
• D2.1b Report on the experimental study on the critical pressure heads, month 15 (CTO)
• D2.2a Report on the numerical study on the critical pressure heads, month 17 (MEC)
• D2.2b Guidelines and criteria on leakage occurrence modelling, month 23 (CTO)
• D2.3 Report on the experimental study on the pressure losses in openings, month 14 (AALTO)
• D2.4a Results of the computational study on the pressure losses in openings, month 17 (CNRS)
• D2.4b Results of the studies on the pressure losses in air pipes and effects of ventilation, month 17 (CTO, STX)
• D2.5a Draft report on flooding tests on detailed cabin arrangements, month 11 (MARIN)
• D2.5b Report on flooding tests on detailed cabin arrangements and the effects of different scale, month 17 (MARIN)
• D2.5c Guidelines on modelling principles for cabin areas, month 23 (MARIN)
• D2.6 Sensitivity analysis for the input data in flooding simulation, month 32 (AALTO)