Jean-Marc Rousset

The Transient and Progressive Flooding Stages of Damaged Ro-Ro Vessels: A Systematic Review of Entailed Factors

Roll-on/roll-off vessels appear to be sensitive to rapid capsizing due to an abrupt ingress of water caused by maritime accidents. As a result of the damage creation, the flooded ship can experience intermediate stages, which might be more devastating than the final condition, as the sudden loading could significantly alter the ship stability characteristics. Far from a probabilistic analysis, the paper under study presents the state-of-the-art in regards to flooding physics by treating some relevant important topics. It sheds light on the transient and progressive flooding stages, focuses on relevant factors, and suggests combinations between factors that strongly affect the flooding before the steady state is reached. Furthermore, the authors comment on some points, which remain difficult to take into consideration either numerically or experimentally, and propose, where found necessary, recommendations for a more reliable assessment of the flooding process. This review shows that the intermediate flooding phase depends upon many factors, and its assessment could be adequate in calm water condition. The effects and interdependency between these factors still require further investigation. Therefore, we recommend carrying out a wide range parametric investigation into these factors, which consider their interdependency and encourage the application of the design of experiments methodology.

An experimental study on the flooding of a damaged passenger ship

Some recent marine incidents have shown that damaged Ro-Ro ferries can be extremely vulnerable to loss of stability. After an abrupt ingress of water caused by a maritime accident, flooding of the spaces below the car deck may endanger the ship and eventually lead to its sinking within a short period of time. The flooding stages depend upon many factors pertaining to the vessel, the accident, and the environment. Some of these factors interact during the flooding. An experimental investigation using an International Towing Tank Conference (ITTC) Ro-Ro ferry was carried out to provide a thorough insight into the flooding physics. Both transient and progressive phases are found to be highly dependent upon water and air behaviours. The damage area, the time of damage creation and the air ventilation level inside damaged compartments are key factors in determining the final ship state.

A Method of Immersed Surface Capture for Broaching Application

The modeling of ship behavior in astern seas requires a large range of maneuverability and seakeeping knowledge since the understanding of the ship motions returns to solve a fluid structure interactions problem between waves and the ship hull. The broaching phenomenon is known as an abrupt change in motion in the horizontal plane, resulting in a loss of ship’s heading. It is characterized by a sudden divergence of yaw. Thus, there is a transfer of the kinetic energy on the roll axis that increases the risk of ship capsize. In the aim of modeling this phenomenon, the developed model uses the capture of the intersection between the ship hull and the free surface. Thus, we can overcome the hydrostatic stiffness matrix and integrate directly the hydrostatic pressure on the immersed surface. This method has the advantage of taking into account non-linearities of the wave profile into the calculation of the immersed surface, directly by performing a remodeling of the facets near the free surface. In the literature, three main factors are likely to affect the stability: the loading of the vessel, the presence of external disturbance torques and inadequate conditions of navigation, as is the case when a ship is caught in a storm. The first two factors are taken into account in the study of static stability, while the third factor is considered in the study of the instantaneous stability. Hydrostatic behavior of a ship is interesting when one wants to know her intact stability limits in calm seas. However, in the study of the ship behavior in following seas, the ship is no longer in usual conditions of navigation, but in unsuitable conditions requiring the study of the instantaneous stability. In the model formulation, the dynamic torsor comes from the general non-linear maneuverability equations and the time advance is solved by a 4th order Runge Kutta scheme with a constant time step. The torsor of the total applied mechanical action on the ship hull is expressed as the superposition of six torsors (gravity, hydrostatic, Froude Krylov, radiation, hydrodynamics and maneuverability) expressed in the center of gravity of the ship. Thus, we obtain a strong coupling between the maneuverability and seakeeping equations. Validation cases will be conducted and presented. The improvement of the model will require the implementation of test campaigns that will be specific for the study of ship behavior in astern seas. Validation of the model will help to define new stability criteria for ships in wave.Copyright

Investigating the Transient Flooding and Sloshing in Internal Compartments of an ITTC Damaged Ro-Ro Passenger Ferry: Part II—Experimental Analysis

Passenger Ro-Ro ferries have proved to be extremely vulnerable regarding their hydrostatic stability when damaged. This is not only due to the design of their car decks. After an abrupt ingress of water caused by a maritime accident, the spaces below the car deck can experience dangerous intermediate flooding stages that might lead the ship to sink. The intermediate flooding stages depend upon hosts of factors that are interdependent. Some of them eventually interact during the flooding. An experimental campaign using the midsection of the PRR02 - ITTC/SiW passenger Ro-Ro ferry was devoted to provide a thorough insight to the flooding physics and to quantify these interactions using a novel-to-ocean-engineering methodology, the so-called DOE method. The physical background and the experimental set up of this campaign are presented in the previous one (OMAE2010-20047). This paper is devoted to presenting the experimental methodology and the first findings. The flooding is found a complex phenomenon in which a strong interaction between water and air occurs, also in coupling with the hydrodynamic efforts. Model tests based on one-factor-at-a-time experiments highlights the importance of the damage area and the time of damage creation in the ship behavior during the transient phase. We advocate the use of the DOE methodology to deal with stability problems and to find a model quantifying the intermediate flooding stages.Copyright

On the Transient and Progressive Flooding Stages of Damaged RO-RO Vessels

Roll-On/Roll-Off vessels appear to be sensitive to rapid capsizing due to abrupt ingress of water caused by maritime accidents. As a result of the damage creation, the flooded ship can experience intermediate stages which might be more devastating than the final condition, as the sudden loading could significantly alter the ship stability characteristics. Far from a probabilistic analysis, the present paper aims at contributing to enhance knowledge of the flooding physics by treating some relevant important topics. It sheds light on the transient and progressive flooding stages, focuses on relevant factors and suggests combinations between factors that strongly affect the flooding before the steady state is reached. Furthermore, the authors comment on some points which remain hard to take into consideration, whatever the adopted methodology is, and propose, where found necessary, recommendations for a more reliable assessment of the flooding process. This survey shows that the intermediate flooding phase, which assessment could be adequate in calm water condition, depend upon many factors whose interdependency and effects still require further investigation. May a novel assessment methodology lead us to a better understanding and facilitate, therefore, the framing of new damage stability regulations.Copyright

Experimental and Numerical Comparative Investigation of Pressure Fields Under Steep 2D Waves

In the present work is presented a recently developed fully-nonlinear spectral Numerical Wave Tank (NWT) model, named HOST-wm2, and its capabilities for reproducing highly-nonlinear evolutions in a wavetank are evidenced on experimental comparisons. This fully-spectral model is based on a Higher-Order Spectral (HOS) method, which ensures high levels of accuracy and efficiency, thanks to the fast resolution made by FFTs only. This numerical method is dedicated to model wave basins and a specific care is paid to fit the experimental wavetank characteristics (are included, the physical geometry of the wavetank, the snake-type wavemaker, an absorbing beach, ...). The numerical simulations are successfully compared to experiments conducted in cooperation with Ocean Power Delivery (OPD) in the wavetank of the Ecole Centrale de Nantes (ECN). Comparisons for wave elevation and pressure fields under highly-nonlinear steep 2D waves are reported. The usefulness of the presented NWT to assist experiments is also illustrated on the assessment of the procedure used to extract the pressure gradient from the experimental pressure signals.Copyright