Numerical Investigation on Flood Water Sloshing Influence on Intact and Damaged Stability of Ship

Sloshing affects the intact and damage stability of the ship, which causes variation in dynamic metacentric height (GM) under critical load conditions. The transient flooding soon after the ship damage is analyzed, with floodwater accumulation in large space and causing the ship to suffer huge heel angles. The ship motion and stability changes when sloshing becomes high in partially flooded compartments. Most of the previous researches focus on the motion response of ship alone, hence the variation of stability due to sloshing is to be more critically studied. In the present study, three critical damage locations are identified and flooding through these locations are analyzed using the volume of fluids method. The method focus on finding damage ship motion response, flood water dynamics, and coupled dynamics of both. This is studied using the numerical method FLOW3D. Motion and stability behaviour will be different for different damage locations; hence portside, starboard-side, and aft-end bottom damage cases are considered. The effect of compartment shape and damage location on motion response and stability of the damaged ship is highlighted.

Quasi-Static Flooding Analysis Method of a Damaged Ship Considering Oil Spill and Cargo Load

When a ship is damaged at sea, it is important to predict its behavior as well as whether it is to sink or not. If the ship comes to an equilibrium, the equilibrium position and time should be estimated; otherwise, the time to sink should be estimated. Furthermore, flooding analysis should be carried out not only during the design stage of the ship for preventive reasons, but also after an accident for a better investigation of its causes. In addition, flooding analysis methods that can provide predictions in case of an accident are of particular importance, as there is no time for the required calculations in an emergency. For this purpose, a quasi-static flooding analysis method for the damaged ship in the time domain is proposed in this study. There are a number of studies in which the equilibrium position and time were estimated by flooding analysis. However, most of them have not considered the air pressure effect in fully flooded compartments, and the method of determining the fluid volume in these compartments was not accurate. In the present study, the virtual vent and accumulator method are used to calculate the reference pressure in the fully flooded compartments, and the compartment shape is considered by using polyhedral integration. Also, spilled oil and solid cargo items from the damaged ship are taken into account for realistic flooding analysis. Finally, the damage stability criteria were checked not only in the final state, but also during the entire time of the flooding, as the intermediate states can be more hazardous than the final state. To validate the feasibility of the proposed method, it was applied to a naval ship, which is considerably more stringent for damage stability. As a result, we checked the availability of this study.

Towards Self-organized Control: Using Neural Cellular Automata to Robustly Control a Cart-pole Agent

Neural cellular automata (Neural CA) are a recent framework used to model biological phenomena emerging from multicellular organisms. In these systems, artificial neural networks are used as update rules for cellular automata. Neural CA are end-to-end differentiable systems where the parameters of the neural network can be learned to achieve a particular task. In this work, we used neural CA to control a cart-pole agent. The observations of the environment are transmitted in input cells while the values of output cells are used as a readout of the system. We trained the model using deep-Q learning where the states of the output cells were used as the Q-value estimates to be optimized. We found that the computing abilities of the cellular automata were maintained over several hundreds of thousands of iterations, producing an emergent stable behavior in the environment it controls for thousands of steps. Moreover, the system demonstrated life-like phenomena such as a developmental phase, regeneration after damage, stability despite a noisy environment, and robustness to unseen disruption such as input deletion.

EFFECT OF WATERTIGHT SUBDIVISION ON DAMAGE STABILITY OF RO-RO FERRIES

Effect of various subdivision arrangements of ro-ro vessels on damage stability is discussed. The arrangements included single and double sides both below and above the car deck, with and without a double buoyant car deck, and with or with- out a watertight tween deck below the car deck. This gave as many as 16 various arrangements for each compartment length. The double sides both above and below the car deck are of the same width b = 0.1B. The double bottom, when not flooded, worsens damage stability. The car deck and tween decks should be ‘openwork’, to be transparent for water and air. Oth- erwise, the ship can capsize at the very initial stages of flooding. Double sides and a double car deck together improve con- siderably damage stability, both in terms of maximum arm and range. A new characteristic was introduced, termed the critical deck height. Flooding a deck above the critical height leads to a rapid capsizing of the ship.

SOLAS 2009 STABILITY REQUIREMENTS: IMPLEMENTATION

January 2009 saw the introduction of substantial changes to SOLAS, commonly referred to as SOLAS 2009. Not only have significant parts of Chapter II-1 completely changed, but so have the methodologies for assessing survivability of certain ship types. This paper provides an overview of some of the main topics and how Lloyd’s Register is adapting to provide necessary industry solutions and support, immediately and into the future. It provides an insight into the probabilistic requirements, our approval processes, developments and our participation in defining industry standards. It is evident in this paper that the discussions predominantly revolve around passenger ships. This is due to their complexity and the conflict between the new regulations for survivability assessment moving from a restrained deterministic requirement to a risk-based probabilistic solution. It also highlights real issues over the difficulties of implementing this methodology. This conflict in overall design is less pronounced for dry cargo ships, which did not have to comply with a general damage stability standard until 1992 when the probabilistic concept was introduced for dry cargo ships only. Under SOLAS 2009, a modified requirement has been implemented. However, the fundamental issues remain the same.

NAVAL ARCHITECTURAL CONSIDERATIONS IN THE DESIGN OF FLOATING DOCK

A brief introduction about floating docks, its advantages and types have been described. The naval architectural considerations which play a significant role in the design of floating dock have been explained. Typical ratios of L/B and L/D as a function of Dock’s lifting capacity have been presented. Empirical formulation for the same have also been indicated wherever applicable. Intact stability and its criterion as applicable for a floating dock have been described. Critical positions during evolution of docking operation and important considerations while performing stability calculations have been highlighted. Attention has also been drawn to the damage stability of floating dock. Aspects of longitudinal and transverse bending moment, which are the governing aspects in the scantling calculations have been described. Also typical methods for securing and mooring of floating dock, without compromising on flexibility for docking operations have been described. Methodology and consideration which has to be kept in mind while using design software (such as NAPA) have been indicated. Simple size optimization techniques which result in steel / ballast volume reduction have also been explained.

Tumblehome Ships - From Greek Triremes to the Zumwalt

After almost a century the US Navy has reintroduced tumblehome into the design of naval combatants. This paper discusses some of the reasons tumblehome was originally designed into ships and why it served it owners well for many centuries. The transition from sail to steam power a little over a century ago led to a variety of problems with the combatant ships designed with tumblehome where the lack of damage stability caused a major loss of life as these ships sank so quickly. During World War I ships designed with tumblehome fell out of favor and some of the ships were actually modified to remove the tumblehome from the design. These changes in the design of tumblehome ships are discussed in this paper.