Optimización del diseño holístico de buques: embarcaciones mercantes y navales

The present paper provides a brief introduction to a holistic approach to ship design optimization, defines the generic ship design optimization problem, and demonstrates its solution by using advanced optimization techniques for the computer-aided generation, exploration, and selection of optimal designs. It discusses proposed methods on the basis of some typical ship design optimization problems of cargo and naval ships related to multiple objectives, leading to improved and partly innovative design features with respect to ships’ economy, cargo carrying capacity, safety, survivability, comfort, required powering, environmental protection, or combat strength, as applicable.Este documento brinda una breve introducción a un enfoque holístico a la optimización del diseño de embarcaciones, define el problema genérico de la optimización del diseño de embarcaciones y demuestra su solución mediante el uso de técnicas avanzadas de optimización asistidas por computador para la generación, exploración y selección de diseños óptimos. Discute los métodos propuestos sobre la base de algunos problemas típicos de optimización de diseño de embarcación de buques de carga y navales relacionados a los objetivos múltiples, conllevando a características de diseño mejoradas y parcialmente innovadoras con respecto a la economía de la embarcación, capacidad de carga, seguridad, supervivencia, comodidad, potencia requerida, protección ambiental o fortaleza de combate, como sea aplicable

On Nonlinear Simulation Methods and Tools for Evaluating the Performance of Ships and Offshore Structures in Waves

This paper describes the development of alternative time domain numerical simulation methods for predicting large amplitude motions of ships and floating structures in response to incoming waves in the frame of potential theory. The developed alternative set of time domain methods simulate the hydrodynamic forces acting on ships advancing in waves with constant speed. For motions’ simulation, the diffraction forces and radiation forces are calculated up to the mean wetted surface, while the Froude-Krylov forces and hydrostatic restoring forces are calculated up to the undisturbed incident wave surface in case of large incident wave amplitude. This enables the study of the above waterline hull form effect. Characteristic case studies on simulating the hydrodynamic forces and motions of standard type of ships have been conducted for validation purpose. Good agreement with other numerical codes and experimental data has been observed. Furthermore, the added resistance of ships in waves can be calculated by the presented methods. This capability supports the increased demand of this type of tools for the proper selection of engine/propulsion systems accounting for ship’s performance in realistic sea conditions, or when optimizing ship’s sailing route for minimum fuel consumption and toxic gas emissions

Stochastic life cycle ship design optimization

In the presented research study, a parametric model of a bulk carrier design is utilized in order to explore the technical and economic ship design features (design attributes) in the frame of a stochastic optimization procedure. The life cycle assessment of a newbuilding's investment that includes ship's acquisition and operation cost for ship's life cycle is affected by a variety of cost and other parameters have an inherent uncertainty. The ship design attributes are herein represented by six main ship parameters that define the basic characteristics of a vessel: length, breadth, depth, draft, block coefficient and speed. Among the ship characteristics that are related to high uncertainty are ship's energy consumption in terms of fuel consumption, fuel mix and fuel prices. In the present paper, an attempt is made to investigate how the uncertainty of estimations of the fuel consumption, fuel mix and prices, which are made at an early stage of ship design, can affect the outcome of the ship design optimization procedure with respect to ship's life cycle cost. Therefore, a stochastic optimization procedure is being applied, which is utilizing well established optimization algorithms and techniques in a robust and efficient manner. Sample results of this stochastic optimization are compared with solutions of a deterministic optimization and eventually lead to a rational basis for the decision making regarding the life cycle assessment of ship investments

Parametric design and multiobjective optimization of containerships

The introduction of the energy efficiency design index (EEDI) and ballast water treatment regulations by the International Maritime Organization, the fluctuation of fuel price levels, along with the continuous endeavor of the shipping industry for economic growth and profits has led the shipbuilding industry to explore new and cost-efficient designs for various types of merchant ships. In this respect, proper use of modern computer-aided design/computer-aided engineering systems (CAD/CAE) extends the design space, while generating competitive designs with innovative features in short lead time. The present article deals with the parametric design and optimization of containerships. The developed methodology, which is based on the CAESES/Friendship-Framework software system, is demonstrated by the conceptual design and multiobjective optimization of a midsized, 6500-TEU containership. The methodology includes a complete parametric model of the ship’s external and internal geometry and the development and coding of all models necessary for the determination of the design constraints and the design efficiency indicators, which are used for the evaluation of parametrically generated designs. Such indicators defining the objective functions of a multiobjective optimization problem are herein the EEDI, the required freight rate, the ship’s zero ballast container box capacity, and the ratio of the above to below deck number of containers.The set-up multiobjective optimization problem is solved by use of the genetic algorithms, and clear Pareto fronts are generated. Identified optimal design proves very competitive compared with the standard containership designs in the market

Advanced damage stability assessment for surface combatants

One of the major contributors to the survivability of a surface combatant is her reduced vulnerability to weapon effects and as such the ship's damage stability characteristics determine a ship's ability to resist the consequences of possible flooding, namely to not capsize and/or sink. There are serious concerns about the limitations of the current semi-empirical deterministic criteria in which a combatant's damage stability is assessed upon. This paper details a comparison between the current approach and a newly presented probabilistic approach with the aim of determining which will result in a more accurate way of estimating the level of survivability of a particular design. A study is also presented in which the maximum damage length used in the naval ship assessment is increased to merchant ship standards of 0.24L bp

Assessment of survivability of surface combatants after damage in the sea environment

The operating conditions of modern warships, in the natural sea environment, have a significant influence on their survivability in the event that watertight integrity is lost. Up to now, the consideration of sea and weather conditions has been implicitly accounted for in a naval ship’s damaged stability assessment. This paper outlines a probabilistic approach to assessing a naval ship’s damage stability, in which some of the limitations of the currently used damage stability criteria are identified, including the validity of the assumption of moderate sea states at the time of damage. An investigation into the operability of a frigate design found that there is a significant increase in the risk of a ship’s loss when changing the operational area from the North Atlantic to the North Pacific. A remarkable additional finding of the study showed that the assumed distribution for the damage penetration has no significant effect on the ship’s survivability due to the way modern combatants are designed

Parametric design and multi-objective optimisation of containerships

The introduction of new regulations by the International Maritime Organisation, the fluctuation of fuel price levels, along with the continuous endeavour of the shipping industry for economic growth and profits has led the shipbuilding industry to explore new and cost-efficient designs for various types of merchant ships. In this respect, proper use of modern computer-aided design/computer-aided engineering systems (CAD/CAE) extends the design space, while generating competitive designs in short lead time. The present paper deals with the parametric design and optimisation of containerships. The developed methodology, which is based on the CAESES/Friendship-Framework software system, is demonstrated by the conceptual design and multi-objective optimisation of a midsized, 6,500 TEU containership. The methodology includes a complete parametric model of the ship’s external and internal geometry and the development and coding of all models necessary for the determination of the design constraints and the design efficiency indicators, which are used for the evaluation of parametrically generated designs. Such indicators defining the objective functions of a multi-objective optimisation problem are herein the energy efficiency design index, the required freight rate, the ship’s zero ballast container box capacity and the ratio of the above to below deck number of containers. The set-up multi-objective optimisation problem is solved by use of the genetic algorithms

Advanced damaged stability assessment for surface combatants

One of the major contributors to survivability of a surface combatant is her vulnerability to weapon effects and as such the damage stability characteristics have a direct influence on vulnerability. There are serious concerns about the limitations of the current semi-empirical deterministic criteria in which a combatant’s damage stability is assessed upon. This paper details a comparison between the current approach and a newly presented probabilistic approach with the aim of determining which will result in a more accurate way of estimating the level of survivability of a particular design. A study is also presented in which the damage length used is increased to merchant standards of 0.24Lbp

Damage stability requirements for passenger ships : collision risk based cost benefit assessment

Currently built passenger ships have to comply with SOLAS 2009 probabilistic damage stability requirements. There are, however, serious concerns regarding the sufficiency of these requirements with respect to the Required Subdivision Index R, which should properly account for the risk of People On Board (POB) and ship’s inherent survivability in case of loss of her watertight integrity. In recent years extensive research on determining the appropriate level of R using risk-based methods has been carried out. The urgency of the matter was reinforced by the quite recent Costa Concordia (2012) accident, even though this accident was not related to a collision event. This paper outlines the objectives, the methodology of work and first results of the ongoing studies funded by EMSA (EMSA III project) focusing on risk-based damage stability requirements for passenger ships. In compliance with IMO Formal Safety Assessment process a collision risk model is further developed based on the results of EU GOALDS project and a new required index shall be suggested by means of cost-benefit assessment. The updated collision risk model uses information from the most recent analysis of casualty reports of databases considering the period 1990 to 201