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Abstract In this paper, we study the relationship between economic performance and flexibility for non-transport vessels. More specifically, we investigate the difference between two means of achieving flexibility: retrofittability and versatility, i.e., the ability of a vessel to satisfy diverse needs with or without change of physical form, respectively. A model is presented to study this relationship, where we first generate design alternatives with relevant, flexible properties before we subsequently evaluate the design alternatives based on their expected discounted economic lifecycle performance. The evaluation model is based on a two-level decomposition of the planning horizon to handle temporal complexity, using scenario planning and Epoch-Era analysis (EEA) for long-term strategic considerations, and Monte Carlo simulation and optimization for medium-term tactical ship deployment. The proposed model is applied to an offshore construction ship design case. Findings indicate that retrofittability can increase economic performance significantly for non-transport vessels operating in an uncertain heterogeneous context. Highlights • This paper studies retrofittability and versatility as two aspects of flexibility in design non-transport vessels. • A vessel can satisfy a diverse set of needs with (retrofittability) or without (versatility) change of physical form. • Epoch-Era Analysis is used at the strategic level and Monte Carlo analysis at the tactical level. • The relationship between investment costs, flexibility, and revenue potential is studied. • Findings indicate that retrofittability significantly can increase economic performance for non-transport vessels. [ABSTRACT FROM AUTHOR]

Charles I's great warship the Sovereign of the Seas is famed for its design, decoration and importance as a tool that heightened the image of English naval supremacy. By exploring its career, size, name and decoration, this article highlights the Sovereign of the Seas’ significance as a national symbol of political and cultural power. It argues that Charles's leading warship was developed as a reaction to naval advances and current affairs in Europe. Through a diverse range of evidence including diplomatic correspondence, printed texts and artwork from both English and French institutions, as well as relating this to similar advances in the Netherlands and Sweden, the Sovereign of the Seas’ development is internationally contextualized. By comparing it with other contemporary warships, most importantly la Couronne of France, it is shown that Charles's flagship was a product of a growing international theatre of maritime activity that was inspired by cultural and political competition, as much as it was by military escalation. [ABSTRACT FROM AUTHOR]

Propellers usually operate in the ship's stern, where the inflow of the non-uniform wake generates oscillating loads and changes the hydrodynamic performance. Therefore, determination of the forces on propellers and hydrodynamic performance due to a non-uniform wake field are the challenging problems for naval architects and hydrodynamists. The main objectives of the present study are to assess the hydrodynamic performance for a single blade and all the blades. The propeller is a B-series propeller under non-uniform wake field behind the Seiun-Maru (hereafter SM) ship hull. A practical approach is employed to calculate the hydrodynamic oscillating loads of the ship propeller under a non-uniform wake field. Results of the computations on the propeller behind the SM ship, due to a non-uniform wake field, are presented and analyzed using classical mathematical methods over a single cycle. The results show that a variation of thrust with the discussed parameters is the same as that shown for torque, also the blade-frequency of the total force, thrust and torque is an increasing function of radial sections, whereas these parameters decrease with increasing radial blade sections. [ABSTRACT FROM AUTHOR]

Techniques for shape representation and further modification of a hull surface definitely play a key role in both the design of new buildings and in the optimisation of the existing ones. The simplification of the methods is the goal to reach in order to create useful tools for real applications. A new approach for hull shape modification is proposed. It is based on a combination of the Subdivision Surface technique for hull surface modelling and Free Form Deformation for shape variation. The formal relation between the two methods is established by the Free Form Deformation control volume and the Subdivision Surface control polygon, introducing significant simplification to the definition of the transformation. The new approach is described in detail highlighting its benefits. Its effectiveness is finally proved by an example of application on a real hull shape, where a combination of a local and global modification has been analysed. [ABSTRACT FROM AUTHOR]

Energy storage has the potential to reduce the fuel consumption of ships by loading the engine(s) more efficiently. The exact effect of on-board energy storage depends on the ship functions, the configuration of the on-board power system and the energy management strategy. Previous research in this area consists of detailed modelling, design, and comparisons of specific on-board power systems for explicitly defined operational profiles. The necessary inputs for these studies are rarely known initially however, since the effect of energy storage on the fuel consumption is not necessarily always positive, it is essential to know the limitations of fuel savings obtained by an on-board energy storage early in the design stage. To that effect, the paper proposes a set of algebraic formulas for the equivalent specific fuel consumption of on-board power systems equipped with electrical energy storage, which give a quick estimation of the maximum fuel savings obtainable. Depending on the specific fuel consumption of the prime mover, the loading point of the system and the use scenario of the battery, relative efficiency improvements can vary between −48% and 57%. A set of design guidelines is also proposed based on the obtained results. [ABSTRACT FROM AUTHOR]

Low temperatures can have a significant impact on the design and construction of marine and offshore structures as the performance and functions can be severely reduced. Compliance with relevant rules and regulations forms a prerequisite along with the specific design considerations to be taken into account. This paper provides an overview of the influence that the specification of the air temperature has on the materials selection used in design codes and standards. The paper focuses on the standards and the definitions used for the ambient air temperature and contributing parameters. To highlight the impact, analysis of air temperature data is presented for low temperature regions of the Russian Arctic, and observations from application to design standards for ships and offshore structures are provided based on this. From the analysis it is clear that the design temperature needs to be carefully selected to ensure the reliability of fracture toughness of structures. [ABSTRACT FROM AUTHOR]

Modular adaptable ships use modules to handle uncertainty in the future operating context. Modules are independent subsystems that increase the flexibility of mission selection with affordable reconfiguration, enabling decision-makers to postpone investments until more information becomes available. Although various studies have investigated modular adaptable ships, the design methods should be developed further to consider the economic value of such operational flexibility in a quantitative manner. We therefore present a hybrid simulation-optimisation method to address this issue. The method determines the optimal design of a modular adaptable ship using both simulation-based optimisation and optimisation-based simulation. We implement the method in a case study where we consider different levels of modularity in designing an offshore support vessel. The case study shows that operational flexibility can mitigate risks in early design decisions that are made under uncertainty. [ABSTRACT FROM AUTHOR]

This paper presents a methodology and analysis tool to explore naval ship system vulnerability using a simplified preliminary arrangement and vulnerability (PA&V) modeling approach in the concept and requirements exploration (C&RE) process at Virginia Tech. This C&RE process uses a multiobjective genetic optimization (MOGO) to explore the design space for nondominated ship design solutions based on design effectiveness, cost, and risk. The previous C&RE process evaluated ship characteristics and only intact system options to determine a design overallmeasure of effectiveness (OMOE) through the calculation of Measures of Performance (MOPs). Vulnerability is very dependent on system design, architecture, and spatial arrangement, and for simplicity these were not developed or calculated. The new C&RE uses a simplified PA&V model so that an Overall Measure of Vulnerability (OMOV) can be calculated for each ship design using the new process and tools described in this paper. The OMOV is calculated by combining Vulnerability measure of performance scores across multiple ship mission options. It is then combined with the intactMOPs to calculate a more complete warfighting OMOE which can be used in the C&RE. [ABSTRACT FROM AUTHOR]

The paper addresses projected changes of wave climate in the North Atlantic and their impact on the safe design of ships, with a particular focus given on associated uncertainties. The Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) uses four scenarios for future greenhouse gas concentrations in the atmosphere called Representative Concentration Pathways (RCP). Two of these scenarios are applied to investigate how sensitive the future North Atlantic wave climate is to the emissions they represent. Winds obtained from six global climate models have been used to simulate waves for a historical period at the end of last century and to project waves for a future period towards the end of this century for these two scenarios. Based on these projections, possible changes in extreme wind and waves are investigated and the associated uncertainties are discussed. The occurrence of rogue-prone sea states which may trigger generation of rogue waves in the past and future climate is also studied. It is shown how the scientific findings on uncertainties related to climate change projections and rogue waves can be incorporated in the risk-based approach used in current design practice of tankers, and ship structures in general. The potential effect of climate change on the safety level of current design practice for tankers is demonstrated. Finally, the paper discusses how structural design of ships can be upgraded to account for climate change and rogue waves without necessarily leading to significant economic consequences. [ABSTRACT FROM AUTHOR]

This paper investigates tradeoffs between technical performance, cost and flexibility level for reconfigurable offshore ships. An offshore ship can be configured with various types of equipment; thus, its base structure constitutes a platform from which several end ship design configurations can be derived. A ship with equipment retrofit flexibility will typically have excess stability, deadweight and deck area to ensure physical compatibility. However, there are complex system interactions that need consideration, such as the effects of flexibility on cost and technical performance. To tackle this problem, we capture technical performance using a multi-attribute utility function, based on a ship's capability, capacity and operability, and utilize a tradespace representation of the system to quantify flexibility using the filtered outdegree metric. Findings indicate that increased platform flexibility does increase capacity, but comes at a complex compromise with operability as resistance is increased, and roll periods become unfavorable due to high accelerations. Furthermore, the analysis confirms the applicability of multi-attribute utility, tradespace exploration and filtered outdegree for understanding the implications of flexible offshore ships. [ABSTRACT FROM AUTHOR]

It is important to predict the actual RPM and engine power of a ship because it helps the ship builder and seafarer understand the actual performance of the ship. However, a precise prediction is difficult because it is closely connected to the ship design, resistance, seakeeping, maneuvering performance, etc., synthetically. In this paper, we propose a new approach to predict the actual RPM and engine power of an LNGC from full-scale measurement data considering the described performance. The sea route, speed over ground and environmental conditions obtained from the measured data are additionally used to simulate sailing of the ship from the coast of southern Taiwan to the coast of Madagascar for 14 days. The results of the simulation are qualitatively reviewed by comparing the calculated time histories of the RPM and the power with the measured RPM and power. The results are quantitatively analyzed by comparing the time histories of errors between the measured values and calculated values. Finally, the power increment due to the environmental load is estimated by comparing the predicted power considering the environmental load with the predicted power, not considering the environmental load. [ABSTRACT FROM AUTHOR]

This investigation presents an approach towards a better understanding of achievable accuracy of fuel consumption predictions of ships and provides an example of how a thorough uncertainty analysis of prediction models can be performed. A generic ship energy systems model is used for the fuel consumption prediction of two reference ships: a RoRo ship and a tanker. The study presents how uncertainties can be categorised and handled in four different phases of a ship's life - from early design to ship operation. Monte Carlo simulations are carried out for two environmental conditions to calculate the mean and uncertainty of the fuel consumption. The results show that the uncertainty in the fuel consumption prediction in a very early phase of the design process is approximately 12%, whereas at a very late phase, it reduces to less than 4%. Finally, the simulation model is applied to a real ship during operation conditions. [ABSTRACT FROM AUTHOR]

In this work, we introduce ShipHullGAN, a generic parametric modeller built using deep convolutional generative adversarial networks (GANs) for the versatile representation and generation of ship hulls. At a high level, the new model intends to address the current conservatism in the parametric ship design paradigm, where parametric modellers can only handle a particular ship type. We trained ShipHullGAN on a large dataset of 52,591 physically validated designs from a wide range of existing ship types, including container ships, tankers, bulk carriers, tugboats, and crew supply vessels. We developed a new shape extraction and representation strategy to convert all training designs into a common geometric representation of the same resolution, as typically GANs can only accept vectors of fixed dimension as input. A space-filling layer is placed right after the generator component to ensure that the trained generator can cover all design classes. During training, designs are provided in the form of a shape-signature tensor (SST) which harnesses the compact geometric representation using geometric moments that further enable the inexpensive incorporation of physics-informed elements in ship design. We have shown through extensive comparative studies and optimisation cases that ShipHullGAN can generate designs with augmented features resulting in versatile design spaces that produce traditional and novel designs with geometrically valid and practically feasible shapes. Video abstract: https://youtu.be/LT9Z52vBgzI [Display omitted] [ABSTRACT FROM AUTHOR]

Service speed of a ship in real weather conditions is a basic design parameter. Forecasting of this speed at preliminary design stage is made difficult by the lack of simple but at the same accurate models of forces acting upon a ship sailing on a preset shipping route. The article presents a model for calculating forces and moment on plane rudder, useful for forecasting of ship service speed at preliminary stages of ship design.

In this paper the scenario based optimization of the bulbous bow of the KRISO Container Ship (KCS) is presented. The optimization of the parametrically modeled vessel is based on a statistically developed operational profile generated from noon-to-noon reports of a comparable 3600 TEU container vessel and specific development functions representing the growth of global economy during the vessels service time. In order to consider uncertainties, statistical fluctuations are added. An analysis of these data lead to a number of most probable upcoming operating conditions (OC) the vessel will stay in the future. According to their respective likeliness an objective function for the evaluation of the optimal design variant of the vessel is derived and implemented within the parametrical optimization workbench FRIENDSHIP Framework. In the following this evaluation is done with respect to vessel's calculated effective power based on the usage of potential flow code. The evaluation shows, that the usage of scenarios within the optimization process has a strong influence on the hull form.

In this paper the scenario based optimization of the bulbous bow of the KRISO Container Ship (KCS) is presented. The optimization of the parametrically modeled vessel is based on a statistically developed operational profile generated from noon-to-noon reports of a comparable 3600 TEU container vessel and specific development functions representing the growth of global economy during the vessels service time. In order to consider uncertainties, statistical fluctuations are added. An analysis of these data lead to a number of most probable upcoming operating conditions (OC) the vessel will stay in the future. According to their respective likeliness an objective function for the evaluation of the optimal design variant of the vessel is derived and implemented within the parametrical optimization workbench FRIENDSHIP Framework. In the following this evaluation is done with respect to vessel’s calculated effective power based on the usage of potential flow code. The evaluation shows, that the usage of scenarios within the optimization process has a strong influence on the hull form.

The paper presents a method of choosing the optimal value of the cargo ships deadweight. The method may be useful at the stage of establishing the main owners requirements concerning the ship design parameters as well as for choosing a proper ship for a given transportation task. The deadweight is determined on the basis of a selected economic measure of the transport effectiveness of ship - the Required Freight Rate (RFR). The mathematical model of the problem is of a deterministic character and the simplifying assumptions are justified for ships operating in the liner trade. The assumptions are so selected that solution of the problem is obtained in analytical closed form. The presented method can be useful for application in the pre-investment ships designing parameters simulation or transportation task studies.

Hull form optimization from a hydrodynamic performance point of view is an important aspect of ship design. This study presents a computational method to estimate the ship seakeeping in regular head wave. In the optimization process the Genetic Algorithm (GA) is linked to the computational method to obtain an optimum hull form by taking into account the displacement as design constraint. New hull forms are obtained from the well-known S60 hull and the classical Wigley hull taken as initial hulls in the optimization process at two Froude numbers (Fn=0.2 and Fn=0.3). The optimization variables are a combination of ship hull offsets and main dimensions. The objective function of the optimization procedure is the peak values for vertical absolute motion at a point 0.15LBP behind the forward perpendicular, in regular head waves.

The ability of predicting material failure is essential for adequate structural dimensioning in every mechanical design. For ships, and particularly for military vessels, the challenge of optimizing the toughness-to-weight ratio at the highest possible value is essential to provide agile structures that can safely withstand external forces. Exploring the case of underwater explosions, the present paper summarizes some of the fundamental mathematical relations for foreseeing the behavior of naval panels to such solicitation. A broad state-of-the-art survey links the mechanical stress-strain response of materials and the influence of local reinforcements in flexural and lateral-torsional buckling to the hydrodynamic relations that govern the propagation of pressure waves prevenient from blasts. Numerical simulation approaches used in computational modeling of underwater explosions are reviewed, focusing on Eulerian and Lagrangian fluid descriptions, Johnson-Cook and Gurson constitutive materials for naval panels, and the solving methods FEM (Finite Element Method), FVM (Finite Volume Method), BEM (Boundary Element Method), and SPH (Smooth Particle Hydrodynamics). The confrontation of experimental tests for evaluating different hull materials and constructions with formulae and virtual reproduction practices allow a wide perception of the subject from different yet interrelated points of view.