bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Model-Scale and Full-scale Deceleration of a Fully Skirted Air Cushion Vehicle in Sideslip
Authors: Cole Robert E. , Boza Joseph J.
Published: January 2021

This article provides experimental results and shows comparisons of 90 sideslip performance of a fully skirted air cushion vehicle using theoretical predictions, 1/12th model scale data, and full-scale data. The goal is to establish a relation among the three data sets and draw conclusions for use in future predictions. First, this article presents results and analysis of tow tank data obtained in late 2008. Then, the Froude scaled data are used to obtain an empirical drag coefficient. A comparison is made between this approach and a theoretical prediction proposed in previous work. An iterative, one dimensional deceleration algorithm is then constructed using the coefficients to predict the deceleration of a full-scale craft having similar skirt characteristics. The predictions are performed for three craft weights and the resulting deceleration rates as a function of Froude number are presented. Data obtained from full-scale testing are then compared with the results of both the model-based algorithm and the theoretical prediction. In general, the model-based simulation overpredicts the deceleration rate for a full-scale craft, whereas the theoretical prediction is more accurate. The model simulation is recomputed using a developed correction factor and is plotted against the theoretical and full-scale deceleration, revealing favorable results. Lastly, a review of the technique is described and recommendations for improvements and following work are provided.
Risk-based Winterization for Vessels Operations in Arctic Environments
Authors: Yang Ming , Khan Faisal I. , Lye Leonard , Sulistiyono Heri , Dolny John , Oldford Dan
Published: January 2021

Because the oil and gas industry has an increasing interest in the hydrocarbon exploration and development in the Arctic regions, it becomes important to design exploration and production facilities that suit the cold and harsh operating conditions. In addition to well-established minimum class requirements for hull strengthening, winterization should be considered as a priority measure early in the design spiral for vessels operating in the Arctic environments. The development of winterization strategies is a challenging task, which requires a robust decision support approach. This article proposes a risk-based approach for the selection of winterization technologies and determination of winterization levels or requirements on a case-by-case basis. Temperature data are collected from climatology stations located in the Arctic regions. Loading scenarios are defined by statistical analysis of the temperature data to obtain probabilistic distributions for the loadings. Risk values are calculated under different loading scenarios. Based on the risk values, appropriate winterization strategies can be determined. A case study is used to demonstrate how the proposed approach can be applied to the identification of heating requirements for gangways.
Dynamic Performance of the National Technical University of Athens Double-chine Series Hull Forms in Random Waves
Authors: Grigoropoulos Gregory J. , Damala Dimitra P.
Published: January 2021

A systematic series of double-chine, wide-transom hull forms with warped planing surface has been developed at the Laboratory for Ship & Marine Hydrodynamics (LSMH) of the National Technical University of Athens during the last two decades. The series are suitable for medium and large ships operating at high but preplaning speeds and consist of five hull forms. Two scaled models for each hull form have been constructed and tested in calm water and in waves. In this article, systematic experimental results in random waves are presented.
Multiobjective Particle Swarm Optimization of a Planing Craft with Uncertainty
Authors: Knight Joshua T. , Zahradka Frank T. , Singer David J. , Collette Matthew D.
Published: January 2021

Uncertainty exists in many of the design variables and system parameters for planing craft. This is especially true in the early stages of design. For this reason, and others, optimization of a craft's performance characteristics is often delayed until later in the design process, after uncertainties have been at least partially resolved. However, delaying optimization can also limit its potential, because freedom to make changes to a design is also highly limited in the later stages. This article demonstrates how uncertainty can be directly incorporated into optimization using particle swarm. A simple synthesis model for a planing craft is built, and a deterministic Pareto front of optimal solutions is found, minimizing two objectives: drag and vertical acceleration at the center of gravity. The craft's weight is then modeled as a normally distributed random variable and sampling methods are used to quantify the uncertainty in the estimated drag for points along the Pareto front. Preliminary results reveal that drag uncertainty is not constant along the Pareto front, presenting useful tradeoff information for designers and decision-makers.
Buckling of Stiffened Panels and Its Mitigation
Authors: Mandal N. R. , Prabu Sree Krishna , Kumar Sharat
Published: January 2021

The increased use of thin plates, like in ships for high-speed operation, results in significantly increased distortion. In-process control of welding distortion is more desirable than post welding rectification from the point of manufacturing efficiency. This can be achieved by suitably designing and also implementing one or more of the distortion control measures as is suitable for a particular manufacturing situation. In this study, an investigation on buckling phenomenon in fabrication of stiffened panels was carried out. Analytical formulae were used to calculate the weld-induced compressive stresses. Critical buckling stresses considering appropriate buckling coefficient for typical stiffened panels as used in shipbuilding practice were calculated. The predictions from these analytical tools were compared with experimental observations. The experimental results compared fairly well with those of the calculated ones. In the present study the panel design aspect as well as thermomechanical tensioning scheme were studied with regard to buckling mitigation. It was observed that when choosing suitable stiffener spacing in conjunction with plate thickness, buckling distortion can be significantly reduced. Distortion mitigation through thermomechanical tensioning was also found to an effective yet simple-to-implement method of buckling distortion control. However, further investigation is necessary toward fully establishing the method of thermomechanical tensioning. Once this method is established, this pre-tensioning technique can be applied as an active in-process control method to avoid buckling distortion in stiffened panels.
The Calculation and Measurement of Welding Residual Stress for Invar Steel of a Liquefied Natural Gas Carrier’s Containment System
Authors: Zhao DongSheng , Liu Yulung , Wang XianDong , Ji ZhouShang
Published: January 2021

The finite element method is applied to calculate the welding residual stress for Invar steel of a liquefied natural gas (LNG) carrier's containment system, whereas the x-ray diffraction method is applied to measure the longitudinal welding residual stress of the welding joint. The calculation and measurement results indicate that the measurement results of longitudinal residual stress are lower than the calculation results, but the distribution of both results is consistent with each other. The measurement results indicate that the longitudinal residual stress near the welding seam increased first and then decreased with the increasing distance to the welding seam, and the tensile residual stress converted to the compressive stress gradually. There exists high longitudinal residual stress in the weld seam and the heat-affected zone of Invar steel, and the maximum residual stress is above 200MPa, which may decrease the fatigue life of Invar steel. Thus, the influence of welding residual stress cannot be neglected when you assess the fatigue life of a LNG carrier's containment system under the sloshing impact.
Modeling and Analysis of Ship Repairing Time
Authors: Kr Dev Arun , Saha Makaraksha
Published: January 2021

Ship repairing (hereinafter referred to as repairing) time, duration of stay of a ship in a shipyard (also a slipway or a floating dock), is a part of the routine maintenance schedule of a ship, mainly required by the classification societies and the flag states. With an interval of approximately 24–30 months, the regulations of both the flag state and the classification society call for a ship to carry out docking survey, intermediate survey, or special survey (once in 5 years), depending on the age of the ship, in a shipyard/floating dock/slipway (hereinafter referred to as a yard). It is mandatory to fulfill the requirements and comply with the rules and regulations for maintaining statutory certification. Owners and yards always try to reduce the repairing time to reduce the loss of income (for an owner) and maximize the annual turnover through handling more ships (for a shipyard). Repairing time and related information for 600 cargo ships were collected from a single shipyard. A multiple linear regression model was developed and analyzed using these basic data. Ship repairing time was then expressed as a function of a ship's age, deadweight, repairing works of mainly hull coating, piping, structural steel, and tank coating. "Method of least squares" was applied to estimate the regression coefficients. In this article, the authors have made an attempt to identify the number of those independent variables that influence repairing time (the dependent variable) and their interrelationship. A mathematical model has been developed and proposed, as a guiding tool, for the decision-maker to estimate a more realistic ship repairing time for the fleet maintenance.
New Estimation Methods for the Steel Weight of European Inland Dry Bulk Ships
Authors: Hekkenberg Robert G. , Hopman Hans
Published: January 2021

There are hardly any methods available for the estimation of the steel weight of inland ships in the earliest design stages. The few weight estimation methods that are available are out of date, limited to a narrow band of main dimensions and not sensitive enough to be used for innovative designs. In this article, which summarizes key results from the PhD thesis of Hekkenberg (2013), new methods are derived for the estimation of the steel weight of inland dry bulk ships. The estimation methods that are presented are derived from large systematic series of computer generated ship designs that comply with Lloyds Register's rules regarding their structure and with the European rules for freeboard. The structure and weight of these designs are validated by a comparison of modeled scantlings with the scantlings of midship sections of existing ships. Further validation is done by a comparison of the modeled overall steel weight with the steel weight of actual ships and the weight estimates of existing methods. The designs are used to derive two types of estimation methods: the first is a set of simple formulas that are valid for inland ships with common sizes and L/B ratios and the second is a more complex set of formulas that allows estimation of the steel weight of inland ships with draughts ranging from 1.5 to 4.5 m, lengths of 40–185 m, beams of 5–25 m, and L/B ratios of 4–20.
Concepts for Ferry Propulsion and Emissions Performance Improvement
Authors: Lamb Thomas
Published: January 2021

As a result of budget pressure, ship owners are seeking ways to reduce fuel cost and meet emission requirements. This is especially true of ferry operators as a result of their continuous operation near land. This article proposes concepts in the areas of hull form, propulsors, and materials for hull and deckhouse structure that could provide the way to achieve improved performance in these areas and provide some additional important benefits.
Seakeeping Analysis of two Medium-speed Twin-hull Models
Authors: Zaraphonities George , Grigoropoulos Gregory J. , Damala Dimitra P. , Mourkoyannis Dimitris
Published: January 2021

The use of twin-hull ships for high-speed passenger and car-passenger transportation is widespread, whereas their potential use for high-speed cargo transportation was estimated as limited. The present article discusses the seakeeping performance of two twin-hull models of an innovative medium-speed container ship design. Their hull form was the result of a thorough hydrodynamic optimization performed at the School of Naval Architecture and Marine Engineering of NTUA aiming to minimize the calm water resistance within the EU-funded project "EU-CargoXpress." The seakeeping analysis was performed by applying numerical tools and also by performing a series of experiments in the towing tank of NTUA and MARINTEK. The obtained results are presented and discussed.
A Decision-based Design Approach for Ships Operating in Open Water and Ice
Authors: Franz von Bock und Polach Rüdiger U. , Ehlers Sören , Ove Erikstad Stein
Published: January 2021

Designing ships for open water and ice requires a suitable design method to account for the distinct challenges in open water and ice. Ships with multi environment capabilities are of high complexity as a result of design-coupling, which is illustrated by design matrices. In this context, this article presents a method that includes a ship performance evaluation method based on the Ship Merit Factor (SMF). The method combines the SMF with a route specific ship-dependent productivity and allows to compare the technoeconomic performance of ships operating in open water and ice. Consequently, the method is applied to a case study comparing the performance of different ship designs operating along the route Rotterdam to Yokohama through the Suez Canal and the Northern Sea Route. The resulting design approach indicates the necessity to include and develop novel simulation-based methods for the reliable assessment of ice-capable ships is discussed.
Numerical Investigation on Interruption in the Welding Process Used in Shipbuilding
Authors: Podder Debabrata , Kenno Sara , Das Sreekanta , Ranjan Mandal Nisith
Published: January 2021

Interruptions in the welding process in shipbuilding are unavoidable because of complex geometry and human fatigue. This article presents an uncoupled three dimensional finite element (FE) modeling technique for bead-on-plate welding and an interruption in the welding process for low carbon and high notch toughness steel plate typically used in shipbuilding. The goal of the FE model was to successfully predict the effect of various time delays in the welding interruption on the residual stress distributions. The FE results are compared with the experimental results for the validation of the model. The experimental work was completed using the neutron diffraction method. The element birth-and-death algorithm was used in ANSYSW to simulate the filler metal deposition. A double ellipsoid heat source was used to simulate the heat source of the weld pool. The FE model considers the temperature dependent nonlinear material properties and uses the temperature-dependent combined coefficient of heat loss. The study found that weld interruptions in the welding process change the residual stress patterns and cause an increase in the maximum longitudinal tensile residual stresses. However, the maximum longitudinal compressive stress reduces as a result of interruptions in the weld process. This study found that a weld interruption duration of approximately 2 minutes is optimum for both fatigue and buckling strength. This study also analyzed the effect of preheat on longitudinal residual stress distribution and concluded that a suitable short time lag without any preheat is equivalent to preheat after a long welding interval.
Reducing Detail Design and Construction Work Content by Cost-Effective Decisions in Early-Stage Naval Ship Design
Authors: Keane Robert G. , Deschamps Laurent , Maguire Steve
Published: January 2021

The Office of the Under Secretary of Defense, Acquisition, Technology, and Logistics (AT&L) recently presented analyses of cost and schedule growth on Major Defense Acquisition Programs (MDAPs) over the last 20 years (2013, 2014). For naval ships, AT&L (2013) concluded that contract work content growth (not capability growth) dominates total cost growth statistically. In addition, costs-over-target are significant and reflect poor cost estimation or faulty framing assumptions. AT&L (2014) also concluded prices on fixed-price contracts are only "fixed" if the contractual work content remains fixed, but this is often not the case. We show that under-sizing the ship during concept design studies increases ship outfit density and adds complexities to the design. These early-stage design decisions on sizing the ship are a major contributor to unnecessary work content growth later in Detail Design and Construction (DD&C) that cannot be eliminated no matter how productive the shipbuilder. However, new ship design methods are being developed and integrated with legacy physicsbased design and analysis tools into a Rapid Ship Design Environment (RSDE) that will enable a more rational process for initially sizing ships. We also identify the need for early-stage design measures of complexity and ship costing tools that are more sensitive to these measures, and propose solutions that will aid decision-makers in reducing DD&C work content by making cost-effective design decisions in early-stage naval ship design.
On the Prospects for International Commercial Shipbuilding Competiveness in Developed Countries
Authors: Koenig Philip C.
Published: January 2021

Since the 1950s, firms in mature manufacturing industries in the developed countries have come under severe pressure from competition based in up-and-coming newly industrialized countries. Particularly in heavy industries, the outlook for the established manufacturers became grim in the 1970s and 1980s. Despite a partial resurgence in some western heavy industries in the 1990s, a new generation of powerful competition emerged in the 2000s and this has placed the future of heavy industrial competitiveness in western and developed Asian countries in question. What is the situation in shipbuilding? Can competitiveness be maintained or resurrected in developed countries? In this article, this question is discussed through two perspectives: that of the industry life cycle and the level of attractiveness of the industry.
Risk-based Winterization on a North Atlantic-based Ferry Design
Authors: Yang Ming , Khan Faisal , Oldford Dan , Lye Leonard , Sulistiyono Heri
Published: January 2021

The Arctic is a recent focal point of the marine and offshore industries. Winterization is required for safe and efficient operations in these harsh cold environments. A riskbased approach to winterization was recently proposed to provide a quantitative way of determining the need for winterization and its appropriate level. To further validate and enhance this approach, it has been applied to a new ice-class passenger ferry design, which will operate in a particular area of the North Atlantic. This location is ideal for the application with low temperatures, strong wind, and high waves. To facilitate this application and eliminate some limitations of the proposed approach, this article proposes a generic framework of risk-based winterization. Results from this article validated the effectiveness and feasibility of using risk-based winterization on vessel designs.
Definition of Ship Outfitting Scheduling as a Resource Availability Cost Problem and Development of a Heuristic Solution Technique
Authors: Rose Christopher , Coenen Jenny , Hopman Hans
Published: January 2021

The outfitting process of shipyards building complex ship types, such as offshore, passenger, and military vessels, is becoming more critical to efficient ship production as the number of components installed on these vessels continues to increase. Outfitting of such vessels is generally characterized by disorganization and rework due to a lack of coordination between the shipyard and subcontractors as well as insufficiently detailed planning. This paper presents a mathematical model for the outfitting planning process of a shipyard building complex vessels. A qualitative description is included for the constraints and objectives underlying the developed mathematical model for the Ship Outfitting Scheduling Problem (SOSP). A heuristic solution technique is also developed for solving the SOSP, and a test case of six midship sections from a recently constructed pipelaying vessel is presented to show the feasibility of both the mathematical model and heuristic. This test case shows that it is possible to find a high-quality planning for the SOSP with a reasonable computational effort. Furthermore, it was found that the greatest priority should be given to components that have the earliest deadlines or dependents with such deadlines. Components should also be scheduled in such a way to minimize the required movements of outfitting personnel between the different work sites of a shipyard.
A Study on Classification Algorithm of Rectangle Curved Hull Plates for Plate Fabrication
Authors: Kim ChanSuk , Shin Jong Gye , Kim Eungkon , Choi YangRyul
Published: January 2021

Since a ship's hull consists of various curved plates, different fabrication methods are applied for efficient fabrication works of curved hull plates. Currently, the classification methods largely rely on division resolution and thus lead to insufficient reliability. This article proposes four standard shapes for fabrication by calculating boundary curvature of each curved plate so that same curvature areas could be acquired. Some examples are carried out for the classification of curved hull plates.
Dry-Dock Inspection Methods for Improved Fouling Control Coating Performance
Authors: Geir Geoffrey , Lund Geir
Published: January 2021

Dry docking is the scheduled time when the fouling control coating is assessed, the hull refurbished, and new coatings applied. The decisions made during this period will affect the performance of the ship for several years. Royal Caribbean Cruises Ltd. has funded research at the Florida Institute of Technology to develop a strategy to improve the selection, application, and management of ship hull coatings. The purpose of the research was threefold: establish an in-house baseline of performance to improve selection, maintenance, and life cycle costs of the different commercially available coatings; improve quality control of dry-dock procedures to include surface preparation and coating application; and insure that the ships are operating in compliance with both local and international regulations. The paper will present the methods that are available to measure specific aspects of the dry-dock process and how this data may be used for quality control and coating selection.
Direct Measure of Rigid Body Accelerations for Wave Impact of a Planing Hull
Authors: Savitsky Daniel
Published: January 2021

Measurements of accelerations during wave impact of a planing hull are usually contaminated by nonhydrodynamic disturbances inherent in full-scale tests and by vibrations induced by the test model and towing carriage in towing tank tests. As a consequence, researchers have resorted to the use of electronic filters to extract rigid body hydrodynamic impact accelerations. This article first calculates the rigid body impact acceleration time histories of 2dimensional deadrise wedges impacting on a level water surface as a function of initial contact velocity, deadrise angle, and unit drop weight. It also calculates the spectral content of these time histories. It then demonstrates how the time histories, time to peak, and spectral content of these 2D wedges are distorted by the use of standard "one-way" electronic filters when processing the data. In a sense, this section of the article can be taken as a simple tutorial on the impact process. The Davidson Laboratory suggests and demonstrates the use of a rigid "free-running" model that is not rigidly connected to the towing carriage and is thus devoid of carriage-induced disturbances. This obviates the use of filters in processing the recorded data. Hence, the directly measured impact accelerations are thus rigid body hydrodynamic accelerations. These are compared with measurements made with the model rigidly attached to the carriage to demonstrate its effect on contaminating the recorded hydrodynamic signal. It is recommended that other towing tanks consider the use of this or other "free-model" test procedures to identify the possible contamination of the recorded acceleration time histories introduced by their carriage and model disturbances. It is also recommended that for those full-scale tests, where the "Standard G" method of data reduction has been applied, that a model be built and tested using the "free-model" test procedure suggested in this article. This will compare the derived rigid body accelerations with the true hydrodynamic impact accelerations as obtained in these free-model tests.
Toward Efficient Merchant Shipbuilding Based on the Lean Production Methodology
Authors: Jiang Ge , Feng Dingzhong , Zhu Weihang
Published: January 2021

In order to effectively meet the new requirements raised by the international shipbuilding convention and specification for shipbuilding enterprises, and to quickly improve enterprise innovation capability, this article analyzes the modern shipbuilding characteristics and compares them with the lean production methodology. In China, the shipbuilding enterprise development is guided by the Shipbuilding Industry Standard Conditions assessment rules from the Ministry of Industrial and Information Technology of China. This article proposes establishing an efficient merchant shipbuilding system based on the lean production methodology and the construction technology capability indices in the Shipbuilding Industry Standard Conditions. This article focuses more on the hull construction and merchant ship production processes, instead of the entire engineering, procurement, and construction shipbuilding management. It elaborates key system technologies including value stream analysis, efficient shipbuilding production design, efficient shipbuilding project management, efficient shipbuilding precision management, and efficient full factory management. The efficient shipbuilding system has been implemented in a Chinese merchant shipbuilding enterprise to significantly improve productivity and reduce shipbuilding cycle time.
Modeling and Analysis of Ship Repairing Labor
Authors: Kr Dev Arun , Saha Makaraksha
Published: January 2021

Labor cost is an important and sensitive issue in labor intensive industry. Ship repairing work is, by nature, labor intensive and not prone to automation. In normal ship repairing or routine maintenance of a ship, labor cost contributes the highest amount in the final invoice. This figure may go up to 70% of the total cost. This cost is directly contributed by labor (man-days) utilized for the ship repairing works. Owners and shipyards are always very keen for lowering the man-days value. Lesser man-days can directly be translated into the lower final invoice (for the owner) and higher productivity (for a shipyard), which can help the shipyard to stay in a competitive market. Ship repairing labor (man-days) and related information for 50 cargo ships of various ages, sizes and types were collected from a single shipyard. A multiple linear regression model was developed and analyzed using these primary data. Ship repairing labor was then expressed as a function of a ship's age, deadweight, type, and repairing works consisting of mainly hull blasting, hull painting, structural steel, and piping. The "method of least squares" was applied to estimate the regression coefficients. In this article, the authors have made an attempt to identify those independent variables that influence ship repairing man-days (the dependent variable) and their interrelationship. A mathematical model has thus been developed and proposed, as a guiding tool, for the decision maker to estimate a more realistic ship repairing labor (man-days) for ships to be under repair.
Numerical Investigation on the Effect of Thermo-mechanical Tensioning on the Residual Stresses in Thin Stiffened Panels
Authors: Podder Debabrata , Gadagi Amith , Ranjan Mandal Nisith , Kumar Sharat , Singh Lavepreet , Das Sreekanta
Published: January 2021

In shipbuilding industry, thin plates are widely used to maintain the minimum hull weight and to increase the fuel efficiency. These thin plates, when welded, are more prone to buckling distortions. So, it is very much important to predict these buckling distortions beforehand and try to mitigate them in the fabrication stage rather than doing it later. By doing this, the competitiveness in cost and time can be increased. In this study, a numerical investigation on the reduction of buckling distortions in the fabrication of orthogonal stiffened panels as used in shipbuilding was conducted. A method of in-process distortion mitigation technique, named as thermo-mechanical tensioning (TMT) was introduced to reduce the compressive residual stress in the far-field zone. The detail stress development mechanism in TMT process is discussed here. Commercially available finite element software ANSYS® 15 was used for calculations. The simulations revealed that the peak tensile stresses in the weld zone and the corresponding far-field compressive residual stresses get significantly reduced by the implementation of TMT. Thus, with reduction of compressive residual stress, buckling of such stiffened panels is effectively mitigated.
Numerical and Experimental Study on Cutting Access Opening in Ship Structure
Authors: Zhou Bo , Han Xiaoshuang , Guo Wei , Liu Yujun , Tan Soon-Keat
Published: January 2021

Creating an access opening in ship structure through thermal cutting is an important process in ship repair and reconstruction. The flame cutting process typically leads to a nonuniform temperature distribution, generates residual thermal stress and localized plastic deformation. As openings are needed at various locations of ship hulls, it is also necessary to consider the effects of structural constraints in the immediate end of the plate where the plate is either welded or fixed to the ship frame or bulkhead. These are challenging tasks. This article presents a study based on the thermal elastoplastic analysis. By using the finite element techniques, a steel plate model undergoing flame cutting process to create an opening was studied in details. The numerical model was validated with experimental data. The study identified several key parameters that are 1) structural boundary condition, 2) steel plate size, 3) opening location, and 4) opening shape.
On the Rotor Lifting Line Wake Model
Authors: Epps Brenden
Published: January 2021

This article comments on the wake model used in moderately loaded rotor lifting line theory for the preliminary design of propellers and horizontal-axis turbines. Mathematical analysis of the classic wake model reveals an inconsistency between the induced velocities numerically computed by the model versus those theoretically predicted by the model. An improved wake model is presented, which better agrees with theory than previous models and thus improves the numerical consistency and robustness of rotor lifting line design algorithms. The present wake model analytically relates the pitch of the trailing vortices to the pitch of the total inflow computed at the lifting line control points. For conciseness, the article focuses on the propeller case, although both propeller and horizontal-axis turbine examples are presented.
Ship Pipe Routing Method Based on Genetic Algorithm and Cooperative Coevolution
Authors: Dong Zongran , Lin Yan
Published: January 2021

Pipe routing is one of the most time-consuming and complicated jobs in shipbuilding design. This article presents the automatic ship pipe routing method. To improve the efficiency of single pipe routing, the fixed-length encoding genetic algorithm (GA) is first used by connecting adjacent intermediate points with generated pipe segments according to the specific routing patterns. The crossover and mutation operations are designed on the basis of this encoding as well. In case of the routing for multi pipes or pipe with branches, cooperative coevolutionary GA is adopted to route pipes harmoniously and to reduce the risk of combinatorial explosion caused by the number of pipes. During algorithm implementation and the building of cell decomposition model, the practical constraints in ship piping have been taken into account. In the end, the efficiency and feasibility of the proposed approach are illustrated by solving problems in designed test case and real ship applications.
Productivity Improvement Strategies Using Simulation in Offshore Plant Construction
Authors: Gi Back Myung , Woo Jong Hun , Lee Philippe , Gye Shin Jong
Published: January 2021

Since the global financial crisis of 2008, the global shipbuilding industry has changed considerably and placed major Korean shipbuilding companies (mostly common carrier builders) in a precarious position. Current competitiveness in the global shipbuilding industry has been attracted by low labor costs in China. The Korean shipbuilding industry, with heavy industry as the central figure, is attempting to increase its share of offshore plant construction to develop deep-sea resources. This highlights the most outdated part of offshore plant in Korea, the development technology, which includes front-end engineering development and deep-water floaters, unlike in more advanced companies in the United States, where development technology has advanced rapidly. This has prompted the Korean government to invest most of its R&D funds in the areas of product and equipment development. However, mega shipbuilders such as Samsung, Hyundai, and Daewoo have incurred considerable losses at construction stages because of major delays in production. By contrast, international engineering companies have supported development engineering. The considerable financial losses incurred by mega shipbuilders are believed to be caused by a lack of quality management with respect to the massive production quantities and complexities involved in outfitting topside structures. This study investigates a strategy to advance production management specialized for the offshore plant business and describes a robust and sustainable technical roadmap based on current information technologies (IT) and simulation-based management methods
Assessment of Survivability of Surface Combatants after Damage in the Sea Environment
Authors: Boulougouris Evangelos , Winnie Stuart , Papanikolaou Apostolos
Published: January 2021

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 article 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 of 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 because of the way modern combatants are designed.
A Study into the Validity of the Ship Design Spiral in Early Stage Ship Design
Authors: Pawling Rachel , Percival Victoria , Andrews David
Published: January 2021

For many years, the design spiral has been seen to be a convenient model of an acknowledged complex process. It has virtues particularly in recognizing the ship design interactive and, hopefully, converging nature of the process. However, many find it unsatisfactory. One early criticism focused on its apparent assumption of a relatively smooth process to a balanced solution implied by most ship concept algorithms. The paper draws on a postgraduate design investigation using the University College London Design Building Block approach, which looked specifically at a nascent naval combatant design and the issues of size associated with "passing decks" and margins. Results from the study are seen to suggest that there are distinct regions of cliffs and plateau in plots of capability against design output, namely ship size and cost. These findings are discussed with regard to the insight they provide into the nature of such ship designs and different ways of representing the ship design process. The paper concludes that the ship design spiral is a misleading and unreliable representation of complex ship design at both the strategic and detailed iterative levels.
A Framework for Integrating Human Factors in the Early Stages of Ship Design: Application to the Mess Halls of a Surface Combatant
Authors: González-Cela Gerardo , Bellas Roberto , Carreño Rafael , Martínez Javier , Touza Ramón , González-Gil Arturo , Gómez Miguel , González Diego
Published: January 2021

The new F-110 frigates project is currently in the conceptual design and definition phase. General arrangement has to be defined; there are many demands and proposals of changes. One of them is the design of the most crowded areas, the mess halls. The aim of this article is to provide the Spanish Navy Staff with a decision tool that helps in determining the optimal distribution of the future F-110 mess halls. For this purpose, a new "analytical decision maker" model was designed providing advanced statistical methods and computer pedestrian simulations within multicriteria decision-making framework that allows optimizing conceptual designs. To reduce subjectivity, crew movement simulations and statistical methods were added to the multicriteria decision model, thus creating a less-subjective decision tool. A sensitivity analysis was conducted to check the robustness of results. An integrative decision and design approach are necessary for broad acceptance of human factors adoption within naval architecture design.

1. Introduction

1.1. Ship design and human factors

Ship design is a complex challenging process that requires the successful coordination of many different disciplines and that necessarily involves trade-offs between competing interests to achieve a balanced result. Hence, ship designers need to understand the complex interaction between different design drivers and their influence on the final solution, always being aware that the cost of rework may become drastically high if errors are found in the later stages of the design.
Preliminary Stability and Resistance Analysis of the Cheops Boat
Authors: Morabito Michael G. , Brier Bob , Greene Stuart
Published: January 2021

The Cheops Boat is the most complete, largest, and one of the oldest boats ever excavated, but it has received surprisingly little study by Naval Architects. The 43-m boat was constructed around 2500 BC and placed, disassembled, in a pit next to the Great Pyramid at Giza in Egypt. Since its discovery in 1954, there has been speculation about its original design, means of propulsion, and purpose. This article presents previously unpublished results of the first tank testing of a model of the Cheops Boat and some preliminary conclusions about the design, propulsion, and function of the original. It is shown that the stability characteristics of the boat make it suited for carrying lightweight cargo and people in the protected waters of the Nile. Towing tests have shown that the boat can be safely rowed in a variety of wind and current conditions. Windward sailing calculations have shown that, if fitted with sail, then boats such as the Cheops Boat perform well downwind, but sail no closer than a beam reach.

During the 1954 clearing of debris from the Giza Plateau, it was noticed that the Great Pyramid's north and west enclosure walls were 23.6m from the base of pyramid, but the south wall was 5mcloser to the base. Careful inspection revealed that the south wall had been built in an asymmetrical location to conceal two boat pits beneath it. The two pits were end to end, one covered by 41 massive limestone blocks and the other by 40. When the eastern pit was opened, the remains of the disassembled boat were revealed. Figure 1 shows photographs of some of the pieces as they were removed from the pit. Remarkably, the 4500-year-old cedar had been so well preserved that it was possible to reassemble this boat like a kit. Even the rope was preserved, and looked like what could be bought today.
Comparison between the Dynamic Behavior of the Non-stepped and Double-stepped Planing Hulls in Rough Water: A Numerical Study
Authors: Esfandiari Arman , Tavakoli Sasan , Dashtimanesh Abbas
Published: January 2021

Reducing vertical motions of high-speed planing hulls in rough water is one of the most important factors that help a boat to become more operable, and will benefit the structure of the boat and the crew on board. In the recent decade, stepped planing hulls have been investigated with emphasis on their better performance in calm water than that of nonstepped planing hulls. However, there are still doubts about their performance in rough water. In this study, we investigate this problem by providing numerical simulations for motions of a double-stepped and a non-stepped planing hull in a vertical plane when they encounter head waves. The problem will be solved using the finite volume method and volume of fluid method. To this end, a numerical computational fluid dynamics code (STARCCM1) has been used. Accuracy of the numerical simulations is evaluated by comparing their outcome with available experimental data. The dynamic response of the investigated hulls has been numerically modeled for two different wave lengths, one of which is smaller than the boat length and the other which is larger than the boat length. Using the numerical simulations, heave and pitch motions as well as vertical acceleration are found. It has been found that at wave lengths larger than the boat length, heave amplitude decreases by 10–40%when two steps are added to the bottom of a vessel. It has also been observed that pitch of a planing hull is reduced by 18–32% in the presence of the two steps on its bottom. Finally, it has been observed that for wave lengths larger than the boat length, the maximum vertical acceleration decreases by a gravitational acceleration of about .2–.7.
Effect of Manual and Automatic Activated Tungsten Inert Gas Welding Using Single Component Fluxes on Stainless Steel AISI-304
Authors: Prasad Shaji Krishna , Mathiazhagan Andy , Krishnadas Pallichakkalayil Sasidharan
Published: January 2021

The study compared the effects of manual activated tungsten inert gas (A-TIG) welding and automated A-TIG welding on AISI (American Iron and Steel Institute)- 304 at three different values of current using commercially available powders of Al2O3, SiO2, Fe2O3, MgCl2, and TiO2 separately as activated flux and distilled water as carrier solvent. The effect of fluxes on the depth of penetration of the weldments, width of weldment, microstructure of the weldment, and microhardness of the weldment was investigated. Reverse Marangoni convection and arc constriction are found to be more effective in A-TIG manual welding, as aspect ratio obtained by A-TIG manual welding is greater as than that of automatic A-TIG welding. Microstructure of both the manual and automatic A-TIG-welded specimen is similar with no noticeable differences and almost same amount of intermetallic phases and carbon precipitates. Microhardness tests revealed that for Al2O3 and TiO2 fluxes, manual A-TIG-welded specimen have lower values of microhardness at weldment, heat-affected zone, and base metal than automated A-TIG-welded specimen. The aim of the study is to implement the manual A-TIG process in shipbuilding industry to improve the productivity of welding as automated A-TIG welding in the industry has limitations.
A Point Set Analysis Method for Hull Blocks Based on CPD and Engineering Constraints
Authors: Guan Guan , Liao Hongling
Published: January 2021

A point set analysis method considering the practical engineering constraints has been proposed in this article. First, the coherent point drift method was used to obtain the initial values of data analysis. Second, the error distribution in different directions was expressed by weight vectors. Last, the multiobjective optimization model was built and the engineering constrains were introduced into the multioptimization objective function to achieve the optimal data analysis results. The experimental results proved that the method could obtain the reasonable data analysis results, which met the engineering constraints. It provides the important basis for the subsequent assembly.
Nesting Problem of Irregular Shape Based on Motion Simulation
Authors: Li Peiyong , Gao Xiang , Wu Xiaodong , Zhang HuaWei , Wang Chong
Published: January 2021

This article discusses cutting and packing problems found in the shipbuilding industry, with the aim of minimizing material wastage. The irregular nesting problem is a variation of such problems in which the container has variable length and fixed width. Nesting of irregular shapes is a combinatorial problem with nondeterministic polynomial complete difficulty. Generally, work on solving such problems is mainly conducted in the fields of geometry and operations research. This study proposes a new method for solving the nesting problem; i.e., shape nesting can be simulated by the motion of discrete bodies in a container with a fixed width. Calculation with the program developed by the authors has been performed, and the results show that the algorithm was able to achieve good compaction for the datasets, and the running time and utility of sheet are satisfied. Results of this study show that the new method based on motion simulation can be a new solution to the shape nesting problem.
Design of the Remote Monitoring System for CNC Ship Cold Frame Bender
Authors: Li Peiyong , Huang Qiming , Shu Kun , Zhou Yongqing , Wang Chong
Published: January 2021

The aim of this study was to overcome the problems and difficulties in the process of using CNC ship cold frame bender, especially for the routine maintenance and troubleshooting of CNC ship cold frame bender. The remote monitoring system is established according to the work principle of CNC ship cold frame bender. The system is composed of Client/Server and Browser/Server mixed structure, which includes data acquisition module, data transmission module, data network sharing module, remote online fault detection module, etc. The test results show that the system can collect and analyze the operation condition of the equipment remotely, and then analyze the data to realize the remote online detection. Furthermore, experts can evaluate the performance data and the test results remotely and give feedback to the site by the data network distribution platform. The test results also demonstrate the promising application of the proposed remote monitoring system to effectively improve the efficiency of the CNC ship cold frame bender.