Initial Stage Of Ship Design Research Articles

Enhanced Unified Theory with Forward-Speed Effect Taken into Account in the Inner Free-Surface Condition

The enhanced unified theory (EUT) has been used as a core theory in the integrated system developed at the Research Initiative on Oceangoing Ships (RIOS) of Osaka University for predicting the propulsion and seakeeping performance of a ship in actual seas. In this study, the EUT is modified by adopting partially the solution method in the rational strip theory of Ogilvie and Tuck as a particular solution in the inner problem, thereby a forward-speed effect in the convection term of the free-surface condition is incorporated in the inner solution. This forward-speed effect is analytically shown to contribute only to the cross-coupling radiation forces. Some other forward-speed and 3D effects important in a low-frequency range are also included in the homogeneous component of the inner solution through matching with the outer solution in a similar manner to the unified theory of Newman. Numerical computations are implemented for a slender modified Wigley model and the RIOS bulk carrier model. Good agreement is confirmed in a comparison with experimental data for the cross-coupling added mass and damping coefficients between heave and pitch and also for the resulting ship motions, particularly in heave near the resonant frequency. The added resistance around the motion-resonant wavelength is found to be improved but sensitive to a slight change in heave and pitch motions. Thus, it is stressed that accurate prediction of the ship motions and resultant Kochin function is critical for more accurate prediction of the added resistance in waves. Introduction Although the design of the ship hull form has been based mainly on the propulsion performance in still water, recently, prediction and onboard data analysis for the propulsion and seakeeping performance of a ship in actual irregular waves have been attracting attention of the researchers (Orihara & Tsujimoto 2018; Minoura et al. 2019). In fact, real ships navigate mostly in rough seas, and thus, the so-called short-term and long-term predictions of ship response in actual seas must be made to guarantee the performance and safety of a ship. This trend to study the seakeeping performance of a ship is partly because the Energy Efficiency Design Index regulation was introduced by International Maritime Organization (IMO) to reduce greenhouse gas emission from the ships in operation. Thus, it becomes important to predict with sufficient accuracy the wave-induced ship motions, the added resistance, and the resultant speed loss of a ship in irregular waves represented by a directional wave spectrum (Kashiwagi 2009; Kim et al. 2017) even in the initial stage of ship design, necessitating computations for various profiles of a candidate ship.

A Scenario Simulation - Evaluating Evacuation Analysis for ro-ro Passenger Ship in MV Tai Hwa

The ro-ro passenger ship is a type of passenger ship which is commonly seen in Europe. After the tragedy of MV Estonia, an effective evaluation of escape routes in passenger ship in the initial stage of ship design has been required by International Convention for the Safety of Life at Sea (SOLAS) Convention. To reduce the loss of life in passenger ships at sea, the International Maritime Organization (IMO) has created the revised guidelines on evacuation analyses for new and existing passenger ships. This article followed IMO's mandatory guidelines via using the hydraulic model of emergency egress to scrutinize the evacuation routes, congestion points, and the total evacuation duration of MV Tai Hwa.

Numerical and Experimental Investigation on the Free-surface Flow and Total Resistance of the DTMB Surface Combatant

Starting with the initial design stage, the ship resistance constitutes one of the most important hydrodynamic aspects. In order to generate and optimize the body lines plan, the ship resistance performance must be considered. In this case, both numerical and experimental methods must be applied to obtain the minimum ship resistance controlled by the speed domain. In the last years, numerical studies based on the Computational Fluid Dynamic (CFD) were implemented in the initial ship design stage in order to analyse the free-surface flow and to predict the ship resistance. The numerical optimization process of the hull forms must be validated by means of the experimental model tests in the specific towing tanks. The constant evolution of the numerical and experimental methodologies can be noted. As a consequence, the accuracy level of the ship resistance prediction is increased; though, difficult numerical problems can occur in case of the unconventional hull forms. Taking into account this aspect, a complex numerical and experimental investigation of the ship resistance problem and free-surface topology was performed in the case of the DTMB surface combatant. A parallel numerical simulation was carried out by using the viscous flow solver ISIS–CFD of the software FINETM/Marine provided by NUMECA. The solver is based on the finite volume method to build the spatial discretization of the transport equation to resolve the Reynolds-Averaged Navier Stokes (RANS) equation. Closure to turbulence is achieved by making use of the k-ω SST model, while the free-surface is captured through an air-water interface based on the Volume of Fluid (VOF) method. For the validation purpose, the tank conditions are reintroduced in the numerical model to account for any banking effect, especially for the high speed cases. Experimental model tests were performed in accordance with the ITTC standard procedures, while the extrapolation process to the full-scale was obtained by using an in-house code, based on the ITTC 57 method. The experimental results are compared through with some internationally recognized towing tank experiments that have been performed for a similar ship model, showing a good agreement. Also, the numerical results are validated against the experimental data and showed to be within a satisfactory congruence.

Multi-Objective Optimization of Internal Compartment Layout of Oil Tankers

This work deals with the design of the internal layout of a shuttle tanker formulated as a multi-objective optimization problem, balancing cargo capacity and minimizing still water bending moment with safety requirements, in particular survivability after damage. A parametric model is used to specify the internal layout of a tanker ship considering a fixed hull shape and regulatory framework. The design variables include positions of watertight members in the internal layout, such as watertight bulkhead position, double-bottom height, and wing tanks width. Merit functions are the minimization of oil outflow parameter, maximization of cargo capacity, and minimization of the longitudinal bending moment, which are, respectively, represented for reduction of environmental pollution due to damaged oil tankers, improvement of economic benefits, and safety during operation. The multi-objective genetic algorithm is used for approaching the Pareto frontiers, and the choices between the optimal designs are discussed while introducing a utility function. 1. Introduction The internal layout of the ship's hull is established in the initial stage of ship design. The size and location of the internal spaces are defined taking into consideration the type of ship and the type of content and usage of the compartments. On the other hand, survivability regulations impose limitations in the subdivision arrangement of the ship. Also, the economic competitiveness has special importance in the design of a merchant ship. Cargo capacity and building cost are some of those economic objectives that are not necessarily in accordance with the improvement of safety objectives. Thus, the design of the internal layout of the vessels can be studied as a multi-objective optimization problem targeting safety improvement after damage besides decreasing the cost functions. A diversity of internal layout designs can be investigated within an optimization framework to choose the dominating design among the feasible solutions (Nowacki 2010). However, targeting a variety of objective functions complicates the process of internal compartment design, especially when the main hull dimensions have to be kept constant (Santos & Guedes Soares 2010).

중형급 알루미늄 고속 Rigid Inflatable Boat 선형개발과 저항성능에 관한 연구

In this study, a high speed Rigid Inflatable Boat(RIB) with about 10 meters length is developed. Design speed of the boat is 30 knots (15.43 m/s) using 250 hp twin engines and main material is aluminum. Resistance performance related to the free running attitude as trim and sinkage are discussed and wave patterns are observed to make clear the relationship between the performance and wave characteristics using model test and CFD analysis. The results show that not only wave patterns but also free running attitude of the boat have a strong influence on resistance performance. CFD results including free surface give good relative tendency for effective power and the attitude comparing model test results. CFD analysis used in this study can be used at initial ship design stage of high speed boat.

선박의 성능 요소 추정을 위한 신경망의 실용화 연구

In the initial ship design stage, performance predictions are generally carried out before and after the hull form design. The former is based on the main dimensions and power information, and the latter is based on the geometry of the hull form and propeller. This paper deals with the practical application of neural networks for the predi ction of a ship's performance factors before and after the hull form design. For this, the hull form parameters that affect the performance are studie d, and an optimal neural network structure based on the SSMB database is constructed. By comparing the results predicted by neural networks and the model test results, we confirmed that neural networks can be applied to practically evaluate the performance in the initial ship design stage.

Application of a real-coded genetic algorithm for the fitting of a ship hull surface through a single non-uniform B-spline surface

In digital ship-design processes, surface modeling needs to be as accurate as possible for effectiveness in ship production as well as numerical analysis of the performance. Traditionally, the form of a ship hull is constructed from a set of cross-sectional data. This approach entails difficulties in the cross-sectional spacing and accuracy of the characteristic curves, such as the stern and bow profiles, deck side line, bottom tangential line, and unconnected curves. Genetic algorithms (GAs) have attracted increasing attention as a multimodal optimization solution for surface reconstruction that enable construction of a single non-uniform B-spline (NUB) surface at the initial stage of ship design with constraints such as knuckles, discontinuity conditions, and bulbous bows with high curvatures, . The first, simultaneous multi-fitting GA determines the boundary curves, such as the stem and stern profiles, and finds the common knot values for both curves. Similarly, the same GA technique is applied for other boundary curves at the bottom and the deck. The second GA is employed to fit the interior data points after the boundary curves are fitted. The encoded design variables for surface construction are the locations of the vertices and the knot values. Those variables are modified for improving the surface quality until a predefined degree of precision is attained. In four instances of application, the GA technique developed in this research has been shown to provide good, single, NUB surfaces with high efficiency. In the early design stage, a single NUB surface is more convenient for performance visualization and finite-element methods. It can be readily translated into many CAD/CAM packages, which facilitate the smooth transition of data across the different design stages.

An expert system using rough sets theory for aided conceptual design of ship’s engine room automation

More and more complicated conceptual design of ship’s engine room (CDSER) heavily depends on designers’ engineering knowledge and existing ship data. To achieve intelligent design at the initial ship design stage, many researchers have made much significant progress in this field, however, most of them only focused on how to find the similar constructed ships. At present, how to utilize these existing data remains an untouched topic. In order to make good use of the existing data and reduce the dependence on designers’ experience, a novel system named Expert System for Aided Conceptual Design of Ship’s Engine Room Automation (ESACD), is elaborated in this study. With the support of the constructed Ship Data Warehouse System, two core subsystems Configuration Selection Assistant (CSA) and Design Scheme Decision Assistant (DSDA) are included in ESACD. A promising approach integrating Fuzzy c-means algorithm (FCM) and Rough Sets Theory (RST) to extract configuration rules from the stored data is adopted in CSA. According to engineers’ proposals, RST is utilized to reason knowledge in incomplete scheme information systems for getting design scheme rules in DSDA, which are useful suggestions for engineers to get better schemes at this stage. Finally, the validity and necessity of this interactive expert system are demonstrated through the CDSER of a new 50,000 DWT Handymax bulk carrier. It is proved that ESACD can efficiently facilitate rapid and intelligent design in CDSER, and reduce the cost of a new ship design.

Generation of the 3D CAD model of the hull structure at the initial ship design stage and its application

Currently, all design information of a hull structure is being first defined on 2D drawings not 3D CAD model at the initial ship design stage and then transferred to following design stages through the 2D drawings. This is caused by the past design practice, limitation on time, and lack of shipbuilding CAD systems supporting the initial design stage. As a result, the following design tasks such as the process planning and scheduling are being manually performed using the 2D drawings. For solving this problem, a data structure for shipbuilding CAD systems supporting the initial design stage is proposed and a prototype system is developed based on the data structure. The applicability of the system is demonstrated by applying it to various examples. The results show that the system can be effectively used for generating the 3D CAD model of the hull structure at the initial design stage.

Rapid generation of the piping model having the relationship with a hull structure in shipbuilding

At the initial stage of ship design, a hull structural model, that is, 3D CAD model of a hull structure is not generated by the existing shipbuilding CAD system because it is time-consuming and requires much effort. As a result, a designer is generating a piping model, that is, 3D CAD model of the pipes in the hull structure, independently of the hull structural model at the detailed design stage. The designer must manually modify the piping model whenever the hull structural model changes. To lighten the burden imposed on the designer, a generation method of the piping model based on the hull structural model is developed in this study. The applicability of the developed method is demonstrated by applying it to a deadweight 300,000 ton VLCC (Very Large Crude Oil Carrier). The result shows that the developed method can quickly generate the piping model having the relationship with the hull structure in early time.

Improvement of ship design practice using a 3D CAD model of a hull structure

At the initial stage of ship design, a hull structural model, that is, a 3D CAD model of a hull structure is not generated by the existing shipbuilding CAD system because it is time-consuming and requires much effort. Without the hull structural model, a designer must manually calculate the production material information of a building block by using 2D drawings, parent ship data, and design experiences at the initial planning and scheduling stages. At the initial stage of hull structural analysis, the designer manually generates a structural analysis model, that is, a finite element model of the hull structure. Moreover, the piping model, that is a 3D CAD model of the pipes in the hull structure, is generated independently of the hull structural model at the detailed design stage. To lighten the burden imposed on the designer, we developed an initial hull structural modeling system in our previous study. Using this system, a designer can rapidly and easily generate the hull structural model at the initial stage of design. In this study, the generation methods of the production material information of a building block, the structural analysis model, and the piping model based on the hull structural model are developed. The applicability of the developed methods are demonstrated by applying them to a deadweight 300,000 ton very large crude oil carrier (VLCC). The results show that the developed methods can quickly generate the corresponding information or models at the initial design stage.

초기 설계를 위한 자료 구조 및 모델링 함수 기반의 선체 구조 CAD 시스템 개발

Currently, all design information of a hull structure is being first defined on 2D drawings not 3D CAD model at the initial ship design stage and then transferred to following design stages through the 2D drawings. This is caused by the past design practice, limitation on time, and lack of hull structural CAD systems supporting the initial design stage. As a result, the following design tasks such as the process planning and scheduling are being manually performed using the 2D drawings. For solving this problem, a data structure supporting the initial design stage is proposed and a prototype system is developed based on the data structure. The applicability of the system is demonstrated by applying it to various examples. The results show that the system can be effectively used for generating the 3D CAD model of the hull structure at the initial design stage.

Development of a 3D CAD system for modeling hull structure at the initial ship design stage

At the initial process planning and scheduling stages of shipbuilding, production material information of a building block is manually calculated by using two-dimensional drawings, data of parent ships, and designers' experiences. Thus, the accuracy of the calculated information is low. To provide precise information for the initial process planning and scheduling stages, a three-dimensional computer-aided design model of the hull structure is required at the initial design stage. In this study, a 3D computer-aided design system for modeling hull structure supporting the initial stage of ship design was developed. The applicability of the system was verified through its application to various ships. As a result, it was shown that the developed system can efficiently generate the three-dimensional computer-aided design model and production material information through rapid modeling at the initial design stage.

An initial hull structural modeling system for computer-aided process planning in shipbuilding

At the initial stage of ship design, it is difficult for designers to define all design information of a hull structure on 2D drawings. Thus, other designers must undertake the arduous task of translating such information to generate a 3D CAD model of the hull structure which is required at the following design stage such as the initial process planning stage. Since this task needs much time and effort, the 3D CAD model is not being generated at the initial design stage. For solving this problem, an initial hull structural modeling system is developed in this study. The applicability of the developed system is demonstrated by applying it to a deadweight 300,000 ton VLCC (Very Large Crude oil Carrier). The results show that the developed system can quickly generate the 3D CAD model of the hull structure and accurately extract the production material information for computer-aided process planning at the initial design stage.

선박 초기설계 단계에서의 설계 및 해석 프로세스 통합

Tight integration between design and analysis process and data representation in the ship design application domain has been studied in this paper. Multi-Representation Architecture proposed at Georgia Institute of Technology has been carefully investigated for the application in the initial ship design stage. The prototype implementation shows that the application of MRA in the structural ship design domain is quite possible and can be extended for other design and analysis views in ship design.

Development of a semantic product modeling system for initial hull structure in shipbuilding

In the initial stage of ship design, designers represent geometry, arrangement, and dimension of hull structures, which correspond to product model information, with 2D geometric primitives such as points, lines, arcs, and drawing symbols on 2D drawings. However, designers must translate the product model information defined on the 2D drawings more intelligently in the following design stages. Thus, design semantics could be lost and design processes that follow could be delayed because of errors by mistranslating the information. Here, design semantics mean design intents of the designer, that is, functions and structures which the product must have. In this study, a semantic product model data structure of an initial ship hull structure was proposed, and a semantic product modeling system was developed based on the proposed data structure. The proposed data structure can store semantic product model information such as product design results with the use of 2D wire frame geometrical data, part attributes, and design knowledge. Hence, this information can be used to generate a 3D solid model and production material information for CAPP as needed. The applicability of the proposed data structure and the developed system was verified by applying them to the deadweight 300,000 ton of Very Large Crude oil Carrier’s product modeling procedure. The application results showed that the proposed data structure and the developed system can be efficiently used for overall initial ship design environment.

Agent-based collaborative design system and conflict resolution based on a case-based reasoning approach

Under the concept of a global economy, enterprises are assigning design and production environments around the world in different areas. A serious issue of information exchange emerges as companies use traditional hardware and very distinct software appropriate to their field of expertise. To overcome the problem of low productivity due to the interruption of information, the concept of simultaneous engineering and concurrent design becomes very significant. In this article an agent-based ship design system is developed to support cooperation in distributed ship design environments. Above all, the conflicts that occur while sharing knowledge in the system must be resolved. One approach is to adopt a case-based conflict resolution strategy formulated to resolve current conflict on the basis of similar previously resolved cases in agent-based collaborative design system environments. To do this, conflict cases that occur in the initial ship design stage are extracted. On the basis of the extracted cases, a case base is constructed. In addition, a conflict resolution handler located in the superagent called a facilitator, an agent to control other subagents, is developed to treat conflict problems effectively by case-based reasoning. The case-based conflict resolution strategy is evaluated by applying it to a collaborative design process in the initial ship design stage, especially the machinery outfitting design, the preliminary design, the hullform design, and the structural design. Through the help of the collaboration of the design agents, the facilitator, the conflict resolution handler, and the case-based system, a designer can make decisions based on similar previously resolved cases.

A Study on Optimum Structural Design of Container Ship

There are many unknown variables at the initial stage of ship design. Since the computational time of finite element analysis including modeling is large, it is not appropriate to use finite element method at this stage of ship design. In this paper, structural analysis by transfer matrix method for longitudinal and transverse strength is implemented for container ship design. Genetic algorithm is used for an optimization method, since discrete design variables can be handled easily. The method also has advantage that globally optimized solution can be obtained. The objective function of cost minimization is considered, and its result is compared with real ship.

TECHNOLOGICAL ADVANCES IN AIRCRAFT CARRIER DESIGN

ABSTRACTSince the signing of the Contract Design Plane for the CVN 68 (the U.S. Navy's latest Class of Aircraft Carriers) In 1963, considerable technological advances have been made in Naval Ship Design. This paper provides specific examples of how new technology has affected traditional Carrier design practices and techniques, and also indicates areas where future advanced technology will be needed. It is divided into four sections: 1) Computer Design Application; 2) Total Ship Energy Conservation Analysis; 3) Advances in Structural Design; and 4) Impact of V/STOL Aircraft.The increased use of the computer to define ship characteristics in the initial stage of ship design is discussed, followed by a report on efforts to include energy conservation as an integral part of the design process. The energy conservation approach uses traditional analytical techniques to develop innovative design configurations that will achieve energy savings. Of the many advances in Carrier structural design, two specific examples are given: 1) Elimination of the infamous “knee‐knockers” (high sills in passageway openings) common to Gallery Deck structure, and 2) Successful attempts at reducing the thickness of aircraft elevator platforms. The paper concludes by pointing out some possible challenges facing the ship designer and some of the technology already created by the expected introduction of advanced design Vertical/Short Takeoff and Landing (V/STOL) aircraft.