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Generalized finite difference method for three-dimensional eigenproblems of Helmholtz equation

MATHEMATICS AND COMPUTERS IN SIMULATION 2020年第0期196卷 45-67页

作者： Zhang, Juan Shuy, Rong-Juin Chu, Chiung-Lin Fan, Chia-Ming Natl Taiwan Ocean Univ Doctoral Degree Program Ocean Engn & Technol Keelung 20224 Taiwan Jiangsu Ocean Univ Sch Ocean Engn Lianyungang 222005 Peoples R China Natl Taiwan Ocean Univ Dept Syst Engn & Naval Architecture Keelung 20224 Taiwan Natl Taiwan Ocean Univ Dept Harbor & River Engn Keelung 20224 Taiwan

In this paper, a meshless numerical procedure, based on the generalized finite difference method (GFDM) is proposed to efficiently and accurately solve the three-dimensional eigenproblems of the Helmholtz equation. The eigenvalues and eigenvectors are very important to various engineering applications in three-dimensional acoustics, optics and electromagnetics, so it is essential to develop an efficient numerical model to analyze the three-dimensional eigenproblems in irregular domains. In the GFDM, the Taylor series and the moving-least squares method are used to derive the expressions at every node. By enforcing the satisfactions of governing equation at interior nodes and boundary conditions at boundary nodes, the resultant system of linear algebraic equations can be expressed as the eigenproblems of matrix and then the eigenvalues and eigenvectors can be efficiently acquired. In this paper, four numerical examples are provided to validate the accuracy and simplicity of the proposed numerical scheme. Furthermore, the numerical results are compared with analytical solutions and other numerical results to verify the merits of the proposed method.(c) 2022 International Association for Mathematics and Computers in Simulation (IMACS). Published by Elsevier B.V. All rights reserved.

关键词： Helmholtz equation Eigenvalue Eigenvector Generalized finite difference method Meshless method

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Three-dimensional numerical analysis of a vertical axis autorotation current turbine (VAACT): Effects of lateral blockage and free surface

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APPLIED OCEAN RESEARCH 2024年 150卷

作者： Wu, Hao Yang, Shuojia Wang, Enhao Cao, Renjing Fernandes, Antonio Carlos Yin, Xianghan Xiao, Qing Tsinghua Univ Inst Ocean Engn Shenzhen Int Grad Sch Shenzhen 518055 Guangdong Peoples R China Southern Univ Sci & Technol Dept Mech & Aerosp Engn Shenzhen 518055 Guangdong Peoples R China Southern Univ Sci & Technol Guangdong Prov Key Lab Turbulence Res & Applicat Shenzhen 518055 Guangdong Peoples R China Fed Univ Rio Janeiro Program Ocean Engn COPPE BR-21945970 Rio De Janeiro Brazil Univ Strathclyde Dept Naval Architecture Ocean & Marine Engn Glasgow G4 0LZ Scotland

In this study, we conduct an in-depth three-dimensional (3D) numerical analysis of an innovative vertical axis autorotation current turbine (VAACT), focusing on examining the effects of lateral blockage and free surface on its performance. This analysis employs detached eddy simulation (DES) integrated with the sliding mesh and the volume of fluid algorithm. To begin with, the time series data of angular velocities acquired during the power output phase indicates that, within the range of 0.05 to 0.213, an increased blockage ratio positively influences the turbine's rotational stability and improve its efficiency. Further, the extrapolation from the fitted curve of the mean power coefficient (CP) P ) as a function of lateral blockage ratio suggests that, in the absence of lateral blockage, the CP P value would approximate 0.145. Additionally, it is observed that the free surface generally diminishes the turbine's rotational speed and power. This effect is particularly pronounced when the free surface fluctuation is large relative to the turbine's submerged height. Notably, two parallel rows of 3D vortices on the free surface periodically detach in the wake, and the vortices downstream of the retreating edge appear stronger. This study also presents and analyses detailed flow field characteristics, including 3D vortical structures, free surface fluctuations, and vorticity contours. Overall, this research enhances the comprehension of this innovative vertical-axis turbine, offering valuable knowledge for its potential practical deployment.

关键词： Detached eddy simulation Vertical-axis hydrokinetic turbine Slide mesh Lateral blockage effect Free surface effect

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A critical review on structural testing and assessment of lightweight sandwich structure for ship structure application

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AIP Conference Proceedings 2023年第1期2674卷

作者： Tuswan Tuswan Abdi Ismail Achmad Zubaydi Bambang Piscesa Nadya Paramita Langening Sukma Sukma Department of Naval Architecture Institut Teknologi Sepuluh Nopember Indonesia Departement of Naval Architecture Universitas Diponegoro Semarang Indonesia Ship Machinery Study Program Faculty of Vocational Studies Indonesia Defense University Belu Indonesia Department of Civil Engineering Institut Teknologi Sepuluh Nopember 60111 Surabaya Indonesia

Many experts have lately joined the effort to study lightweight materials as an alternative solution in ship construction. However, there are limited references regarding the discussion of the current development of the lightweight material application, specifically in ship structure. The purpose of this article is to offer an overview of the present state of the art and give critical points concerning the design and requirements of sandwich applications in ship constructions. The discussion covers several topics, including the current rules/ standard of developing material issued by classification bodies, various sandwich types with different application areas, and an overview of the structural strength assessment of hybrid sandwich application on various ship structure locations. Some potential scenarios for sandwich constructions in maritime applications are also proposed.

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Integrated ship recycling industrial estate design concept for Indonesia

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IOP Conference Series: Earth and Environmental Science 2022年第1期972卷

作者： Sunaryo Bagus A Tjitrosoemarto Naval Architecture and Marine Engineering Study Program Universitas Indonesia Kampus UI Depok 16424 Indonesia.

Since the implementation of the cabotage principle, the number of Indonesian flagged ships has been increasing significantly, due to the government's incentive on importation tax for used ships. The fleet is dominated by old ships, which most of them will soon be sent for recycling. The ship recycling industry has a great opportunity for the economy of Indonesia, because of its contribution to the steel industry and job creation, but on the other hand it is also a very environmentally unfriendly industry. Currently there is no ship recycling yard complies with the requirements of international and national regulations, most of them are still implementing conventional method, and are not connected to the supporting industries. Based on these issues the study was aimed to design a concept of an integrated green and sustainable ship recycling industry estate, which has all necessary industries and facilities in it, and efficiently connected with each other. Block Plan program was used to optimize the arrangement. It is proposed that five ship recycling yards, large; medium; and smaller capacity, steel mill, waste treatment facility, electricity power plant, fresh water facility, training centre, workers accommodation, hospital, and bus terminal should be included in the estate.

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Prediction of submarine pipeline equilibrium scour depth based on machine learning applications considering the flow incident angle

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APPLIED OCEAN RESEARCH 2021年 112卷 1页

作者： Hu, Ke Bai, Xinglan Zhang, Zhaode Vaz, Murilo A. Zhejiang Ocean Univ Sch Naval Architecture & Maritime Zhoushan 316022 Peoples R China Key Lab Offshore Engn Technol Zhejiang Prov Zhoushan 316022 Peoples R China Univ Fed Rio de Janeiro Ocean Engn Program Rio De Janeiro Brazil

Scouring below submarine pipelines, due to fluid, structure and soil material interaction, is a complex phenomenon involving numerous effective parameters. In this research, machine learning methods, such as the GABP (Genetic Algorithm based Back Propagation) neural network, RBF (Radial Basis Function) and SVM (Support Vector Machine) are presented and prediction models are built for forecasting pipeline equilibrium scour depth. The results of the prediction models are compared with observed data, which shows that the GA-BP model provides the best predictive performance for scour depth exhibiting highest correlation coefficient and lowest Root Mean Square Error as compared with RBF, SVM in live-bed conditions. Results of the sensitivity analysis indicate that Froude number (Fr) is the most effective parameter for predicting the scouring depth below the pipeline. With the increase of flow incident angle, its influence on the predicted scour depth results becomes more obvious.

关键词： Submarine pipeline Scouring depth Machine learning method Flow incident angle

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FIRE PHENOMENON OF NATURAL GAS LEAK ACCIDENTS ON THE LNG-FUELED SHIP USING COMPUTATIONAL FLUID DYNAMIC 39

FIRE PHENOMENON OF NATURAL GAS LEAK ACCIDENTS ON THE LNG-FUE...

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ASME 39th International Conference on Ocean, Offshore and Arctic Engineering (OMAE)

作者： Nubli, Haris Prabowo, Aditya Rio Sohn, Jung Min Pukyong Natl Univ PKNU Interdisciplinary Program Marine Convergence Desi Busan South Korea Univ Sebelas Maret UNS Dept Mech Engn Surakarta Indonesia Pukyong Natl Univ PKNU Dept Naval Architecture & Marine Syst Engn Busan South Korea

ISBN: (纸本)9780791884324

The emission of greenhouse gases has tightened up in the shipping industries, since the International Maritime Organization established the Emission Control Area (ECA), to reduce the emission of NOx and SOx. It results in an increase of Liquefied Natural Gas (LNG) as an alternative fuel for merchant vessels. However, the LNG-fueled ship should be verified with respect to reliability and its safety due to the high risk of natural gas. This work aims to establish the scenario of gas leak accident, and the critical zone due to fire spreading. The variables of leak size, leak location, wind direction and wind speed were included into the scenario. The probabilistic approach also applied to determine the scenario. This study provides the release duration which is associated to the ignition probability. The Latin Hypercube Sampling was used to generate the credible scenario. Finally, Computational Fluid Dynamics (CFD) analysis of fire release scenarios was performed by using a commercial package software, Kameleon FireEx. The numerical simulation results show the thermal radiations which consisted of several levels of heat intensity. The size of critical zone can be determined from the contour of thermal radiation.

关键词： LNG-fueled ship gas dispersion fire phenomenon computational fluid dynamics critical zone

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An Approach using Multicriteria Decision Methods to Barges Conguration for Pushed Convoys in the Amazon

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INTERNATIONAL JOURNAL OF INFORMATION TECHNOLOGY & DECISION MAKING 2020年第1期19卷 317-341页

作者： Dias Lameira, Pedro Igor Garcia Miranda Filgueiras, Taina Carvalho Botter, Rui Carlos Saavedra, Rodrigo dos Santos Fed Univ Para Fac Marine Engn & Naval Architecture Augusto Correa St 01 BR-66640590 Belem Para Brazil Univ Sao Paulo Postgrad Program Marine Engn & Naval Architecture Prof Mello Moraes Ave 2231 BR-05508900 Sao Paulo SP Brazil

The Amazon region has the largest hydrographic basin in the world and a favorable geographical location as a strategic export point but does not satisfactorily exploit its potential for transport and cargo flow , mainly as a diffierential factor of logistic competitiveness. For the waterway mode, cargo transportation is predominantly carried out by pushed convoys. The objective of this research is to evaluate and select, the best river train for the outflow of iron ore on the Maraba - Vila do Conde stretch, through a multiple criteria decision-making approach. To meet the objectives, a methodological framework is proposed using a hybrid AHP-DEMATEL method, based on a statistical analysis and to guarantee the reliability of the results for the proposed alternatives and not only considering the preference function, the ELECTRE method was used and also a parametric comparison of the AHP results. The main goals of this work were achieved and it was possible to infer that the combination of these methods has, in addition to the evident efficacy, a high reliability in the water transport area, being able to be used with accuracy of diverse forms in the academic area, as well as in industrial applications. Therefore, it can be affirmed that the best-pushed convoy configuration for the iron ore runoff in the Maraba - Vila do Conde stretch is composed by six barges in the arrangement of two columns and three rows with the measurements, by barge, with length of 60.96 m;beam of 13.75 m;and a 5m molded depth.

关键词： Pushed convoys design Amazon logistics multiple criteria decision making AHP-DEMATEL ELECTRE IV

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Hydrodynamic characteristics of a full-scale kelp model for aquaculture applications

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AQUACULTURAL ENGINEERING 2020年 90卷 102086-102086页

作者： Fredriksson, David W. Dewhurst, Tobias Drach, Andrew Beaver, William St Gelais, Adam T. Johndrow, Kathryn Costa-Pierce, Barry A. US Naval Acad Dept Naval Architecture & Ocean Engn 590 Holloway Rd11D Annapolis MD 21402 USA Kelson Marine Co Scarborough ME 04074 USA Univ Texas Austin Austin TX 78712 USA US Naval Acad Hydromech Lab 590 Holloway Rd11D Annapolis MD 21402 USA Univ New England Sch Marine & Environm Programs Grad Program Ocean Food Syst 11 Hills Beach Rd Biddeford ME 04005 USA Univ New England Sch Marine & Environm Programs 11 Hills Beach Rd Biddeford ME 04005 USA

Hydrodynamic characteristics are needed to optimize the design of kelp aquaculture systems. To support this need, the objective of this study was to resolve both the normal and tangential drag forces acting on a dense aggregate of kelp blades using full-scale physical model tests. The physical model was designed to match the exposed length, individual blade flexural rigidity, the number of blades per unit width, the mass/length of biomass, and the aggregate mass density of kelp cultured at the University of New England experimental aquaculture lease site in Saco Bay, Maine USA. Tow tests were conducted at the United States naval Academy in a tank with the dimensions of 116m x 7.9m x 4.9 m. The large tank size enabled the use of the full-scale physical model, minimizing dynamic similarity issues. In a series of tests, the model was towed in orientations both aligned and perpendicular to the tow direction. Horizontal and vertical reaction forces were measured for five tow speeds, along with the deflection of the dense kelp aggregate. With these datasets and the wet weight biomass per length of the model, normal and tangential drag forces were calculated. Drag components were processed into corresponding normal and tangential drag-area values. The drag-area representation was chosen since reference areas were ambiguous for both the actual kelp and model. At the higher speeds, the total horizontal drag in the aligned configuration were slightly lower than for the perpendicular orientation. Normal drag-areas as a function of tow speed ranged from 2.36 m(2)/m to 1.39 m(2)/m for the aligned case and from 2.49 to 1.88 m(2)/m for the perpendicular case. Tangential drag-areas as a function of tow speed ranged from 0.264 m(2)/m to 0.0325 m(2)/m for the aligned case and from 0.213 to 0.0415 m(2)/m for the perpendicular case. A transition from a bluff body to a streamlined body occurred as the tow speeds increased. To investigate this transition, horizontal components of the nor

关键词： Macroalgae hydrodynamics Aquaculture physical model Reconfiguration of kelp Saccharina latissima

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Electrical system design of solar-powered electrical water recreational and sport vessel 1

Electrical system design of solar-powered electrical water r...

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1st International Conference on Automotive, Manufacturing, and Mechanical Engineering, IC-AMME 2018

作者： Sunaryo Shadu Imfianto, Pradhana Naval Architecture and Marine Engineering Study Program Department of Mechanical Engineering Universitas IDN Depok 16424 Indonesia

Indonesia is the world's largest archipelago with more than 17 000 islands, and the best marine tourism destination due to its beautiful beaches and underwater scenery, but Indonesia is also the most vulnerable country to be affected by climate change due to the greenhouse effect. Besides industry, the transportation sector is the highest contributor to the global greenhouse effect. In order to reduce the source of the greenhouse effect, the Indonesian Government has committed to using new and renewable energy as an alternative to fossil-based fuel. In an attempt to contribute to the Government's efforts and to advance the national marine tourism, the research is aimed to design water recreational and sport vessel that powered by a solar generated electric engine, as further development of Universitas Indonesia's solar boat participated in International Solar-boat Challenge competition in the Netherlands. The research is focused on the effective use of solar energy as the main source for powering the vessel's electrical engine, based on the existing optimum shape and dimensions of the boat. Information and data regarding the arrangement of the vessel, solar electric generation processes and vessel powering system obtained from literature study, discussion with experts, and on the spot surveys of various recreational vessels were used as input for the calculation and simulation of the vessel being investigated. The research results are expected could be further developed for other related usages such as fish farming, coastal fishing rig, floating restaurant, etc. © 2019 The Authors, published by EDP Sciences.

关键词： Greenhouse effect

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Finite Element Analysis and Topology Optimization Design of Anchor Mooring Winch Support Bracket

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IOP Conference Series: Earth and Environmental Science 2022年第1期972卷

作者： Nurul Huda Ocid Mursid -Mechanization Fisheries Study Program Sorong Polytechnic of Marine and Fisheries Indonesia Department of Naval Architecture Diponegoro University Indonesia

The weight of the deck machinery greatly affects the position of the small ship's center of gravity so that it also affects the stability of the ship. Therefore, it is necessary to conduct optimization studies to reduce the weight of ship deck machinery, especially anchor mooring winch, by reducing the weight of ship deck machinery will lower the position of the center of gravity of ship so that can improve ship stability. This paper presents the effects of a topology optimization examination based on the finite element evaluation on anchor mooring winch support bracket using the SolidWorks Simulation module. The main intention to examine is to optimize the general weight of the anchor mooring winch support bracket via way of means of thinning specific regions of the anchor mooring winch support bracket in keeping with the calculated minimum strain energy. The topology optimization algorithm that is used in the current study gives an optimal structural shape of the support bracket of the anchor mooring winch with the largest stiffness, considering the given quantity of mass so that it will be eliminated from the preliminary layout space. The complete sequence of steps for carrying out the topology control optimization study is shown, taking into account the constraints arising from the construction features and the method of manufacturing the support bracket of the anchor mooring winch. The layout became carried out, and the effects have been provided via way of means of evaluating the preliminary version and the optimized version. As the result of topology optimization study, its stress was increased by about 4MPa and mass was reduced by about 15kg in comparison with the initial design.

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