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A mathematical study of a two-layer fluid flow system in the presence of a floating breakwater in front of VLFS

Applied Mathematical Modelling 2023年第1期122卷 706-730页

作者： Barman, Koushik Kanti Chanda, Ayan Tsai, Chia-Cheng Center of Excellence for Ocean Engineering National Taiwan Ocean Unviersity Keelung Taiwan Department of Ocean Engineering and Naval Architecture Indian Institute of Technology Kharagpur West Bengal India Bachelor Degree Program in Ocean Engineering and Technology National Taiwan Ocean University Keelung Taiwan

The present study deals with the usefulness of a surface-piercing porous structure of definite width in a two-layer fluid placed at a finite distance from a floating elastic plate to mitigate the hydrodynamic response of the elastic plate. We use linear water wave theory with the eigenfunction expansion approach to develop analytical solutions to the model problem in finite water depth. Here, we identify and explore the complete parameter space associated with the problem by examining the hydrodynamic coefficients for waves in surface and internal modes, plate elevation, shear force, bending moment, wave loads on the elastic plate, flow amplitude in the plate-covered region and wave attenuation. We investigate the effectiveness of structures of various configurations and geometries on wave scattering. This study demonstrates an oscillatory pattern of wave reflection in the confined region between the plate and the breakwater. Moreover, optima in the oscillatory pattern can be observed due to the resonating interaction of waves and the breakwater-plate system. Furthermore, the research shows that an ideal width and distance between the breakwater and floating plate can be calculated while assuming an appropriate configuration of the porous structure to create a breakwater-plate system with a reasonable efficiency that possesses both reflection and dissipation properties. The design of various types of coastal structures employed in the marine environment for the reflection and dissipation of wave energy at continental shelves dominated by stratified fluid, described here as a two-layer fluid, will significantly benefit from the findings of the current study. © 2023 Elsevier Inc.

关键词： Eigenvalues and eigenfunctions

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Aero-Hydrodynamic Coupled Dynamic Characteristics of Semi-Submersible Floating Offshore Wind Turbines Under Inflow Turbulence

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China ocean engineering 2023年第4期37卷 660-672页

作者： JIANG Hai-rui BAI Xing-lan Murilo A.VAZ School of Naval Architecture and Maritime Zhejiang Ocean UniversityZhoushan 316022China Key Laboratory of Offshore Engineering Technology of Zhejiang Province Zhoushan 316022China Ocean Engineering Program Federal University of Rio de JaneiroRio de JaneiroBrazil

In this study,the frequency characteristics of the turbulent wind and the effects of wind-wave coupling on the low-and high-frequency responses of semi-submersible floating offshore wind turbines(FOWT)are *** wave load components,such as first-order wave loads,combined first-and second-order difference-frequency wave loads,combined first-and second-order sum-frequency wave loads,and first-and complete second-order wave loads are taken into consideration,while different turbulent environments are considered in aerodynamic *** com-parison is based on time histories and frequency spectra of platform motions and structural load responses and statistical *** findings indicate that the second-order difference-frequency wave loads will significantly increase the natural frequency of low-frequency motion in the responses of the platform motion and structure load of the semi-submersible platform,which will cause structural fatigue *** the action of turbulent wind,the influences of second-order wave loads on the platform motion and structural load response cannot be ignored,especially under extreme sea ***,in order to evaluate the dynamic responses of semi-submersible FOWT more accurately,the actual environment should be simulated more realistically.

关键词： turbulence characteristics floating offshore wind turbines second-order hydrodynamic loads low-and high-frequency responses aero-hydrodynamic coupling

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Flexural-gravity wave interaction with undulating bottom topography in the presence of uniform current: An asymptotic approach

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Applied Mathematical Modelling 2024年 133卷 41-64页

作者： Barman, Koushik Kanti Chanda, Ayan Tsai, Chia-Cheng Mondal, Sandipan Center of Excellence for Ocean Engineering National Taiwan Ocean University Keelung Taiwan Department of Mathematics Birla Institute of Technology Mesra Jharkhand India Department of Ocean Engineering and Naval Architecture Indian Institute of Technology West Bengal Kharagpur India Bachelor Degree Program in Ocean Engineering and Technology National Taiwan Ocean University Keelung Taiwan Department of Environmental Biology and Fishery Science National Taiwan Ocean University Keelung Taiwan

Using an asymptotic method, this article deals with flexural-gravity wave scattering with undulating bottom topography, including the effect of uniform currents. The interest in this problem lies in developing second-order solutions using the Fourier transform, which minimises the error gap between first and second-order solutions. The present method allows the physical processes involved in the sea-bed topography, uniform current, plate-covered surface, and wave interaction to be studied. Specifically, we observe Bragg resonance between the flexural-gravity waves and the bottom ripples, which are associated with the reflection of incident wave energy. We examine the effects of wave current and emphasise how crucial the asymptotic expansion method is to the emergence of the current response. We demonstrate that bottom topography dominates the effects of Bragg resonance for depth Froude numbers valued at 0.8 or less. Further, most reflected wave components have their frequencies shifted by the current, and wave action conservation causes reflected wave energy to be enhanced for following currents. Using the Joint North Sea Wave Observation Project spectrum and the discrete Fourier transform, the theory derived in the frequency domain is shown in the time domain to analyse wave propagation through the whole system. © 2024

关键词： Time domain analysis

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Meshless generalized finite difference method with a domain-selection method for solving degenerate boundary problems

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engineering Analysis with Boundary Elements 2023年第1期152卷 185-193页

作者： Huang, Ji Lyu, Hong-Guan Fan, Chia-Ming Chen, Jiahn-Horng Naval Architecture and Shipping College Guangdong Ocean University Zhanjiang524088 China School of Ocean Engineering and Technology Sun Yat-sen University Zhuhai519082 China Doctoral Degree Program in Ocean Engineering Technology National Taiwan Ocean University Keelung20224 Taiwan Department of Harbor and River Engineering National Taiwan Ocean University Keelung20224 Taiwan Shih Yen-Ping Center for Underwater Technology National Taiwan Ocean University Keelung20224 Taiwan National Academy of Marine Research Kaohsiung80661 Taiwan

This paper is dedicated to presenting a combined Generalized Finite Difference Method (GFDM) and Domain-Selection Method (DSM) approach for solving degenerate boundary problems which are usually encountered in engineering simulations. Compared with traditional Domain-Decomposition Method (DDM), the most critical advantage of the present GFDM-DSM is that it is entirely free from matching continuous boundary conditions for different parts of the fluid domain of interest, which is sometimes hard to perform for specific situations. Instead, the only prerequisite of the present GFDM-DSM is to identify which sub-domain each computational node belongs to, and then a linear algebraic system can be assembled according to the pattern of domain-selection. Four benchmarks are performed to validate the convergence and accuracy of the present GFDM-DSM. It is shown that the present GFDM-DSM holds satisfactory accuracy for solving degenerate boundary problems. In particular, the present DSM is a flexible strategy since it can be also combined with other localized domain-type meshless methods in practical applications. © 2023 Elsevier Ltd

关键词： Domain decomposition methods

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Design and Experiment of a Water Hydraulic Artificial Muscle Actuated Diving Auxiliary Operating System 9

Design and Experiment of a Water Hydraulic Artificial Muscle...

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9th International Conference on Fluid Power and Mechatronics, FPM 2023

作者： Che, Jin-Kai Zhang, Zeng-Meng Yang, Yong Wang, Ji-Xiang Chen, Yin-Long Gong, Yong-Jun Yang, Rui College of Naval Architecture and Ocean Engineering Dalian Maritime University Dalian China Dalian University of Technology Open Research Program of Key Laboratory for Precision and Non-traditional Machining Technology of Ministry of Education of China Dalian China

ISBN: (数字)9798350304947

ISBN: (纸本)9798350304947

A diving auxiliary operating system based on water hydraulic artificial muscle (WHAM) was developed to enhance the efficiency of underwater work for divers. The water filling pressure of the WHAM was calculated by the interaction torque between the operating system and the wearer. Power assisted experiments were conducted to imitation the underwater rigging connections, desilting, and obstacle clearance for rescue operations. The power assistance effect was evaluated through a comparison of the surface electromyography (EMG) intensity between the wearer with and without the auxiliary operating system. The experiments results indicate that the auxiliary system can enhance the diver's operational capacity 43%. © 2023 IEEE.

关键词： Muscle

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Bragg scattering of gravity waves by a sea bed of varying depth in the presence of uniform current covered by a floating membrane

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Physics of Fluids 2024年第1期36卷 012118-012118页

作者： Barman, Koushik Kanti Chanda, Ayan Tsai, Chia-Cheng Hsu, Tai-Wen Center of Excellence for Ocean Engineering National Taiwan Ocean University Keelung Taiwan Department of Ocean Engineering and Naval Architecture Indian Institute of Technology Kharagpur West Bengal Kharagpur India Bachelor Degree Program in Ocean Engineering and Technology National Taiwan Ocean University Keelung Taiwan Department of Harbor and River Engineering National Taiwan Ocean University Keelung202301 Taiwan

We present an asymptotic approach to solving the water wave scattering by undulating bottom topography in the presence of uniform currents where a flexible membrane covers the upper surface. The interest in this problem lies in the development of asymptotic solutions using the Fourier transform under the action of uniform currents. The method allows the physical processes involved in the sea-bed topography and membrane-covered surface and wave interactions to be studied. In particular, we identify the existence of Bragg resonance between gravity waves and the bottom ripples, which are associated with the reflection of incident wave energy. We consider the impacts of uniform current, and we highlight the central role of the asymptotic expansion method in the evolution of the response of current. For depth Froude number in the range of 0.4-0.7, the effects of bottom topography on Bragg resonance dominate. The current shifts the frequency of the most reflected wave components, and wave action conservation results in amplified reflected wave energies for the following currents. The theory developed in the frequency domain is illustrated in the time domain using discrete Fourier transform with the Joint North Sea Wave Observation Project (JONSWAP) spectrum [Hasselmann et al., J. Phys. oceanogr. 10, 1264 (1980)] to analyze wave propagation through the whole system. © 2024 Author(s).

关键词： Gravity waves

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A FRAMEWORK FOR DEFINING RISK-BASED INSPECTION PLANS FOR SUBSEA EQUIPMENT 42

A FRAMEWORK FOR DEFINING RISK-BASED INSPECTION PLANS FOR SUB...

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ASME 2023 42nd International Conference on ocean, Offshore and Arctic engineering, OMAE 2023

作者： Schleder, Adriana M. Maturana, Marcos C. Martins, Marcelo R. Melo, Paulo F. F. Frutuoso E. de Barros, Leonardo O. Orlowski, Rene T. C. Naval Architecture and Ocean Engineering Department University of São Paulo São Paulo Brazil COPPE Graduate Program of Nuclear Engineering Federal University of Rio de Janeiro Rio de Janeiro Brazil Research and Development Center CENPES Petrobras Rio de Janeiro Brazil

ISBN: (纸本)9780791886847

Cost and risk optimization is a central issue in the offshore Oil and Gas sector, and risk-based approaches has been more and more employed to assist the segment in the concretization of that goal. In this sense, the use of Risk Based Inspection by the oil industry has increased. The inspection procedure aims mitigating the uncertainty related to the asset degradation state, enabling a better quantification of the actual damage, and, consequently, increasing the accuracy of remaining life projections. However, the costs involved in offshore subsea inspections are considerable. Therefore, the optimization of inspection plans plays a crucial role in the definition of an asset management program economically balanced. To perform an efficient optimization, it is important not only obtain an effective optimization algorithm but also achieve a high quality of the information used as input. In other words, an adequate definition of the risk indexes used is necessary, as well as the entire process used to quantify them. In this context, this paper presents a framework for obtaining the optimized inspection plans, starting from the assessment of the risk associated with the failure modes, moving on through the process of defining risk indices and, finally, presenting the optimization process itself. In this way, the framework proposed presents all the phases necessary to obtain optimized inspection plans, including the stage of preparation for the optimization process. Finally, the application of the proposed framework is illustrated by the elaboration of the inspection plans for a subsea manifold. Copyright © 2023 by ASME.

关键词： Inspection

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Component Criticality Rating of a Subsea Manifold using FMECA 32nd

Component Criticality Rating of a Subsea Manifold using FMEC...

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32nd European Safety and Reliability Conference, ESREL 2022

作者： Nicolau, Andressa S. Martins, Maximiano C. Paulo, Fernando F. Melo, Frutuoso E. Schleder, Adriana M. Martins, Marcelo R. De Barros, Leonardo O. Orlowski, Rene Thiago C. COPPE Graduate Program of Nuclear Engineering Federal University of Rio de Janeiro Rio de Janeiro Brazil LabRisco Analysis Evaluation and Risk Management Laboratory Naval Architecture and Ocean Engineering Department University of Sao Paulo Sao Paulo Brazil CENPES Research and Development Center of Petrobras Petrobras Brazil

ISBN: (纸本)9789811851834

Subsea manifold is a metallic structure fixed to the seabed, in which valves and accessory equipment are installed that make it possible to couple Wet Christmas Trees and other production systems (such as Pipeline End Manifold, Pipeline End Termination and risers);it is required during the completion and production of oil and gas wells. The failure of the subsea manifold can cause serious damage to the environment and human health, as well as stop production causing the loss of large foreign exchange, so ensuring its integrity is extremely important for the sector. In this article a Failure Mode, Effects and Criticality Analysis is presented for the criticality classification of the components of a typical subsea manifold cluster, Pipeline end manifold and Pipeline end termination. The final effect of equipment failure in the manifold was evaluated as a function of production interruption, production reduction, rupture, environmental pollution, plugging, leakage and structural collapse. Different means of detection were considered. The results of this study provide information about the weakness of the subsea manifold equipment. It is expected that this paper can contribute to future analysis of similar equipment and means to contribute to future work involving risk analysis, and inspection maintenance plan. © 2022 ESREL2022 Organizers. Published by Research Publishing, Singapore.

关键词： Christmas trees (wellheads)

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Meshless generalized finite difference method with a domain-decomposition method for solving Helmholtz equation and its application to caisson resonance problems

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ocean engineering 2023年 271卷

作者： Huang, Ji Lyu, Hong-Guan Chen, Jiahn-Horng Fan, Chia-Ming School of Naval Architecture and Maritime Guangdong Ocean University Zhanjiang524088 China School of Ocean Engineering and Technology Sun Yat-sen University Zhuhai519082 China Doctoral Degree Program in Ocean Engineering Technology National Taiwan Ocean University Keelung20224 Taiwan Shih Yen-Ping Center for Underwater Technology National Taiwan Ocean University Keelung20224 Taiwan National Academy of Marine Research Kaohsiung80661 Taiwan Department of Harbor and River Engineering National Taiwan Ocean University Keelung20224 Taiwan

This paper aims at presenting a meshless Generalized Finite Difference Method (GFDM) for solving the Helmholtz equation. In particular, in order to tackle the problem where a fluid domain is divided into different parts by a thin-wall structure, a Domain-Decomposition Method (DDM) is introduced to prevent interactions between node pairs coming from different parts of the flow domain. Two rigorous benchmarks are performed to validate the convergence and accuracy of the present GFDM-DDM model. Furthermore, caisson resonance problems are also investigated and discussed based on the novel numerical tool. It is shown that the present GFDM-DDM model can provide satisfactory predictions for resonance modes in caisson resonance problems, and hence can be treated as a powerful numerical tool in ocean engineering design due to its accurate and efficient characteristics. © 2023 The Authors

关键词： Caissons

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Response of the Offshore Jacket Platform at its Ultimate Strength Under Operating and Extreme Loads

SSRN

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SSRN 2022年

作者： Othman, Nor Adlina Mohd, Mohd Hairil Offshore Engineering and Naval Architecture Research Interest Group Maritime Technology Program Faculty of Ocean Engineering Technology and Informatics Universiti Malaysia Terengganu Kuala Terengganu21300 Malaysia

Before reassessing the reliability condition of an offshore jacket platform, it is essential to understand the behaviours that the offshore platform exhibits while it is at sea, which are measured in terms of environmental loads: under operating and extreme conditions. Metocean data from a 1-year return period (operating condition) and a 100-year return period (storm condition) are used to predict the four-legs jacket platform's behaviour. Also, two values of minimum design water depth (WD) of 105.9 m and maximum design WD of 115.4 m are chosen. The Structural Analysis Computer Software (SACS), a non-linear finite element analysis software, is used to calculate the jacket platform's ultimate strength, called pushover analysis. The analysis result will determine the Reserve Strength Ratio (RSR) as an approach to examining the offshore jacket platform's ultimate strength. Responses to the offshore jacket platform are base shear design, base shear ultimate, rotation, displacement, and moment, which illustrate the behaviour of the offshore jacket platform. Eight combinations of environmental load directions are applied at 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315° to obtain the structure's weakest part. 45° is the critical direction for maximum design WD, while 90° is the critical direction for minimum design WD. © 2022, The Authors. All rights reserved.

关键词： Drilling platforms

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