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Gravity wave interaction with multiple submerged artificial reefs

PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART M-JOURNAL OF ENGINEERING FOR THE MARITIME ENVIRONMENT 2021年第2期235卷 607-622页

作者： Vijay, K. G. Neelamani, S. Nishad, C. S. Sahoo, T. IIT Kharagpur Dept Ocean Engn & Naval Architecture Kharagpur W Bengal India Oceaneering Int Serv Ltd Chandigarh India Kuwait Inst Sci Res Environm & Life Sci Res Ctr Coastal Management Program Safat Kuwait Pandit Deendayal Petr Univ Gandhinagar Sch Technol Dept Math Gandhinagar 382007 Gujrat India

In the present study, gravity wave interaction with a series of submerged artificial permeable reefs is analysed within the framework of linearised water wave theory. For wave past porous walls of the artificial reefs, a quadratic pressure drop is assumed to account for the wave energy dissipation due to the changes in wave height. The physical problem is handled for a solution using a numerical model based on the iterative multi-domain boundary element method and the developed numerical model is validated with known results in the literature. The iterative model is compared with the numerical model based on linear pressure drop boundary condition (i.e., Darcy law). The study reveals that the wave transmission reduces with the increase in the number of reef units. It is demonstrated that the transmission coefficient can be reduced to less than 0.5 when the number of reef units is greater than or equal to three for a relative height greater than 0.7, reef porosities less than 20% and for 0.4

关键词： Artificial reefs quadratic pressure drop Darcy's law iterative multi-domain boundary element method scattering coefficients

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Propagation of Lamb waves in an elastic layer with irregular surfaces

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WAVE MOTION 2023年 119卷

作者： Ahmetolan, Semra Peker-Dobie, Ayse Deliktas-Ozdemir, Ekin Caglayan, Esra Istanbul Tech Univ Fac Sci & Letters Dept Math TR-34469 Istanbul Turkiye Piri Reis Univ Fac Engn Dept Naval Architecture & Marine Engn TR-34940 Istanbul Turkiye Istanbul Univ TEBIP High Performers Program Board Higher Educ Turkey TR-34452 Istanbul Turkiye

In this article, we investigate the problem of Lamb wave propagation in a layer composed of homogeneous, isotropic material with irregular free surfaces. It is assumed that the irregular free surfaces vary slowly in the direction of wave propagation. By employing an asymptotic perturbation method, a unique asymptotic solution for the amplitude function of Lamb waves is obtained. The dispersion relation is expressed as a function of phase velocity of waves, wave number and the direction of wave propagation. We examine the effect of irregularities of the boundary surfaces on the propagation of waves under the assumption that free surfaces have periodic properties. (c) 2023 Elsevier B.V. All rights reserved.

关键词： Lamb waves Corrugated surfaces Perturbation methods

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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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Development of an Automatic Anti Pitching System (APS) Autonomous Surface Vehicle (ASV) for Fish Mapping 3

Development of an Automatic Anti Pitching System (APS) Auton...

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3rd International Conference on Science and Technology 2019, ICST 2019

作者： Saputra, Noverdo Lukmana, Muhammad Arifudin Suranto, Purwo Joko Study Program Naval Architecture Universitas Pembangunan Nasional Veteran Jakarta Indonesia Study Program Mechanical Engineering Universitas Pembangunan Nasional Veteran Jakarta Indonesia

The common problem occurs in fish mapping using autonomous surface vehicles (ASV) is pitching stability. Some researchers have indicated that problem affects the results of mapping. The target of this system is to design an Autonomous Pitching System (APS) for ASV using numerical simulation software. The simulation is done by implement APS into the system, producing an oscillatory motion from the ASV. For both dynamics of craft in short and long periods, APS with proportional controller (P), proportional-integral controller (PI), and proportional-integral-derivative controller (PID) are developed in order to minimize the oscillatory behaviour. It was found that for the short period dynamics, the APS with PI controller was the optimal controller, followed by the PID controller and then the P controller. For the long period dynamics, the APS with PID controller was optimal. © 2020 IOP Publishing Ltd. All rights reserved.

关键词： Three term control systems

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Prediction of Chinese-lantern submarine hose tension variation in extreme sea states based on data-driven methods

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APPLIED OCEAN RESEARCH 2023年第1期139卷

作者： Hu, Ke An, Chen Bai, Xinglan Su, Jian Vaz, Murilo A. China Univ Petr Coll Safety & Ocean Engn Beijing 102249 Peoples R China Zhejiang Ocean Univ Sch Naval Architecture & Maritime Zhoushan 316022 Peoples R China Univ Fed Rio Janeiro Nucl Engn Program COPPE CP 68509 BR-21941972 Rio De Janeiro Brazil Univ Fed Rio Janeiro Ocean Engn Program COPPE CP 68508 BR-21941972 Rio De Janeiro Brazil

To predict the variation of Chinese-lantern type submarine hose tension in extreme sea states is of great significance for the monitoring, operation and lifetime assessment of catenary anchor leg mooring (CALM) systems. In this research, the machine learning algorithm in radial basis function (RBF) neural network and the deep learning algorithm in long short-term memory (LSTM) neural network model were used to predict the variation of submarine hose tension respectively, and the prediction performance of the two algorithms on the time-series variation of submarine hose tension was evaluated. During the neural network construction, the six-degree-offreedom (6-DOF) motion of CALM buoy is taken as the training parameter, while the historical tension variation data is also integrated for the correction of the prediction results. The training data are collected by hydrodynamic coupling simulation of the established CALM system with submarine hoses. Different parameter values selection of the neural network model is investigated to determine the optimal structure of the RBF and LSTM neural network models, including spread, initial learning rate, number of nodes in the hidden layer and batch size. Since the direction of environmental loads has a large effect on the response of the submarine hose, four combinations of wind, wave and currents under 100-year self-existing sea state are considered in the research. Through the case study and sensitivity analysis, it is demonstrated that the non-linear relationship between 6-DOF motion and hose tension is varied for different environmental load directions and LSTM neural network is suitable for predicting the variation of Chinese-lantern type submarine hose tension in CALM systems under different combinations of extreme sea states.

关键词： Calm system Chinese-lantern submarine hose Radial basis function neural network Long short-term memory neural network Extreme sea states Tension prediction Sensitivity analysis

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Marine energy converters: Potential acoustic effects on fishes and aquatic invertebratesa)

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JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2023年第1期154卷 518-532页

作者： Popper, Arthur N. Haxel, Joseph Staines, Garrett Guan, Shane Nedelec, Sophie L. Roberts, Louise Deng, Zhiqun D. D. Univ Maryland Dept Biol College Pk MD 20742 USA Pacific Northwest Natl Lab Coastal Sci Div Sequim WA 98382 USA Bur Ocean Energy Management Environm Studies Program Sterling VA 20166 USA Univ Exeter Dept Biosci Exeter England Univ Liverpool Sch Environm Sci Dept Earth Ocean & Ecol Sci Liverpool England Pacific Northwest Natl Lab Earth Syst Sci Div Richland WA 99354 USA Environm BioAcoust LLC Silver Spring MD 20906 USA Catholic Univ Amer Dept Mech Engn Washington DC 20064 USA Univ Michigan Dept Naval Architecture & Marine Engn Ann Arbor MI 48109 USA

The potential effects of underwater anthropogenic sound and substrate vibration from offshore renewable energy development on the behavior, fitness, and health of aquatic animals is a continuing concern with increased deployments and installation of these devices. Initial focus of related studies concerned offshore wind. However, over the past decade, marine energy devices, such as a tidal turbines and wave energy converters, have begun to emerge as additional, scalable renewable energy sources. Because marine energy converters (MECs) are not as well-known as other anthropogenic sources of potential disturbance, their general function and what is known about the sounds and substrate vibrations that they produce are introduced. While most previous studies focused on MECs and marine mammals, this paper considers the potential of MECs to cause acoustic disturbances affecting nearshore and tidal fishes and invertebrates. In particular, the focus is on particle motion and substrate vibration from MECs because these effects are the most likely to be detected by these animals. Finally, an analysis of major data gaps in understanding the acoustics of MECs and their potential impacts on fishes and aquatic invertebrates and recommendations for research needed over the next several years to improve understanding of these potential impacts are provided.

关键词： Fish

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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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Exact and heuristic algorithms for the fleet composition and periodic routing problem of offshore supply vessels with berth allocation decisions

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EUROPEAN JOURNAL OF OPERATIONAL RESEARCH 2021年第3期295卷 908-923页

作者： Vieira, Bruno S. Ribeiro, Glaydston M. Bahiense, Laura Cruz, Roberto Mendes, Andre B. Laporte, Gilbert Univ Fed Rio de Janeiro Transportat Engn Program Alberto Luiz Coimbra Inst Grad Sch & Res Engn Rio De Janeiro Brazil Univ Fed Rio de Janeiro Syst Engn & Comp Sci Program Alberto Luiz Coimbra Inst Grad Sch & Res Engn Rio De Janeiro Brazil Univ Sao Paulo Dept Naval Architecture & Ocean Engn Sao Paulo Brazil HEC Montreal Distribuit Management Montreal PQ Canada Univ Bath Sch Management Bath Avon England

This paper presents a branch-and-cut algorithm and an adaptive large neighborhood search (ALNS) heuristic for the periodic supply vessel planning problem (PSVPP) arising in the upstream offshore petroleum logistics chain. Platform supply vessels support the offshore oil and gas exploration and production activities by transporting all the necessary material and equipment back and forth between offshore units and an onshore supply base according to a delivery schedule. The PSVPP consists of solving a periodic vehicle routing problem and simultaneously determining an optimal fleet size and mix of heterogeneous offshore supply vessels, their weekly routes and schedules for servicing the offshore oil and gas installations, and the berth allocations at the supply base. The branch-and-cut algorithm considers a reduced formulation for the problem which performs much better than the complete one, and easily finds optimal solutions for the smaller and most of the clustered instances. The ALNS heuristic contains new features which include multiple starts and spaced local searches. These algorithms were tested on instances with up to 79 offshore units, providing better results than the best available. (c) 2021 Elsevier B.V. All rights reserved.

关键词： OR in maritime industry Offshore supply vessel planning Periodic VRP Heterogeneous fleet sizing Berth allocation B&C algorithm ALNS heuristic

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CFD SIMULATIONS FOR TRAJECTORY PREDICTION OF AN UNDERWATER GLIDER UNDER THE INFLUENCE OF OCEAN CURRENTS

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Journal of Taiwan Society of naval Architects and Marine Engineers 2023年第3期42卷 129-137页

作者： Chen, H.-C. Liu, T.-L. Pan, K.-C. Master Program of Naval Architecture and Ocean Engineering CCIT National Defense University Taiwan Department of Power Vehicle and Systems Engineering CCIT National Defense University Taiwan

The Autonomous Underwater Glider (AUG) is equipped with a self-adjusting buoyancy engine, allowing it to modify its buoyancy and center of gravity. Through this capability, the AUG can control its motion and achieve both ascending and descending movements. The theoretical mechanism employed by the AUG for adjusting its depth is based on this motion control. However, as an energy-efficient underwater vehicle, the AUG primarily relies on ocean currents for propulsion, which significantly impacts its trajectory in terms of direction and speed. Therefore, trajectory planning plays an indispensable role in the AUG's mission of collecting oceanographic data, highlighting its critical importance. To address this issue, this research aims to apply Computational Fluid Dynamics (CFD) numerical simulations to predict the glider's trajectory under the influence of ocean currents. This analysis will help construct an appropriate operational mode for the underwater glider in various oceanic environments. Regarding the application of CFD to predict the underwater glider's trajectory influenced by ocean currents, the preliminary flow field simulation analysis and feasibility study have been completed. From the simulation results, it is evident that variations in ocean current velocity will have a substantial impact on the glider's initial motion attitude, horizontal speed, as well as the distance covered during each diving and ascending phase. The research findings are expected to significantly contribute to the design and development of a new domestic underwater glider. © 2023 Taiwan Society of naval Architects and Marine Engineers. All rights reserved.

关键词： Ocean currents

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Dynamic behavior of steel catenary riser at the TDZ considering soil stiffness degeneration and trench development

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OCEAN ENGINEERING 2022年 250卷 110970-110970页

作者： Chen, Jiaming Bai, Xinglan 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

This work is focused on developing a riser-soil interaction model with soil stiffness degradation and trench formation, herein named the weakening model, for steel catenary riser (SCR) touchdown zone (TDZ) fatigue damage assessment. At present the riser-soil interaction models mainly include the linear, non-linear hysteretic and P-y curve behaviors. However, there are still some drawbacks in the existing models, such as the soil stiffness degradation is not considered in the P-y curve, and the trench development is not described in the hysteretic curve. The new procedure for global analysis of SCRs is obtained based on the weakening model and imple-mented in the program CABLE3D RSI. Results show that the soil strength gradually degenerates in the cyclic riser-soil interaction weakening model when compared with the P-y curve model. The ultimate soil strength values were selected for comparison of fatigue analysis for a typical case study, and the fatigue life is increased compared with the case without the strength degradation with the increase of the weakening factor. The results of this study can provide an effective and convenient method considering degradation of soil strength and trench development for predicting the response and fatigue life of SCRs.

关键词： Steel catenary riser Riser-soil interaction Soil stiffness degeneration Trench development Weakening model

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