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2025 IEEE Underwater Technology, UT 2025

作者： Cheng, Ming-Hung Hwang, Robert R. National Academy of Marine Research Marine Industry and Engineering Research Center Kaohsiung Taiwan National Taiwan Ocean University Department of System Engineering and Naval Architecture Keelung Taiwan

ISBN: (纸本)9798331534189

Taiwan, surrounded by the ocean, benefits from the powerful Kuroshio Current along its eastern coastline, presenting substantial potential for harnessing marine energy resources. To capitalize on these opportunities, the National Academy of Marine Research initiated research and development efforts in 2020, focusing on key technologies for ocean current energy and conducting sea trials. These efforts are expected to culminate in the development of a Floating Kuroshio Turbine (FKT). To gain a comprehensive understanding of the FKT's underwater operations, this study employs a series of numerical simulations. Using the Navier-Stokes equations, combined with the $\mathrm{k}-\varepsilon$ turbulence model and dynamic mesh techniques, a numerical model for fluid-structure interaction is developed. The simulation results reveal that as flow velocity increases, the vortices behind the unit become increasingly complex. For the 20 kW FKT, the dual-blade system with counter-rotating blades reduces the downstream impact distance compared to a single-unit setup, limiting it to approximately 4 to 5 times the length of the unit's longest side. The primary objective of this study is to enhance understanding of the system's performance under different FKT, providing critical insights for future design optimizations and environmental impact assessments. © 2025 IEEE.

关键词： Navier Stokes equations

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Structural impact under accidental LNG release on the LNG bunkering ship: Implementation of advanced cryogenic risk analysis

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Process Safety and Environmental Protection 2024年 186卷 329-347页

作者： Nubli, Haris Jung, Dongho Kim, Sang Jin Sohn, Jung Min Department of Naval Architecture and Marine System Engineering Pukyong National University Korea Republic of Department of Offshore Platform Research Division Korea Reseacrch Institute of Ships and Ocean Engineering Korea Republic of Department of Marine Environment and Engineering National Sun Yat-sen University Kaohsiung Taiwan Department of Marine Design Convergence Engineering Pukyong National University Korea Republic of

The potential risk associated with the accidental release of Liquefied Natural Gas (LNG) is a notable concern during the design phase of gas-handling facilities. One of the risk is an excessive cryogenic exposure to structures or equipment, leading to hazardous situations. This study aims to introduce a novel method that implements Advanced Cryogenic Risk Analysis (ACRA) to enhance the safety of LNG bunkering ship structure in case of cryogenic flow leakage. The method involves evaluating thermal loads based on the preceding simulated LNG release scenarios using Computational Fluid Dynamics (CFD). These thermal parameters are then employed in structural analysis through the Finite Element (FE) approach. The integration of thermal data from CFD simulations into the FE model was achieved using the Random Forest algorithm. The LNG bunkering structure is represented using DH36-grade steel material. Furthermore, to accurately capture the mechanical properties of DH36 steel, cryogenic tensile tests were conducted across a temperature range from 298.15 K to 113.15 K. The resulting stress-strain data from these tests were utilized to establish a reliable material model for conducting FE analysis. This paper comprehensively presents a novel ACRA procedure by utilizing physical parameter of the gas release cosnequence such as the steel temperature profile to identify the brittle failure under the accidental gas release on the LNG bunkering ship. In addition, quantitative risk analysis (QRA) was also presented regarding the cryogenic spill hazard, to link the probability and consequence aspects of the LNG bunkering risk, particularly the results of steel temperature, stress, and strain experienced by the ship's structure. Furthermore, the individual risk was also estimated. The implications of the findings are discussed in detail regarding the cryogenic risk, cryogenic tensile test and numerical analyses. © 2024 The Institution of Chemical Engineers

关键词： Hazardous materials spills

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The chamber design of the L-shaped oscillating water column using artificial neural network 15th

The chamber design of the L-shaped oscillating water column ...

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15th European Wave and Tidal Energy Conference, EWTEC 2023

作者： Lin, C.-C. Chow, Y.-C. Nguyen, D.T. Department of mechanical and mechatronic engineering and Center for Ocean Energy System National Taiwan Ocean University Keelung202301 Taiwan Department of systems engineering and naval architecture and Center for Ocean Energy System National Taiwan Ocean University Keelung202301 Taiwan Department of systems engineering and naval architecture National Taiwan Ocean University Keelung202301 Taiwan

Among the various wave energy converters available, the oscillating water column (OWC) shows several advantages in implementation and maintenance. In dealing with the survivability issues, incorporating OWCs into reinforced concrete constructions, like breakwaters, is more cost-effective and can endure the effects of seawater impact and erosion. This paper focuses on optimizing the chamber design of a novel OWC type, the L-shaped OWC, by establishing a general design procedure to achieve higher power-capturing efficiency. The performance of the OWC is influenced significantly by the OWC’s geometry under a specified wave condition. It is found that the dimension of the air chamber and water duct is critical in determining OWC’s performance. We develop the chamber design procedure based on the artificial neural network approach by establishing a collection of two-dimensional RANS simulations as the training database. In the end, the performance of the optimal design is compared with the design of a previous paper. The result shows that the capture factor of the present optimized chamber geometry of the L-shaped OWC is 60% more than a former design. © 2023 European Wave and Tidal Energy Conference. This paper has been subjected to single-blind peer review.

关键词： Tidal power

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Guidelines for Determining the Extent of Toxic Areas for Ships Using Ammonia as a Fuel 34th

Guidelines for Determining the Extent of Toxic Areas for Shi...

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34th International Ocean and Polar engineering Conference, ISOPE 2024

作者： Nam, Hyunjoon Kim, Do Kyun Kim, Sunghee Shin, Dongkyu System Safety Research Department HD Korea Shipbuilding and offshore Engineering Co Ltd Gyeonggi-do Korea Republic of Department of Naval Architecture and Ocean Engineering Seoul National University Seoul Korea Republic of

ISBN: (纸本)9781880653784

Guidelines are proposed to determine the extent of toxic area for ships using ammonia as a fuel. The guidelines clearly define the purpose of Toxic Area Classification and suggest a specific reference toxic concentration for determining the extent of toxic areas. Included within the guidelines is a chart developed to estimate hazardous distances according to the volumetric characteristics of toxic releases. A case study conducted on a large ammonia-fueled container ship demonstrates the effectiveness and practicality of the guidelines. The proposed guidelines can serve as a valuable tool for determining and justifying the extent of toxic areas. © 2024 by the International Society of Offshore and Polar Engineers (ISOPE).

关键词： Ammonia

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PIPELINE DAMAGE DETECTION METHOD USING THE NON-INTRUSIVE PIPE PRESSURE MONITORING SENSOR 29

PIPELINE DAMAGE DETECTION METHOD USING THE NON-INTRUSIVE PIP...

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29th International Congress on Sound and Vibration, ICSV 2023

作者： Jung, Byungchang Noh, Hyungju Park, Jin-Woo Shin, Yun-Ho Department of System Dynamics Korea Institute of Machinery & Materials Daejeon Korea Republic of Dept. of Naval Architecture & Ocean Engineering Pusan National University Busan Korea Republic of

ISBN: (纸本)9788011034238

In order to prevent unexpected accident due to a pipe damage, it is necessary to quickly detect location of the damage. Damage in a pipeline can be classified into leak and rupture according to the size of the damage. In this research, we studied two pipeline damage localization methods, which employ the non-intrusive pipe pressure monitoring sensor: (1) a cross-correlation function-based leak localization method and (2) a rupture localization method based on Recurrence Plot(RP) and Convolutional Neural Network(CNN). Frist, to develop a cross-correlation function-based leak localization method, two non-intrusive pipe pressure monitoring sensors were installed on the pipeline testbed, and the fluid-pipe coupled vibration signals were measured when a pipe was leak. The time difference between the measured signals was calculated using the cross-correlation function, and it was confirmed that leak location can be predicted within about 7.8% error. Second, to develop a RP-CNN based rupture localization method, pressure change at various locations in a pipeline testbed were measured when rupture is occurred using non-intrusive pipe pressure monitoring sensors. After that, the pressure data were converted into images using RP, and the images were classified using CNN. It was found that pressure data measured close to the rupture are well classified with the pressure data measured away from the rupture. © 2023 Proceedings of the International Congress on Sound and Vibration. All rights reserved.

关键词： Testbeds

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Broadband noise prediction of a pump-jet propeller for submarine using wall pressure spectrum 24

Broadband noise prediction of a pump-jet propeller for subma...

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24th International Congress on Acoustics, ICA 2022

作者： Kim, Min-Hyeok Hong, Suk-Yoon Song, Jee-Hun Park, Il-Ryong Kim, Min-Jae Department of Naval Architecture and Ocean Engineering Seoul National University Korea Republic of Institute of Engineering Research Seoul National University Korea Republic of Department of Naval Architecture and Ocean Engineering Chonnam National University Korea Republic of Department of Naval Architecture and Ocean Engineering Dongeui University Korea Republic of Naval System R&D Institute Agency for Defense Development Korea Republic of

Since submarines generally operate in non-cavitating conditions and the use of a Pump-Jet Propeller (PJP) instead of a conventional single propeller can decrease tone noises, contributions of mid-to-high frequency broadband noise to radiation noise become significant. PJP consists of a decelerating duct, a fixed stator adjusting flow direction, and a rotating rotor generating flows. In this paper, broadband noise from trailing edges was analyzed to predict the radiation noise at multiple observation points, and the contribution of each component was compared. Since noise sources up to high frequency are obtained from small eddies in turbulent boundary layers, Wall Pressure Spectrum (WPS) was used with input data given by Computational Fluid Dynamics (CFD) simulation with Reynolds-averaged Navier-Stokes(RANS) turbulence model. Thin airfoil theory was used to predict distributions of acoustic pressure on blades. Noise radiation from trailing edges to far-field observation points was calculated by applying duct green's function through PJP and free-field green's function after its exit. By comparing the contribution, it can be identified which parts need to be redesigned to reduce the noise, and decreasing the radiation noise in all directions can be achieved. © ICA *** rights reserved

关键词： Broadband noise Pump-jet propeller Wall pressure spectrum

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Optimal Design of the Overtopping Wave Energy Converter Based on Fluid–Structure Interaction Simulation

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Journal of Coastal Research 2024年第SP1期116卷 578-582页

作者： Sung-Hwan An Geun-Gon Kim Jong-Hyun Lee Department of Ocean System Engineering Gyeongsang National University Tongyeong Republic of Korea Department of Naval Architecture and Ocean Engineering Gyeongsang National University Tongyeong Republic of Korea

An, S.-H.; Kim, G.-G., and Lee, J.-H., 2023. Optimal design of the overtopping wave energy converter based on fluid–structure interaction simulation. In: Lee, J.L.; Lee, H.; Min, B.I.; Chang, J.-I.; Cho, G.T.; Yoon, J.-S., and Lee, J. (eds.), Multidisciplinary Approaches to Coastal and Marine Management. Journal of Coastal Research, Special Issue No. 116, pp. 578-582. Charlotte (North Carolina), ISSN *** wave overtopping system in wave power generation systems is called the Overtopping Wave Energy Converter (OWEC). The performance of the OWEC is affected by wave height and period. Wave characteristics, such as wave height, period, and direction, vary with environmental conditions, which make it difficult for the OWEC to generate stable electric power. To mitigate this issue, appropriate OWEC designs based on environmental conditions and wave characteristics must be investigated. In this study, the hydraulic efficiency of the OWEC and the load acting on it were calculated using the Smoothed Particle Hydrodynamics (SPH) based on the environmental conditions along the Ulleungdo coast, and the structural safety of the optimized OWEC model was verified. Moreover, a particle-based simulation was performed to confirm the effect of design parameters on energy efficiency. Additionally, the load acting on the OWEC was calculated, and the optimization method was used to design six types of substructures. Finally, structural analysis was conducted, confirming that all six types avoided the design model's structural resonance period.

关键词： design optimization Overtopping Wave Energy Converter smoothed particle hydrodynamics structural analysis

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Numerical Study for the Variations of Flow Field During FKT Operation

Numerical Study for the Variations of Flow Field During FKT ...

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International Symposium on Underwater Technology

作者： Ming-Hung Cheng Robert R. Hwang Marine Industry and Engineering Research Center National Academy of Marine Research Kaohsiung Taiwan Department of System Engineering and Naval Architecture National Taiwan Ocean University Keelung Taiwan

ISBN: (数字)9798331534189

ISBN: (纸本)9798331534196

关键词： Oceans system performance Simulation Numerical simulation Mathematical models Numerical models Underwater technology Turbines Research and development Navier-Stokes equations

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A Simplified Nonlinear Analysis Procedure for the Flexible Risers in Subjected to Combined Loading Effects 14th

A Simplified Nonlinear Analysis Procedure for the Flexible R...

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14th International Symposium on Practical Design of Ships and Other Floating Structures, PRADS 2019

作者： Kim, Jeong Du Jang, Beom-Seon Department of Naval Architecture and Ocean Engineering Seoul National University Seoul Korea Republic of Research Institute of Marine System Engineering Department of Naval Architecture and Ocean Engineering Seoul National University Seoul Korea Republic of

ISBN: (纸本)9789811546792

A dynamic analysis of flexible risers in large-scale domain remains the offshore industrys most challenging problems. The cross section of flexible risers, consisting of multiple metallic and plastic layers, experiences inter-layer slippage during cyclic bending. This results in nonlinear and hysteretic bending behavior with rapid dissipation of energy. For the dynamic analysis for flexible risers in the large scale domain, this study replaces all layers of risers with simple beam elements with a nonlinear beam model. This simplified beam model traces the curvature to bending moment relation and captures the variation of stiffness due to the onset of slippage. The suggested methods formulate both the change of configuration due to large deflection and contact between risers and seabed, therefore more realistic and effective analysis can be achieved. In the current study, the details of the analysis method are described. Main formulation methods of the total Lagrangian framework and the interaction between risers and seabed are described as well as the nonlinear bending model for flexible risers. The validity of the developed method is examined through some case studies, and the results show how the bending nonlinearity of flexible risers affects the overall behavior of riser systems during its operation. © 2021, Springer Nature Singapore Pte Ltd.

关键词： Stiffness

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Experimental Study on Flow Kinematics and Pressure Characteristics of Dam Break Flow

SSRN

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SSRN 2023年

作者： Kim, Hyung Joon Kim, Jong Mu Kim, Jae Hong Jung, Kwang Hyo Lee, Gang Nam Department of Naval Architecture and Ocean Engineering Pusan National University Korea Republic of Department of Ocean System Engineering Jeju National University Korea Republic of

This paper presents an experimental investigation of flow kinematics and pressure characteristics of dam break flow. The experiments were performed in 2D prismatic channel, obtaining the velocity fields by particle image velocimetry (PIV) measurement for the entire dam break flow, and shadowgraph image technique was applied to analyze the generation type and flow stage. Pressure sensors were installed on the vertical wall and bottom of the channel to analyze the characteristics of the pressure distribution. From the experimental results, the generation types and flow stages of the dam break flow could be categorized three stages. Flow kinematics of the dam break flow were provided in comparison with the analytic solutions. The energy variation during the dam break flow was calculated for the entire dam break flow system using the instantaneous velocity fields, and the energy dissipations during the flow were analyzed in the study. Pressure distributions were presented for the distinct generation phases and analyzed on its component of dynamic and hydrostatic pressures. The extensive experimental results provided in the study can be used for estimating complex impact loads, which are challenging to predict, and contribute as a validation model for various numerical studies for multiphase flow in engineering purposes. © 2023, The Authors. All rights reserved.

关键词： Pressure distribution

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