Pub Date : 2025-02-01DOI: 10.1016/j.joes.2023.07.002
Liang Zhao , Yong Bai , Jeom Kee Paik
The idea of dispatching multiple unmanned surface vehicles (USVs) to undertake marine missions has ignited a burgeoning enthusiasm on a global scale. Embarking on a quest to facilitate inland water monitoring, this paper presents a systematical approach concerning global path planning and path following for heterogeneous USVs. Specifically, by capturing the heterogeneous nature, an extended multiple travelling salesman problem (EMTSP) model, which seamlessly bridges the gap between various disparate constraints and optimization objectives, is formulated for the first time. Then, a novel Greedy Partheno Genetic Algorithm (GPGA) is devised to consistently address the problem from two aspects: (1) Incorporating the greedy randomized initialization and local exploration strategy, GPGA merits strong global and local searching ability, providing high-quality solutions for EMTSP. (2) A novel mutation strategy which not only inherits all advantages of PGA but also maintains the best individual in the offspring is devised, contributing to the local escaping efficiently. Finally, to track the waypoint permutations generated by GPGA, control input is generated by the nonlinear model predictive controller (NMPC), ensuring the USV corresponds with the reference path and smoothen the motion under constrained dynamics. Simulations and comparisons in various scenarios demonstrated the effectiveness and superiority of the proposed scheme.
{"title":"Global path planning and waypoint following for heterogeneous unmanned surface vehicles assisting inland water monitoring","authors":"Liang Zhao , Yong Bai , Jeom Kee Paik","doi":"10.1016/j.joes.2023.07.002","DOIUrl":"10.1016/j.joes.2023.07.002","url":null,"abstract":"<div><div>The idea of dispatching multiple unmanned surface vehicles (USVs) to undertake marine missions has ignited a burgeoning enthusiasm on a global scale. Embarking on a quest to facilitate inland water monitoring, this paper presents a systematical approach concerning global path planning and path following for heterogeneous USVs. Specifically, by capturing the heterogeneous nature, an extended multiple travelling salesman problem (EMTSP) model, which seamlessly bridges the gap between various disparate constraints and optimization objectives, is formulated for the first time. Then, a novel Greedy Partheno Genetic Algorithm (GPGA) is devised to consistently address the problem from two aspects: (1) Incorporating the greedy randomized initialization and local exploration strategy, GPGA merits strong global and local searching ability, providing high-quality solutions for EMTSP. (2) A novel mutation strategy which not only inherits all advantages of PGA but also maintains the best individual in the offspring is devised, contributing to the local escaping efficiently. Finally, to track the waypoint permutations generated by GPGA, control input is generated by the nonlinear model predictive controller (NMPC), ensuring the USV corresponds with the reference path and smoothen the motion under constrained dynamics. Simulations and comparisons in various scenarios demonstrated the effectiveness and superiority of the proposed scheme.</div></div>","PeriodicalId":48514,"journal":{"name":"Journal of Ocean Engineering and Science","volume":"10 1","pages":"Pages 88-108"},"PeriodicalIF":13.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46551015","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.joes.2022.08.004
Ling Liu , Yu Yang , Tao Peng
This study uses a machine learning technique based on the Reservoir Computing (RC) model to predict the surge, sway, heave, roll, pitch, and yaw (6-DOF) motions of the KVLCC2 ship in an irregular wave environment. The trained RC model can predict the 6-DOF motions and give the predicted length of 2–5 wave cycles ahead with good accuracy. This work shows the strong ability of machine learning to predict vessel wave-excited motions. It implies that machine learning has important guiding significance in real-time forecasting for motions of both manned and unmanned ships.
{"title":"Machine learning prediction of 6-DOF motions of KVLCC2 ship based on RC model","authors":"Ling Liu , Yu Yang , Tao Peng","doi":"10.1016/j.joes.2022.08.004","DOIUrl":"10.1016/j.joes.2022.08.004","url":null,"abstract":"<div><div>This study uses a machine learning technique based on the Reservoir Computing (RC) model to predict the surge, sway, heave, roll, pitch, and yaw (6-DOF) motions of the KVLCC2 ship in an irregular wave environment. The trained RC model can predict the 6-DOF motions and give the predicted length of 2–5 wave cycles ahead with good accuracy. This work shows the strong ability of machine learning to predict vessel wave-excited motions. It implies that machine learning has important guiding significance in real-time forecasting for motions of both manned and unmanned ships.</div></div>","PeriodicalId":48514,"journal":{"name":"Journal of Ocean Engineering and Science","volume":"10 1","pages":"Pages 22-28"},"PeriodicalIF":13.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47455643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-22DOI: 10.1016/j.joes.2024.12.004
Jianmei Chen , Zhe Chen , Qiang Ma , Yuqing Zhang , Yanping He
Polar Carriers operate in both open water and brash ice areas, where differing navigation environments impose varying requirements on hull form design. Determining the proportion of these navigation areas is crucial for achieving a balanced hull form that optimizes both open water performance and ice-going capabilities. This paper proposes a Navigation State Recognition Model (NSRM) that utilizes GPS data from ship tracks to distinguish between different navigation states, allowing for an assessment of the proportion of open water and brash ice encountered during voyages. Based on the NSRM, a rapid hull form optimization method is developed for polar ships, aiming to minimize total resistance across both open water and brash ice areas. The total resistance is calculated using a weighted sum of the resistances in ice-covered and open-water sections of the route, as determined by the NSRM. The Rankine source and Reynolds-Averaged Navier-Stokes (RANS) methods are employed to calculate open-water resistance, while Juva and Riskas formula is used to estimate ice resistance in brash ice conditions. Additionally, the optimization method is applied to a parent ship with an invisible bulbous bow, resulting in an optimized bow hull form. This demonstrates the applicability of the NSRM-based optimization method for the design of Polar Carrier hull forms.
极地航母可以在开阔水域和浮冰区域运行，不同的航行环境对船体形状设计提出了不同的要求。确定这些导航区域的比例对于实现平衡的船体形状至关重要，从而优化开放水域性能和冰上能力。本文提出了一种导航状态识别模型（NSRM），该模型利用来自船舶轨迹的GPS数据来区分不同的导航状态，从而可以评估航行中遇到的开阔水域和浮冰的比例。在此基础上，提出了一种用于极地船舶的船体形状快速优化方法，旨在使开放水域和浮冰区域的总阻力最小。总阻力是根据NSRM确定的路线冰雪覆盖部分和开放水域部分阻力的加权和来计算的。开放水域阻力计算采用Rankine源法和reynolds - average Navier-Stokes （RANS）法，浮冰条件下冰阻力计算采用Juva和Riskas公式。此外，将该优化方法应用于具有隐形球首的母船，得到了最优的船首船体形状。这证明了基于nsrm的优化方法在极地航母船型设计中的适用性。
{"title":"Hull form optimization for polar carrier based on navigation state recognition model","authors":"Jianmei Chen , Zhe Chen , Qiang Ma , Yuqing Zhang , Yanping He","doi":"10.1016/j.joes.2024.12.004","DOIUrl":"10.1016/j.joes.2024.12.004","url":null,"abstract":"<div><div>Polar Carriers operate in both open water and brash ice areas, where differing navigation environments impose varying requirements on hull form design. Determining the proportion of these navigation areas is crucial for achieving a balanced hull form that optimizes both open water performance and ice-going capabilities. This paper proposes a Navigation State Recognition Model (NSRM) that utilizes GPS data from ship tracks to distinguish between different navigation states, allowing for an assessment of the proportion of open water and brash ice encountered during voyages. Based on the NSRM, a rapid hull form optimization method is developed for polar ships, aiming to minimize total resistance across both open water and brash ice areas. The total resistance is calculated using a weighted sum of the resistances in ice-covered and open-water sections of the route, as determined by the NSRM. The Rankine source and Reynolds-Averaged Navier-Stokes (RANS) methods are employed to calculate open-water resistance, while Juva and Riskas formula is used to estimate ice resistance in brash ice conditions. Additionally, the optimization method is applied to a parent ship with an invisible bulbous bow, resulting in an optimized bow hull form. This demonstrates the applicability of the NSRM-based optimization method for the design of Polar Carrier hull forms.</div></div>","PeriodicalId":48514,"journal":{"name":"Journal of Ocean Engineering and Science","volume":"10 5","pages":"Pages 819-829"},"PeriodicalIF":11.8,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145050470","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-14DOI: 10.1016/j.joes.2024.12.002
Bing Li, Jun Fan, Bin Wang, Kaiqi Zhao, Liwen Tan
This study investigates the scattering characteristics of a buried elastic sphere under plane wave subcritical incidence at low-frequency. As the penetrating wave in sediment at subcritical angles transitions to an evanescent wave, it decays along the depth. The scattering separation method is utilized to explore the form function of a polymethyl methacrylate (PMMA) sphere and the multiple scattering effects between the sphere and the interface under evanescent wave incidence. Additionally, a Ray approach is utilized to predict the far-field scattering from the buried PMMA sphere, which is verified using experimental results. The findings reveal that the evanescent wave field in the sediment exhibits spatially limited beam characteristics and low-pass filtering features. At low frequencies, echoes from the PMMA sphere are primarily contributed by Rayleigh waves. Furthermore, under evanescent wave incidence, the interference between clockwise and counterclockwise Rayleigh waves in the bistatic scattering of the PMMA sphere weakens, and the Specular-Rayleigh wave interference pattern becomes prominent, replacing the typical “X-shaped” distribution of the impulse response with a “backslash-like shaped” distribution in the time-angular domain. The smoothed Wigner-Ville distribution (SWVD) analysis of the echo signals indicates that the group velocity of lower frequency Rayleigh waves is biased higher, leading to a faster arrival of low-frequency components. This research may provide a valuable reference for detecting artificial targets at low-frequency and long distances.
{"title":"Subcritical scattering from buried elastic sphere based on subsonic Rayleigh waves","authors":"Bing Li, Jun Fan, Bin Wang, Kaiqi Zhao, Liwen Tan","doi":"10.1016/j.joes.2024.12.002","DOIUrl":"10.1016/j.joes.2024.12.002","url":null,"abstract":"<div><div>This study investigates the scattering characteristics of a buried elastic sphere under plane wave subcritical incidence at low-frequency. As the penetrating wave in sediment at subcritical angles transitions to an evanescent wave, it decays along the depth. The scattering separation method is utilized to explore the form function of a polymethyl methacrylate (PMMA) sphere and the multiple scattering effects between the sphere and the interface under evanescent wave incidence. Additionally, a Ray approach is utilized to predict the far-field scattering from the buried PMMA sphere, which is verified using experimental results. The findings reveal that the evanescent wave field in the sediment exhibits spatially limited beam characteristics and low-pass filtering features. At low frequencies, echoes from the PMMA sphere are primarily contributed by Rayleigh waves. Furthermore, under evanescent wave incidence, the interference between clockwise and counterclockwise Rayleigh waves in the bistatic scattering of the PMMA sphere weakens, and the Specular-Rayleigh wave interference pattern becomes prominent, replacing the typical “X-shaped” distribution of the impulse response with a “backslash-like shaped” distribution in the time-angular domain. The smoothed Wigner-Ville distribution (SWVD) analysis of the echo signals indicates that the group velocity of lower frequency Rayleigh waves is biased higher, leading to a faster arrival of low-frequency components. This research may provide a valuable reference for detecting artificial targets at low-frequency and long distances.</div></div>","PeriodicalId":48514,"journal":{"name":"Journal of Ocean Engineering and Science","volume":"10 5","pages":"Pages 761-773"},"PeriodicalIF":11.8,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145046735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-14DOI: 10.1016/j.joes.2024.11.003
Dongrong Zhou , Yiting Wang , Shangzhe Xin , Lei Wang , Tong Ge
In this paper, the dynamic response characteristics of an ancient shipwreck “ChangJiangKou II” salvaging system during its salvaging operation, including off-bottom, lifting and off-surface stage, are numerically and experimentally investigated. In order to accurately predict the hydrodynamic performance of “ChangJiangKou II” and the crane barge during the salvaging operation, a specific designed coupled time-domain model combining wreck-soil interaction, lifting module and mooring module is established. A physical model-scale experiment for dynamic lifting of an underwater structure is performed to validate the coupled numerical model. The performance of the dynamic lifting process in different lifting speeds and different environmental conditions is analysed and discussed. The experimental results indicate that there is a tension distribution process during the lifting operation and an external disturbance to the shipwreck can lead to a large increase in lifting cable tensions.
{"title":"The dynamic response characteristics of “ChangJiangKou II” shipwreck salvaging operation: Physical and numerical experiments","authors":"Dongrong Zhou , Yiting Wang , Shangzhe Xin , Lei Wang , Tong Ge","doi":"10.1016/j.joes.2024.11.003","DOIUrl":"10.1016/j.joes.2024.11.003","url":null,"abstract":"<div><div>In this paper, the dynamic response characteristics of an ancient shipwreck “ChangJiangKou II” salvaging system during its salvaging operation, including off-bottom, lifting and off-surface stage, are numerically and experimentally investigated. In order to accurately predict the hydrodynamic performance of “ChangJiangKou II” and the crane barge during the salvaging operation, a specific designed coupled time-domain model combining wreck-soil interaction, lifting module and mooring module is established. A physical model-scale experiment for dynamic lifting of an underwater structure is performed to validate the coupled numerical model. The performance of the dynamic lifting process in different lifting speeds and different environmental conditions is analysed and discussed. The experimental results indicate that there is a tension distribution process during the lifting operation and an external disturbance to the shipwreck can lead to a large increase in lifting cable tensions.</div></div>","PeriodicalId":48514,"journal":{"name":"Journal of Ocean Engineering and Science","volume":"10 5","pages":"Pages 788-799"},"PeriodicalIF":11.8,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145046733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-13DOI: 10.1016/j.joes.2025.01.002
Peng Jiang, Yichen Huang, Yong Cao, Shijun Liao, Bin Xie
The objective of this work is to investigate the utility and effectiveness of the high-order scheme for simulating unsteady turbulent flows. To achieve it, the studies are conducted from two perspectives: (i) the ability of different numerical schemes to accurately simulate turbulence problems using the same set of meshes; and (ii) the accuracy and stability of higher-order schemes for solving turbulence statistics for different mesh types (hexahedral, tetrahedral, and polyhedral cells). The simulations employ the third-order scheme for spatial discretization of the governing equations, while a widely-used second-order solver, namely pisoFoam, is employed for comparison. This study considers the canonical cases of the two-dimensional Taylor-Green vortex (2D TGV) problem at and flow past a sphere at to address the aforementioned two key issues. For the TGV case, the high-order model significantly improves the numerical accuracy with convergence rates and reduces the numerical dissipation of nearly 1/10 of pisoFoam on different meshing types. In the latter case, the high-order scheme with large-eddy simulation (LES) accurately predicts the vortex structures and the flow instability, regardless of grid type. However, pisoFoam is found to be sensitive to mesh types, which results in numerous non-physical structures in the flow field due to numerical noise rather than flow physics, particularly for tetrahedral cells. Furthermore, for the typical low- and high-order flow statistics, the numerical results predicted by the present model show better agreement with the reference data and have less dependence on the type of grids compared with the conventional scheme. In addition, the obtained energy spectrum by the high-order solver accurately captures the Kelvin-Helmholtz (K-H) instability and the vortex shedding frequency, while these important features are less pronounced by the traditional low-order model.
{"title":"Utility of high-order scheme for unsteady flow simulations: Comparison with second-order tool","authors":"Peng Jiang, Yichen Huang, Yong Cao, Shijun Liao, Bin Xie","doi":"10.1016/j.joes.2025.01.002","DOIUrl":"10.1016/j.joes.2025.01.002","url":null,"abstract":"<div><div>The objective of this work is to investigate the utility and effectiveness of the high-order scheme for simulating unsteady turbulent flows. To achieve it, the studies are conducted from two perspectives: (i) the ability of different numerical schemes to accurately simulate turbulence problems using the same set of meshes; and (ii) the accuracy and stability of higher-order schemes for solving turbulence statistics for different mesh types (hexahedral, tetrahedral, and polyhedral cells). The simulations employ the third-order scheme for spatial discretization of the governing equations, while a widely-used second-order solver, namely pisoFoam, is employed for comparison. This study considers the canonical cases of the two-dimensional Taylor-Green vortex (2D TGV) problem at <span><math><mrow><mi>R</mi><mi>e</mi><mo>=</mo><mn>100</mn><mo>,</mo><mspace></mspace><mn>1600</mn></mrow></math></span> and flow past a sphere at <span><math><mrow><mi>R</mi><mi>e</mi><mo>=</mo><mn>10</mn><mspace></mspace><mn>000</mn></mrow></math></span> to address the aforementioned two key issues. For the TGV case, the high-order model significantly improves the numerical accuracy with convergence rates and reduces the numerical dissipation of nearly 1/10 of pisoFoam on different meshing types. In the latter case, the high-order scheme with large-eddy simulation (LES) accurately predicts the vortex structures and the flow instability, regardless of grid type. However, pisoFoam is found to be sensitive to mesh types, which results in numerous non-physical structures in the flow field due to numerical noise rather than flow physics, particularly for tetrahedral cells. Furthermore, for the typical low- and high-order flow statistics, the numerical results predicted by the present model show better agreement with the reference data and have less dependence on the type of grids compared with the conventional scheme. In addition, the obtained energy spectrum by the high-order solver accurately captures the Kelvin-Helmholtz (K-H) instability and the vortex shedding frequency, while these important features are less pronounced by the traditional low-order model.</div></div>","PeriodicalId":48514,"journal":{"name":"Journal of Ocean Engineering and Science","volume":"10 5","pages":"Pages 774-787"},"PeriodicalIF":11.8,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145046734","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-13DOI: 10.1016/j.joes.2024.12.001
Susana Costa , Tiago C.A. Oliveira , Ali Abdolali
Wind-wave steepness along the North Atlantic (27.46 N < lat < 43.53 N and 62.03 W < lon < 80.19 W) is characterized based on at most 37 years (1984 to 2020) of buoy measurements. Wave data from 16 National Data Buoy Center (NDBC) and 2 Marine Environmental Data Section (MEDS) stations located at depths ranging from 33 m to 5394 m are used. Intra-annual variability of the full spectrum wave steepness (sm) and the wind-sea steepness (smw) are analyzed. Among the 18 locations, the average sm and smw ranged between 0.023 to 0.037 and 0.025 to 0.039, respectively. Results show similar intra-annual variability among the different buoys both for sm and for smw with monthly average maximums occurring between January and February (0.029 < sm < 0.045, 0.030 < smw < 0.048) and minimums between July and August (0.018<sm<0.033, 0.019 < smw < 0.035). The probability distribution function of sm/smw presents a peak between 0.9 and 1.0 for all stations. It is also found that the sea states with the maximum sm and smw are not directly linked to the maximum events of significant wave height. Practically, these findings can inform the implementation of various ocean engineering endeavors as well as navigation risk determination, as wave steepness exerts a significant influence on several physical processes in the marine environment.
{"title":"Wind-wave steepness offshore the North American east coast","authors":"Susana Costa , Tiago C.A. Oliveira , Ali Abdolali","doi":"10.1016/j.joes.2024.12.001","DOIUrl":"10.1016/j.joes.2024.12.001","url":null,"abstract":"<div><div>Wind-wave steepness along the North Atlantic (27.46 N < lat < 43.53 N and 62.03 W < lon < 80.19 W) is characterized based on at most 37 years (1984 to 2020) of buoy measurements. Wave data from 16 National Data Buoy Center (NDBC) and 2 Marine Environmental Data Section (MEDS) stations located at depths ranging from 33 m to 5394 m are used. Intra-annual variability of the full spectrum wave steepness (<em>s</em><sub>m</sub>) and the wind-sea steepness (<em>s</em><sub>mw</sub>) are analyzed. Among the 18 locations, the average <em>s</em><sub>m</sub> and <em>s</em><sub>mw</sub> ranged between 0.023 to 0.037 and 0.025 to 0.039, respectively. Results show similar intra-annual variability among the different buoys both for <em>s</em><sub>m</sub> and for <em>s</em><sub>mw</sub> with monthly average maximums occurring between January and February (0.029 < <em>s</em><sub>m</sub> < 0.045, 0.030 < <em>s</em><sub>mw</sub> < 0.048) and minimums between July and August (0.018<<em>s</em><sub>m</sub><0.033, 0.019 < <em>s</em><sub>mw</sub> < 0.035). The probability distribution function of <em>s</em><sub>m</sub>/<em>s</em><sub>mw</sub> presents a peak between 0.9 and 1.0 for all stations. It is also found that the sea states with the maximum <em>s</em><sub>m</sub> and <em>s</em><sub>mw</sub> are not directly linked to the maximum events of significant wave height. Practically, these findings can inform the implementation of various ocean engineering endeavors as well as navigation risk determination, as wave steepness exerts a significant influence on several physical processes in the marine environment.</div></div>","PeriodicalId":48514,"journal":{"name":"Journal of Ocean Engineering and Science","volume":"10 5","pages":"Pages 745-760"},"PeriodicalIF":11.8,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145046743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The wave run-up along the column surface is one of the focal issues of research in ocean engineering. This experimental study aimed to reveal the wave run-up characteristics of a fixed four-square-column array with rounded corners under focused waves by controlling wave steepness, spectral peak period, wave direction, and focus position. The experiment utilized a 1:50 scale physical model, with focused waves generated in a wave tank to simulate extreme sea conditions. Four squared columns were fixed to the tank carriage. Eighteen wave probes were installed around the fore and rear columns to measure wave run-ups. The results indicated that with an increase in wave steepness, the wave run-up ratio demonstrates an increasing trend, particularly when the waves approach or precisely break at the focal point. Furthermore, the wave run-up ratio on the front column decreases as the spectral peak period increases, owing to the weakening of the nonlinear wave-column interaction when the wavelength is significantly larger than the column width. For the rear column, the dissipation of wave energy by the front column leads to a notably lower wave run-up ratio. However, under the influence of incident focused waves at certain wavelengths, the rear column may experience a more intense secondary run-up phenomenon. Additionally, comparative analysis of different focus positions revealed that the wave run-up ratio is maximized when the focus position is located behind the front column. The incident waves at 45° were diffracted by the rounded corners of the columns, leading to the dispersion of wave energy and consequently yielding a reduced wave run-up ratio. The experimental data obtained serve as crucial benchmarks for validating further numerical simulations of wave impact on rounded square columns.
{"title":"An experimental study on wave run-ups of fixed four-rounded-square-column array in focused waves","authors":"Meng Shan , Longfei Xiao , Wencheng Wu , Yufeng Kou , Kelu Li","doi":"10.1016/j.joes.2024.12.003","DOIUrl":"10.1016/j.joes.2024.12.003","url":null,"abstract":"<div><div>The wave run-up along the column surface is one of the focal issues of research in ocean engineering. This experimental study aimed to reveal the wave run-up characteristics of a fixed four-square-column array with rounded corners under focused waves by controlling wave steepness, spectral peak period, wave direction, and focus position. The experiment utilized a 1:50 scale physical model, with focused waves generated in a wave tank to simulate extreme sea conditions. Four squared columns were fixed to the tank carriage. Eighteen wave probes were installed around the fore and rear columns to measure wave run-ups. The results indicated that with an increase in wave steepness, the wave run-up ratio demonstrates an increasing trend, particularly when the waves approach or precisely break at the focal point. Furthermore, the wave run-up ratio on the front column decreases as the spectral peak period increases, owing to the weakening of the nonlinear wave-column interaction when the wavelength is significantly larger than the column width. For the rear column, the dissipation of wave energy by the front column leads to a notably lower wave run-up ratio. However, under the influence of incident focused waves at certain wavelengths, the rear column may experience a more intense secondary run-up phenomenon. Additionally, comparative analysis of different focus positions revealed that the wave run-up ratio is maximized when the focus position is located behind the front column. The incident waves at 45° were diffracted by the rounded corners of the columns, leading to the dispersion of wave energy and consequently yielding a reduced wave run-up ratio. The experimental data obtained serve as crucial benchmarks for validating further numerical simulations of wave impact on rounded square columns.</div></div>","PeriodicalId":48514,"journal":{"name":"Journal of Ocean Engineering and Science","volume":"10 5","pages":"Pages 800-818"},"PeriodicalIF":11.8,"publicationDate":"2025-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145050469","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-11DOI: 10.1016/j.joes.2024.11.002
Chern Fong Lee, Sindre Fjermedal, Muk Chen Ong
For intermediate water depths (typically ranging from 50 m to 80 m), designing steel catenary mooring systems for floating marine renewable energy (FMRE) platforms can be challenging due to the limited weight of suspended mooring lines. This can substantially increase mooring line tensions following large platform offsets. In contrast, mooring systems using synthetic fibre ropes offer the potential to prevent large platform offsets while reducing peak mooring line tensions. In this study, novel semi-taut mooring systems incorporating polyester ropes and steel chains are proposed for a combined wind and wave energy system – the semi-submersible flap torus combination (STFC) concept, deployed at a 50 m water depth. The STFC integrates a semi-submersible floating offshore wind turbine (FOWT), a torus wave energy converter (WEC) and three flap-type WECs. The dynamic responses of the STFC with different semi-taut mooring configurations under operational and survival environmental conditions are assessed in terms of key performance parameters such as the platform's motion responses and mooring line tensions. These performance parameters are compared against those of a chain-catenary mooring system. With the use of semi-taut mooring systems, significantly smaller mooring footprints as compared to the chain-catenary mooring systems can be achieved. Moreover, it is demonstrated that the semi-taut mooring systems are effective in reducing the maximum tension of the mooring lines. A basic cost analysis further indicates that semi-taut mooring systems offer substantial cost advantages over chain-catenary moorings in intermediate water depths.
{"title":"Design and comparative analysis of mooring systems for a combined wind and wave energy system at intermediate water depth","authors":"Chern Fong Lee, Sindre Fjermedal, Muk Chen Ong","doi":"10.1016/j.joes.2024.11.002","DOIUrl":"10.1016/j.joes.2024.11.002","url":null,"abstract":"<div><div>For intermediate water depths (typically ranging from 50 m to 80 m), designing steel catenary mooring systems for floating marine renewable energy (FMRE) platforms can be challenging due to the limited weight of suspended mooring lines. This can substantially increase mooring line tensions following large platform offsets. In contrast, mooring systems using synthetic fibre ropes offer the potential to prevent large platform offsets while reducing peak mooring line tensions. In this study, novel semi-taut mooring systems incorporating polyester ropes and steel chains are proposed for a combined wind and wave energy system – the semi-submersible flap torus combination (STFC) concept, deployed at a 50 m water depth. The STFC integrates a semi-submersible floating offshore wind turbine (FOWT), a torus wave energy converter (WEC) and three flap-type WECs. The dynamic responses of the STFC with different semi-taut mooring configurations under operational and survival environmental conditions are assessed in terms of key performance parameters such as the platform's motion responses and mooring line tensions. These performance parameters are compared against those of a chain-catenary mooring system. With the use of semi-taut mooring systems, significantly smaller mooring footprints as compared to the chain-catenary mooring systems can be achieved. Moreover, it is demonstrated that the semi-taut mooring systems are effective in reducing the maximum tension of the mooring lines. A basic cost analysis further indicates that semi-taut mooring systems offer substantial cost advantages over chain-catenary moorings in intermediate water depths.</div></div>","PeriodicalId":48514,"journal":{"name":"Journal of Ocean Engineering and Science","volume":"10 4","pages":"Pages 492-508"},"PeriodicalIF":13.0,"publicationDate":"2025-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144704737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-16DOI: 10.1016/j.joes.2024.11.001
Zhiyao Li , Yiming Zhu , Yiting Wang , Yong Zhang , Lei Wang
To solve the path following problem in navigation tasks for under-actuated autonomous surface vehicles (ASVs), this paper proposed a path following control method which combines trajectory dataset of random ship motion and offline reinforcement learning (RM-ORL). The method does not require the reinforcement learning (RL) agent to interact with the environment while training the policy, and it can obtain training datasets with a lower cost. In RM-ORL, the irregular motion data of the ASV in open water is first collected. Then the desired path is reconstructed using the B-spline function and the path points along the motion trajectories. Thus the offline dataset will be enhanced with the motion data and the new path. Finally, the conservative Q-learning algorithm is utilized to train the path following controller. The path deviation in simulation maps, rudder data and ship motion parameters of RM-ORL, online RL and other offline RL policies trained on different datasets are compared. The simulation results illustrate that the RM-ORL achieves comparable path following accuracy to that of online RL agent and offline RL agent trained on expert data, while surpassing the one trained on online agent replay buffer data. The rudder steering amplitude of RM-ORL is also smaller than that of other policies, which verifies the effectiveness of our method applied to the path following control of under-actuated ASV.
{"title":"Path following control of under-actuated autonomous surface vehicle based on random motion trajectory dataset and offline reinforcement learning","authors":"Zhiyao Li , Yiming Zhu , Yiting Wang , Yong Zhang , Lei Wang","doi":"10.1016/j.joes.2024.11.001","DOIUrl":"10.1016/j.joes.2024.11.001","url":null,"abstract":"<div><div>To solve the path following problem in navigation tasks for under-actuated autonomous surface vehicles (ASVs), this paper proposed a path following control method which combines trajectory dataset of random ship motion and offline reinforcement learning (RM-ORL). The method does not require the reinforcement learning (RL) agent to interact with the environment while training the policy, and it can obtain training datasets with a lower cost. In RM-ORL, the irregular motion data of the ASV in open water is first collected. Then the desired path is reconstructed using the B-spline function and the path points along the motion trajectories. Thus the offline dataset will be enhanced with the motion data and the new path. Finally, the conservative Q-learning algorithm is utilized to train the path following controller. The path deviation in simulation maps, rudder data and ship motion parameters of RM-ORL, online RL and other offline RL policies trained on different datasets are compared. The simulation results illustrate that the RM-ORL achieves comparable path following accuracy to that of online RL agent and offline RL agent trained on expert data, while surpassing the one trained on online agent replay buffer data. The rudder steering amplitude of RM-ORL is also smaller than that of other policies, which verifies the effectiveness of our method applied to the path following control of under-actuated ASV.</div></div>","PeriodicalId":48514,"journal":{"name":"Journal of Ocean Engineering and Science","volume":"10 5","pages":"Pages 724-744"},"PeriodicalIF":11.8,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145046742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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