Ocean Engineering最新文献

Numerical study on wave–wind coupling effects on hydrodynamics and light capture performance of offshore multi-body floating photovoltaic system

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-08 DOI: 10.1016/j.oceaneng.2025.120593

Jia Fu , Yun-Peng Zhao , Guang-Chen Jia , Chao Ma , Jia-Qing Shu , Yan-Qian Sun

Offshore floating photovoltaic (FPV) systems have the potential to become important clean energy sources. However, the behavior of multi-body FPV under coupled wave–wind conditions are not fully understood. In this study, the hydrodynamics and light capture performance of FPV systems in coupled wave–wind co-directional conditions were numerically assessed by considering three different panel arrangements. This study utilized potential flow theory to conduct wave simulations and used Morison force to calculate the wind effect on the structure. The wind coefficient variation with pitch is innovatively considered in the present numerical method. The hydrodynamic results were compared with wave-only conditions to understand the effects of wind–wave coupling better. It was observed that wind has a significant effect on the surge motions of FPV systems in low-frequency waves. Compared with a pure wave condition, the average position in the vertical direction of the structure in a parallel arrangement sinks by about 12.4% owing to the vertical component of the wind load on the photovoltaic panel, while exhibiting a float rise in staggered and symmetrical arrangements. The coupling of wave–wind loads cause a sharp increase in both the mooring force and the horizontal connection forces at low frequencies. The insolation in the parallel arrangement was 13% greater than that in the staggered and symmetrical arrangements under the same conditions.

{"title":"Numerical study on wave–wind coupling effects on hydrodynamics and light capture performance of offshore multi-body floating photovoltaic system","authors":"Jia Fu , Yun-Peng Zhao , Guang-Chen Jia , Chao Ma , Jia-Qing Shu , Yan-Qian Sun","doi":"10.1016/j.oceaneng.2025.120593","DOIUrl":"10.1016/j.oceaneng.2025.120593","url":null,"abstract":"<div><div>Offshore floating photovoltaic (FPV) systems have the potential to become important clean energy sources. However, the behavior of multi-body FPV under coupled wave–wind conditions are not fully understood. In this study, the hydrodynamics and light capture performance of FPV systems in coupled wave–wind co-directional conditions were numerically assessed by considering three different panel arrangements. This study utilized potential flow theory to conduct wave simulations and used Morison force to calculate the wind effect on the structure. The wind coefficient variation with pitch is innovatively considered in the present numerical method. The hydrodynamic results were compared with wave-only conditions to understand the effects of wind–wave coupling better. It was observed that wind has a significant effect on the surge motions of FPV systems in low-frequency waves. Compared with a pure wave condition, the average position in the vertical direction of the structure in a parallel arrangement sinks by about 12.4% owing to the vertical component of the wind load on the photovoltaic panel, while exhibiting a float rise in staggered and symmetrical arrangements. The coupling of wave–wind loads cause a sharp increase in both the mooring force and the horizontal connection forces at low frequencies. The insolation in the parallel arrangement was 13% greater than that in the staggered and symmetrical arrangements under the same conditions.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"323 ","pages":"Article 120593"},"PeriodicalIF":4.6,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143350744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Numerical study on the dynamic RPT behavior of the damaged LPG carrier with combined CFD and VOF boiling model

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-08 DOI: 10.1016/j.oceaneng.2025.120546

XinLong Zhang , Li Lin , YiHua Su , Shan Ma , Gang Wang , Simone Mancini

Reasonable evaluation of RTP (Rapid Phase Transition) characteristics in the damage leakage scenario is a significant consideration in the ship design and risk control of LPG (Liquefied Petroleum Gas) carriers. This paper proposes a numerical method to realize the natural leakage of LPG. CFD (Computational Fluid Dynamics) module is used to govern the mixed flow of multiphase fluids and solve motion response of the damage ship, while VOF (Volume of Fluid) boiling module is used to simulate RPT mechanism and deal with the multiphase interaction. Especially, UDF (User-Defined Function) is a key to perform the initial distribution of multiphase fluids and multiple physical field properties. To verify the accuracy of the numerical method on dealing with RPT, this paper performs the reliability analysis based on the experimental study of the liquid nitrogen injecting into water. By analyzing four leakage scenarios, main findings is divided into two aspects. Firstly, to truly assess the RPT behavior, the equivalent opening should consider the location and shape of the potential opening. Secondly, the cryogenic environment in the secondary barrier only occurs in a limited time and space. Overall, obtained results can provide valuable reference for the regulation revision and the ship design.

{"title":"Numerical study on the dynamic RPT behavior of the damaged LPG carrier with combined CFD and VOF boiling model","authors":"XinLong Zhang , Li Lin , YiHua Su , Shan Ma , Gang Wang , Simone Mancini","doi":"10.1016/j.oceaneng.2025.120546","DOIUrl":"10.1016/j.oceaneng.2025.120546","url":null,"abstract":"<div><div>Reasonable evaluation of RTP (Rapid Phase Transition) characteristics in the damage leakage scenario is a significant consideration in the ship design and risk control of LPG (Liquefied Petroleum Gas) carriers. This paper proposes a numerical method to realize the natural leakage of LPG. CFD (Computational Fluid Dynamics) module is used to govern the mixed flow of multiphase fluids and solve motion response of the damage ship, while VOF (Volume of Fluid) boiling module is used to simulate RPT mechanism and deal with the multiphase interaction. Especially, UDF (User-Defined Function) is a key to perform the initial distribution of multiphase fluids and multiple physical field properties. To verify the accuracy of the numerical method on dealing with RPT, this paper performs the reliability analysis based on the experimental study of the liquid nitrogen injecting into water. By analyzing four leakage scenarios, main findings is divided into two aspects. Firstly, to truly assess the RPT behavior, the equivalent opening should consider the location and shape of the potential opening. Secondly, the cryogenic environment in the secondary barrier only occurs in a limited time and space. Overall, obtained results can provide valuable reference for the regulation revision and the ship design.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"323 ","pages":"Article 120546"},"PeriodicalIF":4.6,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143351148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Model predictive controller based design for energy optimization of the hybrid shipboard microgrids

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-08 DOI: 10.1016/j.oceaneng.2025.120545

Farooq Alam , Sajjad Haider Zaidi , Arsalan Rehmat , Bilal M. Khan

Nowadays, the need for hybrid Shipboard Microgrid (SMG) optimization, integration, and control is rising constantly. This paper provides an optimal hierarchical control scheme for integrating microgrid systems comprising AC and DC electrical distribution networks for a shipboard architecture. Utilizing this power by the inverter can result in rapid spikes in the AC/DC voltages, potentially reducing the overall performance of the hybrid microgrid. The proposed Model Predictive Control (MPC) based controller shows better performances in the reduction of transient droops of the AC/DC voltages and handling parametric changes, load variations, and grid transitions. We provided the analytical solution for implementing proposed optimal design of hierarchical control for a multi-DG and renewable energy resources (RESs) integration-based shipboard microgrid. The performance of pproportional integral (PI), Sliding Mode Controller (SMC), and MPC based optimal hierarchical control designs are compared through simulation test cases with various static and dynamic load conditions, both for AC and DC-type loads. Furthermore, we extended our analysis to include multiple distribution generator (DG) and RES involvements in the system to demonstrate the enhanced performance of our design against parametric variations and undesirable faulty load conditions. Additionally, the architecture incorporates multiple DG and RES to enhance system scalability and flexibility. Simulation results validated in MATLAB/Simulink show improved energy optimization and resilience across various static and dynamic load conditions. Practical hardware implementation using the NVIDIA Jetson Nano further confirms the real-time applicability of the control strategies.

{"title":"Model predictive controller based design for energy optimization of the hybrid shipboard microgrids","authors":"Farooq Alam , Sajjad Haider Zaidi , Arsalan Rehmat , Bilal M. Khan","doi":"10.1016/j.oceaneng.2025.120545","DOIUrl":"10.1016/j.oceaneng.2025.120545","url":null,"abstract":"<div><div>Nowadays, the need for hybrid Shipboard Microgrid (SMG) optimization, integration, and control is rising constantly. This paper provides an optimal hierarchical control scheme for integrating microgrid systems comprising AC and DC electrical distribution networks for a shipboard architecture. Utilizing this power by the inverter can result in rapid spikes in the AC/DC voltages, potentially reducing the overall performance of the hybrid microgrid. The proposed Model Predictive Control (MPC) based controller shows better performances in the reduction of transient droops of the AC/DC voltages and handling parametric changes, load variations, and grid transitions. We provided the analytical solution for implementing proposed optimal design of hierarchical control for a multi-DG and renewable energy resources (RESs) integration-based shipboard microgrid. The performance of pproportional integral (PI), Sliding Mode Controller (SMC), and MPC based optimal hierarchical control designs are compared through simulation test cases with various static and dynamic load conditions, both for AC and DC-type loads. Furthermore, we extended our analysis to include multiple distribution generator (DG) and RES involvements in the system to demonstrate the enhanced performance of our design against parametric variations and undesirable faulty load conditions. Additionally, the architecture incorporates multiple DG and RES to enhance system scalability and flexibility. Simulation results validated in MATLAB/Simulink show improved energy optimization and resilience across various static and dynamic load conditions. Practical hardware implementation using the NVIDIA Jetson Nano further confirms the real-time applicability of the control strategies.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"323 ","pages":"Article 120545"},"PeriodicalIF":4.6,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143350742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Investigation on wave attenuation characteristics and mechanism of oyster castles under regular waves

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-08 DOI: 10.1016/j.oceaneng.2025.120617

Aifeng Tao , Jianhao Liu , Wei Xu , Jian Zeng , Jun Fan , Rongyuan Wang , Jinhai Zheng

Oyster reefs protect coastal areas by reducing wave intensity and erosion, and their hydrodynamic behavior deserves further study. This paper delves into the wave attenuation characteristics and mechanism of oyster castles under regular waves through a combination of experimental and numerical approaches. The effects of relative reef submergence d_s/H_i, relative crest width B/H_i, and oyster density ρ₀ on wave attenuation are analyzed, the spatial variation of flow field and turbulent kinetic energy around oyster castles are investigated, and the wave attenuation mechanism are revealed. Overall, the transmission coefficient increased nonlinearly with growing relative reef submergence. When 1.0≤d_s/H_i ≤ 2.0, the effects of relative crest width and oyster density on the transmission coefficient are significant, and the transmission coefficient decreases with the enlarge of relative crest width or oyster density. When d_s/H_i = 1.0 and B/H_i = 5.0, the transmission coefficient of ρ₀ = 600 ind/m² decreases by about 13% in contrast to ρ₀ = 0 ind/m². In terms of wave attenuation mechanism, wave breaking and frictional dissipation dominate the wave attenuation when d_s/H_i = 1.0. When 2.0≤d_s/H_i ≤ 4.0, frictional dissipation dominates, and it steadily decreases with the extend of relative reef submergence. The findings could be instrumental for evaluating the disaster mitigation potential of oyster castles.

{"title":"Investigation on wave attenuation characteristics and mechanism of oyster castles under regular waves","authors":"Aifeng Tao , Jianhao Liu , Wei Xu , Jian Zeng , Jun Fan , Rongyuan Wang , Jinhai Zheng","doi":"10.1016/j.oceaneng.2025.120617","DOIUrl":"10.1016/j.oceaneng.2025.120617","url":null,"abstract":"<div><div>Oyster reefs protect coastal areas by reducing wave intensity and erosion, and their hydrodynamic behavior deserves further study. This paper delves into the wave attenuation characteristics and mechanism of oyster castles under regular waves through a combination of experimental and numerical approaches. The effects of relative reef submergence <em>d</em><sub>s</sub>/<em>H</em><sub>i</sub>, relative crest width <em>B</em>/<em>H</em><sub>i</sub>, and oyster density <em>ρ</em><sub>0</sub> on wave attenuation are analyzed, the spatial variation of flow field and turbulent kinetic energy around oyster castles are investigated, and the wave attenuation mechanism are revealed. Overall, the transmission coefficient increased nonlinearly with growing relative reef submergence. When 1.0≤<em>d</em><sub>s</sub>/<em>H</em><sub>i</sub> ≤ 2.0, the effects of relative crest width and oyster density on the transmission coefficient are significant, and the transmission coefficient decreases with the enlarge of relative crest width or oyster density. When <em>d</em><sub>s</sub>/<em>H</em><sub>i</sub> = 1.0 and <em>B</em>/<em>H</em><sub>i</sub> = 5.0, the transmission coefficient of <em>ρ</em><sub>0</sub> = 600 ind/m<sup>2</sup> decreases by about 13% in contrast to <em>ρ</em><sub>0</sub> = 0 ind/m<sup>2</sup>. In terms of wave attenuation mechanism, wave breaking and frictional dissipation dominate the wave attenuation when <em>d</em><sub>s</sub>/<em>H</em><sub>i</sub> = 1.0. When 2.0≤<em>d</em><sub>s</sub>/<em>H</em><sub>i</sub> ≤ 4.0, frictional dissipation dominates, and it steadily decreases with the extend of relative reef submergence. The findings could be instrumental for evaluating the disaster mitigation potential of oyster castles.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"323 ","pages":"Article 120617"},"PeriodicalIF":4.6,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143350743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Seismic vulnerability analysis of bridges incorporating scour uncertainty using a copula-based approach

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-08 DOI: 10.1016/j.oceaneng.2025.120598

Yongle Li , Hongyu Chen , Ming Yi , Jinrong Li , Chen Fang

Scour can significantly compromise bridge foundations and increase the possibility of failure during seismic events. Although the traditional cloud method is a commonly employed approach for assessing seismic resistance in bridges subjected to scour, it relies on empirical assumptions and inevitably introduces analytical errors. A copula-based approach was proposed for seismic vulnerability analysis by incorporating the uncertainty of scour depth into the assessment of bridge seismic performance. A bivariate copula function was employed to model the nonlinear dependencies between intensity measures (IM) and engineering demand parameters (EDP), thereby facilitating the construction of more accurate vulnerability curves without the restrictive assumption of a log-normal distribution. The uncertainty in scour depth was captured using the Latin Hypercube Sampling (LHS) technique. A case study of a four-span continuous beam bridge was conducted to demonstrate the effectiveness of the proposed framework. The results indicate that scour has a significant impact on piles compared to other components. Taking the slight damage state as an example, as the scour scenario progresses from slight to severe, the failure probability of the piers and bearings under an IM of 1.0g decreases by 0.17% and 0.11%, respectively. However, the vulnerability of the piles increases by 9.78 times.

{"title":"Seismic vulnerability analysis of bridges incorporating scour uncertainty using a copula-based approach","authors":"Yongle Li , Hongyu Chen , Ming Yi , Jinrong Li , Chen Fang","doi":"10.1016/j.oceaneng.2025.120598","DOIUrl":"10.1016/j.oceaneng.2025.120598","url":null,"abstract":"<div><div>Scour can significantly compromise bridge foundations and increase the possibility of failure during seismic events. Although the traditional cloud method is a commonly employed approach for assessing seismic resistance in bridges subjected to scour, it relies on empirical assumptions and inevitably introduces analytical errors. A copula-based approach was proposed for seismic vulnerability analysis by incorporating the uncertainty of scour depth into the assessment of bridge seismic performance. A bivariate copula function was employed to model the nonlinear dependencies between intensity measures (IM) and engineering demand parameters (EDP), thereby facilitating the construction of more accurate vulnerability curves without the restrictive assumption of a log-normal distribution. The uncertainty in scour depth was captured using the Latin Hypercube Sampling (LHS) technique. A case study of a four-span continuous beam bridge was conducted to demonstrate the effectiveness of the proposed framework. The results indicate that scour has a significant impact on piles compared to other components. Taking the slight damage state as an example, as the scour scenario progresses from slight to severe, the failure probability of the piers and bearings under an IM of 1.0g decreases by 0.17% and 0.11%, respectively. However, the vulnerability of the piles increases by 9.78 times.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"323 ","pages":"Article 120598"},"PeriodicalIF":4.6,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143349784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Behaviour of an offshore finned monopile located on a sloping ground surface: An innovative foundation solution

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-08 DOI: 10.1016/j.oceaneng.2025.120557

T. Jegadeesh Kumar, Deendayal Rathod, K.T. Krishnanunni

This study explores the performance of finned monopiles as an innovative foundation solution for Offshore Wind Turbines subjected to cyclic loading under varying seabed conditions. Traditional monopiles face challenges related to stability when installed on sloped terrains, which are common in offshore environments. To address this, the research investigates the effectiveness of rectangular fins attached along the monopile's length to improve lateral resistance and reduce accumulated rotation. Experimental and numerical analyses were conducted across different slope gradients (flat, 1V:5H, 1V:3H, 1V:2H), pile positions (0Dp, 2.5Dp, 5Dp, 7.5Dp), and soil densities (35%, 55%, 75%), applying cyclic loading at 0.25 Hz over 1000 cycles with lateral load amplitudes (ξ_b) of 30%, 40%, and 50%. This study is the first to investigate finned monopiles under cyclic loading on sloping seabed conditions, demonstrating a 30–60% improvement in lateral resistance by increasing the passive soil resistance by reducing the rotation compared to monopiles. This work addresses the challenges of Offshore Wind Turbine foundations in complex topographies. Numerical modeling using PLAXIS 3D closely aligned with experimental findings, confirming the effectiveness of finned monopiles in enhancing stability on sloped seabeds. These findings suggest that finned piles offer a robust foundation alternative for Offshore Wind Turbines, particularly in challenging environments with variable seabed topography.

{"title":"Behaviour of an offshore finned monopile located on a sloping ground surface: An innovative foundation solution","authors":"T. Jegadeesh Kumar, Deendayal Rathod, K.T. Krishnanunni","doi":"10.1016/j.oceaneng.2025.120557","DOIUrl":"10.1016/j.oceaneng.2025.120557","url":null,"abstract":"<div><div>This study explores the performance of finned monopiles as an innovative foundation solution for Offshore Wind Turbines subjected to cyclic loading under varying seabed conditions. Traditional monopiles face challenges related to stability when installed on sloped terrains, which are common in offshore environments. To address this, the research investigates the effectiveness of rectangular fins attached along the monopile's length to improve lateral resistance and reduce accumulated rotation. Experimental and numerical analyses were conducted across different slope gradients (flat, 1V:5H, 1V:3H, 1V:2H), pile positions (0<em>Dp</em>, 2.5<em>Dp</em>, 5<em>Dp</em>, 7.5<em>Dp</em>), and soil densities (35%, 55%, 75%), applying cyclic loading at 0.25 Hz over 1000 cycles with lateral load amplitudes (<em>ξ</em><sub><em>b</em></sub>) of 30%, 40%, and 50%. This study is the first to investigate finned monopiles under cyclic loading on sloping seabed conditions, demonstrating a 30–60% improvement in lateral resistance by increasing the passive soil resistance by reducing the rotation compared to monopiles. This work addresses the challenges of Offshore Wind Turbine foundations in complex topographies. Numerical modeling using PLAXIS 3D closely aligned with experimental findings, confirming the effectiveness of finned monopiles in enhancing stability on sloped seabeds. These findings suggest that finned piles offer a robust foundation alternative for Offshore Wind Turbines, particularly in challenging environments with variable seabed topography.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"323 ","pages":"Article 120557"},"PeriodicalIF":4.6,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143351150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A computational fluid dynamics (CFD) study on changes in dissolved oxygen levels during a tidal cycle in a non-conventional finfish aquaculture structure

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-08 DOI: 10.1016/j.oceaneng.2025.120553

Duc Nguyen , Sarah Wakes , Ross Vennell , Si Thu Paing , Scott Rhone , Louise Kregting , Suzy Black

This study examined the effects of i) the maximum current speed, ii) slack tide length, and iii) tidal cycle length, on the Dissolved Oxygen (DO) inside a non-conventional finfish aquaculture structure with varying fish stocking densities between 5 and 30 kgm⁻³, using Computational Fluid Dynamics (CFD). The three volume fractions of interest for finfish to survive and thrive are classified as lethal (DO < 30% of ambient DO); sub-optimal (30% < DO ≤ 70%); and optimal (DO > 70%). When the fish stocking density was 30 kgm⁻³ and the maximum current speed halved from 0.1 to 0.05 ms⁻¹, the lethal time (the time that the lethal DO fraction ≥0.5 of volume structure) increased from 0 to 72 min. Increasing slack tide length from 0 to 60 min increased the lethal time fraction from 0 to 66 min. Increase in tidal length (from semidiurnal to diurnal) resulted in an increase of lethal time from 0 to 63 min. During lower DO supply and greater DO consumption, the lethal fraction dominated the sub-optimal fraction. We recommend that the fish stocking density should be reduced in locations where tide dynamics result in lower DO conditions, to avoid lethal conditions inside the structure.

{"title":"A computational fluid dynamics (CFD) study on changes in dissolved oxygen levels during a tidal cycle in a non-conventional finfish aquaculture structure","authors":"Duc Nguyen , Sarah Wakes , Ross Vennell , Si Thu Paing , Scott Rhone , Louise Kregting , Suzy Black","doi":"10.1016/j.oceaneng.2025.120553","DOIUrl":"10.1016/j.oceaneng.2025.120553","url":null,"abstract":"<div><div>This study examined the effects of i) the maximum current speed, ii) slack tide length, and iii) tidal cycle length, on the Dissolved Oxygen (DO) inside a non-conventional finfish aquaculture structure with varying fish stocking densities between 5 and 30 kgm<sup>−3</sup>, using Computational Fluid Dynamics (CFD). The three volume fractions of interest for finfish to survive and thrive are classified as lethal (DO < 30% of ambient DO); sub-optimal (30% < DO ≤ 70%); and optimal (DO > 70%). When the fish stocking density was 30 kgm<sup>−3</sup> and the maximum current speed halved from 0.1 to 0.05 ms<sup>−1</sup>, the lethal time (the time that the lethal DO fraction ≥0.5 of volume structure) increased from 0 to 72 min. Increasing slack tide length from 0 to 60 min increased the lethal time fraction from 0 to 66 min. Increase in tidal length (from semidiurnal to diurnal) resulted in an increase of lethal time from 0 to 63 min. During lower DO supply and greater DO consumption, the lethal fraction dominated the sub-optimal fraction. We recommend that the fish stocking density should be reduced in locations where tide dynamics result in lower DO conditions, to avoid lethal conditions inside the structure.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"323 ","pages":"Article 120553"},"PeriodicalIF":4.6,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143351147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Application of transfer learning on physics-based models to enhance vessel shaft power predictions

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-08 DOI: 10.1016/j.oceaneng.2025.120540

Stamatis Mavroudis , Tiedo Tinga

International shipping must reduce its emissions to meet global targets, with improving energy efficiency being a crucial step in this journey. Predictive models are essential for implementing energy efficiency measures such as weather routing, scheduling of hull cleanings, and just-in-time arrival, which are vital for reducing fuel consumption and emissions.

This paper explores the use of transfer learning to integrate physics-based and data-driven models for predicting vessel shaft power under varying operating conditions. Physics-based models rely on principles of resistance and propulsion, whereas data-driven models employ advanced machine learning techniques utilizing high-frequency operational data. A novel approach is proposed that integrates synthetic data from physics-based simulations with real operational data via transfer learning. This method enhances model accuracy while significantly reducing the amount of data required, and therefore the time until sufficient data is collected to develop a reliable data-driven model.

The proposed method is demonstrated on an ocean-going vessel use case to predict the shaft power demand in varying conditions. The results reveal that the proposed transfer learning approach outperforms regular data-driven methods, both in accuracy and required training time. The approach thus offers a robust solution for predicting vessel performance, demonstrating improved model accuracy and reduced dependency on extensive real-world data for training.

{"title":"Application of transfer learning on physics-based models to enhance vessel shaft power predictions","authors":"Stamatis Mavroudis , Tiedo Tinga","doi":"10.1016/j.oceaneng.2025.120540","DOIUrl":"10.1016/j.oceaneng.2025.120540","url":null,"abstract":"<div><div>International shipping must reduce its emissions to meet global targets, with improving energy efficiency being a crucial step in this journey. Predictive models are essential for implementing energy efficiency measures such as weather routing, scheduling of hull cleanings, and just-in-time arrival, which are vital for reducing fuel consumption and emissions.</div><div>This paper explores the use of transfer learning to integrate physics-based and data-driven models for predicting vessel shaft power under varying operating conditions. Physics-based models rely on principles of resistance and propulsion, whereas data-driven models employ advanced machine learning techniques utilizing high-frequency operational data. A novel approach is proposed that integrates synthetic data from physics-based simulations with real operational data via transfer learning. This method enhances model accuracy while significantly reducing the amount of data required, and therefore the time until sufficient data is collected to develop a reliable data-driven model.</div><div>The proposed method is demonstrated on an ocean-going vessel use case to predict the shaft power demand in varying conditions. The results reveal that the proposed transfer learning approach outperforms regular data-driven methods, both in accuracy and required training time. The approach thus offers a robust solution for predicting vessel performance, demonstrating improved model accuracy and reduced dependency on extensive real-world data for training.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"323 ","pages":"Article 120540"},"PeriodicalIF":4.6,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143351149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Dynamic damage functions for scour protection at monopile foundations: Application of ensemble machine learning models

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-08 DOI: 10.1016/j.oceaneng.2025.120590

Mohammad Najafzadeh , Ana Margarida Bento , Sajad Basirian , Tiago Fazeres-Ferradosa

This study addresses the critical issue of scour, which represents a significant safety threat to marine and offshore structures. The use of smaller stone sizes in scour protections has given rise to concerns pertaining to the potential for damage, thereby emphasizing the imperative for the formulation of explicit criteria to define damage. In order to reduce the uncertainty associated with empirical equations, this research proposes the use of Machine Learning (ML) models to enhance the accuracy of the results. The ML models were developed from the analysis of experimental models concerning dynamic scour protections. A total of 160 scour tests from the existing literature were subjected to analysis in order to quantify the damage levels in protected monopile foundations. Five ML algorithms were employed to quantify the damage: Random Forest (RF), Support Vector Machine (SVM), Extreme Gradient Boosting (XGBoost), Adaptive Boosting (AdaBoost), and Categorical Boosting (CatBoost). In the training and testing phases, the XGBoost, CatBoost, and AdaBoost models exhibited superior accuracy in predicting damage, with the RF models exhibiting a worse performance. The results provide substantial evidence of the potential of ML techniques to damage levels at scour protections. Furthermore, the promising performance of visual assessment of scour damage at monopile foundations was observed across different wave number ranges (N = 3000–5000).

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引用次数: 0

Mechanism of sailing safety through bridge area based on a coupled hull-propeller-rudder model

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-08 DOI: 10.1016/j.oceaneng.2025.120591

Yang Miao , Lei Zhang , Zhiyong Pei , Longming Gu , Bin Liu

The safety of ships sailing through bridge areas has received significant attention, and the ship model without propeller and rudder (H-model) is widely used nowadays. To further elucidate the sailing mechanism in the bridge area, a coupled hull-propeller-rudder model (C-model) is proposed. Specifically, secondary development based on Fluent is undertaken. The governing equations of the ship are embedded using the user-defined function (UDF) module, and a modified multiple reference frame (MRF) model is employed to solve the coupled translational and rotational motions of the propeller. Compared to the motion parameters obtained by the H-model, the additional flow-mediated interactions among the propeller, rudder and pier lead to a smaller yaw angle and a greater lateral displacement. The reasons for these changes are given by analyzing the flow evolution and ship motions. The effects of flow velocity and ship velocity are also given. In front of the pier, the lateral displacement and yaw angle of the ship increase with the flow velocity and decrease with the ship velocity. Behind the pier, the yaw angles increase continuously under conditions of the low flow velocity and high ship velocity, thereby increasing the risk of the stern of the ship sweeping against the pier.

{"title":"Mechanism of sailing safety through bridge area based on a coupled hull-propeller-rudder model","authors":"Yang Miao , Lei Zhang , Zhiyong Pei , Longming Gu , Bin Liu","doi":"10.1016/j.oceaneng.2025.120591","DOIUrl":"10.1016/j.oceaneng.2025.120591","url":null,"abstract":"<div><div>The safety of ships sailing through bridge areas has received significant attention, and the ship model without propeller and rudder (H-model) is widely used nowadays. To further elucidate the sailing mechanism in the bridge area, a coupled hull-propeller-rudder model (C-model) is proposed. Specifically, secondary development based on Fluent is undertaken. The governing equations of the ship are embedded using the user-defined function (UDF) module, and a modified multiple reference frame (MRF) model is employed to solve the coupled translational and rotational motions of the propeller. Compared to the motion parameters obtained by the H-model, the additional flow-mediated interactions among the propeller, rudder and pier lead to a smaller yaw angle and a greater lateral displacement. The reasons for these changes are given by analyzing the flow evolution and ship motions. The effects of flow velocity and ship velocity are also given. In front of the pier, the lateral displacement and yaw angle of the ship increase with the flow velocity and decrease with the ship velocity. Behind the pier, the yaw angles increase continuously under conditions of the low flow velocity and high ship velocity, thereby increasing the risk of the stern of the ship sweeping against the pier.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"323 ","pages":"Article 120591"},"PeriodicalIF":4.6,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143351153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0