Ocean Engineering最新文献

英文中文

Member-level probabilistic durability design of reinforced concrete structures in marine environment: Framework and general procedures

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.120001

Xinyi Ye , Quanwang Li , Hao Zhang

In existing probabilistic durability design for marine reinforced concrete (RC) structures, the material-level deterioration behavior is modelled, and corrosion onset at a point on the rebar is taken as the limit state. However, the owners may more concern the risk of the structural member's surface damage or the potential maintenance demands. To bridge the gap, a member-level durability design method is developed in this paper. It treats the target reliability index as a function of member-level target performance, and incorporates the existing design method into the proposed framework. Its differences and relations with the existing material-level method are addressed. By improving the effective tools from existing studies, the general procedures of performing a member-level durability design are proposed. Taking the HZM project as the examples, member-level durability designs are performed for its beams, columns and immerged tube tunnels under various exposure conditions with various design targets being considered. Accuracy of the design outputs are checked by assessing the corresponding member-level performance and comparing it to the design targets. In addition, the proposed method is also validated with the in-situ data from an in-service high-pile RC wharf.

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引用次数: 0

Seismic response characteristics and liquefaction risk of artificial island with saturated hydraulic fill coral sand

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.120025

Baokui Chen , Yufei Ye , Dongsheng Wang , Yurun Li , Jingang Xiong , Chunxu Qu

Marine artificial islands are generally constructed by hydraulic fill coral sand. Existing seismic damages show that the saturated coral sand foundation faces serious liquefaction risk. However, previous studies on the liquefaction of artificial islands mainly concentrate on the damage resulting from seabed site liquefaction, neglecting the liquefaction risk of island backfill material. This study focuses on the seismic response characteristics and liquefaction risk of islands. Firstly, a series model of seismic wave analysis and liquefaction analysis is innovatively proposed, the proposed analysis method can effectively analyze the liquefaction risk characteristics caused by offshore ground motions that include real site features of the seabed and artificial island. Subsequently, the influencing factors of seismic response and liquefaction risk are discussed, such as the relative density and thickness of the coral sand foundation, seawater and seabed site conditions. The results indicate that the liquefaction area is significantly decreased when the relative density increased from 55% to 65%. Notably, when the relative density is greater than 75%, the continuous increase of the relative density has limited improvement in the anti-liquefaction ability. The influence of seawater and nonlinear silt layer on the seabed is limited.

{"title":"Seismic response characteristics and liquefaction risk of artificial island with saturated hydraulic fill coral sand","authors":"Baokui Chen , Yufei Ye , Dongsheng Wang , Yurun Li , Jingang Xiong , Chunxu Qu","doi":"10.1016/j.oceaneng.2024.120025","DOIUrl":"10.1016/j.oceaneng.2024.120025","url":null,"abstract":"<div><div>Marine artificial islands are generally constructed by hydraulic fill coral sand. Existing seismic damages show that the saturated coral sand foundation faces serious liquefaction risk. However, previous studies on the liquefaction of artificial islands mainly concentrate on the damage resulting from seabed site liquefaction, neglecting the liquefaction risk of island backfill material. This study focuses on the seismic response characteristics and liquefaction risk of islands. Firstly, a series model of seismic wave analysis and liquefaction analysis is innovatively proposed, the proposed analysis method can effectively analyze the liquefaction risk characteristics caused by offshore ground motions that include real site features of the seabed and artificial island. Subsequently, the influencing factors of seismic response and liquefaction risk are discussed, such as the relative density and thickness of the coral sand foundation, seawater and seabed site conditions. The results indicate that the liquefaction area is significantly decreased when the relative density increased from 55% to 65%. Notably, when the relative density is greater than 75%, the continuous increase of the relative density has limited improvement in the anti-liquefaction ability. The influence of seawater and nonlinear silt layer on the seabed is limited.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"317 ","pages":"Article 120025"},"PeriodicalIF":4.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143094766","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

Analysis of vessel traffic flow characteristics in inland restricted waterways using multi-source data

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.120065

Wenzhang Yang , Peng Liao , Shangkun Jiang , Hao Wang

To effectively manage vessel traffic and alleviate congestion on busy inland waterways, it is crucial to understand vessel traffic flow characteristics. However, limited data availability has hindered research in this area. This study addresses this gap by conducting vessel-following experiments and fixed-point video monitoring to collect multi-source data. First, distributions of traffic flow parameters are analyzed, then the relationship between microscopic vessel speed and gap distance is examined. Next, the study explores the macroscopic relationships among speed, density, and flow rate, proposing a novel piecewise fundamental diagram model. Lastly, inland vessel traffic states are categorized using the K-means clustering algorithm, which is then applied to vessel navigation services. The results reveal that: in the inland restricted waterways of Jiangsu Province, (1) the economic speeds for empty and loaded vessels are approximately 12 km/h and 9 km/h, respectively; (2) the minimum vessel speed is around 2.65 km/h, with a minimum gap distance of 12 m; and (3) the maximum flow rate is about 44 vessels per hour, with an optimal vessel density below 4 vessels per kilometer to reduce delays and improve efficiency. These findings offer valuable insights for enhancing inland waterway transportation and supporting the development of integrated waterway systems.

{"title":"Analysis of vessel traffic flow characteristics in inland restricted waterways using multi-source data","authors":"Wenzhang Yang , Peng Liao , Shangkun Jiang , Hao Wang","doi":"10.1016/j.oceaneng.2024.120065","DOIUrl":"10.1016/j.oceaneng.2024.120065","url":null,"abstract":"<div><div>To effectively manage vessel traffic and alleviate congestion on busy inland waterways, it is crucial to understand vessel traffic flow characteristics. However, limited data availability has hindered research in this area. This study addresses this gap by conducting vessel-following experiments and fixed-point video monitoring to collect multi-source data. First, distributions of traffic flow parameters are analyzed, then the relationship between microscopic vessel speed and gap distance is examined. Next, the study explores the macroscopic relationships among speed, density, and flow rate, proposing a novel piecewise fundamental diagram model. Lastly, inland vessel traffic states are categorized using the K-means clustering algorithm, which is then applied to vessel navigation services. The results reveal that: in the inland restricted waterways of Jiangsu Province, (1) the economic speeds for empty and loaded vessels are approximately 12 km/h and 9 km/h, respectively; (2) the minimum vessel speed is around 2.65 km/h, with a minimum gap distance of 12 m; and (3) the maximum flow rate is about 44 vessels per hour, with an optimal vessel density below 4 vessels per kilometer to reduce delays and improve efficiency. These findings offer valuable insights for enhancing inland waterway transportation and supporting the development of integrated waterway systems.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"317 ","pages":"Article 120065"},"PeriodicalIF":4.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143094662","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

Fish-friendly optimization of low-head axial-flow turbines

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.120070

Kan Kan , Yunkuan Yu , Feng Zhao , Jinbo Chen , Maxime Binama , Huixiang Chen

Given the global trend toward fully exploiting large hydropower bases, industry and academia are increasingly focusing on low-head small hydro systems. These systems offer numerous advantages, such as low cost, short construction time, and minimal environmental impact. This study is based on a low-head axial-flow turbine model developed using Standard Modular Hydropower technology. The turbine was redesigned and optimized by reducing the number of runner blades from eight to four, which not only ensured excellent hydraulic performance but also enhanced fish passage capacity. The results indicated that the fish mortality rate due to impact with the blades was the highest within the low-head turbine runner. In contrast, the probability of fish damage due to pressure gradient and shear stress remained low, with fish being nearly immune to direct pressure damage. Orthogonal experiments revealed that the parameters influencing the runner airfoil profile had a greater impact on efficiency than those affecting the stator airfoil profile. Among these, the coefficient of the runner blade installation angle (Crsa) was found to have the most significant effect on turbine efficiency. Following optimization, the fish damage probability due to pressure gradient inside the runner under high-flow conditions and the fish damage probability due to shear stress under low-flow conditions were reduced to a certain extent. Furthermore, the fish mortality rate due to blade impact was significantly reduced, with a maximum reduction ratio of 65%. This study offers a novel approach for optimizing the design of fish-friendly hydraulic turbines, with significant implications for the sustainable use of low-head hydraulic resources and environmental protection.

{"title":"Fish-friendly optimization of low-head axial-flow turbines","authors":"Kan Kan , Yunkuan Yu , Feng Zhao , Jinbo Chen , Maxime Binama , Huixiang Chen","doi":"10.1016/j.oceaneng.2024.120070","DOIUrl":"10.1016/j.oceaneng.2024.120070","url":null,"abstract":"<div><div>Given the global trend toward fully exploiting large hydropower bases, industry and academia are increasingly focusing on low-head small hydro systems. These systems offer numerous advantages, such as low cost, short construction time, and minimal environmental impact. This study is based on a low-head axial-flow turbine model developed using Standard Modular Hydropower technology. The turbine was redesigned and optimized by reducing the number of runner blades from eight to four, which not only ensured excellent hydraulic performance but also enhanced fish passage capacity. The results indicated that the fish mortality rate due to impact with the blades was the highest within the low-head turbine runner. In contrast, the probability of fish damage due to pressure gradient and shear stress remained low, with fish being nearly immune to direct pressure damage. Orthogonal experiments revealed that the parameters influencing the runner airfoil profile had a greater impact on efficiency than those affecting the stator airfoil profile. Among these, the coefficient of the runner blade installation angle (Crsa) was found to have the most significant effect on turbine efficiency. Following optimization, the fish damage probability due to pressure gradient inside the runner under high-flow conditions and the fish damage probability due to shear stress under low-flow conditions were reduced to a certain extent. Furthermore, the fish mortality rate due to blade impact was significantly reduced, with a maximum reduction ratio of 65%. This study offers a novel approach for optimizing the design of fish-friendly hydraulic turbines, with significant implications for the sustainable use of low-head hydraulic resources and environmental protection.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"317 ","pages":"Article 120070"},"PeriodicalIF":4.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143094715","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

Calculation method of flow drag around a pile in soft soil considering Bingham fluid properties and analysis of single pile response

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.120031

Min Wu , Jiayong Zheng , Qijian Liu , Lu Zheng , Tao Deng

The lateral displacement of deep soft soil caused by large-area heap loading is a common issue in engineering practice, which affects the stability of neighboring pile foundations. This study investigates the calculation of thrust force exerted by the flow of soft soil around piles and its impact on pile foundations. The surrounding soft soil is considered a Bingham fluid. An analytical formula for single pile flow drag during the internal slip of deep soft soil is derived based on fluid mechanics theory and the fluid characteristics of the Bingham fluid. The traditional cantilever pile approach is modified by assuming a rectangular distribution of flow drag along the pile body and using the matrix transfer method. The response of a single pile body under field heap loading conditions is then analyzed, and the results are compared with the calculation results of the traditional soil pressure method and field-measured data to validate the proposed calculation method for flow drag around a pile in soft soil. Finally, a parametric study is conducted to analyze the effects of the relative flow velocity and dynamic viscous coefficient of soft soil on flow drag.

{"title":"Calculation method of flow drag around a pile in soft soil considering Bingham fluid properties and analysis of single pile response","authors":"Min Wu , Jiayong Zheng , Qijian Liu , Lu Zheng , Tao Deng","doi":"10.1016/j.oceaneng.2024.120031","DOIUrl":"10.1016/j.oceaneng.2024.120031","url":null,"abstract":"<div><div>The lateral displacement of deep soft soil caused by large-area heap loading is a common issue in engineering practice, which affects the stability of neighboring pile foundations. This study investigates the calculation of thrust force exerted by the flow of soft soil around piles and its impact on pile foundations. The surrounding soft soil is considered a Bingham fluid. An analytical formula for single pile flow drag during the internal slip of deep soft soil is derived based on fluid mechanics theory and the fluid characteristics of the Bingham fluid. The traditional cantilever pile approach is modified by assuming a rectangular distribution of flow drag along the pile body and using the matrix transfer method. The response of a single pile body under field heap loading conditions is then analyzed, and the results are compared with the calculation results of the traditional soil pressure method and field-measured data to validate the proposed calculation method for flow drag around a pile in soft soil. Finally, a parametric study is conducted to analyze the effects of the relative flow velocity and dynamic viscous coefficient of soft soil on flow drag.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"317 ","pages":"Article 120031"},"PeriodicalIF":4.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143094344","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

Interference between main and auxiliary rotors in floating dual-rotor wind turbines under stationary and surge conditions

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2025.120462

Xueying Peng , Lei Duan , Gen Li , Yanhui Jin , Zhaolong Han

As the size of floating offshore wind turbines increases, the cylindrical segments at the blade roots, which have poor aerodynamic performance, also lengthen to meet structural strength requirements, leading to considerable wind energy dissipation. The floating dual-rotor wind turbine (FDRWT) emerges as a solution to mitigate this challenge. This study applies CFD method on a full-scale model to explore aerodynamic features of FDRWTs. Initially, interaction between the main and auxiliary rotors, as well as the overall aerodynamic performance of the FDRWT without platform motion, is investigated. Results show that the overall efficiency of the FDRWT exceeds that of the corresponding floating single-rotor wind turbine (FSRWT) by 1.74%, despite the main rotor's efficiency decreases by 1.87% and the auxiliary one's by 3.37%, due to mutual interference. The study also examines the FDRWT's performance under platform surge motion, revealing that both the average value and fluctuations of the total power coefficient increase with surge intensity. Additionally, the auxiliary rotor exhibits high-frequency, low-amplitude fluctuations induced by the main rotor. While the FDRWT enhances energy capture, its economic feasibility, considering construction and maintenance costs, must be carefully evaluated. These findings highlight the potential of FDRWTs to improve offshore wind energy efficiency but underscore the need for detailed economic assessments in their design.

{"title":"Interference between main and auxiliary rotors in floating dual-rotor wind turbines under stationary and surge conditions","authors":"Xueying Peng , Lei Duan , Gen Li , Yanhui Jin , Zhaolong Han","doi":"10.1016/j.oceaneng.2025.120462","DOIUrl":"10.1016/j.oceaneng.2025.120462","url":null,"abstract":"<div><div>As the size of floating offshore wind turbines increases, the cylindrical segments at the blade roots, which have poor aerodynamic performance, also lengthen to meet structural strength requirements, leading to considerable wind energy dissipation. The floating dual-rotor wind turbine (FDRWT) emerges as a solution to mitigate this challenge. This study applies CFD method on a full-scale model to explore aerodynamic features of FDRWTs. Initially, interaction between the main and auxiliary rotors, as well as the overall aerodynamic performance of the FDRWT without platform motion, is investigated. Results show that the overall efficiency of the FDRWT exceeds that of the corresponding floating single-rotor wind turbine (FSRWT) by 1.74%, despite the main rotor's efficiency decreases by 1.87% and the auxiliary one's by 3.37%, due to mutual interference. The study also examines the FDRWT's performance under platform surge motion, revealing that both the average value and fluctuations of the total power coefficient increase with surge intensity. Additionally, the auxiliary rotor exhibits high-frequency, low-amplitude fluctuations induced by the main rotor. While the FDRWT enhances energy capture, its economic feasibility, considering construction and maintenance costs, must be carefully evaluated. These findings highlight the potential of FDRWTs to improve offshore wind energy efficiency but underscore the need for detailed economic assessments in their design.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"322 ","pages":"Article 120462"},"PeriodicalIF":4.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143168075","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

Boundary-layer transition on a shallowly submerged vehicle

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.120051

Bin Liu , Zhanchao Yin , Qiyi An , Xiao Zhang

As the underwater vehicle travels beneath the free surface, the surface gravity waves are generated, which may have a significant effect on the boundary-layer transition. The boundary-layer transitions on a shallowly submerged vehicle are investigated by coupling the transition model, wave system model, and volume of fluid model. The numerical method is validated through the experimental data and theory. It is found that the free surface has a significant influence on the boundary-layer transition of the upper surface, whereas no such influence is observed on the transition of the lower surface. On the upper surface, the wave system of the free surface results in a fuller velocity profile and a more extended region of the laminar flow, which causes a delay in the boundary-layer transition. The underlying mechanism of the transition delay phenomenon on a shallowly submerged vehicle is discussed. It is observed that the region of the favorable pressure gradient generated by the interaction between the bow and aft shoulder waves of the free surface becomes larger. Furthermore, as the submergence depth increases, the transition delay effect weakens rapidly, which is closely associated with the sharp reduction in amplitude of the free surface wave and in favorable pressure gradient.

{"title":"Boundary-layer transition on a shallowly submerged vehicle","authors":"Bin Liu , Zhanchao Yin , Qiyi An , Xiao Zhang","doi":"10.1016/j.oceaneng.2024.120051","DOIUrl":"10.1016/j.oceaneng.2024.120051","url":null,"abstract":"<div><div>As the underwater vehicle travels beneath the free surface, the surface gravity waves are generated, which may have a significant effect on the boundary-layer transition. The boundary-layer transitions on a shallowly submerged vehicle are investigated by coupling the transition model, wave system model, and volume of fluid model. The numerical method is validated through the experimental data and theory. It is found that the free surface has a significant influence on the boundary-layer transition of the upper surface, whereas no such influence is observed on the transition of the lower surface. On the upper surface, the wave system of the free surface results in a fuller velocity profile and a more extended region of the laminar flow, which causes a delay in the boundary-layer transition. The underlying mechanism of the transition delay phenomenon on a shallowly submerged vehicle is discussed. It is observed that the region of the favorable pressure gradient generated by the interaction between the bow and aft shoulder waves of the free surface becomes larger. Furthermore, as the submergence depth increases, the transition delay effect weakens rapidly, which is closely associated with the sharp reduction in amplitude of the free surface wave and in favorable pressure gradient.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"317 ","pages":"Article 120051"},"PeriodicalIF":4.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143094273","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

Large eddy simulation of the flow field characteristics around a jacket foundation under unidirectional flow actions

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.120057

Hao Chen , Jisheng Zhang , Peng Zhang , Yakun Guo , Yiming Ji , Runze Fu

Jacket foundation is primarily used to support the tower and fan blades of offshore wind turbines in water depths exceeding 30 m and is designed in a modular pattern and assembled on-site. However, to date, limited research has been conducted on scour and flow field characteristics around jacket foundations under complex marine conitions. This paper employs the Large Eddy Simulation to simulate flow field and sediment transport around the jacket foundation. Results indicate that, compared to flat bed condition, the maximum streamwise and vertical velocities around the jacket decrease by 17% and 13% under the scour equilibrium condition. During the initial scour stage (

t

= 0.25 h), turbulence intensity (

T I

) and turbulent kinetic energy (

T K E

) decrease by 9% and 17%, respectively, compared to the flat bed condition. As scour progresses, both

T I

and

T K E

gradually increase, approaching values under the flat bed condition. Additionally, the increase in flow intensity exacerbates the scour, accompanied by increased energy dissipation within the scour pit. The flow field characteristics around the back pile of the jacket are influenced by the energy dissipation as well as by sand dunes formed between piles. The flow field characteristics around the jacket foundation are minimally affected by water depth.

{"title":"Large eddy simulation of the flow field characteristics around a jacket foundation under unidirectional flow actions","authors":"Hao Chen , Jisheng Zhang , Peng Zhang , Yakun Guo , Yiming Ji , Runze Fu","doi":"10.1016/j.oceaneng.2024.120057","DOIUrl":"10.1016/j.oceaneng.2024.120057","url":null,"abstract":"<div><div>Jacket foundation is primarily used to support the tower and fan blades of offshore wind turbines in water depths exceeding 30 m and is designed in a modular pattern and assembled on-site. However, to date, limited research has been conducted on scour and flow field characteristics around jacket foundations under complex marine conitions. This paper employs the Large Eddy Simulation to simulate flow field and sediment transport around the jacket foundation. Results indicate that, compared to flat bed condition, the maximum streamwise and vertical velocities around the jacket decrease by 17% and 13% under the scour equilibrium condition. During the initial scour stage (<span><math><mrow><mi>t</mi></mrow></math></span> = 0.25 h), turbulence intensity (<span><math><mrow><mi>T</mi><mi>I</mi></mrow></math></span>) and turbulent kinetic energy (<span><math><mrow><mi>T</mi><mi>K</mi><mi>E</mi></mrow></math></span>) decrease by 9% and 17%, respectively, compared to the flat bed condition. As scour progresses, both <span><math><mrow><mi>T</mi><mi>I</mi></mrow></math></span> and <span><math><mrow><mi>T</mi><mi>K</mi><mi>E</mi></mrow></math></span> gradually increase, approaching values under the flat bed condition. Additionally, the increase in flow intensity exacerbates the scour, accompanied by increased energy dissipation within the scour pit. The flow field characteristics around the back pile of the jacket are influenced by the energy dissipation as well as by sand dunes formed between piles. The flow field characteristics around the jacket foundation are minimally affected by water depth.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"317 ","pages":"Article 120057"},"PeriodicalIF":4.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143094280","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

On energy efficiency of tankers: EEDI, EEXI and CII

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.120028

Matija Vasilev, Milan Kalajdžić, Nikola Momčilović

This paper aims to extensively analyze the energy efficiency of large tanker fleets, focusing on their compliance with the International Maritime Organization (IMO) requirements through the evaluation of design and operational indices. Despite an increase in energy efficiency studies, few have assessed large tanker fleets and their subgroups systematically, leaving a significant gap regarding the impact of regulations on different tanker sizes. The paper evaluates the energy efficiencies of tankers concerning Energy Efficiency Existing Ship Index (EEXI), Energy Efficiency Design Index (EEDI), and Carbon Intensity Indicator (CII), differentiating ships by size and type. It further explores and provides the potential reductions in speed and power for each subgroup of tankers, required to meet current and future energy efficiency requirements. The outcome shows that regulatory measures like EEDI, EEXI, and CII have significantly improved energy efficiency, but compliance remains challenging, with only 14.8% of ships meeting the EEXI criteria, especially for smaller ships, which face greater power reductions than larger ones. The results also indicate that the considered fleet of tankers does not operate at more than 60% of the available engine power and that the ships are already sailing at 8% lower speed than for which they were designed.

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引用次数: 0

Design strategy for submerged floating tunnels: Structural response analysis and rational mooring-boundary condition combinations under wave loads

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.120097

Kiwon Jeong, Jinwoo Kim, Seongi Min, Hyunwoo Shin, Seungjun Kim

This study examines the dynamic behavior of submerged floating tunnels (SFTs) induced by wave action, considering various mooring types and boundary conditions to determine optimal design strategies. The analysis includes three mooring configurations: vertical (Type 1), inclined (Type 2), and combined inclined (Type 3), evaluated under four distinct boundary conditions: free, fixed, hinged, and hinged-fixed. Through a detailed comparative analysis of structural responses under irregular wave conditions, this research reveals the significant influence of both mooring configurations and boundary conditions on the performance of SFTs. Furthermore, the study identifies the optimal combination by analyzing serviceability, strength, and stability criteria. The combination of Type 3 mooring with free boundary conditions proved most advantageous, effectively minimizing displacements, accelerations, and stresses while satisfying all design criteria, even under inclined wave conditions. Furthermore, optimization of the Type 3 mooring was also performed. These insights offer valuable guidance for engineers involved in the design of SFTs.

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引用次数: 0

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