Pub Date : 2025-01-01DOI: 10.1016/j.apor.2024.104332
Lawrence J. Doctors
A simple model of the water flow behind a transom stern is presented. The water is assumed to separate cleanly from the bottom of the transom and it is considered that this domain of the flow is inviscid. Immediately aft of the transom is a stagnant region, in which the pressure can be computed on purely hydrostatic grounds. It is this hydrostatic pressure that acts upon the free-surface of the first water domain. Linearized free-surface theory is utilized to perform the analysis. The theoretical results for the length of the hollow and its profile area are seen to be much higher than the experimental data would suggest. It is thought that the source of the discrepancy is the hydraulic jump in the free surface which cannot be modeled using the current theory.
{"title":"Pseudo-inviscid theory for transom-stern flow at low Froude numbers","authors":"Lawrence J. Doctors","doi":"10.1016/j.apor.2024.104332","DOIUrl":"10.1016/j.apor.2024.104332","url":null,"abstract":"<div><div>A simple model of the water flow behind a transom stern is presented. The water is assumed to separate cleanly from the bottom of the transom and it is considered that this domain of the flow is inviscid. Immediately aft of the transom is a stagnant region, in which the pressure can be computed on purely hydrostatic grounds. It is this hydrostatic pressure that acts upon the free-surface of the first water domain. Linearized free-surface theory is utilized to perform the analysis. The theoretical results for the length of the hollow and its profile area are seen to be much higher than the experimental data would suggest. It is thought that the source of the discrepancy is the hydraulic jump in the free surface which cannot be modeled using the current theory.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104332"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166912","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}
Pub Date : 2025-01-01DOI: 10.1016/j.apor.2024.104377
Jian Yang , Zhaochen Sun , Jiayang Gu , Xiaojian Ma , Shuxiu Liang
This work investigates wave impacts on the flexible wall. An experiment was conducted to investigate shallow water solitary wave impacts on a flexible wall, and the results are presented. During the experiment, the water depth (h) varied between 0.22 and 0.3 m, the ratio of incident wave height and the water depth (H/h) varied between 0.1 and 0.5. The bottom of the flexible wall was constrained while the top end remained free, with the lowest dry natural frequency being 14.2 Hz. The experiment identified various types of wave impacts, including the flip-through impact without aeration, the low-aeration impact, the high-aeration impact, and the broken wave impact. Subsequently, an analysis was conducted to explore the characteristics of impact pressures, slamming phenomena, and structural deflections under these different impact types. Furthermore, we directed our attention to the correlation between wave conditions and structural dynamic response, discovering that a linear fit adequately describes the relationship between the maximum structural displacement and the relative wave height under the current experimental conditions. This study can be beneficial in enhancing our understanding of wave impacts on flexible walls and provides a solid foundation for future work.
{"title":"Experimental study of shallow water solitary wave impacts on a bottom-constrained flexible wall","authors":"Jian Yang , Zhaochen Sun , Jiayang Gu , Xiaojian Ma , Shuxiu Liang","doi":"10.1016/j.apor.2024.104377","DOIUrl":"10.1016/j.apor.2024.104377","url":null,"abstract":"<div><div>This work investigates wave impacts on the flexible wall. An experiment was conducted to investigate shallow water solitary wave impacts on a flexible wall, and the results are presented. During the experiment, the water depth (<em>h</em>) varied between 0.22 and 0.3 m, the ratio of incident wave height and the water depth (<em>H</em>/<em>h</em>) varied between 0.1 and 0.5. The bottom of the flexible wall was constrained while the top end remained free, with the lowest dry natural frequency being 14.2 Hz. The experiment identified various types of wave impacts, including the flip-through impact without aeration, the low-aeration impact, the high-aeration impact, and the broken wave impact. Subsequently, an analysis was conducted to explore the characteristics of impact pressures, slamming phenomena, and structural deflections under these different impact types. Furthermore, we directed our attention to the correlation between wave conditions and structural dynamic response, discovering that a linear fit adequately describes the relationship between the maximum structural displacement and the relative wave height under the current experimental conditions. This study can be beneficial in enhancing our understanding of wave impacts on flexible walls and provides a solid foundation for future work.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104377"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166917","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}
Evaluating instantaneous power output of heaving-buoy wave energy converters (WECs) with power take-off (PTO) damping in irregular waves has commonly been conducted in the time domain by numerically solving the Cummins equation. Not only is the time domain-method computationally time-consuming, but also no explicit closed-form solution has been available. This paper develops a novel and efficient pole-residue approach, operated in the frequency domain, for estimating instantaneous power of heaving-buoy WECs in arbitrary irregular waves. A closed-form solution for the instantaneous power, which is an explicit function of PTO damping coefficient, is derived. The proposed pole-residue approach formulates the system frequency response function in its analytical form, from which “artificial” poles located along the imaginary axis of complex plane are designated. The correctness of the proposed method is verified by using a time-domain method through numerical examples of a heaving-buoy WEC in regular and irregular waves, respectively. The proposed method would be useful for the practical design and optimization of the PTO system for heaving-buoy WECs.
{"title":"Analytical solutions for instantaneous power of heaving-buoy wave energy converters in irregular waves","authors":"Shixuan Liu, Jinwei Sun, Meng Shao, Shuai Cong, Linqiang Zhang, Chongyang Sun, Wei Tao, Yunming Han","doi":"10.1016/j.apor.2024.104381","DOIUrl":"10.1016/j.apor.2024.104381","url":null,"abstract":"<div><div>Evaluating instantaneous power output of heaving-buoy wave energy converters (WECs) with power take-off (PTO) damping in irregular waves has commonly been conducted in the time domain by numerically solving the Cummins equation. Not only is the time domain-method computationally time-consuming, but also no explicit closed-form solution has been available. This paper develops a novel and efficient pole-residue approach, operated in the frequency domain, for estimating instantaneous power of heaving-buoy WECs in arbitrary irregular waves. A closed-form solution for the instantaneous power, which is an explicit function of PTO damping coefficient, is derived. The proposed pole-residue approach formulates the system frequency response function in its analytical form, from which “artificial” poles located along the imaginary axis of complex plane are designated. The correctness of the proposed method is verified by using a time-domain method through numerical examples of a heaving-buoy WEC in regular and irregular waves, respectively. The proposed method would be useful for the practical design and optimization of the PTO system for heaving-buoy WECs.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104381"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166939","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}
Pub Date : 2025-01-01DOI: 10.1016/j.apor.2024.104407
Yang Gao , Tonghui Yang , Cheng Wang , Yuanbo Sun
Underwater electrical wire explosion (UEWE) is an efficient source of underwater shock waves and bubble pulsation. However, the impact of wire parameters on the dynamics of shock waves and bubbles generated by UEWE has not been thoroughly explored. In this paper, we present novel insights based on a self-built UEWE experimental platform, where high-power electric pulses are used to ionize and explode aluminum wires of varying diameters and lengths in water. The experimental investigation focused on the resulting shock waves and bubble pulsation behavior, contributing to a deeper understanding of the mechanisms underlying these phenomena. First, we examined the energy storage conditions of the pulse capacitor and characterized the discharge behavior of the electrical explosion. Subsequently, we analyzed the bubble generation mechanism and the complete pulsation process, comparing the maximum bubble radius with the Rayleigh-Plesset equation solution, finding a high degree of consistency during the first pulsation period. Furthermore, we explored the relationships between the maximum bubble radius, shock wave energy, bubble energy, shock wave pressure, pulsation pressure curves, and bubble pulsation period under various experimental conditions. Our results demonstrate that for a 0.5 mm diameter aluminum wire, both the shock wave energy and bubble energy are positively correlated with the wire length, achieving maximum efficiencies of 13.04 % and 79.7 %, respectively. The shock wave peak under each experimental condition also shows a positive correlation with wire diameter and length, while the second pressure wave exhibits a concave trend and the third a convex trend. Notably, before the bubble pulsation period reaches its peak, the period shortens as the wire diameter and length increase, influenced by the aluminum-water reaction. These findings provide a novel perspective on UEWE, advancing the research of explosion bubbles to ensure safer and more efficient underwater explosions, thereby contributing to the broader field of underwater explosion mechanics.
{"title":"Experimental study on shock wave and bubble pulsation behavior generated by underwater aluminum wire electrical explosion","authors":"Yang Gao , Tonghui Yang , Cheng Wang , Yuanbo Sun","doi":"10.1016/j.apor.2024.104407","DOIUrl":"10.1016/j.apor.2024.104407","url":null,"abstract":"<div><div>Underwater electrical wire explosion (UEWE) is an efficient source of underwater shock waves and bubble pulsation. However, the impact of wire parameters on the dynamics of shock waves and bubbles generated by UEWE has not been thoroughly explored. In this paper, we present novel insights based on a self-built UEWE experimental platform, where high-power electric pulses are used to ionize and explode aluminum wires of varying diameters and lengths in water. The experimental investigation focused on the resulting shock waves and bubble pulsation behavior, contributing to a deeper understanding of the mechanisms underlying these phenomena. First, we examined the energy storage conditions of the pulse capacitor and characterized the discharge behavior of the electrical explosion. Subsequently, we analyzed the bubble generation mechanism and the complete pulsation process, comparing the maximum bubble radius with the Rayleigh-Plesset equation solution, finding a high degree of consistency during the first pulsation period. Furthermore, we explored the relationships between the maximum bubble radius, shock wave energy, bubble energy, shock wave pressure, pulsation pressure curves, and bubble pulsation period under various experimental conditions. Our results demonstrate that for a 0.5 mm diameter aluminum wire, both the shock wave energy and bubble energy are positively correlated with the wire length, achieving maximum efficiencies of 13.04 % and 79.7 %, respectively. The shock wave peak under each experimental condition also shows a positive correlation with wire diameter and length, while the second pressure wave exhibits a concave trend and the third a convex trend. Notably, before the bubble pulsation period reaches its peak, the period shortens as the wire diameter and length increase, influenced by the aluminum-water reaction. These findings provide a novel perspective on UEWE, advancing the research of explosion bubbles to ensure safer and more efficient underwater explosions, thereby contributing to the broader field of underwater explosion mechanics.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104407"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166949","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}
Pub Date : 2025-01-01DOI: 10.1016/j.apor.2024.104398
Martin Träsch , Peter Davies , Damien Le Vour’ch , Vincent Perier , Michel Répécaud , Guillaume Damblans , Romain Ribault , Jean Sebastien Verjut
Fiber ropes (polyester, nylon, HMPE, etc.) are being considered for Floating Offshore Wind Turbines mooring lines, as they can reduce mooring weight and cost. Measuring the strain of these synthetic mooring lines could help to understand their behavior and long term monitoring of these systems could lead to their design and maintenance optimization.
A new strain sensor for synthetic mooring lines is proposed in this paper. It uses an ultrasonic altimeter to measure the distance between the transducer and a target fixed on a synthetic mooring line. This instrument is non-intrusive and can be fixed on anchor lines after their installation at sea. The measurement principle and prototype design are presented. Then, the validation of the concept in a water tank is described, demonstrating the feasibility of measuring length using acoustic waves with a high degree of accuracy. The acoustic strain sensor was deployed in operational condition on a demonstrator buoy mooring line in the Mediterranean sea, together with a wire displacement sensor and a load sensor. The measurements from these three instruments are compared, showing the ability of the acoustic sensor to monitor the behavior of a mooring line at sea.
{"title":"Development of an acoustic sensor to monitor synthetic mooring lines","authors":"Martin Träsch , Peter Davies , Damien Le Vour’ch , Vincent Perier , Michel Répécaud , Guillaume Damblans , Romain Ribault , Jean Sebastien Verjut","doi":"10.1016/j.apor.2024.104398","DOIUrl":"10.1016/j.apor.2024.104398","url":null,"abstract":"<div><div>Fiber ropes (polyester, nylon, HMPE, etc.) are being considered for Floating Offshore Wind Turbines mooring lines, as they can reduce mooring weight and cost. Measuring the strain of these synthetic mooring lines could help to understand their behavior and long term monitoring of these systems could lead to their design and maintenance optimization.</div><div>A new strain sensor for synthetic mooring lines is proposed in this paper. It uses an ultrasonic altimeter to measure the distance between the transducer and a target fixed on a synthetic mooring line. This instrument is non-intrusive and can be fixed on anchor lines after their installation at sea. The measurement principle and prototype design are presented. Then, the validation of the concept in a water tank is described, demonstrating the feasibility of measuring length using acoustic waves with a high degree of accuracy. The acoustic strain sensor was deployed in operational condition on a demonstrator buoy mooring line in the Mediterranean sea, together with a wire displacement sensor and a load sensor. The measurements from these three instruments are compared, showing the ability of the acoustic sensor to monitor the behavior of a mooring line at sea.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104398"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166956","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}
Pub Date : 2025-01-01DOI: 10.1016/j.apor.2025.104413
Alireza Ghorbanzadeh, Hodjat Shiri, Xiaoyu Dong
Ice gouging is a significant issue for offshore structures in cold environments. Pipelines in Arctic regions are buried in the seabed to prevent the direct contact of pipelines and the impacts of soil displacement from ice gouging. However, choosing the appropriate backfilling material and stiffness to maintain the pipeline's integrity while minimizing construction costs is a complex design consideration. It is crucial to accurately model the interaction between the ice, backfill, trench wall, and pipeline to assess the backfill functionality in a coupled ice gouging analysis. This study comprehensively investigated the effect of backfilling stiffness and configuration on seabed failure mechanisms and pipeline response during ice gouging events on a deeply buried pipeline. The study focused on six different backfill materials, including dense and loose sands and very soft clay to stiff clay. The Coupled Eulerian-Lagrangian (CEL) method was used to simulate the large seabed deformation due to the ice gouging process in a trenched/backfilled seabed in Abaqus/Explicit. Incorporation of the strain-rate dependency and strain-softening effects involved the development of a user-defined subroutine and incremental update of the undrained shear strength within the Abaqus software. Key findings reveal that both overly soft and excessively stiff backfill materials can negatively impact pipeline response during ice gouging. Very soft clay exhibits a distinct "removal" mechanism, leading to increased pipeline displacement, while overly stiff clay and dense sands result in more significant displacement due to efficient force transfer. The results can inform the selection of appropriate backfill materials and backfilling techniques to enhance pipeline protection against ice gouging.
{"title":"Effect of backfilling stiffness and configuration on seabed failure mechanisms and pipeline response to ice gouging","authors":"Alireza Ghorbanzadeh, Hodjat Shiri, Xiaoyu Dong","doi":"10.1016/j.apor.2025.104413","DOIUrl":"10.1016/j.apor.2025.104413","url":null,"abstract":"<div><div>Ice gouging is a significant issue for offshore structures in cold environments. Pipelines in Arctic regions are buried in the seabed to prevent the direct contact of pipelines and the impacts of soil displacement from ice gouging. However, choosing the appropriate backfilling material and stiffness to maintain the pipeline's integrity while minimizing construction costs is a complex design consideration. It is crucial to accurately model the interaction between the ice, backfill, trench wall, and pipeline to assess the backfill functionality in a coupled ice gouging analysis. This study comprehensively investigated the effect of backfilling stiffness and configuration on seabed failure mechanisms and pipeline response during ice gouging events on a deeply buried pipeline. The study focused on six different backfill materials, including dense and loose sands and very soft clay to stiff clay. The Coupled Eulerian-Lagrangian (CEL) method was used to simulate the large seabed deformation due to the ice gouging process in a trenched/backfilled seabed in Abaqus/Explicit. Incorporation of the strain-rate dependency and strain-softening effects involved the development of a user-defined subroutine and incremental update of the undrained shear strength within the Abaqus software. Key findings reveal that both overly soft and excessively stiff backfill materials can negatively impact pipeline response during ice gouging. Very soft clay exhibits a distinct \"removal\" mechanism, leading to increased pipeline displacement, while overly stiff clay and dense sands result in more significant displacement due to efficient force transfer. The results can inform the selection of appropriate backfill materials and backfilling techniques to enhance pipeline protection against ice gouging.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104413"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166957","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}
Pub Date : 2025-01-01DOI: 10.1016/j.apor.2024.104348
Andreas von Brandis , Daniel Menges , Adil Rasheed
Autonomous Surface Vessels (ASVs) rely on advanced perception algorithms to accurately represent internal and external conditions. One of the most challenging tasks is tracking surrounding objects, especially in the presence of model and measurement uncertainties. In case of multiple dynamic obstacles, the tracking problem becomes highly important to guarantee safe navigation. Therefore, we propose a multi-target tracking algorithm based on Light Detection And Ranging (LiDAR) and Automatic Identification System (AIS) data. To estimate the shape of other vessels, a Numerically Stable Direct Least-Squares (NSDLS) ellipse fitting algorithm is applied to LiDAR point clouds. For that purpose, the point clouds are separated into clusters using a modified version of Density-Based Spatial Clustering of Applications with Noise (DBSCAN). To improve the robustness of the tracking algorithm, the LiDAR-generated estimations are fused with AIS measurements using a Kalman Filter (KF). The motion model used for the KF enables the prediction of dynamic obstacles surrounding the ASV. This proactive awareness can be used for predictive control concepts such as Model Predictive Control. However, testing such advanced algorithms on real systems can be dangerous. A Digital Twin (DT) allows for an extendable integration of physics-based models, sensor data, and intelligent algorithms, enabling simulations in a safe environment. This work demonstrates the proposed multi-target tracking approach in a DT of an ASV, which contains vessel dynamics, sensor models, and real-world AIS data streams.
{"title":"Multi-Target Tracking for Autonomous Surface Vessels Using LiDAR and AIS Data Integration","authors":"Andreas von Brandis , Daniel Menges , Adil Rasheed","doi":"10.1016/j.apor.2024.104348","DOIUrl":"10.1016/j.apor.2024.104348","url":null,"abstract":"<div><div>Autonomous Surface Vessels (ASVs) rely on advanced perception algorithms to accurately represent internal and external conditions. One of the most challenging tasks is tracking surrounding objects, especially in the presence of model and measurement uncertainties. In case of multiple dynamic obstacles, the tracking problem becomes highly important to guarantee safe navigation. Therefore, we propose a multi-target tracking algorithm based on Light Detection And Ranging (LiDAR) and Automatic Identification System (AIS) data. To estimate the shape of other vessels, a Numerically Stable Direct Least-Squares (NSDLS) ellipse fitting algorithm is applied to LiDAR point clouds. For that purpose, the point clouds are separated into clusters using a modified version of Density-Based Spatial Clustering of Applications with Noise (DBSCAN). To improve the robustness of the tracking algorithm, the LiDAR-generated estimations are fused with AIS measurements using a Kalman Filter (KF). The motion model used for the KF enables the prediction of dynamic obstacles surrounding the ASV. This proactive awareness can be used for predictive control concepts such as Model Predictive Control. However, testing such advanced algorithms on real systems can be dangerous. A Digital Twin (DT) allows for an extendable integration of physics-based models, sensor data, and intelligent algorithms, enabling simulations in a safe environment. This work demonstrates the proposed multi-target tracking approach in a DT of an ASV, which contains vessel dynamics, sensor models, and real-world AIS data streams.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104348"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166998","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}
Pub Date : 2025-01-01DOI: 10.1016/j.apor.2024.104366
Peter Davies , Nicolas Lacotte , Gaspard Fourestier , Iroise Petton
Synthetic fibre ropes are increasingly popular for mooring lines of marine structures. The adoption of polyester ropes for deep water offshore platforms has resulted in a large material database, but the development of floating wind turbines has widened the scope to include more dynamic loadings and more compliant mooring lines are being developed. These are needed both for the turbines, particularly in shallow water, but also for the weather buoys which are used to obtain data on site conditions before wind park installation. This study has investigated the residual properties of weather buoy mooring lines based on hybrid fibres, polyester with polyolefin fibres. A set of lines was recovered from two shallow water sites after up to 2.5 years at sea. Significant loss of strength was measured after service, up to 50%. The reasons for this, mainly damage to external polyester fibres caused by mussel attachment, are discussed.
{"title":"Mechanical performance after service of hybrid synthetic mooring lines for weather buoys","authors":"Peter Davies , Nicolas Lacotte , Gaspard Fourestier , Iroise Petton","doi":"10.1016/j.apor.2024.104366","DOIUrl":"10.1016/j.apor.2024.104366","url":null,"abstract":"<div><div>Synthetic fibre ropes are increasingly popular for mooring lines of marine structures. The adoption of polyester ropes for deep water offshore platforms has resulted in a large material database, but the development of floating wind turbines has widened the scope to include more dynamic loadings and more compliant mooring lines are being developed. These are needed both for the turbines, particularly in shallow water, but also for the weather buoys which are used to obtain data on site conditions before wind park installation. This study has investigated the residual properties of weather buoy mooring lines based on hybrid fibres, polyester with polyolefin fibres. A set of lines was recovered from two shallow water sites after up to 2.5 years at sea. Significant loss of strength was measured after service, up to 50%. The reasons for this, mainly damage to external polyester fibres caused by mussel attachment, are discussed.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104366"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143167000","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}
Pub Date : 2025-01-01DOI: 10.1016/j.apor.2024.104411
Romain Hascoët, Nicolas Jacques
This study aims to investigate whether fatigue damage induced by bottom wave slamming can be a failure mode, important to consider when sizing a marine structural element. The body exposed to wave impacts is assumed to have a shape and structural arrangement such that the duration of wave-impact loads is short relative to the structure’s vibratory response time. In this dynamical regime, fatigue is found to be a potentially important failure mechanism: accounting for the risk of failure due to fatigue damage may result in design constraints that are significantly more conservative than those based on the risk of ultimate strength exceedance. The role of fatigue damage depends on the elevation of the body. It is predominant for low elevations, for which slamming events are frequent. Since this study aims to provide general insight, the specific details of the body, such as its shape and structural arrangement, are not specified. Instead, a general framework is used for the analysis. The way forward to address a specific case study, possibly including the effects of forward and seakeeping motions, is briefly explained.
{"title":"On the risk of fatigue failure of structural elements exposed to bottom wave slamming – Impulse response regime","authors":"Romain Hascoët, Nicolas Jacques","doi":"10.1016/j.apor.2024.104411","DOIUrl":"10.1016/j.apor.2024.104411","url":null,"abstract":"<div><div>This study aims to investigate whether fatigue damage induced by bottom wave slamming can be a failure mode, important to consider when sizing a marine structural element. The body exposed to wave impacts is assumed to have a shape and structural arrangement such that the duration of wave-impact loads is short relative to the structure’s vibratory response time. In this dynamical regime, fatigue is found to be a potentially important failure mechanism: accounting for the risk of failure due to fatigue damage may result in design constraints that are significantly more conservative than those based on the risk of ultimate strength exceedance. The role of fatigue damage depends on the elevation of the body. It is predominant for low elevations, for which slamming events are frequent. Since this study aims to provide general insight, the specific details of the body, such as its shape and structural arrangement, are not specified. Instead, a general framework is used for the analysis. The way forward to address a specific case study, possibly including the effects of forward and seakeeping motions, is briefly explained.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104411"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166401","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}
Pub Date : 2025-01-01DOI: 10.1016/j.apor.2024.104403
Van Suong Nguyen , Quang Duy Nguyen , Tuan Son Le , Hai Van Dang
In this study, a fixed-time adaptive radial basis function (RBF) neural network controller is proposed for ship roll stabilization, considering fixed-time convergence, the computational burden reduction, unknown dynamics, and external disturbances. First, the fixed-time stability theory is integrated with the backstepping method to design a controller for the ship's anti-roll fin stabilizers. With this controller, the errors of the closed-loop system are ensured to converge into the origin with faster convergent time. Moreover, the settling time of the system is independent from the initial states. Second, the unknown dynamics of the ship rolling model are estimated by the RBF neural network. To reduce the computational burden of the neural control system, the minimum learning parameter (MLP) technique is incorporated into the adaptive law of the RBF neural network. Based on the Lyapunov theory, the stability of a closed-loop system is proven to be guaranteed within a fixed time. Finally, numerical simulations and comparison analyses are performed to demonstrate the effectiveness and superiority of the proposed controller.
{"title":"Fixed-time adaptive RBF neural network controller via minimum learning parameter for ship roll stabilization","authors":"Van Suong Nguyen , Quang Duy Nguyen , Tuan Son Le , Hai Van Dang","doi":"10.1016/j.apor.2024.104403","DOIUrl":"10.1016/j.apor.2024.104403","url":null,"abstract":"<div><div>In this study, a fixed-time adaptive radial basis function (RBF) neural network controller is proposed for ship roll stabilization, considering fixed-time convergence, the computational burden reduction, unknown dynamics, and external disturbances. First, the fixed-time stability theory is integrated with the backstepping method to design a controller for the ship's anti-roll fin stabilizers. With this controller, the errors of the closed-loop system are ensured to converge into the origin with faster convergent time. Moreover, the settling time of the system is independent from the initial states. Second, the unknown dynamics of the ship rolling model are estimated by the RBF neural network. To reduce the computational burden of the neural control system, the minimum learning parameter (MLP) technique is incorporated into the adaptive law of the RBF neural network. Based on the Lyapunov theory, the stability of a closed-loop system is proven to be guaranteed within a fixed time. Finally, numerical simulations and comparison analyses are performed to demonstrate the effectiveness and superiority of the proposed controller.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"154 ","pages":"Article 104403"},"PeriodicalIF":4.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166403","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}
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