Pub Date : 2025-10-30DOI: 10.1016/j.marstruc.2025.103959
Guy McCauley, Hugh Wolgamot, Paul H. Taylor, Jana Orszaghova
The relationship between measured tower bending moments and motions of the TetraSpar Demonstrator floating offshore wind turbine is assessed using conditioning analysis techniques for an extreme storm event, and indicates that the motion to moment transfer function is linear, but dependent on turbine state and wind speed. Using measured motions and bending moments, a look-up table of linear transfer functions is generated for different turbine speed and wind speed bins. The look-up table is then used to predict tower bending moment from measured motions for a winter period, and the accuracy of the predictions is assessed. Finally, predicted stress from the linear transfer function method is used to calculate fatigue damage, which compares well to fatigue calculated using measured bending moments.
{"title":"From motion to moments: conditioning analysis of floating offshore wind turbine tower bending","authors":"Guy McCauley, Hugh Wolgamot, Paul H. Taylor, Jana Orszaghova","doi":"10.1016/j.marstruc.2025.103959","DOIUrl":"10.1016/j.marstruc.2025.103959","url":null,"abstract":"<div><div>The relationship between measured tower bending moments and motions of the TetraSpar Demonstrator floating offshore wind turbine is assessed using conditioning analysis techniques for an extreme storm event, and indicates that the motion to moment transfer function is linear, but dependent on turbine state and wind speed. Using measured motions and bending moments, a look-up table of linear transfer functions is generated for different turbine speed and wind speed bins. The look-up table is then used to predict tower bending moment from measured motions for a winter period, and the accuracy of the predictions is assessed. Finally, predicted stress from the linear transfer function method is used to calculate fatigue damage, which compares well to fatigue calculated using measured bending moments.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"106 ","pages":"Article 103959"},"PeriodicalIF":5.1,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145416840","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}
Pub Date : 2025-10-27DOI: 10.1016/j.marstruc.2025.103957
Wei Cheng , Yun Gao , Conghe Shi , Chen Shi
The dynamic response characteristics of a submerged floating tunnel (SFT) under pure wave loads, pure current loads, and combined wave-current loads were studied using the two-dimensional unsteady Reynolds-averaged Navier-Stokes equations and the shear stress transport k-ω model coupled with the fourth-order Runge-Kutta method. The hydrodynamic forces acting on the SFT, and its motion response characteristics, including vibration amplitude, displacement frequency, and vibration trajectory, were systematically analyzed and discussed. The numerical results showed that, for the design parameters of the SFT selected in this study, when only a wave load was considered, the vibration amplitude of the SFT tube increased as the wave height increased, however, it decreased as the wave period increased. The displacement frequency remained consistent with the wave frequency. When only a current load was considered, the motion response of the SFT tube in the sway direction displayed multi-frequency characteristics, with the dominant frequency in the sway direction being approximately twice that in the heave direction. When a combined wave-current load was considered, for a low current velocity, the displacement frequency response of the SFT body in the heave direction was dominated by the wave load, while for a high current velocity, it was dominated by the wave and current loads simultaneously. Furthermore, for a low current velocity, the coupling effect between the wave and current loads was slight. However, as the current velocity increased to 2.5 m s-1, the wave-current coupling effect became obviously pronounced and non-negligible.
采用二维非定常雷诺数-平均Navier-Stokes方程和四阶龙格-库塔方法耦合的剪切应力输运k-ω模型，研究了纯波浪荷载、纯电流荷载和波流复合荷载作用下沉浮隧道的动力响应特性。系统地分析和讨论了作用在SFT上的水动力力及其运动响应特性，包括振动幅值、位移频率和振动轨迹。数值结果表明，对于本研究选取的SFT设计参数，当仅考虑波浪荷载时，SFT管的振动幅值随波高的增加而增大，随波周期的增加而减小。位移频率与波浪频率保持一致。仅考虑电流载荷时，SFT管在摇摆方向的运动响应呈现多频特性，摇摆方向的主导频率约为升沉方向的两倍。考虑波流复合载荷时，当电流速度较低时，SFT体在升沉方向的位移频率响应以波浪载荷为主，而当电流速度较大时，SFT体在升沉方向的位移频率响应同时由波浪和电流载荷主导。此外，当电流速度较低时，波浪和电流负载之间的耦合效应较小。然而，当电流速度增加到2.5 m s-1时，波流耦合效应变得明显且不可忽略。
{"title":"Numerical investigation of the dynamic response characteristics of a submerged floating tunnel tube under wave and current loads","authors":"Wei Cheng , Yun Gao , Conghe Shi , Chen Shi","doi":"10.1016/j.marstruc.2025.103957","DOIUrl":"10.1016/j.marstruc.2025.103957","url":null,"abstract":"<div><div>The dynamic response characteristics of a submerged floating tunnel (SFT) under pure wave loads, pure current loads, and combined wave-current loads were studied using the two-dimensional unsteady Reynolds-averaged Navier-Stokes equations and the shear stress transport <em>k</em>-<em>ω</em> model coupled with the fourth-order Runge-Kutta method. The hydrodynamic forces acting on the SFT, and its motion response characteristics, including vibration amplitude, displacement frequency, and vibration trajectory, were systematically analyzed and discussed. The numerical results showed that, for the design parameters of the SFT selected in this study, when only a wave load was considered, the vibration amplitude of the SFT tube increased as the wave height increased, however, it decreased as the wave period increased. The displacement frequency remained consistent with the wave frequency. When only a current load was considered, the motion response of the SFT tube in the sway direction displayed multi-frequency characteristics, with the dominant frequency in the sway direction being approximately twice that in the heave direction. When a combined wave-current load was considered, for a low current velocity, the displacement frequency response of the SFT body in the heave direction was dominated by the wave load, while for a high current velocity, it was dominated by the wave and current loads simultaneously. Furthermore, for a low current velocity, the coupling effect between the wave and current loads was slight. However, as the current velocity increased to 2.5 m s<sup>-1</sup>, the wave-current coupling effect became obviously pronounced and non-negligible.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"106 ","pages":"Article 103957"},"PeriodicalIF":5.1,"publicationDate":"2025-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145416841","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}
Pub Date : 2025-10-23DOI: 10.1016/j.marstruc.2025.103956
Youhai Guan , Kaixin Liang , Jincheng Hu , Huanyu Lv , Zhaohui Yang , Bo Wang , Meng Zhao , Shaojian Liu , Zhe Wang
Local scour constitutes a critical threat to structural safety of offshore suction bucket foundations, while conventional countermeasures demonstrate constrained efficacy. To mitigate scour depths around suction bucket foundations, flowable stabilized soil (FSS) was applied to the upper seabed layer adjacent to structures. Flume experiments under steady current conditions were conducted to evaluate scour characteristics of tripod suction bucket foundations with versus without FSS protection. Results indicate that FSS exhibits significantly higher compressive and shear strength than natural seabed, characterized by densely compacted microstructure. Scour patterns for FSS under varied protection radii were categorized as "joint erosion" and "surface erosion". A correction coefficient for horseshoe vortex intensity was incorporated based on energy conservation theory, while the equilibrium scour depth formula was refined to account for FSS influences. Under identical conditions, FSS protection demonstrates superior efficiency relative to riprap and collar devices, with lower costs and simpler construction than grouting methods, empirically validating its enhanced scour mitigation capabilities.
{"title":"Experimental study on flowable solidified soil for scour protection of tripod suction bucket foundations in offshore wind farms","authors":"Youhai Guan , Kaixin Liang , Jincheng Hu , Huanyu Lv , Zhaohui Yang , Bo Wang , Meng Zhao , Shaojian Liu , Zhe Wang","doi":"10.1016/j.marstruc.2025.103956","DOIUrl":"10.1016/j.marstruc.2025.103956","url":null,"abstract":"<div><div>Local scour constitutes a critical threat to structural safety of offshore suction bucket foundations, while conventional countermeasures demonstrate constrained efficacy. To mitigate scour depths around suction bucket foundations, flowable stabilized soil (FSS) was applied to the upper seabed layer adjacent to structures. Flume experiments under steady current conditions were conducted to evaluate scour characteristics of tripod suction bucket foundations with versus without FSS protection. Results indicate that FSS exhibits significantly higher compressive and shear strength than natural seabed, characterized by densely compacted microstructure. Scour patterns for FSS under varied protection radii were categorized as \"joint erosion\" and \"surface erosion\". A correction coefficient for horseshoe vortex intensity was incorporated based on energy conservation theory, while the equilibrium scour depth formula was refined to account for FSS influences. Under identical conditions, FSS protection demonstrates superior efficiency relative to riprap and collar devices, with lower costs and simpler construction than grouting methods, empirically validating its enhanced scour mitigation capabilities.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"106 ","pages":"Article 103956"},"PeriodicalIF":5.1,"publicationDate":"2025-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145362674","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}
This study evaluates an efficient time-domain fatigue analysis approach for welded joints in semi-submersible floating wind turbine (FWT) hulls. A fully coupled, time domain approach serves as reference for comparing simplified methods. In particular, a simplified decoupled method in which the global load effects due to wind and waves are determined separately and the corresponding hot spot stress for estimating the fatigue damage in representative points is determined by superimposing the time series of the stress due to global wave and wind effects. A 10-MW semi-submersible FWT at various North Sea and China offshore locations, is analyzed employing a multi-segment floater model to capture global structural responses. Fatigue damage of various positions of the hull is estimated using the rainflow cycle counting method and the SN-curve approach. The results indicate that the fully coupled method, while highly accurate in capturing real-time wind-wave interactions, implies significant computational costs. The decoupled approach enhances the efficiency and reduces the simulation requirements by over 80 %, while maintaining a reasonable accuracy, particularly for wind turbines in the Northern North Sea, i.e., with a deviation of <12 %. In addition, a highly simplified method is proposed, which is based on considering only the most probable wave conditions at different wind speeds. This method shows good agreement with fully coupled fatigue assessments in the Northern North Sea, but it leads to notable underestimation in the South China Sea. However, further investigations of this approach are needed to document its feasibility. The findings in this study highlight the trade-offs between computational cost and accuracy, and especially shows the potential of the decoupled method for an efficient long-term fatigue assessment of floating wind turbines. Future research should be carried out to document its applicability for various floating wind turbine designs and offshore locations.
{"title":"An efficient approach for time-domain fatigue analysis for semi-submersible hulls of floating wind turbines","authors":"Shuaishuai Wang , Torgeir Moan , Zhen Gao , Shan Gao","doi":"10.1016/j.marstruc.2025.103955","DOIUrl":"10.1016/j.marstruc.2025.103955","url":null,"abstract":"<div><div>This study evaluates an efficient time-domain fatigue analysis approach for welded joints in semi-submersible floating wind turbine (FWT) hulls. A fully coupled, time domain approach serves as reference for comparing simplified methods. In particular, a simplified decoupled method in which the global load effects due to wind and waves are determined separately and the corresponding hot spot stress for estimating the fatigue damage in representative points is determined by superimposing the time series of the stress due to global wave and wind effects. A 10-MW semi-submersible FWT at various North Sea and China offshore locations, is analyzed employing a multi-segment floater model to capture global structural responses. Fatigue damage of various positions of the hull is estimated using the rainflow cycle counting method and the SN-curve approach. The results indicate that the fully coupled method, while highly accurate in capturing real-time wind-wave interactions, implies significant computational costs. The decoupled approach enhances the efficiency and reduces the simulation requirements by over 80 %, while maintaining a reasonable accuracy, particularly for wind turbines in the Northern North Sea, i.e., with a deviation of <12 %. In addition, a highly simplified method is proposed, which is based on considering only the most probable wave conditions at different wind speeds. This method shows good agreement with fully coupled fatigue assessments in the Northern North Sea, but it leads to notable underestimation in the South China Sea. However, further investigations of this approach are needed to document its feasibility. The findings in this study highlight the trade-offs between computational cost and accuracy, and especially shows the potential of the decoupled method for an efficient long-term fatigue assessment of floating wind turbines. Future research should be carried out to document its applicability for various floating wind turbine designs and offshore locations.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"106 ","pages":"Article 103955"},"PeriodicalIF":5.1,"publicationDate":"2025-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145362649","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}
Pub Date : 2025-10-15DOI: 10.1016/j.marstruc.2025.103950
Malcolm Smith , Ken Nahshon , Teresa Magoga , Joel Hogan , Rachel Markert , Joel Higgins
A deck grillage structure was extracted from a decommissioned warship (ex-HMCS IROQUOIS) and damaged as the result of a dynamic pressure loading test, resulting in overall permanent multi-bay deformation of the plating and attached members. The damaged grillage was then re-configured for residual ultimate strength testing under longitudinal loading. The test article spanned three complete frame bays plus half-bays at each end and four continuous longitudinals of the original structure. In addition to thickness and material property measurements, Light Detection and Ranging (LiDAR) measurement of the damaged panel was carried out after re-configuration. The residual strength testing consisted of compressive loading to collapse and post-collapse, followed by two tension-compression cycles. Numerical assessments of the residual strength were performed using nonlinear finite element analysis (FEA) and material models based on measured material properties from material recovered from the ship. Excellent agreement is achieved between the measured and predicted load-shortening behaviour through progressive adjustment of the material modelling parameters. The deformation damage is estimated to result in a 20.7% loss of ultimate strength. The modelling approach developed here is then extended to the analysis of four previously-studied grillage structures recovered from the same vessel.
{"title":"Residual ultimate strength of a damaged deck grillage structure","authors":"Malcolm Smith , Ken Nahshon , Teresa Magoga , Joel Hogan , Rachel Markert , Joel Higgins","doi":"10.1016/j.marstruc.2025.103950","DOIUrl":"10.1016/j.marstruc.2025.103950","url":null,"abstract":"<div><div>A deck grillage structure was extracted from a decommissioned warship (ex-HMCS IROQUOIS) and damaged as the result of a dynamic pressure loading test, resulting in overall permanent multi-bay deformation of the plating and attached members. The damaged grillage was then re-configured for residual ultimate strength testing under longitudinal loading. The test article spanned three complete frame bays plus half-bays at each end and four continuous longitudinals of the original structure. In addition to thickness and material property measurements, Light Detection and Ranging (LiDAR) measurement of the damaged panel was carried out after re-configuration. The residual strength testing consisted of compressive loading to collapse and post-collapse, followed by two tension-compression cycles. Numerical assessments of the residual strength were performed using nonlinear finite element analysis (FEA) and material models based on measured material properties from material recovered from the ship. Excellent agreement is achieved between the measured and predicted load-shortening behaviour through progressive adjustment of the material modelling parameters. The deformation damage is estimated to result in a 20.7% loss of ultimate strength. The modelling approach developed here is then extended to the analysis of four previously-studied grillage structures recovered from the same vessel.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"106 ","pages":"Article 103950"},"PeriodicalIF":5.1,"publicationDate":"2025-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145324375","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}
Pub Date : 2025-10-10DOI: 10.1016/j.marstruc.2025.103953
Zhiquan Zhou , Jiasong Wang
The stability of wake oscillator model prediction accuracy across varying conditions is a critical and widely studied topic. This study developed a wake oscillator model incorporating newly fitted Van der Pol parameters, derived through mathematical derivation coupled with experimental fitting. The model comprises structural dynamic equations and Van der Pol oscillators in the in-line and cross-flow directions, solved numerically via the central difference method. Comparison with several classical experimental data and other numerical studies illustrates the enhanced comprehensive accuracy of the model. Particularly, this modification effectively addresses the common underestimation of in-line amplitudes and maintains consistent performance across diverse operating conditions. Investigation of the vortex-induced vibrations in the deep-sea mining riser reveals that the application of the new parameters magnifies the vibration amplitude, especially the peaks. The phenomenon arises from localized energy accumulation and reduced phase velocity. The model effectively enhances the higher-order frequency components and modifies the sidelobe width of the dominant vibration frequency, preventing the occurrence of unforeseen resonance. Those variations are amplified as the flow velocity increases. The static displacement of the riser, governed by the mean drag coefficient, remains unaffected. This improvement establishes a foundation for predicting vortex-induced vibrations responses and ensuring operational safety of deep-sea mining risers.
{"title":"Newly fitted Van der Pol parameters for vortex-induced vibration and their application to a deep-sea mining riser","authors":"Zhiquan Zhou , Jiasong Wang","doi":"10.1016/j.marstruc.2025.103953","DOIUrl":"10.1016/j.marstruc.2025.103953","url":null,"abstract":"<div><div>The stability of wake oscillator model prediction accuracy across varying conditions is a critical and widely studied topic. This study developed a wake oscillator model incorporating newly fitted Van der Pol parameters, derived through mathematical derivation coupled with experimental fitting. The model comprises structural dynamic equations and Van der Pol oscillators in the in-line and cross-flow directions, solved numerically via the central difference method. Comparison with several classical experimental data and other numerical studies illustrates the enhanced comprehensive accuracy of the model. Particularly, this modification effectively addresses the common underestimation of in-line amplitudes and maintains consistent performance across diverse operating conditions. Investigation of the vortex-induced vibrations in the deep-sea mining riser reveals that the application of the new parameters magnifies the vibration amplitude, especially the peaks. The phenomenon arises from localized energy accumulation and reduced phase velocity. The model effectively enhances the higher-order frequency components and modifies the sidelobe width of the dominant vibration frequency, preventing the occurrence of unforeseen resonance. Those variations are amplified as the flow velocity increases. The static displacement of the riser, governed by the mean drag coefficient, remains unaffected. This improvement establishes a foundation for predicting vortex-induced vibrations responses and ensuring operational safety of deep-sea mining risers.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"106 ","pages":"Article 103953"},"PeriodicalIF":5.1,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145266948","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}
Pub Date : 2025-10-09DOI: 10.1016/j.marstruc.2025.103949
Hongyan Ding , Tingyuan Wang , Conghuan Le , Yunlong Xu , Puyang Zhang
To address the challenges of penetration attitude control caused by eccentric loads during the integrated penetration of composite bucket foundations for offshore wind power, this study combines model tests and numerical simulations to systematically investigate the penetration characteristics, seepage field evolution, and critical suction mechanism under eccentric loads. The effects of different eccentric load magnitudes and positions on penetration characteristics were analyzed. Results show that increasing eccentric loads reduces penetration resistance (about 15 % lower than the non-eccentric case), and applying the load directly above a single compartment enhances installation stability through a three-compartment compensation strategy. The study reveals the asymmetric distribution of excess pore water pressure in the soil under eccentric loads, with the negative pore pressure loss at the outer wall of the compensation compartment reduced by approximately 20 % compared to the non-compensation compartment. Critical seepage failure occurs at the interface between the non-compensation compartments and the partition plates. Based on the relationship between seepage paths and pressure differences, a critical suction formula is derived, considering the number of compensation compartments, pressure differences, and penetration depth. The results show that eccentric loads lead to a maximum reduction of 17.56 % in critical suction. This study provides theoretical support and engineering guidance for efficiently installing composite bucket foundations in offshore wind power applications.
{"title":"Penetration characteristics of composite bucket foundations under eccentric loads during integrated offshore wind turbine installation","authors":"Hongyan Ding , Tingyuan Wang , Conghuan Le , Yunlong Xu , Puyang Zhang","doi":"10.1016/j.marstruc.2025.103949","DOIUrl":"10.1016/j.marstruc.2025.103949","url":null,"abstract":"<div><div>To address the challenges of penetration attitude control caused by eccentric loads during the integrated penetration of composite bucket foundations for offshore wind power, this study combines model tests and numerical simulations to systematically investigate the penetration characteristics, seepage field evolution, and critical suction mechanism under eccentric loads. The effects of different eccentric load magnitudes and positions on penetration characteristics were analyzed. Results show that increasing eccentric loads reduces penetration resistance (about 15 % lower than the non-eccentric case), and applying the load directly above a single compartment enhances installation stability through a three-compartment compensation strategy. The study reveals the asymmetric distribution of excess pore water pressure in the soil under eccentric loads, with the negative pore pressure loss at the outer wall of the compensation compartment reduced by approximately 20 % compared to the non-compensation compartment. Critical seepage failure occurs at the interface between the non-compensation compartments and the partition plates. Based on the relationship between seepage paths and pressure differences, a critical suction formula is derived, considering the number of compensation compartments, pressure differences, and penetration depth. The results show that eccentric loads lead to a maximum reduction of 17.56 % in critical suction. This study provides theoretical support and engineering guidance for efficiently installing composite bucket foundations in offshore wind power applications.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"106 ","pages":"Article 103949"},"PeriodicalIF":5.1,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267883","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}
Pub Date : 2025-10-08DOI: 10.1016/j.marstruc.2025.103948
Haonan Tian , Mohsen N. Soltani , Oriol Colomés
Mooring failures significantly threaten the stability of Floating Offshore Wind Turbines (FOWT) under extreme environmental conditions. This study presents an innovative integrated damping mooring system incorporating Seaflex dampers to improve structural stability and operational reliability. Dynamic simulations under 1-year and 50-year return period sea states demonstrate the system’s effectiveness. Under Ultimate Limit State (ULS) conditions, the system reduces surge displacement by 59%, pitch angle by 47%, and mooring line tension by 72%. Under Accidental Limit State (ALS) conditions, it mitigates load spikes, reduces drift displacement by 60%, and improves safety factors by 50%. The comparison shows chain and wire rope configurations have better load reduction performance in the integrated damping scheme. Lightweight and adaptable, the Seaflex dampers enhance broad-spectrum damping without affecting platform buoyancy. This study offers a robust solution for enhancing FOWT safety and durability in harsh marine environments, thereby enabling large-scale offshore wind energy development.
{"title":"Innovative integrated damping mooring technology for floating wind turbines under extreme sea conditions","authors":"Haonan Tian , Mohsen N. Soltani , Oriol Colomés","doi":"10.1016/j.marstruc.2025.103948","DOIUrl":"10.1016/j.marstruc.2025.103948","url":null,"abstract":"<div><div>Mooring failures significantly threaten the stability of Floating Offshore Wind Turbines (FOWT) under extreme environmental conditions. This study presents an innovative integrated damping mooring system incorporating Seaflex dampers to improve structural stability and operational reliability. Dynamic simulations under 1-year and 50-year return period sea states demonstrate the system’s effectiveness. Under Ultimate Limit State (ULS) conditions, the system reduces surge displacement by 59%, pitch angle by 47%, and mooring line tension by 72%. Under Accidental Limit State (ALS) conditions, it mitigates load spikes, reduces drift displacement by 60%, and improves safety factors by 50%. The comparison shows chain and wire rope configurations have better load reduction performance in the integrated damping scheme. Lightweight and adaptable, the Seaflex dampers enhance broad-spectrum damping without affecting platform buoyancy. This study offers a robust solution for enhancing FOWT safety and durability in harsh marine environments, thereby enabling large-scale offshore wind energy development.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"106 ","pages":"Article 103948"},"PeriodicalIF":5.1,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145266950","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}
Pub Date : 2025-10-08DOI: 10.1016/j.marstruc.2025.103951
Peter J. Rohrer , Erin E. Bachynski-Polić , John Marius Hegseth
A wide variety of semi-submersible floating wind turbine designs have been proposed, though few studies have attempted design optimization with more than a handful of design variables. Gradient-based design optimization can enable optimization with many design variables to define the tower, substructure, and structural scantling design and allow for the inclusion of increasingly realistic design constraints based on ultimate and fatigue limit states of the structure. A surrogate-assisted optimization model centered around a linearized frequency-domain aero-hydro-servo-elastic model of a semi-submersible wind turbine was developed and applied to find optimal designs in three hypothetical locations. The optimal designs vary significantly based on the environmental conditions, and show the potential for significant cost-savings by employing site-specific design for floating wind turbines. For all of the hypothetical locations considered here, the tower design is driven by fatigue damage in near-rated wind speed conditions at the tower base and top, and buckling utilization in the rated-wind speed extreme condition for the remaining tower sections. The substructure design is driven by fatigue damage in near-rated wind speed conditions for the central column and above-rated wind speed conditions for the pontoons. Rules-based buckling constraints in the rated-wind speed condition drive the outer column and scantling design. The optimization model has also been used to investigate the impact of the bounds on tower design variables on the integrated tower-substructure structural design, and has the potential to be adapted to help answer a range of other concept-level design questions.
{"title":"Gradient-based design optimization of semi-submersible floating wind turbines","authors":"Peter J. Rohrer , Erin E. Bachynski-Polić , John Marius Hegseth","doi":"10.1016/j.marstruc.2025.103951","DOIUrl":"10.1016/j.marstruc.2025.103951","url":null,"abstract":"<div><div>A wide variety of semi-submersible floating wind turbine designs have been proposed, though few studies have attempted design optimization with more than a handful of design variables. Gradient-based design optimization can enable optimization with many design variables to define the tower, substructure, and structural scantling design and allow for the inclusion of increasingly realistic design constraints based on ultimate and fatigue limit states of the structure. A surrogate-assisted optimization model centered around a linearized frequency-domain aero-hydro-servo-elastic model of a semi-submersible wind turbine was developed and applied to find optimal designs in three hypothetical locations. The optimal designs vary significantly based on the environmental conditions, and show the potential for significant cost-savings by employing site-specific design for floating wind turbines. For all of the hypothetical locations considered here, the tower design is driven by fatigue damage in near-rated wind speed conditions at the tower base and top, and buckling utilization in the rated-wind speed extreme condition for the remaining tower sections. The substructure design is driven by fatigue damage in near-rated wind speed conditions for the central column and above-rated wind speed conditions for the pontoons. Rules-based buckling constraints in the rated-wind speed condition drive the outer column and scantling design. The optimization model has also been used to investigate the impact of the bounds on tower design variables on the integrated tower-substructure structural design, and has the potential to be adapted to help answer a range of other concept-level design questions.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"106 ","pages":"Article 103951"},"PeriodicalIF":5.1,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145266947","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}
Pub Date : 2025-10-07DOI: 10.1016/j.marstruc.2025.103952
Jinming Tu , Fan Yang , Donghua Liu , Yunsong Ji , Chengchao Guo , Fuming Wang
Local scour around the semiconical structure of a monopile was systematically studied considering the side slope angle (α = 0°–60°), protruding height (E/d = 0–2), and flow intensity (clear-water or live-bed flow conditions). The three-dimensional scour profiles and features were meticulously explored using flow visualizations through large-eddy simulations. As the semiconical structure was buried in the seabed (E/d = 0), increasing side slope angle α from 0° to 60° reduced the maximum scour depth Smax by 53 % compared with the results of the monopile without the countermeasure. At E/d = 2, the maximum scour depth occurred at the downstream edge for α ≥ 30°, while the scour upstream was significantly diminished. Smax decreased significantly with an increase in α. At α = 60°, the reduction of Smax is up to 100 %. Vortex shedding also diminished owing to the semiconical structure. An increase in E led to a reduction in Smax, while the flow intensity had a limited impact. An equation for predicting scour-protection efficiency was derived from experimental results; it shows good predictive performance, with errors within 20 %.
{"title":"Local scour around a monopile using semiconical protection in a steady current","authors":"Jinming Tu , Fan Yang , Donghua Liu , Yunsong Ji , Chengchao Guo , Fuming Wang","doi":"10.1016/j.marstruc.2025.103952","DOIUrl":"10.1016/j.marstruc.2025.103952","url":null,"abstract":"<div><div>Local scour around the semiconical structure of a monopile was systematically studied considering the side slope angle (<em>α</em> = 0°–60°), protruding height (<em>E/d</em> = 0–2), and flow intensity (clear-water or live-bed flow conditions). The three-dimensional scour profiles and features were meticulously explored using flow visualizations through large-eddy simulations. As the semiconical structure was buried in the seabed (<em>E/d</em> = 0), increasing side slope angle α from 0° to 60° reduced the maximum scour depth <em>S<sub>max</sub></em> by 53 % compared with the results of the monopile without the countermeasure. At <em>E/d</em> = 2, the maximum scour depth occurred at the downstream edge for <em>α</em> ≥ 30°, while the scour upstream was significantly diminished. <em>S<sub>max</sub></em> decreased significantly with an increase in <em>α</em>. At <em>α</em> = 60°, the reduction of <em>S<sub>max</sub></em> is up to 100 %. Vortex shedding also diminished owing to the semiconical structure. An increase in <em>E</em> led to a reduction in <em>S<sub>max</sub></em>, while the flow intensity had a limited impact. An equation for predicting scour-protection efficiency was derived from experimental results; it shows good predictive performance, with errors within 20 %.</div></div>","PeriodicalId":49879,"journal":{"name":"Marine Structures","volume":"106 ","pages":"Article 103952"},"PeriodicalIF":5.1,"publicationDate":"2025-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145266949","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}
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