Pub Date : 2025-02-01DOI: 10.1016/j.apor.2025.104433
Xin Liao, Chan Ghee Koh, Yean Khow Chow
A hybrid strategy combining the advantages of the meshless Consistent Particle Method (CPM) and the mesh-based Finite Element Method (FEM) is proposed in this paper to solve fluid-structure interaction problems. Water is modelled by CPM, whereas deformable structure is solved by FEM. Unlike some traditional particle methods that require a kernel function in computing spatial derivatives, CPM utilizes Taylor series expansion and avoids the use of artificial values of physical parameters (such as artificial viscosity and sound speed). The interaction between water and structure is achieved by a partitioned approach for its flexibility and ease of implementation. To ensure compatibility between CPM and FEM solutions at the fluid-structure interface, an iteration scheme of enforcing pressure Poisson equation (PPE) is proposed. The accuracy and stability of the proposed hybrid strategy are validated through three benchmark examples: water column on an elastic plate, sloshing of sunflower oil interacting with an elastic baffle, and a dam break with an elastic gate. Comparisons between CPM-FEM results with published experimental and numerical results demonstrate the effectiveness and advantages of the proposed hybrid strategy.
{"title":"A hybrid strategy for numerical simulations of fluid-structure interaction problems in ocean engineering","authors":"Xin Liao, Chan Ghee Koh, Yean Khow Chow","doi":"10.1016/j.apor.2025.104433","DOIUrl":"10.1016/j.apor.2025.104433","url":null,"abstract":"<div><div>A hybrid strategy combining the advantages of the meshless Consistent Particle Method (CPM) and the mesh-based Finite Element Method (FEM) is proposed in this paper to solve fluid-structure interaction problems. Water is modelled by CPM, whereas deformable structure is solved by FEM. Unlike some traditional particle methods that require a kernel function in computing spatial derivatives, CPM utilizes Taylor series expansion and avoids the use of artificial values of physical parameters (such as artificial viscosity and sound speed). The interaction between water and structure is achieved by a partitioned approach for its flexibility and ease of implementation. To ensure compatibility between CPM and FEM solutions at the fluid-structure interface, an iteration scheme of enforcing pressure Poisson equation (PPE) is proposed. The accuracy and stability of the proposed hybrid strategy are validated through three benchmark examples: water column on an elastic plate, sloshing of sunflower oil interacting with an elastic baffle, and a dam break with an elastic gate. Comparisons between CPM-FEM results with published experimental and numerical results demonstrate the effectiveness and advantages of the proposed hybrid strategy.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"155 ","pages":"Article 104433"},"PeriodicalIF":4.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143176385","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 : 2025-02-01DOI: 10.1016/j.apor.2025.104419
Hongkuan Yang , Lizhong Wang , Zhenming Lei , Shengjie Rui , Zhenyu Liu , Zhen Guo
The lateral pipe-soil interaction in sloping ground is numerically simulated, with a modified Mohr-Coulomb model adopted to capture the state-dependent behavior of dense sand. The numerical model is first validated by previous physical tests in level ground. Then, both peak and residual lateral resistance are investigated in nonpositive slopes (pipeline moves relatively outwards the slope), while only the former is focused in opposite cases. The effects of burial depth ratio, interface roughness and slope angle on soil resistances are specially discussed. It is found that in terms of the failure mechanisms, increasing the slope angle implies to some extent an increase of burial depth ratio in level ground. A positive slope usually provides higher soil resistance than a negative slope for a given burial depth ratio as the normalized normal pipe-soil contact stress on the pulling side increases with the slope angle. The difference in peak resistance between the perfectly smooth and generally rough pipeline is amplified in positive slopes, which is associated with the transition of the failure mechanisms. Finally, a preliminary methodology to evaluate the soil resistances in sloping ground is presented, based on the improved implicit limit equilibrium method for level ground and newly proposed slope effect coefficients.
{"title":"Numerical study of lateral soil resistance to pipe movement in sandy slopes","authors":"Hongkuan Yang , Lizhong Wang , Zhenming Lei , Shengjie Rui , Zhenyu Liu , Zhen Guo","doi":"10.1016/j.apor.2025.104419","DOIUrl":"10.1016/j.apor.2025.104419","url":null,"abstract":"<div><div>The lateral pipe-soil interaction in sloping ground is numerically simulated, with a modified Mohr-Coulomb model adopted to capture the state-dependent behavior of dense sand. The numerical model is first validated by previous physical tests in level ground. Then, both peak and residual lateral resistance are investigated in nonpositive slopes (pipeline moves relatively outwards the slope), while only the former is focused in opposite cases. The effects of burial depth ratio, interface roughness and slope angle on soil resistances are specially discussed. It is found that in terms of the failure mechanisms, increasing the slope angle implies to some extent an increase of burial depth ratio in level ground. A positive slope usually provides higher soil resistance than a negative slope for a given burial depth ratio as the normalized normal pipe-soil contact stress on the pulling side increases with the slope angle. The difference in peak resistance between the perfectly smooth and generally rough pipeline is amplified in positive slopes, which is associated with the transition of the failure mechanisms. Finally, a preliminary methodology to evaluate the soil resistances in sloping ground is presented, based on the improved implicit limit equilibrium method for level ground and newly proposed slope effect coefficients.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"155 ","pages":"Article 104419"},"PeriodicalIF":4.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143176386","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 : 2025-02-01DOI: 10.1016/j.apor.2025.104437
Lin-fang Xu , Zhi-hui Wan , Guo-liang Dai , Tao Hu , Feng Zhou , Chun-hui Bao
The bearing behaviors of post-grouted piles for offshore wind turbines are significantly affected by the grouting effect, especially in heavily weathered granite, which has attracted considerable attention in the academic community. This paper presents field static load tests on a large-diameter steel-concrete composite pile for offshore wind turbine foundations in deeply weathered granite formations. The influence of combined end-and-side grouting on the bearing behaviors of large-diameter steel-concrete composite piles in heavily weathered granite was thoroughly investigated through core drilling and CT scanning. Furthermore, numerical simulations were employed to conduct a parametric analysis of the combined post-grouting of large-diameter steel-concrete composite piles in heavily weathered granite formations, systematically studying the influence of grouting pressure and grouting volume on the bearing properties of post-grouted piles. The results indicated that compared to that before combined grouting, the bearing capacity of large-diameter steel-concrete piles is effectively enhanced after combined grouting. Core drilling clearly revealed the distribution of cement grout around and below the pile, indicating that the influence range of cement grout in heavily weathered granite formations extends from 0.5D below the pile tip to 5.3D above the pile tip. CT scanning results confirmed that cement grout could form cementation in heavily weathered granite, validating the effectiveness of combined post-grouting in such formations. The findings can serve as a reference for evaluating the grouting effect of post-grouted piles and contribute to advancing the application of post-grouted piles in heavily weathered rock formations.
{"title":"Full-scale field investigations and numerical analyses of grouting effect for large-diameter steel-concrete composite piles in offshore wind turbines","authors":"Lin-fang Xu , Zhi-hui Wan , Guo-liang Dai , Tao Hu , Feng Zhou , Chun-hui Bao","doi":"10.1016/j.apor.2025.104437","DOIUrl":"10.1016/j.apor.2025.104437","url":null,"abstract":"<div><div>The bearing behaviors of post-grouted piles for offshore wind turbines are significantly affected by the grouting effect, especially in heavily weathered granite, which has attracted considerable attention in the academic community. This paper presents field static load tests on a large-diameter steel-concrete composite pile for offshore wind turbine foundations in deeply weathered granite formations. The influence of combined end-and-side grouting on the bearing behaviors of large-diameter steel-concrete composite piles in heavily weathered granite was thoroughly investigated through core drilling and CT scanning. Furthermore, numerical simulations were employed to conduct a parametric analysis of the combined post-grouting of large-diameter steel-concrete composite piles in heavily weathered granite formations, systematically studying the influence of grouting pressure and grouting volume on the bearing properties of post-grouted piles. The results indicated that compared to that before combined grouting, the bearing capacity of large-diameter steel-concrete piles is effectively enhanced after combined grouting. Core drilling clearly revealed the distribution of cement grout around and below the pile, indicating that the influence range of cement grout in heavily weathered granite formations extends from 0.5<em>D</em> below the pile tip to 5.3<em>D</em> above the pile tip. CT scanning results confirmed that cement grout could form cementation in heavily weathered granite, validating the effectiveness of combined post-grouting in such formations. The findings can serve as a reference for evaluating the grouting effect of post-grouted piles and contribute to advancing the application of post-grouted piles in heavily weathered rock formations.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"155 ","pages":"Article 104437"},"PeriodicalIF":4.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143176383","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}
Pipelines play a crucial role in the transportation of oil and gas, corrosion is a prevalent issue in submarine pipelines, and accurately predicting the corrosion rate is crucial for ensuring their safe operation. In light of the challenges posed by the scarcity and imbalance of corrosion data samples, this study develops a data-driven hybrid model for pipeline corrosion prediction. Firstly, grey relational analysis is employed to validate the nonlinear relationship between corrosion factors and corrosion rate. Subsequently, this study innovatively combines Kernel Principal Component Analysis (KPCA) with Variational Autoencoder (VAE) to capture the nonlinear relationships within the data and augment the sample size. The proposed Residual Update Gradient Forest (RUGF) model is then utilized to predict the augmented data. Finally, through SHapley Additive exPlanations (SHAP) and Fourier Amplitude Sensitivity Test (FAST), this study demonstrates that the model effectively identifies key principal components and provides explanations for the prediction results. Case studies reveal that the proposed model exhibits robust generalization capabilities and significantly outperforms classical regression algorithms, achieving highly accurate predictions of corrosion rate in Submarine pipeline.
{"title":"Submarine pipeline corrosion rate prediction model based on high-dimensional mapping augmentation and residual update gradient forest","authors":"Hongbing Liu , Zhenhao Zhu , Jingyang Zhang , Qiushuang Zheng , Ankui Xie , Xianqiang Qu","doi":"10.1016/j.apor.2025.104432","DOIUrl":"10.1016/j.apor.2025.104432","url":null,"abstract":"<div><div>Pipelines play a crucial role in the transportation of oil and gas, corrosion is a prevalent issue in submarine pipelines, and accurately predicting the corrosion rate is crucial for ensuring their safe operation. In light of the challenges posed by the scarcity and imbalance of corrosion data samples, this study develops a data-driven hybrid model for pipeline corrosion prediction. Firstly, grey relational analysis is employed to validate the nonlinear relationship between corrosion factors and corrosion rate. Subsequently, this study innovatively combines Kernel Principal Component Analysis (KPCA) with Variational Autoencoder (VAE) to capture the nonlinear relationships within the data and augment the sample size. The proposed Residual Update Gradient Forest (RUGF) model is then utilized to predict the augmented data. Finally, through SHapley Additive exPlanations (SHAP) and Fourier Amplitude Sensitivity Test (FAST), this study demonstrates that the model effectively identifies key principal components and provides explanations for the prediction results. Case studies reveal that the proposed model exhibits robust generalization capabilities and significantly outperforms classical regression algorithms, achieving highly accurate predictions of corrosion rate in Submarine pipeline.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"155 ","pages":"Article 104432"},"PeriodicalIF":4.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143176769","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 : 2025-02-01DOI: 10.1016/j.apor.2025.104436
Pei-Qing Zhao , Wen-Gang Qi , Bo Liu , Fu-Ping Gao
Significant advancements have been made in understanding local scour around pile foundations in non-cohesive soils; however, the scour phenomenon in clay soils remains relatively unexplored. Existing formulas for predicting scour development in clay soils around pile foundations often rely on empirical fittings to experimental data, rendering them limited by specific experiment conditions and prone to scale effects. To address this gap, this study proposes a physics-based model for clear-water scour development around a pile foundation in clay soils under both steady and unsteady flow conditions. By integrating a scaling expression for shear stress based on the phenomenological theory of turbulence (PTT) and incorporating a general sediment transport model, an ordinary differential equation (ODE) is derived to characterize the temporal variation in scour depth following the principle of sediment mass conservation. This ODE inherently considers all significant dimensional parameters influencing the scouring process, thereby effectively addressing potential scale-related issues. The predictions of the analytical solutions for the proposed ODE closely align with previously observed scour depth development curves around pile foundations in clay soils. Additionally, the model can be applied to scenarios with unsteady flow velocities, such as waterway floods and tidal currents.
{"title":"A physics-based model for clear-water scour development around a pile foundation in clayey soils","authors":"Pei-Qing Zhao , Wen-Gang Qi , Bo Liu , Fu-Ping Gao","doi":"10.1016/j.apor.2025.104436","DOIUrl":"10.1016/j.apor.2025.104436","url":null,"abstract":"<div><div>Significant advancements have been made in understanding local scour around pile foundations in non-cohesive soils; however, the scour phenomenon in clay soils remains relatively unexplored. Existing formulas for predicting scour development in clay soils around pile foundations often rely on empirical fittings to experimental data, rendering them limited by specific experiment conditions and prone to scale effects. To address this gap, this study proposes a physics-based model for clear-water scour development around a pile foundation in clay soils under both steady and unsteady flow conditions. By integrating a scaling expression for shear stress based on the phenomenological theory of turbulence (PTT) and incorporating a general sediment transport model, an ordinary differential equation (ODE) is derived to characterize the temporal variation in scour depth following the principle of sediment mass conservation. This ODE inherently considers all significant dimensional parameters influencing the scouring process, thereby effectively addressing potential scale-related issues. The predictions of the analytical solutions for the proposed ODE closely align with previously observed scour depth development curves around pile foundations in clay soils. Additionally, the model can be applied to scenarios with unsteady flow velocities, such as waterway floods and tidal currents.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"155 ","pages":"Article 104436"},"PeriodicalIF":4.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143176757","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 : 2025-02-01DOI: 10.1016/j.apor.2025.104440
Guoqing Zhang , Chengqian Shi , Jiqiang Li , Xianku Zhang
In this paper, a robust neural cooperative path following control algorithm is designed for multi-unmanned surface vehicles (USVs) to address the problems of the wreck avoidance by an utilization of the formation reconstruction mechanism and event-triggered rule. For this purpose, an artificial potential field (APF) guidance principle is developed, where can guide a local avoidance obstacle effect without affecting the global path following operation by designing a formation reconstruction mechanism. The major feature is that the problems of the local minimum and unattainable destination for the traditional APF are settled by presenting a velocity coordination strategy, ensuring a cooperative performance of the USVs while encountering the wreck obstacles. For the control module, a novel dynamic event-triggered rule is proposed by introducing a feedback function of output error, which can avoid the restriction of the fixed threshold parameters. Owning to this merit, the actuation frequency of the control law and adaptive neural parameter is reduced for saving a limited transmission resource usage. Further, the actuator failures caused by the potential factors, see for example saturation, delay and hysteresis are discussed by employing the two adaptive law, where the unknown gain-functions are free.
{"title":"Cooperative event-triggered control for the multi-USVs via the formation reconstruction","authors":"Guoqing Zhang , Chengqian Shi , Jiqiang Li , Xianku Zhang","doi":"10.1016/j.apor.2025.104440","DOIUrl":"10.1016/j.apor.2025.104440","url":null,"abstract":"<div><div>In this paper, a robust neural cooperative path following control algorithm is designed for multi-unmanned surface vehicles (USVs) to address the problems of the wreck avoidance by an utilization of the formation reconstruction mechanism and event-triggered rule. For this purpose, an artificial potential field (APF) guidance principle is developed, where can guide a local avoidance obstacle effect without affecting the global path following operation by designing a formation reconstruction mechanism. The major feature is that the problems of the local minimum and unattainable destination for the traditional APF are settled by presenting a velocity coordination strategy, ensuring a cooperative performance of the USVs while encountering the wreck obstacles. For the control module, a novel dynamic event-triggered rule is proposed by introducing a feedback function of output error, which can avoid the restriction of the fixed threshold parameters. Owning to this merit, the actuation frequency of the control law and adaptive neural parameter is reduced for saving a limited transmission resource usage. Further, the actuator failures caused by the potential factors, see for example saturation, delay and hysteresis are discussed by employing the two adaptive law, where the unknown gain-functions are free.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"155 ","pages":"Article 104440"},"PeriodicalIF":4.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143174566","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 : 2025-02-01DOI: 10.1016/j.apor.2025.104442
Zhaoyang Sun , Jiancheng Yu , Wentao Zhao , Feng Hu , Jin Wang , Qianlong Jin
A wingsail converts wind energy into a driving force, and the angle-of-attack polar curve of a wingsail must be obtained from a velocity prediction program (VPP) for the automatic sailing control of autonomous sailboats. Thus, a VPP is required to predict and evaluate the performance of autonomous sailboats. The wind under natural sea conditions has an atmospheric boundary layer, and its speed varies with altitude. Although wingsails are generally 1–2 m high, they are located in the bottom boundary layer of the atmosphere, where the wind speed changes rapidly. Thus, the effect of the wind velocity gradient on wingsail aerodynamic performance cannot be ignored. In this study, an autonomous sailboat VPP that considers the sea-surface wind velocity gradient was developed. The autonomous sailboat Seagull was considered as the research object. Moreover, the sailboat was modeled as a rigid body undergoing surge, roll, and yaw, and a three-degree-of-freedom mechanical equilibrium model of the autonomous sailboat was developed. The relationships between navigation resistance, heeling angle, drift angle, and velocity were calculated by computational fluid dynamics simulations using Star CCM+. The aerodynamic coefficients of the three-dimensional wingsail were calculated. The rigid wingsail was discretized along the height direction, and the aerodynamics of each unit were calculated by combining the wind velocity gradient model. Furthermore, the driving and lateral forces generated by the wingsail were obtained via integral summation. Optimization was performed to maximize the velocity of the sailboat, and the speed and wingsail angle-of-attack polar curves of the Seagull autonomous sailboat were obtained. Based on the calculation results, a comparative analysis was conducted regarding the changes in the maximum speed and optimal angle-of-attack of the autonomous sailboat, considering wind velocity gradients. Finally, the proposed VPP was verified by a comparative sea trial evaluating the sailing performance of two types of autonomous sailboat VPPs with and without considering wind velocity gradients. When the wind velocity gradient was considered, the upwind sailing ability and maximum speed of the autonomous sailboat outperformed those assuming a uniform constant-flow field.
{"title":"Autonomous sailboat velocity prediction program considering the sea-surface wind velocity gradient","authors":"Zhaoyang Sun , Jiancheng Yu , Wentao Zhao , Feng Hu , Jin Wang , Qianlong Jin","doi":"10.1016/j.apor.2025.104442","DOIUrl":"10.1016/j.apor.2025.104442","url":null,"abstract":"<div><div>A wingsail converts wind energy into a driving force, and the angle-of-attack polar curve of a wingsail must be obtained from a velocity prediction program (VPP) for the automatic sailing control of autonomous sailboats. Thus, a VPP is required to predict and evaluate the performance of autonomous sailboats. The wind under natural sea conditions has an atmospheric boundary layer, and its speed varies with altitude. Although wingsails are generally 1–2 m high, they are located in the bottom boundary layer of the atmosphere, where the wind speed changes rapidly. Thus, the effect of the wind velocity gradient on wingsail aerodynamic performance cannot be ignored. In this study, an autonomous sailboat VPP that considers the sea-surface wind velocity gradient was developed. The autonomous sailboat <em>Seagull</em> was considered as the research object. Moreover, the sailboat was modeled as a rigid body undergoing surge, roll, and yaw, and a three-degree-of-freedom mechanical equilibrium model of the autonomous sailboat was developed. The relationships between navigation resistance, heeling angle, drift angle, and velocity were calculated by computational fluid dynamics simulations using Star CCM+. The aerodynamic coefficients of the three-dimensional wingsail were calculated. The rigid wingsail was discretized along the height direction, and the aerodynamics of each unit were calculated by combining the wind velocity gradient model. Furthermore, the driving and lateral forces generated by the wingsail were obtained via integral summation. Optimization was performed to maximize the velocity of the sailboat, and the speed and wingsail angle-of-attack polar curves of the <em>Seagull</em> autonomous sailboat were obtained. Based on the calculation results, a comparative analysis was conducted regarding the changes in the maximum speed and optimal angle-of-attack of the autonomous sailboat, considering wind velocity gradients. Finally, the proposed VPP was verified by a comparative sea trial evaluating the sailing performance of two types of autonomous sailboat VPPs with and without considering wind velocity gradients. When the wind velocity gradient was considered, the upwind sailing ability and maximum speed of the autonomous sailboat outperformed those assuming a uniform constant-flow field.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"155 ","pages":"Article 104442"},"PeriodicalIF":4.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143176388","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 : 2025-02-01DOI: 10.1016/j.apor.2025.104439
Eirini Katsidoniotaki , Stephen Guth , Malin Göteman , Themistoklis P. Sapsis
Marine energy technologies face significant challenges in ensuring their survivability under extreme ocean conditions. Quantifying extreme load statistics on marine energy structures is essential for reliable structural design; however, this is a challenging task due to the scarcity of high-quality data and the inherent uncertainties associated with predicting rare events. While computational fluid dynamics (CFD) simulations can accurately capture the nonlinear dynamics and loads in extreme wave–structure interactions, providing high-fidelity data, extracting statistical information through these models is computationally impractical. This study proposes a reduced-order modeling framework for marine energy systems, enabling efficient analysis across diverse scenarios, and facilitating the quantification of extreme load statistics with significantly reduced computational cost. Specifically, a hybrid reduced-order or surrogate model for a wave energy converter is developed to map extreme sea states and design parameters to the resulting loads in the mooring system. The term ”hybrid” refers to the combination of Gaussian Process Regression (GPR) and Long Short-Term Memory (LSTM) neural networks. The model is developed using two distinct approaches: (1) a baseline approach that relies on existing CFD data for training and validation, and (2) an active learning approach that strategically selects the most informative CFD samples from regions of the input space associated with extreme mooring loads. This procedure iteratively refines the model while minimizing prediction uncertainty, making it particularly effective for real-world applications where obtaining each sample requires substantial time and resources. The developed model demonstrates its exceptional ability to efficiently predict complex load time series, including instantaneous peaks, at speeds significantly faster than traditional modeling methods. Subsequently, the model is utilized to effectively evaluate Monte Carlo samples, providing accurate estimates of the probability of extreme mooring loads. Understanding the expected extreme loads is essential during the design phase of marine energy systems, enabling cost reduction by optimizing strength margins, refining overly conservative safety factors, and enhancing overall system reliability.
{"title":"Reduced order modeling of wave energy systems via sequential Bayesian experimental design and machine learning","authors":"Eirini Katsidoniotaki , Stephen Guth , Malin Göteman , Themistoklis P. Sapsis","doi":"10.1016/j.apor.2025.104439","DOIUrl":"10.1016/j.apor.2025.104439","url":null,"abstract":"<div><div>Marine energy technologies face significant challenges in ensuring their survivability under extreme ocean conditions. Quantifying extreme load statistics on marine energy structures is essential for reliable structural design; however, this is a challenging task due to the scarcity of high-quality data and the inherent uncertainties associated with predicting rare events. While computational fluid dynamics (CFD) simulations can accurately capture the nonlinear dynamics and loads in extreme wave–structure interactions, providing high-fidelity data, extracting statistical information through these models is computationally impractical. This study proposes a reduced-order modeling framework for marine energy systems, enabling efficient analysis across diverse scenarios, and facilitating the quantification of extreme load statistics with significantly reduced computational cost. Specifically, a hybrid reduced-order or surrogate model for a wave energy converter is developed to map extreme sea states and design parameters to the resulting loads in the mooring system. The term ”hybrid” refers to the combination of Gaussian Process Regression (GPR) and Long Short-Term Memory (LSTM) neural networks. The model is developed using two distinct approaches: (1) a baseline approach that relies on existing CFD data for training and validation, and (2) an active learning approach that strategically selects the most informative CFD samples from regions of the input space associated with extreme mooring loads. This procedure iteratively refines the model while minimizing prediction uncertainty, making it particularly effective for real-world applications where obtaining each sample requires substantial time and resources. The developed model demonstrates its exceptional ability to efficiently predict complex load time series, including instantaneous peaks, at speeds significantly faster than traditional modeling methods. Subsequently, the model is utilized to effectively evaluate Monte Carlo samples, providing accurate estimates of the probability of extreme mooring loads. Understanding the expected extreme loads is essential during the design phase of marine energy systems, enabling cost reduction by optimizing strength margins, refining overly conservative safety factors, and enhancing overall system reliability.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"155 ","pages":"Article 104439"},"PeriodicalIF":4.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143328315","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 : 2025-02-01DOI: 10.1016/j.apor.2025.104435
Zhengtao Yang , Jianwen Ding , Tianzhu Hang , You Qin , Guoxing Chen
Marine coral sand is a primary fill material for port and infrastructure construction on coral islands. When embedded in slopes and embankments, it is typically in an anisotropic consolidation and saturated state. A series of undrained cyclic shear tests with various loading frequencies (f) were conducted on saturated coral sand in an anisotropic consolidation state (consolidation stress ratio, kc, and consolidation direction angle, αc). When the 90° jump of loading principal stress path with the cyclic loading direction angle (ασ) of 22.5°is applied, all strain components exhibit significant development, generalized dynamic modulus (K) replaces Young's (E) or shear modulus (G) as the suitable physical index for characterizing the global stiffness. Specimens under anisotropic consolidation persist residual generalized dynamic modulus (Kr) even in the failure phase. Kr increases with increasing kc and f, and decreases negatively exponentially as αc increases. The maximum generalized dynamic modulus (K0) is significantly influenced by anisotropic consolidation state and f. The effect (positive or negative) of the anisotropic consolidation state is determined by αc, and it is nonmonotonic from αc = 0° to 45° The increase of kc only serves to strengthen the effect of αc on K0. Additionally, K0 and f exhibit a strong logarithmic correlation, which is independent of anisotropic consolidation state. Ultimately, relative generalized dynamic modulus (η) is introduced to characterize the decline characteristic of K, and a generalized Davidenkov model which normalized consolidation conditions and f is established over a wide strain range.
{"title":"Modulus degradation characteristics of saturated marine coral sand under anisotropic consolidation and various loading frequencies","authors":"Zhengtao Yang , Jianwen Ding , Tianzhu Hang , You Qin , Guoxing Chen","doi":"10.1016/j.apor.2025.104435","DOIUrl":"10.1016/j.apor.2025.104435","url":null,"abstract":"<div><div>Marine coral sand is a primary fill material for port and infrastructure construction on coral islands. When embedded in slopes and embankments, it is typically in an anisotropic consolidation and saturated state. A series of undrained cyclic shear tests with various loading frequencies (<em>f</em>) were conducted on saturated coral sand in an anisotropic consolidation state (consolidation stress ratio, <em>k</em><sub>c</sub>, and consolidation direction angle, <em>α</em><sub>c</sub>). When the 90° jump of loading principal stress path with the cyclic loading direction angle (<em>α<sub>σ</sub></em>) of 22.5°is applied, all strain components exhibit significant development, generalized dynamic modulus (<em>K</em>) replaces Young's (<em>E</em>) or shear modulus (<em>G</em>) as the suitable physical index for characterizing the global stiffness. Specimens under anisotropic consolidation persist residual generalized dynamic modulus (<em>K</em><sub>r</sub>) even in the failure phase. <em>K</em><sub>r</sub> increases with increasing <em>k</em><sub>c</sub> and <em>f</em>, and decreases negatively exponentially as <em>α</em><sub>c</sub> increases. The maximum generalized dynamic modulus (<em>K</em><sub>0</sub>) is significantly influenced by anisotropic consolidation state and <em>f</em>. The effect (positive or negative) of the anisotropic consolidation state is determined by <em>α</em><sub>c</sub>, and it is nonmonotonic from <em>α</em><sub>c</sub> = 0° to 45° The increase of <em>k</em><sub>c</sub> only serves to strengthen the effect of <em>α</em><sub>c</sub> on <em>K</em><sub>0</sub>. Additionally, <em>K</em><sub>0</sub> and <em>f</em> exhibit a strong logarithmic correlation, which is independent of anisotropic consolidation state. Ultimately, relative generalized dynamic modulus (<em>η</em>) is introduced to characterize the decline characteristic of <em>K</em>, and a generalized Davidenkov model which normalized consolidation conditions and <em>f</em> is established over a wide strain range.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"155 ","pages":"Article 104435"},"PeriodicalIF":4.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143174567","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 : 2025-02-01DOI: 10.1016/j.apor.2025.104454
M.A. Khan , S.S.K. Singh , S. Abdullah , A. Arifin , M. Bashir
The objective of this study is to characterise the fatigue life of API X65 steel based on the effects of corrosion and internal loads fluctuations using experimental and numerical analysis. The structural integrity of offshore in-service pipes is influenced by the existence of cracks resulting from many factors, such as random loads, material characteristics, welding imperfections, and corrosive influences. The internal pressure fluctuations for in-service oil and gas pipeline were experimentally and numerically analysed to determine the fatigue life based on stress life-based models from four test conditions. Mechanical testing was conducted on ASTM E8 specimens which were submerged in sea water for 48 h with pH: 6.8 and salinity: 28. 48ppt.From the scanning electron microscopy (SEM) the localised corrosion characteristics with cavities were observed. In addition, based on the cyclic test based on ASTM 466 were carried out, the endurance limit is found to be 276.3 MPa. The random operational stresses applied to the pipeline's material were used to predict the stress- based fatigue life of in-service pipeline by considering the mean stress correction models. The fatigue life was ranging from 1.15xto 1.1xcycles to failure, among them Goodman model showed the least fatigue life. Hence, the study provides an alternative approach to estimate fatigue life of in-service offshore pipelines using loading history and experimental results as a function of corrosion fatigue mechanism.
{"title":"Fatigue life characterisation of API X65 steel pipeline for internal vibrational loads under sea water condition","authors":"M.A. Khan , S.S.K. Singh , S. Abdullah , A. Arifin , M. Bashir","doi":"10.1016/j.apor.2025.104454","DOIUrl":"10.1016/j.apor.2025.104454","url":null,"abstract":"<div><div>The objective of this study is to characterise the fatigue life of API X65 steel based on the effects of corrosion and internal loads fluctuations using experimental and numerical analysis. The structural integrity of offshore in-service pipes is influenced by the existence of cracks resulting from many factors, such as random loads, material characteristics, welding imperfections, and corrosive influences. The internal pressure fluctuations for in-service oil and gas pipeline were experimentally and numerically analysed to determine the fatigue life based on stress life-based models from four test conditions. Mechanical testing was conducted on ASTM E8 specimens which were submerged in sea water for 48 h with pH: 6.8 and salinity: 28. 48ppt.From the scanning electron microscopy (SEM) the localised corrosion characteristics with cavities were observed. In addition, based on the cyclic test based on ASTM 466 were carried out, the endurance limit is found to be 276.3 MPa. The random operational stresses applied to the pipeline's material were used to predict the stress- based fatigue life of in-service pipeline by considering the mean stress correction models. The fatigue life was ranging from 1.15x<span><math><mrow><msup><mrow><mn>10</mn></mrow><mn>9</mn></msup><mspace></mspace></mrow></math></span>to 1.1x<span><math><mrow><msup><mrow><mn>10</mn></mrow><mn>11</mn></msup><mspace></mspace></mrow></math></span>cycles to failure, among them Goodman model showed the least fatigue life. Hence, the study provides an alternative approach to estimate fatigue life of in-service offshore pipelines using loading history and experimental results as a function of corrosion fatigue mechanism.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"155 ","pages":"Article 104454"},"PeriodicalIF":4.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143174570","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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