Ocean EngineeringPub Date : 2025-07-26DOI: 10.1016/j.oceaneng.2025.122211
Vatsal Dhamelia, Ming Zhao, Pan Hu, Heath Palmer, Adnan Munir
{"title":"Experiment investigation of scour and self-burial of sagging subsea pipelines in steady current","authors":"Vatsal Dhamelia, Ming Zhao, Pan Hu, Heath Palmer, Adnan Munir","doi":"10.1016/j.oceaneng.2025.122211","DOIUrl":"10.1016/j.oceaneng.2025.122211","url":null,"abstract":"<div><div>Fundamental mechanisms of the self-burial process of a subsea pipeline that fully sags into a scour hole and the effects of the timing of pipeline sagging on the self-burial are investigated experimentally. Each self-burial experiment starts with an initial scour hole that is generated by a scour experiment for a particular time, which is defined as the touchdown time <em>T</em><sub>td</sub>. The effects of the touchdown time on the self-burial process are discussed. It was found that, to achieve self-burial, the touchdown time must be delayed to allow a sufficiently deep scour hole to develop. If the touchdown time is too soon, the scour will continue after the pipeline touches down and self-burial will not happen. After touchdown, self-burial initialises at the downstream side of the pipeline and has two stages: pre-self-burial scour and self-burial. The scoured sand behind the pipeline during pre-self-burial scour form a sand dune behind the pipeline and this sand dune is the key mechanisms of self-burial. The growth of this sand dune slows down the flow through the gap and finally stops the scour. Flow visualisation of a sagging pipeline was also conducted using the Particle Image Velocimetry method to understand the flow mechanism at different stages of the self-burial process. If the scour is allowed to fully develop, the pipeline can sag into the scour hole to a vertical distance of 0.7<em>D</em> before self-burial occurs, where <em>D</em> is diameter of pipeline. Based on the visualisation, recirculation of flow downstream to the pipeline plays a significant role in backfilling in the self-burial process.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"340 ","pages":"Article 122211"},"PeriodicalIF":4.6,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144711359","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}
Ocean EngineeringPub Date : 2025-07-26DOI: 10.1016/j.oceaneng.2025.122233
Ting Wu , Yan Zhang , Xiaofei Yang , Hui Ye , Zhengrong Xiang
{"title":"Energy-efficient tracking control of unmanned surface vehicles: A fixed-time pose and velocity constrained strategy","authors":"Ting Wu , Yan Zhang , Xiaofei Yang , Hui Ye , Zhengrong Xiang","doi":"10.1016/j.oceaneng.2025.122233","DOIUrl":"10.1016/j.oceaneng.2025.122233","url":null,"abstract":"<div><div>This paper investigates the fixed-time energy-efficient tracking control for unmanned surface vehicles (USVs) with external disturbances and unknown dynamics. To guarantee the safety of USVs in constrained environments, the pose and velocity constraints are considered. Firstly, a tan-type nonlinear mapping function that incorporates the constraint set is constructed, and the original USV system with pose and velocity constraints is converted into an unconstrained one. Subsequently, a fixed-time disturbance observer is designed to estimate external disturbances. Furthermore, by employing the backstepping technique and fixed-time theory, the performance index functions that measure tracking error costs and control input costs are presented, and then the virtual and actual control signals can be derived as the optimized solutions of the corresponding subsystems. Given the inherent difficulties in solving the Hamilton-Jacobi-Bellman (HJB) equations, the reinforcement learning (RL) algorithm within an identifier-actor-critic framework is proposed, where identifiers are utilized to approximate unknown dynamics. The control scheme ensures that the tracking error converges to a small region around zero within a fixed time while minimizing the costs and meeting the constraint requirements. Finally, the simulation results verify the effectiveness of the proposed method.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"340 ","pages":"Article 122233"},"PeriodicalIF":4.6,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144711362","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}
Ocean EngineeringPub Date : 2025-07-26DOI: 10.1016/j.oceaneng.2025.122264
Nan Zhang , Yifan Duan , Xinhong Li , Qinghua Gu , Mingyang Yang , Xiuquan Liu , Yuanjiang Chang
{"title":"Dynamic characteristics of the nonlinear tensioner-riser system under soft hang-off mode using a coupled numerical simulation method","authors":"Nan Zhang , Yifan Duan , Xinhong Li , Qinghua Gu , Mingyang Yang , Xiuquan Liu , Yuanjiang Chang","doi":"10.1016/j.oceaneng.2025.122264","DOIUrl":"10.1016/j.oceaneng.2025.122264","url":null,"abstract":"<div><div>Deepwater drilling risers in soft hang-off configurations are subjected to complex dynamic loads from platform heave and lateral wave-current excitations. Traditional models often simplify tensioners as linear springs, neglecting key nonlinear mechanisms that critically influence axial and lateral responses. This study develops a fully coupled nonlinear time-domain simulation method that integrates a high-fidelity tensioner model with a geometrically nonlinear riser system. The tensioner model incorporates gas compressibility, internal friction, and hydraulic pressure losses, enabling bidirectional interaction between platform motion and riser dynamics. Results demonstrate that the nonlinear tensioner introduces dynamic top tension variation, which significantly amplifies axial vibration amplitudes. In contrast, its influence on lateral displacement is relatively minor, as geometric nonlinearity of the riser dominates the lateral response. Comparative analysis reveals that linear tensioner models significantly misrepresent riser dynamic responses by underestimating top tension and overestimating bending stresses, thereby leading to inaccurate predictions of structural behavior and potential fatigue damage. Sensitivity analyses show that recoil valve opening and initial gas volume dominate riser stability, while fluid viscosity has minor influence. These findings highlight the importance of refined tensioner modeling in accurately predicting riser dynamics and enhancing the structural integrity of soft hang-off systems under extreme marine environments.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"340 ","pages":"Article 122264"},"PeriodicalIF":4.6,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144711364","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}
Ocean EngineeringPub Date : 2025-07-26DOI: 10.1016/j.oceaneng.2025.122289
Glib Ivanov , Yongyan Wu , Kai-Tung Ma
{"title":"Optimized mooring solutions for floating offshore wind turbines in harsh environments","authors":"Glib Ivanov , Yongyan Wu , Kai-Tung Ma","doi":"10.1016/j.oceaneng.2025.122289","DOIUrl":"10.1016/j.oceaneng.2025.122289","url":null,"abstract":"<div><div>The mooring system is a critical component of floating offshore wind turbines (FOWTs). Increased wind turbines in harsher environments necessitate larger mooring sizes and additional lines for redundancy. This study investigates the optimal mooring system for a three-column semi-submersible FOWT in Taiwan Strait, a region characterized by typhoon conditions. A novel mooring concept, V-Share Mooring, is introduced and compared against traditional clustered and spread mooring systems. The V-Share design connects two mooring lines from two columns of the semi-submersible to a single anchor. It utilizes all field-proven mooring components for reduced engineering risk and readiness. It is found that the V-Share mooring can stabilize the floater with smaller platform offset and yaw motions and may provide an opportunity to reduce the floater size. Using polynomial regression with response surface analysis of platform offset and mooring tension, optimal mooring design parameters, including pretension and total chain weight, are determined. A cost comparison provides an apples-to-apples assessment of total mooring procurement and installation expenses. Due to the anchor sharing, the V-Share system can be relatively cost-efficient, offering a reduced mooring footprint, minimized seabed disruption, and improved floater stability. The findings in the study may contribute to improving the economic viability of FOWTs.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"340 ","pages":"Article 122289"},"PeriodicalIF":4.6,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144711360","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}
Ocean EngineeringPub Date : 2025-07-26DOI: 10.1016/j.oceaneng.2025.122287
Zhenya Li , Chiheng Zhao , Zhongjin Wang , Cun Zhang , Zhiqing Zhang
{"title":"Torsional vibration of a pipe pile in layered unsaturated soil considering the construction disturbance","authors":"Zhenya Li , Chiheng Zhao , Zhongjin Wang , Cun Zhang , Zhiqing Zhang","doi":"10.1016/j.oceaneng.2025.122287","DOIUrl":"10.1016/j.oceaneng.2025.122287","url":null,"abstract":"<div><div>In this study, an analytical solution is developed to address the torsional vibration of a pipe pile embedded in layered unsaturated soil. The continuum model is employed to simulate the behavior of both the outer and inner soils. Additionally, the shear complex stiffness transfer (SCST) model is utilized to account for the effect of construction-induced disturbance. By solving the governing equations for the outer and inner soils, the circumferential shear stresses acting on the pipe pile by these two regions are ascertained. Subsequently, the governing equation for the pipe pile is solved, thereby obtaining its complex impedance and the amplitude-frequency response of the twist angle through the impedance transfer approach. Eventually, upon validating the proposed solution, a parametric study is carried out to explore the effects of saturation degree, construction disturbance, inner soil height, and pipe pile defects on pile torsional vibration.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"340 ","pages":"Article 122287"},"PeriodicalIF":4.6,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144711361","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}
{"title":"Design sea state assessment via IFORM-based environmental contour approach derived with Gaussian mixture model","authors":"Yuliang Zhao , Sheng Dong , Bingchen Liang , Zhi-Ming Yuan , Atilla Incecik","doi":"10.1016/j.oceaneng.2025.122259","DOIUrl":"10.1016/j.oceaneng.2025.122259","url":null,"abstract":"<div><div>Environmental contour (EC) plays a crucial role in the design of marine structures. It has been widely used to pinpoint extreme sea states and estimate potential structural damages. ECs can be obtained through the Inverse First Order Reliability Method (IFORM) in combination with joint probability techniques for metocean variables. This paper aims to capture the intricate dependence structure within metocean data by employing a suitable and versatile statistical model. The Gaussian mixture distribution was adopted to model both the marginal and bivariate distributions of environmental variables. The optimal components number was ascertained using the Bayesian Information Criterion, and the expectation-maximization algorithm was harnessed to estimate the numerous unknown parameters in the mixture models. The validity of the joint mixture model was then evaluated through statistical tests. Subsequently, the ECs derived using the Gaussian mixture model were compared with those constructed by the commonly used conditional Weibull-Lognormal model. The robustness of the mixture model was verified by its satisfied performance in fitting wave data from diverse sites and handling contours with highly complex probabilistic characteristics. Those refined ECs showed great potential for evaluating the most probable extreme responses of marine structures, thereby enhancing the safety and reliability of marine engineering designs.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"340 ","pages":"Article 122259"},"PeriodicalIF":4.6,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144711358","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}
Ocean EngineeringPub Date : 2025-07-26DOI: 10.1016/j.oceaneng.2025.122269
Yuxiang Ma , Yuqi Ding , Congfang Ai , Yue Liu , Shuxia Bu
{"title":"Prediction of wave parameters under extreme sea conditions using a 3D U-Net deep learning model","authors":"Yuxiang Ma , Yuqi Ding , Congfang Ai , Yue Liu , Shuxia Bu","doi":"10.1016/j.oceaneng.2025.122269","DOIUrl":"10.1016/j.oceaneng.2025.122269","url":null,"abstract":"<div><div>Wave parameters forecast plays a crucial role in coastal and ocean engineering, but there are fewer studies on forecasting under extreme sea conditions. In order to solve this problem, this paper proposes a 3D U-Net wave forecast model for significant wave height (SWH) and mean zero-crossing period (MP2) forecast in the Northwest Pacific (NWP). Meanwhile, this paper proposed a multi-dimensional dataset construction method to train the model for wave forecast under extreme sea conditions. The forecast results are evaluated for 25 tropical cyclone periods in 2020, and the results show that the 3D U-Net model consistently demonstrated superior accuracy. The mean absolute error (MAE) and mean absolute percentage error (MAPE) were 0.14 m, 9.6 % for SWH forecast, and 0.34 s, 6.6 % for MP2 forecast, respectively, and the <span><math><mrow><msup><mi>R</mi><mn>2</mn></msup></mrow></math></span> was as high as 0.98 for both SWH and MP2. In addition, four buoy data are used for comparison, and the 3D U-Net model is even stronger than the ERA5 reanalysis for forecasting at the maximum SWH. These results highlight the strong regional forecasting ability of the 3D U-Net model in both normal and extreme sea conditions.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"340 ","pages":"Article 122269"},"PeriodicalIF":4.6,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144711363","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}
Ocean EngineeringPub Date : 2025-07-25DOI: 10.1016/j.oceaneng.2025.122250
Youkou Dong , Zihang Liu , Dingtao Yan , Honglei Sun , Dong Wang
{"title":"Assessment of horizontal impact forces of submarine landslides upon fixed subsea pile foundations","authors":"Youkou Dong , Zihang Liu , Dingtao Yan , Honglei Sun , Dong Wang","doi":"10.1016/j.oceaneng.2025.122250","DOIUrl":"10.1016/j.oceaneng.2025.122250","url":null,"abstract":"<div><div>Accurate quantification of impact loads from submarine landslides is critical for ensuring the structural integrity and long-term safety of offshore pile foundations in geohazard-prone areas. This study investigates the steady-state horizontal forces imposed by submarine landslides on fixed subsea piles through numerical simulations. A finite volume model, validated against experimental data of flume tests, is employed to capture the yield stress and shear-thinning behavior of the sliding material using the Herschel-Bulkley rheological framework. To account for various combinations of the geometrical configurations of the pile and the rheological properties of the sliding material, a hybrid formulation, based on both geotechnical and fluid mechanics, is adopted to interpret the resulting impact forces. These impact forces are decomposed into components associated with inertia effects, shear resistance, and asymmetric geo-static pressure along with the drag coefficient, bearing capacity factor and static pressure coefficient, respectively. Regression analysis of the results from parametric studies indicates that short piles exhibit higher drag coefficients and bearing capacity factors compared to long piles while long piles present larger static pressure coefficients. A case study further demonstrates that inertial effects dominate at high velocity, while shear resistance governs at low velocities, with the static pressure component remaining small across all conditions.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"340 ","pages":"Article 122250"},"PeriodicalIF":4.6,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144704035","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}
Ocean EngineeringPub Date : 2025-07-25DOI: 10.1016/j.oceaneng.2025.122275
Xin Zhang , Zengcheng Zhou , Yihao Shi , Ming Li , Wei Peng , Chen Song , Zhi Li , Xingong Cheng , Menghua Zhang
{"title":"Adaptive sliding mode control for underactuated ship-mounted cranes with dead zones and actuated/unactuated state constraints","authors":"Xin Zhang , Zengcheng Zhou , Yihao Shi , Ming Li , Wei Peng , Chen Song , Zhi Li , Xingong Cheng , Menghua Zhang","doi":"10.1016/j.oceaneng.2025.122275","DOIUrl":"10.1016/j.oceaneng.2025.122275","url":null,"abstract":"<div><div>With the rapid development of maritime engineering in recent years, ship-mounted cranes have become increasingly critical for underwater load-handing operations. Under the severe maritime environment, anti-swaying control of submerged payloads faces significant challenges due to the inherently complicated dynamics of ship-mounted cranes, which exhibit strong nonlinearities, high coupling properties, and hydrodynamic forces acting directly on underwater payloads. An adaptive fuzzy controller is proposed in this study to limit the boom and payload swing angles to a specified range while addressing dead zones and generating integral-type functions with actuated/unactuated constraints. The construction of integral constraint terms as time-variant gains, which introduce control energy in advance to drive state variables to converge to their desired values, ensures both actuated and unactuated constraints. Through rigorous theoretical analysis, the payload swing angle can converge to zero while enabling the finite-time convergence of both the boom and rope. Experimental validation confirms the method's robustness and efficacy. To the best of our knowledge, this work presents the first adaptive fuzzy control solution for ship-mounted cranes to simultaneously handle the underwater payload lifting problem under actuated/unactuated state constraints and dead zones.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"340 ","pages":"Article 122275"},"PeriodicalIF":4.6,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144704033","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}
Ocean EngineeringPub Date : 2025-07-25DOI: 10.1016/j.oceaneng.2025.122248
Hui Yi , Zhipeng Du , Hui Chen , Ke Zhang
{"title":"Multi-objective optimization framework for PEMFC hybrid marine power Systems: Integrating dynamic lifetime degradation and energy management","authors":"Hui Yi , Zhipeng Du , Hui Chen , Ke Zhang","doi":"10.1016/j.oceaneng.2025.122248","DOIUrl":"10.1016/j.oceaneng.2025.122248","url":null,"abstract":"<div><div>This study develops a comprehensive multi-objective optimization framework for fuel cell hybrid marine power systems, aiming to effectively balance initial capital investment and long-term operational costs under dynamic, load-induced component degradation. The proposed framework integrates dynamic lifespan models of fuel cells and lithium batteries into a bi-objective optimization model, which is addressed through the application of an improved adaptive multi-objective particle swarm optimization algorithm (IAMOPSO). This approach facilitates the derivation of Pareto frontier solutions that explicitly delineate the trade-offs between capital expenditures — encompassing fuel cell rated power and battery series/parallel configurations — and lifecycle costs, including hydrogen consumption and equipment health degradation. Notably, the compromise solution demonstrates an 11.0 % reduction in operating costs relative to the minimum-investment design, with a marginal 11.2 % increase in initial investment, underscoring the practical engineering trade-offs involved. Furthermore, sensitivity analysis employing Sobol indices quantitatively assesses the influence of key parameters on overall system economics, thereby providing critical insights for decision-making in hybrid marine power system design. The proposed framework demonstrates robust performance across varying design scenarios, thereby reinforcing its applicability and effectiveness in optimizing hybrid marine power systems.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"340 ","pages":"Article 122248"},"PeriodicalIF":4.6,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144711357","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}