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DWAS-RL: A safety-efficiency balanced reinforcement learning approach for path planning of Unmanned Surface Vehicles in complex marine environments
IF 4.6 2区 工程技术 Q1 ENGINEERING, CIVIL Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.119641
Tianci Qu , Gang Xiong , Hub Ali , Xisong Dong , Yunjun Han , Zhen Shen , Fei-Yue Wang
Navigating autonomous surface vehicles in dynamic marine environments, where uncertainties and disturbances like static or moving obstacles, ocean currents, and waves abound, poses a formidable challenge. Recent advancements in Deep Reinforcement Learning (DRL) have shown promising results in terms of adaptivity and timeliness through interaction with the environment. However, effectively addressing zero safety violations while achieving sample efficiency remains a dual challenge in practical applications. In this paper, we strive to ensure both safety and learning efficiency by combining the advantages of the Dynamic Window Approach (DWA) and safe reinforcement learning. First, a customized simulator for diverse marine conditions is developed, where various types of marine scenarios and algorithms are trained and testified. Then, the problem is formulated as a constrained Markov decision process and the DWA-based safe RL (DWAS-RL) approach is proposed. Specifically, to guarantee safety in the exploration process, we utilize DWA to observe and generate prudent actions by predicting potential near-future hazards, then utilize the safe RL framework for exploration and training. To improve sample efficiency, the technique called Hindsight Experience Replay is utilized to accelerate the training process. Simulation experiments demonstrate the effectiveness of our approach on the metrics of kinematics performance, safety and sample efficiency compared to the state-of-the-art DRL algorithms. These findings highlight the robustness and superiority of our approach, suggesting that our approach holds promise for addressing challenges in complex marine environments.
{"title":"DWAS-RL: A safety-efficiency balanced reinforcement learning approach for path planning of Unmanned Surface Vehicles in complex marine environments","authors":"Tianci Qu ,&nbsp;Gang Xiong ,&nbsp;Hub Ali ,&nbsp;Xisong Dong ,&nbsp;Yunjun Han ,&nbsp;Zhen Shen ,&nbsp;Fei-Yue Wang","doi":"10.1016/j.oceaneng.2024.119641","DOIUrl":"10.1016/j.oceaneng.2024.119641","url":null,"abstract":"<div><div>Navigating autonomous surface vehicles in dynamic marine environments, where uncertainties and disturbances like static or moving obstacles, ocean currents, and waves abound, poses a formidable challenge. Recent advancements in Deep Reinforcement Learning (DRL) have shown promising results in terms of adaptivity and timeliness through interaction with the environment. However, effectively addressing zero safety violations while achieving sample efficiency remains a dual challenge in practical applications. In this paper, we strive to ensure both safety and learning efficiency by combining the advantages of the Dynamic Window Approach (DWA) and safe reinforcement learning. First, a customized simulator for diverse marine conditions is developed, where various types of marine scenarios and algorithms are trained and testified. Then, the problem is formulated as a constrained Markov decision process and the DWA-based safe RL (DWAS-RL) approach is proposed. Specifically, to guarantee safety in the exploration process, we utilize DWA to observe and generate prudent actions by predicting potential near-future hazards, then utilize the safe RL framework for exploration and training. To improve sample efficiency, the technique called Hindsight Experience Replay is utilized to accelerate the training process. Simulation experiments demonstrate the effectiveness of our approach on the metrics of kinematics performance, safety and sample efficiency compared to the state-of-the-art DRL algorithms. These findings highlight the robustness and superiority of our approach, suggesting that our approach holds promise for addressing challenges in complex marine environments.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"317 ","pages":"Article 119641"},"PeriodicalIF":4.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143094299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Seismic response of reef-seawater system with steep slope under Scholte wave
IF 4.6 2区 工程技术 Q1 ENGINEERING, CIVIL Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.120063
Yunyi Li, Jian-Min Zhang, Rui Wang
The topographic feature of offshore reef leads to its unique response under earthquakes, especially considering the influence of surface waves. A dynamic solid-fluid coupling numerical model is developed to analyze the seismic response of reef-seawater system with steep slope under the Scholte wave, a special type of surface wave observed in submarine earthquakes. The governing equations, dispersion equation, and motion of steady Scholte wave are deduced. For transient Scholte wave, a non-uniform seismic wave input method for numerical analysis is proposed utilizing a novel stepwise artificial boundary condition (S-ABC). Using the proposed seismic input method, the seismic response of a typical reef-seawater system is analyzed. From the numerical results, shear wave is found to be partly dissipated by seawater. On the contrary, seawater can significantly amplify the motion of Scholte wave at the reef flat. The influence of topographic features, including flat width, height, and slope angle, are found to be limited for shear wave, but remarkable for Scholte wave. The findings suggest that amplification effect of seawater on surface waves and the influence of topographic features must be considered for the seismic response of offshore reefs.
{"title":"Seismic response of reef-seawater system with steep slope under Scholte wave","authors":"Yunyi Li,&nbsp;Jian-Min Zhang,&nbsp;Rui Wang","doi":"10.1016/j.oceaneng.2024.120063","DOIUrl":"10.1016/j.oceaneng.2024.120063","url":null,"abstract":"<div><div>The topographic feature of offshore reef leads to its unique response under earthquakes, especially considering the influence of surface waves. A dynamic solid-fluid coupling numerical model is developed to analyze the seismic response of reef-seawater system with steep slope under the Scholte wave, a special type of surface wave observed in submarine earthquakes. The governing equations, dispersion equation, and motion of steady Scholte wave are deduced. For transient Scholte wave, a non-uniform seismic wave input method for numerical analysis is proposed utilizing a novel stepwise artificial boundary condition (S-ABC). Using the proposed seismic input method, the seismic response of a typical reef-seawater system is analyzed. From the numerical results, shear wave is found to be partly dissipated by seawater. On the contrary, seawater can significantly amplify the motion of Scholte wave at the reef flat. The influence of topographic features, including flat width, height, and slope angle, are found to be limited for shear wave, but remarkable for Scholte wave. The findings suggest that amplification effect of seawater on surface waves and the influence of topographic features must be considered for the seismic response of offshore reefs.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"317 ","pages":"Article 120063"},"PeriodicalIF":4.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143094764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Experimental study of a barge-type floating offshore wind turbine under a sequential mooring line failure
IF 4.6 2区 工程技术 Q1 ENGINEERING, CIVIL Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.119999
Hung-Jie Tang , Hao-Cheng Yao , Muk Chen Ong , Ray-Yeng Yang
Navigational safety is a crucial concern for floating offshore wind turbines (FOWTs) in the Taiwan Strait due to potential conflicts between wind farms and existing navigational channels. Understanding the influence of mooring line failures, particularly sequential failures, is essential to address this issue. Despite the abundance of numerical simulations addressing this issue, experimental data on mooring line failures in FOWTs remains scarce. This study aims to provide comprehensive experimental data to support the validation of numerical models. We introduce a novel experimental procedure to examine the effects of sequential mooring line failures on mooring loads and platform motions of FOWTs under diverse wave conditions. A barge-type FOWT, equipped with an NREL 5 MW wind turbine and moored with eight catenary lines at a 1/64 scale ratio, is used for this investigation. The study analyzes the influences of wave height and wave period on the FOWT under sequential mooring failures. Both statistical and spectral analyses are conducted to examine mooring loads and platform motions. The results provide valuable insights into mooring design, platform stability, and drift distance, which are crucial for mitigating the impact of sequential mooring failures and for analyzing space utilization and navigational safety in future floating wind farms.
{"title":"Experimental study of a barge-type floating offshore wind turbine under a sequential mooring line failure","authors":"Hung-Jie Tang ,&nbsp;Hao-Cheng Yao ,&nbsp;Muk Chen Ong ,&nbsp;Ray-Yeng Yang","doi":"10.1016/j.oceaneng.2024.119999","DOIUrl":"10.1016/j.oceaneng.2024.119999","url":null,"abstract":"<div><div>Navigational safety is a crucial concern for floating offshore wind turbines (FOWTs) in the Taiwan Strait due to potential conflicts between wind farms and existing navigational channels. Understanding the influence of mooring line failures, particularly sequential failures, is essential to address this issue. Despite the abundance of numerical simulations addressing this issue, experimental data on mooring line failures in FOWTs remains scarce. This study aims to provide comprehensive experimental data to support the validation of numerical models. We introduce a novel experimental procedure to examine the effects of sequential mooring line failures on mooring loads and platform motions of FOWTs under diverse wave conditions. A barge-type FOWT, equipped with an NREL 5 MW wind turbine and moored with eight catenary lines at a 1/64 scale ratio, is used for this investigation. The study analyzes the influences of wave height and wave period on the FOWT under sequential mooring failures. Both statistical and spectral analyses are conducted to examine mooring loads and platform motions. The results provide valuable insights into mooring design, platform stability, and drift distance, which are crucial for mitigating the impact of sequential mooring failures and for analyzing space utilization and navigational safety in future floating wind farms.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"317 ","pages":"Article 119999"},"PeriodicalIF":4.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143094340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Reconstruction of scaled FOWT blades for achieving aerodynamic similarity with control strategy adjustment
IF 4.6 2区 工程技术 Q1 ENGINEERING, CIVIL Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.120078
Gang Ma , Longhui Liu , Hongwei Wang , Jianhua Zhang , Ke Sun , Hailong Chen
It is challenging to simultaneously satisfy Froude and Reynolds similarities in floating offshore wind turbine (FOWT) model tests. This issue causes the thrust and torque of FOWT model to fall short of the desired values. A scaled blade reconstruction method based on the third generation non-dominated sorting genetic algorithm (NSGA-III) and lift force matching is proposed to match the thrust and torque of the FOWT at various speed scales with those of the full model of FOWT. The chord of FOWT blade model is reconstructed based on the lift force matching principle and the chord of prototype blade model. The NSGA-III is used to optimize the control strategy (pitch angle and rotor speed under different wind speeds) to minimize the difference between the thrust and torque of the FOWT model and the desired thrust and torque. The proposed method is applied to reconstruct the blade models for the DTU 10 MW and IEA 15 MW wind turbines at different speed scale ratios, demonstrating its applicability across different turbine types, followed by a performance analysis. The results show that the thrust and torque of the FOWT models after adjusting control strategy closely match the desired values, with most of errors within 5%.
{"title":"Reconstruction of scaled FOWT blades for achieving aerodynamic similarity with control strategy adjustment","authors":"Gang Ma ,&nbsp;Longhui Liu ,&nbsp;Hongwei Wang ,&nbsp;Jianhua Zhang ,&nbsp;Ke Sun ,&nbsp;Hailong Chen","doi":"10.1016/j.oceaneng.2024.120078","DOIUrl":"10.1016/j.oceaneng.2024.120078","url":null,"abstract":"<div><div>It is challenging to simultaneously satisfy Froude and Reynolds similarities in floating offshore wind turbine (FOWT) model tests. This issue causes the thrust and torque of FOWT model to fall short of the desired values. A scaled blade reconstruction method based on the third generation non-dominated sorting genetic algorithm (NSGA-III) and lift force matching is proposed to match the thrust and torque of the FOWT at various speed scales with those of the full model of FOWT. The chord of FOWT blade model is reconstructed based on the lift force matching principle and the chord of prototype blade model. The NSGA-III is used to optimize the control strategy (pitch angle and rotor speed under different wind speeds) to minimize the difference between the thrust and torque of the FOWT model and the desired thrust and torque. The proposed method is applied to reconstruct the blade models for the DTU 10 MW and IEA 15 MW wind turbines at different speed scale ratios, demonstrating its applicability across different turbine types, followed by a performance analysis. The results show that the thrust and torque of the FOWT models after adjusting control strategy closely match the desired values, with most of errors within 5%.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"317 ","pages":"Article 120078"},"PeriodicalIF":4.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143094771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
A method for the profile optimization of the primary barrier of a membrane-type LNG tank using surrogate modeling
IF 4.6 2区 工程技术 Q1 ENGINEERING, CIVIL Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.120054
Dong-Woo Kim , Myung-Il Roh , Do-Hyun Chun , Sun-Hong Woo , Yong-Tai Kim
Membrane-type cargo holds, known for their high capacity, are commonly used in LNG carriers and are composed of various insulating materials and primary and secondary barriers to provide good thermal insulation and structural strength. The primary barrier, directly in contact with the liquefied cargo, is designed with a corrugated profile to withstand cryogenic thermal loads, cargo pressure, and sloshing loads.
In this study, a novel method for developing the optimal profile of the primary barrier in a membrane-type LNG tank is proposed. The profile is defined using a third-order Bezier curve to allow flexibility in design, and tensile tests for SUS304L, cargo pressure calculations based on IGC code, and sloshing loads derived from model tests are used for non-linear structural analysis. Global optimization of the primary barrier profile is performed using the genetic algorithm NSGA-II, applying surrogate models as objective functions. Various surrogate models, including traditional methods and DNN, are evaluated to identify the most suitable model for optimization. The proposed method was compared and analyzed with the primary barrier geometry of the MARKIII FLEX cargo containment system (CCS) of a 174K LNG carrier. The results show that the optimal primary barrier can minimize longitudinal stress, permanent deformation, and production costs.
{"title":"A method for the profile optimization of the primary barrier of a membrane-type LNG tank using surrogate modeling","authors":"Dong-Woo Kim ,&nbsp;Myung-Il Roh ,&nbsp;Do-Hyun Chun ,&nbsp;Sun-Hong Woo ,&nbsp;Yong-Tai Kim","doi":"10.1016/j.oceaneng.2024.120054","DOIUrl":"10.1016/j.oceaneng.2024.120054","url":null,"abstract":"<div><div>Membrane-type cargo holds, known for their high capacity, are commonly used in LNG carriers and are composed of various insulating materials and primary and secondary barriers to provide good thermal insulation and structural strength. The primary barrier, directly in contact with the liquefied cargo, is designed with a corrugated profile to withstand cryogenic thermal loads, cargo pressure, and sloshing loads.</div><div>In this study, a novel method for developing the optimal profile of the primary barrier in a membrane-type LNG tank is proposed. The profile is defined using a third-order Bezier curve to allow flexibility in design, and tensile tests for SUS304L, cargo pressure calculations based on IGC code, and sloshing loads derived from model tests are used for non-linear structural analysis. Global optimization of the primary barrier profile is performed using the genetic algorithm NSGA-II, applying surrogate models as objective functions. Various surrogate models, including traditional methods and DNN, are evaluated to identify the most suitable model for optimization. The proposed method was compared and analyzed with the primary barrier geometry of the MARKIII FLEX cargo containment system (CCS) of a 174K LNG carrier. The results show that the optimal primary barrier can minimize longitudinal stress, permanent deformation, and production costs.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"317 ","pages":"Article 120054"},"PeriodicalIF":4.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Preliminary investigation of the effects of a trapezoidal moonpool on the hydrodynamic performance of the Barge-Type FOWT substructures for potential OWC integration
IF 4.6 2区 工程技术 Q1 ENGINEERING, CIVIL Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2025.120532
Reza Saghi , Zhifu Li , Dezhi Ning
This paper aims to examine the effects of the geometry of the moonpool of a barge-type Floating Offshore Wind Turbine (FOWT) substructure on the operation of an Oscillating Water Column (OWC) wave energy capture system installed inside the moonpool. The analysis takes into consideration the piston-like water oscillation relative to the heave motion as the main criteria for evaluating the operation of the OWC system. To achieve this, a numerical model was developed in OpenFOAM to simulate a barge-type FOWT substructure, utilizing coupled overset-volume of fluid methods. The barge-type FOWT substructure with a trapezoidal moonpool featuring different sizes and inner-sidewall angles was modeled against waves with varying wave frequencies. Based on the obtained results, trapezoidal square moonpools with sidewall angles of 80 and 100° are identified as favorable options relative to those with vertical walls, enhancing the operation of the OWC system across different ranges of wave frequencies.
{"title":"Preliminary investigation of the effects of a trapezoidal moonpool on the hydrodynamic performance of the Barge-Type FOWT substructures for potential OWC integration","authors":"Reza Saghi ,&nbsp;Zhifu Li ,&nbsp;Dezhi Ning","doi":"10.1016/j.oceaneng.2025.120532","DOIUrl":"10.1016/j.oceaneng.2025.120532","url":null,"abstract":"<div><div>This paper aims to examine the effects of the geometry of the moonpool of a barge-type Floating Offshore Wind Turbine (FOWT) substructure on the operation of an Oscillating Water Column (OWC) wave energy capture system installed inside the moonpool. The analysis takes into consideration the piston-like water oscillation relative to the heave motion as the main criteria for evaluating the operation of the OWC system. To achieve this, a numerical model was developed in OpenFOAM to simulate a barge-type FOWT substructure, utilizing coupled overset-volume of fluid methods. The barge-type FOWT substructure with a trapezoidal moonpool featuring different sizes and inner-sidewall angles was modeled against waves with varying wave frequencies. Based on the obtained results, trapezoidal square moonpools with sidewall angles of 80 and 100° are identified as favorable options relative to those with vertical walls, enhancing the operation of the OWC system across different ranges of wave frequencies.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"322 ","pages":"Article 120532"},"PeriodicalIF":4.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143168074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Underwater vehicle autopilot system for controlling depth and pitch: Maneuvering through near-surface waves and environmental disturbances
IF 4.6 2区 工程技术 Q1 ENGINEERING, CIVIL Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.119910
Vladimir Petrov, Gage MacLin, Venanzio Cichella
This paper introduces a control algorithm for autonomous underwater vehicles (AUVs) designed to perform missions under complex near-surface wave conditions. The algorithm enables the AUV to control depth and pitch in response to changing environmental conditions and speed of the AUV. The proposed control system targets the specific case of a Joubert BB2 vehicle, utilizing control inputs from the tail planes, sail plane, and hover tank. The control system combines a Linear Quadratic Regulator (LQR) with L1 adaptive autopilot augmentation. The LQR controller, designed to address wave disturbances, incorporates a filtering technique that mitigates the effects of such disturbances on the vehicle’s actuators without affecting the robustness of the autopilot. The L1 adaptive augmentation deals with low-frequency disturbance and model uncertainties, and ensures asymptotic stability of depth and pitch dynamics in the presence of such disturbance. This advanced control strategy for underwater vehicles significantly enhances their functionality across various marine operations. The effectiveness of the proposed control system has been validated through comprehensive simulations using a reduced order model of the Joubert BB2 vehicle, which was developed in our previous work. This validation confirms the potential of the control system to improve AUV performance in demanding underwater conditions.
{"title":"Underwater vehicle autopilot system for controlling depth and pitch: Maneuvering through near-surface waves and environmental disturbances","authors":"Vladimir Petrov,&nbsp;Gage MacLin,&nbsp;Venanzio Cichella","doi":"10.1016/j.oceaneng.2024.119910","DOIUrl":"10.1016/j.oceaneng.2024.119910","url":null,"abstract":"<div><div>This paper introduces a control algorithm for autonomous underwater vehicles (AUVs) designed to perform missions under complex near-surface wave conditions. The algorithm enables the AUV to control depth and pitch in response to changing environmental conditions and speed of the AUV. The proposed control system targets the specific case of a Joubert BB2 vehicle, utilizing control inputs from the tail planes, sail plane, and hover tank. The control system combines a Linear Quadratic Regulator (LQR) with <span><math><msub><mrow><mi>L</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> adaptive autopilot augmentation. The LQR controller, designed to address wave disturbances, incorporates a filtering technique that mitigates the effects of such disturbances on the vehicle’s actuators without affecting the robustness of the autopilot. The <span><math><msub><mrow><mi>L</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> adaptive augmentation deals with low-frequency disturbance and model uncertainties, and ensures asymptotic stability of depth and pitch dynamics in the presence of such disturbance. This advanced control strategy for underwater vehicles significantly enhances their functionality across various marine operations. The effectiveness of the proposed control system has been validated through comprehensive simulations using a reduced order model of the Joubert BB2 vehicle, which was developed in our previous work. This validation confirms the potential of the control system to improve AUV performance in demanding underwater conditions.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"317 ","pages":"Article 119910"},"PeriodicalIF":4.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Hybrid analysis of severe wave impact and hydroelastic effects on a rectangular vertical cylinder
IF 4.6 2区 工程技术 Q1 ENGINEERING, CIVIL Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.119846
Alireza Ahani , Marilena Greco , Bjørn Christian Abrahamsen
This study investigates the most severe wave impact scenario documented by Abrahamsen et al. (2023a) on a rectangular vertical cylinder, mimicking a semisubmersible platform leg. Both flexible and rigid panels were tested under severe irregular waves, employing a hybrid analysis that combined signal-analysis techniques with use of a finite element method (FEM) and a simplified hydrodynamic model. Results revealed nearly two-dimensional impacts with gas-cavity entrapment causing peak pressure loads and subsequent oscillations. Maximum strain in the flexible panel occurred as a consequence of the cavity compression but the evolution of strain frequency content suggested a shorter permanence of the cavity at the structure and aero/hydroelastic effects. The forced-vibration stage connected maximum strain with peak pressures, highlighting the role of cavity compression for the excitation loads and for the hydrodynamic damping induced on the structure; this damping dominated over structural damping. A modal decomposition approach identified the deflection and strain modes, enabling the reconstruction of the distributed deflections, strains, and stresses, with the use of only five strain gauges.
{"title":"Hybrid analysis of severe wave impact and hydroelastic effects on a rectangular vertical cylinder","authors":"Alireza Ahani ,&nbsp;Marilena Greco ,&nbsp;Bjørn Christian Abrahamsen","doi":"10.1016/j.oceaneng.2024.119846","DOIUrl":"10.1016/j.oceaneng.2024.119846","url":null,"abstract":"<div><div>This study investigates the most severe wave impact scenario documented by Abrahamsen et al. (2023a) on a rectangular vertical cylinder, mimicking a semisubmersible platform leg. Both flexible and rigid panels were tested under severe irregular waves, employing a hybrid analysis that combined signal-analysis techniques with use of a finite element method (FEM) and a simplified hydrodynamic model. Results revealed nearly two-dimensional impacts with gas-cavity entrapment causing peak pressure loads and subsequent oscillations. Maximum strain in the flexible panel occurred as a consequence of the cavity compression but the evolution of strain frequency content suggested a shorter permanence of the cavity at the structure and aero/hydroelastic effects. The forced-vibration stage connected maximum strain with peak pressures, highlighting the role of cavity compression for the excitation loads and for the hydrodynamic damping induced on the structure; this damping dominated over structural damping. A modal decomposition approach identified the deflection and strain modes, enabling the reconstruction of the distributed deflections, strains, and stresses, with the use of only five strain gauges.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"317 ","pages":"Article 119846"},"PeriodicalIF":4.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143094350","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Constrained trajectory planning for automatic berthing of maritime autonomous surface ships based on input-to-state safe zeroing high order control barrier functions
IF 4.6 2区 工程技术 Q1 ENGINEERING, CIVIL Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.119843
Haodong Liu , Nan Gu , Anqing Wang , Yuchao Wang , Tieshan Li , Zhouhua Peng
This paper addresses the trajectory planning of maritime autonomous surface ships (MASSs) for automatic berthing moving in a restrictive harbor subject to multiple port shorelines. A trajectory planning method is proposed for the automatic berthing of an MASS with collision-free behavior. First, a line-of-sight guidance method is utilized to obtain a sequence of surge velocity, sway velocity, and yaw rate signals such that a nominal trajectory is generated for the MASS to reach the final berthing position with a desired heading angle. Next, a sequence of surge force and sway force signals are generated by using the estimated disturbance information obtained from extend state observer. Then, input-to-state safe zeroing high order control barrier functions (ISSf-ZHOCBFs) are introduced to encode the port shorelines as multiple safety constraints. Finally, the encoded safety constraints are further resorted to formulate a quadratic program problem for obtaining optimized yaw rate, surge force, and sway force signals such that a safety trajectory for automatic berthing is obtained. Simulation results verify that the effectiveness of the proposed ISSf-ZHOCBF-based trajectory planning method for collision-free automatic berthing.
{"title":"Constrained trajectory planning for automatic berthing of maritime autonomous surface ships based on input-to-state safe zeroing high order control barrier functions","authors":"Haodong Liu ,&nbsp;Nan Gu ,&nbsp;Anqing Wang ,&nbsp;Yuchao Wang ,&nbsp;Tieshan Li ,&nbsp;Zhouhua Peng","doi":"10.1016/j.oceaneng.2024.119843","DOIUrl":"10.1016/j.oceaneng.2024.119843","url":null,"abstract":"<div><div>This paper addresses the trajectory planning of maritime autonomous surface ships (MASSs) for automatic berthing moving in a restrictive harbor subject to multiple port shorelines. A trajectory planning method is proposed for the automatic berthing of an MASS with collision-free behavior. First, a line-of-sight guidance method is utilized to obtain a sequence of surge velocity, sway velocity, and yaw rate signals such that a nominal trajectory is generated for the MASS to reach the final berthing position with a desired heading angle. Next, a sequence of surge force and sway force signals are generated by using the estimated disturbance information obtained from extend state observer. Then, input-to-state safe zeroing high order control barrier functions (ISSf-ZHOCBFs) are introduced to encode the port shorelines as multiple safety constraints. Finally, the encoded safety constraints are further resorted to formulate a quadratic program problem for obtaining optimized yaw rate, surge force, and sway force signals such that a safety trajectory for automatic berthing is obtained. Simulation results verify that the effectiveness of the proposed ISSf-ZHOCBF-based trajectory planning method for collision-free automatic berthing.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"317 ","pages":"Article 119843"},"PeriodicalIF":4.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143094298","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Mitigating cavitation effects on Francis turbine performance: A two-phase flow analysis
IF 4.6 2区 工程技术 Q1 ENGINEERING, CIVIL Pub Date : 2025-02-01 DOI: 10.1016/j.oceaneng.2024.120018
Burak Altintas , Ece Ayli , Kutay Celebioglu , Selin Aradag , Yigit Tascioglu
Due to their ability to operate over a wide range of flow rates and generate high power, Francis turbines are the most widely used of hydroturbine type. Hydraulic turbines, are designed for specific flow and head conditions tailored to site conditions. However, Francis turbines can also be operated outside of design conditions due to varying flow and head values. Operation outside of design conditions can lead to cavitation. In this study, single-phase steady-state an alyses were conducted initially to examine cavitation in detail, followed by two-phase transient analyses. The results obtained from these analyses were compared to determine the cavitation characteristics of the designed turbine. The steady-state simulation results indicate the occurrence of cavitation, including traveling bubble and draft tube cavitation, under overload operating conditions. However, these cavitation characteristics are not observed in the two-phase transient simulation results under the same operating conditions. Additionally, the turbine efficiency is predicted to be higher in the transient simulation results. This is attributed to the frozen rotor interface used in the steady-state simulations, which over predicts flow irregularities. The reduced flow irregularities in the transient results have resulted in lower cavitation and losses, leading to higher predicted turbine efficiency.
{"title":"Mitigating cavitation effects on Francis turbine performance: A two-phase flow analysis","authors":"Burak Altintas ,&nbsp;Ece Ayli ,&nbsp;Kutay Celebioglu ,&nbsp;Selin Aradag ,&nbsp;Yigit Tascioglu","doi":"10.1016/j.oceaneng.2024.120018","DOIUrl":"10.1016/j.oceaneng.2024.120018","url":null,"abstract":"<div><div>Due to their ability to operate over a wide range of flow rates and generate high power, Francis turbines are the most widely used of hydroturbine type. Hydraulic turbines, are designed for specific flow and head conditions tailored to site conditions. However, Francis turbines can also be operated outside of design conditions due to varying flow and head values. Operation outside of design conditions can lead to cavitation. In this study, single-phase steady-state an alyses were conducted initially to examine cavitation in detail, followed by two-phase transient analyses. The results obtained from these analyses were compared to determine the cavitation characteristics of the designed turbine. The steady-state simulation results indicate the occurrence of cavitation, including traveling bubble and draft tube cavitation, under overload operating conditions. However, these cavitation characteristics are not observed in the two-phase transient simulation results under the same operating conditions. Additionally, the turbine efficiency is predicted to be higher in the transient simulation results. This is attributed to the frozen rotor interface used in the steady-state simulations, which over predicts flow irregularities. The reduced flow irregularities in the transient results have resulted in lower cavitation and losses, leading to higher predicted turbine efficiency.</div></div>","PeriodicalId":19403,"journal":{"name":"Ocean Engineering","volume":"317 ","pages":"Article 120018"},"PeriodicalIF":4.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143094767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
期刊
Ocean Engineering
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