Pub Date : 2024-10-25DOI: 10.1016/j.apor.2024.104283
Milad Shajaripour, Hamid Zeraatgar
This study addresses the hydrodynamic performance of high-speed planing catamarans compared to equivalent mono-hulls using numerical simulations and experimental validation. The study includes computational fluid dynamics (CFD) simulations to analyse the hydrodynamic behaviour of the catamarans under various operating conditions, such as different speeds, deadrise angles, and static trim angles. Comparison of the numerical simulation results with model tests reveals that the numerical results for the resistance of planing catamarans at high speeds deviate significantly from the experimental data due to strong spray. This discrepancy is systematic (rather than random) and has been recognised and modified. The modified numerical results are sufficiently accurate for further pursuit. Generally, the resistance of a planing catamaran compared to an equivalent planing mono-hull is significantly larger, approximately 25–60 %, while the absolute sinkage is lower. A positive feature of the catamaran is its ability to prevent porpoising instability, especially in boats with a small deadrise angle. Choosing a planing catamaran over a mono-hull must offer other substantial advantages, such as better seakeeping performance, which compensate the higher resistance.
{"title":"Hydrodynamic performance comparison of planing catamarans with mono-hulls using numerical and experimental methods","authors":"Milad Shajaripour, Hamid Zeraatgar","doi":"10.1016/j.apor.2024.104283","DOIUrl":"10.1016/j.apor.2024.104283","url":null,"abstract":"<div><div>This study addresses the hydrodynamic performance of high-speed planing catamarans compared to equivalent mono-hulls using numerical simulations and experimental validation. The study includes computational fluid dynamics (CFD) simulations to analyse the hydrodynamic behaviour of the catamarans under various operating conditions, such as different speeds, deadrise angles, and static trim angles. Comparison of the numerical simulation results with model tests reveals that the numerical results for the resistance of planing catamarans at high speeds deviate significantly from the experimental data due to strong spray. This discrepancy is systematic (rather than random) and has been recognised and modified. The modified numerical results are sufficiently accurate for further pursuit. Generally, the resistance of a planing catamaran compared to an equivalent planing mono-hull is significantly larger, approximately 25–60 %, while the absolute sinkage is lower. A positive feature of the catamaran is its ability to prevent porpoising instability, especially in boats with a small deadrise angle. Choosing a planing catamaran over a mono-hull must offer other substantial advantages, such as better seakeeping performance, which compensate the higher resistance.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"153 ","pages":"Article 104283"},"PeriodicalIF":4.3,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527398","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-25DOI: 10.1016/j.apor.2024.104273
C. Peláez-Rodríguez , J. Pérez-Aracil , A.M. Gómez-Orellana , D. Guijo-Rubio , V.M. Vargas , P.A. Gutiérrez , C. Hervás-Martínez , S. Salcedo-Sanz
Providing an accurate prediction of Significant Wave Height (SWH), and specially of extreme SWH events, is crucial for coastal engineering activities and holds major implications in several sectors as offshore renewable energy. With the aim of overcoming the challenge of skewness and imbalance associated with the prediction of these extreme SWH events, a fuzzy-based cascade ensemble of regression models is proposed. This methodology allows to remarkably improve the predictive performance on the extreme SWH values, by using different models specialised in different ranges on the target domain. The method’s explainability is enhanced by analysing the contribution of each model, aiding in identifying those predictor variables more characteristic for the detection of extreme SWH events. The methodology has been validated tackling a long-term SWH prediction problem, considering two case studies over the southwest coast of the United States of America. Both reanalysis data, providing information on various meteorological factors, and SWH measurements, obtained from the nearby stations and the station under examination, have been considered. The goodness of the proposed approach has been validated by comparing its performance against several machine learning and deep learning regression techniques, leading to the conclusion that fuzzy ensemble models perform much better in the prediction of extreme events, at the cost of a slight deterioration in the rest of the samples. The study contributes to advancing the SWH prediction field, specially, to understanding the behaviour behind extreme SWH events, critical for various sectors reliant on oceanic conditions.
{"title":"Fuzzy-based ensemble methodology for accurate long-term prediction and interpretation of extreme significant wave height events","authors":"C. Peláez-Rodríguez , J. Pérez-Aracil , A.M. Gómez-Orellana , D. Guijo-Rubio , V.M. Vargas , P.A. Gutiérrez , C. Hervás-Martínez , S. Salcedo-Sanz","doi":"10.1016/j.apor.2024.104273","DOIUrl":"10.1016/j.apor.2024.104273","url":null,"abstract":"<div><div>Providing an accurate prediction of Significant Wave Height (SWH), and specially of extreme SWH events, is crucial for coastal engineering activities and holds major implications in several sectors as offshore renewable energy. With the aim of overcoming the challenge of skewness and imbalance associated with the prediction of these extreme SWH events, a fuzzy-based cascade ensemble of regression models is proposed. This methodology allows to remarkably improve the predictive performance on the extreme SWH values, by using different models specialised in different ranges on the target domain. The method’s explainability is enhanced by analysing the contribution of each model, aiding in identifying those predictor variables more characteristic for the detection of extreme SWH events. The methodology has been validated tackling a long-term SWH prediction problem, considering two case studies over the southwest coast of the United States of America. Both reanalysis data, providing information on various meteorological factors, and SWH measurements, obtained from the nearby stations and the station under examination, have been considered. The goodness of the proposed approach has been validated by comparing its performance against several machine learning and deep learning regression techniques, leading to the conclusion that fuzzy ensemble models perform much better in the prediction of extreme events, at the cost of a slight deterioration in the rest of the samples. The study contributes to advancing the SWH prediction field, specially, to understanding the behaviour behind extreme SWH events, critical for various sectors reliant on oceanic conditions.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"153 ","pages":"Article 104273"},"PeriodicalIF":4.3,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527400","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 : 2024-10-25DOI: 10.1016/j.apor.2024.104276
Andrei M. Ermakov , Jack L. Rose-Butcher , John V. Ringwood
The article evaluates the potential of the Fano resonance operational principle in wave energy converters (WECs), using a 2-body loosely moored self-referenced WEC as an illustrative example. By leveraging Fano resonance, the point absorber buoy can remain relatively stationary with low loading on mooring lines, serving as an efficient wave energy transmitter while concurrently achieving resonance within the internal power take-off (PTO) system. This arrangement reduces the motion of the point absorber hull, thereby decreasing loads on the WEC structure, mooring lines, and anchors. As a result, operational and structural costs are minimised, further reducing the levelised costs of generated energy. Additionally, by ensuring minimal fluctuations in the WEC, confidence in using traditional linear mathematical models is increased, as commonly employed for WEC performance assessment and control design.
The article presents a resonance study and introduces newly derived solutions in the frequency domain for the proposed operational concept. It analytically demonstrates the viability of employing the Fano resonance operational strategy for WECs, suggesting that this strategy has the potential to compete with traditional methods of wave energy transformation. Furthermore, the insights gained from the study contribute to identifying optimal parameters for a PTO system, as well as optimising the design of the heaving buoy.
{"title":"On the value of Fano resonance in wave energy converters","authors":"Andrei M. Ermakov , Jack L. Rose-Butcher , John V. Ringwood","doi":"10.1016/j.apor.2024.104276","DOIUrl":"10.1016/j.apor.2024.104276","url":null,"abstract":"<div><div>The article evaluates the potential of the Fano resonance operational principle in wave energy converters (WECs), using a 2-body loosely moored self-referenced WEC as an illustrative example. By leveraging Fano resonance, the point absorber buoy can remain relatively stationary with low loading on mooring lines, serving as an efficient wave energy transmitter while concurrently achieving resonance within the internal power take-off (PTO) system. This arrangement reduces the motion of the point absorber hull, thereby decreasing loads on the WEC structure, mooring lines, and anchors. As a result, operational and structural costs are minimised, further reducing the levelised costs of generated energy. Additionally, by ensuring minimal fluctuations in the WEC, confidence in using traditional linear mathematical models is increased, as commonly employed for WEC performance assessment and control design.</div><div>The article presents a resonance study and introduces newly derived solutions in the frequency domain for the proposed operational concept. It analytically demonstrates the viability of employing the Fano resonance operational strategy for WECs, suggesting that this strategy has the potential to compete with traditional methods of wave energy transformation. Furthermore, the insights gained from the study contribute to identifying optimal parameters for a PTO system, as well as optimising the design of the heaving buoy.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"153 ","pages":"Article 104276"},"PeriodicalIF":4.3,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527462","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 : 2024-10-23DOI: 10.1016/j.apor.2024.104269
Yifan Dong , Wei Han , Rennian Li , Haozhi Nan , Xiaobo Shen , Shiqi Yang , Lu Bai
The loading characteristics of underwater explosions and the dynamic behavior of bubbles are directly related to the charge structure. This study proposes a unique charge structure in a gas–liquid two-phase fluid domain. Numerical methods are used to investigate the effects of fluid layer thickness and gas–liquid ratio on underwater explosion shock wave load, bubble dynamics, and bubble pulsation load. The results show that the two-phase fluid layer significantly enhances the directional release of shock wave energy and bubble pulsation load. During the shock wave phase, a lagging wave effect appears in the liquid layer direction, causing a secondary high-energy shock, significantly increasing the specific impulse. The gas layer direction may form a pressure relief channel effect, enhancing the shock wave peak pressure. For the bubble motion phase, differences in the physical properties of the fluid layer medium lead to irregular bubble boundary movements, promoting bubble tearing and rupture. The gaseous medium converts the accumulated shock wave energy into the internal energy of the bubble, increasing its volume potential. Although this characteristic reduces the pulsation frequency, it significantly increases the specific impulse. Altering the fluid layer medium can control explosion loads and bubble movement, offering new insights for ocean engineering applications.
{"title":"Directional enhancement of underwater impact and bubble loads in neighbor two-phase fluid domains charge","authors":"Yifan Dong , Wei Han , Rennian Li , Haozhi Nan , Xiaobo Shen , Shiqi Yang , Lu Bai","doi":"10.1016/j.apor.2024.104269","DOIUrl":"10.1016/j.apor.2024.104269","url":null,"abstract":"<div><div>The loading characteristics of underwater explosions and the dynamic behavior of bubbles are directly related to the charge structure. This study proposes a unique charge structure in a gas–liquid two-phase fluid domain. Numerical methods are used to investigate the effects of fluid layer thickness and gas–liquid ratio on underwater explosion shock wave load, bubble dynamics, and bubble pulsation load. The results show that the two-phase fluid layer significantly enhances the directional release of shock wave energy and bubble pulsation load. During the shock wave phase, a lagging wave effect appears in the liquid layer direction, causing a secondary high-energy shock, significantly increasing the specific impulse. The gas layer direction may form a pressure relief channel effect, enhancing the shock wave peak pressure. For the bubble motion phase, differences in the physical properties of the fluid layer medium lead to irregular bubble boundary movements, promoting bubble tearing and rupture. The gaseous medium converts the accumulated shock wave energy into the internal energy of the bubble, increasing its volume potential. Although this characteristic reduces the pulsation frequency, it significantly increases the specific impulse. Altering the fluid layer medium can control explosion loads and bubble movement, offering new insights for ocean engineering applications.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"153 ","pages":"Article 104269"},"PeriodicalIF":4.3,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527461","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-23DOI: 10.1016/j.apor.2024.104271
Tongshun Yu , Xin Tong , Xuguang Chen , Haoyang Song , Xuewen Zhao , Yuqiao Wang
Addressing the overlooked uncertainties and stochastic elements in prior studies on scour prediction, this research introduces a probabilistic prediction model for the scour depth around monopile foundations. To enhance the accuracy of the model, the M5’ model tree method was employed to construct a deterministic prediction formula, which was then evaluated using statistical indicators for performance. To address the issue of discontinuities within the deterministic formula, a continuity treatment was applied to improve the credibility of the formula. Expanding on the deterministic formula, a probabilistic model for estimating the local scour depth around a monopile subjected to combined wave and current conditions was developed using Monte Carlo simulations. These simulations integrated specific random parameters into the deterministic model, allowing for the assessment of how these parameters influence the failure probability. The results indicate that the M5’ model tree algorithm can effectively predict the equilibrium scour depth of a monopile under the influence of waves and currents, and the formula, post-continuity treatment, demonstrates enhanced credibility and applicability. Furthermore, the study indicates that the failure probability of a monopile escalates in relation to the increase in near-bed current velocity and the rise in maximum bed surface orbital velocity. It was also discovered that within a specific Froude number range, a consistently low failure probability is maintained, a conclusion that provides a reference for the design of monopile foundations.
{"title":"Prediction of scour depth around monopiles in combined waves and current: A probabilistic assessment of M5’-MCS","authors":"Tongshun Yu , Xin Tong , Xuguang Chen , Haoyang Song , Xuewen Zhao , Yuqiao Wang","doi":"10.1016/j.apor.2024.104271","DOIUrl":"10.1016/j.apor.2024.104271","url":null,"abstract":"<div><div>Addressing the overlooked uncertainties and stochastic elements in prior studies on scour prediction, this research introduces a probabilistic prediction model for the scour depth around monopile foundations. To enhance the accuracy of the model, the M5’ model tree method was employed to construct a deterministic prediction formula, which was then evaluated using statistical indicators for performance. To address the issue of discontinuities within the deterministic formula, a continuity treatment was applied to improve the credibility of the formula. Expanding on the deterministic formula, a probabilistic model for estimating the local scour depth around a monopile subjected to combined wave and current conditions was developed using Monte Carlo simulations. These simulations integrated specific random parameters into the deterministic model, allowing for the assessment of how these parameters influence the failure probability. The results indicate that the M5’ model tree algorithm can effectively predict the equilibrium scour depth of a monopile under the influence of waves and currents, and the formula, post-continuity treatment, demonstrates enhanced credibility and applicability. Furthermore, the study indicates that the failure probability of a monopile escalates in relation to the increase in near-bed current velocity and the rise in maximum bed surface orbital velocity. It was also discovered that within a specific Froude number range, a consistently low failure probability is maintained, a conclusion that provides a reference for the design of monopile foundations.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"153 ","pages":"Article 104271"},"PeriodicalIF":4.3,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-22DOI: 10.1016/j.apor.2024.104281
Shan Gao , Yao Shi , Pengcheng Ye , Shuai Zhang , Guang Pan
This paper analyzes the effect of launch interval on cavitation flow interference and load characteristics during underwater salvo. The study employs the Improved Delayed Detached Eddy Simulation and the Schnerr-Sauer cavitation model, Volume of Fluid (VOF) multiphase flow model, and overlapping grid. Additionally, decompression experiment systems are designed, and numerical simulations are found to be in good agreement with experimental results, thus verifying the effectiveness of the simulation. Detailed discussions are provided on multiphase flow field and load distribution. The results reveal a top-down collapse process of the cavity, with collapse shrinking to an isolated bubble at the end. Synchronized collapse pressure is characterized by short pulse widths at the peaks, all located at the lowermost part of the cavity. During the underwater stage, when the axial launch spacing ranges between 0.5 times and 1.0 times the length of the projectile, the head of the second projectile acts on the area below the center of mass of the first. This leads to gradual stabilization of the initial cavity and a decrease in deviation of the center of mass toward the inside. Despite experiencing large-scale fracture and detachment due to interference from the wake of the first engine, the motion stability of the inside cavity of the second projectile remains intact. In the water exit stage, when the axial launch spacing ranges between 0.75 times and 1 time the length of the projectile, it causes expansion and contraction of the inside cavity of the second projectile. However, asymmetric synchronous collapse loads may occur, leading to unstable motion posture.
{"title":"Effects of axial launch spacing on cavitation interference and load characteristics during underwater salvo","authors":"Shan Gao , Yao Shi , Pengcheng Ye , Shuai Zhang , Guang Pan","doi":"10.1016/j.apor.2024.104281","DOIUrl":"10.1016/j.apor.2024.104281","url":null,"abstract":"<div><div>This paper analyzes the effect of launch interval on cavitation flow interference and load characteristics during underwater salvo. The study employs the Improved Delayed Detached Eddy Simulation and the Schnerr-Sauer cavitation model, Volume of Fluid (VOF) multiphase flow model, and overlapping grid. Additionally, decompression experiment systems are designed, and numerical simulations are found to be in good agreement with experimental results, thus verifying the effectiveness of the simulation. Detailed discussions are provided on multiphase flow field and load distribution. The results reveal a top-down collapse process of the cavity, with collapse shrinking to an isolated bubble at the end. Synchronized collapse pressure is characterized by short pulse widths at the peaks, all located at the lowermost part of the cavity. During the underwater stage, when the axial launch spacing ranges between 0.5 times and 1.0 times the length of the projectile, the head of the second projectile acts on the area below the center of mass of the first. This leads to gradual stabilization of the initial cavity and a decrease in deviation of the center of mass toward the inside. Despite experiencing large-scale fracture and detachment due to interference from the wake of the first engine, the motion stability of the inside cavity of the second projectile remains intact. In the water exit stage, when the axial launch spacing ranges between 0.75 times and 1 time the length of the projectile, it causes expansion and contraction of the inside cavity of the second projectile. However, asymmetric synchronous collapse loads may occur, leading to unstable motion posture.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"153 ","pages":"Article 104281"},"PeriodicalIF":4.3,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527459","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-21DOI: 10.1016/j.apor.2024.104272
Fanglin Cong , Runbo Zhang , Wendong Li , Yang Jin , Guocai Yu , Linzhi Wu
Cylindrical shell structures are widely used in various engineering fields. In this study, the hydrostatic buckling behavior of moderately thick composite cylindrical shells is studied. A theoretical model based on the first-order shear deformation theory is established and its validity was verified by comparison with experimental data. Furthermore, the failure mechanism of moderately thick cylindrical shell is analyzed by experiments and simulations. It is analytically confirmed that the failure mode of moderately thick cylindrical shells changes as the length-to-radius ratio and the radius-to-thickness ratio decreases. Subsequently, the effects of size, stacking sequence, and ply angle on buckling behavior are discussed and parameter optimization is implemented analytically for engineering design. The results indicate that the critical hydrostatic buckling strength increases by more than 18.55 % by parameter optimization. The research results provide a useful reference for the design and optimization of underwater pressure-resistant shells.
{"title":"Buckling analysis of moderately thick carbon fiber composite cylindrical shells under hydrostatic pressure","authors":"Fanglin Cong , Runbo Zhang , Wendong Li , Yang Jin , Guocai Yu , Linzhi Wu","doi":"10.1016/j.apor.2024.104272","DOIUrl":"10.1016/j.apor.2024.104272","url":null,"abstract":"<div><div>Cylindrical shell structures are widely used in various engineering fields. In this study, the hydrostatic buckling behavior of moderately thick composite cylindrical shells is studied. A theoretical model based on the first-order shear deformation theory is established and its validity was verified by comparison with experimental data. Furthermore, the failure mechanism of moderately thick cylindrical shell is analyzed by experiments and simulations. It is analytically confirmed that the failure mode of moderately thick cylindrical shells changes as the length-to-radius ratio and the radius-to-thickness ratio decreases. Subsequently, the effects of size, stacking sequence, and ply angle on buckling behavior are discussed and parameter optimization is implemented analytically for engineering design. The results indicate that the critical hydrostatic buckling strength increases by more than 18.55 % by parameter optimization. The research results provide a useful reference for the design and optimization of underwater pressure-resistant shells.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"153 ","pages":"Article 104272"},"PeriodicalIF":4.3,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527458","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-19DOI: 10.1016/j.apor.2024.104279
Pu Xuan, Hui Du, Shaodong Wang, Pai Peng, Gang Wei
It is essential to give the applicable range of nonlinear theories of the internal solitary wave in different classification conditions and water depth. The nonlinear theories used to describe the ISW, including KdV, eKdV and MCC theories were compared with experimental results. The characteristic parameters of ISW (waveform, phase speed, and wave frequency) and its load on slender body were chosen to provide a quantitatively applicable range of three nonlinear theories at different water depths. In general, the optimal theories are KdV, eKdV and MCC in turns for most conditions. However, for the description of phase speed, both the eKdV and MCC theories can describe it well, where the KdV theory has a large error in describing phase speed at large ISW amplitude. For the vertical force, the KdV and eKdV theories can describe it well in turns, while the MCC theory has a large error in calculating the vertical force. A diagram of the applicable range under different classification conditions and at different water depths is proposed for choosing a better theory in different fields.
{"title":"The applicability of nonlinear theories of the internal solitary wave and its loads on slender body by experimental methods","authors":"Pu Xuan, Hui Du, Shaodong Wang, Pai Peng, Gang Wei","doi":"10.1016/j.apor.2024.104279","DOIUrl":"10.1016/j.apor.2024.104279","url":null,"abstract":"<div><div>It is essential to give the applicable range of nonlinear theories of the internal solitary wave in different classification conditions and water depth. The nonlinear theories used to describe the ISW, including KdV, eKdV and MCC theories were compared with experimental results. The characteristic parameters of ISW (waveform, phase speed, and wave frequency) and its load on slender body were chosen to provide a quantitatively applicable range of three nonlinear theories at different water depths. In general, the optimal theories are KdV, eKdV and MCC in turns for most conditions. However, for the description of phase speed, both the eKdV and MCC theories can describe it well, where the KdV theory has a large error in describing phase speed at large ISW amplitude. For the vertical force, the KdV and eKdV theories can describe it well in turns, while the MCC theory has a large error in calculating the vertical force. A diagram of the applicable range under different classification conditions and at different water depths is proposed for choosing a better theory in different fields.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"153 ","pages":"Article 104279"},"PeriodicalIF":4.3,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527456","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-19DOI: 10.1016/j.apor.2024.104274
Dongxu Wang , Sheng Dong
Through numerical modelling, the hydrodynamic performance of a novel wave energy converter-breakwater integrated system, consisting of a perforated breakwater and a heaving wave energy converter (HWEC) in the wave absorption chamber, is investigated. A method for modelling the Coulomb damping force (CDF) provided by the power take-off system is established to address the instability problem caused by the sudden change of the CDF when the motion direction of the HWEC changes. Under the representative wave condition ( = 1.76, where is wave number and is water depth), the working mechanism of the integrated system is clarified, the preferable HWEC hull shape is found, and the nondimensional relationships for determining the geometric parameters are obtained. In addition, by performing the simulation with the waves of = 2.52 and = 1.11, the limits of the geometric parameters are proposed. It is found that the asymmetric HWEC having a seaward straight corner and leeward curved corner is preferable to minimize wave reflection and capture appreciable wave energy. Under the tested condition, when the nondimensional PTO damping force ranges from 0.5 to 1.25 and the response amplitude operator of the HWEC is no less than 0.3, the capture width ratio of the integrated system will mostly exceed 0.3, and the reflected energy will be quite low.
{"title":"Two-dimensional numerical modelling of a novel heaving wave energy converter-perforated breakwater integrated system","authors":"Dongxu Wang , Sheng Dong","doi":"10.1016/j.apor.2024.104274","DOIUrl":"10.1016/j.apor.2024.104274","url":null,"abstract":"<div><div>Through numerical modelling, the hydrodynamic performance of a novel wave energy converter-breakwater integrated system, consisting of a perforated breakwater and a heaving wave energy converter (HWEC) in the wave absorption chamber, is investigated. A method for modelling the Coulomb damping force (CDF) provided by the power take-off system is established to address the instability problem caused by the sudden change of the CDF when the motion direction of the HWEC changes. Under the representative wave condition (<span><math><mrow><mi>k</mi><mi>d</mi></mrow></math></span> = 1.76, where <span><math><mi>k</mi></math></span> is wave number and <span><math><mi>d</mi></math></span> is water depth), the working mechanism of the integrated system is clarified, the preferable HWEC hull shape is found, and the nondimensional relationships for determining the geometric parameters are obtained. In addition, by performing the simulation with the waves of <span><math><mrow><mi>k</mi><mi>d</mi></mrow></math></span> = 2.52 and <span><math><mrow><mi>k</mi><mi>d</mi></mrow></math></span> = 1.11, the limits of the geometric parameters are proposed. It is found that the asymmetric HWEC having a seaward straight corner and leeward curved corner is preferable to minimize wave reflection and capture appreciable wave energy. Under the tested condition, when the nondimensional PTO damping force ranges from 0.5 to 1.25 and the response amplitude operator of the HWEC is no less than 0.3, the capture width ratio of the integrated system will mostly exceed 0.3, and the reflected energy will be quite low.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"153 ","pages":"Article 104274"},"PeriodicalIF":4.3,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527457","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}
The construction of artificial island can greatly change the reef hydrodynamics, leading to increased water level and wave height as well as changes in flow field distribution. These alterations can affect sediment transport on the reef, and increase the risk of overtopping and structure instability. A numerical model based on the Reynolds Averaged Navier-Stokes (RANS) equations and k-ε turbulence closure model was developed to investigate the influence of artificial island on reef hydrodynamics. The numerical model was validated against the experimental results of wave height, mean water level, and wave breaking morphology. Detailed flow field, wave height, and wave set-up in front of artificial island were further analyzed based on the validated model. After building the reef-top structure, the wave breaking and offshore currents at reef edge were amplified. The flow stratification and increase of the wave set-up were also found on the reef flat. Furthermore, we found the relationship between maximum flow velocities on the reef flat and incoming wave conditions could be characterized by two non-dimensional parameters: , .
{"title":"Numerical simulation on the influence of artificial island on reef hydrodynamics","authors":"Gancheng Zhu , Bing Ren , Hongjie Wen , Pengzhi Lin","doi":"10.1016/j.apor.2024.104266","DOIUrl":"10.1016/j.apor.2024.104266","url":null,"abstract":"<div><div>The construction of artificial island can greatly change the reef hydrodynamics, leading to increased water level and wave height as well as changes in flow field distribution. These alterations can affect sediment transport on the reef, and increase the risk of overtopping and structure instability. A numerical model based on the Reynolds Averaged Navier-Stokes (RANS) equations and <em>k</em>-<em>ε</em> turbulence closure model was developed to investigate the influence of artificial island on reef hydrodynamics. The numerical model was validated against the experimental results of wave height, mean water level, and wave breaking morphology. Detailed flow field, wave height, and wave set-up in front of artificial island were further analyzed based on the validated model. After building the reef-top structure, the wave breaking and offshore currents at reef edge were amplified. The flow stratification and increase of the wave set-up were also found on the reef flat. Furthermore, we found the relationship between maximum flow velocities on the reef flat and incoming wave conditions could be characterized by two non-dimensional parameters: <span><math><mrow><msub><mrow><mrow><mo>|</mo></mrow><mover><mi>u</mi><mo>¯</mo></mover><mrow><mo>|</mo></mrow></mrow><mtext>max</mtext></msub><mo>/</mo><msqrt><mrow><mi>g</mi><mo>(</mo><mover><mi>η</mi><mo>¯</mo></mover><mo>+</mo><msub><mi>h</mi><mi>r</mi></msub><mo>)</mo></mrow></msqrt></mrow></math></span>, <span><math><mrow><mrow><mo>(</mo><mover><mi>η</mi><mo>¯</mo></mover><mo>+</mo><msub><mi>h</mi><mi>r</mi></msub><mo>)</mo></mrow><mo>/</mo><msub><mi>H</mi><mi>i</mi></msub></mrow></math></span>.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":"153 ","pages":"Article 104266"},"PeriodicalIF":4.3,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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