Pub Date : 2024-10-23DOI: 10.1016/j.apor.2024.104271
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":"","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":null,"pages":null},"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
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":"","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":null,"pages":null},"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
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":"","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":null,"pages":null},"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
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":"","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":null,"pages":null},"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
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":"","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":null,"pages":null},"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}
Pub Date : 2024-10-18DOI: 10.1016/j.apor.2024.104266
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":"","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":null,"pages":null},"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}
Pub Date : 2024-10-18DOI: 10.1016/j.apor.2024.104263
<div><div>The water-drop shaped fairings with varying shape angles are attached to a circular cylinder to achieve wake control and vortex suppression at critical Reynolds numbers. To ensure the capability of Reynolds averaged Navier–Stokes (RANS), detached eddy simulation (DES) and large eddy simulation (LES) models at the critical Reynolds number region, three representative turbulence models are employed: LES with <span><math><mi>σ</mi></math></span> subgrid-scale (SGS) model, delayed DES model with improved wall-modeling capability (IDDES) and shear stress transport (SST) <span><math><mrow><mi>k</mi><mo>−</mo><mi>ω</mi></mrow></math></span> RANS model. These models are utilized to simulate flow around a circular cylinder at Reynolds number <span><math><mrow><mtext>Re</mtext><mo>=</mo><mn>2</mn><mo>.</mo><mn>5</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span>. The solver used in this paper is further developed based on the high-resolution algorithm platform for incompressible flow (HRAPIF). The comparative analysis of the results from the three turbulence models has been rigorously validated and investigated. An exhaustive examination of the mean flow field, Reynolds stresses, characteristic lengths, and instantaneous flow fields among the models reveals instructive insights. The IDDES and <span><math><mi>σ</mi></math></span>-LES models predict the hydrodynamic forces, the so-called ‘drag crisis’, alongside the pressure distribution and skin friction coefficient with high precision. The <span><math><mi>σ</mi></math></span>-LES model stands out for its superior accuracy, while the IDDES model is also a viable alternative, offering commendable accuracy with a reduced demand for mesh density. Subsequently, the IDDES model is selected for wake control calculations using fairings with five distinct shape angles (<span><math><mrow><mn>3</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>∘</mo></mrow></msup><mo>,</mo><mn>4</mn><msup><mrow><mn>5</mn></mrow><mrow><mo>∘</mo></mrow></msup><mo>,</mo><mn>6</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>∘</mo></mrow></msup><mo>,</mo><mn>7</mn><msup><mrow><mn>5</mn></mrow><mrow><mo>∘</mo></mrow></msup></mrow></math></span> and <span><math><mrow><mn>9</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>∘</mo></mrow></msup></mrow></math></span>) at <span><math><mrow><mtext>Re</mtext><mo>=</mo><mn>2</mn><mo>.</mo><mn>5</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span>. In-depth comparisons to the bare cylinder and subcritical results reveal that the wake control effect varies at the critical Reynolds region. The fairing with a 30° shape angle substantially suppresses hydrodynamic forces. The lift coefficient experiences a remarkable decrease of approximately 96%, while the drag coefficient diminishes by about 90%. Concurrently, fairings with angles from 45° to 90° lead to reductions in drag coefficient of 11.6%, 10%, 3% and
{"title":"Turbulence model adaptability at critical Reynolds numbers and applications in wake control via fairings","authors":"","doi":"10.1016/j.apor.2024.104263","DOIUrl":"10.1016/j.apor.2024.104263","url":null,"abstract":"<div><div>The water-drop shaped fairings with varying shape angles are attached to a circular cylinder to achieve wake control and vortex suppression at critical Reynolds numbers. To ensure the capability of Reynolds averaged Navier–Stokes (RANS), detached eddy simulation (DES) and large eddy simulation (LES) models at the critical Reynolds number region, three representative turbulence models are employed: LES with <span><math><mi>σ</mi></math></span> subgrid-scale (SGS) model, delayed DES model with improved wall-modeling capability (IDDES) and shear stress transport (SST) <span><math><mrow><mi>k</mi><mo>−</mo><mi>ω</mi></mrow></math></span> RANS model. These models are utilized to simulate flow around a circular cylinder at Reynolds number <span><math><mrow><mtext>Re</mtext><mo>=</mo><mn>2</mn><mo>.</mo><mn>5</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span>. The solver used in this paper is further developed based on the high-resolution algorithm platform for incompressible flow (HRAPIF). The comparative analysis of the results from the three turbulence models has been rigorously validated and investigated. An exhaustive examination of the mean flow field, Reynolds stresses, characteristic lengths, and instantaneous flow fields among the models reveals instructive insights. The IDDES and <span><math><mi>σ</mi></math></span>-LES models predict the hydrodynamic forces, the so-called ‘drag crisis’, alongside the pressure distribution and skin friction coefficient with high precision. The <span><math><mi>σ</mi></math></span>-LES model stands out for its superior accuracy, while the IDDES model is also a viable alternative, offering commendable accuracy with a reduced demand for mesh density. Subsequently, the IDDES model is selected for wake control calculations using fairings with five distinct shape angles (<span><math><mrow><mn>3</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>∘</mo></mrow></msup><mo>,</mo><mn>4</mn><msup><mrow><mn>5</mn></mrow><mrow><mo>∘</mo></mrow></msup><mo>,</mo><mn>6</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>∘</mo></mrow></msup><mo>,</mo><mn>7</mn><msup><mrow><mn>5</mn></mrow><mrow><mo>∘</mo></mrow></msup></mrow></math></span> and <span><math><mrow><mn>9</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>∘</mo></mrow></msup></mrow></math></span>) at <span><math><mrow><mtext>Re</mtext><mo>=</mo><mn>2</mn><mo>.</mo><mn>5</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span>. In-depth comparisons to the bare cylinder and subcritical results reveal that the wake control effect varies at the critical Reynolds region. The fairing with a 30° shape angle substantially suppresses hydrodynamic forces. The lift coefficient experiences a remarkable decrease of approximately 96%, while the drag coefficient diminishes by about 90%. Concurrently, fairings with angles from 45° to 90° lead to reductions in drag coefficient of 11.6%, 10%, 3% and ","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":null,"pages":null},"PeriodicalIF":4.3,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527452","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 : 2024-10-18DOI: 10.1016/j.apor.2024.104268
The free spanning submarine cable, a slender and flexible structure with a certain sag, exhibits unique vortex-induced vibration (VIV) characteristics in currents compared to offshore risers and submarine pipelines. To study the VIV of the cable, a three-dimensional numerical model based on the finite difference method (FDM) and the finite element method (FEM) is established. The large eddy simulation method is employed to close the turbulent motion equations in the hydrodynamic model, while the beam element method is used to solve the structural motion equations in the structural dynamic model. An analytical mapping method is adopted for the reconstruction of the structure surface in the fixed Cartesian fluid grids, and the immersed boundary method is used to deal with boundary conditions at fluid-solid interfaces. Since simulating VIV of a submarine cable with sag requires extensive local grid refinement near the cable's surface, a partition parallel algorithm with multi-GPU nodes is developed to enhance the computational efficiency, where the parallel efficiency of a single GPU can reach 80–90%. The numerical model is validated by a laboratory experiment on the VIV of a submarine cable, where the transverse response amplitudes and frequencies obtained by numerical simulation agree well with the experimental results. The streamwise vibration responses that are not measured in the experiment are analyzed by the numerical simulation. It is found that when the cable's equilibrium profile is deflected in the streamwise direction by the drag force, the streamwise vibration with the same frequency as the transverse vibration occurs, and the streamwise vibration amplitude increases with sag. The detailed flow field information provided by numerical simulation indicates that the size of the vortex structures gradually increases with the velocity, and the shape of the vortex structure has a strong correlation with the transverse vibration mode of the cable.
{"title":"Three-dimensional numerical simulation of vortex-induced vibration of a free spanning submarine cable in uniform currents","authors":"","doi":"10.1016/j.apor.2024.104268","DOIUrl":"10.1016/j.apor.2024.104268","url":null,"abstract":"<div><div>The free spanning submarine cable, a slender and flexible structure with a certain sag, exhibits unique vortex-induced vibration (VIV) characteristics in currents compared to offshore risers and submarine pipelines. To study the VIV of the cable, a three-dimensional numerical model based on the finite difference method (FDM) and the finite element method (FEM) is established. The large eddy simulation method is employed to close the turbulent motion equations in the hydrodynamic model, while the beam element method is used to solve the structural motion equations in the structural dynamic model. An analytical mapping method is adopted for the reconstruction of the structure surface in the fixed Cartesian fluid grids, and the immersed boundary method is used to deal with boundary conditions at fluid-solid interfaces. Since simulating VIV of a submarine cable with sag requires extensive local grid refinement near the cable's surface, a partition parallel algorithm with multi-GPU nodes is developed to enhance the computational efficiency, where the parallel efficiency of a single GPU can reach 80–90%. The numerical model is validated by a laboratory experiment on the VIV of a submarine cable, where the transverse response amplitudes and frequencies obtained by numerical simulation agree well with the experimental results. The streamwise vibration responses that are not measured in the experiment are analyzed by the numerical simulation. It is found that when the cable's equilibrium profile is deflected in the streamwise direction by the drag force, the streamwise vibration with the same frequency as the transverse vibration occurs, and the streamwise vibration amplitude increases with sag. The detailed flow field information provided by numerical simulation indicates that the size of the vortex structures gradually increases with the velocity, and the shape of the vortex structure has a strong correlation with the transverse vibration mode of the cable.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":null,"pages":null},"PeriodicalIF":4.3,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527453","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 : 2024-10-18DOI: 10.1016/j.apor.2024.104277
At present, the energy released by bubble collapse can be used for the surface treatment of workpieces and can also be used to degrade pollutants. However, the mechanism of action between bubble collapse and a nearby wall has yet to be accurately explained. In order to grasp the relationship between the wall distance and collapse characteristics, the methods of spark discharge, high-speed photography, and pressure acquisition are used to study bubble shapes and the dynamic variation during pressure release with different wall distances in this paper. The results show that with the increasing of the distance L, the shape of a bubble changes from oblate to spherical and its collapse time shortens. The proportion of the total collapse time consumed by the slow collapse stage shows an increasing trend. In an experiment with two contractions, the time proportion of the slow collapse stage of the first contraction is much larger than that of the second contraction. The existence of the wall delays the collapse of the bubble. As the distance L increases, the bubble goes from undergoing one collapse to two collapses and then to one collapse again. The proportion of the duration of the slow collapse stage of the first contraction decreases rapidly, and the proportion of the slow collapse stage of the second contraction increases slowly, but the time proportion of second contraction decreases. When the distance L increases from 4.5 mm to 11 mm, the pressure received by the wall gradually decreases 28.19 MPa to 18.01 MPa. With an increase in the distance S from 0 to 8 mm, the maximum pressure received by the wall gradually decreases from 19.77 MPa to 9.37 MPa. The relationship found between the slow collapse stage (ta), the second contraction (tb), and the distance (L) can provide guidance for the effective application of the energy released by bubble collapse.
目前，气泡坍塌释放的能量可用于工件的表面处理，也可用于降解污染物。然而，气泡塌陷与附近壁面之间的作用机理尚未得到准确解释。为了掌握壁距与塌陷特性之间的关系，本文采用火花放电、高速摄影和压力采集等方法，研究了不同壁距下的气泡形状和压力释放过程中的动态变化。结果表明，随着壁距 L 的增大，气泡的形状由扁圆形变为球形，塌陷时间缩短。缓慢坍缩阶段所消耗的时间占总坍缩时间的比例呈上升趋势。在两次收缩的实验中，第一次收缩的慢速塌缩阶段所占的时间比例远远大于第二次收缩。气泡壁的存在延迟了气泡的坍缩。随着距离 L 的增加，气泡会从一次塌缩变成两次塌缩，然后再变成一次塌缩。第一次收缩的缓慢塌缩阶段的持续时间比例迅速减少，第二次收缩的缓慢塌缩阶段的比例缓慢增加，但第二次收缩的时间比例减少。当距离 L 从 4.5 mm 增加到 11 mm 时，壁面承受的压力逐渐从 28.19 MPa 减小到 18.01 MPa。当距离 S 从 0 毫米增加到 8 毫米时，墙体承受的最大压力从 19.77 兆帕逐渐减小到 9.37 兆帕。缓慢塌陷阶段 (ta)、第二次收缩 (tb) 和距离 (L) 之间的关系可为有效利用气泡塌陷释放的能量提供指导。
{"title":"Experiments on the effect of wall distances for bubble collapse characteristics","authors":"","doi":"10.1016/j.apor.2024.104277","DOIUrl":"10.1016/j.apor.2024.104277","url":null,"abstract":"<div><div>At present, the energy released by bubble collapse can be used for the surface treatment of workpieces and can also be used to degrade pollutants. However, the mechanism of action between bubble collapse and a nearby wall has yet to be accurately explained. In order to grasp the relationship between the wall distance and collapse characteristics, the methods of spark discharge, high-speed photography, and pressure acquisition are used to study bubble shapes and the dynamic variation during pressure release with different wall distances in this paper. The results show that with the increasing of the distance <em>L</em>, the shape of a bubble changes from oblate to spherical and its collapse time shortens. The proportion of the total collapse time consumed by the slow collapse stage shows an increasing trend. In an experiment with two contractions, the time proportion of the slow collapse stage of the first contraction is much larger than that of the second contraction. The existence of the wall delays the collapse of the bubble. As the distance <em>L</em> increases, the bubble goes from undergoing one collapse to two collapses and then to one collapse again. The proportion of the duration of the slow collapse stage of the first contraction decreases rapidly, and the proportion of the slow collapse stage of the second contraction increases slowly, but the time proportion of second contraction decreases. When the distance <em>L</em> increases from 4.5 mm to 11 mm, the pressure received by the wall gradually decreases 28.19 MPa to 18.01 MPa. With an increase in the distance <em>S</em> from 0 to 8 mm, the maximum pressure received by the wall gradually decreases from 19.77 MPa to 9.37 MPa. The relationship found between the slow collapse stage (<em>t<sub>a</sub></em>), the second contraction (<em>t<sub>b</sub></em>), and the distance (<em>L</em>) can provide guidance for the effective application of the energy released by bubble collapse.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":null,"pages":null},"PeriodicalIF":4.3,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527402","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 : 2024-10-17DOI: 10.1016/j.apor.2024.104267
Flexible membranes are widely used in marine engineering, but how to calculate their hydrodynamic performance under wave action remains a challenging problem. In this paper, a new model based on the eigenfunction expansion boundary element method (EEBEM) is proposed to calculate the wave-membrane interaction under two-dimensional conditions. A general dynamic boundary condition suitable for linear and arcuate membranes is established based on the membrane’s constitutive equations under cylindrical coordinates. This condition considers the dynamic tension and curvature of the membrane, and an integral expression for the dynamic tension is also derived. Subsequently, the dynamic boundary condition is transformed into a function of the velocity potential and applied to the EEBEM, overcoming the difficulty of the coupled solutions for the arcuate membrane’s motion and the flow field. Moreover, a generalized solution framework for wave-structure interaction is established by constructing a fully closed form of the water wave equations, which effectively shortens the modeling time and expands the application scope. After verifying the accuracy and effectiveness of the model, the hydrodynamic performance (wave force, membrane tension and wave transmission coefficient) and motion response of a submerged flexible membrane breakwater (SFMB) are investigated. The results demonstrate that the model exhibits high accuracy, which is beneficial for elucidating the mechanism of wave-membrane interaction and providing robust support for related research fields.
{"title":"An effective boundary element model to calculate the interaction between waves and flexible membrane","authors":"","doi":"10.1016/j.apor.2024.104267","DOIUrl":"10.1016/j.apor.2024.104267","url":null,"abstract":"<div><div>Flexible membranes are widely used in marine engineering, but how to calculate their hydrodynamic performance under wave action remains a challenging problem. In this paper, a new model based on the eigenfunction expansion boundary element method (EEBEM) is proposed to calculate the wave-membrane interaction under two-dimensional conditions. A general dynamic boundary condition suitable for linear and arcuate membranes is established based on the membrane’s constitutive equations under cylindrical coordinates. This condition considers the dynamic tension and curvature of the membrane, and an integral expression for the dynamic tension is also derived. Subsequently, the dynamic boundary condition is transformed into a function of the velocity potential and applied to the EEBEM, overcoming the difficulty of the coupled solutions for the arcuate membrane’s motion and the flow field. Moreover, a generalized solution framework for wave-structure interaction is established by constructing a fully closed form of the water wave equations, which effectively shortens the modeling time and expands the application scope. After verifying the accuracy and effectiveness of the model, the hydrodynamic performance (wave force, membrane tension and wave transmission coefficient) and motion response of a submerged flexible membrane breakwater (SFMB) are investigated. The results demonstrate that the model exhibits high accuracy, which is beneficial for elucidating the mechanism of wave-membrane interaction and providing robust support for related research fields.</div></div>","PeriodicalId":8261,"journal":{"name":"Applied Ocean Research","volume":null,"pages":null},"PeriodicalIF":4.3,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142445862","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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