Miao Wang, Ming Hai, Anshuang Su, S. Meng, Hailong Mu, Yanxiu Guo
Engineering usually considers coarse-grained soils as nonfrost swelling soils, but serious frost swelling still occurs in coarse-grained canal bases, which is directly related to the recharge conditions and the fine particle content in the soil. Little attention is currently paid to the effect of different fine particle contents on coarse-grained soil frost swelling, especially after the fine particle admixture content exceeds 16%. This paper considers the characteristics of coarse-grained soils in water conservancy projects with fines content between 0% and 50%. The coarse-grained soils with 5%, 15%, 25%, 35% and 45% fines content were designed for freezing and swelling tests. The evolution of temperature and moisture fields and the amount of freezing and swelling of coarse-grained soils during the freezing process were studied by using servo-type freezing and swelling and thawing tester. The experimental results show that the cooling process of soil samples can be divided into a rapid cooling stage, a slow cooling stage and a freezing stabilization stage. The cooling rate and the frost heave amount with increasing fines content showed a trend of first increasing and then decreasing.
{"title":"Experimental study on the effect of fines content on the frost swelling characteristics of coarse-grained soil in canal base under open system","authors":"Miao Wang, Ming Hai, Anshuang Su, S. Meng, Hailong Mu, Yanxiu Guo","doi":"10.1115/1.4062931","DOIUrl":"https://doi.org/10.1115/1.4062931","url":null,"abstract":"\u0000 Engineering usually considers coarse-grained soils as nonfrost swelling soils, but serious frost swelling still occurs in coarse-grained canal bases, which is directly related to the recharge conditions and the fine particle content in the soil. Little attention is currently paid to the effect of different fine particle contents on coarse-grained soil frost swelling, especially after the fine particle admixture content exceeds 16%. This paper considers the characteristics of coarse-grained soils in water conservancy projects with fines content between 0% and 50%. The coarse-grained soils with 5%, 15%, 25%, 35% and 45% fines content were designed for freezing and swelling tests. The evolution of temperature and moisture fields and the amount of freezing and swelling of coarse-grained soils during the freezing process were studied by using servo-type freezing and swelling and thawing tester. The experimental results show that the cooling process of soil samples can be divided into a rapid cooling stage, a slow cooling stage and a freezing stabilization stage. The cooling rate and the frost heave amount with increasing fines content showed a trend of first increasing and then decreasing.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43853232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Surface gravity wave interaction of composite wavy porous plate is studied by developing a numerical model using the boundary element method in the context of two-dimensional linear potential theory. Bragg scattering phenomenon is studied by considering the linearized pressure drop condition known as Darcy's law passing through the porous structure. Numerical results are obtained through the boundary element method for the special limiting case of the existing previous literature to authenticate the accuracy of the numerical solution. The influence of wave and structural design parameters such as the number of ripple wavelengths of the wavy plate, relative plate length, structural porosities and relative submergence depth on hydrodynamics properties such as reflection, transmission, horizontal wave load and vertical wave coefficients are discussed. The study results of composite wavy porous plate indicate improved hydrodynamic performance as compared to the horizontal porous plate and wavy porous plate. This study is significant for practical applications in coastal engineering environments.
{"title":"Bragg scattering of surface gravity waves by a submerged composite wavy porous plate","authors":"A. K. Mohapatra, T. Sahoo","doi":"10.1115/1.4062897","DOIUrl":"https://doi.org/10.1115/1.4062897","url":null,"abstract":"\u0000 Surface gravity wave interaction of composite wavy porous plate is studied by developing a numerical model using the boundary element method in the context of two-dimensional linear potential theory. Bragg scattering phenomenon is studied by considering the linearized pressure drop condition known as Darcy's law passing through the porous structure. Numerical results are obtained through the boundary element method for the special limiting case of the existing previous literature to authenticate the accuracy of the numerical solution. The influence of wave and structural design parameters such as the number of ripple wavelengths of the wavy plate, relative plate length, structural porosities and relative submergence depth on hydrodynamics properties such as reflection, transmission, horizontal wave load and vertical wave coefficients are discussed. The study results of composite wavy porous plate indicate improved hydrodynamic performance as compared to the horizontal porous plate and wavy porous plate. This study is significant for practical applications in coastal engineering environments.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49194290","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Employing traditional Galerkin method, a coupled-mode flutter is predicted in the supercritical region of simply-supported pipes which constitutes a paradox since the internal flow effect is conservative and there is no energy to sustain the oscillation. Although there is a consensus that the flutter does not exist, the intrinsic mechanism remains to be clarified. This study has found that the internal flow induced Coriolis force term cannot be decoupled in traditional Galerkin method which leads to the dissatisfaction of the convergence conditions required in weighted residual approach (WRA). Moreover, the disparities in the predicted complex frequencies have been witnessed at different base function numbers when the internal flow velocity is sufficiently large. A modified Galerkin method adopting a new set of weighting functions is proposed based on WRA, and the Coriolis force term disappears by use of the orthogonality relations (it is stated that the Coriolis force is not directly omitted). Thus, a convergent solution for the set of residual functions which are identically equal to zeros can be guaranteed. Employing the modified method, the convergence in simulations is confirmed and the flutter phenomenon does not occur. This study can be a workbench for the study on the unsolved or partly solved issues in simulations of fluid-conveying pipes. Moreover, it has demonstrated that the predictions in traditional Galerkin method overestimate the natural frequencies, and it becomes more profound in higher-order natural modes at larger internal flow velocities which are of practice significance for dynamic analysis of flexible pipeline systems.
{"title":"An Explanation for the Flutter Paradox in the Supercritical Region of a Simply-Supported Fluid-Conveying Pipe","authors":"Ding Ming, Meng Shuai, Liu Zhen, Zhang Junhan","doi":"10.1115/1.4062718","DOIUrl":"https://doi.org/10.1115/1.4062718","url":null,"abstract":"\u0000 Employing traditional Galerkin method, a coupled-mode flutter is predicted in the supercritical region of simply-supported pipes which constitutes a paradox since the internal flow effect is conservative and there is no energy to sustain the oscillation. Although there is a consensus that the flutter does not exist, the intrinsic mechanism remains to be clarified. This study has found that the internal flow induced Coriolis force term cannot be decoupled in traditional Galerkin method which leads to the dissatisfaction of the convergence conditions required in weighted residual approach (WRA). Moreover, the disparities in the predicted complex frequencies have been witnessed at different base function numbers when the internal flow velocity is sufficiently large. A modified Galerkin method adopting a new set of weighting functions is proposed based on WRA, and the Coriolis force term disappears by use of the orthogonality relations (it is stated that the Coriolis force is not directly omitted). Thus, a convergent solution for the set of residual functions which are identically equal to zeros can be guaranteed. Employing the modified method, the convergence in simulations is confirmed and the flutter phenomenon does not occur. This study can be a workbench for the study on the unsolved or partly solved issues in simulations of fluid-conveying pipes. Moreover, it has demonstrated that the predictions in traditional Galerkin method overestimate the natural frequencies, and it becomes more profound in higher-order natural modes at larger internal flow velocities which are of practice significance for dynamic analysis of flexible pipeline systems.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44877632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Carlos Terencio Pires Bomfimsilva, Theodoro Antoun Netto
Abstract Free-standing hybrid risers (FSHR) are well established in deepwater field developments in the oil and gas industry. The major advantages foreseen for the FSHR are the possibility of safely anticipating production and requiring significantly reduced payloads at the floating production unit. This work addresses the feasibility of a novel proposed optimized concept, the free-standing integrated riser (FSIR), where the pipeline is integrated into the riser by means of a transition section, which is kept in place by a multiple line mooring system, developed to keep the functionality and integrity of the entire riser along its lifetime. The work provides the findings from numerical analysis simulated in orcaflex, a finite element simulation software dedicated to global analysis of risers, considering the design criteria provided in API 2RD Standard. As part of the FSIR evaluation, screening static analysis was performed to identify the most promising configurations for the multiple line mooring system, followed by a series of dynamic analyses to evaluate the behavior of the riser in extreme conditions. In addition, several investigations were performed to assess the functionality and the robustness of the system, including parametric studies to check for installation and dimensional tolerances, assessment of fatigue damage, and checking the impact of pipe size on the design. The results show that the proposed novel FSIR concept can provide a practical and economical solution for deepwater projects.
{"title":"A Novel Free-Standing Riser Concept for Deepwater Developments","authors":"Carlos Terencio Pires Bomfimsilva, Theodoro Antoun Netto","doi":"10.1115/1.4062688","DOIUrl":"https://doi.org/10.1115/1.4062688","url":null,"abstract":"Abstract Free-standing hybrid risers (FSHR) are well established in deepwater field developments in the oil and gas industry. The major advantages foreseen for the FSHR are the possibility of safely anticipating production and requiring significantly reduced payloads at the floating production unit. This work addresses the feasibility of a novel proposed optimized concept, the free-standing integrated riser (FSIR), where the pipeline is integrated into the riser by means of a transition section, which is kept in place by a multiple line mooring system, developed to keep the functionality and integrity of the entire riser along its lifetime. The work provides the findings from numerical analysis simulated in orcaflex, a finite element simulation software dedicated to global analysis of risers, considering the design criteria provided in API 2RD Standard. As part of the FSIR evaluation, screening static analysis was performed to identify the most promising configurations for the multiple line mooring system, followed by a series of dynamic analyses to evaluate the behavior of the riser in extreme conditions. In addition, several investigations were performed to assess the functionality and the robustness of the system, including parametric studies to check for installation and dimensional tolerances, assessment of fatigue damage, and checking the impact of pipe size on the design. The results show that the proposed novel FSIR concept can provide a practical and economical solution for deepwater projects.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136178680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mojtaba Kamarlouei, Thiago Hallak, Jose Gaspar, Miguel Calvario, Carlos Guedes Soares
Abstract This study presents the adaptation of a torus-shaped prime mover of a wave energy converter to an onshore or nearshore fixed platform by a hinged arm, with the objective of providing more favorable conditions for device survivability at extreme sea state. An optimization code is developed to obtain the best prime mover and arm geometries, as well as the power take-off parameters, with the objective to maximize the total absorbed power. In this paper, the power take-off system is modeled as a simplified damper and spring system, where the parameters are optimized for the power absorption of the wave energy converter in each sea state, whereas the optimization process is performed with a genetic algorithm. The results indicate that better survivability performance may be achieved with the torus-shaped prime mover in comparison to a conventional one without a moonpool, despite a relatively lower wave-absorbed power.
{"title":"Torus-Shaped Wave Energy Converter Attached to a Hinged Arm","authors":"Mojtaba Kamarlouei, Thiago Hallak, Jose Gaspar, Miguel Calvario, Carlos Guedes Soares","doi":"10.1115/1.4062624","DOIUrl":"https://doi.org/10.1115/1.4062624","url":null,"abstract":"Abstract This study presents the adaptation of a torus-shaped prime mover of a wave energy converter to an onshore or nearshore fixed platform by a hinged arm, with the objective of providing more favorable conditions for device survivability at extreme sea state. An optimization code is developed to obtain the best prime mover and arm geometries, as well as the power take-off parameters, with the objective to maximize the total absorbed power. In this paper, the power take-off system is modeled as a simplified damper and spring system, where the parameters are optimized for the power absorption of the wave energy converter in each sea state, whereas the optimization process is performed with a genetic algorithm. The results indicate that better survivability performance may be achieved with the torus-shaped prime mover in comparison to a conventional one without a moonpool, despite a relatively lower wave-absorbed power.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136066135","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hydrodynamic forces on small diameter subsea pipelines and cables placed near seabed are important for their on-bottom stability design. In offshore environments, these pipelines are usually subjected to extreme wave conditions. The present study investigates hydrodynamic forces acting on a pipeline near a flat seabed subjected to a wave-induced boundary layer flow. The Keulegan-Carpenter numbers (KC) of the wave-induced boundary layer flow are 20, 140 and 200, defined based on the pipeline diameter (D), the maximum velocity of the undisturbed near-bed orbital velocity (Uw) and the period of the incoming oscillatory flow (Tw). Reynolds number is 1 × 104 based on Uw and D. A seabed roughness ratio ks/D (ks is the Nikuradse equivalent sand roughness) of up to 0.1 and different gap ratios of G/D = 0.05~0.5 between the pipeline and the seabed are considered. Numerical simulations have been carried out based on two-dimensional (2D) Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations combined with the k-ω Shear Stress Transport (SST) turbulence model. A preliminary one-dimensional (1D) simulation is carried out to obtain a fully developed wave-induced boundary layer velocity profile, which is used as inlet flow for the 2D simulations. The numerical model is validated against the experimental data reported by Sumer et al. (1991) at KC = 10. Influences of KC, ks/D and G/D on the hydrodynamic forces and the surrounding flows are discussed in detail.
{"title":"Hydrodynamic Forces on a Near-bottom Pipeline Subject to Wave-induced Boundary Layer","authors":"G. Yin, M. Ong, N. Ye","doi":"10.1115/1.4062896","DOIUrl":"https://doi.org/10.1115/1.4062896","url":null,"abstract":"\u0000 Hydrodynamic forces on small diameter subsea pipelines and cables placed near seabed are important for their on-bottom stability design. In offshore environments, these pipelines are usually subjected to extreme wave conditions. The present study investigates hydrodynamic forces acting on a pipeline near a flat seabed subjected to a wave-induced boundary layer flow. The Keulegan-Carpenter numbers (KC) of the wave-induced boundary layer flow are 20, 140 and 200, defined based on the pipeline diameter (D), the maximum velocity of the undisturbed near-bed orbital velocity (Uw) and the period of the incoming oscillatory flow (Tw). Reynolds number is 1 × 104 based on Uw and D. A seabed roughness ratio ks/D (ks is the Nikuradse equivalent sand roughness) of up to 0.1 and different gap ratios of G/D = 0.05~0.5 between the pipeline and the seabed are considered. Numerical simulations have been carried out based on two-dimensional (2D) Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations combined with the k-ω Shear Stress Transport (SST) turbulence model. A preliminary one-dimensional (1D) simulation is carried out to obtain a fully developed wave-induced boundary layer velocity profile, which is used as inlet flow for the 2D simulations. The numerical model is validated against the experimental data reported by Sumer et al. (1991) at KC = 10. Influences of KC, ks/D and G/D on the hydrodynamic forces and the surrounding flows are discussed in detail.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41332640","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a solution verification and validation study for an overset mesh based numerical wave tank in OpenFOAM, which considers the coupling between a free-surface hydrodynamic flow model, a rigid body motion model and an overset mesh. The coupling between the rigid body motion solver and the free surface flow solver was achieved in a segregated manner. Free decay of roll motion of a barge was modelled using the numerical wave tank, and the damping coefficient was selected as the target quantity for solution verification. The least square based solution verification procedure was adopted, where one of the four types of error estimators was fit to the data in the least-square sense. Both structured and unstructured mesh were tested, and their effects on the convergence order, numerical uncertainty and error were carefully investigated. From the numerical tests, it is found that the numerical wave tank exhibits a very good convergence property for the floating body problems with structured mesh, i.e. nearly second order in space and first order in time. However, when switching the body-fitted mesh to unstructured mesh, the grid convergence is reduced to first order. Unstructured mesh does not significantly affect the convergence order in time domain, but results in a larger uncertainty due to data scattering.
{"title":"Analysis of convergence behavior for the overset mesh based numerical wave tank in OpenFOAM","authors":"Hao Chen, L. Qian, Deping Cao","doi":"10.1115/1.4063265","DOIUrl":"https://doi.org/10.1115/1.4063265","url":null,"abstract":"\u0000 This paper presents a solution verification and validation study for an overset mesh based numerical wave tank in OpenFOAM, which considers the coupling between a free-surface hydrodynamic flow model, a rigid body motion model and an overset mesh. The coupling between the rigid body motion solver and the free surface flow solver was achieved in a segregated manner. Free decay of roll motion of a barge was modelled using the numerical wave tank, and the damping coefficient was selected as the target quantity for solution verification. The least square based solution verification procedure was adopted, where one of the four types of error estimators was fit to the data in the least-square sense. Both structured and unstructured mesh were tested, and their effects on the convergence order, numerical uncertainty and error were carefully investigated. From the numerical tests, it is found that the numerical wave tank exhibits a very good convergence property for the floating body problems with structured mesh, i.e. nearly second order in space and first order in time. However, when switching the body-fitted mesh to unstructured mesh, the grid convergence is reduced to first order. Unstructured mesh does not significantly affect the convergence order in time domain, but results in a larger uncertainty due to data scattering.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48286118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The reliable design of offshore aquaculture structure (OAS) for fish farming in the open ocean is vital to the marine aquaculture industry in the future. However, the lack of easy-to-access numerical tools for the dynamic analysis of OAS challenges the development of marine aquaculture. This article presents a newly developed numerical library under an open-source, finite-element analysis code, Code_Aster, enabling the dynamic analysis of OAS. A numerical model of OAS is first developed using the present numerical library, and then validated against published experiments. The validation shows a good agreement in terms of structural motions and tensions in mooring lines. Subsequently, the dynamic responses of this model are analyzed under irregular waves and current conditions from field measurements on an offshore fish farm site. The results indicate that a negative mean pitch angle will occur when the current velocity is large.
{"title":"DYNAMIC SIMULATION OF AN OFFSHORE AQUACULTURE STRUCTURE SUBJECTED TO COMBINED WAVE AND CURRENT CONDITIONS","authors":"Hui Cheng, M. Ong, Lin Li","doi":"10.1115/1.4062623","DOIUrl":"https://doi.org/10.1115/1.4062623","url":null,"abstract":"\u0000 The reliable design of offshore aquaculture structure (OAS) for fish farming in the open ocean is vital to the marine aquaculture industry in the future. However, the lack of easy-to-access numerical tools for the dynamic analysis of OAS challenges the development of marine aquaculture. This article presents a newly developed numerical library under an open-source, finite-element analysis code, Code_Aster, enabling the dynamic analysis of OAS. A numerical model of OAS is first developed using the present numerical library, and then validated against published experiments. The validation shows a good agreement in terms of structural motions and tensions in mooring lines. Subsequently, the dynamic responses of this model are analyzed under irregular waves and current conditions from field measurements on an offshore fish farm site. The results indicate that a negative mean pitch angle will occur when the current velocity is large.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46830106","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rodrigo O Cruz, G. R. Duarte, B. Lima, B. P. Jacob
This paper presents an optimization tool for jacket structures to support Offshore Wind Turbines (OWTs). The tool incorporates several combinations of optimization algorithms and constraint handling techniques (CHTs): Genetic Algorithm; Differential Evolution (DE); Tournament Selection Method; Multiple Constraint Ranking (MCR); Adaptive Penalty Method, Helper-and-Equivalent Optimization. The objective function regards the minimization of the jacket weight; the design variables are the diameter and thickness of the tubular members. The constraints are related to natural frequencies and Ultimate Limit State criteria. The candidate solutions are evaluated by full nonlinear time-domain Finite Element coupled analyses. To assess the optimization algorithms and CHTs, a case study is presented for the standardized OWT/jacket structure from the Offshore Code Comparison Collaboration Continuation project. Firstly, a numerical model is built and validated, in terms of masses, natural frequencies and vibration modes; then, this model is employed to run the optimization tool for all combinations of optimization algorithms and CHTs. The results indicate that, while all methods lead to feasible optimal solutions that comply with the constraints and present considerable weight reductions, the best performer is the combination of the DE algorithm with the MCR constraint-handling technique.
{"title":"Optimization of steel jackets to support offshore wind turbines using evolutionary algorithms","authors":"Rodrigo O Cruz, G. R. Duarte, B. Lima, B. P. Jacob","doi":"10.1115/1.4062625","DOIUrl":"https://doi.org/10.1115/1.4062625","url":null,"abstract":"\u0000 This paper presents an optimization tool for jacket structures to support Offshore Wind Turbines (OWTs). The tool incorporates several combinations of optimization algorithms and constraint handling techniques (CHTs): Genetic Algorithm; Differential Evolution (DE); Tournament Selection Method; Multiple Constraint Ranking (MCR); Adaptive Penalty Method, Helper-and-Equivalent Optimization. The objective function regards the minimization of the jacket weight; the design variables are the diameter and thickness of the tubular members. The constraints are related to natural frequencies and Ultimate Limit State criteria. The candidate solutions are evaluated by full nonlinear time-domain Finite Element coupled analyses. To assess the optimization algorithms and CHTs, a case study is presented for the standardized OWT/jacket structure from the Offshore Code Comparison Collaboration Continuation project. Firstly, a numerical model is built and validated, in terms of masses, natural frequencies and vibration modes; then, this model is employed to run the optimization tool for all combinations of optimization algorithms and CHTs. The results indicate that, while all methods lead to feasible optimal solutions that comply with the constraints and present considerable weight reductions, the best performer is the combination of the DE algorithm with the MCR constraint-handling technique.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44804071","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wen-Huai Tsao, Ying-Chuan Chen, Christopher Kees, Lance Manuel
Abstract A porous-media-tuned liquid damper (PMTLD) can serve as an effective and economical dynamic vibration absorber. Placing porous media within a water tank can improve the capacity for energy dissipation and optimize the performance by varying its material properties. Two numerical models are adopted to simulate the sloshing problem in PMTLD and the dynamics of a floating platform in waves. Besides, the effectiveness of response mitigation can be verified numerically. The first potential-based approach employs a mixed-type boundary value problem (BVP) solver and a free-surface particle tracker. This approach not only simulates the inviscid water wave but also includes the nonlinear damping of the PMTLD via a quadratic Forchheimer term. Another equivalent mechanical model is used to reduce the degree-of-freedom of the PMTLD system. The Newmark method is incorporated to solve the rigid-body dynamics. The second viscous approach uses the finite element method (FEM) to spatially discretize the Navier–Stokes (NS) equations and handles the free surface via the volume of fluid (VOF) and the level set (LS) equations. The multiphase simulation is implemented by computational modeling toolkits, Proteus and Chrono, for the fluid and solid phases, respectively. The correlations between potential flow and two-phase NS models are presented. The PMTLD is designed by analogy with the tuned mass damper (TMD). Numerical results show that the PMTLD can effectively reduce the structure's dynamic response in terms of vibration amplitude around resonance. Such damping devices have great potential for offshore platforms and wind turbine design.
{"title":"Response Mitigation of Floating Platform by Porous-Media-Tuned Liquid Dampers","authors":"Wen-Huai Tsao, Ying-Chuan Chen, Christopher Kees, Lance Manuel","doi":"10.1115/1.4062292","DOIUrl":"https://doi.org/10.1115/1.4062292","url":null,"abstract":"Abstract A porous-media-tuned liquid damper (PMTLD) can serve as an effective and economical dynamic vibration absorber. Placing porous media within a water tank can improve the capacity for energy dissipation and optimize the performance by varying its material properties. Two numerical models are adopted to simulate the sloshing problem in PMTLD and the dynamics of a floating platform in waves. Besides, the effectiveness of response mitigation can be verified numerically. The first potential-based approach employs a mixed-type boundary value problem (BVP) solver and a free-surface particle tracker. This approach not only simulates the inviscid water wave but also includes the nonlinear damping of the PMTLD via a quadratic Forchheimer term. Another equivalent mechanical model is used to reduce the degree-of-freedom of the PMTLD system. The Newmark method is incorporated to solve the rigid-body dynamics. The second viscous approach uses the finite element method (FEM) to spatially discretize the Navier–Stokes (NS) equations and handles the free surface via the volume of fluid (VOF) and the level set (LS) equations. The multiphase simulation is implemented by computational modeling toolkits, Proteus and Chrono, for the fluid and solid phases, respectively. The correlations between potential flow and two-phase NS models are presented. The PMTLD is designed by analogy with the tuned mass damper (TMD). Numerical results show that the PMTLD can effectively reduce the structure's dynamic response in terms of vibration amplitude around resonance. Such damping devices have great potential for offshore platforms and wind turbine design.","PeriodicalId":50106,"journal":{"name":"Journal of Offshore Mechanics and Arctic Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135574146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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