The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
David Ingram - One of the best experts on this subject based on the ideXlab platform.
-
isolating incident and reflected wave spectra in the presence of current
Coastal Engineering Journal, 2018Co-Authors: Samuel Draycott, Jeffrey Steynor, Thomas Davey, David IngramAbstract:ABSTRACTIt is vital for a variety of coastal and Ocean Engineering problems to understand the reflection characteristics of structures and devices. Various methods have been developed for wave-only cases, yet none have been demonstrated for wave–current conditions present in both the laboratory and real sea environments. A simple method to isolate wave reflections in collinear current is presented in this article, utilizing an established frequency-domain least-squares approach with a modified dispersion relation. The method has been tested numerically, before being applied to experimental data obtained at the FloWave Ocean Energy Research Facility. Typical wave spectra are generated in currents ranging from −0.3 m/s to 0.3 m/s. Results obtained demonstrate the method effectiveness whilst verifying that the assumptions are valid. The development of this method should enable reflection analysis to be performed for wave–current conditions with improved accuracy and greater confidence.
-
isolating incident and reflected wave spectra in the presence of current
Coastal Engineering Journal, 2018Co-Authors: Samuel Draycott, Jeffrey Steynor, Thomas Davey, David IngramAbstract:It is vital for a variety of coastal and Ocean Engineering problems to understand the reflection characteristics of structures and devices. Various methods have been developed for wave-only cases, ...
Abbas Khayyer - One of the best experts on this subject based on the ideXlab platform.
-
enhancement of δ sph for Ocean Engineering applications through incorporation of a background mesh scheme
Applied Ocean Research, 2021Co-Authors: Abbas Khayyer, Yi You, Xing Zheng, Hitoshi GotohAbstract:Abstract The improved Smoothed Particle Hydrodynamics (SPH) method with numerical diffusive terms, which is referred to as δ-SPH, has been widely applied into the studies of Engineering problems, especially in the fields of Ocean and coastal Engineering. Nonetheless, there are still some drawbacks associated with δ-SPH model as in case of other particle methods. These drawbacks correspond to presence of unphysical pressure noise as well as imprecise satisfaction of dynamic free-surface boundary condition in numerical simulations. Through derivation and implementation of a so-called Background Mesh (BM) scheme and enforcing the spatial continuity of calculated source term of pressure equation (Equation of State; EOS), we present enhancements for δ-SPH in providing a more accurate pressure field as well as a more precise reproduction of free-surface. The enhancing effects of the newly proposed δ-SPH+BM are portrayed through several Ocean Engineering-related test cases including dam break and violent sloshing flows in both two and three dimensions. The incorporation of BM scheme is shown to result in enhanced calculation of pressure field as well as improved satisfaction of dynamic free-surface boundary condition as a consequence of enhanced density and pressure fields.
-
multi resolution isph sph for accurate and efficient simulation of hydroelastic fluid structure interactions in Ocean Engineering
Ocean Engineering, 2021Co-Authors: Abbas Khayyer, Hitoshi Gotoh, Yuma Shimizu, Shunsuke HattoriAbstract:Abstract A SPH (Smoothed Particle Hydrodynamics)-based multi-resolution fully Lagrangian meshfree hydroelastic FSI (Fluid-Structure Interaction) solver is developed for accurate and adaptive reproductions of Ocean Engineering problems. The presented hydroelastic FSI solver comprises of projection-based ISPH (Incompressible SPH) fluid model and SPH structure model, through consideration of continuity/Navier-Stokes equations for fluid phase as well as linear/angular momentum conservation equations for structure phase. The FSI solver includes a consistent fluid-structure coupling scheme along with a novel multi-resolution scheme incorporating a common influence length, a modified SPH density definition and a SPH-based formulated SPP (Space Potential Particle) scheme in order to achieve consistent particle-based discretizations, precise satisfaction of fluid-structure interface boundary conditions and accurate volume conservation at the interface. The present ISPH fluid model corresponds to a refined version of ISPH incorporating several previously developed refined schemes, and hence the proposed FSI solver is referred to as “Enhanced Multi-resolution ISPH-SPH”. Validations are performed qualitatively/quantitatively through reproductions of classical as well as Ocean Engineering benchmark tests. Comparisons are also made with an MPS-based FSI solver as well as an Explicit ISPH-based one. A preliminary extension of the proposed solver to three-dimensions is also presented.
-
multi resolution mps for incompressible fluid elastic structure interactions in Ocean Engineering
Applied Ocean Research, 2019Co-Authors: Abbas Khayyer, Yuma Shimizu, Naoki Tsuruta, Hitoshi GotohAbstract:Abstract The paper presents a multi-resolution MPS (Moving Particle Semi-implicit)-based FSI (Fluid-Structure Interaction) solver for efficient and accurate simulations of incompressible fluid flows interacting with elastic structures. The fluid model is founded on the projection-based MPS solution of continuity and Navier-Stokes equations. The structure model is set based on MPS-based discretization of linear and angular momenta corresponding to an isotropic elastic solid. Fluid-structure coupling is conducted in a mathematically-physically consistent manner along with implementation of a multi-resolution scheme comprising of common radius of influence, revised weight function, revised number density and potential number density concepts to enhance i) consistency of particle-based discretizations, ii) imposition of boundary conditions and iii) volume conservation at fluid-structure interface. A set of previously developed enhanced schemes are also adopted for the fluid model. The robustness and efficiency of proposed Enhanced Multi-resolution MPS-MPS FSI solver are investigated through a set of Ocean Engineering-related benchmark tests. To the best knowledge of authors, this study presents the first multi-resolution particle method for FSI corresponding to incompressible fluid and elastic structures.
-
On the state-of-the-art of particle methods for coastal and Ocean Engineering
Coastal Engineering Journal, 2018Co-Authors: Hitoshi Gotoh, Abbas KhayyerAbstract:ABSTRACTThe article aims at providing an up-to-date review on several latest advancements related to particle methods with applications in coastal and Ocean Engineering. The latest advancements corresponding to accuracy, stability, conservation properties, multiphase multi-physics multi-scale simulations, fluid-structure interactions, exclusive coastal/Ocean Engineering applications and computational efficiency are reviewed. The future perspectives for further enhancement of applicability and reliability of particle methods for coastal/Ocean Engineering applications are also highlighted.
-
Current achievements and future perspectives for projection-based particle methods with applications in Ocean Engineering
Journal of Ocean Engineering and Marine Energy, 2016Co-Authors: Hitoshi Gotoh, Abbas KhayyerAbstract:The paper aims at providing a comprehensive and up-to-date review on the latest achievements made in the context of particle methods, in particular the projection-based ones, with applications in Ocean Engineering. The latest achievements corresponding to stability, accuracy, energy conservation and boundary condition enhancements as well as advancements related to improved simulations of multiphase flows, surface tension and fluid–structure interactions are reviewed. The future perspectives for enhancement of applicability and reliability of these methods for Ocean Engineering applications are also highlighted.
Hitoshi Gotoh - One of the best experts on this subject based on the ideXlab platform.
-
enhancement of δ sph for Ocean Engineering applications through incorporation of a background mesh scheme
Applied Ocean Research, 2021Co-Authors: Abbas Khayyer, Yi You, Xing Zheng, Hitoshi GotohAbstract:Abstract The improved Smoothed Particle Hydrodynamics (SPH) method with numerical diffusive terms, which is referred to as δ-SPH, has been widely applied into the studies of Engineering problems, especially in the fields of Ocean and coastal Engineering. Nonetheless, there are still some drawbacks associated with δ-SPH model as in case of other particle methods. These drawbacks correspond to presence of unphysical pressure noise as well as imprecise satisfaction of dynamic free-surface boundary condition in numerical simulations. Through derivation and implementation of a so-called Background Mesh (BM) scheme and enforcing the spatial continuity of calculated source term of pressure equation (Equation of State; EOS), we present enhancements for δ-SPH in providing a more accurate pressure field as well as a more precise reproduction of free-surface. The enhancing effects of the newly proposed δ-SPH+BM are portrayed through several Ocean Engineering-related test cases including dam break and violent sloshing flows in both two and three dimensions. The incorporation of BM scheme is shown to result in enhanced calculation of pressure field as well as improved satisfaction of dynamic free-surface boundary condition as a consequence of enhanced density and pressure fields.
-
multi resolution isph sph for accurate and efficient simulation of hydroelastic fluid structure interactions in Ocean Engineering
Ocean Engineering, 2021Co-Authors: Abbas Khayyer, Hitoshi Gotoh, Yuma Shimizu, Shunsuke HattoriAbstract:Abstract A SPH (Smoothed Particle Hydrodynamics)-based multi-resolution fully Lagrangian meshfree hydroelastic FSI (Fluid-Structure Interaction) solver is developed for accurate and adaptive reproductions of Ocean Engineering problems. The presented hydroelastic FSI solver comprises of projection-based ISPH (Incompressible SPH) fluid model and SPH structure model, through consideration of continuity/Navier-Stokes equations for fluid phase as well as linear/angular momentum conservation equations for structure phase. The FSI solver includes a consistent fluid-structure coupling scheme along with a novel multi-resolution scheme incorporating a common influence length, a modified SPH density definition and a SPH-based formulated SPP (Space Potential Particle) scheme in order to achieve consistent particle-based discretizations, precise satisfaction of fluid-structure interface boundary conditions and accurate volume conservation at the interface. The present ISPH fluid model corresponds to a refined version of ISPH incorporating several previously developed refined schemes, and hence the proposed FSI solver is referred to as “Enhanced Multi-resolution ISPH-SPH”. Validations are performed qualitatively/quantitatively through reproductions of classical as well as Ocean Engineering benchmark tests. Comparisons are also made with an MPS-based FSI solver as well as an Explicit ISPH-based one. A preliminary extension of the proposed solver to three-dimensions is also presented.
-
multi resolution mps for incompressible fluid elastic structure interactions in Ocean Engineering
Applied Ocean Research, 2019Co-Authors: Abbas Khayyer, Yuma Shimizu, Naoki Tsuruta, Hitoshi GotohAbstract:Abstract The paper presents a multi-resolution MPS (Moving Particle Semi-implicit)-based FSI (Fluid-Structure Interaction) solver for efficient and accurate simulations of incompressible fluid flows interacting with elastic structures. The fluid model is founded on the projection-based MPS solution of continuity and Navier-Stokes equations. The structure model is set based on MPS-based discretization of linear and angular momenta corresponding to an isotropic elastic solid. Fluid-structure coupling is conducted in a mathematically-physically consistent manner along with implementation of a multi-resolution scheme comprising of common radius of influence, revised weight function, revised number density and potential number density concepts to enhance i) consistency of particle-based discretizations, ii) imposition of boundary conditions and iii) volume conservation at fluid-structure interface. A set of previously developed enhanced schemes are also adopted for the fluid model. The robustness and efficiency of proposed Enhanced Multi-resolution MPS-MPS FSI solver are investigated through a set of Ocean Engineering-related benchmark tests. To the best knowledge of authors, this study presents the first multi-resolution particle method for FSI corresponding to incompressible fluid and elastic structures.
-
On the state-of-the-art of particle methods for coastal and Ocean Engineering
Coastal Engineering Journal, 2018Co-Authors: Hitoshi Gotoh, Abbas KhayyerAbstract:ABSTRACTThe article aims at providing an up-to-date review on several latest advancements related to particle methods with applications in coastal and Ocean Engineering. The latest advancements corresponding to accuracy, stability, conservation properties, multiphase multi-physics multi-scale simulations, fluid-structure interactions, exclusive coastal/Ocean Engineering applications and computational efficiency are reviewed. The future perspectives for further enhancement of applicability and reliability of particle methods for coastal/Ocean Engineering applications are also highlighted.
-
Current achievements and future perspectives for projection-based particle methods with applications in Ocean Engineering
Journal of Ocean Engineering and Marine Energy, 2016Co-Authors: Hitoshi Gotoh, Abbas KhayyerAbstract:The paper aims at providing a comprehensive and up-to-date review on the latest achievements made in the context of particle methods, in particular the projection-based ones, with applications in Ocean Engineering. The latest achievements corresponding to stability, accuracy, energy conservation and boundary condition enhancements as well as advancements related to improved simulations of multiphase flows, surface tension and fluid–structure interactions are reviewed. The future perspectives for enhancement of applicability and reliability of these methods for Ocean Engineering applications are also highlighted.
Samuel Draycott - One of the best experts on this subject based on the ideXlab platform.
-
isolating incident and reflected wave spectra in the presence of current
Coastal Engineering Journal, 2018Co-Authors: Samuel Draycott, Jeffrey Steynor, Thomas Davey, David IngramAbstract:ABSTRACTIt is vital for a variety of coastal and Ocean Engineering problems to understand the reflection characteristics of structures and devices. Various methods have been developed for wave-only cases, yet none have been demonstrated for wave–current conditions present in both the laboratory and real sea environments. A simple method to isolate wave reflections in collinear current is presented in this article, utilizing an established frequency-domain least-squares approach with a modified dispersion relation. The method has been tested numerically, before being applied to experimental data obtained at the FloWave Ocean Energy Research Facility. Typical wave spectra are generated in currents ranging from −0.3 m/s to 0.3 m/s. Results obtained demonstrate the method effectiveness whilst verifying that the assumptions are valid. The development of this method should enable reflection analysis to be performed for wave–current conditions with improved accuracy and greater confidence.
-
isolating incident and reflected wave spectra in the presence of current
Coastal Engineering Journal, 2018Co-Authors: Samuel Draycott, Jeffrey Steynor, Thomas Davey, David IngramAbstract:It is vital for a variety of coastal and Ocean Engineering problems to understand the reflection characteristics of structures and devices. Various methods have been developed for wave-only cases, ...
Shuwang Yan - One of the best experts on this subject based on the ideXlab platform.
-
reserch on the large diameter and supper long pile running under self weight in the Ocean Engineering
Journal of Coastal Research, 2015Co-Authors: Shuwang Yan, Zhaolin Jia, Wenbin LiuAbstract:ABSTRACT Yan, S.; Jia, Z.; Liu, W., and Zhang, X., 2015. Case history: Large diameter and supper long pile-running under self-weight in Liwan Oil Field. The pile-running frequently occurs because of the great weights of both the pile and the hammer. Thepile-running mechanism is super long and large-diameter piles are commonly used for constructing Ocean platform foundations. Pile-running discussed in the current study through case analyses. A predicting procedure is developed based on the limit equilibrium of pile weight and soil resistance. Reduction factors for soil strength used to calculate the skin friction are also suggested in the current study. The Berezantsev approach is recommended for calculating the end bearing resistance to the running pile, which can improve the precision of the estimation compared with that of commonly used methods. The suggested method is used to predict the pile-running case in a practical project, and the calculated results are consistent with the driving records.
-
pit bearing capacity effect on status of soil plug during pile driving in Ocean Engineering
China Ocean Engineering, 2011Co-Authors: Shuwang Yan, Run Liu, Qunhua Zhou, Wei DongAbstract:Foundation piles of the offshore oil platforms in the Bohai Bay are usually longer than 100 m with a diameter larger than 2 m. Driving such long and large-sized piles into the ground is a difficult task. It needs a comprehensive consider ation of the pile dimensions, soil properties and the hammer energy. Thoughtful drivability analysis has to be performed in the design stage. It has been shown that judging whether the soil column inside the pile is fully plugged, which makes the pile behave as close-ended, strongly influences the accuracy of drivability analysis. Engineering practice repeatedly indicates that the current methods widely used for soil plug judgment often give incorrect results, leading the designers to make a wrong decision. It has been found that this problem is caused by the ignorance of the bearing capacity provided by the soil surrounding the pile. Based on the Terzaghi’s bearing capacity calculation method for deep foundation, a new approach for judging soil plug status is put forward, in which the surcharge effect has been considered and the dynamic effect coefficient is included. This approach has been applied to some practical Engineering projects successfully, which may give more reasonable results than the currently used method does.
-
pit bearing capacity effect to status of soil plug during pile driving in Ocean Engineering
Advanced Materials Research, 2011Co-Authors: Ping Zhu, Shuwang YanAbstract:Foundation piles of the offshore oil platforms in Bohai Bay are usually longer than 100m with a diameter larger than 2m. Thus, thoughtful drivability analysis has to be performed in the design stage because of the high cost and time limitation. It has been shown that to judge if the soil column inside the pile is fully plugged, which will make the pile behave as close-ended, will strongly influence the accuracy of drivability analysis. Engineering practice repeatedly indicates that the currently widely used methods for soil plug judgment often give incorrect results, leading the designers to make a wrong decision. It has been found that this problem is caused by the ignorance of the bearing capacity provided by the soil surrounding the pile. Based on the Terzaghi’s bearing capacity calculation method for deep foundation, a new approach for judging soil plug status is put forward, in which the surcharge effect has been considered and the dynamic effect coefficient is included. This approach has been applied to some practical Engineering projects successfully, which may give more reasonable results than the currently used method.
-
soil plug effect prediction and pile driveability analysis for large diameter steel piles in Ocean Engineering
China Ocean Engineering, 2009Co-Authors: Run Liu, Shuwang YanAbstract:Long steel piles with large diameters have been more widely used in the field of Ocean Engineering. Owing to the pile with a large diameter, soil plug development during pile driving has great influences on pile driveability and bearing capacity. The response of soil plug developed inside the open-ended pipe pile during the dynamic condition of pile-driving is different from the response under the static condition of loading during service. This paper addresses the former aspect. A numerical procedure for soil plug effect prediction and pile driveability analysis is proposed and described. By taking into consideration of the pile dimension effect on side and tip resistance, this approach introduces a dimensional coefficient to the conventional static equilibrium equations for the plug differential unit and proposes an improved static equity method for the plug effect prediction. At the same time, this approach introduces a simplified model by use of one-dimensional stress wave equation to simulate the interaction between soil plug and pile inner wall. The proposed approach has been applied in practical Engineering analyses. Results show that the calculated plug effect and pile driveability based on the proposed approach agree well with the observed data.
