ORCID Profile
0000-0002-6344-638X
Current Organisation
Hong Kong University of Science and Technology
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Civil Engineering | Geotechnical Engineering |
Publisher: CRC Press
Date: 04-09-2014
DOI: 10.1201/B17435-241
Publisher: Springer Science and Business Media LLC
Date: 20-04-2014
Publisher: Thomas Telford Ltd.
Date: 05-2021
Abstract: Both the solid and fluid phases in a debris flow vitally influence the impact dynamics against a rigid barrier. However, previous numerical and analytical models commonly adopt an equivalent fluid approach, which does not explicitly consider solid–fluid interaction when impacting a barrier. This study investigates the role of solid–fluid interaction on the impact mechanism and load exerted on a rigid barrier. A coupled computational fluid dynamics and discrete-element method (CFD–DEM) is used to study the effect of solid–fluid interaction on impact by varying the solid fraction from 0 to 0·5. The mesoscopic insight from CFD–DEM modelling reveals that the particle–fluid interaction plays two roles in increasing the kinematic energy of particles: (a) imposing driving force to the particles (b) reducing inter-particle contact forces and therefore energy dissipation from shearing among grains by applying buoyancy to the particles. Consequently, the run-up height and impact pressure of the water–particle mixture flows at the barrier are higher than those of dry granular flows with the same Froude number (Fr). While impacting the rigid barrier, most of the energy of water–particle mixtures (exhibiting a run-up mechanism) is dissipated as the fluid phase segregates from the mixture and rolls back towards subsequent flow. This differs from the conventional impact mechanism observed for dry granular flows, where the energy is mainly dissipated by way of shearing between layers of sand piling up behind a barrier.
Publisher: Elsevier BV
Date: 10-2018
Publisher: Elsevier BV
Date: 2010
Publisher: Springer Science and Business Media LLC
Date: 20-09-2013
Publisher: Wiley
Date: 19-06-2018
DOI: 10.1002/NAG.2806
Publisher: Elsevier BV
Date: 10-2005
Publisher: Elsevier BV
Date: 10-2019
Publisher: Wiley
Date: 14-07-2015
DOI: 10.1002/NAG.2406
Publisher: Elsevier BV
Date: 05-2013
Publisher: Elsevier BV
Date: 05-2019
Publisher: AIP
Date: 2013
DOI: 10.1063/1.4812025
Publisher: EDP Sciences
Date: 2017
Publisher: Springer International Publishing
Date: 2017
Publisher: Wiley
Date: 28-01-2021
DOI: 10.1002/NAG.3189
Publisher: American Society of Civil Engineers (ASCE)
Date: 08-2019
Publisher: Elsevier BV
Date: 2009
Publisher: Elsevier BV
Date: 10-2017
Publisher: Elsevier BV
Date: 08-2021
Publisher: Elsevier BV
Date: 02-2023
Publisher: Elsevier BV
Date: 08-2003
Publisher: Elsevier BV
Date: 12-2016
Publisher: Wiley
Date: 03-2019
DOI: 10.1002/NAG.2921
Publisher: Elsevier BV
Date: 06-2023
Publisher: Wiley
Date: 03-05-2021
DOI: 10.1002/NAG.3212
Abstract: Footing foundations are sometimes built on sloping grounds of natural sand which is highly anisotropic. The anisotropic mechanical behaviour of sand can significantly influence the bearing capacity of a foundation and the failure mechanism of its supporting slope. Neglecting sand anisotropy may lead to overestimated bearing capacity and under‐design of foundations. A numerical investigation on the response of a supporting slope under a strip footing is presented, placing a special focus on the effect of sand anisotropy. A critical state sand model accounting for fabric evolution is used. The nonlocal method has been used to regularize the mesh‐dependency of the numerical solutions. Predictions of the anisotropic model on the bearing capacity of strip footings on slopes are validated by centrifuge test data on Toyoura sand. Compared to the centrifuge test data , an isotropic model may overpredict the bearing capacity of the footing by up to 100% when the model parameters are determined based on test data on a horizontal bedding plane case. When the isotropic model parameters are determined based on test data where the bedding plane is vertical, the predictions of bearing capacity can be improved for some cases but the settlement at failure may be significantly overestimated. The soil body tends to move along the bedding plane upon the footing loading due to the non‐coaxial strain increment caused by fabric anisotropy. The slip surface appears to be deeper with lower bearing capacity when the preferred soil movement direction caused by bedding plane is towards the slope.
Publisher: Thomas Telford Ltd.
Date: 08-2021
Abstract: A new analytical model is proposed to estimate the peak impact pressure of debris flow exerted on a rigid barrier. The new model consists of two terms, p = α 1 ρ 0 gh 0 + 0·5ρ 0 u 0 2 , accounting for static and dynamic impacting effects, respectively. The static coefficient α 1 is determined according to equations governing the mass and momentum conservation and energy conservation, and the dynamic coefficient 0·5 is adopted on the basis of the Bernoulli equation. The new analytical model is validated for a wide range of Froude number (Fr) with data collected from past studies on small-scale experiments and field observations and numerical simulations of debris flow as a particle–fluid mixture performed by coupled computational fluid dynamics–discrete-element method (CFD–DEM, for wide-range coverage of Fr). Based on equivalence with the new model, the empirical coefficients involved in conventional pure hydrostatic (k) and pure hydrodynamic (α) impact models are found positively and negatively correlated to Fr, respectively. A unique relationship between k and α is further derived: (cos θ/k) + (1/α) = 1, where θ denotes slope angle. The underlying physics of this relationship is interpreted. According to the proposed model, a design chart in terms of Fr is further recommended for practical design of debris-resisting barriers. The new analytical model offers a possible improvement on robust and reliable estimation of debris flow impact on a rigid barrier.
Publisher: Wiley
Date: 06-06-2002
DOI: 10.1002/NAG.225
Publisher: Springer International Publishing
Date: 2017
Publisher: American Society of Civil Engineers (ASCE)
Date: 08-2015
Publisher: Elsevier BV
Date: 04-2021
Publisher: Wiley
Date: 07-10-2020
DOI: 10.1002/NME.6549
Publisher: Springer Berlin Heidelberg
Date: 2013
Publisher: Wiley
Date: 22-12-2020
DOI: 10.1002/NAG.3175
Publisher: American Physical Society (APS)
Date: 22-01-2020
Publisher: Thomas Telford Ltd.
Date: 08-2015
Abstract: This paper presents a multiscale investigation on the interplay among inherent anisotropy, fabric evolution and strain localisation in granular soils, based on a hierarchical multiscale framework with rigorous coupling of the finite-element method (FEM) and discrete-element method (DEM). DEM assemblies with elongated particles are generated to simulate inherent anisotropy and are embedded to the Gauss points of the FEM mesh to derive the required constitutive relation. Specimens prepared with different bedding plane angles are subjected to biaxial shear under either smooth or rough loading platens. Key factors and physical mechanisms contributing towards the occurrence and development of strain localisation are examined. The competing evolutions of two sources of anisotropy, one related to particle orientations and the other related to contact normals, are found to underpin the development of the shear band. A single band pattern is observed under smooth boundary conditions, and its orientation relative to the bedding plane depends critically on the relative dominance between the two anisotropies. Under rough boundary conditions, the non-coaxial material response and the boundary constraint jointly lead to cross-shaped double shear bands. The multiscale simulations indicate that the DEM assemblies inside the shear band(s) undergo extensive shearing, fabric evolution and particle rotation, and may reach the critical state, while those located outside the shear band(s) experience mild loading followed by unloading. The particle-orientation-based fabric anisotropy needs significantly larger shear and dilation for mobilisation than the contact-normal based one. The asynchrony in evolution of the two fabric anisotropies can cause non-coaxial responses for initially coaxial packings, which directly triggers strain localisation.
Publisher: Springer Science and Business Media LLC
Date: 07-07-2020
Publisher: American Society of Civil Engineers (ASCE)
Date: 09-2021
Publisher: Springer Science and Business Media LLC
Date: 08-09-2020
Publisher: The Japanese Geotechnical Society
Date: 2016
Publisher: American Geophysical Union (AGU)
Date: 11-2022
DOI: 10.1029/2022JF006870
Abstract: Geophysical mass flows impacting flexible barriers can create complex flow patterns and multiway solid‐fluid‐structure interactions, wherein estimates of impact loads rely predominantly on analytical or simplified solutions. However, an examination of the fundamental relations, applicability, and underlying mechanisms of these solutions has been so far elusive. Here, using a coupled continuum‐discrete method, we systematically examine the physical laws of multiphase, multiway interactions between geophysical flows of variable natures, and a permeable flexible ring net barrier system. This model well captures the essential physics observed in experiments and field investigations. Our results reveal for the first time that unified bi‐linear laws underpin widely used analytical and simplified solutions, with inflection points caused by the transitions from trapezoid‐shaped to triangle‐shaped dead zones. Specifically, the peak impact load increases bi‐linearly with increasing Froude number, peak cable force, or maximum barrier deformation. Flow materials (wet vs. dry) and impact dynamics (slow vs. fast) jointly drive the patterns of identified bi‐linear correlations. These findings offer a physics‐based, significant improvement over existing solutions to impact problems for geophysical flows.
Publisher: American Society of Civil Engineers (ASCE)
Date: 2013
Publisher: Elsevier BV
Date: 03-2018
Publisher: Elsevier BV
Date: 12-2021
Publisher: Springer Science and Business Media LLC
Date: 02-2014
Publisher: Wiley
Date: 23-03-2021
DOI: 10.1002/NAG.3207
Abstract: In this paper, a new formulation of material point method (MPM) to model coupled soil deformation and pore fluid flow problems is presented within the framework of the theory of porous media. The saturated porous medium is assumed to be consisting of incompressible pore fluid and deformable soil skeleton made up of incompressible solid grains. The main difference of the proposed MPM algorithm is the implicit treatment of pore‐water pressure which satisfies its incompressibility internal constraint. The resulting solid‐fluid coupled equations are solved by using a splitting algorithm based on the Chorin's projection method. The splitting algorithm helps to mitigate numerical instabilities at the incompressibility limit when equal‐order interpolation functions are used. The key strengths of the proposed semi‐implicit coupled MPM formulation is its capability to reduce pressure oscillations as well as to increase the time step size, which is independent of the fluid incremental strain level and the soil permeability. The proposed semi‐implicit MPM is validated by comparing the numerical results with the analytical solutions of several numerical tests, including 1D and 2D plane‐strain consolidation problems. To demonstrate the capability of the proposed method in simulating practical engineering problems involving large deformations, a hydraulic process leading to slope failure is studied, and the numerical result is validated by the monitored data.
Publisher: Thomas Telford Ltd.
Date: 06-01-2021
Publisher: Thomas Telford Ltd.
Date: 08-11-2022
Abstract: Grain crushing underpins key mechanical behaviours of granular materials. A variety of factors, including grading, particle shapes and loading conditions, have been recognised to affect the crushability of grains and the overall behaviour of a granular material. Among them, the role of intermediate principal stress in a general stress condition on the shear behaviour of crushable granular sand remains less understood, owing to the scarcity of experimental data and analytical tools available. In this paper, a multi-scale computational approach is employed to investigate the shear behaviour of crushable granular sand under general stress conditions with varying intermediate principal stresses and confining pressures. The computational approach features multi-scale coupling between non-smooth contact dynamics and peridynamics, and offers a rigorous way to consider the intertwined evolution of particle size and shape during the process of grain crushing. The numerical study helps to quantify comprehensively and analyse the grain crushing-induced changes of macro- and micro-scale material behaviours including strength, deformability, particle size and shape evolution, particle-scale forces and contact conditions, and the development of anisotropy. The competition between a void-filling mechanism due to grain size change and enhanced friction and interlocking due to grain shape change in dictating the deformation of crushable sand is further discussed. The findings offer insights into the complex behaviours of crushable granular materials under general stress conditions and facilitate future development of physics-based constitutive theories on crushable sand.
Publisher: Elsevier BV
Date: 2024
Publisher: Elsevier BV
Date: 06-2008
Publisher: Springer International Publishing
Date: 30-12-2014
Publisher: Elsevier BV
Date: 06-2016
Publisher: Springer Science and Business Media LLC
Date: 14-06-2012
Publisher: Springer Science and Business Media LLC
Date: 23-09-2021
DOI: 10.1007/S10346-020-01531-2
Abstract: Slit dam is an open-check barrier structure widely used in mountainous regions to resist the destructive impacts of granular flows. To examine the dynamics of granular flow impact on slit dams, a numerical study by discrete element method (DEM) is presented in this article. The study considers dry granular materials flowing down a flume channel and interacts with slit dams installed at the lower section of the flume. The particle shape is explicitly considered by particle clumps of various aspect ratios. The slit dams are modeled as rigid and smooth rectangular prisms uniformly spaced at in the flume. Four key stages of granular flow impact on the slit dams have been identified, namely, the frontal impact, run up, pile up, and static deposition stages. In the impact process, the kinetic energy of the granular flow is dissipated primarily by interparticle friction and d ing. The trapping efficiency of the slit dams decreases exponentially with the relative post spacing, while it increases with the particle clump aspect ratio. The numerical results can provide new insights into the optimization of relative post spacing for slit dam design.
Publisher: Elsevier BV
Date: 02-2023
Publisher: Institution of Engineering and Technology
Date: 2012
DOI: 10.1049/CP.2012.2384
Publisher: Springer International Publishing
Date: 2021
Publisher: Springer Science and Business Media LLC
Date: 04-07-2016
Publisher: Springer International Publishing
Date: 2018
Publisher: Elsevier BV
Date: 09-2023
Publisher: Elsevier BV
Date: 05-2011
Publisher: The Japanese Geotechnical Society
Date: 2015
DOI: 10.3208/JGSSP.CPN-05
Publisher: Wiley
Date: 28-02-2021
Publisher: Elsevier BV
Date: 09-2006
Publisher: Springer Science and Business Media LLC
Date: 13-04-2020
Publisher: Elsevier BV
Date: 02-2021
Publisher: Elsevier BV
Date: 02-2017
Publisher: CRC Press
Date: 26-08-2014
DOI: 10.1201/B17395-41
Publisher: The Japanese Geotechnical Society
Date: 2016
Publisher: Springer International Publishing
Date: 2018
Publisher: Wiley
Date: 07-10-2020
DOI: 10.1002/NAG.3151
Publisher: Wiley
Date: 17-04-2018
DOI: 10.1002/NME.5807
Publisher: American Society of Civil Engineers (ASCE)
Date: 2016
Publisher: Springer Science and Business Media LLC
Date: 24-02-2021
Publisher: Elsevier BV
Date: 07-2018
Publisher: Elsevier BV
Date: 05-2019
Publisher: Elsevier BV
Date: 09-2022
Publisher: Thomas Telford Ltd.
Date: 09-01-2023
Abstract: Quantitative understanding of the load–deflection mechanisms of a flexible barrier in intercepting debris flows is critical for barrier design, but remains practically challenging due to the difficulties involved in capturing multi-phase, multi-way interactions. This study employs a physics-based coupled computational fluid dynamics and discrete-element method (CFD–DEM) to simulate a flexible ring-net barrier as a permeable, deformable multi-component system by DEM and model a debris flow as a mixture of discrete particles and a continuous slurry by DEM and CFD, respectively. The CFD–DEM coupling framework offers a unified treatment of in-flow solid–fluid interaction, flow–barrier interaction and interactions among barrier components. Numerical predictions of key flow–barrier interactions and cable forces show reasonable consistency with large-scale experiments. Systematic simulations with varying flow–barrier height ratios ε and flow dynamics are performed to examine the evolving mechanisms of load sharing and transmission and quantify the ε-dependent load–deflection modes. The ratio ε is found to bear a strong, positive correlation with the key barrier response in three typical modes. The post-peak barrier deformations experience shrinkages with ε ≤ 0·6 and expansions when ε 0·6. This study helps to improve understanding of the load–deflection mechanisms for practical design of flexible barriers in mitigating debris flows.
Publisher: Canadian Science Publishing
Date: 02-2011
DOI: 10.1139/T10-060
Abstract: Soil-water characteristic curves (SWCCs) are routinely used for the estimation of unsaturated soil property functions (e.g., permeability functions, water storage functions, shear strength functions, and thermal property functions). This paper examines the possibility of using the SWCC for the estimation of in situ soil suction. The paper focuses on the limitations of estimating soil suctions from the SWCC and also suggests a context under which soil suction estimations should be used. The potential range of estimated suction values is known to be large because of hysteresis between drying and wetting SWCCs. For this, and other reasons, the estimation of in situ suctions from the SWCC has been discouraged. However, a framework is suggested in this paper for estimating the median value for in situ soil suction along with a likely range of soil suction values (i.e., maximum and minimum values). The percentage error in the estimation of soil suction from the SWCC is shown to be lowest for sand soils and highest for clay soils.
Publisher: American Society of Civil Engineers (ASCE)
Date: 05-2017
Publisher: Elsevier BV
Date: 06-2022
Publisher: Elsevier BV
Date: 08-2021
Publisher: Springer Science and Business Media LLC
Date: 30-12-2013
Publisher: Elsevier BV
Date: 09-2021
Publisher: Wiley
Date: 19-07-2013
DOI: 10.1002/NAG.2211
Publisher: American Physical Society (APS)
Date: 25-04-2014
Publisher: Elsevier BV
Date: 2021
Publisher: Elsevier BV
Date: 05-2015
Publisher: Elsevier BV
Date: 07-2021
Publisher: Thomas Telford Ltd.
Date: 03-2016
Abstract: A novel hierarchical multiscale model has been applied to simulate the thick-walled hollow cylinder tests in dry sand and to investigate the corresponding shear failures. The combined finite-element method and discrete-element method (FEM/DEM) model employs the FEM as a vehicle to advance the solution for a macroscopic non-linear boundary value problem incrementally. It is, meanwhile, free of conventional macroscopic phenomenological constitutive law, which is replaced by discrete-element simulations conducted with representative volume elements (RVEs) associated with the Gauss quadrature points of the FEM mesh. Numerical simulations proposed by the authors indicate that this multiscale approach is capable of replicating the evolution of cavity pressure during cavity expansion – before and after the onset of strain localisation – in qualitative agreement with laboratory tests. In particular, the curvilinear shear bands observed from experiments have been reproduced numerically. The information provided by the mesoscale DEM and the macroscale FEM reveals a close linkage between significant particle rotations taking place inside the dilative shear bands and the highly anisotropic microstructural attributes of the associated RVEs.
Publisher: Elsevier BV
Date: 05-2013
Publisher: Springer Science and Business Media LLC
Date: 30-10-2013
Publisher: Elsevier BV
Date: 09-2014
Publisher: Elsevier BV
Date: 2013
Publisher: Springer International Publishing
Date: 2015
Publisher: Springer Science and Business Media LLC
Date: 09-12-2014
Publisher: Springer Berlin Heidelberg
Date: 2013
Publisher: Elsevier BV
Date: 02-2017
Publisher: The Japanese Geotechnical Society
Date: 2016
Publisher: Elsevier BV
Date: 08-2020
Publisher: Thomas Telford Ltd.
Date: 06-2013
Abstract: The concept of the critical state in granular soils needs to make proper reference to the fabric structure that develops at critical state. This study identifies a unique property associated with the fabric structure relative to the stresses at critical state. A unique relationship between the mean effective stress and a fabric anisotropy parameter, K, defined by the first joint invariant of the deviatoric stress tensor and the deviatoric fabric tensor, is found at critical state, and is path-independent. Numerical simulations using the discrete-element method under different loading conditions and intermediate principal stress ratios identify a unique power law for this relationship. Based on the findings, a new definition of critical state for granular media is proposed. In addition to the conditions of constant stress and unique void ratio required by the conventional critical state concept, the new definition imposes the additional constraint that K reaches a unique value at critical state. A unique spatial critical state curve in the three-dimensional space K–e–p′ is found for a granular medium, the projection of which onto the e–p′ plane turns out to be the conventional critical state line. The new critical state concept provides an important reference state for a soil to reach, based on which the key concepts in the constitutive modelling of granular media, including the choice of state parameters, dilatancy relation and non-coaxiality, are reassessed, and future exploratory topics are discussed.
Publisher: CRC Press
Date: 26-08-2014
DOI: 10.1201/B17395-134
Publisher: American Society of Civil Engineers (ASCE)
Date: 12-2013
Publisher: Elsevier BV
Date: 09-2022
Publisher: Springer Science and Business Media LLC
Date: 14-12-2019
Publisher: Wiley
Date: 12-07-2019
DOI: 10.1002/NAG.2951
Publisher: Elsevier BV
Date: 03-2014
Publisher: Elsevier BV
Date: 05-2020
Publisher: Mathematical Sciences Publishers
Date: 09-2006
Publisher: Elsevier BV
Date: 05-2020
Publisher: Springer Science and Business Media LLC
Date: 29-05-2021
Publisher: Springer Science and Business Media LLC
Date: 09-08-2022
Publisher: Elsevier BV
Date: 10-2013
Publisher: AIP
Date: 2013
DOI: 10.1063/1.4811909
Publisher: Elsevier BV
Date: 04-2012
Publisher: American Society of Civil Engineers (ASCE)
Date: 06-2020
Publisher: Elsevier BV
Date: 11-2019
Publisher: American Society of Civil Engineers (ASCE)
Date: 12-2012
Publisher: Elsevier BV
Date: 06-2008
Publisher: American Society of Civil Engineers (ASCE)
Date: 07-2012
Publisher: American Society of Civil Engineers (ASCE)
Date: 05-2017
Publisher: Elsevier BV
Date: 09-2022
Publisher: Thomas Telford Ltd.
Date: 06-2019
Abstract: Particle crushing underpins important macroscopic behaviour of granular materials such as yielding, deformation, dilatancy, failure, mobility and packing features. The crushing condition and crushing pattern have commonly been examined for particles subjected to uniaxial loadings. In the real engineering context, a sand grain is typically in contact with several surrounding particles and is hence subjected to multi-directional loadings, a critical condition that has not been well accounted for in most crushing criteria and studies of crushing patterns relevant to discrete-based sand modelling. In this study, the crushing of single sand particles under different loading conditions is examined based on peridynamic simulations. The peridynamic method is found capable of realistically capturing the crushing of a sand particle under uniaxial loadings in terms of crushing load and the crushing pattern observed in experiments, and is able to simulate multi-contact particle crushing where experimental data are relatively scarce. By examining existing crushing criteria, it is found that the numerical results on the crushing load under multiple contacts compare favourably with the maximum contact force criterion, which states that particle crushing occurs when the maximum contact force reaches a threshold. It is observed that the number of child particles after the crushing of a sand particle bears no apparent correlation with the coordination number. The volumes of child particles can be statistically described by a normal or gamma distribution. The findings from the study offer insights into the behaviour of sand particle crushing, which can be useful for future discrete modelling of granular sand where crushing is important.
Publisher: Elsevier BV
Date: 2013
DOI: 10.1063/2.1302107
Publisher: American Geophysical Union (AGU)
Date: 12-2020
DOI: 10.1029/2020GL090458
Abstract: Granular materials have frequently been used as representations of natural fault gouges. Although they can reproduce proper avalanche behaviors, the universality of the scaling exponent of avalanche size remains debatable. As a core issue in both amorphous plasticity and geophysics, avalanche universality may help reconcile the avalanche behaviors of earthquake and granular materials into the same universality class. We examine numerically the signatures of stress avalanches emerging from quasi‐static shear of granular materials with different size polydispersity. A persistent serrated plastic flow phenomenon is observed in our models with varying polydispersity. The stress drop is well defined by a truncated power law distribution P ( s ) ~ s − τ exp(− s / s max ) . The exponent τ and cutoff stress drop s max show a clear dependence on polydispersity, which reflects a tuned criticality. We further calculate the effective temperature from the statistics of energy fluctuations. The effective temperature volatility can be used to explain the tuned critical behaviors of granular gouge.
Publisher: American Geophysical Union (AGU)
Date: 06-2022
DOI: 10.1029/2021JF006587
Abstract: Flexible, slit, and rigid barriers are common countermeasures to mitigate natural geophysical mass flows, but presently, quantitative comparisons of their performance are lacking, due to the challenges involved in accurately representing the multi‐body and multi‐phase interactions. This study presents a numerical appraisal on this issue using a physics‐based coupled computational fluid dynamics and discrete element method (CFD‐DEM). A geophysical flow is considered as a mixture of discrete gap‐graded particles (DEM) and a continuous viscous slurry (CFD), whereas a permeable and deformable barrier structure can be modeled by DEM. The in‐flow multiphase interactions and flow‐barrier interactions can be rigorously modeled by a coupling scheme between DEM and CFD. Our numerical simulations reasonably capture both field and experimental observations on key features of flow‐barrier interactions and barrier responses. The different intercepting mechanisms of three barriers via pile‐up and runup modes are revealed by qualitative and quantitative characterizations. Flexible barriers perform the best under runup mode regarding much larger peak load reduction ratios (up to 89%) due to their high permeability and Fr ‐dependent load‐deflection behavior. We further compile a barrier‐specific design diagram that suggests existing analytical models calibrated by limited experiments may underestimate the peak impact for slit and rigid barriers due to their neglect of large solid particles in the impinging flows while leading to overestimations for flexible barriers owing to inappropriate representations of barrier permeability and structural deformability. Our findings may offer a basis for model improvements and developments in practical barrier selection and design.
Publisher: AIP
Date: 2013
DOI: 10.1063/1.4812158
Publisher: Elsevier BV
Date: 12-2020
Publisher: American Geophysical Union (AGU)
Date: 05-2018
DOI: 10.1029/2017JB015366
Publisher: Springer Netherlands
Date: 2011
Publisher: Springer Science and Business Media LLC
Date: 24-05-2017
Publisher: Wiley
Date: 21-03-2022
DOI: 10.1002/NME.6963
Abstract: This study presents a scalable three‐dimensional (3D) multiscale framework for continuum‐discrete modeling of granular materials. The proposed framework features rigorous coupling of a continuum‐based material point method (MPM) and a discrete approach discrete element method (DEM) to enable cross‐scale modeling of boundary value problems pertaining to granular media. It employs MPM to solve the governing equations of a macroscopic continuum domain for a boundary value problem that may undergo large deformation. The required loading‐path‐dependent constitutive responses at each material point of the MPM are provided by a DEM solution based on grain‐scale contact‐based discrete simulations that receive macroscopic information at the specific material point as boundary conditions. This hierarchical coupling enables direct dialogs between the macro and micro scales of granular media while fully harnessing the predictive advantages of both MPM and DEM at the two scales. An effective, scalable parallel scheme is further developed, based on the flat message passing interface (MPI) model, to address the computational cost of the proposed framework for 3D large‐scale simulations. We demonstrate that the proposed parallel scheme may offer up to 32X and 40X speedup in strong and weak scaling tests, respectively, significantly empowering the numerical performance and predictive capability of the proposed framework. The 3D parallelized multiscale framework is validated by an element test and a column collapse problem, before being applied to simulate the intrusion of a solid object. The multiscale simulation successfully captures the characteristic response of intrusion as postulated by the modified Archimedes' law theory. The progressive development of the stagnant zone during the intrusion is further examined from a cross‐scale perspective.
Publisher: Wiley
Date: 23-10-2022
DOI: 10.1002/NME.7139
Abstract: Neighbor searching is an essential and computationally heavy step in particle‐based numerical methods such as discrete element method (DEM), molecular dynamics, peridynamics, and smooth particle hydrodynamics. This article presents a novel approach to accelerate particle‐based simulations by leveraging ray tracing (RT) cores in addition to CUDA cores on RTX GPUs. The neighbor search problem is first numerically converted into a general ray tracing problem so that it can be possible to utilize the hardware acceleration of RT cores. A new, general‐purpose RT‐based neighbor search algorithm is then proposed and benchmarked with a prevailing cell‐based one. As a showcase, both algorithms are implemented into a GPU‐based DEM code for simulating large‐scale granular problems including packing, column collapse and debris flow. The overall simulation performance is examined with varying problem sizes and GPU specs. It demonstrates that the RT‐based simulations are 10%–60% faster than the cell‐based ones, depending on the simulated problems and GPU specs. This study offers a new recipe for next‐generation high‐performance computing of large‐scale engineering problems using particle‐based numerical methods.
Publisher: AIP Publishing
Date: 08-2023
DOI: 10.1063/5.0161344
Abstract: This paper presents a numerical study on suspensions of monodisperse non-Brownian grains in a Couette flow. The fully resolved coupled smoothed particle hydrodynamics and discrete element method is employed to model the motion of arbitrarily shaped grains in a viscous fluid. The numerical method is benchmarked against its capability in accurately handling grain–fluid hydrodynamics and inter-grain collisions. It is then used to simulate suspension flows of varying particle Reynolds and Bagnold numbers subjected to different shear rates, solid concentrations, and solid-to-fluid density ratios. A special focus is placed on the effect of grain shape with different aspect ratios and convexities on the flow behavior. Both the inertia and the grain shape are found to affect the grain–fluid and inter-grain interactions and uniquely contribute to the overall shear stress and the rheology of the suspension. The local profiles of solid concentration suggest the presence of grain layering near the boundary walls, which becomes more pronounced with higher solid concentration and inertia, and increased non-circularity in grain shape. A further examination of the pair distribution function and average particle rotation reveals a strong correlation between suspension viscosity and grain microstructure and kinematics.
Publisher: Springer International Publishing
Date: 30-12-2014
Publisher: Wiley
Date: 13-06-2014
DOI: 10.1002/NME.4702
Publisher: Elsevier BV
Date: 10-2020
Publisher: Elsevier BV
Date: 02-2021
Publisher: Elsevier BV
Date: 11-2010
Publisher: Springer Science and Business Media LLC
Date: 10-08-2023
Start Date: 02-2008
End Date: 12-2008
Amount: $120,000.00
Funder: Australian Research Council
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