LES-DEM simulations of sediment transport

Elghannay, Husam A.; Tafti, Danesh K.

doi:10.1016/j.ijsrc.2017.09.006

Cited by 25 publications

(12 citation statements)

References 59 publications

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“…The numerical experiments from using full coupling and base partial coupling showed good agreement in the bedload regime but underpredicted the sediment transport in the suspended load regime as compared to empirical formulas. 33 By moderately reducing the friction factor used in the numerical simulations good agreement was achieved in both bedload and suspended load regimes. 37 By comparing the base partial coupling predictions to the full-coupling approach it was found that the difference between the two was smaller in the bedload regime but became more obvious in the suspended load regime.…”

Section: Simulation Details and Resultsmentioning

confidence: 95%

“…Our previous work included 10 numerical experiments ranging from near incipience of motion of particles to strong suspension of particles. 33 At low flow rates or friction velocity, particle transport occurs in the bedload regime where particles move by rolling, sliding, and making small jumps over the bed (saltating). As the flow increases, particles get suspended in the flow by the action of turbulent structures and transport enters the suspended load regime.…”

Section: Simulation Details and Resultsmentioning

confidence: 99%

“…37 By comparing the base partial coupling predictions to the full-coupling approach it was found that the difference between the two was smaller in the bedload regime but became more obvious in the suspended load regime. 33 This was because in the bedload regime, most of the particles are static in the bed and the smaller drag force predicted by the partial coupling did not have a large impact, while in the suspended load regime many more particles are mobile and an underprediction of drag would have a much larger impact on overall particle transport.…”

Section: Sediment Transport In Turbulent Open Channelmentioning

confidence: 99%

“…The differences between coupling the disperse phase to a multiphase flow solver (full coupling) and coupling the particles to a single-phase flow solver (will refer to this as the "base partial coupling") was investigated by Elghannay and Tafti 33 in sediment transport under turbulent conditions. The fully coupled method solved the volume-averaged Navier-Stokes equations including the effect of void fraction and drag forces from the solid phase.…”

Section: Introductionmentioning

confidence: 99%

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Revised partial coupling in fluid–particulate systems

Elghannay

Tafti

2018

The Journal of Computational Multiphase Flows

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Fluid equations in Computational Fluid Dynamics coupled with Discrete Element Method (CFD-DEM) simulations solve the volume-averaged Navier-Stokes equations. Full coupling between the dispersed phase and continuous phase is made by the exchange of source terms as well as the void fraction. The void fraction is calculated from the presence of the particles in the computational fluid cells while the source terms are calculated from the point mass force models of the fluid-particle interaction forces. Dense particulate system with large spatiotemporal variations in the void fraction shows hard convergence behavior. This can impact the robustness of the solver during the time integration process. One option is to use partial coupling by neglecting the explicit effect of void fraction in the fluid momentum equations while retaining its effect on force models. Although the partial coupling is more stable and shows better convergence behavior, the mobility of the particles is found to be reduced as compared to the full-coupling approach. In the current work, we propose a revised partial coupling in which a modified fluid velocity is used in point mass force models to compensate for the omission of the void fraction in the fluid governing equations. The effectiveness of this method is demonstrated in a fluidized bed and in sediment transport simulations. In both cases it is shown that the use of the proposed method gives very good comparisons with the fully coupled simulations while reducing the fluid calculation time by factors ranging from 1.35 to 4.35 depending on the flow conditions. The revised partial coupling is not recommended as a substitute for full coupling in dense systems but as an alternate approach when full coupling leads to numerical difficulties.

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Section: Simulation Details and Resultsmentioning

confidence: 95%

Section: Simulation Details and Resultsmentioning

confidence: 99%

Section: Sediment Transport In Turbulent Open Channelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Revised partial coupling in fluid–particulate systems

Elghannay

Tafti

2018

The Journal of Computational Multiphase Flows

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“…While classical instrumentation is improving as well (see, e.g., [295] for bedload measurements), more accurate formulations are proposed to account for various mechanisms such as, for example, recently: the bedload grain size distribution [121]; the alternative approach, referred to as the "entrainment flux method" for quantifying the erosion properties of surficial sediments [173]; the integration of multiple classes in 3D models [296]; or new probabilistic formulations for bedload [297]. New types of models are developed, tested and evaluated on simple configurations to improve knowledge of basic mechanisms at a fine scale, e.g., direct numerical simulation of bedform evolution and/or sediment transport [298,299], emerging methods of smoothed particle hydrodynamics for fluid-flow interaction [194]. In-depth theoretical analysis is also ongoing on bedload (e.g., [300,301]), on bedforms [302], on the transition from bedload to suspended load [303,304], on the granular flow rheology in bedload transport [305], amongst others.…”

Section: A Science Field That Evolves With Technologymentioning

confidence: 99%

Why and How Do We Study Sediment Transport? Focus on Coastal Zones and Ongoing Methods

Ouillon

2018

Water

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Scientific research on sediment dynamics in the coastal zone and along the littoral zone has evolved considerably over the last four decades. It benefits from a technological revolution that provides the community with cheaper or free tools for in situ study (e.g., sensors, gliders), remote sensing (satellite data, video cameras, drones) or modelling (open source models). These changes favour the transfer of developed methods to monitoring and management services. On the other hand, scientific research is increasingly targeted by public authorities towards finalized studies in relation to societal issues. Shoreline vulnerability is an object of concern that grows after each marine submersion or intense erosion event. Thus, during the last four decades, the production of knowledge on coastal sediment dynamics has evolved considerably, and is in tune with the needs of society. This editorial aims at synthesizing the current revolution in the scientific research related to coastal and littoral hydrosedimentary dynamics, putting into perspective connections between coasts and other geomorphological entities concerned by sediment transport, showing the links between many fragmented approaches of the topic, and introducing the papers published in the special issue of Water on "Sediment transport in coastal waters".

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