Fully coupled LES-DEM of particle interaction and agglomeration in a turbulent channel flow

Afkhami, Mohammad; Hassanpour, Ali; Fairweather, Michael; Njobuenwu, Derrick O.

doi:10.1016/j.compchemeng.2015.04.003

Cited by 55 publications

(21 citation statements)

References 75 publications

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“…The first LES of particle-laden flow, in particular, was performed under the assumption of negligible contribution of the SGS fluctuations to the filtered fluid velocity seen by inertial particles [11]: The choice was justified considering that inertial particles act as low-pass filters that respond selectively to removal of SGS flow scales according to a characteristic frequency proportional to 1/τ p , where τ p is the particle relaxation time (a measure of particle inertia). The same assumption has been used in other studies [12][13][14][15] in which the filtering due to particle inertia and the moderate Reynolds number of the flow had a relatively weak effect on the (one-particle, two-particles) dispersion statistics examined. However, several studies [16][17][18] have demonstrated that neglecting the effect of SGS velocity fluctuations on particle motion leads to significant errors in the quantification of large-scale clustering and preferential concentration, two macroscopic phenomena that result from particle preferential distribution at the periphery of strong vortical regions into low-strain regions [19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Lagrangian filtered density function for LES-based stochastic modelling of turbulent particle-laden flows

2016

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The Eulerian-Lagrangian approach based on Large-Eddy Simulation (LES) is one of the most promising and viable numerical tools to study turbulent dispersed flows when the computational cost of Direct Numerical Simulation (DNS) becomes too expensive. The applicability of this approach is however limited if the effects of the Sub-Grid Scales (SGS) of the flow on particle dynamics are neglected. In this paper, we propose to take these effects into account by means of a Lagrangian stochastic SGS model for the equations of particle motion. The model extends to particle-laden flows the velocity-filtered density function method originally developed for reactive flows. The underlying filtered density function is simulated through a Lagrangian Monte Carlo procedure that solves for a set of Stochastic Differential Equations (SDEs) along individual particle trajectories. The resulting model is tested for the reference case of turbulent channel flow, using a hybrid algorithm in which the fluid velocity field is provided by LES and then used to advance the SDEs in time. The model consistency is assessed in the limit of particles with zero inertia, when "duplicate fields" are available from both the Eulerian LES and the Lagrangian tracking. Tests with inertial particles were performed to examine the capability of the model to capture particle preferential concentration and near-wall segregation. Upon comparison with DNS-based statistics, our results show improved accuracy and considerably reduced errors with respect to the case in which no SGS model is used in the equations of particle motion.2

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Section: Introductionmentioning

confidence: 99%

Lagrangian filtered density function for LES-based stochastic modelling of turbulent particle-laden flows

2016

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“…LES coupled to the hard-sphere collision model [15][16][17] and energy-balanced and momentum-balanced agglomeration models 4,[18][19][20] have been used to study interparticle collision and particle agglomeration in turbulent channel flow. Afkhami et al 21 and Hellestø et al 22 applied LES coupled to the discrete element method based on the soft-sphere collision model 23 to model particle agglomeration in solid-liquid turbulent channel flow. Ho and Sommerfeld 24 , and…”

Section: Takedownmentioning

confidence: 99%

Large eddy simulation of particle agglomeration with shear breakup in turbulent channel flow

Njobuenwu

Fairweather

2018

Physics of Fluids

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A systematic technique is developed for studying particle dynamics as induced by a turbulent liquid flow, in which transport, agglomeration and breakup are considered. An Eulerian description of the carrier phase obtained using large eddy simulation is adopted and fully coupled to a Lagrangian definition of the particle phase using a pointwise discrete particle simulation. An efficient hard-sphere interaction model with deterministic collision detection enhanced with an energy-balance agglomeration model was implemented in an existing computational fluid dynamic code for turbulent multiphase flow. The breakup model adopted allows instantaneous breakup to occur once the transmitted hydrodynamic stress within an agglomerate exceeds a critical value, characterised by a fractal dimension and the size of the agglomerate. The results from the developed technique support the conclusion that the local turbulence kinetic energy, its dissipation rate and the agglomerate fractal dimension control the kinetics of the agglomeration and de-agglomeration processes, and as well as defining with time the morphology of the particles and their resultant transport. Overall, the results are credible and consistent with the expected physical behaviour and with known theories.

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“…The increased surface area of garnet after modification explains the better dispersion of MG microparticles [33]. Surface energy of unMG is relatively high: according to the principle of minimum energy, unMG particles will aggregate to reduce surface energy [36]. Therefore, a serious reunion phenomenon occurred among garnet particles.…”

Section: Physicochemical Properties Of Mgmentioning

confidence: 99%

Surface-Modified Garnet Particles for Reinforcing Epoxy Composites

Jiang

Liu

et al. 2018

Minerals

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The present study investigated the tribological performance of epoxy (EP) matrix composites enhanced with natural garnet. The garnet was surface-modified with sodium stearate for optimal performance. Composites comprising different contents and particle sizes of modified garnet (MG) were prepared with a mixture of EP and MG. The sodium stearate-bonded garnet and EP formed a stable structure. Tribological performance was measured by a ball-on-plate apparatus under permanent dry sliding conditions and a wear track was obtained by an optical profilometer. The wear mechanism was explored by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) images. Wear test results showed that the coefficient of friction for all EP/MG composites decreased compared with that for neat epoxy. The results also indicated that the addition of MG can evidently improve the tribological properties of EP matrix composites.

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Fully coupled LES-DEM of particle interaction and agglomeration in a turbulent channel flow

Cited by 55 publications

References 75 publications

Lagrangian filtered density function for LES-based stochastic modelling of turbulent particle-laden flows

Lagrangian filtered density function for LES-based stochastic modelling of turbulent particle-laden flows

Large eddy simulation of particle agglomeration with shear breakup in turbulent channel flow

Surface-Modified Garnet Particles for Reinforcing Epoxy Composites

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