On predicting particle-laden turbulent flows

Elghobashi, S.

doi:10.1007/bf00936835

Cited by 1,262 publications

(742 citation statements)

References 28 publications

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“…The values of Re p , using particle size and measured terminal velocity, range from 1.3 (P0) to 30 (P1). Again, this would indicate a damping of turbulence (Elghobashi 1994), while only an increase is observed far downstream. The Stokes numbers range from 0.06 (P0) to 0.48 (P1).…”

Section: Comparison With Empirical Rulesmentioning

confidence: 94%

“…Similar criteria for predicting turbulence augmentation versus attenuation have been introduced by e.g. Hetsroni (1989), who used the Stokes number, and Elghobashi (1994), who used the particle Reynolds number. In practice, it is far from straightforward to vary a single parameter such as the Stokes number, while keeping all other parameters in the experiment constant.…”

Section: Introductionmentioning

confidence: 99%

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Particle–fluid interactions in grid-generated turbulence

Poelma¹,

Westerweel²,

Ooms³

2007

J. Fluid Mech.

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The effect of small particles on decaying grid-generated turbulence is studied experimentally. Using a two-camera system, instantaneous fluid-phase and particlephase measurements can be obtained simultaneously. The data obtained with this system are used to study the decay behaviour of the turbulent flow. The role of particle size, particle density and volume load is studied in a number of different cases. These cases are chosen so that the individual role of these parameters can systematically be evaluated. Addition of particles to the flow has significant effects on the decaying turbulence: first, the onset of the turbulent decay appears to shift upstream; second, the flow becomes anisotropic as it develops downstream. The latter is observed as an increase in integral length scale in the vertical direction. The rate at which the flow becomes anisotropic can be predicted using a new parameter: the product of the non-dimensional number density and the Stokes number (referred to as the 'Stokes load'). This parameter, combining the relevant fluid and particle characteristics, is a measure for the energy redistribution leading to anisotropy. In addition to redistributing energy, the particles also produce turbulence. However, this only becomes evident when the grid-generated turbulence has decayed sufficiently, relatively far downstream of the grid. The turbulence production by particles can also account for the observed decrease in slope of the power spectrum, which leads to a 'cross-over' effect. The production of turbulence by the particles can be predicted using a model for the momentum deficit of the particle wakes. The validity of this approach is confirmed using conditional sampling of the fluid velocity field around the particles.

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Section: Comparison With Empirical Rulesmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Particle–fluid interactions in grid-generated turbulence

Poelma¹,

Westerweel²,

Ooms³

2007

J. Fluid Mech.

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“…Elghobashi [59] could, given time, be implemented in the FLUENT-EDEM code. Figure. 12 shows the horizontal profile of the simulated and measured mean gas velocity in the presence of 1.5 mm spherical particles at SLR=2.3, 3 and 3.5.…”

Section: Sources Of Discrepancies Between Simulation and Experimentsmentioning

confidence: 99%

Numerical and experimental study of horizontal pneumatic transportation of spherical and low-aspect-ratio cylindrical particles

2016

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“…spray mixing, spray combustion, atomization, painting and weather prediction (see e.g. Elghobashi 1994). Of particular interest to the investigation are the characterization of the droplet size and concentration distributions, as well as an elucidation of flow modulation due to phase couplings of mass, momentum and energy in a planar mixing-layer configuration.…”

Section: Introductionmentioning

confidence: 99%

“…The 'Eulerian-Lagrangian' approach is adopted in which every individual droplet is tracked in a time accurate manner using a Lagrangian reference frame (in contrast to the 'Eulerian-Eulerian' approach which describes the dispersed phase as an interpenetrating continuum derived by averaging over sufficiently large local ensembles of droplets, e.g. Zhou 1993;Elghobashi 1994). Present-day supercomputers have been instrumental in the success of DNS for simulating single-phase turbulent flows at all scales for sufficiently low Reynolds numbers; however, for two-phase gas-droplet flows they are still not powerful enough to simultaneously resolve the spatial scales interior and adjacent to individual droplets when the spatial flow scales are much larger than the droplet diameter.…”

Section: Introductionmentioning

confidence: 99%

Direct numerical simulation of a confined three-dimensional gas mixing layer with one evaporating hydrocarbon-droplet-laden stream

Miller¹,

1999

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Direct numerical simulations are performed of a confined three-dimensional, temporally developing, initially isothermal gas mixing layer with one stream laden with as many as 7.3×10 5 evaporating hydrocarbon droplets, at moderate gas temperature and subsonic Mach number. Complete two-way phase couplings of mass, momentum and energy are incorporated which are based on a thermodynamically self-consistent specification of the vapour enthalpy, internal energy and latent heat of vaporization. Effects of the initial liquid mass loading ratio (ML), initial Stokes number (St 0 ), initial droplet temperature and flow three-dimensionality on the mixing layer growth and development are discussed. The dominant parameter governing flow modulation is found to be the liquid mass loading ratio. Variations in the initial Stokes number over the range 0.5 6 St 0 6 2.0 do not cause significant modulations of either first-or second-order gas phase statistics. The mixing layer growth rate and kinetic energy are increasingly attenuated for increasing liquid loadings in the range 0 6 ML 6 0.35. The laden stream becomes saturated before evaporation is completed for all but the smallest liquid loadings owing to: (i) latent heat effects which reduce the gas temperature, and (ii) build up of the evaporated vapour mass fraction. However, droplets continue to be entrained into the layer where they evaporate owing to contact with the relatively higher-temperature vapour-free gas stream. The droplets within the layer are observed to be centrifuged out of high-vorticity regions and to migrate towards high-strain regions of the flow. This results in the formation of concentration streaks in spanwise braid regions which are wrapped around the periphery of secondary streamwise vortices. Persistent regions of positive and negative slip velocity and slip temperature are identified. The velocity component variances in both the streamwise and spanwise directions are found to be larger for the droplets than for the gas phase on the unladen stream side of the layer; however, the cross-stream velocity and temperature variances are larger for the gas. Finally, both the mean streamwise gas velocity and droplet number density profiles are observed to coincide for all ML when the cross-stream coordinate is normalized by the instantaneous vorticity thickness; however, first-order thermodynamic profiles do not coincide.

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On predicting particle-laden turbulent flows

Cited by 1,262 publications

References 28 publications

Particle–fluid interactions in grid-generated turbulence

Particle–fluid interactions in grid-generated turbulence

Numerical and experimental study of horizontal pneumatic transportation of spherical and low-aspect-ratio cylindrical particles

Direct numerical simulation of a confined three-dimensional gas mixing layer with one evaporating hydrocarbon-droplet-laden stream

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