On the two-way interaction between homogeneous turbulence and dispersed solid particles. I: Turbulence modification

Elghobashi, S.; Truesdell, G. C.

doi:10.1063/1.858854

Cited by 533 publications

(364 citation statements)

References 21 publications

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“…Kenning & Crowe 1997); however, these kinetic energy increases were generally attributed to either droplet wake or gravitational effects and occurred only for large droplets having D/l > 10 −1 where l is the integral lengthscale of the turbulence (e.g. Elghobashi & Truesdell 1993). Thirdly, the streamwise component energy is slightly increased by the droplets at the centreline (figure 19a); this is due to the influence of negative slip velocities in regions of decelerating gas flow within the high-concentration braids structures (figure 10a) which serve as a source of gas phase kinetic energy.…”

Section: Second-order Statisticsmentioning

confidence: 99%

“…Elghobashi & Truesdell 1993). Gore & Crowe (1989) compiled results from a variety of experiments which suggest that solid particles can act either to dissipate or to enhance turbulence energy depending on the diameter of the particles relative to the integral lengthscale of the flow; however, no conclusions could be drawn as to the magnitude of the modulation.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Second-order Statisticsmentioning

confidence: 99%

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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“…Owing to the very high numerical demands, most of these have used a number of simplifications: the dispersed phase is often modelled as point particles (Elghobashi & Truesdell 1993;Boivin, Simonin & Squires 2000). Rather than solving the full equation of motion of the particles, it is usually considerably simplified by considering cases with a large density ratio (Squires & Eaton 1990;Ferrante & Elghobashi 2003).…”

Section: Earlier Workmentioning

confidence: 99%

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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“…Gore & Crowe (1989) suggested that turbulence will be augmented or suppressed depending on the ratio of particle dimension to a turbulent length scale. Elghobashi & Truesdell (1993) concluded that 'the particles, due to their inertia impart their energy to the turbulent motion at high wavenumbers with a corresponding increase in the dissipation. The enhanced dissipation signals the smaller wavenumbers (larger scales), to supply more energy to the highly active small scales, at a rate higher than that of the particle-free case'.…”

Section: Introductionmentioning

confidence: 99%

Large-eddy simulation of particle-laden turbulent flows

2008

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A large-eddy-based methodology for the simulation of turbulent sprays is discussed. The transport equations for the spatially filtered gas phase variables, in which source terms accounting for the droplet effects are added, are solved together with a probabilistic description of the liquid phase. The probabilistic approach for the liquid phase is based on the transport equation for the spatially filtered joint probability density function of the variables required in order to describe the state of the liquid phase. In this equation, unclosed terms representing the filtered Lagrangian rates of change of the variables describing the spray are present. General modelling ideas for subgrid-scale (SGS) effects are proposed. The capabilities of the approach and the validity of the closure models, with particular with respect to the SGS dispersion, are investigated through application to a dilute particle-laden turbulent mixing layer. It is demonstrated that the formulation is able to reproduce very closely the measured properties of both the continuous and dispersed phases. The large-eddy simulation (LES) results are also found to be entirely consistent with the experimentally observed characteristics of droplet-gas turbulence interactions. Consistent with direct numerical simulation (DNS) studies of isotropic turbulence laden with particles where the entire turbulence spectrum is found to be modulated by the presence of particles, the present investigation, which comprises the effects of particle transport upon the large-scale vortical structures of a turbulent shear flow, highlights what appears to be a selective behaviour; few large-scale frequencies gain energy whereas the remaining modes are damped.

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On the two-way interaction between homogeneous turbulence and dispersed solid particles. I: Turbulence modification

Cited by 533 publications

References 21 publications

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

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

Particle–fluid interactions in grid-generated turbulence

Large-eddy simulation of particle-laden turbulent flows

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