Effect of particle size on modulating turbulent intensity

Gore, Robert; Crowe, C. T.

doi:10.1016/0301-9322(89)90076-1

Cited by 652 publications

(330 citation statements)

References 19 publications

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“…Λ = 6 mm. According to the rule of thumb suggested by Gore & Crowe (1989), particles should dampen the turbulence in these conditions. However, after the VIO adjustment we find no apparent change in energy decay, except far downstream.…”

Section: Comparison With Empirical Rulesmentioning

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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Section: Comparison With Empirical Rulesmentioning

confidence: 99%

Particle–fluid interactions in grid-generated turbulence

Poelma¹,

Westerweel²,

Ooms³

2007

J. Fluid Mech.

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“…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. Kulick, Fessler & Eaton (1994) conducted experiments of a fully developed channel flow with solid particle mass loadings as large as 80%.…”

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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“…If the preheating is selected, a hot air coming from the preheater (4) should be mixed with the cold mixture of air /olive cake. In the both case, the mixture of air /olive cake goes in the burner (5). The main injector pipe (5) has an inner diameter of 30 mm and a height of 300 mm.…”

Section: Presentation Of the Conveying Systemmentioning

confidence: 99%

“…Gore and Crowe [5] have investigated the effect of the particles size on the flow behavior in a pipe. They have concluded that if the ratio of particles size by flow length scale (dp/Le) is less than 0.1 then the turbulence has reduced and else that has amplified.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Gas-Particles Two Phase Flow in Pipe of Complex Geometry: Pneumatic Conveying of Olive Cake Particles Toward a Dust Burner

Bounaouara¹,

Ettouati²,

Ticha³

et al. 2015

IJHT

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Two phase CFD calculations, using Eulerian-Lagrangian model with commercial Fluent 6.3 were employed to predict the gas and particle flow in pipe of complex geometry designed for pneumatic conveying of olive cake particles toward a pulverized burner. The numerical calculations were validated against experimental data from the literature. The effects of gas velocity and particles size distribution on the mixture flow behavior were studied. The present results help to understand the phenomena occurring in gas-solid flow and optimizing the conveying system.

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Effect of particle size on modulating turbulent intensity

Cited by 652 publications

References 19 publications

Particle–fluid interactions in grid-generated turbulence

Particle–fluid interactions in grid-generated turbulence

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

Numerical Simulation of Gas-Particles Two Phase Flow in Pipe of Complex Geometry: Pneumatic Conveying of Olive Cake Particles Toward a Dust Burner

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