Inter-wake turbulence properties in homogeneous particle-laden flows

Chen, Jeng-Horng; Faeth, G. M.

doi:10.2514/6.1999-3758

Cited by 5 publications

(8 citation statements)

References 14 publications

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“…31 into Eq. 33, a relationship between the coefficients associated with the production of dissipation due to presence of particles and the total dissipation of dissipation within the fluid results in: Crowe and Wang25 compiled data from several different authors5–15 and showed a correlation between the relative Reynolds number and the ratio of Taylor length scale to particle diameter. Most of the data fit remarkably well, however a few sets of data seemed to deviate.…”

Section: Resultsmentioning

confidence: 99%

“…The modulation of turbulence due to the presence of particles is attributed to the altered dissipation within the continuous phase caused by the work done at the surfaces of the particles 4. The modulation of turbulence in particle laden flows has been demonstrated by extensive experimentation over the last two decades 5–15. However, a turbulence model that adequately predicts these modulations over a wide range of data is still lacking.…”

Section: Introductionmentioning

confidence: 99%

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A turbulence dissipation model for particle laden flow

2009

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A dissipation transport equation for the carrier phase turbulence in particle‐laden flow is derived from fundamental principles. The equation is obtained by volume averaging, which inherently includes the effects of the particle surfaces. Three additional terms appear that reveal the effect of the particles; these terms are evaluated using Stokes drag law. Two of the terms reduce to zero and only one term remains which is identified as the production of dissipation due to the particles. The dissipation equation is then applied to cases where particles generate homogeneous turbulence, and experimental data are used to evaluate the empirical coefficients. The ratio of the coefficient of the production of dissipation (due to the presence of particles) to the coefficient of the dissipation of dissipation is found to correlate well with the relative Reynolds number. © 2009 American Institute of Chemical Engineers AIChE J, 2009

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A turbulence dissipation model for particle laden flow

2009

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“…1151-1163. 4 = particle diameter f i = volume fraction of region i n 0 0 = particle number ux U p = mean streamwise relative velocity of a particle u, v = instantaneous streamwise and cross-stream gas velocitȳ u,v = mean streamwise and cross-stream gas velocitȳ u 0 ,v 0 = rms uctuating streamwise and cross-stream velocity e = local rate of dissipation of turbulence kinetic energy } = average generic property of the overall ow } i = average generic property of region i of the ow Subscripts i = turbulent interwake region w = particle wake region Introduction T URBULENCE generation is de ned as the direct disturbance of the continuous-phase velocity eld by the wakes of dispersed-phase objects in dispersed multiphase ows. Turbulence generation supplements the conventional production of turbulence caused by mean velocity gradients in the continuous phase; it is most important when dispersed-phase objects have large relative velocities (large Reynolds numbers) and relatively large relaxation times compared to characteristic turbulence times.…”

Section: Discussionmentioning

confidence: 97%

“…Corresponding values of u i for the turbulent interwake region for these properties could be obtained directly from the correlations of Chen and Faeth. 4 The analogous values of u w for the laminarlike turbulent wake region for these properties were obtained as averages over the volume used to nd f w . Distributions of mean streamwise velocities contribute along with streamwise velocity uctuations when the laminarlike turbulent wake contribution toū 0 2 is found because the arrival of particle wakes is random.…”

Section: Theoretical Methodsmentioning

confidence: 99%

“…in terms of the dimensionless dissipation factor and known properties of the dispersed phase. 4 Motivated by these observations, the objective of the present investigation was to develop a way to predict the overall properties of the continuous phase of ows caused by turbulence generation, seeking to account for the random arrival of particle wakes and incorporating the known properties of laminarlike turbulent wakes and the turbulent interwake region. Information of this type would be measured in the continuous phase of ow dominated by turbulence generation and is of considerable importance as a result.…”

Section: Referencesmentioning

confidence: 99%

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Continuous-Phase Properties of Homogeneous Particle-Laden Turbulent Flows

Chen

Faeth

2001

AIAA Journal

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parameters used in the code. The time breakdown is shown in Table 1. With the present procedure a mesh of 10 5 cells requires about 191 s of CPU time. It can be seen that the most expensive part of the algorithm is the elimination of nodes of degree higher than seven. The cause of this inef ciency has not been tracked in detail but must be attributed to a bad practice in the implementation of the algorithm. If the node-degree homogenization techniques are not employed, then the time is reduced to 70 s approximately.It has been reported 2 that the time necessary to generate a twodimensionalgrid with 10 5 elements it is about 17 s on an SGI Indigo 2 R4400. The same author claims that the equivalent method for the generation of a surface grid requires three times as much CPUtime as the two-dimensional planar procedure. Thus the total cost can be estimated in about 1 min of CPU time, which is more or less the same amount obtained if the node-degree homogenization technique is removed from Table 1. ConclusionsA method for the ef cient generation of unstructured grids on arbitrary surfaces based in Steiner triangulations has been presented. The mesh-generation system uses an internal representation of the surface to isolate the grid-generation and CAD systems. The algorithm does not need the tracking of fronts, and therefore its implementation is attractive because of its simplicity. A special lter has been devised to avoid the generation of sawtooth patterns on the surface during the early stages of the gridding process, and this has proved to be an essential part of the method. The quality of the surface and planar grids obtained by the present approach are similar, but still below the attainable by means of an AF point-placement strategy. AcknowledgmentsThis project has been funded by the Industria de Turbo Propulsores under Contract ITP-002-96 to the School of Aeronautics of the Universidad Politécnica de Madrid, and its permission to publish this Note is gratefully acknowledged.The authors would like to thank R. Gómez for an early implementation of a constrained version of the Bowyer-Watson algorithm and J. M. Barroso for help and useful comments during the development of this work. Nomenclature C D = particle drag coef cient D = dissipation factor; Eq.(2) d p = particle diameter f i = volume fraction of region i n 0 0 = particle number ux U p = mean streamwise relative velocity of a particle u, v = instantaneous streamwise and cross-stream gas velocitȳ u,v = mean streamwise and cross-stream gas velocitȳ u 0 ,v 0 = rms uctuating streamwise and cross-stream velocity e = local rate of dissipation of turbulence kinetic energy } = average generic property of the overall ow } i = average generic property of region i of the ow Subscripts i = turbulent interwake region w = particle wake region

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A fully resolved numerical simulation of turbulent flow past one or several spherical particles

Botto

Prosperetti

2012

Physics of Fluids

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The flow past one or nine spheres arranged in a plane lattice held fixed in a stream of decaying homogeneous isotropic turbulence is studied by means of fully resolved Navier-Stokes simulations. The particle radius is 3–5 times the Kolmogorov length and about 1/3 of the integral length scale. The mean particle Reynolds number is 80 and the turbulence intensity 17% and 33%. Several features of the flow are described: the mean and fluctuating dissipation and its spatial distribution, the mean and fluctuating hydrodynamic forces on the spheres, stimulated vortex shedding, and others. A special attention is paid to the relation between the work done on the fluid by the particles (in the reference frame of the former) and the total dissipation. It is shown that these quantities, which are assumed to balance in many point-particle models, can actually be very different when inertial effects are important.

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Inter-wake turbulence properties in homogeneous particle-laden flows

Cited by 5 publications

References 14 publications

A turbulence dissipation model for particle laden flow

A turbulence dissipation model for particle laden flow

Continuous-Phase Properties of Homogeneous Particle-Laden Turbulent Flows

A fully resolved numerical simulation of turbulent flow past one or several spherical particles

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