Local distortion of turbulence by dispersed particles

Eaton, John K.; Paris, Anthony; Burton, Tristan

doi:10.2514/6.1999-3643

Cited by 8 publications

(8 citation statements)

References 5 publications

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“…This idea may seem feasible if we consider the particles as a series of screens with an average mesh spacing of 15η k continuously falling through the turbulence. Eaton et al (1999) demonstrated that the flow distortions due to particles with Re p ∼ 10 extend several particle diameters (or η k in our case, since d p ∼ η k ) downstream. Not only do the particles add turbulence to the flow through particle wakes, but the energetic flow structure can be destroyed by this 'screen effect'.…”

Section: Energy Budgetsupporting

confidence: 50%

“…The particulate phase was spherical monodisperse glass beads, with a small but finite diameter, d p ∼ η k (Kolmogorov length scale). The particle Reynolds number based on the particle diameter, Re p ∼ 10, so the particle wake distortions extend several particles downstream and cannot be neglected (Eaton, Paris & Burton 1999). The particles were relatively heavy, with ρ p /ρ f ∼ 2000 and particle Stokes number based on the Kolmogorov time scale, St k ∼ 50.…”

Section: Objectivesmentioning

confidence: 99%

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Homogeneous and isotropic turbulence modulation by small heavy ($St\sim 50$) particles

2006

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The interaction of a dilute dispersion of small heavy particles with homogeneous and isotropic air turbulence has been investigated. Stationary turbulence (at Taylor micro-scale Reynolds number of 230) with small mean flow was created in a nearly spherical sealed chamber by means of eight synthetic jet actuators. Two-dimensional particle image velocimetry was used to measure global turbulence statistics in the presence of spherical glass particles that had a diameter of 165 $\umu$m, which was similar to the Kolmogorov length scale of the flow. Experiments were conducted at two different turbulence levels and particle mass loadings up to 0.3. The particles attenuated the fluid turbulence kinetic energy and viscous dissipation rate with increasing mass loadings. Attenuation levels reached 35–40% for the kinetic energy (which was significantly greater than previous numerical studies) and 40–50% for the dissipation rate at the highest mass loadings. The main source of fluid turbulence kinetic energy production in the chamber was the speakers, but the loss of potential energy of the settling particles also resulted in a significant amount of production of extra energy. The sink of fluid energy in the chamber was due to the ordinary viscous dissipation and extra dissipation caused by particles. The extra dissipation was greatly underestimated by conventional models.

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Section: Energy Budgetsupporting

confidence: 50%

Section: Objectivesmentioning

confidence: 99%

Homogeneous and isotropic turbulence modulation by small heavy ($St\sim 50$) particles

2006

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“…Details of the flow distortion caused by the particles must play some role in determining the overall turbulence modification. Recent calculations by Eaton, Paris & Burton (1999) have shown that the flow distortion around the particle is a strong function of Reynolds number when the Reynolds number is of order 10, as it is in the present flow. The flow distortion is localized to a nearly symmetric region extending a few particle diameters at Re p = 1, but by Re p = 10 a strong asymmetry develops with the wake distortion extending many particle diameters downstream.…”

Section: Gas-phase Velocitiesmentioning

confidence: 48%

Turbulence modification by particles in a backward-facing step flow

1999

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The current study investigates turbulence modification by particles in a backward-facing step flow with a fully developed channel flow inlet. This flow provides a range of flow regimes in which to compare turbulence modification under the same experimental conditions. Gas-phase velocities in the presence of 3–40% mass loadings of three different particle classes (90 and 150 μm diameter glass and 70 μm diameter copper spheres) were measured. Attenuation of the streamwise fluid turbulence of up to 35% was observed in the channel-flow extension region of the flow for a 40% mass loading of the largest particles. The level of attenuation decreased with decreasing particle Stokes number, particle Reynolds number and mass loading. No modification of the turbulence was found in the separated shear layer or in the redevelopment region behind the step, although there were significant particle loadings in these regions.

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“…It is known from previous studies that there is a physical increase in the carrier phase turbulence and this is attributed to the wake formation behind these large particles similar to the ones behind the cylinders encountered in single phase flows. Experimental studies from Eaton et al26 state that for Re p around 10, the modulation is caused due to the strong asymmetric wake distortion extending many particle diameters downstream, whereas for Re p =1, the flow distortion is highly localized to a nearly symmetric region extending only a few particle diameters. Taking this into consideration one would expect a significant enhancement of the carrier phase turbulence for the glass particles, but in contrast significant attenuation have taken place, the maximum attenuation is noted at location x/h = 2, and the attenuation of glass particles is roughly about 44% more than its counterpart copper particles.…”

Section: Resultsmentioning

confidence: 99%

Two‐fluid model for particle‐turbulence interaction in a backward‐facing step

Mohanarangam¹,

Tu²

2007

AIChE Journal

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in Wiley InterScience (www.interscience.wiley.com).Particle-turbulence interaction for dilute gas-particle flows over a backward-facing step geometry is numerically investigated. An Eulerian two-fluid model with additional turbulence transport equations for particles is employed in this investigation. RNG based k-e model is used as the turbulent closure with additional transport equations solved, to better represent the combined gas-particle interactions. Two different particle classes with same Stokes number and varied particle Reynolds number are considered in this study. The turbulence modulation of the carrier phase in the presence of the dispersed particulate phase is simulated and compared against the experimental data. However prior to this endeavour, the simulated flow field is validated for mean streamwise velocities and fluctuations for both the phases. Despite the fact that the two particles used in this study share the same Stokes number their behavior is found to be considerably different in the turbulent flow field, which basically underlines the fact that the Stokes number alone is not enough to fully describe the behavior of particles, thereby, herein particle Reynolds number is also investigated to fully understand their behavior. Two other turbulence modulation models were also tested against our own formulation, and our model was found to compare better with the experimental findings.

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Local distortion of turbulence by dispersed particles

Cited by 8 publications

References 5 publications

Homogeneous and isotropic turbulence modulation by small heavy ($St\sim 50$) particles

Homogeneous and isotropic turbulence modulation by small heavy ($St\sim 50$) particles

Turbulence modification by particles in a backward-facing step flow

Two‐fluid model for particle‐turbulence interaction in a backward‐facing step

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