Turbulence attenuation in particle-laden flow in smooth and rough channels

Vreman, A.W.

doi:10.1017/jfm.2015.208

Cited by 88 publications

(83 citation statements)

References 58 publications

(127 reference statements)

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“…Kulick et al (1994) measured strong turbulence attenuation in a gas-solid turbulent channel flow with a particle volume fraction of 0.0001, particle size d + p = 2.3 and Re τ = 640. Recently, a point-particle DNS of this case was performed in a configuration that contained roughly 10 5 particles (Vreman 2015). However, significant differences from the experimental results were still observed.…”

Section: Discussionmentioning

confidence: 92%

“…The attenuation was attributed to the particle-induced dissipation term, a sink term that appears explicitly in the equation of the turbulence kinetic energy derived from the point-particle or related formulation. In particle-laden pipe and channel flows, the turbulence attenuation can be further enhanced by a second effect, which is non-uniformity of the mean particle force (Vreman 2007(Vreman , 2015.…”

Section: Introductionmentioning

confidence: 99%

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Particle-resolved direct numerical simulation of homogeneous isotropic turbulence modified by small fixed spheres

Vreman

2016

J. Fluid Mech.

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A statistically stationary homogeneous isotropic turbulent flow modified by 64 small fixed non-Stokesian spherical particles is considered. The particle diameter is approximately twice the Kolmogorov length scale, while the particle volume fraction is 0.001. The Taylor Reynolds number of the corresponding unladen flow is 32. The particle-laden flow has been obtained by a direct numerical simulation based on a discretization of the incompressible Navier-Stokes equations on 64 spherical grids overset on a Cartesian grid. The global (space-and time-averaged) turbulence kinetic energy is attenuated by approximately 9 %, which is less than expected. The turbulence dissipation rate on the surfaces of the particles is enhanced by two orders of magnitude. More than 5 % of the total dissipation occurs in only 0.1 % of the flow domain. The budget of the turbulence kinetic energy has been computed, as a function of the distance to the nearest particle centre. The budget illustrates how energy relatively far away from particles is transported towards the surfaces of the particles, where it is dissipated by the (locally enhanced) turbulence dissipation rate. The energy flux towards the particles is dominated by turbulent transport relatively far away from particles, by viscous diffusion very close to the particles, and by pressure diffusion in a significant region in between. The skewness and flatness factors of the pressure, velocity and velocity gradient have also been computed. The global flatness factor of the longitudinal velocity gradient, which characterizes the intermittency of small scales, is enhanced by a factor of six. In addition, several point-particle simulations based on the Schiller-Naumann drag correlation have been performed. A posteriori tests of the point-particle simulations, comparisons in which the particle-resolved results are regarded as the standard, show that, in this case, the point-particle model captures both the turbulence attenuation and the fraction of the turbulence dissipation rate due to particles reasonably well, provided the (arbitrary) size of the fluid volume over which each particle force is distributed is suitably chosen.

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Section: Discussionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Particle-resolved direct numerical simulation of homogeneous isotropic turbulence modified by small fixed spheres

Vreman

2016

J. Fluid Mech.

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“…Vreman [110] performed four-way coupled point-particle DNS of downward gas-solid flow in a vertical channel at Re τ =642 and with a mass loading of 0.8. He considered smooth and rough walls, where rough walls were modeled by fixing tiny spherical particles on the walls.…”

Section: Dns With Point-particle Approachmentioning

confidence: 99%

Point-Particle DNS and LES of Particle-Laden Turbulent flow - a state-of-the-art review

Kuerten

2016

Flow Turbulence Combust

162

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Particle-laden or droplet-laden turbulent flows occur in many industrial applications and in natural phenomena. Knowledge about the properties of these flows can help to improve the design of unit operations in industry and to predict for instance the occurrence of rain showers. This knowledge can be obtained from experimental research and from numerical simulations. In this paper a review is given of numerical simulation methods for particle-laden flows. There are various simulation methods possible. They range from methods in which all details, including the flow around each particle, are resolved, via point-particle methods, in which for each particle an equation of motion is solved, to Eulerian methods in which equations for particle concentration and velocity are solved. This review puts the emphasis on the intermediate class of methods, the Euler-Lagrange methods in which the continuous phase is described by an Eulerian approach and the dispersed phase in a Lagrangian way with equations of motion for each individual particle.

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“…The particle/particle collision weakens the preferential distribution of particles [29,35], and reduces maximum near-wall concentrations [26]. The particle/wall collisions also affect the particle-induced turbulence modulation [49]. In addition, particles at high mass loading tend to decrease the thickness of the boundary layer and increase the skin friction [50], and act as the primary source of turbulence generation [8,9].…”

Section: Introductionmentioning

confidence: 99%

“…Overall, this broad range of numerical investigations has relied heavily on the use of the point-force approximation, which is widely applied for systems with large numbers of small, heavy particles; see [29]; [24]; [54]; [17]; [28]; [49]; [52]. While experimental and numerical efforts have made significant progress in understanding the complex problem of particle-laden turbulent channel flow, there remains a continued lack of comparison and validation between consistent numerical and experimental observations [11].…”

Section: Introductionmentioning

confidence: 99%

Inertial particle velocity and distribution in vertical turbulent channel flow: A numerical and experimental comparison

Wang

Fong

Coletti

et al. 2019

International Journal of Multiphase Flow

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This study is concerned with the statistics of vertical turbulent channel flow laden with inertial particles for two different volume concentrations (Φ V = 3 × 10 −6 and Φ V = 5 × 10 −5 ) at a Stokes number of St + = 58.6 based on viscous units. Two independent direct numerical simulation models utilizing the point-particle approach are compared to recent experimental measurements, where all relevant nondimensional parameters are directly matched. While both numerical models are built on the same general approach, details of the implementations are different, particularly regarding how two-way coupling is represented. At low volume loading, both numerical models are in general agreement with the experimental measurements, with certain exceptions near the walls for the wall-normal particle velocity fluctuations. At high loading, these discrepancies are increased, and it is found that particle clustering is overpredicted in the simulations as compared to the experimental observations. Potential reasons for the discrepancies are discussed. As this study is among the first to perform one-to-one comparisons of particle-laden flow statistics between numerical models and experiments, it suggests that continued efforts are required to reconcile differences between

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Turbulence attenuation in particle-laden flow in smooth and rough channels

Cited by 88 publications

References 58 publications

Particle-resolved direct numerical simulation of homogeneous isotropic turbulence modified by small fixed spheres

Particle-resolved direct numerical simulation of homogeneous isotropic turbulence modified by small fixed spheres

Point-Particle DNS and LES of Particle-Laden Turbulent flow - a state-of-the-art review

Inertial particle velocity and distribution in vertical turbulent channel flow: A numerical and experimental comparison

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