Flow Modulation by Finite-Size Neutrally Buoyant Particles in a Turbulent Channel Flow

Wang, Lian‐Ping; Peng, Cheng; Guo, Zhaoli; Yu, Zhaosheng

doi:10.1115/1.4031691

Cited by 42 publications

(39 citation statements)

References 63 publications

(107 reference statements)

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“…2015; Wang et al 2016;Yu et al 2016). This decrease of layering is attributed to the stronger mixing in this flow due to a higher Reynolds number.…”

Section: )mentioning

confidence: 99%

“…The previously mentioned challenges and limitations of experimental and theoretical approaches makes the use of advanced numerical tools a necessity for obtaining detailed information; despite the well-known limitations in terms of Reynolds numbers that can be reached in simulations (Prosperetti 2015). Lately, several groups have been successfully using numerical algorithms for interface-resolved direct numerical simulations (DNS) of different turbulent flows laden with finite size particles: examples are suspensions in isotropic turbulence (Ten Cate et al 2004;Lucci et al 2010), vertical channel flow (Uhlmann 2008), sedimentation (Chouippe & Uhlmann 2015;Fornari et al 2016b), bed load transport (Kidanemariam & Uhlmann 2014;Vowinckel et al 2014), channel transport of mono-dispersed particles (Wang et al 2016;Yu et al 2016;Wang et al 2017), and recently of poly-disperse (Lashgari et al 2017;Fornari et al 2018) and non-spherical particles (Ardekani et al 2017;Eshghinejadfard et al 2017). Likewise, the present work uses such simulations to study turbulent channel transport of neutrally-buoyant finite size spheres.…”

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confidence: 99%

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Effects of the finite particle size in turbulent wall-bounded flows of dense suspensions

et al. 2018

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We use interface-resolved numerical simulations to study finite-size effects in turbulent channel flow of neutrally-buoyant spheres. Two cases with particle sizes differing by a factor of 2, at the same solid volume fraction of 20% and bulk Reynolds number are considered. These are complemented with two reference single-phase flows: the unladen case, and the flow of a Newtonian fluid with the effective suspension viscosity of the same mixture in the laminar regime. As recently highlighted in Costa et al. (2016), a particle-wall layer is responsible for deviations of the mesoscale-averaged statistics from what is observed in the continuum limit where the suspension is modeled as a Newtonian fluid with (higher) effective viscosity. Here we investigate in detail the fluid and particle dynamics inside this layer and in the bulk. In the particle-wall layer, the near wall inhomogeneity has an influence on the suspension micro-structure over a distance proportional to the particle size. In this layer, particles have a significant (apparent) slip velocity that is reflected in the distribution of wall shear stresses. This is characterized by extreme events (both much higher and much lower than the mean). Based on these observations we provide a scaling for the particle-to-fluid apparent slip velocity as a function of the flow parameters. We also extend the scaling laws in Costa et al. (2016) to second-order Eulerian statistics in the homogeneous suspension region away from the wall. The results show that finite-size effects in the bulk of the channel become important for larger particles, while negligible for lower-order statistics and smaller particles. Finally, we study the particle dynamics along the wall-normal direction. Our results suggest that single-point dispersion is dominated by particle-turbulence (and not particle-particle) interactions, while differences in two-point dispersion and collisional dynamics are consistent with a picture of shear-driven interactions.

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“…2015; Wang et al 2016;Yu et al 2016). This decrease of layering is attributed to the stronger mixing in this flow due to a higher Reynolds number.…”

Section: )mentioning

confidence: 99%

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confidence: 99%

Effects of the finite particle size in turbulent wall-bounded flows of dense suspensions

et al. 2018

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“…These observations are in qualitatively agreement with the previous interphase-resolved DNS results on the turbulent channel flows. 27,28 The comparison between Figs. 10 and 17 shows that the particle RMS velocities are smaller than the fluid counterparts, which is also consistent with the results on the turbulent channel flow laden with the neutrally buoyant particles.…”

Section: Solid-phase Statisticsmentioning

confidence: 99%

“…In recent years, the interface-resolved direct numerical simulation methods have been used to probe the mechanisms in the interactions between the turbulence and the finite-size particles, in which the interface between the particles and fluids is resolved and all turbulent structures are resolved with the direct numerical simulation method. Such methods have been applied to the simulations of particle-laden isotropic homogeneous flows (e.g., Ten Cate et al, 16 Lucci et al, 17 Gao et al, 18 and Cisse et al 19 ), pipe flow, 20 vertical channel flows, 21,22 and horizontal channel flows (e.g., Pan and Banerjee, 23 Shao et al, 24 Kidanemariam et al, 25 Do-Quang et al, 26 Picano et al, 27 Wang et al 28 ), as well as the interactions between the turbulence and a fixed particle (e.g., Bagchi and Balachandar, 29 Burton and Eaton, 30 Naso and Prosperetti 31 ). The aim of the present work is to investigate the effects of the finite-size neutrally buoyant particles on the turbulent flows in a square duct with the interface-resolved DNS method, focusing on the mean and root-mean-square velocities and in particular the mean secondary flow.…”

Section: Introductionmentioning

confidence: 99%

Effects of finite-size neutrally buoyant particles on the turbulent flows in a square duct

Lin

Shao

et al. 2017

Physics of Fluids

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Interface-resolved direct numerical simulations of the particle-laden turbulent flows in a square duct are performed with a direct-forcing fictitious domain method. The effects of the finite-size particles on the mean and root-mean-square (RMS) velocities are investigated at the friction Reynolds number of 150 (based on the friction velocity and half duct width) and the particle volume fractions ranging from 0.78% to 7.07%. Our results show that the mean secondary flow is enhanced and its circulation center shifts closer to the center of the duct cross section when the particles are added. The reason for the particle effect on the mean secondary flow is analyzed by examining the terms in the mean streamwise vorticity equation. It is observed that the particles enhance the gradients of the secondary Reynolds normal stress difference and shear stress in the near-wall region near the corners, which we think is mainly responsible for the enhancement in the mean secondary flow. Under a prescribed driving pressure gradient, the presence of particles attenuates the bulk velocity and the turbulent intensity. All particle-induced effects are intensified with increasing particle volume fraction and decreasing particle size, if other parameters are fixed. In addition, the particles accumulate preferentially in the near-corner region. The effects of the type of the collision model (i.e., if friction and damping are included or not) on the results are found significant, but not so significant to bring about qualitatively different results.

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“…We are in the process of optimizing our simulation code so we can carry out a variety of simulations covering different flow and particle parameter regimes. Some additional results regarding the effect of particle size can be found in [55]. We are also exploring a possibility to use a cuboid mesh so that the mesh size in the wall normal direction is different from these in the other two periodic directions.…”

Section: Discussionmentioning

confidence: 95%

Lattice Boltzmann simulation of particle-laden turbulent channel flow

et al. 2016

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Highlights• We present the first LBM simulations of particle-laden turbulent channel flows.• The results of single-phase flow are in excellent agreement with benchmark data.• The LBM results of particle-laden flow are similar to finite-difference results.• The presence of particles is shown to significantly alter flow statistics.• The nature of flow modulation depends on spatial location relative to the walls. AbstractModulation of the carrier phase turbulence by finite-size solid particles is relevant to many industrial and environmental applications. Here we report particle-resolved simulations of a turbulent channel flow laden with finite-size solid particles. We discuss how the mesoscopic lattice Boltzmann method (LBM) can be applied to treat both the turbulent carrier flow and moving fluid-particle interfaces. To validate the LBM approach, we first simulate the single-phase turbulent channel flow at a frictional Reynolds number of 180. A non-uniform force field is designed to excite turbulent fluctuations. The resulting mean flow profiles and turbulence statistics were found to be in excellent agreement with the published data based on the Chebychev-spectral method. We also found that the statistics of the fully-developed turbulent channel flow are independent of the setting of some of the relaxation parameters in the LBM approach. We then consider a particle-laden turbulent channel flow under the same body force. The particles have the same density as the fluid. The particle diameter is 5% of the channel width and the average volume fraction is 7.09%. We found that the presence of the particles reduces the mean flow speed by 4.6%, implying that the fluid-particle system is more dissipative than the single-phase flow. The maximum local reduction of the mean flow speed is about 7.5%. The effects of the solid particles on the fluid r.m.s. velocity fluctuations are mixed: both reduction and augmentation are observed depending on the direction and spatial location relative to the channel walls. Overall, particles enhance the relative turbulence intensity in the near wall region and suppress the turbulence intensity in the center region. The particle concentration distribution across the channel is also complicated. We find that there is a dynamic equilibrium location resembling the Segŕe-Silberberg effect known for a laminar wall-bounded flows. Our LBM results were found to be in good agreement with results based on a finite-difference method with direct forcing to handle the moving solid particles. Additionally, phase-partitioned statistics are obtained and compared.

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Flow Modulation by Finite-Size Neutrally Buoyant Particles in a Turbulent Channel Flow

Cited by 42 publications

References 63 publications

Effects of the finite particle size in turbulent wall-bounded flows of dense suspensions

Effects of the finite particle size in turbulent wall-bounded flows of dense suspensions

Effects of finite-size neutrally buoyant particles on the turbulent flows in a square duct

Lattice Boltzmann simulation of particle-laden turbulent channel flow

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