Dynamics of disk-like particles in turbulent vertical channel flow

Yuan, Wenjun; Andersson, Helge I.; Zhao, Lihao; Challabotla, Niranjan Reddy; Deng, Jianqiang

doi:10.1016/j.ijmultiphaseflow.2017.06.008

Cited by 22 publications

(16 citation statements)

References 60 publications

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“…(2015 c ) and Yuan et al. (2017) for oblate spheroids. The inertial spheroids are considered as individual point particles obeying the laws of classical, i.e.…”

Section: Mathematical Modelling and Methodologymentioning

confidence: 97%

“…The translational and rotational motion of rigid spheroidal particles in turbulent fluid flow is modelled in an Eulerian-Lagrangian approach, following the way paved by Zhang et al (2001), Mortensen et al (2008a,b), Marchioli et al (2010) and Zhao et al (2014) for prolate spheroids and more recently by Challabotla et al (2015c) and Yuan et al (2017) for oblate spheroids. The inertial spheroids are considered as individual point particles obeying the laws of classical, i.e.…”

Section: Mathematical Modelling and Methodologymentioning

confidence: 99%

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Mapping spheroid rotation modes in turbulent channel flow: effects of shear, turbulence and particle inertia

et al. 2019

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The rotational behaviour of non-spherical particles in turbulent channel flow is studied by Lagrangian tracking of spheroidal point particles in a directly simulated flow. The focus is on the complex rotation modes of the spheroidal particles, in which the back reaction on the flow field is ignored. This study is a sequel to the letter by Zhao et al. (Phys. Rev. Lett., vol. 115, 2015, 244501), in which only selected results in the near-wall buffer region and the almost-isotropic channel centre were presented. Now, particle dynamics all across the channel is explored to provide a complete picture of the orientational and rotational behaviour with consideration of the effects of particle aspect ratio ranging from 0.1 to 10 and particle Stokes number from 0 (inertialess) to 30. The rotational dynamics in the innermost part of the logarithmic wall layer is particularly complex and affected not only by modest mean shear, but also by particle inertia and turbulent vorticity. While inertial disks exhibit modest preferential orientation in either the wall-normal or cross-stream direction, inertial rods show neither preferential tumbling nor spinning. Examination of the co-variances between particle orientation, particle rotation and fluid rotation vectors explains the qualitatively different ‘wall mode’ rotation and ‘centre mode’ rotation. Inertialess spheroids transition between the two modes within a narrow zone ($15<z^{+}<35$) in the buffer region. If the spheroids have inertia, the transition zone between the two modes shifts to the inner part of the logarithmic layer, i.e. $z^{+}\geqslant 40$. We ascribe the transition of inertialess spheroids from the ‘wall mode’ to the ‘centre mode’ rotation to the changeover between the time scales associated with mean shear and small-scale turbulence. Inertial spheroids, however, transition between the two rotational modes when the Kolmogorov time scale becomes comparable to the time scale for particle rotation, i.e. the effective Stokes number is of order unity. The aforementioned findings reveal, in addition to the effects of particle shape and alignment, the importance of the characteristic local time scale of fluid flow for the rotation of both tracer and inertial spheroids in turbulent channel flows.

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“…(2015 c ) and Yuan et al. (2017) for oblate spheroids. The inertial spheroids are considered as individual point particles obeying the laws of classical, i.e.…”

Section: Mathematical Modelling and Methodologymentioning

confidence: 97%

Section: Mathematical Modelling and Methodologymentioning

confidence: 99%

Mapping spheroid rotation modes in turbulent channel flow: effects of shear, turbulence and particle inertia

et al. 2019

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“…The effect of gravity typically results in extra slip velocity and affects particle rotation and/or distribution. Nilsen et al (2013), Challabotla et al (2016) and Yuan et al (2017) presented direct numerical simulations of vertical channel flows, and suggested that the gravity effect affects particle orientation as well as particle distribution in the wall-normal direction. These studies focused only on particles with moderate inertia, but more recent studies (Ardekani et al 2017;Fornari et al 2016;Fornari et al 2018) have demonstrated that, counter to intuition, gravity has important effects on particles with small inertia.…”

Section: A C C E P T E D Mmentioning

confidence: 99%

“…Second-order explicit Adams-Bashforth scheme is adopted for the time advancement. The set-up of Eulerian numerical method for fluid phase is the same as those used by Challabotla et al (2016) and Yuan et al (2017).…”

Section: A Eulerian Fluid Dynamicsmentioning

confidence: 99%

Settling tracer spheroids in vertical turbulent channel flows

Qiu

Marchioli

Andersson

et al. 2019

International Journal of Multiphase Flow

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Highlights  Enhancement of settling velocity is observed for both oblate and prolate tracer spheroids in downward and upward flow.  Slip velocity originating from preferential orientation accounts for the major enhancement of settling velocity.  Particles' preferential sampling of high or low speed flow regions is the result of clustering and influences settling velocity.  Wall-normal distribution of particle is dominated by wall-normal slip velocity. Transport of particles in the wall-normal direction reaches a stable state when the velocity due to sampling and the slip velocity balance each other.

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“…Sardina et al (2012) studied turbophoresis in wall-turbulence using the particle pair correlation function and found that particles tend to accumulate in strongly directional and elongated flow structures. In recent years, preferential concentration in the near-wall region has been explored the effects of gravity (Nilsen et al 2013, Yuan et al 2017) and particle shape (Njobuenwu and Fairweather 2014, Rabencov and van Hout 2015, Yuan et al 2018, Zhao et al 2014. The role played by coherent flow structures for particle dispersion has been studied.…”

Section: Introductionmentioning

confidence: 99%

Effects of the quiescent core in turbulent channel flow on transport and clustering of inertial particles

Jie

Andersson

Zhao

2020

Preprint

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The existence of a quiescent core (QC) in the center of turbulent channel flows was demonstrated in recent experimental and numerical studies. The QC-region, which is characterized by relatively uniform velocity magnitude and weak turbulence levels, occupies about 40% of the cross-section at Reynolds numbers Re τ ranging from 1000 to 4000. The influence of the QC region and its boundaries on transport and accumulation of inertial particles has never been investigated before.Here, we first demonstrate that a QC is unidentifiable at Re τ = 180, before an in-depth exploration of particle-laden turbulent channel flow at Re τ = 600 is performed. The inertial spheres exhibited a tendency to accumulate preferentially in high-speed regions within the QC, i.e. contrary to the well-known concentration in low-speed streaks in the near-wall region. The particle wall-normal distribution, quantified by means of Voronoï volumes and particle number concentrations, varied abruptly across the QC-boundary and vortical flow structures appeared as void areas due to the centrifugal mechanism. The QC-boundary, characterized by a localized strong shear layer, appeared as a barrier, across which transport of inertial particles is hindered. Nevertheless, the statistics conditioned in QC-frame show that the mean velocity of particles outside of the QC was towards the core, whereas particles within the QC tended to migrate towards the wall. Such upward and downward particle motions are driven by similar motions of fluid parcels. The present results show that the QC exerts a substantial influence on transport and accumulation of inertial particles, which is of practical relevance in high-Reynolds number channel flow.

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Dynamics of disk-like particles in turbulent vertical channel flow

Cited by 22 publications

References 60 publications

Mapping spheroid rotation modes in turbulent channel flow: effects of shear, turbulence and particle inertia

Mapping spheroid rotation modes in turbulent channel flow: effects of shear, turbulence and particle inertia

Settling tracer spheroids in vertical turbulent channel flows

Effects of the quiescent core in turbulent channel flow on transport and clustering of inertial particles

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