Effect of turbulence-driven secondary flow on particle preferential concentration and clustering in turbulent square duct flows--颗粒学报PARTICUOLOGY

Zhao, Y., Wang, Y., & Yao, J. (2021). Effect of turbulence-driven secondary flow on particle preferential concentration and clustering in turbulent square duct flows. Particuology, 55, 70-83. https://doi.org/10.1016/j.partic.2020.07.006

Effect of turbulence-driven secondary flow on particle preferential concentration and clustering in turbulent square duct flows

Yanlin Zhao, Yanzhi Wang, Jun Yao ^*

International Joint Laboratory on Clean Energy Science and Technology, Beijing Key Laboratory of Process Fluid Filtration and Separation, College of Mechanical and Transportation Engineering, China University of Petroleum-Beijing, Beijing 102249, China

10.1016/j.partic.2020.07.006

Volume 55, April 2021, Pages 70-83

Received 16 April 2020, Revised 8 June 2020, Accepted 8 July 2020, Available online 21 August 2020, Version of Record 3 February 2021.

E-mail: yaojun@cup.edu.cn

Highlights

• Preferential concentration and clustering of inertia particles in fully developed turbulent square duct flows are studied.

• Flow friction Reynolds number (Reτ = 600) and particle size 5–200 μm are considered.

• The inter-phase interaction considered includes one-way and two-way coupling.

• The mechanism responsible for particle preferential concentration in turbulent square duct flows is determined.

Abstract

In this study, the preferential concentration and clustering of inertial particles in fully developed turbulent square duct flows are studied using large eddy simulations combined with Lagrangian approach, where the Reynolds number is equal to Reτ = 600 (based on the mean friction velocity and duct full height), and the particle Stokes number ranges from 0.0007 to 1.16. The results obtained for duct flows are compared with those for channel flows under the same working conditions. Then, the effect of the secondary flow on the particle concentration in duct flows is investigated. The equation of particle motion is governed by the drag force, lift force, added mass force, pressure gradient force, and gravity. The inter-phase interaction that was considered includes one-way and two-way coupling. The simulations of a single phase are verified and in good agreement with the available literature data. For the discrete phase, particles in the duct flow are found to be more dispersed in the vertical direction compared with the channel flow. In near-wall regions, a small fraction of particles tends to accumulate in duct corners, forming stable particle streaks under the effect of the secondary flow. Meanwhile, most particles are likely to reside preferentially in the low-speed flow regions and form elongated particle streaks steadily in the middle region of duct or channel floors. The Voronoi diagram analysis shows that the near-wall secondary flows in the square duct could cause particle clusters to transfer from regions of high to low concentration, and this trend increases with particle size. In addition, two-way coupling is found to enhance the near-wall particle accumulation and to promote particles to form more elongated streaks than one-way coupling. Finally, the mechanism responsible for the particle preferential concentration in turbulent square duct flows is determined.

Graphical abstract

Keywords

Secondary flow; Preferential concentration; Turbulence; Particles; Square duct

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