Direct numerical simulation of particle-laden flow in an open channel at

Abstract

We perform two-way coupled direct numerical simulation of particle-laden flow in an open channel at a friction Reynolds number ( $Re_{\tau }$ ) of 5186, which exhibits many characteristics of high-Reynolds-number wall-bounded turbulence, such as the distinct separation of scales in the inner and outer layers. Three representative cases, an unladen case and low- and high-Stokes-number particle-laden cases, are performed to investigate the turbulent modification by particles. To this end, we compare several statistical quantities to understand the particle effect on momentum exchange and interphasial energy transfer. The modulation of large-scale motions (LSMs) and very-large-scale motions (VLSMs) are analysed using spectral information, and we find that the LSMs and VLSMs are generally weakened in the inner and outer layers, which is qualitatively different from similar simulations at lower Reynolds numbers ( $Re_{\tau } \approx 500$ ). The spatial structures are investigated with correlation analysis, and inclined VLSMs are observed in the near-wall region, with decreased inclination angles by particles. The particles tend to widen and shorten the spanwise and streamwise extent of coherent structures, respectively. Furthermore, we find that the vorticity vector displays a preferential alignment with the eigenvector corresponding to the intermediate eigenvalue of the strain-rate tensor, independent of the particle Stokes number.

How electrostatic forces affect particle behaviour in turbulent channel flows

“…2022; Motoori et al. 2022; Gao, Samtaney & Richter 2023). Detailed information on the selection of such a computational domain can be found in Gao et al.…”

“…Detailed information on the selection of such a computational domain can be found in Gao et al. (2023). A total of grid points are used to discretize the computational domain.…”

“…The simulations to be discussed in the present study are performed at Re τ = 550. The computational domain is set as 2πδ × 2δ × πδ, which is large enough to capture accurately particle behaviours even at Re τ from 1000 to 5186 (Jie et al 2022;Motoori et al 2022;Gao, Samtaney & Richter 2023). Detailed information on the selection of such a computational domain can be found in Gao et al (2023).…”

“…The computational domain is set as 2πδ × 2δ × πδ, which is large enough to capture accurately particle behaviours even at Re τ from 1000 to 5186 (Jie et al 2022;Motoori et al 2022;Gao, Samtaney & Richter 2023). Detailed information on the selection of such a computational domain can be found in Gao et al (2023). A total of 384 × 384 × 256 grid points are used to discretize the computational domain.…”

Dynamics and scaling of particle streaks in high-Reynolds-number turbulent boundary layers

“…As a result, the particle-turbulence interaction of low-Reynolds-number flows may not be representative of large-scale phenomena observed in the ASL. The few numerical investigations of particle-laden wall turbulence reaching Re τ = O(10 3 ) (Sardina et al 2012;Bernardini 2014;Li, Luo & Fan 2017;Wang & Richter 2020;Jie et al 2022;Motoori et al 2022;Gao, Samtaney & Richter 2023;Motoori & Goto 2023) used the point-particle approach, and neglected gravity. While the latter may appear as a reasonable assumption when the particle fall speed is much smaller than the advection velocity, gravity was shown to crucially change the dynamics even for particles of small inertia.…”