The effect of wall-normal gravity on particle-laden near-wall turbulence

Junghoon Lee, Chang Hoon Lee

Research output: Contribution to journalArticle

Abstract

We performed two-way coupled direct numerical simulations of turbulent channel flow with Lagrangian tracking of small, heavy spheres at a dimensionless gravitational acceleration of 0.077 in wall units, which is based on the flow condition in the experiment by Gerashchenko et al. (J. Fluid Mech., vol. 617, 2008, pp. 255-281). We removed deposited particles after several collisions with the lower wall and then released new particles near the upper wall to observe direct interactions between particles and coherent structures of near-wall turbulence during gravitational settling through the mean shear. The results indicate that when the Stokes number is approximately 1 on the basis of the Kolmogorov time scale of the flow (), the so-called preferential sweeping occurs in association with coherent streamwise vortices, while the effect of crossing trajectories becomes significant for 1$]]>. Consequently, in either case, the settling particles deposit on the wall without strong accumulation in low-speed streaks in the viscous sublayer. When particles settle through near-wall turbulence from the upper wall, more small-scale vortical structures are generated in the outer layer as low-speed fluid is pulled farther in the direction of gravity, while the opposite is true near the lower wall.

Original languageEnglish
Pages (from-to)475-507
Number of pages33
JournalJournal of Fluid Mechanics
DOIs
Publication statusPublished - 2019 Jan 1

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Gravitation
Turbulence
turbulence
gravitation
Fluids
Particle interactions
Direct numerical simulation
Channel flow
Vortex flow
Deposits
Trajectories
settling
low speed
Experiments
fluids
channel flow
direct numerical simulation
deposits
trajectories
vortices

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

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The effect of wall-normal gravity on particle-laden near-wall turbulence. / Lee, Junghoon; Lee, Chang Hoon.

In: Journal of Fluid Mechanics, 01.01.2019, p. 475-507.

Research output: Contribution to journalArticle

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