Four-way coupled simulations of small particles in turbulent channel flow
File(s)
Accepted version
Published version
Author(s)
Van Wachem, B
Zhao, F
George, WK
Type
Journal Article
Abstract
This paper investigates the effects of particle shape and Stokes number on the behaviour
of non-spherical particles in turbulent channel flow. Although there are a number
of studies concerning spherical particles in turbulent flows, most important applications
occurring in process, energy, and pharmaceutical industries deal with nonspherical
particles. The computation employs a unique and novel four-way coupling
with the Lagrangian point-particle approach. The fluid phase at low Reynolds number
(Reτ = 150) is modelled by direct numerical simulation, while particles are tracked
individually. Inter-particle and particle-wall collisions are also taken into account.
To explore the effects of particles on the flow turbulence, the statistics of the fluid
flow such as the fluid velocity, the terms in the turbulence kinetic energy equation,
the slip velocity between the two phases and velocity correlations are analysed
considering ellipsoidal particles with different inertia and aspect ratio. The results
of the simulations show that the turbulence is considerably attenuated, even in the
very dilute regime. The reduction of the turbulence intensity is predominant near the
turbulence kinetic energy peak in the near wall region, where particles preferentially
accumulate. Moreover, the elongated shape of ellipsoids strengthens the turbulence
attenuation. In simulations with ellipsoidal particles, the fluid-particle interactions
strongly depend on the orientation of the ellipsoids. In the near wall region, ellipsoids
tend to align predominantly within the streamwise (x) and wall-normal (y) planes
and perpendicular to the span-wise direction, whereas no preferential orientation in
the central region of the channel is observed. Important conclusions from this work
include the effective viscosity of the flow is not affected, the direct dissipation by
the particles is negligible, and the primary mechanism by which the particles affect
the flow is by altering the turbulence structure around the turbulence kinetic energy
peak.
of non-spherical particles in turbulent channel flow. Although there are a number
of studies concerning spherical particles in turbulent flows, most important applications
occurring in process, energy, and pharmaceutical industries deal with nonspherical
particles. The computation employs a unique and novel four-way coupling
with the Lagrangian point-particle approach. The fluid phase at low Reynolds number
(Reτ = 150) is modelled by direct numerical simulation, while particles are tracked
individually. Inter-particle and particle-wall collisions are also taken into account.
To explore the effects of particles on the flow turbulence, the statistics of the fluid
flow such as the fluid velocity, the terms in the turbulence kinetic energy equation,
the slip velocity between the two phases and velocity correlations are analysed
considering ellipsoidal particles with different inertia and aspect ratio. The results
of the simulations show that the turbulence is considerably attenuated, even in the
very dilute regime. The reduction of the turbulence intensity is predominant near the
turbulence kinetic energy peak in the near wall region, where particles preferentially
accumulate. Moreover, the elongated shape of ellipsoids strengthens the turbulence
attenuation. In simulations with ellipsoidal particles, the fluid-particle interactions
strongly depend on the orientation of the ellipsoids. In the near wall region, ellipsoids
tend to align predominantly within the streamwise (x) and wall-normal (y) planes
and perpendicular to the span-wise direction, whereas no preferential orientation in
the central region of the channel is observed. Important conclusions from this work
include the effective viscosity of the flow is not affected, the direct dissipation by
the particles is negligible, and the primary mechanism by which the particles affect
the flow is by altering the turbulence structure around the turbulence kinetic energy
peak.
Date Issued
2015-08-03
Date Acceptance
2015-07-10
Citation
Physics of Fluids, 2015, 27 (8)
ISSN
1089-7666
Publisher
American Institute of Physics (AIP)
Journal / Book Title
Physics of Fluids
Volume
27
Issue
8
Copyright Statement
© 2015 AIP Publishing LLC
Publication Status
Published
Article Number
083301