TY - JOUR
T1 - Influence of Concentration on Sedimentation of a Dense Suspension in a Viscous Fluid
AU - Shajahan, Tariq
AU - Breugem, Wim Paul
PY - 2020
Y1 - 2020
N2 - Macroscopic properties of sedimenting suspensions have been studied extensively and can be characterized using the Galileo number (Ga), solid-to-fluid density ratio (πp) and mean solid volume concentration (ϕ¯). However, the particle–particle and particle–fluid interactions that dictate these macroscopic trends have been challenging to study. We examine the effect of concentration on the structure and dynamics of sedimenting suspensions by performing direct numerical simulation based on an Immersed Boundary Method of monodisperse sedimenting suspensions of spherical particles at fixed Ga= 144 , πp= 1.5 , and concentrations ranging from ϕ¯ = 0.5 to ϕ¯ = 30 %. The corresponding particle terminal Reynolds number for a single settling particle is ReT= 186. Our simulations reproduce the macroscopic trends observed in experiments and are in good agreement with semi-empirical correlations in literature. From our studies, we observe, first, a change in trend in the mean settling velocities, the dispersive time scales and the structural arrangement of particles in the sedimenting suspension at different concentrations, indicating a gradual transition from a dilute regime (ϕ¯ ≲ 2 %) to a dense regime (ϕ¯ ≳ 10 %). Second, we observe the vertical propagation of kinematic waves as fluctuations in the local horizontally-averaged concentration of the sedimenting suspension in the dense regime.
AB - Macroscopic properties of sedimenting suspensions have been studied extensively and can be characterized using the Galileo number (Ga), solid-to-fluid density ratio (πp) and mean solid volume concentration (ϕ¯). However, the particle–particle and particle–fluid interactions that dictate these macroscopic trends have been challenging to study. We examine the effect of concentration on the structure and dynamics of sedimenting suspensions by performing direct numerical simulation based on an Immersed Boundary Method of monodisperse sedimenting suspensions of spherical particles at fixed Ga= 144 , πp= 1.5 , and concentrations ranging from ϕ¯ = 0.5 to ϕ¯ = 30 %. The corresponding particle terminal Reynolds number for a single settling particle is ReT= 186. Our simulations reproduce the macroscopic trends observed in experiments and are in good agreement with semi-empirical correlations in literature. From our studies, we observe, first, a change in trend in the mean settling velocities, the dispersive time scales and the structural arrangement of particles in the sedimenting suspension at different concentrations, indicating a gradual transition from a dilute regime (ϕ¯ ≲ 2 %) to a dense regime (ϕ¯ ≳ 10 %). Second, we observe the vertical propagation of kinematic waves as fluctuations in the local horizontally-averaged concentration of the sedimenting suspension in the dense regime.
KW - Dense suspension
KW - Immersed boundary method
KW - Kinematic waves
KW - Sedimentation
UR - http://www.scopus.com/inward/record.url?scp=85086644228&partnerID=8YFLogxK
U2 - 10.1007/s10494-020-00172-8
DO - 10.1007/s10494-020-00172-8
M3 - Article
AN - SCOPUS:85086644228
VL - 105
SP - 537
EP - 554
JO - Flow, Turbulence and Combustion
JF - Flow, Turbulence and Combustion
SN - 1386-6184
IS - 2
ER -