TY - JOUR
T1 - Swapping trajectories
T2 - A new wall-induced cross-streamline particle migration mechanism in a dilute suspension of spheres
AU - Zurita-Gotor, M.
AU - Bławzdziewicz, J.
AU - Wajnryb, E.
N1 - Funding Information:
We would like to thank our reviewers for calling our attention to the experimental results by Zarraga & Leighton (2001), and for providing some alternative explanations of the swapping mechanism. We would also like to acknowledge helpful suggestions by David Leighton regarding description of the swapping mechanism in terms of the wall reflection of the stresslet, using equation (4.6) to evaluate the self-diffusion coefficient, and showing the asymptotic relation (4.7). This work was supported by NSF grant CTS-0348175 (M. Z. G. and E. W.), NASA grant NAG3-2704 (M. Z. G.), Junta de Andalucia grant EXC/2005/TEP-985 (M. Z. G.), and by Polish Ministry of Science and Higher Education grant N501 020 32/1994 (E. W.).
PY - 2007/12/10
Y1 - 2007/12/10
N2 - Binary encounters between spherical particles in shear flow are studied for a system bounded by a single planar wall or two parallel planar walls under creeping flow conditions. We show that wall proximity gives rise to a new class of binary trajectories resulting in cross-streamline migration of the particles. The spheres on these new trajectories do not pass each other (as they would in free space) but instead they swap their cross-streamline positions. To determine the significance of the wall-induced particle migration, we have evaluated the hydrodynamic self-diffusion coefficient associated with a sequence of uncorrelated particle displacements due to binary particle encounters. The results of our calculations quantitatively agree with the experimental value obtained by Zarraga & Leighton (Phys. Fluids, vol. 14, 2002, p. 2194) for the self-diffusivity in a dilute suspension of spheres undergoing shear flow in a Couette device. We thus show that the wall-induced cross-streamline particle migration is the source of the anomalously large self-diffusivity revealed by their experiments.
AB - Binary encounters between spherical particles in shear flow are studied for a system bounded by a single planar wall or two parallel planar walls under creeping flow conditions. We show that wall proximity gives rise to a new class of binary trajectories resulting in cross-streamline migration of the particles. The spheres on these new trajectories do not pass each other (as they would in free space) but instead they swap their cross-streamline positions. To determine the significance of the wall-induced particle migration, we have evaluated the hydrodynamic self-diffusion coefficient associated with a sequence of uncorrelated particle displacements due to binary particle encounters. The results of our calculations quantitatively agree with the experimental value obtained by Zarraga & Leighton (Phys. Fluids, vol. 14, 2002, p. 2194) for the self-diffusivity in a dilute suspension of spheres undergoing shear flow in a Couette device. We thus show that the wall-induced cross-streamline particle migration is the source of the anomalously large self-diffusivity revealed by their experiments.
UR - http://www.scopus.com/inward/record.url?scp=36348953088&partnerID=8YFLogxK
U2 - 10.1017/S0022112007008701
DO - 10.1017/S0022112007008701
M3 - Article
AN - SCOPUS:36348953088
SN - 0022-1120
VL - 592
SP - 447
EP - 469
JO - Journal of Fluid Mechanics
JF - Journal of Fluid Mechanics
ER -