Particle migration in a Couette apparatus: Experiment and modeling
- Los Alamos National Laboratories, Los Alamos, New Mexico 87545 (United States)
- Department of Mechanical Engineering, University of New Mexico, Albuquerque, New Mexico 87131 (United States)
- Sandia National Laboratories, Albuquerque, New Mexico 87185-0834 (United States)
- New Mexico Resonance, 2425 Ridgecrest Drive, S. E., Albuquerque, New Mexico 87108 (United States)
Suspensions comprised of neutrally buoyant spheres in Newtonian fluids undergoing creeping flow in the annular region between two rotating, coaxial cylinders (a wide-gap Couette) display a bulk migration of particles towards regions of lower shear rate. A series of experiments are performed to characterize this particle migration, including the influence of particle size, surface roughness, and volume fraction. Little, if any, effect of particle surface roughness is observed. An existing continuum diffusive-flux model [Phillips {ital et al.} (1992)] for predicting particle concentration profiles in monomodal suspensions is evaluated using the current series of experimental data. This model predicts a dependence of the migration rate on the square of the suspended particles` radius, a{sup 2}; whereas the present experiments indicate that systems with average particle volume fractions of 50{percent} display a rate that scales with a{sup 3}. Previous use of the diffusive-flux model has assumed constant values for diffusion coefficients which serve as tuning parameters in the phenomenological equation. Here the experimental data are used to investigate variations of the model in which the diffusion coefficients depend upon either the local or global particle volume fraction. For initially uniform suspensions, the coefficients are found to be best modeled as functions of the local particle volume fraction. {copyright} {ital 1998 Society of Rheology.}
- Research Organization:
- Sandia National Laboratory
- DOE Contract Number:
- AC04-94AL85000; FG22-94PC94248; W-7405-ENG-36
- OSTI ID:
- 578068
- Journal Information:
- Journal of Rheology, Journal Name: Journal of Rheology Journal Issue: 2 Vol. 42; ISSN 0148-6055; ISSN JORHD2
- Country of Publication:
- United States
- Language:
- English
Similar Records
Particle migration rates in a Couette apparatus.
A constitutive equation for concentrated suspensions that accounts for shear-induced particle migration