Sun, 27 Jul 2008 09:18:33 BST CiteULike: weeks's migration http://www.citeulike.org/user/weeks/tag/migration CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/weeks/article/2940584 <i>J. Rheology, Vol. 52 (2008), pp. 141-164.</i><br /><br />The isotropic contribution of the particle phase to the bulk stress, or the particle pressure, is studied for Brownian hard sphere suspensions in computationally simulated shear flow. The particle pressure is mechanically defined as the negative mean normal stress exerted by the particles, i.e., Π=-(1/3)[Σ₁₁+Σ₂₂+Σ₃₃] for a viscometric flow where 1, 2, and 3 refer to the flow, velocity gradient, and vorticity directions, respectively. Analysis is provided to relate the particle pressure to the equilibrium osmotic pressure and to show the relation of Π to particle migration phenomena. Utilizing existing hydrodynamic functions and simulating the flow by the Stokesian Dynamics technique, the particle pressure is evaluated for particle volume fractions in the range 0.1<=[lowercase_phi_synonym]<=0.52 for monodisperse spherical particles. The relative strength of Brownian to shearing motion is given by the Péclet number Pe=γa²/D₀, where γ is the shear rate of a simple shear flow, a is the spherical particle radius, and D₀=kT/6πηa with kT the thermal energy and η the suspending fluid viscosity. For each [lowercase_phi_synonym], the range 0.1<=Pe<=1000 has been studied. The particle pressure at Pe=0.1, where it is given predominantly by a Brownian contribution, is found to approach the exact results for the osmotic pressure of an equilibrium hard-sphere dispersion, Π=nkT[1+4[lowercase_phi_synonym]g(2a)], where n is the particle number density and g(2a) is the pair distribution function evaluated at contact. The hydrodynamic contribution to Π grows with Pe and dominates the Brownian contribution at Pe>10. The particle pressure scales as ηγ at elevated Pe. The relative contributions to Π of Brownian and hydrodynamic stress are similar as a function of Pe to the normal stress differences of the suspension. Particle pressure in sheared Brownian suspensions Yevgeny Yurkovetsky Jeffrey Morris J. Rheology, Vol. 52 (2008), pp. 141-164. 2008-06-29T00:34:22-00:00 2008 J. Rheology 52 141 164 migration theory http://www.citeulike.org/user/weeks/article/2909042 <i>Journal of Non-Newtonian Fluid Mechanics, Vol. 135, No. 2-3. (30 May 2006), pp. 149-165.</i><br /><br />Pressure-driven flow of a noncolloidal suspension is studied in two-dimensional channel and axisymmetric circular pipe geometries at bulk solids fractions of 0.2<=[phi]<=0.5. Flows are modeled by the "suspension balance" approach, consisting of mass and momentum balances for the bulk suspension and particle phase. For particles in Newtonian fluid, cross-stream motion is driven by spatial variation of particle phase normal stresses. The particle phase stress model is based strictly upon the computed rate of strain, with a nonlocal contribution to the normal stress. Two solution procedures for the suspension flow equations are described. The first is a "solve-evolve" scheme based upon a full two-dimensional solution of the unsteady, axially varying behavior using a conservative finite volume method to solve the bulk mass and momentum conservation equations. The flow solution is coupled to an explicit update (evolve) step of the particle conservation equation. The second is a nonconservative but efficient marching solution for the asymptotically steady, but axially varying, problem. Predicted axial variation of the particle fraction, velocity and pressure gradient, as well as the fully developed profiles in channel and pipe flows are presented. The rate of axial development is strongly dependent upon the ratio of particle size to channel half-width (or pipe radius), [var epsilon][reverse not equivalent]a/B (or a/R). The agreement of marching method and full model solutions is very close for the cases studied; both agree quantitatively well with available experimental results, including axial development in the pipe flow, where the model predicts the second normal stress difference to influence the migration. Migration in a 2:1 contraction flow provides an illustration of a flow where the full solution is required. Normal stress-driven migration and axial development in pressure-driven flow of concentrated suspensions Ryan Miller Jeffrey Morris doi:10.1016/j.jnnfm.2005.11.009 Journal of Non-Newtonian Fluid Mechanics, Vol. 135, No. 2-3. (30 May 2006), pp. 149-165. 2008-06-19T23:05:41-00:00 2006 Journal of Non-Newtonian Fluid Mechanics 135 2-3 149 165 migration theory http://www.citeulike.org/user/weeks/article/2721820 <i>Physics of Fluids, Vol. 20, No. 4. (2008)</i> Shear-induced particle migration in binary colloidal suspensions Denis Semwogerere Eric Weeks Physics of Fluids, Vol. 20, No. 4. (2008) 2008-04-26T14:00:44-00:00 2008 Physics of Fluids 20 4 AIP binary brownian-motion migration http://www.citeulike.org/user/weeks/article/2560646 <i>Physics of Fluids, Vol. 14, No. 7. (2002), pp. 2194-2201.</i><br /><br />View This Record in Scopus Measurement of an unexpectedly large shear-induced self-diffusivity in a dilute suspension of spheres Isidro Zarraga Jr Physics of Fluids, Vol. 14, No. 7. (2002), pp. 2194-2201. 2008-03-19T13:24:13-00:00 2002 Physics of Fluids 14 7 2194 2201 AIP migration http://www.citeulike.org/user/weeks/article/1676507 <i>J. Fluid Mech., Vol. 581 (2007), pp. 437-451.</i> Development of particle migration in pressure-driven flow of a Brownian suspension D Semwogerere JF Morris ER Weeks J. Fluid Mech., Vol. 581 (2007), pp. 437-451. 2007-09-19T16:15:32-00:00 2007 J. Fluid Mech. 581 437 451 brownian-motion colloids confocal migration http://www.citeulike.org/user/weeks/article/1676506 <i>J. Fluid Mech, Vol. 181 (1987)</i> The shear-induced migration of particles in concentrated suspensions DT Leighton A Acrivos J. Fluid Mech, Vol. 181 (1987) 2007-09-19T16:15:32-00:00 1987 J. Fluid Mech 181 migration http://www.citeulike.org/user/weeks/article/1676505 <i>J. Fluid Mech, Vol. 493 (2003), pp. 363-378.</i> Particle migration in pressure-driven flow of a Brownian suspension M Frank D Anderson ER Weeks JF Morris J. Fluid Mech, Vol. 493 (2003), pp. 363-378. 2007-09-19T16:15:32-00:00 2003 J. Fluid Mech 493 363 378 brownian-motion colloids confocal migration pmma