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Particle roughness and rheology in noncolloidal suspensions
- Source :
- Journal of Rheology. 60:809-818
- Publication Year :
- 2016
- Publisher :
- Society of Rheology, 2016.
-
Abstract
- We explore the effect of deliberately increased particle roughness on the rheology of noncolloidal suspensions of spheres, both in Newtonian (polydimethylsiloxane or silicone oil) and non-Newtonian (Boger fluid) matrices. The object of the experiment is to change only the roughness of the spheres, while leaving the density and the material of the particles unchanged, so as to isolate the effect of roughness on rheology. Two sphere materials, polystyrene (PS) and polymethylmethacrylate (PMMA) were used. The PS spheres were of 40 and 80 μm nominal diameters, and the PMMA spheres were 40 μm in diameter. Roughness ratios (average roughness/sphere radius) of 0.1%–5% were explored. With silicone matrices, there was up to 50% increase in viscosity with a 50% volume fraction suspension and an increase in the normal stress differences of a similar magnitude. Two polybutene-based Boger fluids were also used. The increases of viscosity with the polybutene matrices were somewhat larger than those with the Newtonian matrix; at 40% volume concentration, we saw approximately a 35% increase in viscosity with a roughness ratio of 5.3%. We compared the experimental results with computations for spheres in Newtonian matrices, and we found reasonable agreement with the computations of Mari et al. [J. Rheol. 58, 1693–1724 (2014)] if a friction coefficient of about 0.5 was assumed. We conclude that friction and roughness must be considered in computational work, or no agreement with experiment will be found. We suggest that the shear-thinning seen with Newtonian matrices is due to a lessening of friction with shear rate. We also show that the unexpected success of the Maron–Pierce formula for Newtonian suspensions is due to the fact that it mimics well a frictional suspension with a friction coefficient of ∼0.5.
- Subjects :
- Materials science
010304 chemical physics
Mechanical Engineering
Constant Viscosity Elastic (Boger) Fluids
Condensed Matter Physics
01 natural sciences
Non-Newtonian fluid
010305 fluids & plasmas
Physics::Fluid Dynamics
Shear rate
Viscosity
chemistry.chemical_compound
Rheology
chemistry
Mechanics of Materials
0103 physical sciences
Newtonian fluid
Particle
General Materials Science
Polybutene
Composite material
Subjects
Details
- ISSN :
- 15208516 and 01486055
- Volume :
- 60
- Database :
- OpenAIRE
- Journal :
- Journal of Rheology
- Accession number :
- edsair.doi...........0f73abef2e2ac89c09bb3c21a4295c03