Experimental and numerical study of the rotation and the erosion of fillers suspended in viscoelastic fluids under simple shear flow

When a porous agglomerate immersed in a fluid is submitted to a shear flow, hydrodynamic stresses acting on its surface may cause a size reduction if they exceed the cohesive stress of the agglomerate. The aggregates forming the agglomerate are slowly removed from the agglomerate surface. Such a beh...

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Bibliographic Details
Published in:Rheologica acta 2003-09, Vol.42 (5), p.421-431
Main Authors: ASTRUC, Marianne, VERVOORT, Sylvie, NOUATIN, Hervé O, COUPEZ, Thierry, DE PUYDT, Yves, NAVARD, Patrick, PEUVREL-DISDIER, Edith
Format: Article
Language:English
Subjects:
Agglomerates
Agglomeration
Applied sciences
Axis movements
Carbon black
Compounding ingredients
Computational fluid dynamics
Computer simulation
Elasticity
Engineering Sciences
Erosion
Exact sciences and technology
Fillers
Fillers and reinforcing agents
Finite element method
Fluid flow
Fluids
Materials
Mathematical models
Polymer industry, paints, wood
Rotation
Shear flow
Size reduction
Technology of polymers
Viscoelastic fluids
Viscoelasticity
Vorticity
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Summary:When a porous agglomerate immersed in a fluid is submitted to a shear flow, hydrodynamic stresses acting on its surface may cause a size reduction if they exceed the cohesive stress of the agglomerate. The aggregates forming the agglomerate are slowly removed from the agglomerate surface. Such a behaviour is known when the suspending fluid is Newtonian but unknown if the fluid is viscoelastic. By using rheo-optical tools, model fluids, carbon black agglomerates and particles of various shapes, we found that the particles had a rotational motion around the vorticity axis with a period which is independent on shape (flat particles not considered), but which is exponentially increasing with the elasticity of the medium expressed by the Weissenberg number (We). Spherical particles are always rotating for We up to 2.6 (largest investigated We in this study) but elongated particles stop rotating for We>0.9 while orienting along the flow direction. Erosion is strongly reduced by elasticity. Since finite element numerical simulation shows that elasticity increases the local stress around a particle, the origin of the erosion reduction is interpreted as an increase of cohesiveness of the porous agglomerate due to the infiltration of a viscoelastic fluid.
ISSN:0035-4511
1435-1528
DOI:10.1007/s00397-003-0296-9