Further observations on the rheological behaviour of dense suspensions
1984; Elsevier BV; Volume: 37; Issue: 1 Linguagem: Inglês
10.1016/0032-5910(84)80022-4
ISSN1873-328X
Autores Tópico(s)Electrostatics and Colloid Interactions
ResumoThe literature and recent WSL results on suspensions of spherical particles are surveyed and summarised. It is concluded that the steady shear properties of a dense suspension is not characterised by an unique viscosity or flow curve, but rather it is described by a wide viscosity distribution or a shear stress - shear rate flow band whose mean and standard deviation are functions of solids concentration, particle size distribution and viscometric geometry and dimensions. The standard deviation (or data spread) increases with solids concentration and with decreasing viscometer gap to particle diameter ratio. This property is due to poor sample reproducibility in respect of solids concentration and particle size distribution and the inherent two-phase nature of suspension which gives rise to particle migration and consequently non-uniform packing density or structure in a sample. Because a dense suspension is increasingly sensitive to these factors as concentration is increased, the standard deviation can be very large. Because the details of packing structure vary with flow, the viscosity distribution or flow band depends on viscometric flow geometry and measuring element dimensions. The implications of this conclusion on the study and characterisation of dense suspension property and the prediction of its behaviour in industrial handling and process equipment are discussed.
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