Rheological behavior of a concentrated suspension: A solid rocket fuel simulant

Abstract

The rheological behavior of a very concentrated suspension (76.5 vol %), which serves as a widely used solid rocket fuel simulant, was characterized employing both torsional and capillary flows. No comprehensive studies of the rheology of concentrated suspensions have been carried out previously at such a high solids content. The suspension exhibited shear thinning over the apparent shear rate range of 3&3000 SC'. Significant slip at the wall was observed in both torsional and capillary flows with the slip velocity increasing from about 0.001 mm/s at a shear stress of 4 Pa to as high as 60 mm/s at 100 kPa. A flow visualization technique was applied for the first time to determine the wall slip velocities in torsional flow directly, to also provide the true deformation rate and feedback on yielding. The contribution of the slip of the suspension at the wall to the volumetric flow rate in capillary flow was found to increase with decreasing shear stress, giving rise to plug flow at sufficiently low shear stress values. The observed plug flow is related to the shear-thinning nature of the suspension and differs from the behavior of shear thickening suspensions, which may exhibit plug flow at high wall shear stress values, i.e., above a critical wall shear stress in capillary flow.

Effect of colloidal aggregation on the sedimentation and rheological properties of tank waste

“…Many empirical expressions have been developed to fit the viscometric data of non-Newtonian fluids. Models for pseudoplastic fluids include the power law or Ostwald-DeWaele (Bird et al 1960), Cross (1965), Caneau (Ellwood et al 1990), and Biviscous (Kalyon et al 1993) expressions. Models for viscoelastic materials include the Bingham plastic (Bird et al 1960), Casson (Bird et al 1983), Herschel-Bulkley (Bird et al 1983), and Gay @ab& and Yucel 1987) expressions.…”

Startup Flow of Gelled Crude Oils: An Experimental Study

“…One of these signatures is the dependence of rheological properties, like viscosity, on flow geometry such as a gap width in parallel plate rheometers or shape and radius of capillaries [76,24,61,79,71,63,8,52,109,25,95,4,131,97,14,83].…”

“…There are number of mechanisms proposed to explain slip in certain circumstances [75]. One of these mechanisms is the depletion of boundary layer where particles in a sheared dispersed system, such as emulsions and suspensions, migrate away from the boundary region resulting in a very thin low viscosity layer adjacent to the wall which acts as a lubricating film that facilitates fluid movement [8,29,4,76,13,72,112,117,63,3,25,31,57,108,50,126,5].…”

“…In the literature of rheology and fluid mechanics, wall slip is divided into 'true slip' where there is an adhesive failure at the interface, and 'apparent slip' where there is an inhomogeneous thin layer of fluid adjacent to the wall with different rheological properties to the bulk of fluid which facilitates fluid movement [64,75,70,134,23,15,52,135,3,63,57]. The 'apparent slip' designation comes from the fact that large velocity gradients across the very thin low-viscosity slip layer give an impression of slip at wall although the nonslip condition is not violated [62,31,8].…”

“…The 'apparent slip' designation comes from the fact that large velocity gradients across the very thin low-viscosity slip layer give an impression of slip at wall although the nonslip condition is not violated [62,31,8]. Generally, the apparent slip becomes more pronounced as the viscosity of the slip layer relative to the viscosity of bulk of fluid decreases [63].…”