A Two-Fluid Model for Highly Concentrated Suspension Flow Through Narrow Tubes and Slits: Velocity Profiles, Apparent Fluidity and Wall Layer Thickness
Viscometric flows of highly concentrated suspensions in narrow slits and pipes exhibit a two phase structure if the particle size cannot be considered as infinitesimally small in comparison with the transverse dimension of the vessel. In pipes this leads to a Well-known1,2 annular structure with a particle rich axial core surrounded by a particle depleted wall layer. The former results in a blunted velocity profile and in a reduced mean concentration in the tube, compared to the feed reservoir concentration1. The latter works as a lubricant layer which lowers the apparent viscosity, hence, which decreases extensively the viscous energy loss, even if this layer is very thin, as it was usually observed with highly concentrated suspensions.
KeywordsShear Rate Wall Shear Stress Wall Layer Concentrate Suspension Narrow Slit
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