Abstract
The efficient transport of solid particles using polymeric fluids is an important step in many industrial operations. Different viscoelastic fluids have been designed for this purpose, however, the effects of elasticity have not been fully integrated in examining the particle-carrying capacity of the fluids. In this work, two elastic fluid formulations were employed to experimentally clarify the effect of elasticity on the particle drag coefficient as a proxy model for measuring carrying capacity. Fluids were designed to have a constant shear viscosity within a specific range of shear rates, , while possessing distinct (longest) relaxation times to investigate the influence of elasticity. It is shown that for dilute polymeric solutions, microfluidic rheometry must be practiced to obtain a reliable relaxation time (as one of the measures of viscoelasticity), which is on the order of milliseconds. A calibrated experimental setup, furnished with two advanced particle velocity measurement techniques and spheres with different characteristics, was used to quantify the effect of elasticity on the drag coefficient. These experiments led to a unique dataset in moderate levels of Weissenberg numbers, . The data showed that there is a subtle reduction in the drag coefficient at low levels of elasticity (), and a considerable enhancement at high levels of elasticity (). The experimental results were then compared with direct numerical simulation predictions yielding . These evaluations endorse the numerically quantified behaviors for the drag coefficient to be used to compare the particle-carrying capacity of different polymeric fluids under different flow conditions.
Highlights
The dynamics of solid particles flowing through polymeric fluids is strongly affected by viscoelasticity of the fluid [1,2]
First, the theoretical background is briefly reviewed for the particle dynamics and rheology measurements to accurately determine the parameters required to infer the drag coefficient
The working principle of the μ-rheometer is based on the transverse migration of solid particles occurring when the suspending viscoelastic fluid flows under an inertia-less Poiseuille flow through a confined straight microchannel
Summary
The dynamics of solid particles flowing through polymeric fluids is strongly affected by viscoelasticity of the fluid [1,2]. Several researchers [1,23,29,30,31,32] conducted comprehensive experimental and numerical investigations to determine the effect of fluid elasticity on the terminal velocity of a single sphere settling in a non-Newtonian elastic fluid in order to quantify the drag coefficient These studies, even though they, in some cases, provided contradictory conclusions [11,33], generally showed that the fluid elasticity hinders the particles’ motion, and the effect is more pronounced at a high level of elasticity [2,23]. The current study is undertaken to fulfill two main goals: (i) outline an appropriate scheme to infer the particle-carrying capacity of polymeric fluids, and (ii) generate unique static settling, or drag coefficient, data in moderate levels of elasticity To this end, first, the theoretical background is briefly reviewed for the particle dynamics and rheology measurements (e.g., conventional and microfluidic rheometry) to accurately determine the parameters required to infer the drag coefficient.
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