Abstract
Suspension flows are ubiquitous in industry and nature. Therefore, it is important to understand the rheological properties of a suspension. The key to understanding the mechanism of suspension rheology is considering changes in its microstructure. It is difficult to evaluate the influence of change in the microstructure on the rheological properties affected by the macroscopic flow field for non-colloidal particles. In this study, we propose a new method to evaluate the changes in both the microstructure and rheological properties of a suspension using particle tracking velocimetry (PTV) and a power-law fluid model. Dilute suspension (0.38%) flows with fluorescent particles in a microchannel with a circular cross section were measured under low Reynolds number conditions (Re ≈ 10−4). Furthermore, the distribution of suspended particles in the radial direction was obtained from the measured images. Based on the power-law index and dependence of relative viscosity on the shear rate, we observed that the non-Newtonian properties of the suspension showed shear-thinning. This method will be useful in revealing the relationship between microstructural changes in a suspension and its rheology.
Highlights
IntroductionThe rheological properties of a suspension (solid particles dispersed in a fluid) vary depending on the particle volume fraction, particle shape, interactions between particles, spatial arrangement of particles, and nature of the solvent [1]
The rheological properties of a suspension vary depending on the particle volume fraction, particle shape, interactions between particles, spatial arrangement of particles, and nature of the solvent [1]
Choi et al [40] investigated the distributions of neutrally buoyant spherical particles suspended in a micro-scale pipe flow using a digital holography technique, which showed a qualitatively similar distribution when compared to our experimental results
Summary
The rheological properties of a suspension (solid particles dispersed in a fluid) vary depending on the particle volume fraction, particle shape, interactions between particles, spatial arrangement of particles, and nature of the solvent [1]. Suspension flows are ubiquitous in industry and nature. The rheology of suspension directly influences product quality such as food and paint [5]. Suspensions are important for industrial processes such as filtration [6] and ceramic processing [7,8], since they are the precursors to the manufacturing of numerous products. Understanding rheological properties of suspensions is expected to lead to control of suspension rheology and elucidation of hemorheology
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