Abstract
Rheological properties of the suspension flow, especially effective viscosity, partly depend on spatial arrangement and motion of suspended particles. It is important to consider effective viscosity from the microscopic point of view. For elliptical particles, the equilibrium position of inertial migration in confined state is unclear, and there are few studies on the relationship between dynamics of suspended particles and induced local effective viscosity distribution. Contribution of a single circular or elliptical particle flowing between parallel plates to the effective viscosity was studied, focusing on the particle–wall distance and particle rotational motion using the two-dimensional regularized lattice Boltzmann method and virtual flux method. As a result, confinement effects of the elliptical particle on the equilibrium position of inertial migration were summarized using three definitions of confinement. In addition, the effects of particle shape (aspect ratio and confinement) on the effective viscosity were assessed focusing on the particle–wall distance. The contribution of particle shape to the effective viscosity was found to be enhanced when the particle flowed near the wall. Focusing on the spatial and temporal variation of relative viscosity evaluated from wall shear stress, it was found that the spatial variation of the local relative viscosity was larger than temporal variation regardless of the aspect ratio and particle–wall distance.
Highlights
Suspension flows are ubiquitous in industrial process such as filtration, cosmetics, and food processing and in nature such as mud and blood flow
Rheological properties of a suspension flow partly depend on its microstructure, which refers to spatial arrangement and orientation of suspended particles [1]
The effects of periodic length, which refers to the length L of the parallel plates model, on the equilibrium position of inertial migration were assessed, and a grid independence study was conducted
Summary
Suspension flows are ubiquitous in industrial process such as filtration, cosmetics, and food processing and in nature such as mud and blood flow. In a channel flow, suspended particles migrate transversal to the streamlines and converge at the equilibrium position due to inertial effects. We have observed that the microstructure of a suspension changes in time mainly due to inertial effects of the suspended particles [3] Such inertial effects might be significant in practical cases, such as industrial flow or blood flow; it is important to consider inertial migration. Wen et al [5] numerically investigated the inertial migration of the elliptical particle, and they showed that the equilibrium position of the elliptical particle changes with aspect ratio. The equilibrium position of inertial migration was investigated for various aspect ratios by introducing three definitions of confinement for elliptical particles. These three definitions of confinement effects are discussed in this study
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