A Eulerian—Lagrangian model has been developed to simulate particle attachment to surfaces with arc-shaped ribs in a two-dimensional channel flow at low Reynolds numbers. Numerical simulation has been performed to improve the quantitative understanding of how rib geometries enhance shear rates and particle-surface interact for various particle sizes and flow velocities. The enhanced shear rate is attributed to the wavy flows that develop over the ribbed surface and the weak vortices that form between adjacent ribs. Varying pitch-to-height ratio can alter the amplitude of the wavy flow and the angle of attack of the fluid on the ribs. In the presence of these two competing factors, the rib geometry with a pitch-to-height ratio of two demonstrates the greatest shear rate and the lowest fraction of particle attachment. However, the ribbed surfaces have negligible effects on small particles at low velocities. A force analysis identifies a threshold shear rate to reduce particle attachment. The simulated particle distributions over the ribbed surfaces are highly non-uniform for larger particles at higher velocities. The understanding of the effect of surface topography on particle attachment will benefit the design of surface textures for mitigating particulate fouling in a wide range of applications.
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Virtual Experiments of Particle Mixing Process with the SPH-DEM Model
Particle mixing process is critical for the design and quality control of concrete and composite production. This paper develops an algorithm to simulate the high-shear mixing process of a granular flow containing a high proportion of solid particles mixed in a liquid. DEM is employed to simulate solid particle interactions; whereas SPH is implemented to simulate the liquid particles. The two-way coupling force between SPH and DEM particles is used to evaluate the solid-liquid interaction of a multi-phase flow. Using Darcy’s Law, this paper evaluates the coupling force as a function of local mixture porosity. After the model is verified by two benchmark case studies, i.e., a solid particle moving in a liquid and fluid flowing through a porous medium, this method is applied to a high shear mixing problem of two types of solid particles mixed in a viscous liquid by a four-bladed mixer. A homogeneity metric is introduced to characterize the mixing quality of the particulate mixture. The virtual experiments with the present algorithm show that adding more liquid or increasing liquid viscosity slows down the mixing process for a high solid load mix. Although the solid particles can be mixed well eventually, the liquid distribution is not homogeneous, especially when the viscosity of liquid is low. The present SPH-DEM model is versatile and suitable for virtual experiments of particle mixing process with different blades, solid particle densities and sizes, and liquid binders, and thus can expedite the design and development of concrete materials and particulate composites.
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- NSF-PAR ID:
- 10276150
- Date Published:
- Journal Name:
- Materials
- Volume:
- 14
- Issue:
- 9
- ISSN:
- 1996-1944
- Page Range / eLocation ID:
- 2199
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/ma14092199
