77th Annual Meeting of the APS Division of Fluid Dynamics (November 24, 2024 — November 26, 2024)

V2691002: Separation of Bidisperse Particles in Viscous Thin-Film Flow Down an Incline

Authors

• Sarah Burnett, University of California, Los Angeles
• Qitong Luan, University of California, Los Angeles
• Scott Bloom, University of California, Los Angeles
• Lingyun Ding, University of California, Los Angeles
• Andrea L. Bertozzi, University of California, Los Angeles

DOI: https://doi.org/10.1103/APS.DFD.2024.GFM.V2691002

We present experiments on particle-oil mixtures to examine the separation of negatively buoyant spherical particles based on their size. In these videos, the larger particles are colored red, while the smaller particles are colored blue. When the particles settle in a column, Stokes' law dictates that the larger particles settle faster than the smaller ones. In a cup experiment, a well-mixed slurry allowed to settle over time results in a layer of smaller particles on top. In experiments where a well-mixed slurry is poured down an incline, the fluid forms a thin film down the surface. As the experiment progresses, a noticeable separation occurs, with the larger particles appearing at the top in the vertical direction, perpendicular to the incline. Smaller particles settle out upstream, while larger particles remain in suspension and ultimately aggregate at the front of the fluid.