Particle settling in a shear-thinning, viscoelastic fluid in the presence of wall effects
Abstract The settling of particles in fluids is a widespread phenomenon and commonly involves accounting for the effects of walls. Particle settling and wall effects are well understood for Newtonian fluids but the consequences of non-Newtonian fluid properties on particle settling are less well kno...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Nature Portfolio
2025-02-01
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| Series: | Scientific Reports |
| Online Access: | https://doi.org/10.1038/s41598-025-87742-w |
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| Summary: | Abstract The settling of particles in fluids is a widespread phenomenon and commonly involves accounting for the effects of walls. Particle settling and wall effects are well understood for Newtonian fluids but the consequences of non-Newtonian fluid properties on particle settling are less well known. Here, we present the results from a set of experiments quantifying wall effects on particle settling within quiescent shear-thinning and viscoelastic (non-Newtonian) fluids for sphere-to-tube diameter ratios $$\lambda \le 0.3$$ λ ≤ 0.3 . We find that wall effects on particle settling are reduced in non-Newtonian fluids and settling velocities are poorly predicted by conventional wall-corrected Stokes’ equations. We show that deviations in settling velocity are due to both the shear-thinning and viscoelastic properties of the fluid. Supported by our experimental dataset, we are able to show that calculating the shear-rate based on the particle diameter length-scale corresponds to an apparent viscosity that appropriately accounts for shear-thinning effects. A further correction factor for viscoelastic behaviour based on $$\lambda$$ λ and the Weissenberg number, Wi, is applied, and shows good agreement with all experimentally measured velocities. Together, we provide a quantitative method to accurately predict the terminal settling velocity of particles in shear-thinning, viscoelastic fluids up to sphere-to-tube diameter ratios of 0.3. |
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| ISSN: | 2045-2322 |