Turbulent-like flows in quasi two-dimensional dense suspensions of motile colloids
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| Format: | Preprint |
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2025
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| _version_ | 1866915167521996800 |
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| author | Luo, Rui Snezhko, Alexey Vlahovska, Petia M. |
| author_facet | Luo, Rui Snezhko, Alexey Vlahovska, Petia M. |
| contents | Dense bacterial suspensions exhibit turbulent-like flows at low Reynolds numbers, driven by the activity of the microswimmers. In this study, we develop a model system to examine these dynamics using motile colloids that mimic bacterial locomotion. The colloids are powered by the Quincke instability, which causes them to spontaneously roll in a random-walk pattern when exposed to a square-wave electric field. We experimentally investigate the flow dynamics in dense suspensions of these Quincke random walkers under quasi two-dimensional conditions, where the particle size is comparable to the gap between the electrodes. Our results reveal an energy spectrum scaling at high wavenumbers as $ \sim k^{-4}$, which holds across a broad range of activity levels -- controlled by the field strength -- and particle concentrations. We observe that velocity time correlations decay within a single period of the square-wave field, yet an anti-correlation appears between successive field applications, indicative of a dynamic structural memory of the ensemble. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2502_16381 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Turbulent-like flows in quasi two-dimensional dense suspensions of motile colloids Luo, Rui Snezhko, Alexey Vlahovska, Petia M. Fluid Dynamics Soft Condensed Matter Dense bacterial suspensions exhibit turbulent-like flows at low Reynolds numbers, driven by the activity of the microswimmers. In this study, we develop a model system to examine these dynamics using motile colloids that mimic bacterial locomotion. The colloids are powered by the Quincke instability, which causes them to spontaneously roll in a random-walk pattern when exposed to a square-wave electric field. We experimentally investigate the flow dynamics in dense suspensions of these Quincke random walkers under quasi two-dimensional conditions, where the particle size is comparable to the gap between the electrodes. Our results reveal an energy spectrum scaling at high wavenumbers as $ \sim k^{-4}$, which holds across a broad range of activity levels -- controlled by the field strength -- and particle concentrations. We observe that velocity time correlations decay within a single period of the square-wave field, yet an anti-correlation appears between successive field applications, indicative of a dynamic structural memory of the ensemble. |
| title | Turbulent-like flows in quasi two-dimensional dense suspensions of motile colloids |
| topic | Fluid Dynamics Soft Condensed Matter |
| url | https://arxiv.org/abs/2502.16381 |