SKM 2021 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 5: Poster Session III: Statistical Physics, Complex Fluids and Soft Matter
DY 5.3: Poster
Dienstag, 28. September 2021, 17:30–19:30, P
Depinning of confined colloidal dispersions under oscillatory shear — •Marcel Hülsberg and Sabine H.L. Klapp — ITP, Technische Universität Berlin, Germany
Strongly confined colloidal dispersions under shear exhibit a variety of dynamical phenomena, including a depinning transition similar to single particles that are driven over a periodic substrate potential [1].
Here, we investigate the depinning behavior of these systems under pure oscillatory shearing with shear rate γ(t) = γ0 cos(ω t), as it is a common scenario in rheological experiments [2].
The colloids’ depinning behavior is assessed from a microscopic level based on particle trajectories, which are obtained from overdamped Brownian Dynamics simulations. The numerical approach is complemented by an analytic one based on a single-particle model in the limit of weak driving.
Investigating a broad spectrum of shear rate amplitudes γ0 and frequencies ω, we observe complete pinning as well as temporary depinning behaviour. We discover that temporary depinning occurs for shear rate amplitudes above a frequency-dependent critical amplitude γ0crit(ω), for which we attain a functional expression. This allows us to identify the dominant system-intrinsic time scale that dictates the scaling behavior of γ0crit with driving frequency ω.
Finally, we discuss the connection between depinning and structural changes in the system.
[1] S. Gerloff and S.H.L. Klapp, Phys. Rev. E 94(6), 062605 (2016)
[2] J.M. Brader, et al., Phys. Rev. E 82(6), 061401 (2010)