Regensburg 2022 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 40: Brownian Motion and Anomalous Diffusion
DY 40.1: Vortrag
Donnerstag, 8. September 2022, 10:00–10:15, H20
Depinning and structural transitions 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, which is accompanied by lateral structural changes [1].
Here, we investigate the depinning behaviour 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 behaviour 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 an effective single-particle model in the limits of weak and strong 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 an approximate functional expression.
Above γ0crit(ω), we further observe a variety of dynamical structures, whose stability exhibits an intriguing (γ0, ω) dependency. This might enable new perspectives for potential control schemes.
[1] S. Gerloff and S.H.L. Klapp, Phys. Rev. E 94(6), 062605 (2016)
[2] S.M. Fielding, J. Rheol., 64(3), 723-738 (2020)