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Updated: Jun 14, 2026

Visually Based Characterization of the Incipient Particle Motion in Regular Substrates: From Laminar to Turbulent Conditions
Published on: February 22, 2018
Direct measurement of shear-induced cross-correlations of Brownian motion
1Technische Physik, Universität des Saarlandes, 66041 Saarbrücken, Germany.
Abstract:
Shear-induced cross-correlations of particle fluctuations perpendicular and along streamlines are investigated experimentally and theoretically. Direct measurements of the Brownian motion of micron-sized beads, held by optical tweezers in a shear-flow cell, show a strong time asymmetry in the cross-correlation, which is caused by the non-normal amplification of fluctuations. Complementary measurements on the single particle probability distribution substantiate this behavior and both results are consistent with a Langevin model. In addition, a shear-induced anticorrelation between orthogonal random displacements of two trapped and hydrodynamically interacting particles is detected, having one or two extrema in time, depending on the positions of the particles.
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