BPCPPDYSOE21 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 14: Microfluidics and Droplets - organized by Uwe Thiele (Münster)
DY 14.5: Vortrag
Montag, 22. März 2021, 17:20–17:40, DYa
Anchoring-dependent flow bifurcation in nematic microflows within circular capillaries — •Paul Steffen1, Eric Stellamanns2, and Anupam Sengupta1 — 1Physics of Living Matter, Dept. of Physics and Materials Science, University of Luxembourg, Luxembourg — 2Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
Capillary microflows of liquid crystal (LC) phases are fundamental to biological and bio-inspired systems. Here we investigate stationary flows of nematic LC within circular capillaries under homeotropic (normal) and uniform planar anchoring conditions, using numerical simulations based on the continuum theory of Leslie, Ericksen and Parodi for the material parameters of 5CB, a single component flow-aligning nematic LC. Instead of the expected unique solution with a director field monotonously approaching the alignment angle for increasing Ericksen numbers, we report a second anomalous solution that emerges above a threshold flow rate, leading to an anchoring-dependent flow bifurcation. For homeotropic surface anchoring, the anomalous director field orients against the alignment angle in the vicinity of the pipe center; while in the uniform planar case, the anomalous director field extends throughout the capillary volume, leading to reduction of the flow speed for increasing pressure gradients. Experimental signatures of the second solutions in each case are found in authors's experimental results, reported previously in Phys. Rev. Lett. 110, 048303, 2013 (homeotropic) and Int. J. Mol. Sci. 14, 22826, 2013 (planar case).