The design of flow processes to build a macroscopic bulk material from rod-shaped colloidal particles has drawn considerable attention from researchers and engineers. Here, we systematically explore and show that the characteristic strain rate of the flow universally determines the orientational ordering of colloidal rods. We employed the fluctuating lattice Boltzmann method by simulating hydrodynamically interacting Brownian rods in a Newtonian liquid moving under various flow types. By modeling a rigid rod as a chain of nonoverlapping solid spheres with constraint forces and torque, we elucidate rigid rod dynamics with an aspect ratio () either 4.1 or 8.1 under various rotational Péclet number () conditions. The dynamics of colloidal rods in dilute () and semidilute suspensions () were simulated for a wide range of () under shear flows including Couette and Poiseuille flows in a planar channel geometry, and an extensional and mixed-kinematics flow in a periodic four-roll mill geometry, where is the number density, and and are the diameter and length of the rod, respectively. By evaluating the degree of orientational alignment of rods along the flows, we observed that there is no significant difference between flow types, and the flow-induced ordering of rods depends on the variation of up to moderate (). At a high (), the degree of orientational ordering is prone to diversify depending on the flow type. The spatial inhomogeneity of the strain-rate distribution leads to a substantial decrease in the orientational alignment at high .
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March 2023
Research Article|
March 01 2023
Universal flow-induced orientational ordering of colloidal rods in planar shear and extensional flows: Dilute and semidilute concentrations
Byoungjin Chun
;
Byoungjin Chun
Department of Chemical and Biological Engineering, Korea University
, Seoul 02841, Republic of Korea
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Hyun Wook Jung
Hyun Wook Jung
a)
Department of Chemical and Biological Engineering, Korea University
, Seoul 02841, Republic of Korea
a)Author to whom correspondence should be addressed; electronic mail: hwjung@grtrkr.korea.ac.kr
Search for other works by this author on:
a)Author to whom correspondence should be addressed; electronic mail: hwjung@grtrkr.korea.ac.kr
J. Rheol. 67, 315–330 (2023)
Article history
Received:
August 17 2022
Accepted:
December 14 2022
Citation
Byoungjin Chun, Hyun Wook Jung; Universal flow-induced orientational ordering of colloidal rods in planar shear and extensional flows: Dilute and semidilute concentrations. J. Rheol. 1 March 2023; 67 (2): 315–330. https://doi.org/10.1122/8.0000550
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