Tumbling of a rigid rod in a shear flow
Abstract
The tumbling of a rigid rod in a shear flow is analyzed in the high viscosity limit. Following Burgers, the Master Equation is derived for the probability distribution of the orientation of the rod. The equation contains one dimensionless number, the Weissenberg number, which is the ratio of the shear rate and the orientational diffusion constant. The equation is solved for the stationary state distribution for arbitrary Weissenberg numbers, in particular for the limit of high Weissenberg numbers. The stationary state gives an interesting flow pattern for the orientation of the rod, showing the interplay between flow due to the driving shear force and diffusion due to the random thermal forces of the fluid. The average tumbling time and tumbling frequency is calculated as a function of the Weissenberg number. A simple crossover function is proposed which covers the whole regime from small to large Weissenberg numbers.
 Publication:

Journal of Statistical Mechanics: Theory and Experiment
 Pub Date:
 September 2014
 DOI:
 10.1088/17425468/2014/09/P09007
 arXiv:
 arXiv:1406.1317
 Bibcode:
 2014JSMTE..09..007V
 Keywords:

 Condensed Matter  Statistical Mechanics
 EPrint:
 22 pages, 9 figures