title: Spontaneous circulation of confined active suspensions.
abstract: Many active fluid systems encountered in biology are set in total geometric confinement. Cytoplasmic streaming in plant cells is a prominent and ubiquitous example, in which cargo-carrying molecular motors move along polymer filaments and generate coherent cell-scale flow. When filaments are not fixed to the cell periphery, a situation found both in vivo and in vitro, we observe that the basic dynamics of streaming are closely related to those of a nonmotile stresslet suspension. Under this model, it is demonstrated that confinement makes possible a stable circulating state; a linear stability analysis reveals an activity threshold for spontaneous autocirculation. Numerical analysis of the longtime behavior reveals a phenomenon akin to defect separation in nematic liquid crystals and a high-activity bifurcation to an oscillatory regime.
authors.affiliation: Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom.
authors.forename: Francis G
authors.initials: FG
authors.lastname: Woodhouse
authors.forename: Raymond E
authors.initials: RE
authors.lastname: Goldstein
mesh_terms: D003595:Cytoplasmic Streaming; D057446:Hydrodynamics; D050866:Liquid Crystals; D008954:Models, Biological; D013535:Suspensions
chemical_list: D013535:Suspensions