title: Inhomogeneous distribution of Chlamydomonas in a cylindrical container with a bubble plume.
abstract: Swimming microalgae show various taxes, such as phototaxis and gravitaxis, which sometimes result in the formation of a cell-rich layer or a patch in a suspension. Despite intensive studies on the effects of shear flow and turbulence on the inhomogeneous distribution of microalgae, the effect of a bubble plume has remained unclear. In this study, we used Chlamydomonas as model microalgae, and investigated the spatial distribution of cells in a cylindrical container with a bubble plume. The results illustrate that cells become inhomogeneously distributed in the suspension due to their motility and photo-responses. A vortical ring distribution was observed below the free surface when the bubble flow rate was sufficiently small. We performed a scaling analysis on the length scale of the vortical ring, which captured the main features of the experimental results. These findings are important in understanding transport phenomena in a microalgae suspension with a bubble plume.
authors.affiliation: Graduate School of Biomedical Engineering, Tohoku University, 6-6-01 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Nonaka
authors.affiliation: Dept. Bioengineering and Robotics, Graduate School of Engineering, Tohoku University, 6-6-01 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Kikuchi
authors.affiliation: Graduate School of Biomedical Engineering, Tohoku University, 6-6-01 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Numayama-Tsuruta
authors.affiliation: Dept. Bioengineering and Robotics, Graduate School of Engineering, Tohoku University, 6-6-01 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan.
authors.forename: Azusa
authors.initials: A
authors.lastname: Kage
authors.affiliation: Faculty of Education, Aichi University of Education, 1 Hirosawa, Igaya-cho, Kariya, Aichi 448-8542, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Ueno
authors.affiliation: Graduate School of Biomedical Engineering, Tohoku University, 6-6-01 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan Dept. Bioengineering and Robotics, Graduate School of Engineering, Tohoku University, 6-6-01 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan ishikawa@pfsl.mech.tohoku.ac.jp.
authors.forename: Takuji
authors.initials: T
authors.lastname: Ishikawa
keywords: Aeration; Biofluid mechanics; Flow visualization; Microorganism; Swimming; Vortex