Dynamics of two-dimensional self-propelled turbulence near the slipping boundary
| Autor: | Wen-Yang Chang, 張文陽 |
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| Rok vydání: | 2013 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 101 The high concentration suspensions of bacteria in the liquid exhibit turbulent like behaviors in the form of multi-scale vortices and jets, through the interplay of self-propelling and nonlinear mutual interactions between cells. Regardless of the recent intensive studies on the bacterial turbulence, the effect of boundary on their collective motions and turbulence is still elusive. In this work, for the first time, the dynamical behaviors of the turbulence of dense E. coli suspensions nearby a slipping boundary of a thin liquid film is experimentally investigated. By carefully stretching a liquid film with E. coli suspensions, an ultra-thin film called “common black film (CBF)” is formed at the center of the thin liquid film. The small thickness of the CBF forms a slipping boundary which prevents the cells to move into the CBF. The 2D velocity distribution functions of local cell velocities along two normal directions, and the velocity and the vorticity fields, are measured via particle image velocimetry (PIV). It is found that the slipping boundary suppresses transverse motion and enhance longitudinal motion of cells nearby the boundary. The cell motion gradually becomes more isotropic in the region with increasing distance from the boundary. The synchronized chaotic rocking jets with long range correlation in the region surrounding the CBF boundary, due to the long distance propagation of the information of flow alignment along the boundary, are observed for the first time. When the CBF becomes small, the synchronized chaotic rocking can be extended to the region surrounding the entire CBF boundary. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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