The Orientation of Swimming Biflagellates in Shear Flows
- 449 Downloads
Biflagellated algae swim in mean directions that are governed by their environments. For example, many algae can swim upward on average (gravitaxis) and toward downwelling fluid (gyrotaxis) via a variety of mechanisms. Accumulations of cells within the fluid can induce hydrodynamic instabilities leading to patterns and flow, termed bioconvection, which may be of particular relevance to algal bioreactors and plankton dynamics. Furthermore, knowledge of the behavior of an individual swimming cell subject to imposed flow is prerequisite to a full understanding of the scaled-up bulk behavior and population dynamics of cells in oceans and lakes; swimming behavior and patchiness will impact opportunities for interactions, which are at the heart of population models. Hence, better estimates of population level parameters necessitate a detailed understanding of cell swimming bias. Using the method of regularized Stokeslets, numerical computations are developed to investigate the swimming behavior of and fluid flow around gyrotactic prolate spheroidal biflagellates with five distinct flagellar beats. In particular, we explore cell reorientation mechanisms associated with bottom-heaviness and sedimentation and find that they are commensurate and complementary. Furthermore, using an experimentally measured flagellar beat for Chlamydomonas reinhardtii, we reveal that the effective cell eccentricity of the swimming cell is much smaller than for the inanimate body alone, suggesting that the cells may be modeled satisfactorily as self-propelled spheres. Finally, we propose a method to estimate the effective cell eccentricity of any biflagellate when flagellar beat images are obtained haphazardly.
KeywordsSwimming algae Upswimming Gravitaxis Effective eccentricity Biflagellate Regularized Stokeslets Gyrotaxis Sedimentation torque
Unable to display preview. Download preview PDF.
- Bees, M. A., & Hill, N. A. (1997). Wavelengths of bioconvection patterns. J. Exp. Biol., 200, 1515–1526. Google Scholar
- Cortez, R., Fauci, L., & Medovikov, A. (2005). The method of regularized stokeslets in three dimensions: Analysis, validation, and application to helical swimming. Phys. Fluids 17. Google Scholar
- Fauci, L. J. (1996). A computational model of the fluid dynamics of undulatory and flagellar swimming. Am. Zool., 36, 599–607. Google Scholar
- Gray, J., & Hancock, G. J. (1955). The propulsion of sea-urchin spermatazoa. J. Exp. Biol., 32, 802–814. Google Scholar
- Hill, N. A., & Häder, D. P. (1996). A biased random walk model for the trajectories of swimming micro-organisms. J. Theor. Biol., 41, 503–526. Google Scholar
- Jones, M. (1995). Hydrodynamics of Biflagellate Locomotion. Ph.D. thesis. University of Leeds. Google Scholar
- Lauga, E., & Powers, T. R. (2009). The hydrodynamics of swimming microorganisms. Rep. Prog. Phys. 72. Google Scholar
- Omoto, C. K., Gibbons, I. R., Kamiya, R., Shingyoji, C., Takahashi, K., & Witman, G. B. (1999). Rotation of the central pair microtubules in eukaryotic flagella. Mol. Biol. Cell, 10, 1–4. Google Scholar