Swimming and Bioconvection of Biflagellated Green Algae

Ehsan Ashraf

Friday 30th October, 2009 16:00-17:00 Mathematics Building, room 325


The biflagellated green algae Chlamydomonas reinhardtii has a prolate spheroidal body and has two long, thin flagella attached at one end which are propelled to cause the swimming of the organism. The length of the cell body and flagella is approx. same as 10 micro meter and the flagella beat at approx. 50 hertz. C. reinhardtii is usually considered to swim in a human breast-stroke manner with an effective-recovery style, approximately in the direction of its axis of symmetry. However, the latest research proved that this is not exactly the accurate swimming stroke. The approximation known as Resistive Force Theory (RFT) was established by Gray & Hancock (1953). RFT and singularity solutions method were used by Jones et al. (1994) to model the swimming of a single cell of C. reinhardtii in a viscous flow of low Reynolds number. Analytical and numerical techniques incorporating RFT and image singularities system were used to calculate the magnitude and direction of the cell's swimming velocity and angular velocity in the vicinity of no slip plane boundary. Recently these cells are effectively used as feed stocks in algae photobiorectors. These cells pumped into tubes with addition of CO2 from power stations and waste water to produce biodiesel with water treatment. Bioconvection phenomena defined as the aggregations of typically dense cells which causes instabilities or pattern formations due to gyrotaxis, geotaxis or phototaxis during large scale flow. Here we have studied the experimental analysis of the bioconvection phenomena in thin long horizontal tubes. By varying the cells concentration C, tubes diameter d and flow rate F, we record the images and analyse the data using IDL and statistical tools to quantitatively investigate the initial wavelengths and trends of the bioconvection patterns. Additionally we will try to compare these experimental results with theoretical predictions.

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