Events in Physics
Friday, January 13, 2023
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Theory group seminar on "Multi-scale analysis and reduced models for low-Reynolds swimmers", SPEAKER: Clément MOREAUPS 128ABSTRACT: Over a long period of time, or from a distance, the motion of many swimmers can appear smooth, with their trajectories appearing almost ballistic. These long-time behaviours, however, often mask more complex dynamics, such as the side-to-side snakelike motion exhibited by spermatozoa as they swim, propelled by the frequent and periodic beating of their flagellum, or shape-changing microorganisms and microrobots. Many models of motion neglect, often without formal justification, these effects in favour of smoother long-term behaviours. In this talk, I will present recent results based on multi-timescale analysis and evaluating the long-term effects of high-frequency oscillations on translational and angular motion for various classical swimming models of micro-scale swimmers, with the purpose of assessing the relevance of neglecting these oscillations, and derive simplified equivalent models. In particular, I will focus on the celebrated Jeffery orbit model established in 1922, which can be, according to our results, surprisingly widely generalised to fast-shape-changing bodies, and provide an interpretation of these reduced models in terms of « effective shapes ».
This research was carried out in collaboration with M. P. Dalwadi, B. J. Walker (UCL), E. A. Gaffney (U. Oxford) and K. Ishimoto (U. Kyoto). |