Benjamin Walker

University College London/University of Bath University College London/University of Bath

Multiscale methods and microswimmer models

Fluids and Materials Seminar

9th February 2023, 2:00 pm – 3:00 pm
Fry Building, 2.04

Swimming on the microscale has long been the subject of intense research efforts, from experimental studies of bacteria, sperm, and algae through to varied theoretical questions of low-Reynolds-number fluid mechanics. The biological and biophysical settings that drive this ongoing research are often confoundingly complex, a fact that has driven the development and use of simple models of microswimmers. In this talk, we'll motivate and explore some of these models, building up our intuition for Stokesian fluid dynamics and the behaviours of microscale swimmers. Using these models, we will showcase how we can often exploit separated scales present in these problems to reveal surprisingly simple emergent dynamics, ranging from coarse-grained flow profiles to predictions of globally attracting, long-term behaviours. In doing so, we'll also uncover a surprising cautionary tale, the root of which is captured by a single, elementary statement that nevertheless calls into question much of the intuition gained from commonplace models of microswimming. In particular, we'll see that a wave-of-the-hands, which I have been guilty of before, can drastically and qualitatively change the dynamics that simple models predict, and we'll see how such missteps can be addressed through systematic multiscale methods.

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