Many microorganisms propel through fluid environments by deforming their bodies in some manner. The particular nature of these deformation can often be changed by the organism to adapt to particular environmental conditions. It has been proposed in the literature that this adaptation is driven by the desire to optimise the swimming efficiency. However, it remains an open question as to whether this is indeed the optimised quantity for microorganisms. We study propulsion in Newtonian fluids at zero inertia for a model organism, Taylor's waving sheet. We can understand the swimming of this organism with a simple analytic model based on resistive force theory, which we call the rod model. Using this rod model and numerical methods we have developed to calculate flow fields for sheets of arbitrary swimming gaits, we can investigate the optimization of various quantities that can potentially be optimised by a swimming microorganisms. We compare the optimization of efficiency and swimming speed, showing the optimal gaits and conclude that one cannot claim that optimising the swimming efficiency is the strategy adopted by swimming microorganisms.
This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..