Modelling the collective behaviour of gyrotactic micro-swimmers in a dilute suspension
Date:
Bottom-heavy motile micro-organisms (swimmers) orient themselves under the influence of gravitational and viscous torque. In a downflowing pipe, the balance between the two torques will cause the micro-organism to swim towards the centre, forming a focused beam-like structure. This sideway drift of bottom-heavy swimmers is known as gyrotaxis. Gyrotaxis is responsible for many naturally occurring phenomena, such as bioconvection and the formation of thin phytoplankton layers in some part of the ocean where shearing is strong.
In this talk, I will first briefly present different strategies to model a suspension of gyrotactic swimmers. Then, I will show the (re-)discovery of a singularity in the suspension that gives rise to the gyrotactic plume and a bifurcation in the system that may lead to bioconvection. Lastly, I will briefly mention the current challenges in extending the current work to more a complex flowing environment and how we may overcome it with a new continuum model at the population level.