Advances in Bioconvection

Abstract

The term “bioconvection” describes hydrodynamic instabilities and patterns in suspensions of biased swimming microorganisms. Hydrodynamic instabilities arise from coupling between cell swimming behaviors; physical properties of the cells, such as density; and fluid flows. For instance, a combination of viscous and gravitational torques can lead to cells swimming toward downwelling fluid. If the cells are more dense than the fluid, then a gyrotactic instability results. Phototaxis describes the directed response of cells to light, which can also lead to instability. Bioconvection represents a classic system where macroscopic phenomena arise from microscopic cellular behavior in relatively dilute systems. There are ecological consequences for bioconvection and the mechanisms involved as well as potential for industrial exploitation. The focus of this review is on progress measuring and modeling gyrotactic and phototactic bioconvection. It builds on two earlier reviews of bioconvection and recent interest in active matter, describing progress and highlighting open problems.

Origins of eukaryotic excitability

“…For this they must be able to integrate and respond to multisensory information: such as light, chemicals, flows and gravity. Such single-cell responses can lead to large-scale population structures such as algal blooms, even formation of photo-gyro-gravitactic bioconvection patterns and instabilities [ 145 , 146 ]. In general, behavioural transitions are mediated by stimuli-dependent ionic currents and an excitable membrane, coupled to some form of self-locomotion.…”

Bifurcation and stability of downflowing gyrotactic micro-organism suspensions in a vertical pipe

“…In a suspension of these micro-organisms, such taxes can significantly impact on how they distribute themselves both spatially and temporally as well as on rheological properties. For example, in a shallow suspension of swimming algae where bioconvective patterns are often observed, light, oxygen and gravity are known to suppress or encourage the pattern formation (Bees 2020).…”

An overstability analysis of vertically vibrated suspension of active swimmers subjected to thermal stratification

“…Nayak and co-workers performed the computations for the three-dimensional slip profiles of gyrotactic swimmers in the existence of chemically reacted nanofluid [34]. A detailed review addressing the successive developments and advances of the bioconvection theory is available in the literature [35].…”