Effects of both diffuse and collimated incident radiation on phototactic bioconvection

TL;DR

This study numerically examines how diffuse and collimated light influences the stability and bioconvection patterns of phototactic algae, revealing mode transitions and oscillatory behaviors based on incident angle variations.

Contribution

It introduces a detailed numerical analysis of the effects of incident light angle on bioconvective stability in algal suspensions, highlighting mode transitions and oscillations.

Findings

Transition from stationary to overstable modes with changing incident angle

Mode 2 to mode 1 instability transition observed

Oscillatory disturbance modes emerge at higher incident angles

Abstract

The linear stability of a finite-depth algal suspension is investigated numerically with particular emphasis on the effects of angle of incidence. The suspension of phototactic algae is uniformly illuminated by both diffuse and oblique collimated irradiation. The bioconvective solutions show a transition of the most unstable mode of disturbance from the stationary (overstable) to overstable (stationary) state at the variation in angle of incidence for fixed parameter ranges. Furthermore, a transition from mode 2 to mode 1 instability is noticed for some parameter values as the angle of incidence varies. Oscillatory modes of disturbance are also predicted at the increment in angle of incidence (or cell swimming speed)