Phototactic isotropic scattering bioconvection with oblique irradiation

Abstract

The phenomenon of collective movements of microorganisms is referred to as “bioconvection.” Negative phototaxis refers to motions directed away from the source of illumination, and positive phototaxis refers to motions directed in that direction. In this study, numerical analysis is performed on both the steady-state and linear stability solutions of the isotropic scattering suspension with oblique collimated irradiation. The bottom boundary is taken to be rigid and the top is either stress-free or rigid. The governing equations are solved using a fourth-order Newton–Raphson–Kantorovich iteration-based finite-difference accurate method. Through variation in the angle of incidence, we found two different types of nature for lower and higher scattering albedo in the basic state concentration profile. In the case of a rigid (or stress-free) upper boundary, the bioconvection solutions are generally oscillatory (or stationary) and more stable (or unstable). The scattering model coincides with the up-swimming model at higher wavenumbers.