Role of surface undulation during mixed bioconvective nanofluid flow in porous media in presence of oxytactic bacteria and magnetic fields

Abstract

Abstract Transport phenomena involving thermo-bioconvection have become an interesting field of research due to their novel application in various fields of engineering, bio-energy systems, fuel cells, medical science, etc. Design as well as proper control of such a system involving multiphysical transport in a complex geometry is a very difficult task. On such a system, the present study is conducted aiming to examine the magnetohydrodynamic (MHD) mixed bioconvection with oxytactic microorganisms suspended in copper-water nanofluid. The flow takes place through porous media in a top-wall-translating enclosure with a complex wavy sidewall heated uniformly. The right vertical wall is isothermally cooled; other walls are adiabatic. A magnetic field is imposed along the horizontal direction. Evolved flow physics are analyzed by modeling this complex problem involving an undulating heated wall and many coupled transport equations (due to the presence of motile bacteria or organisms) are numerically solved through a finite volume-based code. The thermo-fluid behaviors are studied extensively to explore the controllability of different involved parameters that could help the system s design and operation. The important parameters influencing the complex physics in the enclosure are the number of undulations (n), bioconvection Rayleigh number (Rb), Darcy number (Da), Hartmann number (Ha), Peclet number (Pe), Lewis number (Le), oxygen diffusion ratio (χ), Grashof number (Gr). The study reveals that the undulating curved surface enhances the heat transfer up to certain optimal magnitudes of undulations at the different operating conditions. The mass transfer rate increases with all undulations and bioconvection supports this trend. Bioconvection always favors heat transfer. In general, it is found that by adjusting the involved flow parameters and number of undulations, the local as well as global transport mechanisms, can be controlled effectively. The concept of this investigation could be found in the designing of microbial fuel cells and different nanotechnology-based bioconvection.