Magnetohydrodynamic mixed bioconvection of oxytactic microorganisms in a nanofluid-saturated porous cavity heated with a bell-shaped curved bottom
International Journal of Numerical Methods for Heat & Fluid Flow
ISSN: 0961-5539
Article publication date: 29 July 2021
Issue publication date: 24 November 2021
Abstract
Purpose
This study aims to investigate thermo-bioconvection of oxytactic microorganisms occurring in a nanofluid-saturated porous lid-driven cavity in the presence of the magnetic field. The heating is provided through a bell-shaped curved bottom wall heated isothermally. The effects of the peak height of the curved bottom wall, bioconvection Rayleigh number (Rb), Darcy number (Da), Hartmann number (Ha), Peclet number (Pe), Lewis number (Le) and Grashof number (Gr) on the flow structure, temperature and the iso-concentrations of oxygen and microorganisms are examined and explained systematically. The local and global, characteristics of heat transfer and oxygen concentration, are estimated through the Nusselt number (Nu) and Sherwood number (Sh), respectively.
Design/methodology/approach
The governing equations of continuity, momentum, energy and additionally consisting of species transport equations for oxygen concentration and population density of microorganisms, are discretized by the finite volume method. The evolved linearized algebraic equations are solved iteratively through the alternate direction implicit scheme and the tri-diagonal matrix algorithm. The computation domain has meshed in non-uniform staggered grids. The entire computations are carried out through an in-house developed code written in FORTRAN following the SIMPLE algorithm. The third-order upwind and second-order central difference schemes are used for handling the advection and diffusion terms, respectively. The convergence criterion for the iterative process of achieving the final solution is set as 10–8 and 10–10, respectively, for the maximum residuals and the mass defect.
Findings
The results show that the flow and temperature distribution along with the iso-concentrations of oxygen and microorganisms are markedly affected by the curvature of the bottom wall. A secondary circulation is developed in the cavity that changes the flow physics significantly. The Nu increases with the peak height of the curved bottom wall and Da; however, it decreases with Ha and Rb. The Sh increases with Da but decreases with Ha and the peak height of the curved wall.
Research limitations/implications
A similar study of bioconvection could be extended further considering thermal radiation, chemical attraction, gravity, light, etc.
Practical implications
The outcomes of this investigation could be used in diverse fields of multi-physical applications such as in food industries, chemical processing equipment, fuel cell technology and enhanced oil recovery.
Originality/value
The insights of bioconvection of oxytactic microorganisms using a curved bottom surface along with other physical issues such as nanofluid, porous substance and magnetic field are addressed systematically and thoroughly.
Keywords
Acknowledgements
The authors would like to thank the anonymous reviewers for their valuable comments to improve the quality of this work. The authors also gratefully acknowledge Dr Pallab Sinha Mahapatra (Department of Mechanical Engineering, IIT Madras, India) and Dr Andrew Rees (Department of Mechanical Engineering, University of Bath, UK) for their valuable views on the technical aspects of the present investigation.
Conflict of interest
None declared.
Citation
Biswas, N., Manna, N.K., Mandal, D.K. and Gorla, R.S.R. (2021), "Magnetohydrodynamic mixed bioconvection of oxytactic microorganisms in a nanofluid-saturated porous cavity heated with a bell-shaped curved bottom", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 31 No. 12, pp. 3722-3751. https://doi.org/10.1108/HFF-10-2020-0668
Publisher
:Emerald Publishing Limited
Copyright © 2021, Emerald Publishing Limited