Thermo-bioconvection of oxytactic microorganisms in porous media in the presence of magnetic field

Abstract

Purpose This study aims to explore magnetohydrodynamic (MHD) thermo-bioconvection of oxytactic microorganisms in multi-physical directions addressing thermal gradient, lid motion, porous substance and magnetic field collectively using a typical differentially heated two-sided lid-driven cavity. The consequences of a range of pertinent parameters on the flow structure, temperature, oxygen isoconcentration and microorganisms’ isoconcentration are examined and explained in great detail. Design/methodology/approach Two-dimensional governing equations in a two-sided lid-driven porous cavity heated differentially and packed with oxytactic microorganisms under the influence of the magnetic field are solved numerically using the finite volume method-based computational fluid dynamics code. The evolved flow physics is analyzed assuming a steady laminar incompressible Newtonian flow within the validity of the Boussinesq approximation. The transport of oxytactic microorganisms is formulated by augmenting the continuum model. Findings The mechanisms involved with MHD-mixed thermo-bioconvection could have potential benefits for industrial exploitation. The distributions of fluid flow, temperature, oxygen and motile microorganisms are markedly modified with the change of convection regime. Both speed and direction of the translating walls significantly influence the concentration of the motile microorganisms. The concentration of oxygen and motile microorganisms is found to be higher at the upper portion of the cavity. The overall patterns of the fluid flow, temperature and the oxygen and microorganism distributions are markedly affected by the increase of magnetic field strength. Research limitations/implications The concept of the present study could be extended to other areas of bioconvection in the presence of gravity, light or chemical attraction. Practical implications The findings of the present study could be used to multi-physical applications like biomicrosystems, pollutant dispersion in aquifers, chemical catalytic converters, geothermal energy usage, petroleum oil reservoirs, enhanced oil recovery, fuel cells, thermal energy storage and others. Originality/value The MHD-mixed thermo-bioconvection of oxytactic microorganisms is investigated under different parametric conditions. The effect of pertinent parameters on the heat and mass transfers are examined using the Nusselt number and Sherwood number.

Magnetohydrodynamic mixed bioconvection of oxytactic microorganisms in a nanofluid-saturated porous cavity heated with a bell-shaped curved bottom

“…The nonconducting and non-magnetic solid materials are used for porous substance and enclosure walls; thus, magnetic fields do not act on these solid materials. The nanofluid flow through the porous medium is modeled following the Brinkman-Forchheimer-Darcy model (BFDM) considering local thermodynamic equilibrium (Biswas et al, 2020a). The major advantage of the DFDM is it can effectively address the resistive forces fluid experiencing when passing through the porous substance, by taking care of both Darcy and inertial frictions (respectively, handled by the Darcy and Forchheimer terms) over the parametric space in the entire cavity.…”

“…Based on the aforementioned facts and assumptions, the conservations of the total mass, momentum, energy, concentration and microorganisms (Kuznetsov, 2006;Biswas et al, 2020a) can be written in the dimensional form (in the Cartesian coordinates) as:…”

“…DC = C o À C min is the maximum difference in oxygen concentration (where C o is the reference oxygen concentration at the walls and C min is the minimum oxygen concentration needed for the microorganisms to be active). Furthermore, Àd n indicates the utilization of oxygen by the microorganisms (Biswas et al, 2020a). From the momentum equation (3), it is clear that the last term indicates the net buoyancy due to microorganisms and thermal effect (Hillesdon and Pedley, 1996;Sheremet and Pop, 2014;Balla et al, 2018).…”

“…where the dimensionless variables X and Y are the Cartesian coordinates, U and V are, respectively, the horizontal and vertical velocity components, P is the pressure, u is the temperature and w and N are, respectively, the oxygen concentration and microorganisms number density. Through some algebraic operations and rearrangements, equations (1)-( 6) are transformed into dimensionless governing equations (Sheremet and Pop, 2014;Biswas et al, 2020a) as:…”

“…With the advances in science and technology, thermobioconvective phenomena find numerous applications. Biology, medical science, bio-reactors, bacteria-powered microfluidic micro-mixers, targeted drug release, removal of tumors, synergistic impacts in immunology, chemical processing equipment, sustainable fuel cell technology, bio-petroleum energies are a few examples of its utility (Biswas et al, 2020a; HFF 15,4 Rana et al, 2020;Sheremet et al, 2019;Ahmed et al, 2018;Uddin et al, 2018;Uddin et al, 2019;Zohra et al, 2019;Zohra et al, 2020;Amirsom et al, 2019).…”