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Article
Publication date: 15 February 2021

Nirmalendu Biswas, Nirmal K. Manna, Dipak Kumar Mandal and Rama Subba Reddy Gorla

The purpose of this study is to address magnetohydrodynamic (MHD) bioconvection caused by the swimming of oxytactic microorganisms in a linearly heated square cavity…

Abstract

Purpose

The purpose of this study is to address magnetohydrodynamic (MHD) bioconvection caused by the swimming of oxytactic microorganisms in a linearly heated square cavity filled with porous media and Cu–water nanofluid. The effects of different multiphysical aspects are demonstrated using local distributions as well as global quantities for fluid flow, temperature, oxygen concentration and microorganisms population.

Design/methodology/approach

The coupled transport equations are converted into the nondimensional partial differential equations, which are solved numerically using a finite volume-based computing code. The flow of Cu–water nanofluid through the pores of porous media is formulated following the Brinkman–Forchheimer–Darcy model. The swimming of oxytactic microorganisms is handled following a continuum model.

Findings

The analysis of transport phenomena of bioconvection is performed in a linearly heated porous enclosure containing Cu–water nanofluid and oxytactic microorganisms under the influence of magnetic fields. The application of such a system could have potential impacts in diverse fields of engineering and science. The results show that the flow and temperature distribution along with the isoconcentrations of oxygen and microorganisms is markedly affected by the involved governing parameters.

Research limitations/implications

Similar study of bioconvection could be extended further considering thermal radiation, chemical attraction, gravity and light.

Practical implications

The outcomes of this investigation could be used in diverse fields of multiphysical applications, such as in food industries, chemical processing equipment, fuel cell technology and enhanced oil recovery.

Originality/value

The insight of the linear heating profile reveals a special attribute of simultaneous heating and cooling zones along the heated side. With such an interesting feature, the MHD bioconvection of oxytactic microorganisms in nanofluid-filled porous substance is not reported so far.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 11
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 16 November 2021

Dipak Kumar Mandal, Milan Kumar Mondal, Nirmalendu Biswas, Nirmal K. Manna, Rama Subba Reddy Gorla and Ali J. Chamkha

This study aims to focus on a thermo-fluid flow in a partially driven cavity (PDC) using Cu-water nanoliquid, magnetic field and porous substance. The cooling and sliding…

Abstract

Purpose

This study aims to focus on a thermo-fluid flow in a partially driven cavity (PDC) using Cu-water nanoliquid, magnetic field and porous substance. The cooling and sliding motion are applied on the upper half of the vertical walls and the bottom wall is heated. Thermal characteristics are explored to understand magnetohydrodynamic convection in a nanoliquid filled porous system from a fundamental viewpoint. The governing parameters involved to cater to the moving speed of the sidewalls and partial translation direction are the relative strength of thermal buoyancy, porous substance permeability, magnetic field intensity, nanoparticle suspension and orientation of the cavity.

Design/methodology/approach

The coupled transport equations of the problem are solved using an in-house developed finite volume-based computing code. The staggered nonuniform grids along the x and y directions are used. The SIMPLE algorithm technique is considered for the iterative solution of the discretized equations with the convergence check of the continuity mass defect below 10–10.

Findings

The present study unveils that the heat transfer enhances at higher Ri with the increasing value of Re, irrespective of the presence of a porous substance or magnetic field or the concentration of nanofluid. Apart from different flow controlling parameters, the wall motions have a significant contribution to the formation of flow vortices and corresponding heat transfer. Orientation of the cavity significantly alters the transport process within the cavity. The upward wall velocity for both the sidewalls could be a better choice to enhance the high heat transfer (approximately 88.39% at Richardson and Reynolds numbers, respectively, 0.1 and 200).

Research limitations/implications

Considering other multi-physical scenarios like porous layers, conducting block, microorganisms and the present investigation could be further extended to analyze a problem of complex flow physics.

Practical implications

In this study, the concept of partially driven wall motion has been adopted under the Cu-water nanoliquid, magnetic field, porous substance and oblique enclosure. All the involved flow-controlling parameters have been experimented with under a wide parametric range and associated thermo-flow physics are analyzed in detail. This outcome of this study can be very significant for designing as well as controlling thermal devices.

Originality/value

The convective process in a partially driven cavity (PDC) with the porous medium has not been investigated in detail considering the multi-physical scenarios. Thus, the present effort is motivated to explore the thermal convection in such an oblique enclosure. The enclosure is heated at its bottom and has partially moving-wall cold walls. It consists of various multi-physical conditions like porous structure, magnetic field, Cu–H2O nanoliquid, etc. The system performance is addressed under different significant variables such as Richardson number, Reynolds number, Darcy number, Hartmann number, nanoliquid concentration and orientation of cavity.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 32 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 29 July 2021

Nirmalendu Biswas, Nirmal Kumar Manna, Dipak Kumar Mandal and Rama Subba Reddy Gorla

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…

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.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 12
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 12 August 2021

Nirmalendu Biswas, Dipak Kumar Mandal, Nirmal K. Manna, Rama Subba Reddy Gorla and Ali J. Chamkha

The aims of this study is to numerically investigate the thermal phenomena during magnetohydrodynamic (MHD) free convection in an oblique enclosure filled with porous…

Abstract

Purpose

The aims of this study is to numerically investigate the thermal phenomena during magnetohydrodynamic (MHD) free convection in an oblique enclosure filled with porous media saturated with Cu–Al2O3/water hybrid nanofluid and heated at the left wavy wall. The thermophysical phenomena are explored thoroughly by varying the amplitude (λ) and undulation (n) of the wavy wall and the inclination of the enclosure (γ) along with other pertinent physical parameters. Darcy–Rayleigh number (Ram), Darcy number (Da), Hartmann number (Ha) and nanoparticle volumetric fraction (ϕ). The effect of all parameters has been analyzed and represented by using heatlines, isotherms, streamlines, average Nusselt number and local Nusselt number.

Design/methodology/approach

The finite volume method is used to work out the transport equations coupled with velocity, pressure and temperature subjected to non-uniform staggered grid structure after grid-sensitivity analysis by an indigenous computing code and the semi-implicit method for pressure linked equations (SIMPLE) algorithm. The solution process is initiated following an iterative approach through the alternate direction implicit sweep technique and the tridiagonal matrix algorithm (TDMA) algorithm. The iterative process is continued until successive minimization of the residuals (<1e-8) for the governing equations.

Findings

This study reveals that the increase in the heating surface area does not always favor heat transfer. An increase in the undulation amplitude enhances the heat transfer; however, there is an optimum value of undulation of the wavy wall for this. The heat transfer enhancement because of the wall curvature is revealed at higher Ram, lower Da and Ha and lower volume fraction of nanoparticles. In general, this augmentation is optimum for four undulations of the wavy wall with an amplitude of λ = 0.3. The heat transfer enhancement can be more at the cavity inclination   γ = 45°.

Research limitations/implications

The technique of this investigation could be used in other multiphysical areas involving partial porous layers, conducting objects, different heating conditions, wall motion, etc.

Practical implications

This study is to address MHD thermo-fluid phenomena of Cu–Al2O3/water-based hybrid nanofluid flow through a non-Darcian porous wavy cavity at different inclinations. The amplitude and number of undulations of the wavy wall, permeability of the porous medium, magnetic field intensity, nanoparticle volumetric fraction and inclinations of the enclosure play a significant role in the heat transfer process. This analysis and the findings of this work can be useful for the design and control of similar thermal systems/devices.

Originality/value

Many researchers have examined the problem of buoyancy-induced free convection in a wavy-porous cavity packed with regular fluids or nanofluids. However, the effect of magnetic fields along with the amplitude (λ) at different undulations (n) of the heated wavy wall of an inclined enclosure is not attended so far to understand the transport mechanisms. Most often, the evolutions of the thermo-fluid phenomena in such complex geometries invoking different multiphysics are very intricate. Numerical implementations for simulations and subsequent post-processing of the results are also challenging.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 32 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 23 November 2020

Nirmalendu Biswas, Aparesh Datta, Nirmal K. Manna, Dipak Kumar Mandal and Rama Subba Reddy Gorla

This study aims to explore magnetohydrodynamic (MHD) thermo-bioconvection of oxytactic microorganisms in multi-physical directions addressing thermal gradient, lid motion…

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.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 25 June 2019

Nirmal Kumar Manna, Nirmalendu Biswas and Pallab Sinha Mahapatra

This study aims to enhance natural convection heat transfer for a porous thermal cavity. Multi-frequency sinusoidal heating is applied at the bottom of a porous square…

Abstract

Purpose

This study aims to enhance natural convection heat transfer for a porous thermal cavity. Multi-frequency sinusoidal heating is applied at the bottom of a porous square cavity, considering top wall adiabatic and cooling through the sidewalls. The different frequencies, amplitudes and phase angles of sinusoidal heating are investigated to understand their major impacts on the heat transfer characteristics.

Design/methodology/approach

The finite volume method is used to solve the governing equations in a two-dimensional cavity, considering incompressible laminar flow, Boussinesq approximation and Brinkman–Forchheimer–Darcy model. The mean-temperature constraint is applied for enhancement analysis.

Findings

The multi-frequency heating can markedly enhance natural convection heat transfer even in the presence of porous medium (enhancement up to ∼74 per cent). Only the positive phase angle offers heat transfer enhancement consistently in all frequencies (studied).

Research limitations/implications

The present research idea can usefully be extended to other multi-physical areas (nanofluids, magneto-hydrodynamics, etc.).

Practical implications

The findings are useful for devices working on natural convection.

Originality/value

The enhancement using multi-frequency heating is estimated under different parametric conditions. The effect of different frequencies of sinusoidal heating, along with the uniform heating, is collectively discussed from the fundamental point of view using the average and local Nusselt number, thermal and hydrodynamic boundary layers and heatlines.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 10
Type: Research Article
ISSN: 0961-5539

Keywords

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