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1 – 10 of 144To investigate numerically the settling of small solid particles in a suspension of motile gyrotactic micro‐organisms in order to evaluate the possibility of using bioconvection…
Abstract
Purpose
To investigate numerically the settling of small solid particles in a suspension of motile gyrotactic micro‐organisms in order to evaluate the possibility of using bioconvection to slow down settling and enhance mixing between particles.
Design/methodology/approach
Numerical computations are performed at the North Carolina Supercomputing Center utilizing an Origin 2400 workstation. A conservative finite‐difference scheme is used to discretize the governing equations. A staggered uniform grid with the stream function and vorticity stored in one set of nodes and the number densities of micro‐organisms and solid particles stored in another set of nodes is utilized. CPU time required to investigate plume development until it attains steady‐state for 36 × 36 uniform mesh is about 50 h.
Findings
It is established that small solid particles that are heavier than water slow down bioconvection. Extremely small particles (nanoparticles) that have negligible settling velocity do not have any noticeable impact on bioconvection, very large particles (that have negligible diffusivity), or very heavy particles (that have very large settling velocity) also do not have any impact on bioconvection because they simply settle at the bottom. However, if the particles are of the optimal size and density (gravitational settling must compete with Brownian diffusion to create an exponential number density distribution of solid particles with the maximum at the bottom of the chamber), these particles can effectively slow down bioconvection.
Research limitations/implications
The question how solid particles may affect the wavelengths of bioconvection patterns requires further investigation.
Practical implications
The finding that solid particles slow down bioconvection may be important in using bioconvection to enhance mixing in fluid microvolumes.
Originality/value
The paper provides a model and numerical data about the effect of bioconvection on mixing of small solid particles. These data are valuable for researches working in fundamental fluid mechanics, multiphase flow, and applications of bioconvection.
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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 filled with…
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.
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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 field…
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.
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Mechanisms of deposition and declogging are considered while formulating a new continuum model for bioconvection in a dilute suspension of motile, negatively geotactic…
Abstract
Mechanisms of deposition and declogging are considered while formulating a new continuum model for bioconvection in a dilute suspension of motile, negatively geotactic microorganisms in a porous medium. According to research in 1988, bioconvection is the name given to pattern‐forming convective motions set up in suspensions of swimming microorganisms. “Negative geotaxis” means that the microorganisms tend to swim against the gravitational force. This paper is motivated by experimental research by Kessler who investigated the effect of porous media on the development of convection instability in algal suspensions. In the model suggested in this paper, the decrease of permeability due to cell adsorption by the porous medium is considered and the influence of this permeability decrease on the development of bioconvection is studied. The existence and stability of a two‐dimensional plume in a rectangular enclosure with stress‐free sidewalls is investigated. Governing equations include the Darcy law as well as the microorganism conservation equations. A conservative finite‐difference scheme is utilized to solve these equations numerically. The analysis of the proposed model reveals that the major factors affecting the development of bioconvection are the initial permeability of the porous medium and the rate of cell deposition. For small permeability, the resistance to the fluid flow is too large, and bioconvection does not develop. If the rate of cell deposition is too large, the number of suspended cells quickly becomes too small because of cell capturing by the porous medium. For this reason, the critical density difference in the top fluid layer cannot be reached, and bioconvection does not develop.
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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, porous…
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.
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– The purpose of this paper is to discuss free convection peristaltic flow in an asymmetric channel with nanofluid containing gyrotactic microorganism.
Abstract
Purpose
The purpose of this paper is to discuss free convection peristaltic flow in an asymmetric channel with nanofluid containing gyrotactic microorganism.
Design/methodology/approach
The governing equations for proposed model are simplified using “long wavelength and low Reynolds number approximation.” Numerical solutions have been presented for “velocity, pressure gradient, the solid volume fraction nanoparticles, temperature profile and density of motile microorganisms.” The effects of various flow parameters, i.e Hartmann number, the solid volume fraction of the nanoparticles amplitude ratio, Prandtl number, bioconvection Péclet number, bioconvection constant, bioconvection Rayleigh number are presented.
Findings
The author finds that the pressure rise increases with an increase in Hartmann number, Grashof number bioconvection, Rayleigh number and buoyancy ratio in the peristaltic pumping section.
Originality/value
The peristaltic flow nanofluid containing gyrotactic microorganism is explored in the literature for the first time.
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Chandra Shekar Balla, C. Haritha, Kishan Naikoti and A.M. Rashad
The purpose of this paper is to investigate the bioconvection flow in a porous square cavity saturated with both oxytactic microorganism and nanofluids.
Abstract
Purpose
The purpose of this paper is to investigate the bioconvection flow in a porous square cavity saturated with both oxytactic microorganism and nanofluids.
Design/methodology/approach
The impacts of the effective parameters such as Rayleigh number, bioconvection number, Peclet number and thermophoretic force, Brownan motion and Lewis number reduces the flow strength in the cavity on the flow strength, oxygen density distribution, motile isoconcentrations and heat transfer performance are investigated using a finite volume approach.
Findings
The results obtained showed that the average Nusselt number is increased with Peclet number, Lewis number, Brownian motion and thermophoretic force. Also, the average Sherwood number increased with Brownian motion and Peclet number and decreased with thermophoretic force. It is concluded that the flow strength is pronounced with Rayleigh number, bioconvection number, Peclet number and thermophoretic force. Brownan motion and Lewis number reduce the flow strength in the cavity.
Originality/value
There is no published study in the literature about sensitivity analysis of Brownian motion and thermophoresis force effects on the bioconvection heat transfer in a square cavity filled by both nanofluid and oxytactic microorganisms.
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A.A. Avramenko and A.V. Kuznetsov
The purpose of this paper is to investigate a combined bioconvection and thermal instability problem in a horizontal layer of finite depth with a basic temperature gradient…
Abstract
Purpose
The purpose of this paper is to investigate a combined bioconvection and thermal instability problem in a horizontal layer of finite depth with a basic temperature gradient inclined to the vertical. The basic flow, driven by the horizontal component of temperature gradient, is the Hadley circulation, which becomes unstable when the vertical temperature difference and density stratification induced by upswimming of microorganisms that are heavier than water become sufficiently large.
Design/methodology/approach
Linear stability analysis of the basic state is performed; the numerical problem is solved using the collocation method.
Findings
The steady‐state solution of this problem is obtained. Linear stability analysis of this steady‐state solution for the case of three‐dimensional disturbances is performed; the numerical problem is solved using the collocation method. The stability problem is governed by three Rayleigh numbers: the bioconvection Rayleigh number and two thermal Rayleigh numbers characterizing temperature gradients in the vertical and horizontal directions, respectively.
Research limitations/implications
Further research should address the application of weakly non‐linear analysis to this problem.
Practical implications
The dependence of the critical bioconvection Rayleigh number on the two thermal Rayleigh numbers and other relevant parameters is investigated.
Originality/value
This paper presents what is believed to be the first research dealing with the effect of inclined temperature gradient on the stability of bioconvection in a suspension of gyrotactic microorganisms.
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S. Sridhar and M. Muthtamilselvan
This paper aims to present a study on stability analysis of Jeffrey fluids in the presence of emergent chemical gradients within microbial systems of anisotropic porous media.
Abstract
Purpose
This paper aims to present a study on stability analysis of Jeffrey fluids in the presence of emergent chemical gradients within microbial systems of anisotropic porous media.
Design/methodology/approach
This study uses an effective method that combines non-dimensionalization, normal mode analysis and linear stability analysis to examine the stability of Jeffrey fluids in the presence of emergent chemical gradients inside microbial systems in anisotropic porous media. The study focuses on determining critical values and understanding how temperature gradients, concentration gradients and chemical reactions influence the onset of bioconvection patterns. Mathematical transformations and analytical approaches are used to investigate the system’s complicated dynamics and the interaction of numerous characteristics that influence stability.
Findings
The analysis is performed using the Jeffrey-Darcy type and Boussinesq estimation. The process involves using non-dimensionalization, using the normal mode approach and conducting linear stability analysis to convert the field equations into ordinary differential equations. The conventional thermal Rayleigh Darcy number
Originality/value
The study’s novelty originated from its investigation of a novel and complicated system incorporating Jeffrey fluids, emergent chemical gradients and anisotropic porous media, as well as the use of mathematical and analytical approaches to explore the system’s stability and dynamics.
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Noura Alsedais, Amal Al-Hanaya and Abdelraheem M. Aly
This paper aims to investigate magnetic impacts on bioconvection flow within a porous annulus between an outer cylinder and five inner cylinders. The annulus is filled by…
Abstract
Purpose
This paper aims to investigate magnetic impacts on bioconvection flow within a porous annulus between an outer cylinder and five inner cylinders. The annulus is filled by oxytactic microorganisms and nano-encapsulated phase change materials.
Design/methodology/approach
The modified ISPH method based on the time-fractional derivative is applied to solve the regulating equations in Lagrangian dimensionless forms. The pertinent factors are bioconvection Rayleigh number Rab (1–100), circular cylinder’s radius Rc (0.1–0.3), fractional time derivative α (0.95–1), Darcy parameter Da (10−5–10−2), nanoparticle parameter ϕ (0–0.1), Hartmann number Ha (0–50), Lewis number Le (1–20), Peclet number Pe (0.1–0.75), s (0.1–0.9), number of cylinders NCylinders (1–4), Rayleigh number Ra (103–106) and fusion temperature θf (0.005–0.9).
Findings
The simulations revealed that there is a strong enhancement in the velocity field according to an increase in Rab. The intensity and location of the phase zone change in response to changes in θf. The time-fractional derivative a acting on a nanofluid velocity and flow characteristics in an annulus. The number of embedded cylinders NCylinders is playing a significant role in the cooling processes and as NCylinders increases from 1 to 4, the velocity field’s maximum reduces by almost 33.3%.
Originality/value
The novelty of this study is examining the impacts of the magnetic field and the presence of several numbers of embedded cylinders on bioconvection flow within a porous annulus between an outer cylinder and five inner cylinders.
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