Impact of Bioconvection and Chemical Reaction on MHD Nanofluid Flow Due to Exponential Stretching Sheet

Thermal management is a crucial task in the present era of miniatures and other gadgets of compact heat density. This communication presents the momentum and thermal transportation of nanofluid flow over a sheet that stretches exponentially. The fluid moves through a porous matrix in the presence of a magnetic field that is perpendicular to the flow direction. To achieve the main objective of efficient thermal transportation with increased thermal conductivity, the possible settling of nano entities is avoided with the bioconvection of microorganisms. Furthermore, thermal radiation, heat source dissipation, and activation energy are also considered. The formulation in the form of a partial differential equation is transmuted into an ordinary differential form with the implementation of appropriate similarity variables. Numerical treatment involving Runge–Kutta along with the shooting technique method was chosen to resolve the boundary values problem. To elucidate the physical insights of the problem, computational code was run for suitable ranges of the involved parameters. The fluid temperature directly rose with the buoyancy ratio parameter, Rayleigh number, Brownian motion parameter, and thermophoresis parameter. Thus, thermal transportation enhances with the inclusion of nano entities and the bioconvection of microorganisms. The findings are useful for heat exchangers working in various technological processors. The validation of the obtained results is also assured through comparison with the existing result. The satisfactory concurrence was also observed while comparing the present symmetrical results with the existing literature.

Electromagnetohydrodynamic bioconvective flow of binary fluid containing nanoparticles and gyrotactic microorganisms through a stratified stretching sheet

Bioconvection has recently been the subject of dispute in a number of biotechnological fields that depend on fluids and their physical properties. When mixed nanofluids are subjected to heat and mass transmission, the process of bioconvection occurs. This attempt conveys the theoretical analysis of two-dimensional electrically conducting and magnetically susceptible binary fluid containing nanoparticles and gyrotactic microorganisms past a stratified stretching surface. Furthermore binary chemical reaction, thermal radiation, and activation energy are taken into assumptions. The analytical solution based on HAM has been performed. The convergence of HAM is presented with the help of figures. The present study is compared with previously published results and has established an excessive agreement which validate the present study. It is perceived that the presence and absence of an electric field influences the variations in fluid velocities due to presence of magnetic field. The micropolar constant heightens the velocity and microrotation of the fluid flow. The buoyancy parameter and bioconvection Rayleigh number diminish the velocity function while these parameters show dual impact on microrotation function. The skin friction and couple stress escalates with the increasing buoyancy ratio parameter and bioconvection Rayleigh number.

Numerical Study of Thermophoresis on Mass Transfer from Natural Convection Flow over a Vertical Porous Medium with Variable Wall Heat Fluxes

This study investigates heat and mass transfer under natural convection flow along a vertical permeable surface with variable wall heat fluxes through a porous medium. The non-Darcian model is employed for the medium. The effects of suction/blowing, inertia, buoyancy ratio, exponent of heat flux, position parameter, Schmidt number, and thermophoresis are considered. The governing equations of continuity, momentum, energy, and concentration are solved by adopting similarity transformation and Runge–Kutta integration with a shooting technique. Results of interest, such as velocity, temperature, and concentration profiles related to local Nusselt and Sherwood numbers, are obtained for the selected buoyancy ratio at different magnitudes of the thermophoretic effect. The numerical solutions help us to realize the gas diffusion phenomena and control the transport technology.

Numerical investigation of double-diffusive mixed convection of Fe3O4/Cu/Al2O3-water nanofluid flow through a backward-facing-step channel subjected to magnetic field

Purpose This study aims to investigate the buoyancy-induced heat and mass transfer phenomena in a backward-facing-step (BFS) channel subjected to applied magnetic field using different types of nanofluid. Design/methodology/approach Conservation equations of mass, momentum, energy and concentration are used through velocity-vorticity form of Navier–Stokes equations and solved using Galerkin’s weighted residual finite element method. The density variation is handled by Boussinesq approximation caused by thermo-solutal buoyancy forces evolved at the channel bottom wall having high heat and concentration. Simulations were carried out for the variation of Hartmann number (0 to 100), buoyancy ratio (−10 to +10), three types of water-based nanofluid i.e. Fe3O4, Cu, Al2O3 at χ = 6%, Re = 200 and Ri = 0.1. Findings The mutual interaction of magnetic force, inertial force and nature of thermal-solutal buoyancy forces play a significant role in the heat and mass transport phenomena. Results show that the size of the recirculation zone increases at N = 1 for aiding thermo-solutal buoyancy force, whereas the applied magnetic field dampened the fluid-convection process. With an increase in buoyancy ratio, Al2O3 nanoparticle shows a maximum 54% and 67% increase in convective heat and mass transfer, respectively at Ha = 20 followed by Fe3O4 and Cu. However, with increase in Ha the Nuavg and Shavg diminish by maximum 62.33% and 74.56%, respectively, for Fe3O4 nanoparticles at N = 5 followed by Al2O3 and Cu. Originality/value This research study numerically examines the sensitivity of Fe3O4, Cu and Al2O3 nanoparticles in a magnetic field for buoyancy-induced mixed convective heat and mass transfer phenomena in a BFS channel, which was not analyzed earlier.

Three-Dimensional Numerical Study of the Effect of Protective Barrier on the Dispersion of the Contaminant in a Building

The finite volume method and potential-vorticity vector formalism in their three-dimensional form were used to numerically study the impact of an adiabatic and impermeable vertical barrier on the dispersion of a local aero-contaminant due to the double-diffusive Rayleigh–Benard convection inside a cubic container. Different governing parameters such as the Rayleigh number, buoyancy ratio and barrier height were analyzed for Le = 1.2 and Pr = 0.7, representing an air-contaminant mixture. The potential-vector-vorticity formalism in the three-dimensional form allowed the elimination of the pressure terms appearing in the Navier–Stokes equations. It was found that the heat and mass transfer as well as the effectiveness of the barrier in reducing contaminant dispersion are strongly influenced by the buoyancy ratio, the barrier size and the Rayleigh number. In addition, the barrier effectiveness is more than 70% for a height of half the building height.

Bioconvection in a porous square cavity containing gyrotactic microorganisms under the effects of heat generation/absorption

In this paper, the bioconvective nanofluid flow in a porous square cavity containing gyrotactic microorganisms in the presence of heat generation/absorption is investigated. The bioconvection flow in porous medium is formulated based on Darcy model of Boussinesq approximation. Galerkin finite elements method is employed to solve the governing equations. The numerical results are obtained and discussed the effect of parameters such as Rayleigh number Ra, bioconvection number Rayleigh number Rb, Peclet number Pe, Lewis number Le, Brownian motion Nb, Thermophoresis Nt, Schmidt number Sc, Prandtl number Pr, heat generation/absorption Q and buoyancy ratio Nr. Also, the average Sherwood number, average Nusselt number and average density number are discussed. The present solutions are validated with existing studies under limited cases. It is found that Peclet number and buoyancy ratio show a significant increasing effect on the streamlines, isotherms, isoconcentrations of nanoparticles and microorganisms. The heat generation/absorption reverses the patterns of the flow, temperature distribution and isoconcentrations of nanoparticles and microorganisms.

Double-Diffusive of a Nanofluid in a Rectangle-Shape Mounted on a Cavity Saturated by Heterogeneous Porous Media

This study presents numerical simulations on double-diffusive flow of a nanofluid in two cavities connected with four vertical gates. Novel shape of an outer square shape mounted on a square cavity by four gates was used. Heterogeneous porous media and Al 2 O 3 -water nanofluid are filled in an inner cavity. Outer rectangle shape is filled with a nanofluid only, and its left walls carry high temperature T h and high concentration C h . The right walls of a rectangle shape carry low temperature T c and low concentration C c and the other walls are adiabatic. An incompressible smoothed particle hydrodynamics (ISPH) method is applied for solving the governing equations of velocities, temperature, and concentration. Results are introduced for the effects of a buoyancy ratio − 2 ≤ N ≤ 2 , Darcy parameter 10 − 3 ≤ Da ≤ 10 − 5 , solid volume fraction 0 ≤ ϕ ≤ 0.05 , and porous levels. Main results are indicated in which the buoyancy ratio parameter adjusts the directions of double-diffusive convection flow in an outer shape and inner cavity. Adding more concentration of nanoparticles reduces the flow speed and maximum of the velocity field. Due to the presence of a porous medium layer in an inner cavity, the Darcy parameter has slight changes inside the rectangle shape.

Thermosolutal convection of a nanofluid in ∧-shaped cavity saturated by a porous medium

Purpose The purpose of this study is to simulate the thermo-solutal convection resulting from a circular cylinder hanging in a rod inside a ∧-shaped cavity. Design/methodology/approach The two dimensional ∧-shaped cavity is filled by Al2O3-water nanofluid and saturated by three different levels of heterogeneous porous media. An incompressible smoothed particle hydrodynamics (ISPH) method is adopted to solve the governing equations of the present problem. The present simulations have been performed for the alteration of buoyancy ratio (−2≤N≤2), radius of a circular cylinder (0.05≤Rc≤0.3), a height of a rod (0.1≤Lh≤0.4), Darcy parameter (10−3≤Da≤10−5), Lewis number (1≤Le≤40), solid volume fraction (0≤ϕ≤0.06), porous levels (0≤η1=η2≤1.5)and various boundary-wall conditions. Findings The performed numerical simulations indicated the importance of embedded shapes on the distributions of temperature, concentration and velocity fields inside ∧-shaped cavity. Increasing buoyancy ratio parameter enhances thermo-solutal convection and nanofluid velocity. Adiabatic conditions of the vertical-walls of ∧-shaped cavity augment the distributions of the temperature and concentration. Regardless the Darcy parameter, a homogeneous porous medium gives the lowest values of a nanofluid velocity. Originality/value ISPH method is used to simulate thermo-solutal convection of a nanofluid inside a novel ∧-shaped cavity containing a novel embedded shape and heterogeneous porous media.

Effects of buoyancy ratio on diffusion of solid particles inside a pipe during double diffusive flow of a nanofluid

Purpose The purpose of this study is to use an incompressible smoothed particle hydrodynamics (ISPH) method for simulating buoyancy ratio and magnetic field effects on double diffusive natural convection of a cooper-water nanofluid in a cavity. An open pipe is embedded inside the center of a cavity, and it is occupied by solid particles. Design/methodology/approach The dimensionless governing equations in Lagrangian form were solved by ISPH method. Two different thermal conditions were considered for the solid particles. The actions of the solid particles were tracked inside a cavity. The effects of Hartman parameter, Rayleigh number, nanoparticles volume fraction and Lewis number on features of heat and mass transfer and flow field were tested. Findings The results showed that the buoyancy ratio changes the directions of the solid particles diffusion in a cavity. The hot solid particles were raised upwards at aiding mode (N > 0) and downwards at an opposing mode (N < 0). A comparison is made with experimental and numerical simulation results, and it showed a well agreement. Originality/value Novel studies for the impacts of buoyancy ratio on the diffusion of solid particles embedded in an open pipe during double-diffusive flow were conducted.