scholarly journals A Revised Model for Magneto Convection in Binary Nanofluids

2019 ◽  
Vol 4 (1) ◽  
pp. 131-138 ◽  
Author(s):  
Jyoti Sharma ◽  
Urvashi Gupta ◽  
Shushant Shukla
Keyword(s):  
Magnetic Field ◽  
Brownian Motion ◽  
Normal Mode ◽  
Scale Effects ◽  
Onset Of Convection ◽  
Nano Scale ◽  
Brownian Motion And Thermophoresis ◽  
Mode Technique ◽  
Double Diffusive

The paper presents double-diffusive nanofluid convection under magnetic field using more realistic revised model in which boundaries are assumed to have zero nanoparticle flux. The nanofluid layer includes the nano scale effects (Brownian motion and thermophoresis) and solutal effects (Dufour and Soret). Impact of different parameters is analyzed using normal mode technique and interpreted graphically with the help of the software Mathematica. Complex expressions for oscillatory motions are solved using approximations to confirm their non-existence and onset of convection is established as stationary. Binary nanofluids are found to be much less stable than regular fluids. Higher conductivity of metallic nanofluids makes them less stable as compared to non-metallic nanofluids.

Double-Diffusive Magneto Convection in a Compressible Couple-Stress Fluid Through Porous Medium

2011 ◽  
Vol 66 (5) ◽  
pp. 304-310 ◽  
Author(s):  
Pardeep Kumar ◽  
Hari Mohan
Keyword(s):  
Magnetic Field ◽  
Porous Medium ◽  
Couple Stress ◽  
Mode Analysis ◽  
Couple Stress Fluid ◽  
Onset Of Convection ◽  
Linearized Stability ◽  
Medium Permeability ◽  
Solute Gradient ◽  
Double Diffusive

The double-diffusive convection in a compressible couple-stress fluid layer heated and soluted from below through porous medium is considered in the presence of a uniform vertical magnetic field. Following the linearized stability theory and normal mode analysis, the dispersion relation is obtained. For stationary convection, the compressibility, stable solute gradient, magnetic field, and couple-stress postpone the onset of convection whereas medium permeability hastens the onset of convection. Graphs have been plotted by giving numerical values to the parameters to depict the stability characteristics. The stable solute gradient and magnetic field introduce oscillatory modes in the system, which were non-existent in their absence. A condition for the system to be stable is obtained by using the Rayleigh-Ritz inequality. The sufficient conditions for the non-existence of overstability are also obtained.

scholarly journals Computation of electroconductive gyrotactic bioconvection under nonuniform magnetic field: Simulation of smart bio-nanopolymer coatings for solar energy

2020 ◽  
Vol 34 (05) ◽  
pp. 2050028 ◽  
Author(s):  
Madhu Aneja ◽  
Sapna Sharma ◽  
Sireetorn Kuharat ◽  
O. Anwar Beg
Keyword(s):  
Magnetic Field ◽  
Nusselt Number ◽  
Brownian Motion ◽  
Differential Equations ◽  
Sherwood Number ◽  
Nonuniform Magnetic Field ◽  
Ohmic Dissipation ◽  
Local Skin ◽  
Brownian Motion And Thermophoresis ◽  
Micro Organisms

The water-based bioconvection of a nanofluid containing motile gyrotactic micro-organisms (moves under the effects of gravity) over a nonlinear inclined stretching sheet in the presence of a nonuniform magnetic field has been investigated. This regime is encountered in the bio-nanomaterial electroconductive polymeric processing systems currently being considered for third-generation organic solar coatings, anti-fouling marine coatings, etc. Oberbeck–Boussinesq approximation along with ohmic dissipation (Joule heating) is considered in the problem. The governing equations of the flow are nonlinear partial differential equations and are converted into ordinary differential equations via similarity transformations. These equations are then solved by the Finite Element Method. The effect of various important parameters on nondimensional velocity, temperature distribution, nanoparticle concentration, the density of motile micro-organisms is analyzed graphically in detail. It is observed from the obtained results that the flow velocity decreases with rising angle of inclination [Formula: see text] while temperature, nanoparticle’s concentration and density of motile micro-organisms increase. The local skin friction coefficient, Nusselt number, Sherwood number, motile micro-organism’s density number are calculated. It is noticed that increasing the Brownian motion and thermophoresis parameter leads to an increase in temperature of fluid which results in a reduction in Nusselt number. On the contrary, the Sherwood number rises with an increase in Brownian motion and thermophoresis parameter. Also, interesting features of the flow dynamics are elaborated and new future pathways for extension of the study identified in bio-magneto-nano polymers (BMNPs) for solar coatings.

The Effect of Local Thermal Nonequilibrium on the Onset of Convection in a Nanofluid

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
D. A. Nield ◽  
A. V. Kuznetsov
Keyword(s):  
Heat Capacity ◽  
Brownian Motion ◽  
Small Particle ◽  
Lewis Number ◽  
Horizontal Layer ◽  
Onset Of Convection ◽  
Thermal Nonequilibrium ◽  
Capacity Ratio ◽  
Brownian Motion And Thermophoresis ◽  
Local Thermal Nonequilibrium

The onset of convection in a horizontal layer of a nanofluid is studied analytically. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis, and allows for local thermal nonequilibrium (LTNE) between the particle and fluid phases. The analysis reveals that in some circumstances, the effect of LTNE can be significant, but for a typical dilute nanofluid (with large Lewis number and with small particle-to-fluid heat capacity ratio), the effect is small.

The Onset of Convection in an Internally Heated Nanofluid Layer

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
D. A. Nield ◽  
A. V. Kuznetsov
Keyword(s):  
Brownian Motion ◽  
Boundary Conditions ◽  
Microwave Heating ◽  
Chemical Reaction ◽  
Vertical Gradient ◽  
Horizontal Layer ◽  
Internal Heating ◽  
Onset Of Convection ◽  
Brownian Motion And Thermophoresis ◽  
Heating From Below

We analytically studied the onset of convection, induced by internal heating, such as that produced by microwave heating or chemical reaction, in a horizontal layer of a nanofluid subject to Brownian motion and thermophoresis. This is a fundamentally different situation from traditionally studied heating from below. Convection, when it occurs, is now concentrated in the portion of the layer where the upward vertical gradient is negative, which is the upper portion of the layer. The situation of internal heating also allows employing more realistic boundary conditions than those hitherto used.

scholarly journals Hall Effect on Bénard Convection of Compressible Viscoelastic Fluid through Porous Medium

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Mahinder Singh ◽  
Chander Bhan Mehta
Keyword(s):  
Magnetic Field ◽  
Porous Medium ◽  
Thermal Instability ◽  
Linear Stability Theory ◽  
Stationary Convection ◽  
Onset Of Convection ◽  
Medium Permeability ◽  
Rayleigh Numbers ◽  
The Magnetic Field ◽  
Mode Technique

An investigation made on the effect of Hall currents on thermal instability of a compressible Walter’s B′ elasticoviscous fluid through porous medium is considered. The analysis is carried out within the framework of linear stability theory and normal mode technique. For the case of stationary convection, Hall currents and compressibility have postponed the onset of convection through porous medium. Moreover, medium permeability hasten postpone the onset of convection, and magnetic field has duel character on the onset of convection. The critical Rayleigh numbers and the wave numbers of the associated disturbances for the onset of instability as stationary convection have been obtained and the behavior of various parameters on critical thermal Rayleigh numbers has been depicted graphically. The magnetic field, Hall currents found to introduce oscillatory modes, in the absence of these effects the principle of exchange of stabilities is valid.

scholarly journals Double-Diffusive Convection of Synovial (Couple-Stress) Fluid in the Presence of Hall Current Through a Porous Medium

2018 ◽  
Vol 23 (4) ◽  
pp. 963-976
Author(s):  
M. Singh
Keyword(s):  
Magnetic Field ◽  
Porous Medium ◽  
Synovial Fluid ◽  
Couple Stress ◽  
Hall Current ◽  
Couple Stress Fluid ◽  
Double Diffusive Convection ◽  
Onset Of Convection ◽  
Diffusive Convection ◽  
Double Diffusive

Abstract An investigation made on the effect of Hall currents on double-diffusive convection of a compressible synovial (couple-stress) fluid in the presence of a horizontal magnetic field through a porous layer is considered. The analysis is carried out within the framework of linear stability theory and normal mode technique. A dispersion relation governing the effects of viscoelasticity, compressibility, magnetic field and porous layer is derived. For the stationary convection, a synovial fluid behaves like an ordinary Newtonian fluid due to the vanishing of the viscoelastic parameter. The stable-solute gradient, compressibility, and magnetic field have postponed the onset of convection, whereas Hall currents and medium permeability have not postponed the onset of convection, moreover, a synovial fluid has a dual character in the presence of Hall currents, whereas in the absence of Hall current in synovial fluid have postponed the onset of convection, which is in contrast in case of thermal convection couple-stress fluid with same effects. These analytic results are confirmed numerically and the effects of various parameters are depicted graphically. It has been observed that oscillatory modes are introduced due to the presence of viscoelasticity, magnetic field, porous medium and Hall currents which were non- existent in their absence. The sufficient conditions for the non-existence of overstability are also obtained.

scholarly journals Linear Stability Effect of Densely Distributed Porous Medium and Coriolis Force on Soret Driven Ferrothermohaline Convection

2018 ◽  
Vol 23 (4) ◽  
pp. 911-928
Author(s):  
R. Sekar ◽  
D. Murugan
Keyword(s):  
Porous Medium ◽  
Stability Analysis ◽  
Linear Stability ◽  
Normal Mode ◽  
Coriolis Force ◽  
Linear Stability Analysis ◽  
Stationary Convection ◽  
Onset Of Convection ◽  
Stability Effect ◽  
Mode Technique

Abstract The effect of Coriolis force on the Soret driven ferrothermohaline convection in a densely packed porous medium has been studied. A linear stability analysis is carried out using normal mode technique. It is found that stationary convection is favorable for the Darcy model, therefore oscillatory instability is studied. A small thermal perturbation is applied to the basic state and linear stability analysis is used for which the normal mode technique is applied. It is found that the presence of a porous medium favours the onset of convection. The porous medium is assumed to be variable and the effect of the permeable parameter is to destabilize the system. The present work has been carried out both for oscillatory as well as stationary instabilities. The results are depicted graphically.

Sign in / Sign up

Export Citation Format

Share Document