Presence Of Soret Effect Research Articles

Double-diffusive natural convection study in a shallow horizontal porous layer filled with a binary fluid and submitted to destabilized conditions in the presence of Soret effect

This paper reports an analytical and numerical study of thermosolutal convection in a Brinkman horizontal porous layer saturated with a binary mixture, destabilized by submitting it either to both heat and mass fluxes (a=0, with Soret effect) or only to a heat flux to recover the case of pure Soret effect (a=1). The analytical solution is derived based on the parallel flow approximation and validated numerically using a finite difference method. A good agreement is found between the predictions of the parallel flow approximation and the numerical results obtained by solving the full governing equations. The governing parameters of this study are the Lewis number, Le, the Rayleigh thermal, RT, the Soret number, Sr, and the buoyancy ratio, φ. The thresholds for the onset of convection and the generated heat and mass transfer rates are examined both in the presence (a=0) and in the absence (a=1) of an external mass flux. The influence of the governing parameters on the onset of motion and the resulting fluid flow, temperature and concentration fields is discussed. It was found that the onset of convection for a=0 and positive values of Sr is delayed compared to the case a=1 (pure Soret effect) and, for the latter case, the onset of convection is delayed compared to a=0 and negative values of the Soret number.

Heat source and radiation absorption on unsteady MHD fluid flow over an infinite vertical plate embedded in a porous medium in presence of Soret effect

In this paper, an investigation on the heat source and radiation absorption on MHD fluid flow past an accelerated vertical plate embedded in a porous medium with variable thermal diffusion are carried out. The dimensionless governing equations are solved using closed form of Laplace transformation technique. The velocity, temperature, concentration profiles, Nusselt number and Sherwood number are graphically interpreted to various physical parameters like thermal Grashof number, time, Accelerating parameter, Prandtl number and Permeability parameter, Magnetic parameter, Schmidt number, Mass Grashof number and Soret number etc. It has been found that velocity, concentration and Nusselt number rise with the increasing Prandtl number. Further, temperature and Sherwood number decreases with increment in Prandtl number.

Soret, heat generation, radiation and porous effects on MHD free convection flow past an infinite plate with oscillating temperature

The magnetohydrodynamic flow of a viscous incompressible fluid past an infinite vertical plate surrounded by a porous medium has been analytically investigated during natural convection. The heat and mass transfer characteristics are examined in the presence of heat generation, chemical reaction, thermal radiation, and Soret effect. An oscillating temperature of the plate is considered about a constant mean temperature. The Laplace transform technique is applied to solve the governing system of coupled partial differential equations. The concentration, velocity, penetration distance, skin-friction, Nusselt number, and Sherwood number results are obtained from the solutions and thoroughly discussed. The results exhibit that the velocity and the penetration distance enhance with an increase in Soret number, whereas the skin-friction decreases with increasing Soret number. The heat transfer rate enhances with the escalation of radiation parameter but diminishes with the increase of phase angle. It is also seen that the rate of mass transfer is occurring from fluid to the plate surface in the presence of Soret effect and surface temperature oscillations.

Steady MHD Casson Ohmic heating and viscous dissipative fluid flow past an infinite vertical porous plate in the presence of Soret, Hall, and ion‐slip current

AbstractIn the present study, the influence of Hall and ion‐slip current on steady magnetohydrodynamics mixed convective, Ohmic heating, and viscous dissipative Casson fluid flow over an infinite vertical porous plate in the presence of Soret effect and chemical reaction are investigated. The modeling equations are transformed into dimensionless equations and then solved analytically through the multiple regular perturbation law. Computations are performed graphically to analyze the behavior of fluid velocity, temperature, concentration, skin friction, Nusselt number, and Sherwood number on the vertical plate with the difference of emerging physical parameters. This study reflects that the incremental values of Casson fluid parameter and Schmidt number lead to reduction in velocity. However, fluid velocity rises due to enhancement of ion‐slip parameter but an opposite effect is observed in case of Hall parameter. In addition, the Sherwood number declines with enhancing dissimilar estimators of the chemical reaction, Schmidt number, as well as Soret number.

MHD dissipative fluid past a stretching sheet in the presence of Soret effect with Newtonian convective heat and mass conditions

AbstractThis article deliberates a theoretical study on a two‐dimensional magnetohydrodynamic free convection flow of an electrically conducting, heat generation/absorption fluid flowing past a linearly stretching sheet, placed vertical in a non‐Darcian porous medium with Soret effect. As the magnetic Reynolds number of the flow field considered very small (due to noncomparability of the induced and applied magnetic fields), the influence of the induced magnetic field is thus neglected. Again due to weak applied voltage differences at the lateral ends, the influence of the electric current is also ignored. A homotopy analysis method is developed to solve the similarity transformed equations subject to a set of convective heat and mass boundary conditions. Numerical data simulations are made on various fluid variables by using some practical/selected values of the governed parameters and illustrated through graphs and tables. It is found that the Newtonian heating parameter enhanced the velocity, temperature, and concentrations, while the solutal Newtonian heating parameter accelerates the rate of flow of heat and masses but minimizes the temperature gradient. The local Forchheimer and dissipation parameters are found to raise the temperature and concentrations, while the flow rate accelerates due to dissipation parameter but decelerates in presence of Forchheimer parameter.

Double-diffusive natural convection in an inclined enclosure with heat generation and Soret effect

PurposeThe purpose of this paper is to study numerically thermosolutal natural convection within an inclined rectangular cavity in the presence of Soret effect and heat generation. The enclosure is heated and salted from its long sides with constant but different temperatures and concentrations. The study focuses on the effects of three main parameters which are, the Soret parameter (Sr = 0 and –0.5), the internal to external Rayleigh numbers ratio 0 ≤ R ≤ 80 and the cavity inclination γ, varied from 0° (vertical position) to 60°. The combined effects of these parameters on fluid flow and heat and mass transfer characteristics are examined for the external Rayleigh number RaE = 105, the Prandtl number Pr = 0.71, the buoyancy ratio N = 1, the Lewis number Le = 2 and the aspect ratio of the cavity A = 2.Design/methodology/approachA hybrid lattice Boltzmann-finite difference method (LBM-FD) was used to tackle the problem under consideration. The LBM with the simple relaxation time was used for the fluid flow in the presence of the gravity force, while the temperature and concentration equations were solved separately using an explicit finite-difference technique at the Boltzmann scale.FindingsThe monocellular nature of the flow, obtained for R = 0 is not destroyed by varying the cavity inclination and the Soret parameter but rather by the increase of the parameter R. The Soret parameter and the cavity inclination become perceptible at high values of R. The inclination γ = 60° leads to high mean temperatures compared to the other inclinations. The effect of R on mean concentration is amplified in the presence of Soret effect but limited in the absence of the latter. The negative Soret parameter combined with high internal heat generation and a relatively high inclination is important when the objective is to maintain the fluid at a high concentration of species. The presence of bicellular flow combined with the important elevation undergone by the fluid temperature, makes both the cold and hot walls playing a cooling role with the most important exchanges taking place at the upper part of these walls. The analysis of the mean mass transfer shows that the increase of the inclination may lead to an increase or a decrease of the mass transfer depending on the range of R, in the case of Sr = 0. However, for Sr = −0.5, it is observed that the increase of γ is generally accompanied by a reduction of the mass transfer.Originality/valueTo the best of the authors’ knowledge, the hybrid LBM-FD was not used before to study such a problem. Combined effect of R and inclination may be useful in charging the fluid with species when the objective is to maintain high concentrations in the medium.

Hybrid lattice Boltzmann finite difference simulation of Soret convection flows in a square cavity with internal heat generation

Thermosolutal natural convection heat and mass transfer in a 2D square cavity are studied numerically in the presence of Soret effect and uniform volumetric heat generation. A hybrid scheme with simple relaxation time lattice Boltzmann method (SRT-LBM) is used to obtain the velocity field while the temperature and concentration fields are deduced from energy and species balances using a finite difference method (FDM). The study focuses on the effect of three parameters, which are the Soret parameter (, 0, and 0.5), the buoyancy ratio ( and 1), and the internal to external Rayleigh numbers ratio (). Combined effects of these parameters on fluid flow and heat and mass transfer characteristics are examined for Lewis number Le =2, Prandtl number , and external Rayleigh number . The interaction between the heat generation and the thermodiffusion may play an important role in purifying/charging the confined fluid from/with species by considering positive/negative values of .

English

English

Non-similarity solution for Soret effect on natural convection over the vertical frustum of a cone in a nanofluid using new bivariate pseudo-spectral local linearisation method

In this paper, we present a numerical investigation of a highly coupled and nonlinear system of partial differential equations (PDEs) that model natural convection over the vertical frustum of a cone in a nanofluid in the presence of Soret effect. The system of PDEs are solved using a new numerical approach named as bivariate pseudo-spectral local linearisation method (BPSLLM). The solution method uses the so-called quasilinearisation method to linearise the equations in a sequential manner and applies spectral collocation to discretise all independent variables. To test the accuracy of the proposed method, error analysis and convergence tests are conducted. Further, the accuracy validation is conducted through comparison with asymptotic series solutions for limiting cases of small and large parameters. In order to unravel the interesting features of the problem, the effects of the physical parameters on skin-friction, heat, regular mass and nanoparticle mass transfer characteristics along the vertical frustum of a cone are given and the salient features are discussed.

Role of thermal diffusion on double-diffusive natural convection in a vertical annular porous medium

Abstract This paper derives analytical solutions of fully developed natural convection heat and mass transfer in a vertical annular non-Darcy porous medium. This investigation extends the work of Cheng (2006) to a situation where Soret effect is present and the flow is both aided and opposed. The influence of the controlling parameters on the flow characteristics has been seen to be higher for double diffusion in the absence of Soret effect than in the presence of Soret effect. It is found that the presence of Soret effect reduces the dependence of the volume flow rate, the total heat rate and the total species rate on the inner radius-gap ratio and on the modified Darcy number.

Linear Stability Analysis of Double Diffusive Convection in a Horizontal Sparsely Packed Rotating Anisotropic 1 Porous Layer in Presence of Soret Effect

In this paper, we have investigated theoretically the effect of Soret parameter on the onset of double diffusive rotating anisotropic convection in a horizontal sparsely packed porous layer using linear stability theory which is based on the usual normal mode technique. The Brinkman model that includes the Coriolis term is employed for the momentum equation. The effect of anisotropy parameters, Soret parameter, solute Rayleigh number, Taylor number, Lewis number, Darcy and Darcy Prandtl number on stationary and oscillatory convection is shown graphically.

Subcritical convection in the presence of Soret effect within a horizontal porous enclosure heated and salted from the short sides

PurposeThe purpose of this paper is to study analytically and numerically the Soret effect on double diffusive natural convection induced in a horizontal Darcy porous layer subject to lateral heat and mass fluxes. The work focuses on the particular situation where the solutal to thermal buoyancy forces ratio, N, is related to the Soret parameter, SP, by the relation. For this particular situation, the rest state is a solution of the problem. The analytical identification of the parallel flow bifurcations counts among the objectives of the study. The effect of the governing parameters on the fluid flow properties and heat and mass transfer characteristics is also examined.Design/methodology/approachBoth the Darcy model and the Boussinesq approximation are used for the mathematical formulation of the problem. The geometry under study is a horizontal porous cavity filled with a binary fluid. The problem is solved analytically on the basis of the parallel flow approximation, valid in the case of a shallow cavity. The analytical results are validated numerically using a second‐order finite difference method.FindingsThe main finding is the absence of a supercritical bifurcation for this problem. More precisely, in the studied case, only the subcritical convection was found possible for the parallel flow structure and its threshold was determined analytically versus the governing parameters. It is also shown that the SP‐Le plane can be divided into two parallel flow regions; in one region the flow is counterclockwise while it is clockwise in the other. At sufficiently large values of RT, two solutions of ψ0, termed as “stable” and “unstable” and varying, respectively, as RT1/3 and RT−1 were obtained. The flows corresponding to these solutions are rotating in the same direction with different intensities. An analytical expression is established for the critical Rayleigh number which allows a control of the onset of motion in the system.Practical implicationsThe thermodiffusion phenomenon in saturated porous geometries is of practical interest in several natural and technological processes such as the migration of moisture through air contained in fibrous insulations, food processing, contaminant transport in ground water, electrochemical processes, etc.Originality/valueThe study concerns the Soret effect within a system subject to outside mass flux. Only one type of bifurcation (subcritical bifurcation) was found possible for the parallel flow structure in the present configuration instead of two kinds of bifurcations (supercritical and subcritical).

Marangoni Convection inWater-Isopropanol Mixtures in the Presence of Soret Effect

Marangoni Convection inWater-Isopropanol Mixtures in the Presence of Soret Effect

Thermo-Solutal Convection in Water Isopropanol Mixtures in the Presence of Soret Effect

Thermo-Solutal Convection in Water Isopropanol Mixtures in the Presence of Soret Effect

Multiplicity of Solutions Induced by Thermosolutal Convection in a Square Porous Cavity Heated from Below and Submitted to Horizontal Concentration Gradient in the Presence of Soret Effect

ABSTRACT Soret effect on fluid flow and heat and mass transfer induced by double-diffusive natural convection in a square porous enclosure, submitted to cross gradients of temperature and concentration, is studied numerically. The cavity is heated from below and cooled from the top, while its vertical walls are adiabatic and maintained at constant but different concentrations. Numerical results are presented for governing parameters varying in the following ranges: 40 ≤ R T ≤ 1,000, Le = 10, − 0.2 ≤ N ≤ 0.2 and − 30 ≤ M ≤ 30, where R T , Le, N, and M are the thermal Rayleigh number, the Lewis number, the buoyancy ratio, and the Soret parameter, respectively. The effect of the buoyancy ratio and the Soret parameter on the maintenance and disappearance of the multiple steady-state solutions obtained in the case of purely thermal convection is analyzed. It is found that only one monocellular flow mode persists at large values of N (or − N), both in the presence and in the absence of the Soret effect. Some flow modes are destroyed by the solutal buoyancy forces in the absence of the Soret effect (M = 0) but reappear in some range of the parameter M. The Soret effect may affect considerably the heat and mass transfer in the medium; it leads to an enhancement or to a reduction of the mass transfer, depending on the flow structure and the sign of M. There are situations where a solution transfers the solute toward the wall with the highest concentration. Such behavior is observed when the temperature gradient and the magnitude of the Soret parameter M are such that the thermodiffusion flux opposes and overcomes the convection flux, resulting in a net mass flux directed from the least concentrated wall toward the most concentrated one.

Long-wave Marangoni instability in a binary-liquid layer with deformable interface in the presence of Soret effect: Linear theory

We investigate the long-wave Marangoni instability in a binary-liquid layer in the limit of a small Biot number B. The surface deformation and the Soret effect are both taken into account. It is shown that the problem is characterized by two distinct asymptotic limits for the disturbance wave number k, k∼B1∕4 and k∼B1∕2, which are caused by the action of two instability mechanisms, namely, the thermocapillary and solutocapillary effects. The asymptotic limit of k∼B1∕2 is novel and is not known for pure liquids. A diversity of instability modes is revealed. Specifically, a new long-wave oscillatory mode is found for sufficiently small values of the Galileo number.

3D numerical simulations of thermodiffusion experiment for a ternary mixture on-board foton

The phenomenon of mass flux in a mixture due to a temperature gradient is known as the Soret effect. Accurate experimental and theoretical models are needed for a better understanding and effective characterisation of situations involving coupled transport processes as in hydrocarbon reservoirs. This requires precise knowledge of the transport coefficients particularly the Fick and Soret diffusion coefficients. We have investigated the effect of residual-g and (very) low-frequency g-jitters encountered on-board spacecraft FOTON on mass-thermo-fluid dynamics in the presence of Soret effect. Results revealed that the diffusion process is slightly affected by the g-jitter on board the FOTON platform, which indicates that FOTON is a good platform to conduct near perfect microgravity environment.

Soret driven thermosolutal convection in a shallow porous layer with a stress‐free upper surface

PurposeThermodiffusion or Soret effect is a phenomenon that can be encountered in many applications. However only little is known about this phenomenon, particularly in the case of sparsely packed media (i.e. Brinkman media). The aim of this paper is to study numerically and analytically the effect of thermodiffusion on the onset of natural convection in a horizontal Brinkman porous layer with a free‐stress upper boundary.Design/methodology/approachThe study is performed by solving numerically the governing equations for different combinations of the governing parameters. An analytical solution is also developed in the case of a shallow layer using the approximation of a parallel flow in the core region to predict the critical conditions corresponding to the onset stationary, subcritical and Hopf convection.FindingsThe results obtained show that, in the presence of Soret effect, the numerical and analytical solutions agree well for long enough layers. The thermodiffusion parameter can affect considerably the supercritical and sub‐critical Rayleigh numbers and heat and mass transfer characteristics in the layer. It is also shown that the plane Le‐φ can be divided into three main regions with specific and different behaviours.Originality/valueThe Soret effect can play a stabilizing or a destabilizing role and this, depending on the sign of the separation parameter, φ.

Technical Note Marangoni instability of a layer of binary liquid in the presence of nonlinear Soret effect

Although the Soret effect induces only small chemical separations, its influence on the variations of physical parameters may be larger than the influence of the thermal gradient from which it results. The effect has been recognized and extensively studied in the Rayleigh–Bénard problem for instabilities generated by density fluctuations [1–4] . In the same way that for the mixture density, the Soret effect may influence significantly the surface tension variations in the presence of a temperature gradient. The interaction between thermocapillary and concentration-capillary mechanisms for promoting motion in binary mixture fluids has motivated many authors to study the Marangoni–Bénard instability in the presence of the Soret effect and important similarities with the Rayleigh–Bénard convection have been evidenced [5] .