Presence Of Thermal Diffusion Research Articles

Synchronization of optically self-assembled nanorotors.

Self-assembly of nanoparticles by means of interparticle optical forces provides a compelling approach toward contact-free organization and manipulation of nanoscale entities. However, exploration of the rotational degrees of freedom in this process has remained limited, primarily because of the predominant focus on spherical nanoparticles, for which individual particle orientation cannot be determined. Here, we show that gold nanorods, which self-assemble in water under the influence of circularly polarized light, exhibit synchronized rotational motion at kilohertz frequencies. The synchronization is caused by strong optical interactions and occurs despite the presence of thermal diffusion. Our findings elucidate the intricate dynamics arising from the transfer of photon spin angular momentum to optically bound matter and hold promise for advancing the emerging field of light-driven nanomachinery.

Heat and Mass Transfer Analysis in An Unsteady Natural Convective Magnet Hydrodynamic Flow of a Nano Fluid under the Presence of Thermal Diffusion and Absorption Radiation

An analysis of unsteady natural convective MHD flow of nanofluid under the presence of thermal diffusion and absorption radiation with the effects of chemical reaction on heat and mass transfer without a porous medium is discussed in the present study. The governing equations were implied and were solved analytically using perturbation technique. The velocity, temperature and concentration fields are obtained. Graphical results were presented for velocity, temperature and concentration profile for various values of parameters.

Characteristics of MHD nanofluid flow towards a vertical cone under convective cross‐diffusion effects through numerical solutions

AbstractIn this study, the aim is to find the numerical solutions of steady, two‐dimensional, incompressible, viscous, electrically conducting magnetohydrodynamic (MHD) boundary‐layer nanofluid flow towards a vertical cone in the presence of thermal diffusion, diffusion thermo, thermophoresis, and Brownian motion effects subject to porous medium and convective boundary condition. For this investigation, the method of similarity transformations is used for the objective of converting nonlinear partial differential equations into the system of ordinary differential equations. Approximate solutions are obtained using a numerical method of the Runge–Kutta method with the shooting technique for the flow, heat, and mass transfer equations together with boundary conditions. For this flow, the impact of various engineering parameters on MHD, thermal, and solutal boundary layers is investigated and the results are displayed graphically. In addition, the numerical values of the local skin‐friction coefficient, rate of heat transfer, and rate of mass transfer coefficients are calculated, and the results are presented numerically. Finally, the comparison with previously published work is made and found in good agreement.

Numerical study on thermal enhancement in magnetohydrodynamic micropolar liquid subjected to motile gyrotactic microorganisms movement and Soret and dufour effects

Motile gyrotactic organism activity in micropolar fluid subjected to simultaneous heat and mass transfer in the presence of thermal diffusion and diffusion thermo effects is modeled. The base fluid is taken as kerosene oil. The immersion of nano-sized particles of C u − T i O 2 kerosene oil makes its rheological characteristics of micropolar fluid because nano-sized particles serve as micro-structures. In this case couple stress, vortex and spin gradient viscosities become significant and simultaneously linear and angular momenta become equally remarkable. So, micropolar theory is the best to model the immersion of nano-structures in the fluid. Similarity variables are used to transform the problems into their dimensionless forms. The mathematical models are solved numerically by applying the finite element method (FEM). The results are validated and numerical experiments are performed to analyze the key parameters of the unknown field variables. In order to analyze the impact of physical parameters on field variables, numerous simulations are performed. The micro-rotation of microparticles and nanoparticles due to fluid deformation motivates fluids particles to rotate faster. Therefore, linear motion is observed to be increased for higher values of vortex viscosity. The curvature parameter has significantly impacted the linear motion of the fluid particles. The impact of the curvature parameter on the movement of nanofluid is lesser than the impact of the curvature parameter on the motion of hybrid nanoparticles. Concentration gradient supports the diffusion of heat in the fluid regime and numerical experiments with variation of Dufour (that measures the effects of concentration gradient on heat diffusion) have shown that concentration gradient is more effective in the case of hybrid nanofluid relative to the mono nanofluid. The angular motion of fluid particles increases when vortex viscosity is increased. Numerical simulations have predicted that the angular motion of particles of hybrid nanofluid has a lesser angular speed than that of the angular motion of particles of mono nanofluid. The Soret number determines the impact of temperature gradient on the diffusion of solute in the fluid. Simulations for various values of Soret number have predicted that the impact of temperature gradient on the diffusion of solute in hybrid nanofluid is stronger than the impact of temperature gradient on the diffusion of solute in mono nanofluid.

Transient MHD convective flow of a micropolar fluid past a moving vertical plate in the presence of thermal diffusion

AbstractIn this article, we investigate a transient magnetohydrodynamic convective micropolar fluid flow over a semi‐infinite vertical plate embedded in a porous medium in the presence of chemical reaction and thermal diffusion. The dimensionless governing equations are solved by adopting the regular perturbation technique. The impact of various parameters on the velocity, microrotation, temperature, concentration profiles, skin friction, Sherwood number, and Nusselt number over the boundary layer is analyzed using graphs. The fluid velocity and microrotation reduce under the effect of thermal diffusion and chemical reaction. Furthermore, concentration rises due to thermal diffusion (Soret) effect, but concentration falls under the effect of chemical reaction. It is found that the velocity and skin friction fall with enhancing value of magnetic parameter. But Sherwood number increases as the magnetic parameter increase.

Convective Heat and Mass Transfer in Third-Grade Fluid with Darcy–Forchheimer Relation in the Presence of Thermal-Diffusion and Diffusion-Thermo Effects over an Exponentially Inclined Stretching Sheet Surrounded by a Porous Medium: A CFD Study

The current study aims to investigate the thermal-diffusion and diffusion-thermo effects on heat and mass transfer in third-grade fluid with Darcy–Forchheimer relation impact over an exponentially inclined stretching sheet embedded in a porous medium. The proposed mechanism in terms non-linear and coupled partial differential equations is reduced to set of ordinary differential equations by employing an appropriate similarity variable formulation. The reduced form of equations is solved by using the MATLAB built-in numerical solver bvp4c. The numerical results for unknown physical properties such as velocity profile, temperature field, and mass concentration along with their gradients such as the skin friction, the rate of heat transfer, and the rate of mass transfer at angle of inclination α=π/6 are obtained under the impact of material parameters that appear in the flow model. The solutions are displayed in forms of graphs as well as tables and are discussed with physical reasoning. From the demonstration of the graphical results, it is inferred that thermal-diffusion parameter Sr velocity, temperature, and concentration profiles are augmented. For the increasing magnitude of the diffusion-thermo parameter Df the fluid velocity and fluid temperature rise but the opposite trend in mass concentration is noted. The current results are compared with the available results in the existing literature, and there is good agreement between them that shows the validation of the present study.

Impact of radiation and heat generation/absorption in a Walters’ B fluid through a porous medium with thermal and thermo diffusion in the presence of chemical reaction

ABSTRACT In this paper, the analytical technique is adopted to investigate the behaviours of the various patients in the non-Newtonian type model of a Walters’ B fluid through a porous medium with the interactive impact of thermal radiation, heat generation/absorption and diffusion thermo impact in the presence of thermal diffusion and chemical reaction. The highly nonlinear systems of equations responsible for the behaviours of the model are modified to the system of coupled nonlinear ordinary differential equations via the fluid variables. The converted equations are executed by Homotopy Analysis Method (HAM). The significance of magnetic parameter, local Weissenberg number as well as other parameters encountered are discussed accordingly. Among the major finding is the variation in thermal buoyancy parameter, which accelerates the motion of the fluid and cools the problem with a significant role of cooling of the system and other electronic panels in the science-related field while the quiescent-fluid gained thermal-effect on the account of the penetration of strong convective-heating for different values of convective-heat parameter which contributes to the drying of material components in technological-related disciplines.

Three‐dimensional flow past a porous vertical plate in a porous medium with sinusoidal suction and permeability in the presence of thermal diffusion

AbstractAn analytical solution, based on the asymptotic series expansion method, for the problem of a fully developed chemically reactive laminar three‐dimensional flow through a porous vertical infinite plate in a porous medium with sinusoidal permeability as suction in the existence of appreciable radiation is presented. The effects of the physical parameters entering into the problem on the flow and transport characteristics are studied and demonstrated through graphs. The flow is three‐dimensional due to sinusoidal suction as well as porosity. It is found that concentration of the fluid rises due to thermal diffusion (Soret) effect. Furthermore, it is seen that fluid velocity is increased for increasing thermal diffusion effect. Also, viscous drag at the plate is increased under the Soret effect.

Mixed Convection Flow of Viscous Reactive Fluids with Thermal Diffusion and Radial Magnetic Field in a Vertical Porous Annulus

This paper investigates the influence of the Frank–Kamenetskii, mixed convection, buoyancy force parameter, Soret effect, and radial magnetic field on steady-state fully developed free convection flow of viscous reactive fluids in the annular region between concentric cylinder r = 1 and r = b in the presence of thermal diffusion and radial magnetic field. The nonlinear ordinary differential equation governing the flow are solved using the semi-analytical method (perturbation series method). The solution obtained is graphically represented and the effect of various controlling pertinent parameters such as λ, Gre, N, Sr, and M on the flow formation is discussed. The physical quantities such as skin friction, Nusselt number and Sherwood number are also computed. It is interesting to observe that increasing the values of Frank–Kamenetskii (λ), mixed convection (Gre), and Soret (Sr) increases the velocity while increase in the radial magnetic field (M) decreases the velocity.

Unsteady MHD Mass Transfer Flow past a Temporarily Accelerated Semi-infinite Vertical Plate in Presence of Thermal Diffusion with Ramped Wall Temperature

Unsteady MHD Mass Transfer Flow past a Temporarily Accelerated Semi-infinite Vertical Plate in Presence of Thermal Diffusion with Ramped Wall Temperature

Impact of Brownian moment and thermophoresis on magnetohydrodynamic flow of magnetic nanofluid past an elongated sheet in the presence of thermal diffusion

Purpose The purpose of this paper is to report the impact of thermophoresis and Brownian moment on MHD two-dimensional forced convection flow of nanofluid past a permeable stretching sheet in the presence of thermal diffusion. Design/methodology/approach The flow governing PDEs are reduced to ODEs by utilizing pertinent transmutations and then resolved by employing a fourth-order Runge-Kutta-based shooting technique. The energy and diffusion equations are incorporated with Brownian motion, thermophoresis and Soret parameters. The velocity, thermal and concentration attributes along with skin friction factor, local Nusselt and Sherwood number are discussed under the influence of sundry pertinent parameters and presented with the assistance of graphical and tabular values. Findings The results infer that Sherwood number is accelerated by Soret parameter but it controls the thermal transport rate. And also, Brownian and thermophoresis play a vital role in enhancing heat conduction process. Originality/value Considering the industrial applications of flow of magnetic nanofluid over a stretching surface, this paper presents the solution of the flow problem considering thermophoresis, Brownian motion, magnetic field and thermal diffusion effects. In addition, the aim and objectives of this paper fills a gap in the industry.

Magneto-Convective Fluid Flow past an Exponentially Accelerated Vertical Porous Plate in the Presence of Thermal Diffusion

Magneto-Convective Fluid Flow past an Exponentially Accelerated Vertical Porous Plate in the Presence of Thermal Diffusion

UNSTEADY MHD HEAT AND MASS TRANSFER FLOW OF A RADIATING FLUID PAST AN ACCELERATED INCLINED POROUS PLATE WITH HALL CURRENT

In this paper an analysis has been performed to study the effects of Hall current and radiation of MHD free convective heat and mass transfer flow of a radiating fluid past an accelerated inclined porous plate with hall current in presence of thermal diffusion and heat source. The solutions for velocity, temperature and concentration distributions are obtained by using Laplace transform technique. The expressions for skin friction, Nusselt number and Sherwood number are also derived. The variations in fluid velocity, temperature and species concentration are shown graphically, whereas numerical values of skin friction, Nusselt number and Sherwood number are presented in tabular form for various values of physical parameters.

THERMAL DIFFUSION AND ROTATIONAL EFFECTS ON MAGNETO HYDRODYNAMIC MIXED CONVECTION FLOW OF HEAT ABSORBING/GENERATING VISCO- ELASTIC FLUID THROUGH A POROUS CHANNEL

This investigation presents an analytical study on magnetohydrodynamic (MHD), convective flow of a viscoelastic, incompressible, radiative, chemically reactive, electrically conducting and rotating fluid through a porous medium filled in a vertical channel in the presence of thermal diffusion. A magnetic field of uniform strength is applied along the axis of rotation. The fluid is assumed to act on with a periodic time variation of the pressure gradient in upward direction vertically. One of the plates is maintained at non-uniform temperature and the temperature difference of the walls of the channel is assumed high enough that induces heat transfer due to thermal radiation. The analytical solutions are obtained for velocity, temperature and concentration, by solving the dimensionless governing equations using regular perturbation technique. To assess the effects of various parameters involved in the model, two cases of small and large rotations have been considered. Effects of various parameters involved in velocity, temperature, species concentration distributions and the corresponding amplitude and the phase angle of the skin friction, Nusselt number and Sherwood number are shown graphically and discussed in detail.

Numerical investigation of MHD free convection flow of a non-Newtonian fluid past an impulsively started vertical plate in the presence of thermal diffusion and radiation absorption

A numerical investigation is carried out on an unsteady MHD free convection flow of a well-known non-Newtonian visco elastic second order Rivlin-Erickson fluid past an impulsively started semi-infinite vertical plate in the presence of homogeneous chemical reaction, thermal radiation, thermal diffusion, radiation absorption and heat absorption with constant mass flux. The presence of viscous dissipation is also considered at the plate under the influence of uniform transverse magnetic field. The flow is governed by a coupled nonlinear system of partial differential equations which are solved numerically by using finite difference method. The effects of various physical parameters on the flow quantities viz. velocity, temperature, concentration, Skin friction, Nusselt number and Sherwood number are studied numerically. The results are discussed with the help of graphs. We observed that the velocity decreases with an increase in magnetic field parameter, Schmidt number, and Prandtl number while it increases with an increase in Grashof number, modified Grashof number, visco-elastic parameter and Soret number. Temperature increases with an increase in radiation absorption parameter, Eckert number and visco-elastic parameter while it decreases with increasing values of radiation parameter, Prandtl number and heat absorption parameter. Concentration increases with increase in Soret number while it decreases with an increase in Schmidt number and chemical reaction parameter.

Thermal diffusion and chemical reaction effects on unsteady flow past a vertical porous plate with heat source dependent in slip flow regime

The present study investigates an analytical solution of free convective unsteady fluid flow in presence of thermal diffusion and chemical reaction effects past a vertical porous plate with heat source dependent in slip flow regime. The plate is assumed to move with a constant velocity in the direction of fluid flow, while free stream velocity is assumed to follow exponentially increasing small perturbation law. The velocity, temperature and concentration profiles are presented graphically for different values of the parameters entering into the problem. Finally the effects of pertinent parameters on the skin friction coefficient, Nusselt number and Sherwood numbers distributions are derived and have shown through graphs and tables by using perturbation technique.

Unsteady MHD Heat And Mass Transfer Flow Of A Radiating Fluid Past An Accelerated Inclined Porous Plate With hall Current

An analysis has been carried out to study the effects of Hall current and radiation of MHD free convective heat and mass transfer flow past an accelerated inclined plate with temperature and concentration in a porous medium in presence of thermal diffusion and heat source. The solutions for velocity field, temperature field and concentration distribution are obtained using Laplace transform technique. The expressions for skin friction, Nusselt number and Sherwood number are also derived. The variations in fluid velocity, fluid temperature and species concentration are shown graphically, whereas numerical values of skin friction, Nusselt number and Sherwood number are presented in tabular form for various values of physical parameters.

The convective stability of fully stratified baroclinic discs

We examine the convective stability of hydrodynamic discs with full stratification in the local approximation and in the presence of thermal diffusion (or relaxation). Various branches of the relevant axisymmetric dispersion relation derived by Urpin (2003) are discussed. We find that when the vertical Richardson number is larger than or equal to the radial one (i.e. $|Ri_z|\geq|Ri_x|$) and wavenumbers are comparable (i.e. $|k_x|\sim|k_z|$) the disc becomes unstable, even in the presence of radial and vertical stratifications with $Ri_x>0$ and $Ri_z>0$. The origin of this resides in an hybrid radial-vertical Richardson number. We propose an equilibrium profile with temperature depending on the radial and vertical coordinates and with $Ri_z>0$ for which this destabilization mechanism occurs. We notice as well that the dispersion relation of the "convective overstability" is the branch of the one here discussed in the limit $|k_z|\gg|k_x|$ (i. e. two-dimensional disc).

Heat and Mass Transfer on MHD Viscoelastic Fluid Flow in the Presence of Thermal Diffusion and Chemical Reaction

Heat and Mass Transfer on MHD Viscoelastic Fluid Flow in the Presence of Thermal Diffusion and Chemical Reaction

MHD Free-Convective and Mass Transfer Flow Past a Continuously Moving Semi-Infinite Vertical Porous Plate with Thermal Diffusion

A steady two dimensional MHD free convective and mass transfer flow of an incompressible fluid past a continuously moving vertical infinite porous plate in the presence of thermal diffusion has been studied. The governing partial differential equations of the MHD free convective boundary layer flow are reduced to nonlinear ordinary differential equations by introducing suitable similarity transformations. The nonlinear similarity equations are then solved numerically by Nachtshiem-Swigert iteration technique. The results of the numerical solution are then presented graphically in the form of velocity, temperature and concentration profiles. The corresponding skin friction coefficient, the Nusselt number and the Sherwood number are also calculated and displayed in tables showing the effects of various parameters on them.