Diffusive Convection Flow Research Articles

Numerical exploration of electroosmotically regulated squeezing rotating flow of TiO2/water nanofluid in a parallel plate channel under triple diffusion convection

The basic motive of this article gives a rudimentary insight into the triple diffusive convective flow of ionic aqueous solution-based titanium dioxide (TiO2) nanofluid amidst two rotating parallel plates. The lower plate is stationary and permeable, allowing the lateral suction/injection of the fluid, while the upper plate is impermeable and moves towards the lower plate. The fluid flow is explored under the simultaneous implementation of electric and magnetic forces. The presence of axial electric force across the plates with an ionic solution between them generates the electroosmotic phenomenon. The Oberbeck-Boussinesq approximation is utilized to include the solutal buoyancy forces occurring due to the concentration gradient of two different solutes. The appropriate similarity transformation is used to reform the governing equations which are resolved using the built-in numerical solver bvp4c of MATLAB. The computations reveal that velocity in the case of injective flow is larger than in the case of suction through the bottom plate. The forwarding electric field contributes to the primary velocity profile at the lower plate while velocity declines near the top plate. For solutes 1 and 2, the modified Dufour number and Dufour Lewis numbers have an opposing effect on the Nusselt number at the lower and upper plates.

Double Diffusive Convective Flow Study of a Hybrid Nanofluid in an Inverted T-Shaped Porous Enclosure Under the Influence of Soret and Dufour Prameters

Abstract This study presents a numerical investigation to examine the influence of Soret and Dufour parameters on the double-diffusive convective flow of a hybrid nanofluid within an inverted T-shaped porous enclosure. The thermophysical properties and numerical values of the hybrid nanofluid are adopted from experimentally published data. The mathematical model is formulated based on the generalized Darcy–Brinkmann–Forchheimer equation and subsequently simulated using the penalty finite element method. A parametric study is conducted, encompassing a wide range of parameters for Rayleigh number, Darcy number, porosity value, buoyancy ratio, Lewis number, Soret parameter, and Dufour parameter. The resulting flow patterns, temperature distribution (isotherms), and concentration distribution (isoconcentration plots) provide insights into the fluid flow, heat transfer, and mass transfer phenomena within the physical domain. Furthermore, the heat and mass transfer rates at the heated (concentrated) wall are quantitatively evaluated by the mean Nusselt number and mean Sherwood number, respectively, considering various combinations of flow parameters. As a key finding, it is observed that the smaller value of the Rayleigh number remains insignificant at convective flow of thermal and solute phenomena. Moreover, the higher value of Ra reinforces the convective strength of hybrid nanofluid, and it helps to identify the real impact of each parameter. Thus, at a higher Rayleigh number, it is observed that the increasing value of Darcy number, porosity value, Lewis number, and buoyancy ratio significantly influence the convective flow of heat and solute transport activity, whereas the impact of Soret and Dufour parameters shows a relatively less influence on the heat and mass transfer phenomena.

Buoyancy Effect on the Unsteady Diffusive Convective Flow of a Carreau Fluid Passed over a Coated Disk with Energy Loss

The unsteady flow of a Carreau fluid over a coated disk under the simultaneous effects of a thermal and concentration field with buoyancy forces is reported. The time-dependent diffusive stream of a Carreau fluid over a conducting coated disk is carried out with energy loss. The time-dependent partial differential equations are first converted into a scheme of ordinary differential equations by the appropriate transformations and are then solved by shooting method. Significant results for speed, hotness and concentration profiles are revealed and deliberated by the graphical outcomes. The numerical values of skin friction suggest that the viscoelastic parameter of the Carreau fluid causes a reduction in the skin friction coefficient due to the coated surface, but the Nusselt and Sherwood numbers increase with the rise of the viscoelastic parameter of the Carreau fluid because of the coated surface. The present model is useful in the field of mechanical engineering to design a tesla turbine for the flow of viscous fluid.

Chemical Reaction and Internal Heating Effects on the Double Diffusive Convection in Porous Membrane Enclosures Soaked with Maxwell Fluid.

In this paper, the joint impact of the interior heating and chemical reaction on the double diffusive convective flow in porous membrane enclosures soaked by a non-Newtonian Maxwell fluid is investigated applying linear and nonlinear stability techniques. The porous enclosures are square, slender and rectangular. Using the linear stability analysis, the expression for the critical thermal Rayleigh–Darcy number, above which the convective movement occurs, is derived analytically in terms of associated physical parameters. A nonlinear stability examination reliant on the Fourier double series is executed to calculate the convective heat and mass transports of the arrangement. It is observed that the pattern of convective activity is oscillatory only in the occurrence of a relaxation parameter and the threshold value of the relaxation parameter for the occurrence of the oscillatory pattern depends on the other physical parameters. The onset of convective instability accelerates with the increasing chemical reacting parameter, the interior heating parameter, the solute Rayleigh–Darcy number, the Lewis number, the Vadasz number, and the relaxation parameter, while it delays with the heat capacity ratio. The convective heat and mass transfers increase with the solute Rayleigh–Darcy number, the Vadasz number, the relaxation parameter, and the aspect ratio (for rectangular enclosure), while it decreases with the heat capacity ratio and the aspect ratio (for slender enclosure). Additionally, the convective heat transfer enhances with the interior heating parameter, while the convective mass transfer enhances with the chemical reacting parameter and the Lewis number. The effects of Vadasz number, heat capacity ratio, and relaxation parameter are witnessed only on the oscillatory pattern of convection and unsteady convective heat and mass transfers. Further, some existing literature results are compared with the current findings.

Structural stability for the Darcy model in double diffusive convection flow with Magnetic field effect

<abstract><p>In this paper, we consider the Darcy model with magnetic field affect which is used to describe the double diffusive flow of a fluid containing a solute. Using the energy estimate methods, we derive the prior bounds of the solutions. By using these a prior bounds, the continuous dependence of the solutions to Darcy model on the magnetic coefficient and the boundary parameter is established.</p></abstract>

Partial Slip Impact on Double Diffusive Convection Flow of Magneto-Carreau Nanofluid through Inclined Peristaltic Asymmetric Channel

The significance of partial slip on double diffusive convection on magneto-Carreau nanofluid through inclined peristaltic asymmetric channel is examined in this paper. The two-dimensional and directional flow of a magneto-Carreau nanofluid is mathematically described in detail. Under the lubrication technique, the proposed model is simplified. The solutions of extremely nonlinear partial differential equations are calculated using a numerical technique. Graphical data are displayed using Mathematica software and Matlab to examine how temperature, pressure rise, concentration, pressure gradient, velocity profile, nanoparticle volume fraction, and stream functions behave on emerging parameters. It is noticed that as the velocity slip parameter is increased, the axial velocity at the channel’s center increases. Additionally, near the boundary, opposite behavior is observed. The temperature, concentration, and nanoparticle profile drops by increasing thermal slip, concentration slip, and nanoparticle slip parameter.

Heatline and Massline Visualization of Hydromagnetic Double Diffusive Convective Flow of Nanofluid Within a Porous Trapezoidal Cavity

Double diffusive convective flow of nanofluid within a porous trapezoidal cavity of various aspect ratios consisting of Al2O3 nanoparticle in the presence of applied magnetic field in the direction perpendicular to the parallel top and bottom walls is analysed. The side walls of the cavity are maintained at constant temperature and concentration while its horizontal walls are insulated and impermeable. The irregular physical domain of the problem is transformed to a regular unit square computational domain. The governing equations have been solved by second order of finite difference method (FDM). Based upon numerical predictions, the effects of pertinent parameters such as Rayleigh number, Darcy number, aspect ratio, solid volume fraction and inclination angle on the flow and temperature fields and the heat transfer performance of the enclosure are examined. It is found that the intensity of heat and mass transfer increases with the increase in the Darcy number and aspect ratio. It is also observed that as the solid volume fraction increases there is increase in the average Nusselt number but reverse effect is observed on the average Sherwood number.

Irreversibility Analysis for Double Diffusive Convection Flow of a Gas Mixture in a Chamfered Corners Square Enclosure Filled with a Porous Medium

An analysis of thermodynamic irreversible principle (TPI), through determination of entropy generation rate, during double-diffusive convection in an octagonal shape, filled with saturated fluid in a porous enclosure, is numerically investigated in this work, by studying the influence of thermodiffusion effect on entropy generation variations. According to the fluid flow evolution under consideration, the influence of mass flux due to temperature gradient is incorporated into the governing equations of the problem, which are solved numerically, using the COMSOL software. Appropriated thermal and solutal Dirichlet boundary conditions are used under the Boussinesq approximation. For the porous medium, the Darcy–Brinkman model is assumed in coupling with energy and mass transfer balance equations. The flow model is described in terms of mass flux due to temperature gradient, buoyancy ratio, thermal Rayleigh number and porosity of the medium. Results of the variations of heat transfer and entropy generation in the studied enclosure are graphically illustrated and are basically discussed, through various physical aspects of the problem. The numerical computations are presented for various values of thermal Rayleigh number (RaT), thermal diffusion parameter (Kt), Darcy number (Da), buoyancy ratio (N) and porosity of the medium (e). In addition, the total entropy generation due to thermal, species and mixed diffusion gradients; Darcy–Brinkman dissipation; and fluid friction are studied and discussed. It is found that the entropy generation increases strongly when passing from the cooperative case of buoyancy forces to the opposite case. A similar behaviour is obtained with increasing the thermal diffusion ratio, at a constant buoyancy ratio. Also, an accentuated increase in entropy generation is observed when the Darcy number exceeds the value 10−6. Moreover, the results show that the augmentation of the thermodiffusion effect induces an increase in total entropy generation, at fixed value of the porosity.

Triple diffusive flow of nanofluid with buoyancy forces and nonlinear thermal radiation over a horizontal plate

AbstractThe present attempt is made to elaborate the features of triple diffusive convective flow of an incompressible nanoliquid induced by horizontal surface under buoyancy forces. The effect of nonlinear thermal radiation is taken into account. Heat flux model of radiation is formulated through Rosseland's approximation. The radiation phenomenon plays a key role in modern solar energy equipment's. The nondimensional variables are introduced to convert the dimensional mathematical expressions into dimensionless single independent variable. Numerical scheme is developed to obtain the solution of mathematical model. The importance of controlling constraints on flow quantities are characterized through plots. The quantities of engineering importance are computed and elaborated graphically. It is noticed that the presence of salts and nanoparticles enhance the thermal performance of base liquid. The liquid temperature and its relevant thickness of thermal layer improved significantly with an increment in the values of radiative parameter. The larger values of parameters of Brownian motion and thermophoretic correspond to higher temperature profiles.

Effects of variable viscosity and porosity of fluid, Soret and Dufour mixed double diffusive convective flow over an accelerating surface

Numerical computation has been carried out for the study of non-linear coupled partial differential equations for combined effects of Soret, Dufour and variable fluid properties like variable viscosity and variable permeability on thermal and diffusion mixed convection flow fluid through porous media over an accelerating surface. The study has been carried out for other additional terms like viscous dissipation and ohmic effect due to the presence of viscous and porous media. By applying the shooting method, we have drawn the numerical results for the flow characteristics like velocity, temperature and concentration for the Soret and Dufour effects on mixed( free and forced) convective flow for various non-dimensional parameters of the problem. Our computational results are compared with the earlier works in the absence of the additional terms and effects on the physical system and found to be good agreement.

Entropy generation due to double diffusive convective flow of Casson fluids over nonlinearity stretching sheets with slip conditions

The present paper deals with the effects of slip boundary conditions and chemical reaction on the heat and mass transfer by mixed convective boundary layer flow of a non-Newtonian fluid over a nonlinear stretching sheet. The Casson fluid model is used to characterize the non-Newtonian fluid behavior. First order chemical reactions are considered. Similar solutions are used to convert the partial differential equations governing the problem to ordinary differential equations. The velocity, temperature and concentration profiles are obtained, numerically, using the MATLAB function bvp4c and those are used to compute the entropy generation number. The effect of increasing values of the Casson parameter is found to suppress the velocity field and temperature distribution. But the concentration is enhanced with the increasing of Casson parameter. The viscous dissipation, temperature and concentration irreversibility are determined and discussed in details.

Acoustic remote sensing of double-diffusive instabilities and intrusions in ocean frontal zones

Small-wavelength sound has been observed to scatter from turbulent microstructure and plankton in the ocean. Additional scattering from salt fingers and diffusive-convective flows that result from double diffusive instabilities (DDI) is also theoretically possible in this same wavelength band, and has been measured in a laboratory setting, though with artificially high gradient parameters. If measurable, small-wavelength backscatter would enable remote sensing of water mass interleaving and mixing from intrusive flows at fronts, which spawn DDI. The factors controlling the visibility of echoes from DDI features is the strength of the features in terms of density and sound-speed anomaly, and the level of masking return from plankton, which may merely interfere or act as passive tracers of these features. Microstructure data collected in double-diffusive instability features are used to compute the expected monostatic backscatter signals. These results suggest that DDI microstructure, from both salt fingering and convection, would be acoustically observable in areas with low to average plankton. The results also suggest that density interfaces (layering structures) associated with DDI would be visible. Acoustic backscatter data show echoes from both the interfaces and DDI microstructure in a frontal zone across a range of wavelengths. [Work supported by the Office of Naval Research.]

지상 및 미소중력 환경에서 물리적 승화법 공정에 미치는 불순물의 영향 분석: 염화제일수은에 대한 응용성

본 연구에서는 지상 및 미소중력환경하에서 물리적 승화법 공정에서의 확산-대류유동에 미치는 불순물의 영향을 이론적으로 <TEX>$Hg_2Cl_2-I_2$</TEX> 시스템에 적용하여 규명하는 것이다. 이론적 해석은 증기상에서 확산-대류 흐름, 열 및 물질전달을 속도 벡터 흐름, 유선, 온도, 농도 분포를 통하여 제시된다. 결정 영역에서의 전체 몰플럭스는 중력가속도와 성분 <TEX>$I_2$</TEX>, 불순물에 상당히 민감하게 반응한다. 성분 <TEX>$I_2$</TEX>을 증가시켰을 때, 농도 대류효과는 확산-대류 유동흐름을 안정화시키는 경향이 있다. 지상중력가속도의 0.001환경에서는 유동흐름은 1차원포물선의 흐름 구조를 나타내며, 확산지배형태를 보여주고 있다. <TEX>$10^{-3}$</TEX>지상중력가속도 이하에서는 대류 영향은 무시할 수 있다. In this study, impurity effects on diffusive-convection flow fields by physical vapor transport under terrestrial and microgravity conditions were numerically analyzed for the mixture of <TEX>$Hg_2Cl_2-I_2$</TEX> system. The numerical analysis provides the essence of diffusive-convection flow as well as heat and mass transfer in the vapor phase during the physical vapor transport through velocity vector flow fields, streamlines, temperature, and concentration profiles. The total molar fluxes at the crystal regions were found to be much more sensitive to both the gravitational acceleration and the partial pressure of component <TEX>$I_2$</TEX> as an impurity. Our results showed that the solutal effect tended to stabilize the diffusive-convection flow with increasing the partial pressure of component <TEX>$I_2$</TEX>. Under microgravity conditions below <TEX>$10^{-3}g_0$</TEX>, the flow fields showed a one-dimensional parabolic flow structure indicating a diffusion-dominant mode. In other words, at the gravitational levels less than <TEX>$10^{-3}g_0$</TEX>, the effects of convection would be negligible.

On the double diffusive convection flow of Eyring-Powell fluid due to cone through a porous medium with Soret and Dufour effects

This paper devotedly study the double diffusive Darcian convection flow of Eyring-Powell fluid from a cone embedded in a homogeneous porous medium with the effects of Soret and Dufour. Arising set of non-linear partial differential equations are transformed through a suitable self-similar transformation into a set of nonlinear ordinary differential equations. Further, the numerical and the analytical solutions of the governing equations are elucidated by using numerical method as well as non-perturbation scheme. Numerical values are presented through tables for the skin friction coefficients, Nusselt number and Sherwood number. The obtained results are validated by comparing the analytical results with previously published results obtained by bvp4c for the numerical values of physical quantities. The effect of various parameters on the velocity, temperature and concentration profiles is discussed and also shown graphically.

Radiation and Chemical Reaction Effects on Unsteady Double Diffusive Convective Flow past an Oscillating Surface with Constant Heat Flux

This paper presents an analysis of combined heat and mass transfer flow past an oscillating vertical plate under the action of radiation effects and chemical reaction when heat is supplied to the plate at constant rate. The governing equations are solved in closed form by Laplace-transform technique. The results are obtained for temperature, concentration, velocity, skin friction, Nusselt number, and Sherwood number. The effects of various parameters on flow variables are illustrated graphically, and the physical aspects of the problem are discussed.

Study of Macrosegregation Defects Formation Caused by Double Diffusive Convective Flow during Solidification of a Binary Alloy

Numerical study of both the solidification of the binary alloy Al-4.1%wtCu and macrosegregation defects formation have been carried out. The mixture continuum model was used in the development of the mathematical model representing the solidification phenomena. This model included the conservative equations (mass, momentum, energy and species); these equations were numerically solved by using a finite volume approach.

Nonsimilar solutions for double diffusive convection near a frustum of a wavy cone in porous media

A nonsimilar boundary layer analysis is presented for double diffusive convection flow near a vertical frustum of a sinusoidal wavy cone in a porous medium with constant wall temperature and concentration. A coordinate transformation is employed to transform the complex wavy conical surface to a smooth conical surface, and the transformed nonsimilar boundary layer governing equations are then solved by the cubic spline collocation method. Effects of the Lewis number, buoyancy ratio, half cone angle and wavy geometry on the Nusselt and Sherwood numbers for a frustum of a sinusoidal wavy cone in porous media are studied. The harmonic curves for the local Nusselt number and those for local Sherwood number as functions of streamwise coordinate have a frequency twice the frequency of the wavy conical surface. Moreover, an increase in the amplitude–wavelength ratio raises the amplitude of the local Nusselt number and the local Sherwood number. Further, the average Sherwood number and the average Nusselt number for a frustum of a wavy cone are found to be smaller than those for the corresponding smooth frustum cone.

Effects of convective fluid motion upon oxide crystal growth in high temperature solution

For understanding of the influence of convective flow on crystal growth, space high temperature in situ observation instrument (SHITISOI) is dedicated to visualize and record the whole growth process of oxide crystals in high temperature up to 1,000°C. Model experiments using transparent liquids such as KNbO3 and a mixture of Li2B4O7+KNbO3 were chosen to investigate effects on ground and in space. On the earth, an investigation of growth kinetics of KNbO3 crystal related to two different states of convection: diffusive-advective flow and diffusive-convective flow, has been performed. The per unit length of a step e is calculated from the experimental data for two different states of convection. Analyses of these data show the effect of buoyancy convection is to enhance the sharpness of the interface. The growth of KNbO3 crystals from solution of KNbO3+Li2B4O7 was investigated in space. The streamlines of the steady thermocapillary convection in Li2B4O7 solvent was observed. Due to thermocapillary convection, KNbO3 crystal grains grew and filled the whole solution homogeneously. Earth-based quenching experiments are designed in order to study polyhedral instability of KNbO3 crystal, which is controlled by diffusion mechanism limitation. In all cases, when the crystal was nucleated near air/solution surface, it lost its polyhedral stability and varied from polyhedrons to dendrites. The thickness of diffusion mechanism limitation layer is about 60 µm.

Hysterisis effect on thermosolutal convection with opposed buoyancy forces in inclined enclosures

The onset of double diffusive convective flows in an inclined fluid layer, when constant fluxes of heat and mass are applied on the two oposing boundaries of the layer, is investigated. The case of equal and opposing buoyancy forces is considered. A numerical linear stability theory is used to determine the critical Rayleigh number for the onset of convection. The existence of a subcritical Rayleigh number, for the onset of finite amplitude convection, is demonstrated on the basis of the parallel flow approximation.

Effect of buoyancy-driven convection upon crystal growth of KNbO 3 in the melt

A high-temperature in situ observation method has been used to observe two different states of convection: diffusive–advective flow and diffusive–convective flow. Characteristic diffusion distance L can be easily measured from a Schlieren photograph and it ranges from 0.01 to 0.1 cm for two different states of convection. By observation of the rotating crystal growth processes in the KNbO 3 melt, the widths of interfacial concentration, heat and momentum transition zone are obtained, which are 7.5×10 −3, 8.6×10 −2 and 4.4×10 −1 cm, respectively. An investigation of growth kinetics of the KNbO 3 crystal related to the different states of convection in high-temperature melts has been performed by this melt. Irrespective of the state of convection in the melt, at the lower supercoolings two-dimensional nucleation growth has been obtained. At the same supercooling, the discrepancy between the growth rates for two different states of convection is assigned to the buoyancy convective enhancement of the interfacial mass flow. The free energy per unit length of a step ε, and the thermodynamic potential barrier for two-dimensional nucleation Δ G* are calculated from the experimental data for two different states of convection. These data are significant for consideration of the influence of convective flow on the interface growth kinetics. The effect of convection is to enhance the sharpness of the interface.