Double-diffusive Boundary Layer Research Articles

Viscoelastic fluid flow over a horizontal flat plate with various boundary slip conditions and suction effects

This study examines the numerical representation of fluid flow on the Maxwell model in a double-diffusive boundary layer over a horizontal plate.

Influences of Zero Mass Flux and Active Conditions on the Predictions of Double Dispersion and Double Diffusive Boundary Layer in Darcy/Non Darcy Nanofluid Flow

Free convective of nanofluid inside dispersive porous medium adjacent to a vertical plate under the effects of the zero mass nanoparticles flux condition and the thermal and solutal dispersions is studied. Buongiorno's model revised is used considering Darcy and non Darcy laminar flows, and isothermal or convective flux outer the wall. Dimensionless governing equations formulated using velocity, temperature, concentration and nanoparticle volume fraction have been solved by finite difference method that implements the 3-stage Lobatto collocation formula. The numerical data obtained with semi or full dispersions cases are compared to predictions made using the non dispersive porous medium. Taking into account the dispersions, the influence of the zero mass nanoparticles flux condition is examined to test the validity of the control active nanoparticle assumption. It is found mainly that the thermal transfers can reach more than 100% in connection with the case where of a semi-dispersion of the porous medium is applied. Realistic condition, i.e. zero mass flux should be addressed for the heat transfer rate rather than the mass transfer rate, discovered markedly different to the active condition. This signifies the importance of considering the zero nanoparticles mass flux and dispersions in the performance characterization of nanofluid flow in porous media.

Thermodiffusion effects on boundary layer flow of viscoelastic nanofluids over a stretching sheet with viscous dissipation and non-uniform heat source using hp-finite element method

This paper theoretically investigates the conjugate effects of viscous dissipation and non-uniform heat source/ sink on the double-diffusive boundary layer flow of a viscoelastic nanofluid over a stretching sheet. In this model, where binary nanofluid is used, the Brownian motion, thermophoresis and cross-diffusion are classified as the main mechanisms which are responsible for the enhancement of the convection features of the nanofluid. The boundary layer equations governed by the partial differential equations are transformed into a set of ordinary differential equations with the help of group theory transformations. Computations are made by the hp-Galerkin finite element method (FEM). The hp-FEM needs a smaller number of nodes and consequently, less computational time and less memory to achieve the same or even better accuracy than h-FEM. A detailed evaluation of the effects of the governing physical parameters on the velocity, temperature, solutal and nanoparticle concentration via graphical plots is conducted for two different cases, namely prescribed surface temperature (PST) and prescribed heat flux (PHF). The reduced Sherwood number (in PST-case) is observed to be increased with the effects of nanofluid and the modified Dufour parameter, whereas the contrary behaviour is computed for the surface solutal concentration in PHF-case. Heat transfer is increasing function of viscoelastic parameter and decreasing function of Brownian motion, thermophoresis, space and time dependent heat source/sink parameter and Eckert number. Mass transfer is increasing function of Eckert number, space and time dependent heat source/sink parameter and decreasing function of viscoelastic parameter.

Finite element solution of double-diffusive boundary layer flow of viscoelastic nanofluids over a stretching sheet

This paper deals with the double-diffusive boundary layer flow of non-Newtonian nanofluid over a stretching sheet. In this model, where binary nanofluid is used, the Brownian motion and thermophoresis are classified as the main mechanisms which are responsible for the enhancement of the convection features of the nanofluid. The boundary layer equations governed by the partial differential equations are transformed into a set of ordinary differential equations with the help of group theory transformations. The variational finite element method (FEM) is used to solve these ordinary differential equations. We have examined the effects of different controlling parameters, namely, the Brownian motion parameter, the thermophoresis parameter, modified Dufour number, viscoelastic parameter, Prandtl number, regular Lewis number, Dufour Lewis number, and nanofluid Lewis number on the flow field and heat transfer characteristics. Graphical display of the numerical examine are performed to illustrate the influence of various flow parameters on the velocity, temperature, concentration, reduced Nusselt, reduced Sherwood and reduced nanofluid Sherwood number distributions. The present study has many applications in coating and suspensions, movement of biological fluids, cooling of metallic plate, melt-spinning, heat exchangers technology, and oceanography.

Finite element solution of double-diffusive boundary layer flow of viscoelastic nanofluids over a stretching sheet

Finite element solution of double-diffusive boundary layer flow of viscoelastic nanofluids over a stretching sheet

Soret Effect on Double-Diffusive Boundary Layer Flows in a Vertical Porous Cavity

Soret Effect on Double-Diffusive Boundary Layer Flows in a Vertical Porous Cavity

Influence of Fluctuating Surface Temperature and Concentration on Natural Convection Flow from a Vertical Flat Plate

A linearized theory is used to investigate how a free double-diffusive boundary layer flow is affected by small amplitude temporal variations in the surface temperature and species concentration. The mean temperature and the mean species concentration are assumed to vary as a power n of the distance measured from the leading edge. Three distinct methods, namely, a perturbation method for low frequencies, an asymptotic series expansion for high frequencies, and a finite difference method for intermediate frequencies, are used. Calculations have been carried out for a wide range of parameters in order to examine the results obtained from the three methods. Comparisons are made in. terms of the amplitudes and phases of the surface. heat transfer and surface mass transfer. It has been found that the amplitudes and phase angles predicted by perturbation theory and the asymptotic method are in good agreement with the finite difference computations.

Countercurrent convection in a double-diffusive boundary layer

Countercurrent flow may be induced by opposing buoyancy forces associated with compositional gradients and thermal gradients within a fluid. The occurrence and structure of such flows is investigated by solving the double-diffusive boundary-layer equations for steady laminar convection along a vertical wall of finite height. Non-similar solutions are derived using the method of matched asymptotic expansions, under the restriction that the Lewis and Prandtl numbers are both large. Two sets of asymptotic solutions are constructed, assuming dominance of one or the other of the buoyancy forces. The two sets overlap in the central region of the parameter space; each set matches up with neighbouring unidirectional similarity solutions at the respective borderlines of incipient counterflow.Interaction between the buoyancy mechanisms is controlled by their relative strength R and their relative diffusivity Le. Flow in the outer thermal boundary layer deviates from single-diffusive thermal convection, depending upon the magnitude of the parameter RLe. Flow in the inner compositional boundary layer deviates from single-diffusive compositional convection, depending upon the magnitude of $RLe^{\frac{1}{3}}$.