Defect and Diffusion Forum Vol. 392

Abstract: An unsteady magnetohydrodynamic natural convection transfer of mass and heat flow over a vertical porous sheet under the influence of thermal radiation and thermo-diffusion effect. The dimensionless governing equations are solved analytically by employing Laplace transform technique. The impact of various physical parameters on momentum, energy and concentration are discussed and analyzed with the aid of graphs. Furthermore, the numerical values for local Skin friction, Nusselt number and Sherwood number are noted and examined. Increasing the values of thermal diffusion results in increasing of the concentration, but it decreases with Schmidt number. Skin friction reduces for increasing values of thermo-diffusion are discussed with the help of tables.

Abstract: The objective of the current problem is to explore the impact of wall motion on flow, heat and species concentration of a UCM fluid in a magnetohydrodynamic Darcian channel. The flow is confined between two moving walls. The effects of the wall motion on the physical quantities for expanding and contracting cases are studied through non-dimensional numbers and variables. Numerical solutions for the highly nonlinear differential equations are obtained by reducing the governing PDE to ODE using well-established similarity variables. The variation of skin friction, Nusselt and Sherwood numbers has been investigated with the help of surface plots so that the influence of the squeezing number on the other non-dimensional parameters can be deeply understood. The results suggest that the squeezing channel intensifies the mass transfer and skin friction at the walls and it also increases the velocity, temperature and concentration of the fluid across the channel.

Abstract: Magnetohydrodynamics (MHD) flow of Casson fluid over a curved stretching surface with the effects of heat and mass flux conditions are studied. Casson fluid is one of the non-Newtonian fluid. Human blood is taken as example of Casson fluid. The flow, heat transfer and the mass transfer characteristics are found by a curved stretching sheet with flux conditions. The governing partial differential equations are converted into nonlinear ordinary differential using similarity transformations and are solved using the Runge-Kutta Fourth order method along with shooting technique. The effects of pertinent governing parameters on the fluid velocity, the temperature and the concentration are shown with help of the graphs. The Skin frication coefficient and the Nusselt number are calculated numerically. The present results have been good agreement when compared with existing results under some special cases.

Abstract: The boundary layer flow, heat and mass transfer over a permeable stretching sheet due to a chemically reacting micropolar fluid with slip and convective boundary conditions have been analyzed. Transverse magnetic field clubbed with electric field is also considered for the sake of brevity. Governing nonlinear coupled PDEs are transformed to nonlinear ODEs with the use of suitable similarity transformation. However, analytical solutions to these transformed equations are not useful therefore; numerical solution is carried out using Runge-Kutta fourth order with shooting technique. The characteristics of the embedded parameters are obtained and presented through graphs. Validation of the proposed work with earlier established results are shown in tables and these are in good agreement. From the careful observation the major outcomes are: induced magnetic field decelerates the flow, enhances the thickness of thermal boundary layer temperature whereas applied electric field decelerates the thickness of thermal boundary layer. Both electric field and slip parameter accelerates the angular momentum. Temperature and concentration magnitudes are accelerated at the sheet with an increase of slip parameter. Furthermore, Schmidt number and first order chemical reaction reduces the concentration boundary layer thickness. PACS Number: 05.45-a; 05.70-Ce.

Abstract: A numerical analysis was performed to study the effects of combined double diffusive and viscous dissipation under non-uniform wall boundary conditions on heat and mass transfer for a viscous nanofluid past a semi-infinite vertical plate embedded in porous medium which descriped by Darcy-Forchheimer extension. The mathematical model of nanofluid incorporate the Brownian motion and thermophoresis mechanisms. The nonlinear governing equations are reduced to a set of nonsimilar ordinary differential equations and the resulting system of equations is then solved numerically by Keller-Box method. A parametric study is achieved and obtained numerical results are presented with the help of graphical illustrations, in order to ride how the governing parameters affects the flow field, temperature, concentration and solide volume fraction profiles. Furthermore, some interesting data for the local Nusselt and Sherwood numbers are also illustrated.

Abstract: This study extends previous investigation on ohmic heating of magnetohydrodynamic viscous fluid flow over a continuous moving plate to include radiative heat-loss, viscous dissipation and buoyancy effects. The mathematical formulation representing the modified physical model involves a system of three partial differential equations, which are transformed into a system of two coupled non-linear ordinary differential equations using suitable dimensionless variables. Thereafter, the resulting dimensionless system of equations governing modified model are solved via Homotopy Analysis Method (HAM). The accuracy and convergence of solutions are vali￾dated by comparing the results obtained with those in literature and they are in good agreement. Parametric study is performed to illustrate the effects of emerging parameters on fluid velocity and temperature, skin friction coefficient and Nusselt number. It is found that the impacts of pertinent parameters due to the extensions are significant and these are presented in graphs and tables. The results indicate that the skin friction coefficient and the heat transfer rate increase with the increasing values of thermal radiation and decrease with the increasing value of viscous dissipation parameter.

Abstract: The prominence of present work is to investigate the axisymmetric mixed convective magnetohydrodynamic (MHD) flow of a Casson nanofluid over a stretching variable thickened rotating disk in the presence of heat source/sink and velocity slip surface boundary condition. Besides, thermal buoyancy and viscous dissipation effects are examined. Convective heat and zero nanoparticles mass flux conditions at the boundaries of the disk are implemented. Von Karman similarity transformation is employed to formulate highly nonlinear coupled ordinary differential equations and solved via Optimal Homotopy Analysis Method (OHAM). The computed numerical values are presented graphically to predict the features of the embedded parameters. A new method (slope of the linear regression) is used to analyze the computed data of Skin friction coefficient, Nusselt number and Sherwood number. It is found that the power law exponent parameter plays a dominant role within the velocity, thermal and concentration boundary layer regions. Further, the fluid flow is opposed due to the magnetic field and velocity slip results in a reduced velocity boundary layer.

Abstract: The two dimensional study of natural convection in vertical cylindrical annular enclosure filled with Cu-water nanofluid under magnetic fields is numerically analyzed. The vertical walls are maintained at different uniform hot and cold temperatures, T_H and T_C, respectively. The top and bottom walls of the enclosure are thermally insulated. The governing equations are solved numerically by using a finite volume method. The coupling between the continuity and momentum equations is effected using the SIMPLER algorithm. Numerical analysis has been carried out for a wide range of Rayleigh number (10³ ≤Ra≤10⁶), Hartmann number (1 ≤Ha≤100) and nanoparticles volume fraction (0 ≤φ≤0.08). The influence of theses physical parameters on the streamlines, isotherms and average Nusselt has been numerically investigated.

Abstract: The effects of slip and wall properties on the peristaltic mechanism of Rabinowitsch fluid flowing through a non-uniform inclined tube is investigated under the assumptions of long wavelength and small Reynold’s number. The governing equations of motion, momentum, and energy are rendered dimensionless by using suitable similarity transformations. The effects of the velocity slip parameter , thermal slip parameter, wall rigidity parameter, wall stiffness parameter and the viscous damping force parameter on velocity, temperature and streamlines are analyzed for shear thinning, viscous, and shear thickening fluid models. From the results, it is found that an increase in the value of velocity and thermal slip parameter enhances the velocity and temperature profiles for viscous and shear thinning fluids. Also, the volume of trapped bolus improves for an increase in the value of rigidity and stiffness parameter for all the three liquids, whereas it decreases for an increase in the value of the viscous damping force parameter.