Defect and Diffusion Forum Vol. 388

Abstract: This article describes the effects of Joule heating and chemical reaction on unsteady MHD mixed convective micropolar fluid over a stretching sheet in presence of radiation, non-uniform heat source and porous medium. The arising non-linear coupled partial differential equations are reduced to a set of coupled non-linear ordinary differential equations and then solved numerically by using the Runge– Kutta–Fehlberg fourth–fifth order method along shooting technique. The graphical and tabular results elucidate the influence of different non-dimensional governing parameters on the velocity, temperature and concentration fields along with the wall friction, local Nusselt and Sherwood numbers. We found the dual nature of the solutions for suction and injection cases. A good agreement of the present results has been observed by comparing with the existing literature results.

Abstract: Mathematical model has been analyzed on MHD convective two-phase flow in a divergent channel with viscous dissipation. The effects of velocity and temperature slip are considered. The relevant governing equations are non-dimensionalised with the help of appropriate transformations and then solved numerically. The present results overlooked with existing results and found in an excellent agreement. Effects of emerging parameters on the flow are discussed and demonstrated graphically. Graphical aid is also used to present the variations in skin friction and Nusselt number. It is found that an increase in velocity slip, the velocities of fluid as well as particle phases are increased. An increase in temperature slip, the temperature of fluid phase gets decreased. KEY WORDS:Particulate suspension, two-phase flow, diverging channel,Slip effects

Abstract: This article deals with the analytical study of MHD flow and heat transfer over a permeable stretching sheet via homotopy analysis method (HAM). The effect of thermal radiation is included in the energy equation, while velocity and thermal slips are included in the boundary conditions. The governing boundary layer equations are transformed into a set of ordinary differential equations by means of similarity transformations. The effects of different parameters on the flow field and heat transfer characteristics are examined. The results obtained were shown to compare well with the numerical results and for some special cases with the published data available in the literature, which are in favorable agreement. Keywords: MHD; Slip flow; Stretching sheet; Thermal radiation; Homotopy analysis method

Abstract: A numerical computation has been carriedout for the steady, mixed convective, incompressible, viscous, electrically conducting couple stress fluid through a vertical plate with variable fluid properties in a porous medium. A uniform magnetic field is applied in the transverse direction and parallel to the vertical plate of the physical model and governing equations are derived for it."Using a suitable similarity transformation, governed PDE's are transformed into a set of ODE's which are highly non-linear coupled equations. An advanced Shooting technique is adopted to compute the variations of velocity, temperature, concentration in terms of non-dimensional parameters. Also physical interpretation of non-dimensional parameters like couple stress parameter magnetic field Prandtl number Schmidt number thermal conductivity and solutal diffusivity parameters are examined through plots for both variable permeability and uniform permeability."From the numerical results, an excellent agreement has been observed for the present results, as well as comparison is made between the present and the earlier works for a particular case of the problem.

Abstract: The numerical study of axi-symmetric, steady flow of an incompressible micropolar fluid past an impervious sphere is presented by assuming uniform flow far away from the sphere. The continuity, linear and angular momentum equations are considered for incompressible micropolar fluid in accordance with Eringen. The governing equations of the physical problem are transformed to ordinary differential equation with variable co-efficient by using similarity transformation method. The obtained differential equation is then solved numerically by assuming the shooting technique. The effect of coupling and coupling stress parameter on the properties of the fluid flow is studied and demonstrated by graphs.

Abstract: An irreversible model of proton exchange membrane fuel cells working at steady-state is established, in which the irreversibility resulting from overpotentials, internal currents and leakage currents are taken into account. In this paper, the irreversibility of fuel cell is expounded mainly from electrochemistry. The general performance characteristic curves are generated including output voltage, output power and output efficiency. In addition, the irreversibility of a class of PEMFC is studied by changing the operating conditions (controllable factors) of the fuel cell, including effect of operating temperature, operating pressure and leakage current. The results provide a theoretical basis for both the operation and optimal design of real PEM fuel cells.

Abstract: This paper deals with synovial joints which are characterized by their large degree of motion. In synovial joints, magnetic field in addition to electric field is added to disperse the nutrients from the synovial fluid to cartilage by considering both BJ and BJR conditions. The governing equation of the physical model is solved analytically and computations are carried out for the parameters involved in the system under different boundary conditions. The obtained computational results indicate that a drastic improvement can be found for the efficiency of artificial joints with combined effects of electric and magnetic fields on electrohydrodynamic dispersion of biological bearings.

Abstract: In this work, we presented a numerical contribution to numerically evaluate the thermal transfer improvement from forcing a 2D flow of air through a baffled channel. Two complex geometry fins were inserted in the flow field to force recirculation zones to augment mixing and thus, the thermal transfer. The dynamic thermo-energy behavior of air is shown for Re numbers ranging from 12 × 10³ to 32 × 10³. The governing equations, employed to simulate the turbulent forced-convection airflow in the domain under investigation, were solved using the finite volume method, by means of CFD FLUENT, based on the SIMPLEC algorithm. For using the complex geometry fins, the augmentations in Nusselt number and friction factor are in the range of 194.108 - 387.322 % and 476.779 - 2603.667 % over the smooth channel with no fin, respectively. In addition, the use of complex geometry fins with Re = 32 × 10³ gives higher TEF than that with Re = 17,000, 22,000, and 27,000 around 12.072 %, 8.568 %, 5.189 %, and 2.389 %, respectively.

Abstract: Fully developed Mixed Convection through vertical channel in the presence of heat generation/absorption with first order chemical reaction is analyzed.The thermal boundary conditions are isothermal–isothermal for left and right walls of the channel and kept at different temperatures.The effect of thermal buoyancy parameter, concentration buoyancy parameter and heat generation/absorption parameter are studied. Also the flow field with the presence of first order chemical reaction is particularly analyzed. The governing equations are solved using finite element method.Velocity, temperature and concentration profiles are investigated for different values of the flow parameters.

Abstract: This study numerically investigates the mixed convection of ferrofluids in a partially heated lid driven square enclosure. The heater is located to the left vertical wall and the right vertical wall is kept at constant lower temperature while other walls of the cavity are assumed to be adiabatic. The governing equations are solved with Galerkin weighted residual finite element method. The influence of the Richardson number (between 0.01 and 100), heater location (between 0.25 H and 0.75H), strength of the magnetic dipole (between 0 and 4), and horizontal location of the magnetic dipole source (between-2H and-0.5H) on the fluid flow and heat transfer are numerically investigated. It is found that local and averaged heat transfer deteriorates with increasing values of Richardson number and magnetic dipole strength. The flow field and thermal characteristics are sensitive to the magnetic dipole source strength and its position and heater location.