Abstract: In this analysis, effects of viscous dissipation and thermal radiation on an electrically conducting boundary layer flow, heat and mass transfer of a fluid through a porous medium over a stretching sheet in the presence of heat source/sink is considered. The symmetry groups admitted by the corresponding boundary value problem are obtained by using symmetric transformations. These transformations are used to convert the partial differential equations of the governing equations into self-similar non-linear ordinary differential equations. These transformed ODEs are solved by employing Runge-Kutta fourth order with shooting method. Numerical results obtained for different thermo-physical parameters characterizes the flow phenomena are drawn graphically and effects of various physical parameters on velocity, temperature and concentration profiles are discussed. Numerical computation for skin friction, Nusselt number and Sherwood number are also obtained and presented in Tables.
Abstract: In this article, the motion of a non-Newtonian visco-inelastic fluid over an object that is neither a cone/wedge nor horizontal/vertical is presented. It is assumed that partial slip and buoyancy induces the flow of Williamson fluid over this kind of object herein referred to as an upper horizontal surface of a paraboloid of revolution. Considering the relationship between the thicknesses of the object and velocity index; the relevance of partial slip at the leading edge is significant and illustrated in this article. The governing equation which models the flow is non-dimensionalized and parameterized. The corresponding dimensionless equations are solved numerically using shooting technique along with fourth order Runge-Kutta integration scheme. Due to the presence of partial slip and thermal jump, increase in horizontal velocity at the wall is ascertained. The decrease in local heat transfer rate is ascertained within large interval next to the surface of a paraboloid of revolution in the absence of partial slip and thermal jump. A significant decrease in temperature distribution near the surface of an upper horizontal surface of a paraboloid of revolution is guaranteed with an increase in thermal buoyancy parameter in the presence of thermal jump.
Abstract: In this paper, we investigate the combined effects of Brownian motion, thermophoresis and Cattaneo-Christov heat flux on Casson nanofluid boundary layer flow over a stretching cylinder. The governing partial differential equations (PDEs) are obtained and transformed into a system of ordinary differential equations (ODEs) by employing appropriate similarity solution. The model nonlinear boundary value problem is tackled numerically using fourth-fifth order Runge-Kutta integration scheme with shooting technique. Effects of various thermophysical parameters on the velocity, temperature and concentration profiles as well as skin friction and Sherwood number are presented graphically and discussed quantitatively. It is found that thermal relaxation parameter minimizes the temperature field and boosting the rate of heat transfer per unit volume. This heat flux conditions are very useful for thermal transport control in manufacturing and chemical industries.
Abstract: In this study, the flow of CuO-water nanofluid in a parallel-plate microchannel in the presence of several micromixers is examined to find optimum arrangements of the micromixers. The governing equations, which are accompanied with the slip velocity and temperature jump boundary conditions, are solved by the Finite Volume Method and SIMPLER algorithm. The study is conducted for the Reynolds numbers in the range of 10 ≤ Re ≤ 100, Knudsen numbers ranging of 0 ≤ Kn ≤ 0.1 and volume fraction of nanoparticles ranging of 0 ≤ ϕ ≤ 4%. The results show that the optimum arrangements of the micromixers belong to cases in which the heights of micromixers are smaller, the distance between them is lower, and their numbers are more.
Abstract: A numerical investigation is carried out to understand the effects of thermal buoyancy and Reynolds number on flow characteristics and mixed convection heat transfer over three isothermal circular cylinders situated in a tandem arrangement within a horizontal channel. The distance between cylinders is fixed at the value of 2.5 widths of the cylinder. The obtained results are presented and discussed for the range of conditions as: Re = 5 to 40, Ri = 0 to 2 at fixed Pr number of 1 and blockage ratio β = 0.25. The main results are depicted in terms of streamlines and isotherm contours to analyze the effect of thermal buoyancy on fluid flow and heat transfer rate. Moreover, the overall drag coefficient and Nusselt number are computed to elucidate the role of Reynolds number and Richardson number on the flow and heat transfer. It is found that increase in the Richardson number increases the drag coefficient of the upstream cylinder whereas it decreases the heat transfer rate of this cylinder. The superimposed of thermal buoyancy created a new sort of recirculation zones between the tandem cylinders.
Abstract: The hemodynamics mixed convection in a stenosed artery with radiative heat transfer in the presence of magnetic field is investigated. Blood is regarded as a viscous, incompressible, Newtonian, electrically conducting and optically dense bio-magnetic fluid. The variable viscosity of blood depending on hematocrit (percentage volume of erythrocytes) is taken into account in order to improve resemblance to the real situation. The constriction in the artery due to stenosis is assumed to be symmetrical such that the stenotic height is small compared with the half width of the unconstricted channel. The governing equations of momentum and energy balance are obtained and solved both numerically using a shooting technique coupled with Runge-Kutta-Fehlberg integration method and analytically using a well known perturbation technique. The effects of various controlling parameters on the dimensionless velocity, temperature, pressure gradient, skin friction and Nusselt number are presented graphically and discussed. It is observed that the flow rate at the stenotic region is enhanced by buoyancy force. The fluid velocity decreases while the temperature increases with an in magnetic field intensity. Our results could be useful in improving the design of flow meters in bio-medical instrumentation for detecting cardiovascular pathological conditions such as stenosis.
Abstract: A numerical investigation is performed into the heat transfer and entropy generation of a variable thermal conductivity magnetohydrodynamic flow of Al2O3-water nanofluid in a vertical channel of varying width with right porous wall, which enable the fluid to enter. The effects of the Lorentz force, buoyancy force, viscous dissipation and Joule heating are considered and modeled using the transverse momentum and energy balance equations respectively. The governing nonlinear partial differential equations are transformed into a system of coupled nonlinear ordinary differential equations using appropriate similarity transformations and then solved numerically using power series with Hermite-Padé approximation method. A stability analysis has been performed for the local rate of shear stress and Nusselt number that indicates the existence of dual solution branches. Numerical results are achieved for the fluid velocity, temperature as well as the rate of heat transfer at the wall and the entropy generation of the system. The present results are original and new for the flow and heat transfer past a channel of varying width in a nanofluid which shows that the physical parameters have significant effects on the flow field.
Abstract: This paper presents the entropy generation analysis of buoyancy effect with internal heat generation on a viscous incompressible non-Newtonian hydromagnetic Poiseuille flow through vertical isothermal walls. The solution of the non-linear boundary value problems obtained from the governing equations is constructed via the rapidly convergent semi-analytical technique of Adomian decomposition. Graphs and table are presented to analyse the effects of some parameters on fluid motion, temperature, entropy generation and irreversibility ratio.
Abstract: A two-dimensional numerical simulation is carried out to understand the combined effects of thermal buoyancy strength and rheological flow behavior of non Newtonian power-law fluids on laminar flow and heat transfer rate through a 180° curved duct. The governing equations including the full Navier-Stokes, the continuity and the energy are solved using the commercial code ANSYS-CFX. The numerical results are presented and discussed for the range of conditions as: Re = 40 to 1000, Ri = 0 to 1 and n = 0.4 to 1.2 for fixed value of Prandt number of Pr = 1. In order to analyze the obtained results, the representative streamlines and isotherm patterns are presented. The average Nusselt number of the inner and outer walls of duct is computed to determine the role of Reynolds number, Richardson number and power-law index on flow and heat transfer. It is found that increase in Richardson number creates alternative vortices on duct walls. Moreover, the alternative vortices enhance the heat transfer rate for shear thinning, Newtonian and shear thickening fluids.