Magnetohydrodynamic go-water nanofluid flow and heat transfer between two parallel moving disks

The unsteady MHD squeezing flow of nanofluid with different type of nanoparticles between two parallel disks is discussed. The governing equations, continuity, momentum, energy, and concentration for this problem are reduced to coupled non-linear equations by using a similarity transformation. It has been found that for contracting motion of upper disk combined with suction at lower disk, effects of increasing absolute values of squeeze parameter are quite opposite to the case of expanding motion. In this case, radial velocity near upper disk decreases while near the lower disk an accelerated radial flow is observed. The comparison between analytical results and numerical ones achieved by forth order Runge-Kutta method, assures us about the validity and accuracy of problem

Analytical simulation of mixed convection between two parallel plates in presence of time dependent magnetic field

327-332<span style="font-size:11.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-bidi-font-family:="" mangal;mso-ansi-language:en-gb;mso-fareast-language:en-us;mso-bidi-language:="" hi"="" lang="EN-GB">Heat transfer enhancement in various energy systems is vital because of the increase in energy prices. In recent years, nanofluids technology is proposed and studied by some researchers experimentally or numerically to control heat transfer in a process. In this paper, an unsteady incompressible three-dimensional mixed convection rotating flow of viscous fluid between two infinite vertical plane walls is investigated analytically using Galerkin optimal homotopy asymptotic method (GOHAM). We also consider the viscous dissipation effects. Such a consideration is significant, because the viscous dissipation effects (the generation of heat due to friction caused by shear in the flow) are important when the fluid is largely viscous or flowing at a high speed. The effects of the emerging parameters on the flow and heat transfer characteristics are studied and examined.</span

Flow and heat transfer of MHD graphene oxide-water nanofluid between two non-parallel walls

The steady 2-D heat transfer and flow between two non-parallel walls of a graphene oxide nanofluid in presence of uniform magnetic field are investigated in this paper. The analytical solution of the non-linear problem is obtained by Galerkin optimal homotopy asymptotic method. At first a similarity transformation is used to reduce the partial differential equations modeling the flow and heat transfer to ordinary non-linear differential equation systems containing the semi angle between the plate’s parameter, Reynolds number, the magnetic field strength, nanoparticle volume fraction, Eckert and Prandtl numbers. Finally, the obtained analytical results have been compared with results achieved from previous works in some cases

Analytical solution of unsteady GO-water nanofluid flow and heat transfer between two parallel moving plates

Unsteady squeezing nanofluid flow between parallel plates has been analyzed analytically. The based fluid is water containing graphene oxide. The Reconstruction of Variational Iteration Method is used to solve this problem. Similarity transformations are used to transform the governing nonlinear equations of momentum and thermal energy to a system of nonlinear ordinary coupled differential equations with fitting boundary conditions. The transmuted model is shown to be controlled by a number of thermo-physical parameters, viz. moving parameter, graphene oxide nanoparticles solid volume fraction, Eckert and Prandtl number. Nusselt number and skin friction parameter are achieved for various values of GO solid volume fraction and Eckert number. The comparison assures us about validity and accuracy of solution

Analytical simulation of mixed convection between two parallel plates in presence of time dependent magnetic field

Heat transfer enhancement in various energy systems is vital because of the increase in energy prices. In recent years, nanofluids technology is proposed and studied by some researchers experimentally or numerically to control heat transfer in a process. In this paper, an unsteady incompressible three-dimensional mixed convection rotating flow of viscous fluid between two infinite vertical plane walls is investigated analytically using Galerkin optimal homotopy asymptotic method (GOHAM). We also consider the viscous dissipation effects. Such a consideration is significant, because the viscous dissipation effects (the generation of heat due to friction caused by shear in the flow) are important when the fluid is largely viscous or flowing at a high speed. The effects of the emerging parameters on the flow and heat transfer characteristics are studied and examine

Analytical solution of unsteady GO-water nanofluid flow and heat transfer between two parallel moving plates

47-52Unsteady squeezing nanofluid flow between parallel plates has been analyzed analytically. The based fluid is water containing graphene oxide. The Reconstruction of Variational Iteration Method is used to solve this problem. Similarity transformations are used to transform the governing nonlinear equations of momentum and thermal energy to a system of nonlinear ordinary coupled differential equations with fitting boundary conditions. The transmuted model is shown to be controlled by a number of thermo-physical parameters, viz. moving parameter, graphene oxide nanoparticles solid volume fraction, Eckert and Prandtl number. Nusselt number and skin friction parameter are achieved for various values of GO solid volume fraction and Eckert number. The comparison assures us about validity and accuracy of solution

Theoretical analysis of the conical premixed flame response to upstream velocity disturbances considering flame speed development effects

The effect of upstream velocity perturbations on the response of a premixed flame was investigated in terms of the flame transfer function dependency on excitation frequency. In this study, the assumption of constant flame speed was extended and the effect of flame speed development was considered; i.e., the flame speed would grow with the time after ignition or with the distance from a flame-holder. In the present study, the kinematics of a conical flame was investigated by linearization of the front tracking equation of flame to uniform and convected fluctuations of the flow velocity and the response was compared with that of a V-shaped flame and the experimental data in the previous studies. The results show that the effect of flame speed development could influence a decreasing gain and increase the phase of the flame response to the uniform velocity oscillations in low and moderate frequencies. Comparing the variations in the gain of flame response upon normalized frequency, show that a conical flame has lower values than the V-flame. In other words, these flames might be less susceptible to combustion instabilities than the V-flames. Furthermore, the variations in phase of the V-flames responses, which show a quasi-linear behavior with normalized frequency, have higher values than the saturated behavior in phase of the conical flame responses. Also, considering that the flame speed development induces an increase in the gain and phase of the conical flame response to the convected velocity oscillations in certain frequencies; because the developed flame front has longer length in comparison to the flame front in constant flame speed model. Therefore, the flame length may be longer than convective wavelength and the heat release would be generated in different points of the flame; consequently the flow oscillations might exert a stronger impact on the unsteady heat release fluctuations

Development of an Implicit Physical Influence Upwind Scheme for Cell-Centered Finite Volume Method

An essential component of a finite volume method (FVM) is the advection scheme that estimates values on the cell faces based on the calculated values on the nodes or cell centers. The most widely used advection schemes are upwind schemes. These schemes have been developed in FVM on different kinds of structured and unstructured grids. In this research, the physical influence scheme (PIS) is developed for a cell-centered FVM that uses an implicit coupled solver. Results are compared with the exponential differencing scheme (EDS) and the skew upwind differencing scheme (SUDS). Accuracy of these schemes is evaluated for a lid-driven cavity flow at Re = 1000, 3200, and 5000 and a backward-facing step flow at Re = 800. Simulations show considerable differences between the results of EDS scheme with benchmarks, especially for the lid-driven cavity flow at high Reynolds numbers. These differences occur due to false diffusion. Comparing SUDS and PIS schemes shows relatively close results for the backward-facing step flow and different results in lid-driven cavity flow. The poor results of SUDS in the lid-driven cavity flow can be related to its lack of sensitivity to the pressure difference between cell face and upwind points, which is critical for the prediction of such vortex dominant flows

A Two-Phase Flow Interface Tracking Algorithm Using a Fully Coupled Pressure-Based Finite Volume Method

Two-phase and multi-phase flows are common flow types in fluid mechanics engineering. Among the basic and applied problems of these flow types, two-phase parallel flow is the one that two immiscible fluids flow in the vicinity of each other. In this type of flow, fluid properties (e.g. density, viscosity, and temperature) are different at the two sides of the interface of the two fluids. The most challenging part of the numerical simulation of two-phase flow is to determine the location of interface accurately. In the present work, a coupled interface tracking algorithm is developed based on Arbitrary Lagrangian-Eulerian (ALE) approach using a cell-centered, pressure-based, coupled solver. To validate this algorithm, an analytical solution for fully developed two-phase flow in presence of gravity is derived, and then, the results of the numerical simulation of this flow are compared with analytical solution at various flow conditions. The results of the simulations show good accuracy of the algorithm despite using a nearly coarse and uniform grid. Temporal variations of interface profile toward the steady-state solution show that a greater difference between fluids properties (especially dynamic viscosity) will result in larger traveling waves. Gravity effect studies also show that favorable gravity will result in a reduction of heavier fluid thickness and adverse gravity leads to increasing it with respect to the zero gravity condition. However, the magnitude of variation in favorable gravity is much more than adverse gravity