Journal Of Applied Fluid Mechanics
Volume:5 Issue: 3, Mar-Apr 2012

The study of hydromagnetic heat and mass transfer in MHD flow of an incompressible, electrically conducting, viscous fluid past an infinite vertical porous plate along with porous medium of time dependent permeability under oscillatory suction velocity normal to the plate has been made. It is considered that the influence of the uniform magnetic field acts normal to the flow and the permeability of the porous medium fluctuate with the time. The problem is solved, numerically by Galerkin finite element method for velocity, temperature, concentration field and the expressions for skin – friction, Nusselt number and Sherwood number are also obtained. The results obtained are discussed for Grashof number (Gr > 0) corresponding to the cooling of the plate and (Gr < 0) corresponding to the heating of the plate with the help of graphs and tables to observe the effects of various parameters.

The problem of steady, laminar flow and heat transfer of an electrically conducting fluid through vertical channel in the presence of uniform transverse magnetic field is formulated using a two-fluid continuum model. Combined free and forced convection inside the channel is considered. The effects of viscous and ohmic dissipations are included in the energy equation. Both walls are kept either at the same or different temperatures such as isoflux-isothermal and isothermal-isoflux conditions. Governing equations in cartesian co-ordinates are solved analytically using regular perturbation technique to develop the expression for velocity and temperature. Velocity, temperature and Nusselt number are presented graphically. Effects of pertinent parameters, such as Hartmann number, electric field load parameter, viscosity ratio, width ratio and conductivity ratio are determined.

Aim of the paper is to investigate the MHD effects on the unsteady boundary layer flow of an incompressible micropolar fluid over a stretching sheet when the sheet is stretched in its own plane. The stretching velocity is assumed to vary linearly with the distance along the sheet. Two equal and opposite forces are impulsively applied along x  axis so that the sheet is stretched, keeping the origin fixed in a micropolar fluid. The governing non-linear equations and their associated boundary conditions are first cast into dimensionless form by a local non-similarity transformation. The resulting equations are solved numerically using the Adams- Predictor Corrector method for the whole transient from the initial state to final steady- state flow. Numerical results are obtained and a representative set is diaplaced graphically to illustrate the influence of the various physical parameters on the velocity profiles, microrotation profiles as well as the Skin friction coefficient for various values of the material parameter K. It is found that there is a smooth transition from the small- time solution to the large- time solution. Results for the local skin friction coefficient are presented in table as well as in graph.

An attempt is made for the study of steady two-dimensional flow of a viscous and incompressible fluid striking at some angle of incidence on a stretching sheet. Fluid is considered in the porous media obeying Darcy law, in the presence of radiation effect. Rosseland approximation is use to model the radiative heat transfer. The stream function splits into a Hiemenz and a tangential component. Using similarity variables, the governing partial differential equations are transformed into a set of three non-dimensional ordinary differential equations. These equations are then solved numerically using fifth order Runge-Kutta Fehlberg method with shooting technique. In the present reported work the effects of striking angle, radiation parameter, porosity parameter and the Prandtl number on flow and heat transfer characteristics have been discussed. Variations of above discussed parameters with the stretching sheet parameter have been graphically presented.

An incompressible unsteady viscous two-dimensional Navier-Stokes solver is developed by using “Consistent Flux Reconstruction” method. In this solver, the full Navier-Stokes equations have been solved numerically using a collocated finite volume scheme. In the present investigation, numerical simulations have been carried out for unconfined flow past a single circular cylinder with both structured and unstructured grids. In structured grid, quadrilateral cells are used whereas triangular elements are used in unstructured grid. Simulations are performed at Reynolds number (Re) = 100 and 200. Flow simulation over a NACA0002 airfoil at Re = 1000 using unstructured grid based solver is also reported. The vortex shedding phenomena is mainly investigated in the flow. It is observed that the nature of flow depends strongly on the value of the Reynolds number. The present results are found to be in satisfactory agreement with several numerical results and a few experimental results available from literature.

The present work is a numerical study of simultaneous heat and mass transfer with phase change in an inclined channel formed by two parallel plates. The lower one is covered by a thin liquid water film and the upper one is considered impermeable. The plates are maintained at a constant temperature. The liquid film is assumed to be extremely thin and its temperature is uniform and equal to that of the wall. Thermo-physical properties are considered constant and the Boussinesq assumption is adopted. Results show that the effects of the buoyancy forces on the ydrodynamic, thermal and mass fraction fields are important. These effects depend on the channel inclination and may result on flow reversal when the channel approaches the vertical position. This phenomenon is addressed and a flow reversal chart, as well as the corresponding correlations, for different channel inclinations is given. These correlations give the values of Grashof numbers, which induce flow reversal for a given Reynolds number and inclination angle.

In the present paper, an analysis is carried out the chemical reaction effects on an unsteady magneto hydrodynamics (MHD) free convection fluid flow past a semi-infinite vertical plate embedded in a porous medium with heat absorption was formulated. The non dimensional governing equations are formed with the help of suitable dimensionless governing parameter. The resultant coupled non dimensional governing equations are solved by a finite element method. The effect of important physical parameters on the velocity, temperature and concentration are shown graphically and also discussed the skin-friction coefficient, Nusselt number and Sherwood number are shown in tables.

We present a versatile three – dimensional two – phase model for simulating snow drift relocation around buildings utilizing deflection fins of various shapes and sizes. The first phase involves numerically obtaining the air velocity profile around the building and fin using a velocity – pressure Navier – Stokes algorithm, while the second phase involves direct classical simulation of snowfall with particle – particle, particle – surface and one – way particle – gusting wind interactions introduced to control accumulation, erosion, clumping and drifting. Because the simulation technique is direct, it is potentially useful for storms and surfaces with widely varying conditions. We are also able to consider the effect of crosswinds.

Conjugate heat transfer of a nanofluid containing Al2O3 nanoparticles dispersed in a mixture of 60% ethylene glycol and 40% water by mass (60:40 EG/W) in a two dimensional microchannel has been solved numerically. The effect of axial conduction in both solid and liquid regions has been considered in a range of Reynolds numbers in laminar regime. The utilized nanofluid models are capable of considering variation of thermal conductivity and dynamic viscosity with temperature. The results show that using nanoparticles with higher thermal conductivities will enhance heat transfer characteristics of the channel. Comparing the nanofluid with pure mixture revealed that adding nanoparticles will decrease conduction number which is a scale of axial conduction. Also, it was found that considering variable properties will cause severe changes to the Nusselt number distribution especially for low Reynolds numbers.

In this paper, vorticity confinement parameters are successfully developed for compressible flows. The first new confinement parameter is proportional to spectral radii of the flux Jacobian matrix. Therefore, the confinement parameter implicitly contains the local conditions of the flow field. This new method is named as lambda vorticity confinement method. In order to gain confidence in the applicability of vorticity confinement, it would be ideal to completely eliminate constant coefficients from confinement parameters. Because these constant coefficients should be determined for every problem by trial and error and it takes a long time. In the next part of this paper, a suitable relation is introduced for the vorticity confinement parameter that doesn’t need any constant coefficient. This new method is named as adaptive vorticity confinement method. Then the capability of these new methods is compared with the other vorticity confinement methods for solving shock-vortex interaction and three dimensional moving vortex problems.

This paper describes the design, construction, and testing of a small wave flume and associated equipment. The wave flume is equipped with a flap-type wave generator, capable of producing both regular and irregular waves. Flap paddle is used to examine deep water and floating structures. Instrumentation includes three capacitive wave gauges. The wave-maker is controlled by a desktop computer, which also provides data-logging capability. In order to design a wave absorber of restricted length, all the different mechanisms able to dissipate wave energy studied. Finally from the survey of the wave absorbers used in different laboratories, a gravel beach designed for absorbing the waves coming from wave maker. By sealing leaks around paddle the error of measuring height-to-stroke ratios versus relative depth is decreased by 3%. The main advantage of this system over the previous ones is reduction of the amount of effort in the set up with optimum deflection and low level cost utility.

The problem of a transient three dimensional MHD flow of an electrically conducting viscous incompressible rotating fluid past an impulsively started infinite horizontal porous plate taking into account the Hall current is presented. It is assumed that the fluid rotates with a constant angular velocity about the normal to the plate and a uniform magnetic field applied along the normal to the plate and directed into the fluid region. The magnetic Reynolds number is assumed to be so small that the induced magnetic field can be neglected. The non-dimensional equations governing the flow are solved by Galerkin finite element method. The expressions for the primary and secondary velocity fields are obtained in non-dimensional form. The effects of the physical parameters like M (Hartmann number), Ω (Rotation parameter) and m (Hall parameter) on these fields are discussed through graphs and results are physically interpreted.

In the present investigations, effect of streamwise end wall fences on the performance improvement of a turbine is studied. The fences with heights of 12 mm, 16 mm were attached normal to the end wall and at a half pitch away from the blades. A miniaturized pressure probe was traversed at the exit of the cascade from midspan to the end wall at 26 locations covering more points in the end wall region. For each spanwise location, the probe was traversed in the pitchwise direction for more than 25 points covering one blade pitch. The boundary layer fence near the end wall remains effective in changing the path of pressure side of leg of horseshoe and weaken the cross flow. The overturn in flow has reduced near the end wall when fences are incorporated while outside end wall and in loss core region, it underturns slightly as result of reduction in secondary loss. The total loss is reduced by 15%, 25% for fences of height 12 mm, and 16 mm respectively. The corresponding change was obtained in the drag and lift coefficients.

The radiation effects on unsteady flow of a viscous incompressible fluid past an exponentially accelerated infinite isothermal vertical plate with uniform mass diffusion is considered in the presence of magnetic field and heat source.The governing partial differential equations are converted into a non-dimensional form and solved numerically by applying a Crank-Nicholson type of implicit finite difference method with a tri-diagonal matrix manipulation and an iterative procedure. The profiles of unsteady velocity, temperature and concentration are shown graphically for different values of thermo physical parameters. Also, the simulated values of the skin-friction coefficient, Nusselt number and Sherwood number are presented. This model finds applications in solar energy collection systems,geophysics and astrophysics, aero space and also in the design of high temperature chemical process systems.