

Effects of Hall Current on Unsteady MHD Couette Flow of ClassII in a Rotating System


Pages :
473484


Authors :
G. S. Seth,
J. K. Singh,
Unsteady hydromagnetic Couette flow of classII of a viscous incompressible electrically conducting fluid in a rotating system with Hall effects in the presence of a uniform transverse magnetic field is studied. Both the fluid and plates of the channel are assumed to be at rest when time and fluid flow within the channel is induced due to nontorsional oscillations of the upper plate in its own plane with a velocity about a nonzero uniform velocity at time . Exact solution of the governing equations is obtained by Laplace transform technique. Asymptotic behavior of the solution is analyzed for small and large values of rotation parameter and magnetic parameter when time t>>1. The numerical values of the fluid velocity are depicted graphically whereas that of shear stress at the plates are presented in tabular form for various values of Hall current parameter , rotation parameter , magnetic parameter and frequency parameter .





Rotation Effects on Unsteady Flow Past an Accelerated Isothermal Vertical Plate With Variable Mass Transfer in the Presence of Chemical Reaction of First Order


Pages :
485490


Authors :
R. Muthucumaraswamy,
N. Dhanasekar,
G. E. Prasad,
An exact analysis of rotation effects on unsteady flow of an incompressible and electrically conducting fluid past a uniformly accelerated infinite isothermal vertical plate with variable mass diffusion, under the action of transversely applied magnetic field has been presented. The plate temperature is raised to Tw and the concentration level near the plate is raised linearly with time. The dimensionless governing equations are solved using Laplacetransform technique. The velocity profiles, temperature and concentration are studied for different physical parameters like magnetic field parameter, chemical reaction parameter, thermal Grashof number, mass Grashof number, Schmidt number, Prandtl number and time. It is observed that the velocity increases with increasing values of thermal Grashof number or mass Grashof number. It is also observed that the velocity increases with decreasing magnetic field parameter or rotation parameter Î©.





Numerical Investigation of Turbulent Natural Convection for a Cavity Having Sinusoidal Protuberances on a Vertical Wall


Pages :
491499


Authors :
K. Rahmani,
A. Bentebbiche,
B. Draoui,
This work concerns the study of heat transfer by means of natural convection with fluids circulating in enclosures. These topics are largely studied both experimentally and numerically due to their wide industrial application in various fields such as nuclear energy, the heating and cooling of buildings, solar collectors, etc. A great deal of relevant research work consists in numerical simulations of natural convection mechanisms with laminar flows in closed cavities. In this context, the present study comes as a contribution in numerical form investigating the turbulent natural convection in vertical enclosure which presents sinusoidal protuberances on one of its vertical walls. Both the top and bottom of the enclosure are open to allow the fluid flow. The horizontal walls are supposed adiabatic.
We are interested in determining for various amplitudes and periods. The influence of geometry on several factors such as: temperature, the number of local Nusselt, the turbulent kinetic energy k and its dissipationï¥. Based on the NavierStokes equations and Boussinesq approximation, the equations were solved by the CFD technique using the Finite Volume Method In the case of enclosures having the form ratio equal to 0.6 (A=0.6). Given the steady conditions of heat flow on the vertical walls and the pressures at the entry and exit of the cavity, the results show that when we gradually increase the amplitudes of the protuberance wall (say a=0.005 m, a=0.010, a=0.015, a= 0.02, and a=0.025), the maximal temperature increases with the increase of amplitude. This is due to the rise of the heat transfer surface of the modified wall. Regarding heat transfer parameters, the results show that the number of local Nusselt varies relatively with the amplitudes. This explains that the modified wall is affected locally by a pure conduction. The results obtained in this study are in agreement with recent works of several authors.





Numerical Analysis of Laminar Natural Convection in a Quadrantal Cavity with a Solid Adiabatic Fin Attached to the Hot Vertical Wall


Pages :
501510


Authors :
P. K. Bose,
D. Sen,
R. Panua,
A. K. Das,
Numerical analysis of laminar natural convection in a quadrantal cavity filled with water having finned hot and cold on adjacent walls have been made to examine heat and fluid flow. Numerical solutions are obtained using a commercial computational fluid dynamics package, FLUENT, using the finite volume method. Effects of the Rayleigh number, Ra, nondimensional fin location and nondimensional fin length on the Nusselt number, Nu, as well as stream function and temperature fields are investigated for the range of Ra from 104 to 107.





Fluid Simulation of the Ion Temperature Effects on a Collisional Magnetized Sheath of a Dusty Plasma


Pages :
511517


Authors :
I. Driouch,
H. Chatei,
The properties of magnetized dusty plasma sheath with finite ion temperature are studied using a fluid model. Hot electrons, fluid ions, neutral particles and cold fluid dust grains are taken into account in this system. Considering the cross section for collisions between the dust and neutrals has a power law dependence on the dust flow velocity, the fluid model is then solved numerically to obtain detailed sheath information under different ion temperatures. A significant change is observed in the quantities characterizing the sheath with respect to the cold ion assumption. In addition, the result reveals that the effect of ion temperature is more obvious on the dust dynamics in collisional sheath with constant cross section.





Numerical Nanofluid Simulation with Finite Volume LatticeBoltzmann Enhanced Approach


Pages :
519527


Authors :
J. Ghasemi,
S. E. Razavi,
In this paper, the finite volume LatticeBoltzmann method is used to model the thermofluid behavior of nanofluid, in which nanoparticles are dispersed. The major internal and external forces including Brownian, repulsion and attracting DLVO, drag and buoyancy acting on nanoparticles are taken into account. All these forces make the thermal and dynamic mechanism inside the nanofluid improved. These models are established to simulate and enhance the heat transfer properties of nanoparticles in the CuOH2O nanofluid as a test case. Also, convective heat transfer coefficient of the nanofluid is computed in different Reynolds numbers. The numerical approach is based on a modified and robust finite volume method.





Investigation of Flow Field in a Typical Hypersonic Wind Tunnel over a Standard Mode


Pages :
529536


Authors :
F. Mohammadifard,
M. Karami,
M. Heidari,
In order to start designing a new hypersonic wind tunnel, it is important to have a preview about physical phenomena in a typical Hypersonic Wind Tunnel (HWT). In present research, it is tried to view phenomenologically the aerodynamics of flow in a typical HWT by Computational Fluid Dynamics (CFD). The considered HWT consists of a curved nozzle in nominal Mach number 12, freejet type test section, a test model and a convergentdivergent diffuser. Aerodynamics of flow in the nozzle exit and test section, conical shock wave system in the diffuser and flow over a standard model (HB2) are investigated. A method is introduced for numerical simulation of capturing the free shear layer in freejet test section based on the vorticity distribution of flow. The aerodynamics behavior of HB2 model is investigated in various Mach numbers and flow domains. The results make a better view of some aerodynamic phenomena in a freejet type test section of wind tunnel that are rarely considered. This research is conducted towards the project of designing and manufacturing the industrial hypersonic wind tunnel for Qadr Aerodynamic research Center.





DTMPade Approximants for MHD Flow with Suction/Blowing


Pages :
537543


Authors :
M. Thiagarajan,
K. Senthilkumar,
In this paper, we study theoretically the magnetic effect of Blasius equation with suction/blowing. The similarity transformations are applied to reduce the governing partial differential equations to a set of nonlinear ordinary differential equations in dimensionless form. A mathematical technique, namely the Differential Transform Method (DTM), is used to solve the nonlinear differential equations under appropriate boundary conditions, in the form of series with easily computable terms. Then, Pade approximants are applied to the solutions to increase the convergence of the given series. The combined DTMPade procedure is implemented directly without requiring linearization, discretization or perturbation. Graphical results are presented to investigate influence of the Magnetic field on the velocity profiles.





Soret and Dufour Effects on Transient Double Diffusive Free Convection of Couplestress Fluid past a Vertical Cylinder


Pages :
545554


Authors :
H. P. Rani,
G. J. Reddy,
This study examines the influence of Soret and Dufour effects on double diffusive transient free convective boundary layer flow of a couplestress fluid flowing over a semiinfinite vertical cylinder. A set of nondimensional governing equations namely, the continuity, momentum, energy and concentration equations is derived and these equations are unsteady nonlinear and coupled. As there is no analytical or direct numerical method available to solve these equations, they are solved by using the CFD techniques. An unconditionally stable CrankNicolson type of implicit finite difference scheme is employed to obtain the discretized forms of governing equations. These equations are solved using the Thomas and pentadiagonal algorithms. The numerical results are compared and found to be in good agreement with previously published results as special cases of the present investigation. Transient velocity, temperature and concentration profiles, average skinfriction, Nusselt number and Sherwood number are shown graphically for different values of Soret (So) and Dufour (Du) numbers. In all these profiles it is observed that, as the values of So decreases or the Du increases, the time required to reach the temporal maximum and the steadystate increases. It is also observed that the average values of skinfriction and heat transfer rate increases with the increasing values of So or decreasing values of Du. Whereas the reverse trend is observed for the average mass transfer rate.





Effect of Cold Spraying Parameters and Their Interaction an Hydroxyapatite Deposition


Pages :
555561


Authors :
R. P. Singh,
U. Batra,
Cold spraying has been effectively investigated for spraying of various metals, alloys and composites. Coating of bioceramics like Hydroxyapatite (HAP) using thermal spraying has been investigated extensively, but there is a dearth of research related with HAP deposition using cold spraying. The relative percentage contribution of five important cold spraying parameters, their optimum combination and expected HAP particle velocity at optimum combination have been extensively discussed by the author, but no researcher reported the interactional effect of cold spraying parameters on HAP particle velocity. This paper examined the severity index of interactional effect of five important factors of cold spraying viz. gas type, gas inlet pressure, gas inlet temperature, particle size and particle temperature on HAP particle velocity. Most influential factor pairs and their influence on HAP particle velocity have been discussed with respect to various cold spraying gases viz. air, hydrogen, nitrogen and helium. In addition, CFD gas pressure and temperature distributions along the nozzle length and their mathematical validation have also been undertaken in the present paper.





Radiative Heat Transfer with MHD Free Convection Flow over a Stretching Porous Sheet in Presence of Heat Source Subjected to Power Law Heat Flux


Pages :
563569


Authors :
H. Kumar,
The study of flow and heat transfer in fluid as it passes over a porous surface has attracted considerable scientific attention, particularly in technologies where boundarylayer control is important. Therefore, this paper reports the effects of radiation and heat source over a stretching surface subjected to a power law heat flux, in the presence of transverse magnetic field on twodimensional boundary layer steady flow and heat transfer of a viscous incompressible fluid. Heat transfer equation is reduced to a linear differential equation using nondimensional parameters and the exact solution is obtained in the form of confluent hypergeometric function (Kummer’s Function) for prescribed power law wall temperature. The effects of the various parameters entering into the problem on the temperature distribution and wall temperature gradient are discussed.





Passive Control via Slotted Blading in a Compressor Cascade at Stall Condition


Pages :
571580


Authors :
M. Ramzi,
G. AbdErrahmane,
This paper was conducted to explore the potential of passive control via slotted bladings in linear cascade configurations under stall condition. Through an extensive 2Dnumerical study, the effects of location, width and slope of slots were analyzed and the best configuration was identified. Based on the optimal slot, the 3D aerodynamic performances of cascade were studied and the influence of slotted blading to control endwall flow was investigated. Both 2D and 3D calculations are performed on steady RANS solver with standard kepsilon turbulence model and low Mach number regime. The total loss coefficient, turning angle and flow visualizations on the blade and endwall surfaces are adopted to describe the different configurations. The obtained results show, for 2D situation, that a maximum of almost 28% reduction in loss coefficient had been reached and the flow turning was increased with approximately 50. Concerning 3D flow fields the slots marked their benefit and delays the boundary layer separation on both end wall and blade suction surface at mid span.





Chemical Reaction and Mass Transfer Effects on Flow of Micropolar Fluid past a Continuously Moving Porous Plate with Variable Viscosity


Pages :
581588


Authors :
P. Loganathan,
N. G. Stepha,
Chemical reaction and mass transfer effects on flow of a micropolar fluid past a continuously moving porous plate with variable viscosity is investigated numerically. The plate is moving with a constant velocity in the fluid, which has a temperature dependent viscosity. The fluid viscosity is considered to vary linearly with temperature. The radiative heat flux and the viscous dissipation are taken into account in the energy equation. The partial differential equations governing the flow have been transformed into system of ordinary differential equation and solved numerically by fourth order RungeKutta method with shooting technique. The velocity, microrotation, temperature, concentration are shown graphically for different value of suction or injection parameter as well as temperature dependent viscosity parameter. The rate of mass transfer for different values of chemical reaction parameter and variable viscosity parameter is also shown graphically. The result shows that chemical reaction parameter and variable viscosity parameter have significant influence on heat and mass transfer rate. Effect of chemical reaction parameter and variable viscosity parameter over skinfriction coefficient and microrotation are examined.





A Magnetoconvection Over a Semi infinite Porous Plate with Heat Generation


Pages :
589595


Authors :
T. Raja,
S. Karthikeyan,
B. Senthilnathan,
Convective flow through porous media is a branch of research undergoing rapid growth in fluid mechanics and heat transfer. This is quite natural because of its important applications in environmental, geophysical and energy related engineering problems. Prominent applications are the utilization of geothermal energy, the control of pollutant spread in ground water, the design of nuclear reactors, solar power collectors and the heat transfer associated with the deep storage of nuclear waste. The study of heat generation in moving fluids is important in problems dealing with chemical reactions and those concerned with dissociating ﬂuids. Heat generation effects may alter the temperature distribution and this in turn can affect the particle deposition rate in nuclear reactors, electronic chips and semi conductor wafers. Although exact modeling of internal heat generation is quite difficult, some simple mathematical models can be used to express its general behaviour for most physical situations. The objective of this work is to investigate the effects of internal heat generation on an unsteady twodimensional magnetohydrodynamic free convection flow of a viscous, incompressible fluid free convection flow past a semiinfinite vertical porous plate embedded in a porous medium, in the presence of variable suction. The equations of continuity, linear momentum and energy, which govern the flow field, are transformed to a system of ordinary differential equations by perturbation technique. The resulting equations are solved analytically to obtain the solutions for the velocity and temperature fields. The behavior of the velocity, temperature, skinfriction and Nusselt number have been discussed for variations in the physical parameters.





Analytical and Numerical Study for MHD Radiating Flow over an Infinite Vertical Surface Bounded by a Porous Medium in Presence of Chemical Reaction


Pages :
597607


Authors :
S. Ahmed,
K. Kalita,
The study of nonlinear MHD flow with heat and mass transfer characteristics of an incompressible, viscous, electrically conducting and Newtonian fluid over a vertical oscillating porous plate embedded in a porous medium in presence of homogeneous chemical reaction of first order and thermal radiation effects have been analyzed. The fluid considered here is a gray, absorbing/emitting radiation, but a nonscattering medium. At timet>0, the plate temperature and concentration levels near the plate raised linearly with timet. The dimensionless governing coupled, nonlinear boundary layer partial differential equations are solved by an efficient, accurate, and extensively validated and unconditionally stable finite difference scheme of the CrankNicolson type as well as by the Laplace Transform technique. An increase in porosity parameter (K) is found to depress the fluid velocities and shear stress in the regime. Also it has been found that, when the conductionradiation (R) increased, the fluid velocities as well as temperature profiles were decreased. It has been found that, when the chemical reaction parameter(C_r) increased, the fluid velocities as well as concentration profiles were decreased. Applications of the study arise in materials processing and solar energy collector systems.





Inertia Effects in Rheodynamic Lubrication of an Externally Pressurized Thrust Bearing Using Bingham Lubricant with Sinusoidal Injection


Pages :
609616


Authors :
I. J. Amalraj,
S. Narasimman,
A. Kandasamy,
In the present theoretical investigation, the combined effects of fluid inertia forces and sinusoidal injection of the Bingham lubricant, on the performance of an externally pressurized thrust bearing with circular geometry are studied. Using the conventional twoconstant Bingham model and by adopting the method of averaging inertia terms, the reduced NavierStokes equations are modified and numerical solutions have been obtained for the bearing performances such as the pressure distribution and the load carrying capacity for different values of Bingham number, Reynolds number, time and amplitude. The effects of fluid inertia forces and the nonNewtonian characteristics of the Bingham lubricant on the bearing performances for different sinusoidal conditions are discussed.





