

Mixed Convection Flow from Vertical Plate Embedded in NonNewtonian Fluid Saturated Non Darcy Porous Medium with Thermal DispersionRadiation and Melting Effects


Pages :
385394


Authors :
J. S. R. Prasad,
K. Hemalatha,
B. D. C. N. Prasad,
We analyzed in this paper the problem of mixed convection along a vertical plate in a nonNewtonian fluid saturated nonDarcy porous medium in the presence of melting and thermal dispersionradiation effects for aiding and opposing external flows. Similarity solution for the governing equations is obtained for the flow equations in steady state. The equations are numerically solved by using RungeKutta fourth order method coupled with shouting technique. The effects of melting, thermal dispersion, radiation, temperature ratio, inertia and mixed convection on velocity distribution and temperature are examined for aiding and opposing external flows.





CFD Investigation of Influences of Reverse Textures on Bearing Surface of a Journal Bearing


Pages :
395399


Authors :
S. Mishra,
A. Choudhury,
S. Sahu,
It has always been the subject of interest and research to find out most efficient method to minimize the
frictional loss of any mating surface in any mechanism. But it has been identified that only improvement of
lubricating material cannot help much. For this reason research on design modification was started and still
going on to optimize the design of mating surfaces so that losses be minimum. In this paper a research has
been done on the design of bearing surface of a journal bearing. Journal bearing is a very important part of
many machines specially turbines used in Power generation and rolling mills used in steel making sectors. By
modifying the design of the bearing surface, load carrying capacity of a journal bearing can be increased and
thus its performance can be improved. It is proved by many researches that, by putting cylindrical dimples on
bearing surface the performance of a journal bearing can be increased. To measure the performance of a
journal bearing three parameters are usually used. Those are, (i) Load Carrying Capacity, (ii) Frictional
resisting force and (iii) Ratio of Frictional resistance and Load carrying capacity, which is called Frictional
coefficient. In this work a modification has been done on the work of Cupillard. Cupillard considered only
the cylindrical dimples for the sake of manufacturing simplicity, but in this work a different configuration of
dimple has been considered and its influence on bearing performance has been studied.
It is proved by many researches that, by putting cylindrical dimples on bearing surface the performance of a journal bearing can be increased. To measure the performance of a journal bearing three parameters are usually used. Those are, (i) Load Carrying Capacity, (ii) Frictional resisting force and (iii) Ratio of Frictional resistance and Load carrying capacity, which is called Frictional coefficient.
In this work a modification has been done on the work of Cupillard at all (reference [9]). Cupillard considered only the cylindrical dimples for the sake of manufacturing simplicity, but in this work a different configuration of dimple has been considered and its influence on bearing performance has been studied.





A Study of the Asymptotic Equilibrium Behavior in Stratified Turbulence Submitted to Horizontal Shear


Pages :
401413


Authors :
L. Thamri Naffouti ,
T. Lili,
M. Bouzaiane,
In this work, the asymptotic equilibrium behaviour of dimensionless parameters in stably stratified turbulence
submitted to a horizontal shear is studied using two different methods. The first one is an analytic method and
is based on linear solutions obtained when non linear effects of pressure and viscosity are neglected. The
Laplace Transform is used for integrating differential system. The principal result of this first part of our
work is the existence of asymptotic equilibrium states at high shear for all non dimensionless parameters. The
second method is a numerical one and is based on a secondorder modeling of equations. The Speziale Sarkar
and Gatski (SSG) model is retained for pressurestrain correlation and dissipation time evolution equation,
whereas, three of the most known secondorder models are retained for the scalar field. The principal result of
this second part is the big contribution of the SSG models for predicting asymptotic equilibrium states of non
dimensional parameters.





Numerical Simulation of Magnetohydrodynamic Forced Convective Boundary Layer Flow past a Stretching/Shrinking Sheet Prescribed with Variable Heat Flux in the Presence of Heat Source and Constant Suction


Pages :
415423


Authors :
S. P. Anjali Devi,
J. W. S. Raj,
A study has been carried out on MHD boundary layer forced convection flow along a shrinking surface with variable heat flux in the presence of heat source. The flow is generated due to linear shrinking of the sheet and is influenced by uniform transverse magnetic field. The basic boundary layer momentum and heat transfer equations, which are nonlinear partial differential equations, are converted into nonlinear ordinary differential equations by means of similarity transformation. Numerical solution of the resulting boundary value problem is obtained using Nachtsheim Swigert shooting iteration scheme for the satisfaction of asymptotic boundary conditions along with the Fourth Order Runge Kutta method. The effects of suction parameter, magnetic parameter, Prandtl number, heat source parameter, stretching/shrinking parameter and heat flux parameter on velocity and temperature are shown in several plots. The results are in good agreement with the earlier published works under some limiting cases. Skin friction coefficient and wall temperature are also explored for typical values of the parameter involved in the study.





Effect of NonUniform Heat Generation on Unsteady MHD NonDarcian Flow over a Vertical Stretching Surface with Variable Properties


Pages :
425434


Authors :
M. Muthtamilselvan,
D. Prakash,
D. H. Doh,
The effect of nonuniform heat generation on an unsteady MHD laminar boundary layer flow of viscous, incompressible fluid over a vertical stretching plate embedded in a sparsely packed porous medium is investigated numerically. The flow in the porous medium is governed by BrinkmanForchheimer extended Darcy model. The variation of porosity, permeability and thermal conductivity is assumed. By applying similarity analysis, the governing partial differential equations are transformed into a set of time dependent nonlinear coupled ordinary differential equations and they are solved by RungeKutta Fehlberg Method along with shooting technique. The effects of governing parameters on the dimensionless velocity and temperature distributions for uniform permeability (UP) and variable permeability (VP) of the porous medium are discussed graphically. Also, the local skin friction coefficient and the rate of heat transfer are computed for various pertinent parameters governing the problem. Moreover, the numerical results obtained in this study is compared with the existing literature and found they are in good agreement.





A Novel Strategy for Designing and Manufacturing a Fixed Wing MAV for the Purpose of Increasing Maneuverability and Stability in Longitudinal Axis


Pages :
435446


Authors :
M. Radmanesh,
O. Nematollahi,
M. NiliAhmadabadi,
M. Hassanalian,
In this study, a novel simple strategy is proposed to choose and accommodate an airfoil based on the effects
of airfoil type and planform shape on the flight performance of a micro air vehicle. In this strategy, after
defining flight mission, the weight of the micro air vehicle is estimated and then, aerodynamic parameters and
thrust force are calculated. In the next step, some different planforms and airfoils are investigated to be
selected for decreasing the stall region in high attack anglesby open source software named XFLR5. Having
calculated the aerodynamic center, the pitching moment needed to stabilize the micro air vehicle is computed.
Due to the static margin, the airfoil camber line is changed to stabilize the micro air vehicle and then, its
thickness is improved to reach to a high aerodynamic characteristic. To evaluate the software results, some
flight tests are performed which then compared to the software results that show a good agreement. Finally,
some adjustments and improvements are made on the micro air vehicle and then, its performance is obtained
by the flight tests. The flight test results show it has an excellent aerodynamic performance, stability and
maneuverability.





DiffusionThermo and Thermaldiffusion Effects on MHD ViscoElastic Fluid Flow over a Vertical Plate


Pages :
447458


Authors :
D. Yasmin,
T. Ahmed,
N. N. Anika,
M. M. Mukitul Hasan,
M. Mahmud Alam,
Unsteady MHD viscoelastic fluid flow has been studied numerically under the action of transverse magnetic field with diffusionthermo and thermal diffusion for small magnetic Reynolds number. The governing equations are nondimensionalized by usual nondimensional variables. The obtained equations are solved by explicit finite difference technique. The solutions of the dimensionless velocity, temperature and concentration equations are shown graphically. The effects of parameters on the shear stress, Nusselt number and Sherwood number are discussed in graphical form. Finally, a qualitative comparison with previous work is tabulated.





Linear Stability Analysis of Double Diffusive Convection in a Horizontal Sparsely Packed Rotating Anisotropic Porous Layer in Presence of Soret Effect


Pages :
459471


Authors :
S. N. Gaikwad,
S. S. Kamble,
In this paper, we have investigated theoretically the effect of Soret parameter on the onset of double diffusive
rotating anisotropic convection in a horizontal sparsely packed porous layer using linear stability theory
which is based on the usual normal mode technique. The Brinkman model that includes the Coriolis term is
employed for the momentum equation. The effect of anisotropy parameters, Soret parameter, solute Rayleigh
number, Taylor number, Lewis number, Darcy and Darcy Prandtl number on stationary and oscillatory
convection is shown graphically.





Numerical Study of Generalized ThreeDimensional MHD Flow over a Porous Stretching Sheet


Pages :
473483


Authors :
M. Heydari,
G. B. Loghmani,
A. A. Dehghan,
In this paper a numerical method for solving generalized threedimensional magnetohydrodynamic (MHD) flow of an incompressible viscous fluid over a porous stretching sheet is proposed. This approach is based on Legendre pseudospectral method with a positive scaling factor and extrapolation. The present method solves the problem on the semiinfinite domain without truncating it to a finite domain. In addition, this method reduces the solution of the problem to solution of a system of algebraic equations. The obtained numerical results are compared with some wellknown results to confirm the accuracy and efficiency of the proposed scheme.





Unsteady Hydromagnetic Flow of a Heat Absorbing Dusty Fluid Past a Permeable Vertical Plate with Ramped Temperature


Pages :
485492


Authors :
M. Das,
B. K. Mahatha,
R. Nandkeolyar,
B. K. Mandal,
K. Saurabh,
The unsteady flow and heat transfer of a viscous incompressible, electrically conducting dusty fluid past vertical plate under the influence of a transverse magnetic field is studied with a view to examine the combined effects of suction, heat absorption and ramped wall temperature. The temperature of the wall is assumed to have a temporarily ramped profile which goes on increasing up to a certain time limit and then becomes constant. To investigate the effect of rampedness in wall temperature, the solution for the flow past an isothermal wall is also obtained. The governing partial differential equations are solved using Laplace transformation technique in which the inversion is obtained numerically using Matlab. To validate the results of numerical inversion a comparison between the numerical and analytical values of fluid and particle temperatures and Nusselt number is also presented. The effects of pertinent flow parameters affecting the flow and heat transfer are investigated with the help of graphs and tables. It is found that the increase in suction, heat absorption and particle concentration contribute in thinning the thermal and momentum boundary layers and the velocity and temperature for both the fluid and particle phases are higher in the case of a flow past an isothermal plate than that of a flow past a plate with ramped temperature.





Numerical Study of Sinusoidal Temperature in Magneto Convection


Pages :
493502


Authors :
H. Jamai,
S. O. Fakhreddine,
H. Sammouda,
In this paper we would like to present a numerical study of the effect of magnetic fields on natural convection
(magnetoconvection) flow of electrically conducting fluid. The 2D square cavity which was studied is
subjected to a sinusoidal temperature conditions. The left and the right walls were respectively heated and
cooled with a sinusoidal temperature while the top wall was kept thermally insulated. The equations are
solved numerically by employing finite element method (MEF) using the software COMSOL Multiphysics.
We presented the results in wide range of Hartmann number and Rayleigh number in terms of isotherm
contours, velocities fields streamlines, , and in an average and local Nusselt number which varies
sinusoidally. Our results are shown to be in good conformity with the available benchmark solutions.





Radiation Effect on MHD Fully Developed Mixed Convection in a Vertical Channel with Asymmetric Heating


Pages :
503512


Authors :
R. Patra,
S. Das,
R. Nath Jana,
Effects of radiative heat transfer on MHD fully developed mixed convective flow of a viscous incompressible electrically conducting fluid through a vertical channel with asymmetric heating of the walls in the presence of a uniform transverse magnetic field has been studied. An exact solution of the governing equations has been obtained in closed form. It is observed that the velocity field is greatly influenced by the radiative heat transfer as well as bouyancy forces. The induced magnetic field decreases at any point near the left wall and it increases near the right wall of the vertical channel with increase in radiation parameter. Further, an increase in radiation parameter leads to a decrease in the temperature at
any point of the channel flow. A limiting consideration of the solutions of the governing equations of the flow are analyzed for Ra<<1.





SoretDufour Effects on Hydromagnetic NonDarcy ConvectiveRadiative Heat and Mass Transfer over a Stretching Sheet in Porous Medium with Viscous Dissipation and Ohmic Heating


Pages :
513523


Authors :
D. Pal,
H. Mondal,
The present study is devoted to investigate the effects of Soret and Dufour on the mixed convection flow, heat
and mass transfer over a stretching sheet in the presence of viscous dissipation, Ohmic heating, thermal radiation in porous medium. Numerical solutions for the coupled governing equations are obtained by using the fifthorder RungeKuttaFehlberg method with shooting technique. Important features of flow, heat and mass transfer characteristics for different values of the physical parameters are analyzed and discussed. Numerical results reveal that the magnetic field and inertia coefficient reduce the skin friction but reverse effects are seen on local Nusselt number.





Experimental Investigation of “Why an AC Dielectric Barrier Discharge Plasma Actuator is Preferred to DC Corona Wind Actuator in Boundary Layer Flow Control?”


Pages :
525534


Authors :
G. Tathiri,
E. Esmaeilzadeh,
S. M. Mirsajedi,
H. Mahdavi Moghaddam,
In this paper, characteristics of the flow induced in the boundary layer by an ACDielectric Barrier Discharge (DBD) plasma actuator are compared against those of a DCcorona wind actuator. This is achieved by visualization of the induced flow using smoke injection and measuring the horizontal induced velocity. Our measurements show that the maximum induced velocity of an ACDBD actuator is about one order of magnitude larger than that of a DCcorona actuator. For an ACDBD actuator, the induced velocity is maximized on the plate surface while for a DCcorona actuator the induced velocity peaks at about 20mm above the surface. Using flow visualization, we demonstrate that the induced velocity of an ACDBD actuator is parallel to the surface, while the induced velocity of a DCcorona actuator has components perpendicular to surface.





Heated Permeable Stretching Surface in a Porous Medium Using Nanofluids


Pages :
535542


Authors :
M. Sheikholeslami,
D. D. Ganji,
In this article, twodimensional laminarforced convection nanofluids flow over a stretching surface in a
porous medium has been studied. The governing partial differential equations with the corresponding
boundary conditions are reduced to a set of ordinary differential equations with the appropriate boundary
conditions using similarity transformation, which is then solved numerically by the fourth order Runge–Kutta
integration scheme featuring a shooting technique. Different models of nanofluid based on different formulas
for thermal conductivity and dynamic viscosity are used. Different types of nanoparticles as copper, silver,
alumina and titanium Oxide with water and Ethylene glycol as their base fluids has been considered. The
influence of significant parameters such as nanoparticle volume fraction, kind of nanofluid, Magnetic
parameter and Reynolds number on the flow and heat transfer characteristics is discussed. The influence of
significant parameters such as Thermal conductivity parameter, volume fraction of the nanoparticles,
Permeability parameter, suction/injection parameter and Velocity ratio parameter on the flow and heat
transfer characteristics is discussed. It was found that choosing Titanium oxide as the nanoparticle and
Ethylene glycol as base fluid proved to have the highest cooling performance for this problem.





Finite Element Simulation of Forced Convection in a Flat Plate Solar Collector: Influence of Nanofluid with Double Nanoparticles


Pages :
543556


Authors :
R. Nasrin,
M. A. Alim,
This work compares heat loss characteristics across a riser pipe of a flat plate solar collector filled water based nanofluid of double nanoparticles (alumina and copper) with single nanoparticle (alumina). Also this study compares heat transfer phenomena among four nanofluids namely watercopper oxide, wateralumina, watercopper and watersilver nanofluids. Comparisons are obtained by numerically solving assisted convective heat transfer problem of a cross section of flat plate solar collector. Governing partial differential equations are solved using the finite element simulation with Galerkin’s weighted residual technique. The average Nusselt number (Nu) at the top hot wall, average temperature (θav), mean velocity (Vav), percentage of collector efficiency (η), midheight dimensional temperature (T) for both nanofluid and base fluid through the collector pipe are presented graphically. The results show that the better performance of heat loss through the riser pipe of the flat plate solar collector is found by using the double nanoparticles (alumina and copper) than single nanoparticle (only alumina). When comparing the four nanofluids considering the same solid volume fraction ( = 5%), this study claims that the average Nusselt number for waterAg nanofluid is higher than others.





