
Stokes Flow over Composite Sphere: Liquid Core with Permeable Shell


Pages :
339350


Authors :
bharat raj jaiswal,
B. R. Gupta,
This paper presents an analytical study of an infinite expanse of uniform flow of steady axisymmetric Stokes flow of an incompressible Newtonian fluid around the spherical drop of ReinerRivlin liquid coated with the permeable layer with the assumption that the liquid located outside the capsule penetrates into the permeable layer, but it is not mingled with the liquid located in the internal concave of capsule. The flow inside the permeable layer is described by the Brinkman equation. The viscosity of the permeable medium is assumed to be same as pure liquid. The stream function solution for the outer flow field is obtained in terms of modified Bessel functions and Gegenbauer functions, and for the inner flow field, the stream function solution is obtained by expanding the stream function in terms of S. The flow fields are determined explicitly by matching the boundary conditions at the pure liquidporous interface, porousReinerRivlin liquid interface, and uniform velocity at infinity. The drag force experienced by the capsule is evaluated, and its variation with regard to permeability parameter a, dimensionless parameter S, ratio of viscosities l2, and thickness of permeable layer d is studied and graphs plotted against these parameters. Several cases of interest are deduced from the present analysis. It is observed that the crossviscosity increases the drag force, whereas the thickness d decreases the drag on capsule. It is also observed that the drag force is increasing or decreasing function of permeability parameter for l2 < 1.





The Influence of Heat Transfer on Peristaltic Transport of MHD Second Grade Fluid through Porous Medium in a Vertical Asymmetric Channel


Pages :
351365


Authors :
Ramesh Katta,
M. Devakar,
In this paper, we study the influence of heat transfer on the peristaltic transport of an incompressible magnetohydrodynamic
second grade fluid in vertical symmetric and asymmetric channels. The channel asymmetry is produced by choosing the peristaltic wave train on the walls to have different amplitudes and phase. The flow is investigated in the wave frame of reference moving with velocity of the wave. Perturbation solutions are obtained for the stream function, temperature and pressure gradient under long wave length assumption. Pressure difference and frictional force are discussed through numerical integration. The influence of various parameters of interest on the flow are discussed and also the graphical results are obtained for different wave forms.





A Numerical Assessment of the Air Flow Behaviour in a Conventional Compact Dry Kiln


Pages :
367376


Authors :
Paulo Zdanski,
Daniel Possamai,
Miguel Vaz Jr.,
Convective drying is the most common drying strategy used in timber manufacturing industries in the developing world. In convective drying, the reduction rate of the moisture content is directly affected by the flow topology in the inlet and exit plenums and the air flow velocity in the channels formed by timber layers.Turbulence, boundary layer separation, vortex formation and recirculation regions are flow features that are intrinsically associated with the kiln geometry, which in turn dictate the flow velocity across the timber stack and, ultimately, the drying rate. Within this framework, this work presents a numerical study of the effects of the plenum width and inlet flow velocity in a compact dry kiln aiming to establish design recommendations to ensure the highest possible level of flow uniformity across the lumber stack. The numerical solution of
the mathematical model is obtained through the finitevolume based Ansys CFX R flow solver. Validation of the numerical approximation is performed by comparing numerical and experimental flow velocities for a scale model of a kiln available in the literature.





Turbodrill Design and Performance Analysis


Pages :
377390


Authors :
Amir Mokaramian,
Vamegh Rasouli,
Gary Cavanough,
Turbodrill (turbine down hole motor) has been recently proposed by the authors as the preferred drive mechanism with high rotation speed for hard rocks drilling for deep mineral exploration applications.Turbodrill is a type of hydraulic axial turbomachinery in which turbine motor section has multistage of rotors and stators that convert the hydraulic power provided by the drilling fluid to mechanical power with diverting the fluid flow through the stator vanes to rotor vanes. This paper presents a methodology for designing multistage turbodrills with asymmetric rotor and stator blades configurations. The numerical simulation approach and the simulations results carried out using computational fluid dynamics (CFD) code for the proposed small size model of turbodrill stage with different drilling fluid (mud) types and various mass flow rates are presented. As a result optimum operational parameters are proposed for gaining the required rotation
speed and torque for hard rocks drilling.





A Flow Model for the Settling Velocities of Non Spherical Particles in Creeping Motion. Part III. Slender Bodies, the Stream Functions, the Flow and the Momentum Equation


Pages :
391398


Authors :
Yuri Mendez,
This paper follows previous work regarding the settling velocity of non spherical particles in creeping motion. In this paper, we summarize the flow model, present solutions for the slender plate and the cylinder (Stoke’s paradox), demonstrate the application for euhedral pseudo hexagonal plates (KGa1) and show the match to the experimental data. In addition, we derive the stream function for the sphere, the slender cylinder and the plate, develop the relationships to compute the flow about a settling particle, back calculate the momentum equation and examine the result





A Proposed Solution for the Settling Velocity of Coplanar Aggregates of Identical Spheres in Creeping Motion.


Pages :
399407


Authors :
Yuri Mendez,
This paper derives a solution for the settling velocity of isolated coplanar aggregates of n identical spherical particles in creeping motion based on the Wall ShearPressure GradientExpansion model (WPE) previously derived by the author. The solution is reached by developing geometryequilibrium mathematical constructs to decide on the dimensions of the free ambient expansions surrounding the aggregates to compute the entire velocity profile. A rational to decide on the orientation and stability of rotation is also proposed. The results compare well with the outcome of available theory and some relevant data sets.





Hall Effects on Unsteady Hydromagnetic Flow Past an Accelerated Porous Plate in a Rotating System


Pages :
409417


Authors :
Sanatan Das,
Sankar Kr. Guchhait,
R. N. Jana,
An unsteady hydromagnetic flow of a viscous incompressible electrically conducting fluid past an accelerated porous flat plate in the presence of a uniform transverse magnetic field in a rotating system taking the Hall effects into account have been presented. An analytical solution describing the flow at large and small times after the start is obtained by the use of Laplace transform technique. The influences of the physical parameters acting on the flow are discussed in detail with the help of several graphs. It is found that interplay of Coriolis force and hydromagnetic force in the presence of Hall currents plays an important role in characterizing the flow behavior.





Magnetothermal Stability of Rotating Walters’ (model B') Viscoelastic Compressible Fluid in the Presence of Hall Currents and Suspended Particles in Porous Medium


Pages :
419427


Authors :
K. Kumar,
Vijendra Singh,
Seema Sharma,
In the present paper, the stability of a compressible rotating Walters’ B' viscoelastic fluid through a porous medium is considered in the presence of uniform vertical magnetic field, Hall current and suspended particles. It is found that the region of stability increases with the increase in magnetic field, rotation and compressibility and it decreases with the increase in suspended particles and Hall currents. Also, it has been established that the medium permeability has destabilizing effect in the absence of rotation while in the presence of rotation it may have stabilizing effect on the system. Graphs are plotted to find the region of stability in the presence of various physical parameters like Hall current parameter, suspended particles, rotation, magnetic field and medium permeability. The principle of exchange of stabilities holds good under certain conditions and the modes may be nonoscillatory or oscillatory.





The Radiation Effect on the ThermoMagnetic Convection in Participating Paramagnetic Medium under Microgravity Condition


Pages :
429438


Authors :
Chengan WANG,
JianYu TAN,
The radiation effect on the thermomagnetic convection which occurs in participating paramagnetic medium under microgravity (g = 0) condition is numerically investigated. Different from the electrically conducting fluid, the paramagnetic fluid is driven by Kelvin force which is proportional to the product of magnetic susceptibility and the gradient of the square of the magnetic induction and is introduced into the source term of the NavierStokes equation. In order to realize the fluid flow, an external magnetic field with uniform or nonuniform magnetic gradient is imposed. Further, the thermomagnetic convection is carried out in high temperature field, in which the magnetic susceptibility varies greatly with absolute temperature according to Curie's law, and the radiation field is also modified by the absorbingemitting paramagnetic medium. In the present study, the effects of magnetic Rayleigh number and optical thickness are investigated. The results show that radiative heat transfer plays a significant role in thermomagnetic convection.





A Ghost Fluid Approach for Thermal Lattice Boltzmann Method in Dealing with Heat Flux Boundary Condition in Thermal Problems with Complex Geometries


Pages :
439452


Authors :
Reza Khazaeli,
S. Mortazavi,
Mahmud Ashrafizaadeh,
In this paper, the ghost fluid thermal lattice Boltzmann method is improved to properly impose the heat flux boundary condition on complex geometries [Khazaeli, R., S. Mortazavi and M. Ashrafizaadeh (2013). Application of a ghost fluid approach for a thermal lattice Boltzmann method, J. Comput. Phys. 250, 126– 140]. A doublepopulation thermal lattice Boltzmann method is used to handle both the flow and temperature fields on a Cartesian grid and the boundary conditions are imposed using a ghost fluid method. The method is based on the decomposition of the unknown distribution functions into their equilibrium and nonequilibrium parts at every ghost point. The equilibrium parts are determined by performing an extrapolation of major quantities from the image points to the associated ghost points. The bounceback scheme is then used to determine the non equilibrium parts. The method benefits from some features such as easy implementation
and second order accuracy. The method is applied to simulate natural convection within annuluses with different shapes and boundary conditions,. The obtained results are generally in a good agreement with those predicted by other numerical efforts.





Heat and Mass Transfer by Unsteady Natural Convection over a Moving Vertical Plate Embedded in a Saturated Porous Medium with Chemical Reaction, Soret and Dufour Effects


Pages :
453463


Authors :
A.M. Rashad,
The thermaldiffusion and diffusionthermo effects on heat and mass transfer by transient free convection flow of over an impulsively started isothermal vertical plate embedded in a saturated porous medium were numerically investigated, considering a homogeneous chemical reaction of first order. The transient, nonlinear and coupled governing equations are solved using an implicit finitedifference scheme. The effects of various parameters on the transient velocity, temperature, and concentration profiles as well as heat and mass transfer rates are analyzed. Numerical results for the unsteadystate velocity, temperature and
concentration profiles as well as the axial distributions and the time histories of the skinfriction coefficient, Nusselt number and the Sherwood number are presented graphically and discussed.





Stagnation Point Flow of Thixotropic Fluid over a Stretching Sheet with Mass Transfer and Chemical Reaction


Pages :
465471


Authors :
T. Hayat,
Sabir Shehzad,
Saleem Asghar,
Ahmed Alsaedi,
The stagnation point flow of thixotropic fluid towards a linear stretching surface is investigated. Mass transfer with first order chemical reaction is considered. The resulting partial differential equations are reduced into the ordinary differential equations. Dimensionless velocity and concentration fields have been computed. Graphical plots are presented to illustrate the details of flow and mass transfer characteristics and their dependence upon the physical parameters. Numerical values of surface mass transfer are first computed and then analyzed.





Numerical Study on MHD Mixed Convection Flow in a Vertical Insulated Square Duct with Strong Transverse Magnetic Field


Pages :
473481


Authors :
Muhim Chutia,
Paramananda Deka,
A numerical study on steady laminar magnetohydrodynamics (MHD) mixed convection flow of an electrically conducting fluid in a vertical square duct under the action of transverse magnetic field has been investigated. The walls are assumed as perfectly electrically insulated. In this study both force and free convection flows are considered. The viscous dissipation and Joule heat are also considered in the energy equation and walls of the duct are kept at constant temperature. The enclosure is heated by uniform volumetric heat density. The governing equations of momentum, induction and energy are first transformed into dimensionless equations by using dimensionless quantities, then these are solved employing finite difference method for velocity, induced magnetic field and temperature distribution. The computed results for velocity, induced magnetic field and temperature distribution are presented graphically for different dimensionless parameters Hartmaan number M, Prandtl number Pr, Grashof number Gr and magnetic Reynolds number Rm.





Effect of Periodic Bottom Plate Heating on Large Scale Flow in Turbulent RayleighBénard Convection


Pages :
483489


Authors :
Margarita Kuqali,
Simone Babuin,
Joseph Niemela,
We report analysis of temperature fluctuations measured inside a RayleighBénard convection cell of aspect ratio unity with steady and timevarying heating of the bottom boundary. The working fluid is cryogenic helium gas at Rayleigh number Ra = 1013, for which a large scale coherent flow (mean wind) exists. We observe the wind to occasionally vanish under both steady and timevarying heating conditions. However, with applied periodic modulation of the lower boundary temperature at the frequency of the wind, we can observe destruction of the periodic temperature variation at the cell midplane, due to relative changes in phase between the mean wind and the propagating temperature wave. The wind speed is not observed to change with modulation, demonstrating that it is set by mean properties of the system. Finally we propose that the frequency of the mean wind – and hence the large scale Reynolds number – could be better resolved by finding resonance with applied forcing.





Comparison between Two Local Thermal Non Equilibrium Criteria in Forced Convection through a Porous Channel


Pages :
491498


Authors :
azzedine ABDEDOU,
Khedidja Bouhadef,
Two criteria are used and compared to investigate the local thermal equilibrium assumption in a forced convection through a porous channel. The first criterion is based on the maximum local temperature difference between the solid and fluid phases, while the second is based on the average of the local differences between the temperature of the solid phase and the fluid phase. For this purpose, the momentum and energy equations based on the DarcyBrinkmanForchheimer and the local thermal non equilibrium models are solved numerically using the finite volume method. The analysis focused on searching thermophysical parameters ranges which validate local thermal equilibrium hypothesis. Thus, by using the two criteria, the obtained results mainly revealed that this local thermal equilibrium assumption is verified for low thermal conductivity ratio and Reynolds number values and for high interstitial Biot number and porosity, while it is unfavorably affected by the high values of Prandtl number. However, it is also found that the parameters ranges corresponding to the local equilibrium validity depends on the selected local thermal non equilibrium criterion.





Boundary Layer Flow and Heat Transfer over a Permeable Stretching/Shrinking Sheet with a Convective Boundary Condition


Pages :
499505


Authors :
Khairy Zaimi,
Anuar Ishak,
This paper concerns with the boundary layer flow and heat transfer over a permeable stretching/shrinking sheet in
a viscous fluid, with the bottom surface of the plate is heated by convection from a hot fluid. The partial differential equations governing the flow and heat transfer are converted into ordinary differential equations using a similarity transformation, before being solved numerically. The effects of the suction, convection and stretching/shrinking parameters on the skin friction coefficient and the local Nusselt number are examined and graphically illustrated. Dual solutions are found to exist for a certain range of the suction and stretching/shrinking parameters. The numerical results also show that suction widens the range of the stretching/shrinking parameter for which the solution exists.





Magnetohydrodynamic Flow of LiquidMetal in Circular Pipes for Externally Heated and NonHeated Cases


Pages :
507514


Authors :
Atilla Altintas,
Ibrahim Ozkol,
The Computational Fluid Dynamics (CFD) study of external magnetic field effect on the steady, laminar, incompressible flow of an electrically conducting liquidmetal fluid in a pipe has been performed. The MHD Module of ANSYS Fluent commercial programme has been used to compute the flow and temperature fields. Na22K78 (sodium potassium) alloy has been used as operating fluid, which is liquid in room temperature. The simulations are performed for two different cases, first a nonheated pipe flow and secondly an externally heated pipe flow. For both cases, three different magnitude uniform external magnetic field, B0, applied (which are B0 = 0.5 T, 1.0 T and 1.25 T, T represents Tesla). The results are compared for the MHD effect on the flow variables in two cases separately, but also compared for heated and nonheated cases in order to analyze the temperature effect on MHD flows, as well. It is observed that heating is reducing the magnetic effect on the flow field. While in nonheated cases it is observed that very wellknown slowing down effect of MHD on fluid flow, in heated case the velocity field shows a tendency to behave as if it were MHD is not applied. Towards the end of the physical length the heating seems dominating the MHD effect. It is shown that in heated case temperature differences and entropy differences are in tendency to behave as if it were MHD is not applied.





Experimental Study of AirCooled Parallel Plate Fin Heat Sinks with and without Circular Pin Fins between the Plate Fins


Pages :
515520


Authors :
Sam Pouryoussefi,
Yuwen Zhang,
Experiments were conducted to investigate forced convective cooling performance of an air cooled parallel plate fin heat sink with and without circular pin fins between the plate fins. The original parallel plate heat sink was fabricated consist of 9 parallel plates of length 53 mm with crosssectional area of 1.4 mm in width by 20 mm height for each plate. The second heat sink has the same geometry of original one but with some circular pins between the plate fins. Thermal and hydrodynamics performances of the heat sinks have been assessed from the results obtained for the pressure drop, thermal resistance and overall performance with the free stream air velocity ranging from 4.7 to 12.5 m/s. Results show that the free stream air velocity has a significant effect on the thermal and hydrodynamics performance of the system. With increasing free stream velocity, the heat transfer coefficient increases and consequently the thermal resistance decreases while pressure drop increases due to higher inertial of fluid at higher velocities. Furthermore, at the same free stream air velocity the thermal resistance for the heat sink with circular pin is about 37.7% lower than that of the original heat sink.





Effect of Homogeneous and Heterogeneous Chemical Reactions on Peristaltic Transport of a Jeffrey Fluid through a Porous Medium with Slip Condition


Pages :
521528


Authors :
RAVI KIRAN GOOLLA,
Radhakrishnamacharya Ganjam,
In this paper, the dispersion of solute matter in a Jeffrey fluid flow through a porous medium in a peristaltic channel has been investigated under the influence of slip boundary conditions. Long wavelength approximation and Taylor's limiting condition are used to obtain the average effective dispersion coefficient in both the cases of homogeneous and heterogeneous chemical reactions. The effects of various pertinent parameters on the effective dispersion coefficient are discussed. Average effective dispersion coefficient increases with amplitude ratio. That is, more dispersion in the presence of peristalsis. Further, the average effective dispersion coefficient increases with the permeability parameter and the slip parameter; but decreases with the Jeffrey number, homogeneous / heterogeneous chemical reaction rate parameter.





Radiation and Mass Transfer Effects on MHD Oscillatory Flow in a Channel Filled with Porous Medium in the Presence of Chemical Reaction


Pages :
529537


Authors :
S. M. Ibrahim,
K. Gangadhar,
N. Bhaskar Reddy,
The interaction of radiation and mass transfer in an electrically conducting fluid through a channel filled with porous medium has received little attention. Hence, an attempt is made to investigate the combined effects of a transverse magnetic field and radiation on an unsteady mass transfer flow with chemical reaction through a channel filled with saturated porous medium and nonuniform wall temperature. The equations of continuity, linear momentum, energy and diffusion, which govern the flow field, are solved by using an analytical method. The behaviour of the velocity, temperature, concentration, skinfriction, Nusselt number and Sherwood number has been discussed for variations in the governing parameters.





Pressure Corrections for the Potential Flow Analysis of Electrohydrodynamic KelvinHelmholtz Instability


Pages :
539547


Authors :
M. K. Awasthi,
Mohammad Tamsir,
The present paper deals with the study of the pressure corrections to the viscous potential flow analysis of KelvinHelmholtz instability with tangential electric field at the interface of two viscous fluids. Viscosity enters through normal stress balance in the viscous potential flow theory and tangential stresses for two fluids are not continuous at the interface. Here we have considered viscous pressure in the normal stress balance along with the irrotational pressure and it is assumed that the addition of this viscous pressure will resolve the discontinuity between the tangential stresses and the tangential velocities at the interface of two fluids. The viscous pressure is derived by mechanical energy balance equation and this pressure correction applied to compute the growth rate of electrohydrodynamic KelvinHelmholtz instability. A dispersion relation is obtained and stability criterion is given in the terms of critical value of relative velocity. It has been observed that the inclusion of irrotational shearing stresses have stabilizing effect on the stability of the system.





Lie Group Analysis for Boundary Layer Flow of Nanofluids near the StagnationPoint over a Permeable Stretching Surface Embedded in a Porous Medium in the Presence of Radiation and Heat Generation/Absorption


Pages :
549558


Authors :
P. Sreenivasulu,
N. Bhaskar Reddy,
This study investigates the influence of thermal radiation and heat generation/absorption on a two dimensional steady boundary layer flow near the stagnationpoint on a permeable stretching sheet in a porous medium saturated with nanofluids. The governing partial differential equations with the appropriate boundary conditions are reduced to a set of ordinary differential equations via Liegroup analysis. The resultant equations are then solved numerically using Runge  Kutta fourth order method along with shooting technique. Two types of nanofluids, namely, copperwater and aluminawater are considered. The velocity and temperature as well as the shear stress and heat transfer rates are computed. The influence of pertinent parameters such as radiation parameter Nr, nanofluid volume fraction parameter , the ratio of free stream velocity and stretching velocity parameter a/c , the permeability parameter K1, suction/blowing parameter S, and heat source/sink parameter on the flow and heat transfer characteristics is discussed. The present study helps to understand the efficiency of heat transfer transport in nanofluids which are likely to be the smart
coolants of the next generation.





Radiation, Heat Generation and Viscous Dissipation Effects on MHD Boundary Layer Flow for the Blasius and Sakiadis Flows with a Convective Surface Boundary Condition


Pages :
559570


Authors :
K. Gangadhar,
N. Bhaskar Reddy,
S. Suneetha,
This study is devoted to investigate the radiation, heat generation viscous dissipation and magnetohydrodynamic effects on the laminar boundary layer about a flatplate in a uniform stream of fluid (Blasius flow), and about a moving plate in a quiescent ambient fluid (Sakiadis flow) both under a convective surface boundary condition. Using a similarity variable, the governing nonlinear partial differential equations have been transformed into a set of coupled nonlinear ordinary differential equations, which are solved numerically by using shooting technique alongside with the forth order of RungeKutta method and the variations of dimensionless surface temperature and fluidsolid interface characteristics for different values of Magnetic field parameter M, Grashof number Gr, Prandtl number Pr, radiation parameter NR, Heat generation parameter Q, Convective parameter and the Eckert number Ec, which characterizes our convection processes are graphed and tabulated. Quite different and interesting behaviors were encountered for Blasius flow compared with a Sakiadis flow. A comparison with previously published results on special cases of the problem shows excellent agreement.





MHD Boundary Layer Flow near Stagnation Point of Linear Stretching Sheet with Variable Thermal Conductivity via He’s Homotopy Perturbation Method


Pages :
571578


Authors :
JHANKAL ANUJ,
MHD boundary layer flow near stagnation point of linear stretching sheet with variable thermal conductivity are solved using He’s Homotopy Perturbation Method (HPM), which is one of the semiexact method. Similarity transformation has been used to reduce the governing differential equations into an ordinary nonlinear differential equation. The main advantage of HPM is that it does not require the small parameter in the equations and hence the limitations of traditional perturbations can be eliminated. In this paper firstly, the basic idea of the HPM for solving nonlinear differential equations is briefly introduced and then it is employed to derive solution of nonlinear governing equations of MHD boundary layer flow with nonlinear term. The influence of various relevant physical characteristics are presented and discussed.





Evaluation of Guiding Device for Downstream Fish Migration with inField Particle Tracking Velocimetry and CFD


Pages :
579589


Authors :
Staffan Lundstrom,
Mattias BR,
AnnaLena Ljung,
Gunnar Hellström,
Torbjörn Green,
The performance of a fish guiding device located just upstream a hydropower plant is scrutinized. The device is designed to redirect surface orientated downstream migrating fish (smolts) away from the turbines towards a spillway that act as a relatively safe fishway. Particles are added upstream the device and the fraction particles going to the spillway is measured. A twoframe Particle Tracking Velocimetry algorithm is used to derive the velocity field of the water. The experimental results are compared to simulations with CFD. If the smolts move passively as the particles used in the study the guiding device works very well and some modifications may optimize its performance. Infield Particle Tracking Velocimetry is a suitable technique for the current case and the results compare well with numerical simulations.





Ferromagnetic Liquid Flow due to GravityAligned Stretching of an Elastic Sheet


Pages :
591600


Authors :
L.S.Rani Titus,
Annamma Abraham,
The flow of a ferromagnetic liquid due to gravityaligned stretching of an elastic sheet in the presence of a magnetic dipole is considered. The fluid momentum and thermal energy equations are formulated as a six parameter problem and a numerical study is made using the shooting method based on Runge – Kutta Fehlberg and Newton Raphson methods. Extensive computation on the velocity and temperature profiles is presented for a wide range of values of the parameters. It was found that the primary effect of the magnetothermomechanical interaction is to decelerate the fluid motion as compared to the hydrodynamic case. The results have possible industrial applications in ferromagnetic liquid based systems involving stretchable materials.





Aerodynamic Optimization of the Nose Shape of a Train Using the Adjoint Method


Pages :
601612


Authors :
Jorge MunozPaniagua,
Javier Garcia,
Antonio Crespo,
Fabien Laspougeas,
The adjoint method is used in this paper for the aerodynamic optimization of the nose shape of a train. This method has been extensively applied in aircraft or ground vehicle aerodynamic optimization, but is still in progress in train aerodynamics. Here we consider this innovative optimization method and present its application to reduce the aerodynamic drag when the train is subjected to front wind. The objective of this paper is to demonstrate the effectiveness of the method, highlighting the requirements, limitations and capabilities of it. Furthermore, a significant reduction of the aerodynamic drag in a short number of solver calls is aimed as well. The independence of the computational cost with respect to the number of design variables that define the optimal candidate is stressed as the most interesting characteristic of the adjoint method. This behavior permits a more complete modification of the shape of the train nose because the number of design variables is not a constraint anymore. The information obtained from the sensitivity field permits determining the regions of the geometry where a small modification of the nose shape might introduce a larger improvement of the train performance. A good agreement between this information and the successive geometry modifications is observed here.





Nonlinear Radiation Effects on Hydromagnetic Boundary Layer Flow and Heat Transfer over a Shrinking Surface


Pages :
613621


Authors :
S. P. Anjali Devi,
J. Wilfred Samuel Raj,
The effects of nonlinear radiation on hydromagnetic boundary layer flow and heat transfer over a shrinking surface is investigated in the present work. Using suitable similarity transformations, the governing nonlinear partial differential equations are transformed into nonlinear ordinary differential equations. The resultant equations which are highly nonlinear are solved numerically using Nachtsheim Swigert shooting iteration scheme together with Fourth Order Runge Kutta method. Numerical solutions for velocity, skin friction coefficient and temperature are obtained for various values of physical parameters involved in the study namely Suction parameter, Magnetic parameter, Prandtl number, Radiation parameter and Temperature ratio parameter. Numerical values for dimensionless rate of heat transfer are also obtained for various physical parameters and are shown through tables. The analytical solution of the energy equation when the radiation term is taken in linear form is obtained using Confluent hypergeometric function.





Unsteady Hydromagnetic Natural Convection Flow past an Impulsively Moving Vertical Plate with Newtonian Heating in a Rotating System


Pages :
623633


Authors :
Gauri Seth,
Subharthi Sarkar,
Raj Nandkeolyar,
An investigation of unsteady hydromagnetic natural convection flow of a viscous, incompressible, electrically conducting and heat absorbing fluid past an impulsively moving vertical plate with Newtonian heating embedded in a porous medium in a rotating system is carried out. The governing partial differential equations are first subjected to Laplace transformation and then inverted numerically using INVLAP routine of Matlab. The governing partial differential equations are also solved numerically by CrankNicolson implicit finite difference scheme and a comparison has been provided between the two solutions. The numerical solution for fluid velocity and fluid temperature are depicted graphically whereas the numerical values of skin friction and Nusselt number are presented in tabular form for various values of pertinent flow parameters. Present solution in special case is compared with previously obtained solution and is found to be in excellent agreement.





A Study on Steady Natural Convective Heat Transfer Inside A Square Cavity For Different Values of Rayleigh and Nusselt Numbers


Pages :
635640


Authors :
Paritosh Bhattacharya,
The aim of the present numerical study is to understand the steady natural convection flow and heat transfer in a Square
cavity with heated left wall. The top and bottom walls of the cavity are kept to be adiabatic. The finite volume approach for
the range of Rayleigh Number as 10... ≤ ... ≤ 10... and Pr=0.71 is used to solve the governing equations, in which
buoyancy is modeled via the Boussinesq approximation in FLUENT. The computed flow patterns and temperature fields are
shown by means of streamlines and isotherms, respectively. The influence of Rayleigh numbers on the hot wall of the cavity
are analyzed. Change in Velocity with different Rayleigh Number near the top wall of the enclosure are investigated here.
Variations of the maximum value of the dimensionless stream function and Nusselt Number were also presented. The
computed result indicated that Nusselt number increases along the length of the hot wall and decreases near the end of the
wall.



