Journal of Fluids
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The latest articles from Hindawi Publishing Corporation
© 2016 , Hindawi Publishing Corporation . All rights reserved.

A Volumetric Approach to Wake Reduction: Design, Optimization, and Experimental Verification
Thu, 05 May 2016 08:40:06 +0000
http://www.hindawi.com/journals/fluids/2016/3587974/
Wake reduction is a crucial link in the chain leading to undetectable watercraft. Here, we explore a volumetric approach to controlling the wake in a stationary flow past cylindrical and spherical objects. In this approach, these objects are coupled with rigid, fluidpermeable structures prescribed by a macroscopic design approach where all solid boundaries are parameterized and modeled explicitly. Local, gradientbased optimization is employed which permits topological changes in the manifold describing the composite solid component(s) while still allowing the use of adjoint optimization methods. This formalism works below small Reynolds number (Re) turbulent flow (–10,000) when simulated using small Reynoldsaveraged NavierStokes (RANS) models. The output of this topology optimization yields geometries that can be fabricated immediately using fused deposition modeling (FDM). Our prototypes have been verified in an experimental water tunnel facility, where the use of Particle Image Velocimetry (PIV) described the velocity profile. Comparisons with our computational models show excellent agreement for the spherical shapes and reasonable match for cylindrical shapes, with wellunderstood sources of error. Two important figures of merit are considered: domainwide wake (DWW) and maximum local wake (MLW), metrics of the flow field disturbance whose definitions are described.
Dean R. Culver, Earl Dowell, David Smith, Yaroslav Urzhumov, and Abraham Varghese
Copyright © 2016 Dean R. Culver et al. All rights reserved.

Rheological Behavior of Physiological Pulsatile Flow through a Model Arterial Stenosis with Moving Wall
Wed, 10 Jun 2015 12:17:41 +0000
http://www.hindawi.com/journals/fluids/2015/546716/
The paper presents a numerical investigation of nonNewtonian modeling effects on unsteady periodic flows in a twodimensional (2D) constricted channel with moving wall using finite volume method. The governing NavierStokes equations have been modified using the Cartesian curvilinear coordinates to handle complex geometries, such as, arterial stenosis. The physiological pulsatile flow has been used at the inlet position as an inlet velocity. The flow is characterized by the Reynolds numbers 300, 500, and 750 that are appropriate for large arteries. The investigations have been carried out to characterize four different nonNewtonian constitutive equations of blood, namely, the (i) Carreau, (ii) Cross, (iii) ModifiedCasson, and (iv) Quemada. In these four models, blood viscosity is a nonlinear function of shear rates. The Newtonian model has been investigated to study the physics of fluid and the results are compared with the nonNewtonian viscosity models. The numerical results are presented in terms of streamwise velocity, wall shear stress, pressure distribution as well as the vorticity, streamlines, and vector plots indicating recirculation zones at the poststenotic region. Comparison has also been illustrated in terms of wall pressure and wall shear stress for the Cross model considering different amplitudes of wall oscillation.
Sumaia Parveen Shupti, Mir Golam Rabby, and Md. Mamun Molla
Copyright © 2015 Sumaia Parveen Shupti et al. All rights reserved.

Separation Criteria for OffAxis Binary Drop Collisions
Mon, 25 May 2015 06:08:33 +0000
http://www.hindawi.com/journals/fluids/2015/405696/
Offaxis collisions of two equal size droplets are investigated numerically. Various governing processes in such collisions are discussed. Several commonly used theoretical models that predict the onset of separation after collision are evaluated based on the processes observed numerically. A separation criterion based on droplet deformation is found. The numerical results are used to assess the validity of some commonly used phenomenological models for drop separation after collision. Also, a critical Weber number for the droplet separation after grazing collision is reported. The effect of Reynolds number is investigated and regions of permanent coalescence and separation are plotted in a WeberReynolds number plane for high impact parameter collisions.
Mary D. Saroka and Nasser Ashgriz
Copyright © 2015 Mary D. Saroka and Nasser Ashgriz. All rights reserved.

Unsteady/Steady Hydromagnetic Convective Flow between Two Vertical Walls in the Presence of Variable Thermal Conductivity
Wed, 20 May 2015 06:24:46 +0000
http://www.hindawi.com/journals/fluids/2015/358053/
Unsteady as well as steady natural convection flow in a vertical channel in the presence of uniform magnetic field applied normal to the flow region and temperature dependent variable thermal conductivity is studied. The nonlinear partial differential equations governing the flow have been solved numerically using unconditionally stable and convergent semiimplicit finite difference scheme. For steady case, approximate solutions have been derived for velocity, temperature, skin friction, and the rate of heat transfer using perturbation series method. Results of the computations for velocity, temperature, skin friction, and the rate of heat transfer are presented graphically and discussed quantitatively for various parameters embedded in the problem. An excellent agreement was found during the numerical computations between the steadystate approximate solutions and unsteady numerical solutions at steadystate time. In addition, comparison with previously published work is performed and the results agree well.
M. M. Hamza, I. G. Usman, and A. Sule
Copyright © 2015 M. M. Hamza et al. All rights reserved.

Effects of Heat and Mass Transfer on the Peristaltic Transport of MHD Couple Stress Fluid through Porous Medium in a Vertical Asymmetric Channel
Mon, 09 Mar 2015 06:43:51 +0000
http://www.hindawi.com/journals/fluids/2015/163832/
The intrauterine fluid flow due to myometrial contractions is peristaltic type motion and the myometrial
contractions may occur in both symmetric and asymmetric directions. The channel asymmetry is produced by choosing the peristaltic wave train on the walls to have different amplitude, and phase due to the variation of channel width, wave amplitudes and phase differences. In this paper, we study the effects of heat and mass transfer on the peristaltic transport of magnetohydrodynamic couple stress fluid through homogeneous porous medium in a vertical asymmetric channel. The flow is investigated in the wave frame of reference moving with constant velocity with the wave. The governing equations of couple stress fluid have been simplified under the long wave length approximation. The exact solutions of the resultant governing equations have been derived for the stream function, temperature, concentration, pressure gradient, and heat transfer coefficients. The pressure difference and frictional forces at both the walls are calculated using numerical integration. The influence of diverse flow parameters on the fluid velocity, pressure gradient, temperature, concentration, pressure difference, frictional forces, heat transfer coefficients, and trapping has been discussed. The graphical results are also discussed for four different wave shapes. It is noticed that increasing of couple
stresses and heat generation parameter increases the size of the trapped bolus. The heat generation parameter increases the peristaltic pumping and temperature.
K. Ramesh and M. Devakar
Copyright © 2015 K. Ramesh and M. Devakar. All rights reserved.

Phase Separation Behavior and System Properties of Aqueous TwoPhase Systems with Polyethylene Glycol and Different Salts: Experiment and Correlation
Tue, 24 Feb 2015 16:31:35 +0000
http://www.hindawi.com/journals/fluids/2015/682476/
The phase separation behaviors of PEG1000/sodium citrate, PEG4000/sodium citrate, PEG1000/ammonium sulfate, and PEG4000/ammonium sulfate aqueous twophase systems were investigated, respectively. There are two distinct situations for the phase separation rate in the investigated aqueous twophase systems: one state is topcontinuous phase with slow phase separation rate and strong bottomcontinuous phase with fast phase separation rate and weak volume ratio dependence. The system properties such as density, viscosity, and interfacial tension between top and bottom phases which have effects on the phase separation rate of aqueous twophase systems were measured. The property parameter differences between the two phases increased with increasing tie line length and then improved the phase separation rate. Moreover, a modified correlation equation including the phase separation rate, tie line length, and physical properties of the four aqueous twophase systems has been proposed and successfully tested in the bottomcontinuous phase, whose coefficients were estimated through regression analysis. The predicted results of PEG1000/sodium citrate aqueous twophase systems were verified through the stationary phase retention in the crossaxis countercurrent chromatography.
Haihua Yuan, Yang Liu, Wanqian Wei, and Yongjie Zhao
Copyright © 2015 Haihua Yuan et al. All rights reserved.

Magnetohydrodynamic Mixed Convection StagnationPoint Flow of a PowerLaw NonNewtonian Nanofluid towards a Stretching Surface with Radiation and Heat Source/Sink
Thu, 19 Feb 2015 12:08:56 +0000
http://www.hindawi.com/journals/fluids/2015/634186/
Twodimensional MHD mixed convection boundary layer flow of heat and mass transfer stagnationpoint flow of a nonNewtonian powerlaw nanofluid towards a stretching surface in the presence of thermal radiation and heat source/sink is investigated numerically. The nonNewtonian nanofluid model incorporates the effects of Brownian motion and thermophoresis. The basic transport equations are made dimensionless first and the complete nonlinear differential equations with associated boundary conditions are solved numerically by finite element method (FEM). The numerical calculations for velocity, temperature, and nanoparticles volume fraction profiles for different values of the physical parameters to display the interesting aspects of the solutions are presented graphically and discussed. The skin friction coefficient, the local Nusslet number and the Sherwood number are exhibited and examined. Our results are compatible with the existing results for a special case.
Macha Madhu and Naikoti Kishan
Copyright © 2015 Macha Madhu and Naikoti Kishan. All rights reserved.

Analysis of Heat and Mass Transfer on MHD Peristaltic Flow through a Tapered Asymmetric Channel
Mon, 26 Jan 2015 12:58:47 +0000
http://www.hindawi.com/journals/fluids/2015/561263/
This paper describes the peristaltic flow of an incompressible viscous fluid in a tapered asymmetric channel with heat and mass transfer. The fluid is electrically conducting fluid in the presence of a uniform magnetic field. The propagation of waves on the nonuniform channel walls to have different amplitudes and phase but with the same speed is generated the tapered asymmetric channel. The assumptions of low Reynolds number and long wavelength approximations have been used to simplify the complicated problem into a relatively simple problem. Analytical expressions for velocity, temperature, and concentration have been obtained. Graphically results of the flow characteristics are also sketched for various embedded parameters of interest entering the problem and interpreted.
M. Kothandapani, J. Prakash, and V. Pushparaj
Copyright © 2015 M. Kothandapani et al. All rights reserved.

Suction/Injection Effects on the Swirling Flow of a ReinerRivlin Fluid near a Rough Surface
Mon, 05 Jan 2015 10:11:28 +0000
http://www.hindawi.com/journals/fluids/2015/253504/
The similarity equations for the Bödewadt flow of a nonNewtonian ReinerRivlin fluid, subject to uniform suction/injection, are solved numerically. The conventional noslip boundary conditions are replaced by corresponding partial slip boundary conditions, owing to the roughness of the infinite stationary disk. The combined effects of surface slip (), suction/injection velocity (), and crossviscous parameter () on the momentum boundary layer are studied in detail. It is interesting to find that suction dominates the oscillations in the velocity profiles and decreases the boundary layer thickness significantly. On the other hand, injection has opposite effects on the velocity profiles and the boundary layer thickness.
Bikash Sahoo, Sébastien Poncet, and Fotini Labropulu
Copyright © 2015 Bikash Sahoo et al. All rights reserved.

Numerical Characterization of the Performance of Fluid Pumps Based on a Wankel Geometry
Tue, 30 Sep 2014 00:00:00 +0000
http://www.hindawi.com/journals/fluids/2014/241010/
The performance of fluid pumps based on Wankeltype geometry, taking the shape of a doublelobed limaçon, is characterized. To the authors’ knowledge, this is the first time such an attempt has been made. To this end, numerous simulations for three different pump sizes were carried out and the results were understood in terms of the usual scaling coefficients. The results show that such pumps operate as low efficiency (<30%) valveless positive displacements pumps, with pump flowrate noticeably falling at the onset of internal leakage. Also, for such pumps, the mechanical efficiency varies linearly with the head coefficient, and, within the onset of internal leakage, the capacity coefficient holds steady even across pump efficiency. Simulation of the flow field reveals a structure rich in threedimensional vortices even in the laminar regime, including Taylorlike counterrotating vortex pairs, pointing towards the utility of these pumps in microfluidic applications. Given the planar geometry of such pumps, their applications as microreactors and micromixers are recommended.
Stephen Wan, Jason Leong, Te Ba, Arthur Lim, and Chang Wei Kang
Copyright © 2014 Stephen Wan et al. All rights reserved.

Modeling the Uniformity of Manifold with Various Configurations
Sun, 24 Aug 2014 07:21:52 +0000
http://www.hindawi.com/journals/fluids/2014/325259/
The flow distribution in manifolds is highly dependent on inlet pressure, configuration, and total inlet flow to the manifold. The flow from a manifold has many applications and in various fields of engineering such as civil, mechanical, and chemical engineering. In this study, physical and numerical models were employed to study the uniformity of the flow distribution from manifold with various configurations. The physical model consists of main manifold with uniform longitudinal section having diameter of 10.16 cm (4 in), five laterals with diameter of 5.08 cm (2 in), and spacing of 22 cm. Different inlet flows were tested and the values of these flows are 500, 750, and 1000 L/min. A manifold with tapered longitudinal section having inlet diameters of 10.16 cm (4 in) and dead end diameter of 5.08 cm (2 in) with the same above later specifications and flow rates was tested for its uniformity too. The percentage of absolute mean deviation for manifold with uniform diameter was found to be 34% while its value for the manifold with nonuniform diameter was found to be 14%. This result confirms the efficiency of the nonuniform distribution of fluids.
Jafar M. Hassan, Thamer A. Mohamed, Wahid S. Mohammed, and Wissam H. Alawee
Copyright © 2014 Jafar M. Hassan et al. All rights reserved.

Double Diffusive Convection in a Layer of Maxwell Viscoelastic Fluid in Porous Medium in the Presence of Soret and Dufour Effects
Thu, 17 Jul 2014 11:05:52 +0000
http://www.hindawi.com/journals/fluids/2014/479107/
Double diffusive convection in a horizontal layer of Maxwell viscoelastic fluid in a porous medium in the presence of temperature gradient (Soret effects) and concentration gradient (Dufour effects) is investigated. For the porous medium Darcy model is considered. A linear stability analysis based upon normal mode technique is used to study the onset of instabilities of the Maxwell viscolastic fluid layer confined between two freefree boundaries. Rayleigh number on the onset of stationary and oscillatory convection has been derived and graphs have been plotted to study the effects of the Dufour parameter, Soret parameter, Lewis number, and solutal Rayleigh number on stationary convection.
Ramesh Chand and G. C. Rana
Copyright © 2014 Ramesh Chand and G. C. Rana. All rights reserved.

Numerical Simulation of Water Jet Flow Using Diffusion Flux Mixture Model
Wed, 16 Jul 2014 07:34:04 +0000
http://www.hindawi.com/journals/fluids/2014/193215/
A multidimensional diffusion flux mixture model was developed to simulate water jet twophase flows. Through the modification of the gravity using the gradients of the mixture velocity, the centrifugal force on the water droplets was able to be considered. The slip velocities between the continuous phase (gas) and the dispersed phase (water droplets) were able to be calculated through multidimensional diffusion flux velocities based on the modified multidimensional drift flux model. Through the numerical simulations, comparing with the experiments and the simulations of traditional algebraic slip mixture model on the water mist spray, the model was validated.
Zhi Shang, Jing Lou, and Hongying Li
Copyright © 2014 Zhi Shang et al. All rights reserved.

Pulsatile NonNewtonian Laminar Blood Flows through Arterial Double Stenoses
Thu, 29 May 2014 13:26:10 +0000
http://www.hindawi.com/journals/fluids/2014/757902/
The paper presents a numerical investigation of nonNewtonian modeling effects on unsteady periodic flows in a twodimensional (2D) pipe with two idealized stenoses of 75% and 50% degrees, respectively. The governing NavierStokes equations have been modified using the Cartesian curvilinear coordinates to handle complex geometries. The investigation has been carried out to characterize four different nonNewtonian constitutive equations of blood, namely, the (i) Carreau, (ii) Cross, (iii) Modified Casson, and (iv) Quemada models. The Newtonian model has also been analyzed to study the physics of fluid and the results are compared with the nonNewtonian viscosity models. The numerical results are represented in terms of streamwise velocity, pressure distribution, and wall shear stress (WSS) as well as the vorticity, streamlines, and vector plots indicating recirculation zones at the poststenotic region. The results of this study demonstrate a lower risk of thrombogenesis at the downstream of stenoses and inadequate blood supply to different organs of human body in the Newtonian model compared to the nonNewtonian ones.
Mir Golam Rabby, Sumaia Parveen Shupti, and Md. Mamun Molla
Copyright © 2014 Mir Golam Rabby et al. All rights reserved.

Viscous Flows Driven by Uniform Shear over a Porous Stretching Sheet in the Presence of Suction/Blowing
Sun, 25 May 2014 12:33:49 +0000
http://www.hindawi.com/journals/fluids/2014/206846/
An analysis is carried out to study the steady twodimensional flow of an incompressible viscous fluid past a porous deformable sheet, which is stretched in its own plane with a velocity proportional to the distance from the fixed point subject to uniform suction or blowing. A uniform shear flow of strain rate β is considered over the stretching sheet. The analysis of the result obtained shows that the magnitude of the wall shear stress increases with the increase of suction velocity and decreases with the increase of blowing velocity and this effect is more pronounced for suction than blowing. It is seen that the horizontal velocity component (at a fixed streamwise position along the plate) increases with the increase in the ratio of shear rate β and stretching rate (c) (i.e., β/c) and there is an indication of flow reversal. It is also observed that this flow reversal region increases with the increase in β/c.
Samir Kumar Nandy and Swati Mukhopadhyay
Copyright © 2014 Samir Kumar Nandy and Swati Mukhopadhyay. All rights reserved.

Linear Stability Analysis of Thermal Convection in an Infinitely Long Vertical Rectangular Enclosure in the Presence of a Uniform Horizontal Magnetic Field
Tue, 29 Apr 2014 08:12:16 +0000
http://www.hindawi.com/journals/fluids/2014/642042/
Stability of thermal convection in an infinitely long vertical channel in the presence of a uniform horizontal magnetic field applied in the direction parallel to the hot and cold walls was numerically studied. First, in order to confirm accuracy of the present numerical code, the onedimensional computations without the effect of magnetic field were computed and they agreed with a previous study quantitatively for various values of the Prandtl number. Then, linear stability analysis for the thermal convection flow in a square horizontal cross section under the magnetic field was carried out for the case of Pr = 0.025. The thermal convection flow was once destabilized at certain low Hartmann numbers, and it was stabilized at high Hartmann numbers.
Takashi Kitaura and Toshio Tagawa
Copyright © 2014 Takashi Kitaura and Toshio Tagawa. All rights reserved.

Peristaltic Motion of NonNewtonian Fluid with Heat and Mass Transfer through a Porous Medium in Channel under Uniform Magnetic Field
Thu, 10 Apr 2014 09:10:57 +0000
http://www.hindawi.com/journals/fluids/2014/525769/
This paper is devoted to the study of the peristaltic motion of nonNewtonian fluid with heat and mass transfer through a porous medium in the channel under the effect of magnetic field. A modified Casson nonNewtonian constitutive model is employed for the transport fluid. A perturbation series’ method of solution of the stream function is discussed. The effects of various parameters of interest such as the magnetic parameter, Casson parameter, and permeability parameter on the velocity, pressure rise, temperature, and concentration are discussed and illustrated graphically through a set of figures.
Nabil T. M. Eldabe, Bothaina M. Agoor, and Heba Alame
Copyright © 2014 Nabil T. M. Eldabe et al. All rights reserved.

Enhancement of Impinging Jet Heat Transfer Using Two Parallel Confining Plates Mounted near Rectangular Nozzle Exit
Tue, 25 Mar 2014 12:47:11 +0000
http://www.hindawi.com/journals/fluids/2014/873684/
Impinging jet heat transfer on a target plate was enhanced by using two parallel confining
plates mounted between a rectangular nozzle end plate and a jet target plate. The target
plate was set equal to 2, 3, 4, and 5 times the jet exit width, , and the gap ratio of two parallel confining plates, , were changed from 2.7 to 8.0 only by impinging length and from 2.7 to 6.7 by . Two confining parallel plates mounted near the jet exit produced
swingtype flow under some conditions. As a result, the maximum Nusselt number
attained around the stagnation point was augmented by about 50% compared to the one
for normal impinging jet without the two parallel plates and then spatial mean Nusselt
number was increased by about 40%.
Yoshiaki Haneda, Akiko Souma, Hideo Kurasawa, Shouichiro Iio, and Toshihiko Ikeda
Copyright © 2014 Yoshiaki Haneda et al. All rights reserved.

DoubleDiffusive Convection in Presence of Compressible RivlinEricksen Fluid with Fine Dust
Tue, 04 Feb 2014 13:30:07 +0000
http://www.hindawi.com/journals/fluids/2014/714150/
An investigation is made on the effect of suspended particles (fine dust) on doublediffusive convection of a compressible RivlinEricksen elasticoviscous fluid. The perturbation equations are analyzed in terms of normal modes after linearizing the relevant set of equations. A dispersion relation governing the effects of viscoelasticity, compressibility, stable solute gradient, and suspended particles is derived. For stationary convection, RivlinEricksen fluid behaves like an ordinary Newtonian fluid due to the vanishing of the viscoelastic parameter. The stable solute gradient compressibility has a stabilizing effect on the system whereas suspended particles hasten the onset of thermosolutal instability. The Rayleigh numbers and the wave numbers of the associated disturbances for the onset of instability as stationary convection are obtained and the behaviour of various parameters on Rayleigh numbers has been depicted graphically. It has been observed that oscillatory modes are introduced due to the presence of viscoelasticity, suspended particles, and stable solute gradient which were not existing in the absence of these parameters.
Mahinder Singh and Rajesh Kumar Gupta
Copyright © 2014 Mahinder Singh and Rajesh Kumar Gupta. All rights reserved.

Hydraulic Analysis of Water Distribution Network Using Shuffled Complex Evolution
Thu, 16 Jan 2014 11:16:28 +0000
http://www.hindawi.com/journals/fluids/2014/979706/
Hydraulic analysis of water distribution networks is an important problem in civil engineering. A widely used approach in steadystate analysis of water distribution networks is the global gradient algorithm (GGA). However, when the GGA is applied to solve these networks, zero flows cause a computation failure. On the other hand, there are different mathematical formulations for hydraulic analysis under pressuredriven demand and leakage simulation. This paper introduces an optimization model for the hydraulic analysis of water distribution networks using a metaheuristic method called shuffled complex evolution (SCE) algorithm. In this method, applying ifthen rules in the optimization model is a simple way in handling pressuredriven demand and leakage simulation, and there is no need for an initial solution vector which must be chosen carefully in many other procedures if numerical convergence is to be achieved. The overall results indicate that the proposed method has the capability of handling various pipe networks problems without changing in model or mathematical formulation. Application of SCE in optimization model can lead to accurate solutions in pipes with zero flows. Finally, it can be concluded that the proposed method is a suitable alternative optimizer challenging other methods especially in terms of accuracy.
Naser Moosavian and Mohammad Reza Jaefarzadeh
Copyright © 2014 Naser Moosavian and Mohammad Reza Jaefarzadeh. All rights reserved.

Free Convection Heat and Mass Transfer MHD Flow in a Vertical Porous Channel in the Presence of Chemical Reaction
Thu, 12 Dec 2013 08:34:07 +0000
http://www.hindawi.com/journals/fluids/2013/297493/
The objective of the present study is to examine the fully developed free convective MHD flow of an electrically conducting viscous incompressible fluid in a vertical porous channel under influence of asymmetric wall temperature and concentration in the presence of chemical reaction. The heat and mass transfer coupled with diffusionthermo effect renders the present analysis interesting and curious. The analytical solution by Laplace transform technique of partial differential equations is used to obtain the expressions for the velocity, temperature, and concentration. It is observed that under the influence of dominating mass diffusivity over thermal diffusivity with stronger Lorentz force the velocity is reduced at all points Further, low rate of thermal diffusion delays the attainment of free stream state. Flow of aqueous solution in the presence of heavier species is prone to back flow.
R. N. Barik, G. C. Dash, and M. Kar
Copyright © 2013 R. N. Barik et al. All rights reserved.

On the Stability of a Compressible Axial Flow with an Axial Magnetic Field
Tue, 10 Dec 2013 08:09:18 +0000
http://www.hindawi.com/journals/fluids/2013/869324/
We consider the stability problem of inviscid compressible axial flows with axial magnetic fields following the work of Dandapat and Gupta (Quarterly of Applied Mathematics, 1975). A numerical study of the stability of some basic flows has been carried out and it is found that an increase in the magnetic field strength has a stabilizing effect on subsonic flows and a
destabilizing effect on supersonic flows. An analytical study of the stability problem has also been done in the present paper, but this analytical study is restricted by the approximation and , where is the Mach number and is the imaginary part of the complex phase velocity . A semicircular region depending on the magnetic field parameter and the Mach number is found for subsonic disturbances and as a consequence it is found that sufficiently strong magnetic field stabilizes all subsonic disturbances. Under a weak magnetic field, it is shown that short subsonic disturbances are stable.
M. Subbiah and M. S. Anil Iype
Copyright © 2013 M. Subbiah and M. S. Anil Iype. All rights reserved.

Thermal Jump Effects on Boundary Layer Flow of a Jeffrey Fluid Near the Stagnation Point on a Stretching/Shrinking Sheet with Variable Thermal Conductivity
Thu, 05 Dec 2013 18:49:48 +0000
http://www.hindawi.com/journals/fluids/2013/749271/
A mathematical model will be analyzed in order to study the effects of thermal jump and variable thermal conductivity on flow and heat transfer near the stagnation point on a stretching/shrinking sheet in a Jeffrey fluid. The highly nonlinear partial differential equation of Jeffrey fluid flow along with the energy equation are transformed to an ordinary system using nondimensional transformations. The arising equations are solved for temperature, velocity, shear stress, and heat flux using finite difference method. The effect of the influences parameters is discussed. For nonradiation regular viscous fluid our results are as that by Nazar et al. (2002).
M. A. A. Hamad, S. M. AbdElGaied, and W. A. Khan
Copyright © 2013 M. A. A. Hamad et al. All rights reserved.

Free Convective MHD Flow Past a Vertical Cone with Variable Heat and Mass Flux
Mon, 18 Nov 2013 13:56:45 +0000
http://www.hindawi.com/journals/fluids/2013/405985/
A numerical study of buoyancydriven unsteady natural convection boundary layer flow past a vertical cone embedded in a nonDarcian isotropic porous regime with transverse magnetic field applied normal to the surface is considered. The heat and mass flux at the surface of the cone is modeled as a power law according to and , respectively, where denotes the coordinate along the slant face of the cone. Both Darcian drag and Forchheimer quadratic porous impedance are incorporated into the twodimensional viscous flow model. The transient boundary layer equations are then nondimensionalized and solved by the CrankNicolson implicit difference method. The velocity, temperature, and concentration fields have been studied for the effect of Grashof number, Darcy number, Forchheimer number, Prandtl number, surface heat flux powerlaw exponent (), surface mass flux powerlaw exponent (), Schmidt number, buoyancy ratio parameter, and semivertical angle of the cone. Present results for selected variables for the purely fluid regime are compared with the published results and are found to be in excellent agreement. The local skin friction, Nusselt number, and Sherwood number are also analyzed graphically. The study finds important applications in geophysical heat transfer, industrial manufacturing processes, and hybrid solar energy systems.
J. Prakash, S. Gouse Mohiddin, and S. Vijaya Kumar Varma
Copyright © 2013 J. Prakash et al. All rights reserved.

CFD Analysis of Energy Separation in RanqueHilsch Vortex Tube at Cryogenic Temperature
Thu, 14 Nov 2013 09:19:56 +0000
http://www.hindawi.com/journals/fluids/2013/562027/
Study of the energy separation phenomenon in vortex tube (VT) at cryogenic temperature (temperature range below 123 K) has become important because of the potential application of VT as inflight air separator in air breathing propulsion. In the present study, a CFD model is used to simulate the energy separation phenomenon in VT with gaseous air at cryogenic temperature as working fluid. Energy separation at cryogenic temperature is found to be considerably less than that obtained at normal atmospheric temperature due to lower values of inlet enthalpy and velocity. Transfer of tangential shear work from inner to outer fluid layers is found to be the cause of energy separation. A parametric sensitivity analysis is carried out in order to optimize the energy separation at cryogenic temperature. Also, rates of energy transfer in the form of sensible heat and shear work in radial and axial directions are calculated to investigate the possible explanation of the variation of the hot and cold outlet temperatures with respect to various geometric and physical input parameters.
T. Dutta, K. P. Sinhamahapatra, and S. S. Bandyopadhyay
Copyright © 2013 T. Dutta et al. All rights reserved.

SlipFlow and Heat Transfer in a Porous Microchannel Saturated with PowerLaw Fluid
Thu, 14 Nov 2013 08:16:00 +0000
http://www.hindawi.com/journals/fluids/2013/604893/
This study aims to numerically examine the fluid flow and heat transfer in a porous microchannel saturated with powerlaw fluid. The governing momentum and energy equations are solved by using the finite difference technique. The present study focuses on the slip flow regime, and the flow in porous media is modeled using the modified DarcyBrinkmanForchheimer model for powerlaw fluids. Parametric studies are conducted to examine the effects of Knudsen number, Darcy number, power law index, and inertia parameter. Results are given in terms of skin friction and Nusselt number. It is found that when the Knudsen number and the power law index decrease, the skin friction on the walls decreases. This effect is reduced slowly while the Darcy number decreases until it reaches the Darcy regime. Consequently, with a very low permeability the effect of power law index vanishes. The numerical results indicated also that when the power law index decreases the fullydeveloped Nusselt number increases considerably especially, in the limit of high permeability, that is, nonDarcy regime. As far as Darcy regime is concerned the effects of the Knudsen number and the power law index of the fullydeveloped Nusselt number is very little.
Yazan Taamneh and Reyad Omari
Copyright © 2013 Yazan Taamneh and Reyad Omari. All rights reserved.

A Double Diffusive Unsteady MHD Convective Flow Past a Flat Porous Plate Moving through a Binary Mixture with Suction or Injection
Sat, 26 Oct 2013 12:59:13 +0000
http://www.hindawi.com/journals/fluids/2013/935156/
The problem of unsteady magnetohydrodynamic convective flow with radiation and chemical reaction past a flat porous plate moving through a binary mixture in an optically thin environment is considered. The governing boundary layer equations are converted to nonlinear ordinary differential equations by similarity transformation and then solved numerically by MATLAB “bvp4c” routine. The velocity, temperature, and concentration profiles are presented graphically for various values of the material parameters. Also a numerical data for the local skin friction coefficient, the local Nusselt number, and local Sherwood number is presented in tabular forms.
D. R. V. S. R. K. Sastry and A. S. N. Murti
Copyright © 2013 D. R. V. S. R. K. Sastry and A. S. N. Murti. All rights reserved.

An Exact Analytical Solution of the Strong Shock Wave Problem in Nonideal Magnetogasdynamics
Mon, 21 Oct 2013 10:55:08 +0000
http://www.hindawi.com/journals/fluids/2013/810206/
We construct the solutions to the strong shock wave problem with generalized geometries in nonideal magnetogasdynamics. Here, it is assumed that the density ahead of the shock front varies according to a power of distance from the source of the disturbance. Also, an analytical expression for the total energy carried by the wave motion in nonideal medium under the influence of magnetic field is derived.
S. D. Ram, R. Singh, and L. P. Singh
Copyright © 2013 S. D. Ram et al. All rights reserved.

Hall Effect on Bénard Convection of Compressible Viscoelastic Fluid through Porous Medium
Thu, 10 Oct 2013 15:55:54 +0000
http://www.hindawi.com/journals/fluids/2013/910531/
An investigation made on the effect of Hall currents on thermal instability of a compressible Walter’s B′ elasticoviscous fluid through porous medium is considered. The analysis is carried out within the framework of linear stability theory and normal mode technique. For the case of stationary convection, Hall currents and compressibility have postponed the onset of convection through porous medium. Moreover, medium permeability hasten postpone the onset of convection, and magnetic field has duel character on the onset of convection. The critical Rayleigh numbers and the wave numbers of the associated disturbances for the onset of instability as stationary convection have been obtained and the behavior of various parameters on critical thermal Rayleigh numbers has been depicted graphically. The magnetic field, Hall currents found to introduce oscillatory modes, in the absence of these effects the principle of exchange of stabilities is valid.
Mahinder Singh and Chander Bhan Mehta
Copyright © 2013 Mahinder Singh and Chander Bhan Mehta. All rights reserved.

Numerical and Experimental Analysis of the Growth of Gravitational Interfacial Instability Generated by Two Viscous Fluids of Different Densities
Thu, 03 Oct 2013 14:25:54 +0000
http://www.hindawi.com/journals/fluids/2013/532016/
In the geophysical context, there are a wide variety of mechanisms which may lead to the formation of unstable density stratification, leading in turn to the development of the RayleighTaylor instability and, more generally, interfacial gravitydriven instabilities, which involves moving boundaries and interfaces. The purpose of this work is to study the level set method and to apply the process to study the RayleighTaylor instability experimentally and numerically. With the help of a simple, inexpensive experimental arrangement, the RT instability has been visualized with moderate accuracy for real fluids. The same physical phenomenon has been investigated numerically to track the interface of two fluids of different densities to observe the gravitational instability with the application of level set method coupled with volume of fraction replacing the Heaviside function. Good agreement between theory and experimental results was found and growth of instability for both of the methods has been plotted.
Snehamoy Majumder, Debajit Saha, and Partha Mishra
Copyright © 2013 Snehamoy Majumder et al. All rights reserved.