Editorial New Developments in Fluid Mechanics and Its Engineering

Hindawi Publishing CorporationMathematical Problems in EngineeringVolume 2013, Article ID 797390, 3 pageshttp://dx.doi.org/10.1155/2013/797390

EditorialNew Developments in Fluid Mechanics andIts Engineering Applications

Oluwole Daniel Makinde,1 Waqar Ahmed Khan,2 and Tirivanhu Chinyoka3

1 Faculty of Military Science, Stellenbosch University, Private Bag X2, Saldanha 7395, South Africa2Department of Engineering Sciences, Pakistan Navy Engineering College, National University of Sciences & Technology,Karachi 75350, Pakistan

3 Center for Research in Computational and Applied Mechanics, University of Cape Town, Rondebosch 7701, South Africa

Correspondence should be addressed to Oluwole Daniel Makinde; [email protected]

Received 8 December 2013; Accepted 8 December 2013

Copyright © 2013 Oluwole Daniel Makinde et al. This is an open access article distributed under the Creative CommonsAttribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work isproperly cited.

Fluid mechanics is an active field of research with manyunsolved or partially solved problems in science and engi-neering. Fluid mechanics can be mathematically complex.Sometimes the problems can best be solved by numericalmethods, typically using computers. Fluids have the ability totransport matter and its properties as well as transmit force;therefore fluidmechanics is a subject that is particularly opento cross-fertilization with other sciences and disciplines ofengineering.The subject of fluid mechanics is highly relevantin such domains as mechanical, chemical, petrochemical,civil, metallurgical, biological, and ecological engineering.

The original papers explored in this special issue includea wide variety of topics such as boundary layer flows,nanofluids dynamics, heat and mass transfer, combustiontheory hydromagnetic flows, gas dynamics, computationalfluid dynamics, thermodynamics analysis, aerodynamics,and non-Newtonian flows. In “Travelling waves solution ofthe unsteady flow problem of a rarefied nonhomogeneouscharged gas bounded by an oscillating plate,” T. Zakaraiaand A. Wahid solved the initial-boundary value problem ofthe Rayleigh flow applied to the system of two-componentplasma (positive ions + electrons), bounded by an oscillatingplate. The ratios between the different contributions of theinternal energy changes are predicted via the extended Gibbsequation for both diamagnetic and paramagnetic plasmas.In “DSMC prediction of particle behavior in gas-particletwo-phase impinging streams,” M. Du et al. investigatedthe behaviour of gas-particle two-phase impinging streams

(GPISs). The collisional interaction of particles was takeninto account by means of a modified direct simulationMonteCarlo (DSMC) method based on a Lagrangian approachand the modified Nanbu method. The results indicatethat the particle distribution in GPIS can be divided intothree zones: particle-collision zone, particle-jetting zone, andparticle-scattering zone. In “Performance analysis of high-speed deep/shallow recessed hybrid bearing,” L. Wang and S.Jiang presented a theoretical analysis of the performance ofdeep/shallow recessed hybrid bearing. By adopting bulk flowtheory, the turbulent Reynolds equation and energy equationare modified and solved numerically. The results indicatethat the load capacity and drag torque increase as the depthbecomes shallower and the width ratio (half angle of deeprecess versus half angle of shallow recess) becomes smaller. In“Feature-parameter-criterion for predicting lean blowout limitof gas turbine combustor and bluff body burner,” H. Zhenget al. proposed a new method named Feature-Parameter-Criterion (FPC) for predicting Lean blowout (LBO) limitusing computational fluid dynamics (CFD) software FLU-ENT.The results show that the simulation of LBO limit basedon FPC is in good agreement with the experiment data (theerrors are about 5%). In “Time-splitting procedures for thenumerical solution of the 2D advection-diffusion equation,” A.R. Appadu and H. H. Gidey presented a spectral analysisof the dispersive and dissipative properties of two time-splitting procedures, namely, locally one-dimensional (LOD)Lax-Wendroff andLOD(1, 5) for the numerical solution of the

2 Mathematical Problems in Engineering

2D advection-diffusion equation. An optimization techniqueis implemented to find the optimal value of temporal step sizethat minimizes the dispersion error for both schemes whenthe spatial step is chosen as 0.025. In “Model of infiltrationof spent automotive catalysts by molten metal in process ofplatinum metals recovery,” A. Fornalczyk et al. analysed themodel for the washing-out process of precious metals fromspent catalysts by the use of molten lead in which the metalflow is caused by the rotating electromagnetic field andthe Lorentz force. The developed model enabled analysis ofthe impact of spacing between the catalysts and the supplycurrent on the degree of catalyst infiltration by the moltenmetal. In “A fractal model for the maximum droplet diameterin gas-liquid mist flow,” X. H. Tan et al. made use of fractaltheory to describe liquid droplet size distribution in gas-liquid mist flow. The results reveal that maximum dropletdiameter decreases with an increase in gas superficial velocitybut increases with an increase in liquid superficial velocity.Droplet fractal dimension also increases with an increasein gas superficial velocity but decreases with an increasein liquid superficial velocity. In “Framework for the shapeoptimization of aerodynamic profiles using genetic algorithms,”D. Lopez et al. developed a framework for the shape opti-mization of aerodynamics profiles using computational fluiddynamics (CFD) and genetic algorithms.The results obtaineddemonstrated the effectiveness of the developed tool. In“Nonlinear characteristics of helicopter rotor blade airfoils:an analytical evaluation”, C. Rotaru examined the effect ofunsteadiness on airfoil operating under nominally attachedflow conditions away from stall using Theodorsen’s theory,where the aerodynamic response (lift and pitching moment)is considered as a sum of noncirculatory and circulatoryparts. The apparent mass contributions to the forces andpitching moments, which are proportional to the instanta-neous motion, are included as part of the quasi-steady result.In “The use of fractional order derivative to predict the ground-water flow,” A. N. Atangana and Bildik derived the analyticalsolution of the-time-fractional groundwater flow equation(TFGFE) via the Laplace-Carson transform method and thegeneralized Wright function. This solution obtained is inperfect agreement with the data observed from the pumpingtest performed by the Institute for Groundwater Study onone of its borehole settled on the test site of the Universityof the Free State. In “Unsteady analyses of a control valve dueto fluid-structure coupling,” Y. Xie et al. analysed the couplingmechanism between the structure and the fluid system atthe control valve numerically. The results help understandthe processes that occur in the valve flow path leading tothe pressure control instability observed in the control valvein the combined cycle power plants (CCPP). In “The flowof a variable viscosity fluid down an inclined plane with afree surface,” M. S. Tshehla investigated the combined effectsof convective heating and temperature dependent variableviscosity on fluid flowing down an inclined plane with a freesurface.Themodel problem is tackled numerically; graphicalresults are displayed and discussed quantitatively. In “A newnumerical approach of MHD flow with heat and mass transferfor the UCM fluid over a stretching surface in the presenceof thermal radiation,” S. Shateyi and G. T. Marewo made

use of spectral relaxation method in order to numericallyinvestigate the magnetohydrodynamic boundary layer flowwith heat and mass transfer of an incompressible upper-convected Maxwell fluid over a stretching sheet in thepresence of viscous dissipation and thermal radiation as wellas chemical reaction. The results are obtained for velocity,temperature, concentration, skin friction, and Nusselt num-ber. In “Analytical solution of flow and heat transfer over apermeable stretching wall in a porous medium,” M. Dayyanet al. investigated the boundary layer flow through a porousmedium over a stretching porous wall with respect to firstand second laws of thermodynamics for both isothermal andisoflux cases. It is shown that the rate of heat transfer increaseswith Reynolds number, Prandtl number, and suction to thesurface. In “Calculation analysis of pressure wave velocity ingas and drillingmud two-phase fluid in annulus during drillingoperations,” Y. Lin et al. proposed a united wave velocitymodel based on pressure gradient equations in drillingoperations, gas-liquid two-fluid model, the gas-drilling mudequations of state, and small perturbation theory. It is shownthat the drop of pressure causes an increase in void fractionalong the flow direction. The wave velocity tends to increasewith the increase in back pressure and the decrease of gasinflux rate and angular frequency, significantly in low range.In “Spectral local linearisation approach for natural convectionboundary Layer flow,” S. S.Motsa et al. utilised a spectral locallinearisation method (SLLM) to numerically solve a modelproblem describing natural convection boundary layer flowwith domain transformation. A comparative study betweenthe SLLM and existing results in the literature was carried outto validate the results.Themethod has shown to be a promis-ing efficient tool for nonlinear boundary value problems as itgives converging results after few iterations. In “Gel character-istics of urea-formaldehyde resin under shear flow conditions,”D. Wang et al. investigated the gel characteristics of urea-formaldehyde resin (UFR) chemical grout under shear flowconditions experimentally using an apparatus which consistsof a magnetic stirrer and a viscometer. The results showthat the grouting flow rate influences the gelling time. Fasterflow rates will cause longer gelling time, which means thatthe time for the grout to gel during the flowing processunder shear flow conditions is longer than that under staticconditions. In “On the comparison between compact finitedifference and pseudospectral approaches for solving similarityboundary layer problems,” P. G. Dlamini et al. presenteda comparison of the compact finite difference approachagainst the pseudospectral approach in solving similarityboundary layer problems. It is shown that the results of thetwo approaches are comparable in terms of accuracy forsmall systems of equations. For larger systems of equations,the proposed compact finite difference approaches are moreaccurate than the spectral-method-based approaches. In“Radiation and magnetohydrodynamics effects on unsteadyfree convection flow in a porous medium,” S. Ulhaq et al.examined the unsteady MHD free convection flow nearan exponentially accelerated infinite vertical plate throughporous medium with uniform heat flux in the presence ofthermal radiation. Exact solutions are obtained by the Laplacetransform method. The effects of pertinent parameters such

Mathematical Problems in Engineering 3

as the radiation parameter, Grashof number, Prandtl number,and time on velocity, temperature, and skin friction are showngraphically and discussed quantitatively. In “CFD simulationof heat transfer and friction factor augmentation in a circulartube fitted with elliptic-cut twisted tape inserts,” S. D. Salmanet al. presented a numerical simulation of swirling flow in atube induced by elliptic-cut and classical twist tape insertsusing CFD package (FLUENT-6.3.26). The results show thatthe heat transfer rate and friction factor in the tube equippedwith elliptic-cut twist tape (ECT) are significantly higher thanthose fitted with classical twist tape (CTT). In “Shock wavesolutions for some nonlinear flowmodels arising in the study ofa non-Newtonian third grade fluid,” T. Aziz et al. presenteda new class of closed-form shock wave solutions for somenonlinear problems arising in the study of a third gradefluid model using the Lie symmetry reduction technique.In “Hydromagnetic stagnation-point flow towards a radiallystretching convectively heated disk,” S. Shateyi and O. D.Makinde presented a numerical solution for steady MHDstagnation-point flow and heat transfer of an electricallyconducted incompressible viscous fluid over a convectivelyheat and radially stretching disk surface. Pertinent resultson the effects of various thermophysical parameters onthe velocity and temperature fields as well as local skinfriction and local Nusselt number are discussed in detailand shown graphically and/or in tabular form. In “MHDboundary layer flow due to exponential stretching surfacewith radiation and chemical reaction,” Y. I Seini and O.D. Makinde investigated the combined effects of thermalradiation and first order homogeneous chemical reaction onhydromagnetic boundary layer flow of a viscous, steady, andincompressible fluid over an exponential stretching sheet.It was found that the rate of heat transfer at the surfacedecreases with increasing values of the transverse magneticfield parameter and the radiation parameter. In “Entropygeneration analysis in a variable viscosity MHD channelflow with permeable walls and convective heating,” A. S.Eegunjobi and O. D. Makinde numerically analysed inherentirreversibility in a steady flow of an incompressible variableviscosity electrically conducting fluid through a channel withpermeablewalls and convective surface boundary conditions.The results revealed that entropy generation minimizationcan be achieved by appropriate combination of the regulatedvalues of thermophysical parameters controlling the flowsystems. In “Boundary layer flow past a wedge moving in ananofluid,” W. A. Khan and I. Pop numerically studied theproblem of steady boundary layer flow of nanofluid pasta stretching wedge with a parallel free stream velocity. Itis found that the velocity at the surface increases/decreaseswith stretching/shrinking parameters while the temperatureincreases with both Brownian motion and thermophoresisparameters.

Thus, the papers in this special issue, representing a broadspectrum of both theoretical and experimental approachesand areas of investigation, demonstrate the wide array ofnew development in fluid mechanics and its engineeringapplications. We are certain that the papers published in thisspecial issue will contribute to advancement of knowledge inthe field of fluid mechanics and provide scientists, engineers,

industries, research scholars, and practitioners’ latest theoret-ical and technological achievements in fluid mechanics andits various engineering applications.

Acknowledgments

Wewould like to thank the authors for their contribution andthe reviewers for their collaboration.

Oluwole Daniel MakindeWaqar Ahmed KhanTirivanhu Chinyoka

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Editorial New Developments in Fluid Mechanics and Its Engineering