bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mixed convection in a buoyancy‐assisted two‐sided lid‐driven cavity filled with a porous medium
Authors: Vishnuvardhanarao Elaprolu , Das Manab Kumar 
Published: May 2009

PurposeThe purpose of this paper is to consider a two‐dimensional, steady, mixed convection flow in an enclosure filled with a fluid‐saturated uniform porous medium. The left wall is moving down and the right wall is moving up and are maintained at cold and hot constant temperatures, respectively. The top and the bottom walls are fixed and are thermally insulated.Design/methodology/approachThe governing equations are normalized and solved numerically with appropriate boundary conditions by finite‐volume approach using third‐order accurate scheme (deferred QUICK).FindingsThe study is conducted by varying the key parameters, i.e. Richardson number (Ri=Gr/Re2), Darcy number (Da=κ /H2) and Grashof number (Gr=gβ H3 Δ T/ν 2) and fixing Prandtl number at (Pr=0.71). A parametric study is conducted and a set of streamline and isotherm plots are presented. The average Nusselt number reaches a value of 1 asymptotically when the Ri is gradually increased for Gr up to 103. The asymptotic value is 1.5 for Gr=104. A heat transfer correlation is also presented.Originality/valueThe study of the mixed convection problem with lid‐driven flows in enclosures will be useful in cooling of electronic devices, lubrication technologies, chemical processing equipment, etc.
Convective heat transfer augmentation through vortex shedding in sinusoidal constricted tube
Authors: Batina J. , Batchi M. , Blancher S. , Creff R. , Amrouche C. 
Published: May 2009

PurposeThe purpose of this paper is to analyse the convective heat transfer of an unsteady pulsed, laminar, incompressible flow in axisymmetric tubes with periodic sections. The flow is supposed to be developing dynamically and thermally from the duct inlet. The wall is heated at constant and uniform temperature.Design/methodology/approachThe problem is written with classical homogeneous boundary conditions. We use a shift operator to impose non‐homogeneous boundary conditions. Consequently, this method introduces source terms in the Galerkin formulation. The momentum equations and the energy equation which govern this problem are numerically solved in space by a spectral Galerkin method especially oriented to this situation. A Crank‐Nicolson scheme permits the resolution in time.FindingsFrom the temperature field, the heat transfer phenomenon is presented, discussed and compared to those obtained in straight cylindrical pipes. This study showed the existence of zones of dead fluid that locally have a negative influence on heat transfer. Substantial modifications of the thermal convective heat transfer are highlighted at the entry and the minimum duct sections.Practical implicationsPulsated flows in axisymmetric geometries can be applied to medical industries, mechanical engineering and technological processes.Originality/valueOne of the original features of this study is the choice of Chebyshev polynomials basis in both axial and radial directions for spectral methods, combined with the use of a shift operator to satisfy non‐homogeneous boundary conditions.
The entropy generation for a rotating sphere under uniform heat flux boundary condition in forced‐convection flow
Authors: Antar Mohamed A. , El‐Shaarawi Maged A.I. 
Published: May 2009

PurposeThe purpose of this paper is to investigate the problem of entropy generation around a spinning/non‐spinning solid sphere subjected to uniform heat flux boundary condition in the forced‐convection regime.Design/methodology/approachThe governing continuity, momentum, energy and entropy generation equations are numerically solved for a wide range of the controlling parameters; Reynolds number and the dimensionless spin number.FindingsThe dimensionless overall total entropy generation increases with the dimensionless spin number. The effect of increasing the spin number on the fluid‐friction component of entropy generation is more significant compared to its effect on heat transfer entropy generation.Research limitations/implicationsSince the boundary‐layer analysis is used, the flow is presented up to only the point of external flow separation.Practical implicationsEntropy generation analysis can be used to evaluate the design of many heat transfer systems and suggest design improvements.Originality/valueA review in the open literature indicated that no study is available for the entropy generation in the unconfined flow case about a spinning sphere.
Natural convection heat transfer augmentation in a partially heated and partially cooled square cavity utilizing nanofluids
Authors: Das Manab Kumar , Shridhar Ohal Pravin 
Published: May 2009

PurposeThe purpose of this paper is to investigate the behaviour of nanofluids numerically inside a partially heated and partially cooled square cavity to gain insight into heat transfer and flow processes induced by a nanofluid.Design/methodology/approachA model is developed to analyze the behaviour of nanofluids taking into account the solid volume fraction χ. The transport equations are solved numerically with finite volume approach using SIMPLEC algorithm.FindingsComparisons with previously published work on the basis of special cases are performed and found to be in excellent agreement. Five different relative positions of the active zones are considered.While circulation depend strongly on the total exit length. Governing parameters were 103 < Gr < 107 but due to space constraints the results for 104 < Gr <107 are presented. It is found that both the Grashof number and solid volume fraction χ affect the fluid flow and heat transfer in the cavity. CopperWater nanofluid is used with Pr = 6.2 and solid volume fraction is varied as 0, 4, 8, 12, 16 and 20 per cent. Detailed results are presented for flow pattern and heat transfer curves.Originality/valueThe present study focusses on the analysis of several parameters on the heat transfer characteristics of nanofluids within the enclosure.
Effects of injection (suction) on a steady mixed convection boundary layer flow over a vertical cone
Authors: Ravindran R. , Roy Satyajit , Momoniat E. 
Published: May 2009

PurposeThe purpose of this paper is to study the steady mixed convection flow over a vertical cone in the presence of surface mass transfer when the axis of the cone is inline with the flow.Design/methodology/approachIn this case, the numerical difficulties to obtain the non‐similar solution are overcome by applying an implicit finite difference scheme in combination with the quasilinearization technique.FindingsNumerical results are reported here to display the effects of Prandtl number, buoyancy and mass transfer (injection and suction) parameters at different stream‐wise locations on velocity and temperature profiles, and on skin friction and heat transfer coefficients.Research limitations/implicationsThermo‐physical properties of the fluid in the flow model are assumed to be constant except the density variations causing a body force term in the momentum equation. The Boussinesq approximation is invoked for the fluid properties to relate the density changes to temperature changes and to couple in this way the temperature field to the flow field.Practical implicationsConvective heat transfer over a stationary cone is important for the thermal design of various types of industrial equipments such as heat exchangers, conisters for nuclear waste disposal, nuclear reactor cooling systems and geothermal reservoirs, etc.Originality/valueThe combined effects of thermal diffusion and surface mass transfer on a vertical cone has been studied.
Radiation effects on hydromagnetic free convective and mass transfer flow of a gas past a circular cylinder with uniform heat and mass flux
Authors: EL‐Hakiem M.A. 
Published: May 2009

PurposeThe purpose of this paper is to highlight the effect of combined heat and mass transfer characteristics of magnetohydrodynamic (MHD) free convection flow of an electrically conducting Newtonian fluid on circular cylinder with uniform heat/mass flux, taking into consideration the effects of uniform transverse magnetic field and thermal radiation.Design/methodology/approachAn analysis is performed to study the momentum, combined heat and mass transfer characteristics of MHD free convection flow past a circular cylinder surface under the effect of thermal radiation with uniform heat and mass flux. By using Lie group method, the infinitesimal generators of governing equations are calculated. Using the resulting generators for the boundary value problem, the equations are transformed into an ordinary differential system. Numerical solutions of the outcoming non‐linear differential equations are found by using a combination of a Runge–Kutta algorithm and shooting technique.FindingsApplication of a magnetic field normal to the flow of an electrically conducting fluid gives rise to a resistive force that acts in the direction opposite to that of the flow. This resistive force tends to slow down the motion of the fluid along the cylinder and causes increases in its temperature and concentration and hence the respective changes in the wall shear stress, local Nusselt and Sherwood numbers as the magnetic parameter, respectively are changed with various values of angle which is measured in degrees from the front stagnation point on the surface. It is noted that these coefficients reduced as the magnetic parameter increases. Also, the effect of thermal radiation works as a heat source and so the quantity of heat added to the fluid increases, therefore the local Nusselt number reduced as the radiation parameter increases.Research limitations/implicationsAn analysis is performed to study the momentum, combined heat and mass transfer characteristics of MHD free convection flow of an electrically conducting Newtonian fluid on circular cylinder with uniform heat/mass flux with the effects of uniform transverse magnetic field and thermal radiation.Practical implicationsThis paper provides a very useful source of coefficient of heat and mass transfer values for engineers planning to transfer heat and mass by using electrically conducting gases with uniform heat/mass flux.Originality/valueThe combined heat and mass transfer of an electrically conducting gases on free convection flow in the presence of magneto and thermal radiation effects are investigated and can be used by different engineers working on industry, geothermal, geophysical, technological and engineering applications.
Mixed convection flow of a micropolar fluid near a non‐orthogonal stagnation‐point on a stretching vertical sheet
Authors: Lok Y.Y. , Pop I. , Ingham D.B. , Amin N. 
Published: May 2009

PurposeThe purpose of this paper is to study theoretically the steady two‐dimensional mixed convection flow of a micropolar fluid impinging obliquely on a stretching vertical sheet. The flow consists of a stagnation‐point flow and a uniform shear flow parallel to the surface of the sheet. The sheet is stretching with a velocity proportional to the distance from the stagnation point while the surface temperature is assumed to vary linearly. The paper attempts also to show that a similarity solution of this problem can be obtained.Design/methodology/approachUsing a similarity transformation, the basic partial differential equations are first reduced to ordinary differential equations which are then solved numerically using the Keller box method for some values of the governing parameters. Both assisting and opposing flows are considered. The results are also obtained for both strong and weak concentration cases.FindingsThese results provide information about the effect of a/c (ratio of the stagnation point velocity and the stretching velocity), σ (shear flow parameter) and K (material parameter) on the flow and heat transfer characteristics in mixed convection flow near a non‐orthogonal stagnation‐point on a vertical stretching surface. The results show that the shear stress increases as K increases, while the heat flux from the surface of the sheet decreases with an increase in K.Research limitations/implicationsThe results in this paper are valid only in the small region around the stagnation‐point on the vertical sheet. It is found that for smaller Prandtl number, there are difficulties in the numerical computation due to the occurrence of reversed flow for opposing flow. An extension of this work could be performed for the unsteady case.Originality/valueThe present results are original and new for the micropolar fluids. They are important in many practical applications in manufacturing processes in industry.
Flow simulation in a complex fluidics using three turbulence models and unstructured grids
Authors: Wang Junye , Priestman Geoffrey H. 
Published: May 2009

PurposeThe purpose of this paper is to simulate the behaviour of the symmetrical turn‐up vortex amplifier (STuVA) to obtain insight into its maximum through‐flow operation within the eight‐port STuVA, and understand the relation between its design parameters and flow characteristics. Furthermore, it is to test the performance of different turbulent models and near‐wall models using the same grid, the same numerical methods and the same computational fluid dynamics code under multiple impingement conditions.Design/methodology/approachThree turbulence models, the standard k‐ε, the renormalization group (RNG) k‐ε model and the Reynolds stress model (RSM), and three near‐wall models have been used to simulate the confined incompressible turbulent flow in an eight‐port STuVA using unstructured meshes. The STuVA is a special symmetrical design of turn‐up vortex amplifier, and the simulation focused on its extreme operation in the maximum flow state with no swirling. The predictions were compared with basic pressure‐drop flow rate measurements made using air at ambient conditions. The effect of different combinations of turbulence and near‐wall models was evaluated.FindingsThe RSM gave predictions slightly closer to the experimental data than the other models, although the RNG k‐ε model predicted nearly as accurately as the RSM. They both improved errors by about 3 per cent compared to the standard k‐ε model but took a long time for convergence. The modelling of complex flows depends not only on the turbulence model but also on the near‐wall treatments and computational economy. In this study a good combination was the RSM, the two layer wall model and the higher order discretization scheme, which improved accuracy by more than 10 per cent compared to the standard k‐ε model, the standard wall function and first order upwind.Research limitation/implicationsThe results of this paper are valid for the global pressure drop flow rate. It should be desirable to compare some local information with the experiment.Originality/valueThis paper provides insight into the maximum through‐flow operation within the eight‐port STuVA to understand the relation between its design parameters and flow characteristics and study the performance of turbulence and near wall models.
Application of axisymmetric analog to unstructured grid for aeroheating prediction of hypersonic vehicles
Authors: Parhizkar H. , Karimian S.M.H. 
Published: May 2009

PurposeThe purpose of this paper is to present an engineering inviscid‐boundary layer method for the calculation of convective heating rates on three‐dimensional non‐axisymmetric geometries at angle of attack.Design/methodology/approachBased on the axisymmetric analog, convective heating rates are calculated along the surface streamlines which are determined using the inviscid properties calculated on an unstructured grid.FindingsSince the method is capable of using inviscid properties calculated on an unstructured grid, it is applicable to a variety of configurations and it requires much less computational effort than a Navier‐Stokes code. The results of the present method are evaluated on different wing body configurations in laminar and turbulent hypersonic equilibrium flows. In comparison to experimental data, the present results are found to be fairly accurate in the windward and leeward regions.Practical implicationsWith this approach, heating rates can be predicted on general three‐dimensional configurations at hypersonic speeds in an accurate and fast scheme.Originality/valueIn order to calculate the heating rates at any specific point on the surface, a technique is developed to calculate the inviscid surface streamlines in a backward manner using the inviscid velocity components. The metric coefficients are also calculated using a new simple technique.
Numerical solution of wetting fluid spread into porous media
Authors: Markicevic B. , Navaz H.K. 
Published: May 2009

PurposeThe purpose of this paper is to develop a general numerical solution for the wetting fluid spread into porous media that can be used in solving of droplet spread into soils, printing applications, fuel cells, composite processing.Design/methodology/approachA discrete capillary network model based on micro‐force balance is numerically implemented and the flow for an arbitrary capillary number can be solved. At the fluid interface, the boundary condition that accounts for the capillary pressure jump is used.FindingsThe wetting fluid spread into porous medium starts as a single‐phase flow, and after some particular number of the porous medium characteristic length scales, the multi‐phase flow pattern occurs. Hence, in the principal flow direction, the phase content (saturation) decreases, and in the lower limit for the capillary number sufficiently small, the saturation should become constant. This qualitative saturation behavior is observed irrespective of the flow dimensionality, whereas the quantitative results vary for different flow systems.Research limitations/implicationsThe numerical solution has to be expanded to solve the spread of the fluid in the porous medium after there is no free fluid left at the porous medium surface.Practical implicationsIt is shown that the multi‐phase flow can develop even on a small domain due to the porous medium heterogeneity. Neglecting the medium heterogeneity and flow type can lead to a large error as shown for the droplet spread time in the porous medium.Originality/valueThis is believe to be the only paper relating to solving the droplet spread into porous medium as a multi‐phase flow problem.
On MHD boundary‐layer flow and mass transfer past a vertical plate in a porous medium with constant heat flux
Authors: Makinde O.D. 
Published: May 2009

PurposeThe hydromagnetic mixed convection flow of an incompressible viscous electrically conducting fluid and mass transfer over a vertical porous plate with constant heat flux embedded in a porous medium is investigated.Design/methodology/approachUsing the Boussinesq and boundary‐layer approximations, the fluid equations for momentum, energy balance and concentration governing the problem are formulated. These equations are solved numerically by using the most effective Newton–Raphson shooting method along with fourth‐order Runge–Kutta integration algorithm.FindingsIt was found that for positive values of the buoyancy parameters, the skin friction increased with increasing values of both the Eckert number (Ec) and the magnetic field intensity parameter (M) and decreased with increasing values of both the Schmidt number (Sc) and the permeability parameter (K).Practical implicationsA very useful source of information for researchers on the subject of hydromagnetic flow in porous media.Originality/valueThis paper illustrates the effects of magnetic field on mixed convective boundary layer flow past a vertical plate embedded in a saturated porous medium with mass transfer and a constant heat flux.
Marketing in the Great Recession: an executive guide
Authors: Grossberg Kenneth Alan 
Published: May 2009

PurposeThe world economy is likely to worsen because of the consumer's fears created by a cascade of financial and business catastrophes. To adapt their marketing approach, executives need guidance on how to respond to the sea change in the attitudes of individual customers during this current Great Recession. this paper aims to investigate this issue.Design/methodology/approachGiven that experts believe that we have entered a period of austerity marketing, which is defined as marketing to consumers who do not want to spend, the paper shows how companies can reconcile consumers' fear, their aspirations for comfort, and their new reluctance to flaunt extravagance. His research indicates that marketers will have to include reassurance as part of their appeal.FindingsSome businesses think that the fail‐safe approach is to emphasize great value, but this will require them to understand their evolving customers' value system better than ever in order to sell to them successfully; in particular their need for self‐respect, status and self‐fulfillment.Research limitations/implicationsThe author, a professor of marketing at Waseda University in Tokyo has also been a senior marketing executive for major global businesses. Much of his research is based on first‐hand observation.Practical implicationsIn the consumer markets of the USA, Japan and Europe, one new marketing approach that addresses consumers' higher needs is that of indulgent parsimony, or frugal indulgence. The theory is that recession‐shocked consumers are shopping for less costly goods and services but nonetheless want their purchases to provide comfort and relief from stress.Originality/valueFor the next few years, marketers should encourage guilt‐free (and altruistic) gratification by customers. A potentially successful marketing approach could articulate this customer mindset: “I'm worth it … because I've examined all the alternatives and this one gives me the best value for something I really do need”. Indulgent parsimony – offering reassurance, value and self‐esteem at bargain – may prove most effective.
How to cut costs in a recession – with help from employees
Authors: Katzenbach Jon , Bromfield Paul 
Published: May 2009

PurposeThe economic downturn requires prudent cost reductions, yet only 10 percent of companies sustain cost reductions after three years. Some of the most successful cost cutters have learned to engage their workforce to embrace both the rational and emotional arguments for taking action and to focus on what the company is and will become. This paper aims to investigate this issue.Design/methodology/approachThe task of securing employee commitment to cost reductions is not easy, and requires paying close attention to six principles which this paper introduces. This is referred to as the motivating cost discipline (MCD) approach.FindingsIn the example application of the MCD approach, costs were cut by 30 percent with employee satisfaction and price lifted 20 percent.Research limitations/implicationsThe six principles offered are collected from observing best practice in the field.Practical implicationsThis paper shows that beyond the mandate to an immediately lower cost structure, it is also possible to motivate people in positive ways that produce emotional as well as rational commitment.Originality/valueContrary to conventional wisdom, it is possible to get more costs out sooner and realize benefits that are more lasting; the secret is fully engaging employees in the cost cutting process, which this paper helps to do.