Similarity Solutions for MHD Visco-Elastic Flow over a Permeable and Non-Linearly Quadratic Stretching Sheet

A notable study on similarity solutions for visco-elastic (Walters liquid B’ model) fluid flow over a permeable and nonlinearly stretching sheet is investigated in the presence uniform magnetic field. Recently Raptis and Perdikis [1] studied the similarity solutions for boundary layer flow over an impermeable quadratic non-linear stretching sheet using a stream function of the kind......

Effect of viscous dissipation on natural convection in a non-Darcy porous medium saturated with non-Newtonian fluid of variable viscosity

This paper investigates the influence of the effect of viscous dissipation and radiation on natural convection heat transfer from vertical flat plate in a non-Darcy porous media saturated with non-Newtonian fluid of variable viscosity. The wall and the ambient medium are maintained at constant but different levels of temperature. The Ostwald-de Waele power law model is used to characterize the non-Newtonian fluid behavior. The viscosity of the fluid is assumed to follow Reynolds viscosity model. Rosseland approximation is used to describe the radiative heat flux in the energy equation. The governing equations in their non-similar form are solved numerically by local non-similarity method. The effects of variable viscosity, viscous dissipation, radiation and the power-law index parameters on the velocity and temperature profiles as well as on the heat transfer coefficient are analyzed. © Kairi et al.published_or_final_versio

Heat and Mass Transfer in MHD Micropolar Fluid in The Presence of Diffusion Thermo and Chemical Reaction

This work is devoted to investigating the influence of diffusion thermo effect on hydromagnetic heat and mass transfer oscillatory flow of a micropolar fluid over an infinite moving vertical permeable plate in a saturated porous medium in the presence of transverse magnetic field and chemical reaction. The dimensionless equations are solved analytically using perturbation technique. The effects of the various fluid flow parameters entering into the problem on the velocity, microrotation, temperature and concentration fields within the boundary layer are discussed with the help of graphs. Also the local skin-friction coefficient, the wall couple stress coefficient, and the rates of heat and mass transfer coefficients are derived and shown in graphs. Comparison of the obtained numerical results is made with existing literature and is found to be in good agreement

Beberapa masalah aliran lapisan sempadan olakan dengan kesan gelinciran dan tanpa gelinciran pada permukaan

Fenomenon kesan gelinciran pada permukaan boleh berlaku pada permukaan bendalir-pepejal dan pada permukaan lapisan bendalir-bendalir, terutama bagi sesetengah bendalir berskala kecil dalam mikroaliran. Dalam kebanyakan kajian aliran lapisan sempadan yang telah dilakukan oleh para penyelidik, didapati kesan gelinciran adalah baik bagi meningkatkan kadar pemindahan haba pada permukaan yang diperlukan dalam suatu proses penyejukan. Bagi aliran tanpa gelinciran, ciri-ciri pemindahan haba bergantung pada masalah aliran yang dikaji. Dalam tesis ini, model matematik dibina untuk mengkaji ciri-ciri aliran dan pemindahan haba bagi lima masalah aliran lapisan sempadan yang dihadkan kepada aliran mantap dua matra dalam bendalir likat tak mampat. Masalah pertama dan kedua masing-masing mempertimbangkan aliran berdekatan titik genangan dan aliran hidromagnet, keduaduanya pada helaian tegak meregang. Masalah ketiga dan keempat mempertimbangkan syarat sempadan gelinciran, masing-masing bagi aliran terhadap titik genangan pada permukaan tegak dan aliran terhadap helaian telap mengecut. Sementara itu, masalah kelima melibatkan aliran pada permukaan meregang/mengecut di bawah aliran ricih luar dengan syarat sempadan permukaan olakan. Formulasi model matematik diperoleh dengan menurunkan persamaan pembezaan separa tak linear kepada persamaan pembezaan biasa menggunakan penjelmaan keserupaan. Analisis kepada sistem persamaan yang terhasil dimulakan dengan menyelesaikan masalah secara berangka menggunakan kaedah kotak Keller atau kaedah tembakan. Kaedah kotak Keller diatur cara menggunakan perisian MATLAB 7, manakala kaedah tembakan menggunakan atur cara “bina dalam” dalam perisian Maple 12. Seterusnya, nilai-nilai berangka bagi pekali geseran kulit dan nombor Nusselt setempat serta profil-profil halaju dan suhu diperoleh untuk pelbagai nilai parameter menakluk seperti parameter nisbah halaju, parameter keapungan, parameter magnet, parameter gelinciran halaju dan terma, nombor Prandtl, parameter olakan, parameter sedutan/semburan dan parameter regangan/kecutan. Keputusan berangka yang diperoleh dipersembahkan dalam bentuk jadual dan graf. Didapati gelinciran halaju mengurangkan pekali geseran kulit tetapi meningkatkan kadar pemindahan haba pada permukaan, manakala kesan gelinciran terma adalah sebaliknya. Suhu permukaan pula didapati bertambah dengan kehadiran medan magnet dan dengan syarat sempadan permukaan olakan. Selain itu, parameter-parameter menakluk yang lain turut mempengaruhi pekali geseran kulit dan nombor Nusselt setempat, di samping kewujudan penyelesaian dual atau unik, bagi masalah-masalah yang dikaji

Thermophoretic deposition of particles in fully developed mixed convection flow in a parallel-plate vertical channel: the full analytical solution

In a recent paper (Grosan et al. in Heat Mass Transf 45:503-509, 2009) a mostly numerical approach to the title problem has been reported. In the present paper the full analytical solution is given. Several new features emerging from this approach are discussed in detai

Nanofluid Flow over a Permeable Surface with Convective Boundary Conditions and Radiative Heat Transfer

We investigate the effects of thermal radiation and convective boundary conditions on heat and mass transfer in nanofluid flow over a permeable flat plate. The mathematical model for the nanofluid incorporates variations in the nanoparticle volume fraction of up to 20%. The performance of two water-based nanofluids, namely, stable suspensions of copper and gold nanoparticles in water was investigated. The governing partial differential equations were transformed into ordinary ones using a similarity transformation and solved numerically. The numerical results were validated by comparison with previously published results in the literature. The main focus of this paper is to study the fluid and surface parameters such as the radiation parameter, and suction/injection parameter, solute concentration profiles, as well as the skin friction coefficient and heat and mass transfer rates were conducted

The entrainment theorem for wall driven boundary layer flows

Boundary layer flows driven by permeable plane surfaces, stretching with power-law velocities are considered in the presence of an applied lateral mass flux. The relationship between the wall shear stress and the entrainment velocity (the transversal velocity at the outer edge of the boundary layer) as a function of the mass transfer parameter f w is examined analytically by using the Merkin transformation method. It is shown that at the value of f w where the wall shear stress vanishes, the entrainment velocity reaches a minimum or maximum value. This relationship between two characteristic quantities at the outer and inner edge of the boundary layer, respectively, is referred to as entrainment theorem. Its physical content is analyzed in the paper in some detai

The effect of joule heating, thermal radiation on the MHD convective Heat and Mass Transfer flow of a variable electrically conducting micro polar fluid.

The magneto-hydrodynamic (MHD) and effect of Joule heating, thermal radiation, chemical reaction and dissipation on the convective heat and mass transfer flow of a micro polar fluid past a stretching sheet with variable electric conductivity in the presence of a magnetic field. The non-linear equations governing the flow, heat and mass transfer have been solved numerically by employing fourth order Runge – Kutta shooting method. Results are obtained for a range of Eckert number (Ec), magnetic, Joule heating, micro rotation parameter, heat source parameter, thermal radiation parameter and chemical reaction parameter. The sheet is assumed to be non-isothermal with prescribed heat flux varying with length. Keywords: Joule heating, magnetic field, micro polar fluid, stretching sheet

Inter- and intra- observer reliability of the offera method for assessing exposure risk of computer work-related to wmsds

The purpose of this study was to evaluate inter- and intra- observer reliability of the observers assessing office workers performing their jobs using the Office Ergonomic Risk Assessment (OFFERA) method. 44 Industrial Engineering students at UTHM participated in a training session on inter- and intra- observer reliability. The period interval between inter- and intra- observer training session was 1 week. Three different jobs were assessed by observer using the OFFERA method. Through the three different tasks, the average of inter- and intraobserver reliability ranged between good to very good agreement. Meanwhile, the level of agreement for the intra-observer (K=0.68-0.96) was higher than the inter-observer (K=0.62- 0.94). Items with the strongest agreement (K=0.96) were related to armrest, document holder and keyboard wrist rest. The OFFERA method has both good and very good agreement in terms of reliability. The observers stated that it was easy to evaluate the ergonomic risk at office using this simple tool