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K. Ganesh Kumar, B.J. Gireesha, N.G. Rudraswamy and M.R. Krishnamurthy

Abstract

An unsteady flow and melting heat transfer of a nanofluid over a stretching sheet was numerically studied by considering the effect of chemical reaction and thermal radiation. The governing non-linear partial differential equations describing the flow problem are reduced to a system of non-linear ordinary differential equations using the similarity transformations and solved numerically using the Runge–Kutta–Fehlberg fourth–fifth order method. Numerical results for concentration, temperature and velocity profiles are shown graphically and discussed for different physical parameters. Effect of pertinent parameters on momentum, temperature and concentration profiles along with local Sherwood number, local skin-friction coefficient and local Nusselt number are well tabulated and discussed.

Open access

Carmen Popa, Violeta Anghelina and Octavian Munteanu

Abstract

The descriptive geometry constitues the foundation of the engineering sciences, so necessary to the specialists of this field. The aim of this paper is to establish the intersection curve between two cylinders and their unfoldings, by using the programmes:AutoCAD and Mathematica. We used the classical method and we first establish the intersection curve and then the cylinders unfoldings. To do this, we used the AutoCAD program. The same unfoldings can be obtained by introducing directly the curve equations (which are inferred) in Mathematica program.

Open access

A.S. Idowu and U. Sani

Abstract

An analysis was carried out for an unsteady magnetohydrodynamic(MHD) flow of a generalized third grade fluid between two parallel plates. The fluid flow is a result of the plate oscillating, moving and pressure gradient. Three flow problems were investigated, namely: Couette, Poiseuille and Couette-Poiseuille flows and a number of nonlinear partial differential equations were obtained which were solved using the He-Laplace method. Expressions for the velocity field, temperature and concentration fields were given for each case and finally, effects of physical parameters on the fluid motion, temperature and concentration were plotted and discussed. It is found that an increase in the thermal radiation parameter increases the temperature of the fluid and hence reduces the viscosity of the fluid while the concentration of the fluid reduces as the chemical reaction parameter increases.

Open access

D. Kiran Prasad, K.V. Ramana and N. Mohan Rao

Abstract

One of the most common incipient losses of integrity in mechanical structures is the development and propagation of cracks. Especially in rotating members like steam turbine rotors etc. cracks, because of their potential, cause catastrophic failures and are a grave threat to an uninterrupted operation and performance. A crack may propagate from some small imperfections on the surface of the body or inside of the material and it is most likely to appear in correspondence to high stress concentration. Crack propagation path is generally determined by the direction of maximum stress or by the minimum material strength. Hence determination of stresses induced has been the focus of attention for many researchers. In the present work, development of a mathematical model to determine the stresses induced in a rotating disc of varying thickness is studied. This model is applied to a steam turbine rotor disc to determine the induced stresses and radial deflection. The mathematical modeling results are validated with the results obtained using Ansys package. The results of the present study will be useful in diagnosing the location and magnitude of maximum stress induced in the turbine rotor disc and stress intensity factor due to the presence of crack.

Open access

František Dzianik, Štefan Gužela and Eva Puškášová

Abstract

The paper presents a comparison of the process properties of two types of the heat exchangers designed for the heat removal from a high temperature helium cooling loop with steady natural circulation of helium. The first considered heat exchanger is a shell and tube heat exchanger with U-tubes and the other one is a helical coil heat exchanger. Using the thermal and hydrodynamic process calculations, the thermal performance of the two alternative heat exchangers are determined, as well as the pressure drops of flowing fluids in their workspaces. The calculations have been done for several defined operating conditions of two considered types of heat exchangers. The operating conditions of heat exchangers correspond to the certain helium flow rates.

Open access

R.R. Gupta and R.R. Gupta

Abstract

The present investigation deals with the propagation of circular crested Lamb waves in a homogeneous micropolar transversely isotropic medium. Secular equations for symmetric and skew-symmetric modes of wave propagation in completely separate terms are derived. The amplitudes of displacements and microrotation are computed numerically for magnesium as a material and the dispersion curves, amplitudes of displacements and microrotation for symmetric and skew-symmetric wave modes are presented graphically to evince the effect of anisotropy. Some special cases of interest are also deduced.

Open access

Florina Violeta Anghelina, Veronica Despa, Carmen Popa and Constantin C. Anghelina

Abstract

It is obvious that all the elements in a metallic prosthesis implanted in the human body may have beneficial or detrimental effects on the tissue-prosthesis interference. For this reason, the precise knowledge of the chemical composition and structure of an implantable metallic material becomes a major requirement for estimating the medical prosthesis behavior and minimizing the risk of rejection of the implant by the human body. This paper presents an elemental and structural analysis of some potentially biocompatible materials, such as AISI 316 and Co-Cr-Mo alloys.

Open access

Nicolae Angelescu, Dan Nicolae Ungureanu, Vasile Bratu and Florin Toma

Abstract

This work is an attempt viewing to emphasize the possibility of using waste - as aggregate - from the demolition of silicoaluminuous refractory linings for manufacturing concrete with aluminuous cement. The article shows further on the possibilities of reducing the cement dosage and of using cheap admixtures.

Open access

Nicolae Angelescu, Dan Nicolae Ungureanu and Florin Toma

Abstract

The paper is an attempt to present and evaluate of the some monolithic refractory materials, originating from our research activity, with potential to be used as the thermoprotective linings for the nonferrous metals and ferrous alloys manufacturing installations in foundries and steelworks.

Open access

G. Manjunatha, C. Rajashekhar, H. Vaidya and K.V. Prasad

Abstract

The present study investigates the combined effects of varying viscosity and heat transfer on a Casson fluid through an inclined porous axisymmetric tube in the presence of slip effects. The modeled governing equations are solved analytically by considering the long wavelength and small Reynolds number approximations. The numerical integration is employed to obtain pressure rise and frictional force. A parametric analysis has been presented to study the effects of the Darcy number, angle of inclination, varying viscosity, velocity slip, thermal slip, yield stress, amplitude ratio, Prandtl number and Eckert number on the pressure rise, pressure gradient, streamlines, frictional force and temperature. The study reveals that an increase in the angle of inclination and viscosity parameter has a proportional increase in the pressure rise. Also, an increase in the porosity causes a significant reduction in the pressure rise.