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Indian Journal of Engineering & Materials Sciences

 

ISSN : 0971-4588

 

CODEN : IEMSEW

VOLUME 10

 NUMBER 5

OCTOBER 2003

 

 

CONTENTS

 

Engineering
 

Analysis of non-reacting flow in an aircraft gas turbine engine afterburner model using finite volume method

 

341

M Rajkumar & V Ganesan

 

 

 

Numerical simulation of normal shock wave/turbulent boundary-layer interaction over a bump surface

 

353

R C Mehta

 

 

 

Determination of the first transition of mode shapes for buckling and free vibration problems of uniform simply supported beams on variable two parameter elastic foundations through the concept of equivalent uiform Winkler foundation

 

 

359

G Venkateswara Rao

 

 

 

Buckling of an orthotropic cylindrical thin shell with continuously varying  thickness under a dynamic loading

 

365

Abdullah H Sofiyev, Erol Keskin, Hakan Erdem & Zihni Zerin

 

 

 

Propagation of Lamb waves in transversely isotropic piezoelectric elastic plate

371

J N Sharma & Mohinder Pal

 

 

 

Effect of the variation of conical liner apex angle and explosive ignition point on shaped charge jet formation

 

381

I Gokhan Aksoy & Sadri Sen

 

 

 

Transient free convection flow of a viscous incompressible fluid past an infinite vertical plate with periodic heat flux

 

390

V M Soundalgekar, R Deka & U N Das

 

 

 

Activated sludge process—A rationality in design

397

Devendra Swaroop Bhargava & Anirudh Prakash

 

 

 

Materials Science
 

Characterizing transition metal perovskites with PAC spectroscopy

403

R Dogra & A C Junqueira

 

 

 

Wear resistance of leaded aluminium alloy prepared by mechanical alloying

413

Vinod Kumar, Albert Yanthan, P R Soni & T V Rajan

 

 

 

Flow behaviour of β-Sn single crystals

416

A E Ekinci, N Ucar, G Cankaya & B Duzgun

 

 

 

Study of black and composite agglomerates of cork as thermal insulating materials

419

M A Diaz-Diez, A Diaz-Parralezo, A Macias-Garcia, P de la Rosa Blanco & V Gomez-Serrano

 

 

 

Preparation of net shape Al2O3/Al3Ni in-situ composites by reactive melt penetration

424

V Venkateswara Rao

 

 

 

Electrical conduction in chemically deposited CdSe1-x Tex mixed/alloyed thin film

427

P D More & L P Deshmukh

 

 

 

Growth and characterization of vacuum deposited cadmium telluride thin films

433

K N Shreekanthan, V B Kasturi & G K Shivakumar

 


 

 

Indian Journal of Engineering & Materials Sciences 

Vol. 10, October 2003, pp. 341-352

 

Analysis of non-reacting flow in an aircraft gas turbine engine afterburner model using finite volume method

M Rajkumar & V Ganesan

 

This paper focuses on the aerodynamics of the non-reacting flow inside an aero-gas turbine engine afterburner by carrying out a three-dimensional CFD analysis using the finite volume approach. A 60° sector of the afterburner with all the complexities has been modelled to take advantage of the symmetry of the design. The computational methodology employed SIMPLE algorithm for pressure velocity coupling, RNG k–e model for turbulence in an unstructured and non-uniform grid. The analysis has been carried out for sea level inlet conditions. A recirculation zone was seen to be formed behind the V-gutters and inner wall of the diffuser. The performance of the diffuser was found to be good and the Mach number just upstream of the V-gutter was found to be in line with requirements. The pressure loss was in line with successful designs and the nozzle performance was found to be satisfactory.  The predicted flow fields are verified using existing experimental results. The results for various mass flow rates and different geometries are presented for the closed nozzle position.

 

 

 

Indian Journal of Engineering & Materials Sciences 

Vol. 10, October 2003, pp. 353-358

 

Numerical simulation of normal shock wave/turbulent boundary-layer interaction over a bump surface

R C Mehta

 

Numerical computation of the normal shock wave/turbulent boundary layer interaction over a bump is discussed here. The time-dependent, two-dimensional Reynolds averaged compressible Navier-Stokes equations have been solved employing three-stage Runge-Kutta time-stepping scheme in-conjunction with a finite volume discretization of spatial coordinates. The closure of these equations is obtained using the Baldwin-Lomax turbulence model. Artificial dissipation terms are added to the numerical scheme to maintain numerical stability and they contain a blend of second and fourth differences of the state vector with an appropriate pressure switch that detects the presence of strong pressure gradients. The formation of the λ-shock is simulated by setting downstream pressure condition using an adjustable aerofoil. The numerical solution captures the λ-shock associated with the separated boundary layer inside the channel, which is very sensitive to the exit condition of the flow. Comparisons have been made with available experimental data such as interferogram and wall pressure distributions. They are found to be in good agreement.

 

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 10, October 2003, pp. 359-364

 

Determination of the first transition of mode shapes
for buckling and free vibration problems of uniform
simply supported beams on variable two parameter
elastic foundations through the concept of
equivalent uniform Winkler foundation

G Venkateswara Rao

 

Two parameter foundation models represent accurately the foundation characteristics compared to the simple, single parameter model (Winkler model). The widely used two parameter foundation model is the Pasternak foundation model. Further, beams on elastic foundation exhibit an interesting phenomenon of changing mode shapes (from the first mode to the second mode and so on) for both buckling and free vibration problems at specific foundation stiffnesses parameter(s). While, evaluating the foundation stiffness parameter for beams on Winkler foundation, for both the buckling and vibration problems is easy, in the case of the two parameter uniform or variable foundations, the procedure is more involved. Further, most of the practicing engineers are very familiar with the Winkler foundation than the two parameter foundations. Hence, it will be very useful and elegant if one obtains an equivalent uniform Winkler foundation to represent the uniform or variable two parameter elastic foundations, for example, the Pasternak foundation, such an attempt is made in this paper. The efficacy of the concept of the equivalent uniform Winkler foundation, in determining the first transition stiffness parameter(s) of mode shapes for the buckling and free vibration problems of beams on either a uniform or a variable Pasternak foundation is clearly demonstrated.

 

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 10, October 2003, pp. 365-370

 

Buckling of an orthotropic cylindrical thin shell with continuously varying thickness under a dynamic loading

Abdullah H Sofiyev, Erol M Keskin, Hakan Erdem & Zihni Zerin

 

The buckling of an orthotropic composite cylindrical shell with variable thickness, subjected to a dynamic loading, is reported here. At first, the fundamental relations and Donnell type dynamic buckling equation of an orthotropic cylindrical shell with variable thickness have been obtained. Then, employing Galerkin’s method, these equations have been reduced to a time dependent differential equation with variable coefficients. Finally, for different initial conditions and approximation functions, applying the Ritz type variational method, analytical expression has been found for the dynamic factor. Using these results, the effect of the variations of the power of time in the external pressure expression, the loading parameter and the ratios of the Young’s moduli on the dynamic factor are studied numerically for the case when the thickness of the cylindrical shell varies as a power and exponential functions. It has been observed that these effects change the dynamic factor of the problem in the heading appreciably.

 

 

 

Indian Journal of Engineering & Materials Sciences

 Vol. 10, October 2003, pp. 371-380

 

Propagation of Lamb waves in transversely isotropic piezoelectric elastic plate

J N Sharma & Mohinder Pal

 

The propagation of Lamb waves in a homogeneous, transversely isotropic, piezoelectric plate subjected to charge free and electrically shorted, stress free boundary conditions is investigated. Secular equations for the plate in closed form and isolated mathematical conditions for symmetric and antisymmetric wave mode propagation in completely separate terms are derived. It is shown that motion of purely transverse (SH) mode gets decoupled from rest of the motion and remains unaffected due to piezoelectric effects. At short wavelength limits the secular equation for symmetric and skew-symmetric waves in both charge free and electrically shorted, stress free plate reduce to Rayleigh surface wave frequency equations because a finite plate in such situation behave like a semi-infinite medium. The amplitudes of displacement and electrical potential have also been computed in case of symmetric and skew-symmetric motions of the plate. Finally, numerical solution is carried out for cadmium-selenide (6 mm class) material. The dispersion curves and amplitudes of displacements and electrical potential for symmetric and antisymmetric wave modes are presented graphically in order to illustrate and compare the analytical results. The theory and numerical computations is found to be in close agreement. The various wave characteristics are found to be more stable and realistic in the presence of piezoelectric effects than in the absence of such a effect thereby making such materials more viable for practical importance and use.

 

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 10, October 2003, pp. 381-389

 

Effect of the variation of conical liner apex angle and
explosive ignition point on shaped charge jet formation

I Gokhan  Aksoy   &  Sadri Sen

 

Shaped charge technology has an important role in the military and commercial areas, as bullets and warheads made by the shaped charge principle are especially used for penetration to target and demolition purposes. In early studies, the solution of shaped charge problems has been obtained by using analytical methods. However, over the past decade, numerical methods based on finite difference and finite element methods are used for simulating this complex process. In this study, the effects of varying parameters (conical liner apex angle and explosive ignition place) are investigated by a numerical modelling of the shaped charge performed using the Dyna2D hydrodynamic code. The 81 mm precision shaped charge warhead which is designed by Ballistic Research Laboratory (BRL) is taken as a reference charge. The simulations are carried out from 13° to 46° of the apex angle because both the jets do not occur completely for the apex angles equal or smaller than 13° and the velocity decreases for the apex angles larger than 46°. The velocity of the jet tip increases very slowly with the decrease of the apex angle from 38° to 13°. When the apex angle in this range decreases the jet tip becomes shorter while the jet slug gets longer and thicker. Additionally, it is realized that it needs longer time for the jet formation, and moreover, the jet does not occur completely. For those reasons, the parametric evaluations are realized by changing the conical liner apex angle (38°, 40°, 42°, 44°, 46°) and explosive ignition place (central point, plane and ring). As a result of the variation of the parameters, some important variations are determined in pressure, velocity gradient and jet formation of the shaped charge through simulation. The present results are found in good agreement with the reported results.

 

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 10, October 2003, pp. 390-396

 

Transient free convection flow of a viscous incompressible fluid past an infinite vertical plate with periodic heat flux

V M Soundalgekar, R Deka & U N Das

 

An exact solution by the Laplace-transform technique to the transient free convection flow past an infinite vertical plate in the presence of periodic heat flux superposed on the steady heat flux at the plate, is presented in this paper. It is observed that the transition from conduction to convection takes place at a distance nearer and nearer to the leading edge when wt or frequency w or the Prandtl number is high. In case of flow of high Prandtl number fluids, when the frequency is high, the transition from conduction to convection may take place at the leading edge itself.

 

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 10, October 2003, pp. 397-402

 

Activated sludge process — A rationality in design

 Devendra Swaroop Bhargava & Anirudh Prakash

 

An attempt has been made here to determine the various conditions of operating variables that influence the design and efficiency of the process. Nomographs have been evolved for a handy and quick aid in the design of an ASP under the varying conditions and values of the parameters that significantly affect the performance of the ASP.

 

 

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 10, October 2003, pp. 403-412

 

Characterizing transition metal perovskites with
PAC spectroscopy

R Dogra & A C Junqueira

 

Among the several experimental techniques based on different principles available to investigate the materials, the microscopic techniques based on hyperfine interaction form a subclass that characterizes a material at the smallest possible atomic scale. After an introduction to the basic properties of the transition metal perovskites of type ABO3, the hyperfine interactions along with hyperfine technique such as Perturbed Angular Correlation (PAC) have been briefly described in this paper. The characteristics of the materials analyzed have been expressed in terms of internal magnetic hyperfine fields, electric field gradients and the microscopic point symmetry at the probe site. In particular in this review, a special attention has been paid to the information that can be obtained from a PAC spectroscopy applied to perovskite materials, which may help to understand the microscopic nature of different physical environments around the probe nucleus.

 

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 10, October 2003, pp. 413-415

 

 

Wear resistance of leaded aluminium alloy
prepared by mechanical alloying

Vinod Kumar, Albert Yanthan, P R Soni & T VRajan

 

A1-10 wt% Pb alloy was prepared by mechanical alloying (MA) in a laboratory attritor mill. The X-ray diffraction studies of MA powder was carried out. After degassing, the powder was consolidated by hot pressing. Studies on microstructure, grain size and pore structures in the consolidated alloy were carried out using image analysis technique. Wear resistance of the alloy was evaluated using pin-on-disc method.

 

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 10, October 2003, pp. 416-418

 

Flow behaviour of -Sn single crystals

A E Ekinci, N Ucar, G Cankaya & B Duzgun

 

The flow behaviour of b-Sn single crystals by tension test was studied as a function of orientation and strain rate. It was found that the flow stress curves were strongly dependent on crystal orientation and strain rate. In addition, while the slip traces change with the strain rate, there was not any detectable effect of crystal orientation.

 

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 10, October 2003, pp. 419-423

 

Study of black and composite agglomerates of
cork as thermal insulating materials

M A Díaz-Díez, A Díaz-Parralejo, A Macías-García, P de la Rosa Blanco
& V Gómez-Serrano

 

 

The behaviour of cork agglomerates as thermal insulating materials was studied. The products used were black agglomerate (BA) and composite agglomerate (CA), which were prepared from black regranulate (BR) of cork. In the preparation of the agglomerates, the specimen thickness for BA and the particle size of BR and the resin dosage for CA were varied. A procedure was proposed for measuring the thermal conductivity of materials in a granular or powder form. The thermal conductivity of BR, BA, and CA was determined using a Ketherm QTM-D3 fast meter, provided with an adapter QTM PA1. The behaviour as a thermal insulating material can be improved by decreasing the particle size for BR and by increasing the specimen thickness for BA. In the case of CA, the best behaviour is shown when the intermediate particle size of BR and the highest resin dosage are used in its preparation. Frequently, the insulating behaviour is better for CA than for BR, and also for BA than for CA.

 

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 10, October 2003, pp. 424-426

 

Preparation of net-shape Al2O3/Al3Ni in
situ composites by reactive melt penetration

V Venkateswara Rao

 

By reacting silica preforms with a molten Al-Ni alloy net-shape, in situ Al2O3/Al3Ni composites were prepared. Presence of Ni in the melt was found to slow down the reaction between silica and aluminium. The density of the composites was found to be 3.98 ± 0.12 g/cc, and they were found to be much harder than Al2O3/Al composites.

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 10, October 2003, pp. 427-432

 

 

Electrcial conduction in chemically deposited
CdSe1-xTex mixed/alloyed thin films

P D More & L P Deshmukh

 

CdSe1-xTex films are crystalline in nature over the whole range of composition with a predominant wurzite structure. The compositional analysis showed that in Cd-rich films compared to Te content, Se content in the films is slightly greater for each of the compositions. The surface morphology showed diffused grained polycrysalline texture with overgrowth developed in some cases. The temperature dependences of electrical conductivity, thermoelectric power, carrier concentration and mobility are examined and the influence of the Te-concentration on them is investigated and explained in terms of Petritz grain boundary scattering limited model. The dc electrical conductivity is found to decrease with an increase in x up to 0.08 and thereafter increased continuously as x was increased. The results indicated that the electrical transport properties of chemically deposited Cd (Se, Te) films are governed by the intergrain barrier potential, which is sensitively dependent on the Te-concentration in the CdSe films.

 

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 10, October 2003, pp. 433-436

 

Growth and characterization of vacuum deposited
cadmium telluride thin films

K N Shreekanthan,V B Kasturi & G K Shivakumar

 

Semiconducting thin films of cadmium telluride, both p-type and n-type, have been prepared by conventional thermal evaporation technique. The influence of various growth parameters such as the rate of deposition, deposition temperature, post-deposition heat treatment, and source material composition has been investigated. The films deposited at high deposition rates and low substrate temperatures exhibited an excess of tellurium and showed a p-type conductivity, whereas those deposited at high substrate temperature and low deposition rates contained excess cadmium and are n-type in nature. An intrinsic bandgap of 1.49 eV for stoichiometric films obtained by both electrical and optical characterization is reported.