
Archive issue  vol.7 No.2
No. 
Author(s)  Title 
Pages 
1. 
T.Groşan and I.Pop  Free convection of nonnewtonian fluids over a vertical surface in a porous medium with internal heat generation 
401407 
2. 
R.Nazar, N.Amin and I.Pop  Free convection boundary layer flow on a horizontal circular cylinder with constant heat flux in a micropolar fluid 
409431 
3. 
R.C.Sharma, P.Kumar and S.Sharma  RayleighTaylor instability of Walters' B' elasticoviscous fluid through porous medium 
433444 
4. 
S.N.Ojha  Shock waves in nonideal fluids 
445464 
5. 
S.Nedelcu and A.Postelnicu  Solving the nonlinear problem of gaslubricated hybrid circular bearings. Part II: unsteady case 
465478 
6. 
R.Bassani, E.Ciulli and M.Lorenzetti  Experimental research on hydrostatic bearing in hydraulic actuators 
479489 
7. 
M.Królak and Z.Kołakowski  Buckling and initial postbuckling behaviour of thinwalled shell and plate structures 
491512 
8. 
P.G.Siddheshwar and A.Desseaux  Effect of homogeneous chemical reaction on solutal analog of rayleighbenard convection in a micropolar fluid 
513525 
9. 
P.K.Das and S.C.Dutta  Effect of strength and stiffness deterioration on seismic behaviour of r/c asymmetric buildings 
526564 
10. 
A.V. Kuznetsov  Forced convection in heterogeneous porous media: the effect of thermal dispersion 
565590 
11. 
B.C.Ghosh and P.R.Sengupta  On the hydromagnetic flow of a dusty viscoelastic Maxwell fluid through a rectangular channel 
591618 
12. 
M.E.KlonowskaProsnak and M.Kołodziejczyk  Tests on a new method for numerical solution to the NavierStokes equations. Part II: plane unsteady flow around curvilinear contours 
619652 
13. 
B.C.Majumdar and A.Kumar  Analysis of twolayered gaslubricated porous bearings 
653664 

1.
FREE CONVECTION OF NONNEWTONIAN FLUIDS OVER A VERTICAL SURFACE IN A POROUS MEDIUM WITH INTERNAL HEAT GENERATION
T. GROŞAN and I. POP
Faculty of Mathematics
University of Cluj, R3400 Cluj, CP 253, ROMANIA
email: popi@math.ubbcluj.ro
The effect of the internal heat generation on the free convection from a vertical flat plate embedded in a porous medium saturated with the nonNewtonian fluid is studied. Similarity solutions are obtained for a given form of the internal heat generation. It is found that the present results are in very good agreement with those known from the literature.

Key words: 
nonNewtonian fluid, porous medium, flat plate, convection, boundary layer. 
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2.
FREE CONVECTION BOUNDARY LAYER FLOW ON A HORIZONTAL CIRCULAR CYLINDER WITH CONSTANT HEAT FLUX IN A MICROPOLAR FLUID
R.NAZAR and N.AMIN
Department of Mathematics, Universiti Teknologi Malaysia,
81310 Johor Bahru, Johor, MALAYSIA
I.POP
Faculty of Mathematics, University of Cluj,
R3400 Cluj, CP 253, ROMANIA
email: popi@math.ubbcluj.ro
Numerical solutions for the steady laminar free convection boundary layer flow over a horizontal circular cylinder subjected to a constant surface heat flux in a micropolar fluid are presented in this paper. The governing boundary layer equations are first transformed into a nondimensional form. These equations are then transformed into a set of nonsimilar boundary layers, which are solved numerically using a very efficient implicit finitedifference method known as the Kellerbox scheme. The obtained solution for the material parameter K=0 (Newtonian fluid) and different values of the Prandtl number Pr are used to compare the accuracy of the present method with that known from the open literature. The results are shown to compare very well. The effects of various values of K on the velocity and temperature fields as well as on the wall temperature and local skin friction coefficient are presented through graphs and tables for Pr=0.72 and 1.

Key words: 
circular cylinder, micropolar fluid, free convection, boundary layer, constant heat flux. 
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3.
RAYLEIGHTAYLOR INSTABILITY OF WALTERS' B' ELASTICOVISCOUS FLUID THROUGH POROUS MEDIUM
R.C. SHARMA, P. KUMAR and S. SHARMA
Department of Mathematics, Himachal Pradesh University
SummerHill, Shimla  171005, INDIA
email: shivani_sharma2000@yahoo.com
RayleighTaylor instability of Walters' B' elasticoviscous fluid through a porous medium is considered. For the stable configuration, the system is found to be stable or unstable if the kinematic viscoelasticity (assumed equal for both fluids) is less than or greater than the medium permeability divided by the medium porosity. However, the system is found to be unstable for the potentially unstable configuration. The effects of a uniform horizontal magnetic field and a uniform rotation on the problem are considered separately.

Key words: 
RayleighTaylor instability, porous medium, Walters' B' fluid, uniform horizontal magnetic field, uniform rotation. 
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4.
SHOCK WAVES IN NONIDEAL FLUIDS
S.N. OJHA
Department of Mathematics, S.C.P.G. College
BALLIA  277 001, U.P., INDIA
The problem of propagation of shock waves in nonideal fluids has been discussed. In the course of discussion, the similarity solution method developed by Sedov has been used. The effects due to geometry of the motion, presence of magnetic field and rotation of the fluid on the propagation of shock waves have been discussed separately. The effects of radiation and viscosity have not been taken into account.

Key words: 
shock waves, magnetohydrodynamic, rotating atmosphere. 
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5.
SOLVING THE NONLINEAR PROBLEM OF GASLUBRICATED HYBRID CIRCULAR BEARINGS. PART II: UNSTEADY CASE
S. NEDELCU
Department of Mathematics,
Air Force Academy, Brasov, 2200, ROMANIA
A. POSTELNICU
Department of Fluid Mechanics,
Transilvania University of Brasov, 2200, ROMANIA
email: adip@unitbv.ro
In the paper, a dynamic analysis of gaslubricated hybrid circular bearings is made. The mathematical model is the Reynolds equation in unsteady regimes along with the boundary conditions for a multiple connected domain. Within the hypothesis of a periodic relative motion of bearing surfaces, the method of small perturbations is used. The equations of the model are solved numerically using a difference finite method and finally, the curves of variation of the critical mass versus the eccentricity are obtained.

Key words: 
lubrication, hybrid bearings, compressible fluids, unsteady regime, nonlinear equations. 
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6.
EXPERIMENTAL RESEARCH ON HYDROSTATIC BEARING IN HYDRAULIC ACTUATORS
R. BASSANI, E. CIULLI and M. LORENZETTI
Department of Mechanical,
Nuclear and Industrial Engineering, University of Pisa
Via Diotisalvi 2, 56126 Pisa, ITALY
email: m.lorenzetti@ing.unipi.it
Low fluid losses associated with low friction are an important target for every kind of sealing, in particular for hydraulic actuators. In this work an experimental study on a device with capillary compensated hydrostatic pistons is reported. Experimental results, mainly concern the flow rate and pressure determination for different conditions, show a quite good agreement with the theoretical ones. A possibility to improve the system has been found out.

Key words: 
hydrostatics, fluid seals, capillaries. 
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7.
BUCKLING AND INITIAL POSTBUCKLING BEHAVIOUR OF THINWALLED SHELL AND PLATE STRUCTURES
M. KRÓLAK, Z. KOŁAKOWSKI
Technical University of Łód
Department of Strength of Materials and Structures
ul. Stefanowskiego 1/15, 90924 Łód, POLAND
email: kola@orion.p.lodz.pl
The problem of critical states and initial postbuckling equilibrium paths of thinwalled girders (beamcolumns) built of plate and/or shell elements subjected to compression and bending has been solved. Plate and shell elements can be made of multilayer orthotropic materials. The problem has been solved within the first order approximation of Koiters asymptotic theory, using the transition matrix method. The results of numerical calculations have been presented in the form of plots.

Key words: 
thinwalled structures, composite, buckling, postbuckling, plate, shell. 
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8.
EFFECT OF HOMOGENEOUS CHEMICAL REACTION ON SOLUTAL ANALOG OF RAYLEIGHBENARD CONVECTION IN A MICROPOLAR FLUID
P.G. SIDDHESHWAR
UGCDSA Centre in Fluid Mechanics
Department of Mathematics, Bangalore University
Central College Campus
Bangalore 560 001, INDIA
email: pgsiddheshwar@hotmail.com
A. DESSEAUX
Universite de Valenciennes
I.U.T.  G.M.P., Le Mont Houy  59313
Valenciennes Cedex 9, FRANCE
The solutal analog of the RayleighBenard convection in a reactive micropolar fluid is studied numerically using the RayleighRitz method. The solute concentration is assumed to disappear at a rate which is linearly proportional to the concentration. It is observed that the critical solutal Rayleigh number for this fluid system with homogeneous kinetics is greater than that of a nonreactive fluid system. The results have possible industrial applications.

Key words: 
micropolar fluid, RayleighBenard analog, chemical reaction. 
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9.
EFFECT OF STRENGTH AND STIFFNESS DETERIORATION ON SEISMIC BEHAVIOUR OF R/C ASYMMETRIC BUILDINGS
P.K. DAS, S.C. DUTTA
Department of Applied Mechanics
Bengal Engineering College (Deemed University)
Howrah 711 103, West Bengal, INDIA
email: prithwishbec@netscape.net
Past earthquakes (e.g., 1985 Mexico earthquake) have demonstrated the severe seismic vulnerability of asymmetric buildings due to coupled lateraltorsional vibration in elastic as well as in inelastic range, even under a purely translational ground shaking. Extensive research effort on inelastic behaviour of asymmetric buildings has generally used an elastoplastic or bilinear hysteresis behaviour for the structural loadresisting elements, ignoring the strength and stiffness deteriorating characteristics of RC structural elements under cyclic loading. Hence, these studies could not recognize the possibility of progressively increasing torsional damage of load resisting elements near one edge, due to continuous shifting of centre of resistance caused by such degradations during inelastic excursions. The present study on asymmetric one storey building systems aims to assess these possible detrimental effects. The system responses are studied using a) elastoplastic, b) stiffness degrading, c) strength deteriorating, and d) stiffness degrading as well as strength deteriorating hysteresis models for the loadresisting elements. These responses are expressed in terms of the maximum displacement demand and hysteretic energy demand in loadresisting elements. Variations of these two response quantities are studied for feasible ranges of influencing parameters due to each of the four hysteresis behaviours. The results are compared to understand the effects of stiffness degradation and strength deterioration. The remedial measures are also outlined to control the excessive response found to be generated due to such degradation effects. The study may prove useful to arrive at more justified torsional code provisions.

Key words: 
earthquake, asymmetric buildings, reinforced concrete, stiffness degradation, strength deterioration, torsion, inelastic displacement, hysteretic energy demand. 
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10.
FORCED CONVECTION IN HETEROGENEOUS POROUS MEDIA: THE EFFECT OF THERMAL DISPERSION
A.V. KUZNETSOV
Department of Mechanical and Aerospace Engineering
North Carolina State University
Campus Box 7910, Raleigh, NC 276957910, USA
email: avkuznet@eos.ncsu.edu
This paper presents a new analytical solution to a problem of forced convection in a heterogeneous channel filled with two different layers of isotropic porous media. The BrinkmanForchheimerextended Darcy equation is utilized to describe the fluid flow in the porous layers, and the effect of transverse thermal dispersion is accounted for in the energy equations. Three momentum boundary layers are identified in the channel: a boundary layer at the solid wall and two boundary layers at the interface between the porous media. The dependence of the Nusselt number on the Darcy numbers, Forchheimer coefficients, and particle Reynolds numbers in different parts of the channel is investigated. This study demonstrates that thermal dispersion has a strong effect on the Nusselt number in the channel for large particle Reynolds numbers.

Key words: 
porous media, forced convection, thermal dispersion, heterogeneous media. 
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11.
ON THE HYDROMAGNETIC FLOW OF A DUSTY VISCOELASTIC MAXWELL FLUID THROUGH A RECTANGULAR CHANNEL
B.C. GHOSH
Central Pally, Gangnapur
Dt:Nadia, West Bengal  741233
West Bengal, INDIA
P.R. SENGUPTA
Indian Institute of Mechanics of Continua
Gangnapur  741233, West Bengal, INDIA
The unsteady motion of a dusty viscoelastic Maxwell type conducting fluid under arbitrary pressure gradient through a long uniform tube of rectangular crosssection is studied. Expressions for the velocities of the fluid and particle are obtained by using Laplace transform technique.

Key words: 
hydromagnetic, dusty, Maxwell, Laplace transform. 
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12.
TESTS ON A NEW METHOD FOR NUMERICAL SOLUTION TO THE NAVIERSTOKES EQUATIONS
PART II: PLANE UNSTEADY FLOW AROUND CURVILINEAR CONTOURS
M.E. KLONOWSKAPROSNAK
Institute of Oceanology, Polish Academy of Sciences
81712 Sopot, POLAND
email: klonowsk@ocean.iopan.gda.pl
M. KOŁODZIEJCZYK
Department of Mechanics, Technical University of Białystok
15351 Białystok, POLAND
Similarly as the preceding paper of the authors (Klonowska and Kołodziejczyk, 1999) also the present one deals with the new method (Prosnak and Kosma, 1991) for the determination of unsteady, plane flows of viscous incompressible fluids. The novelty of the method consists in elimination of pressure from the system of the NavierStokes equations by means of integration of the "total" differential of pressure. Consequently  the order of the system resulting from such an elimination is not increased in comparison with the original one, and no artificial, nonphysical boundary conditions occur.
The main difference between the present paper and the previous one consists in geometrical properties of the domain of solution. It is infinite, and bounded by a curvilinear contour. Three contours are considered in the paper: a flat plate, a circle, and the NACA 0012 airfoil. The results prove, that also in these cases the method works properly  at least for rather small values of the Reynolds number. Such a limitation is due to the efficiency of the computers being available at the time, when the calculations were made.

Key words: 
NavierStokes equations, elimination of pressure, conformal mapping, curvilinear grids, doubly connected domains, stretching and compression of subdomains. 
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13.
ANALYSIS OF TWOLAYERED GASLUBRICATED POROUS BEARINGS
B.C. MAJUMDAR and A. KUMAR
Department of Mechanical Engineering
Indian Institute of Technology
Kharagpur721302, INDIA
email: majum@mech.iitkgp.ernet.in
A theoretical estimate is made to evaluate performance characteristics in terms of steady state and stability of twolayered externally pressurized porous gas journal bearings. Assuming only radial flow in the porous medium and considering twodimensional flow in the bearing clearance, basic equations are solved to find load capacity and stability margin. It has been observed that a twolayered bearing gives higher stability when compared with a singlelayered one.

Key words: 
porous bearings, externally pressurized, twolayered, steady state and stability. 
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