Archive issue - vol.5 No.4



   No.   Author(s) - Title
Pages

   1.
 

 Postelnicu A. and Minea D. -- Finite element analysis of the hemodynamics in the human carotid artery bifurcation
 

759-772
 

   2.
 

 Chan B.H.M., Chan S.L. and Law S.S. -- Nonlinear behaviour of pitched roof steel frames subjected to sequential loads
 

773-793
 

   3.
 

 Niola V. and Longobardi M. -- Fuzzy logic system for superficial defects classification in metal patches
 

795-802
 

   4.
 

 Shimada K., Nishida H. and Yamaguchi H. -- Theoretical analysis of the hydrodynamic characteristics of electrorheological fluid in a parallel duct flow
 

803-820
 

   5.
 

 Shtemler Y.M., Levitsky M.P., Shreiber I.R., Levitsky S.P. and Berkovich Y. -- Two-stage atomization model for liquid jet disintegration in gas atomizers
 

821-842
 

   6.
 

 Chakraverty S., Bhat R.B. and Stiharu I. -- Vibration of annular elliptic orthotropic plates using two dimensional orthogonal polynomials
 

843-866
 

   7.
 

 Bhattacharyya B. and Chakraborty S. -- Stochastic finite element method for sensitivity analysis of structures
 

867-882
 

   8.
 

 Sharma R.C., Sunil and Pal M. -- On couple-stress fluid heated from below in porous medium in the presence of rotation
 

883-896
 

   9.
 

 Naeem R.K. and Shad Ahsan S.M. -- On the plane steady flows of a viscous incompressible fluid of finite electrical conductivity in the presence of a magnetic field
 

897-911
 

   10.
 

 El-Hakiem M.A. and Gorla R.S.R. -- Radiative effects in non-Darcy axisymmetric free convection in a porous medium
 

913-921
 

   11.
 

 Elliott J.W. and Strange M.E. -- Viscous-inviscid interactions for surface-cooled axisymmetric boundary-layer flows
 

923-957
 

   12.
 

 Böhle U., Kamlah M., Munz D. and Tsakmakis C. -- Macroscopic description of the non-linear electro-mechanical coupling in ferroelectrics
 

959-970
 

   13.
 

  -- In memory of Professor John Brand MARTIN
 

971-973
 

 



1.

FINITE ELEMENT ANALYSIS OF THE HEMODYNAMICS
IN THE HUMAN CAROTID ARTERY BIFURCATION

A. POSTELNICU

Transilvania University of Brasov,
Department of Fluid Mechanics,
Brasow, 2200, ROMANIA

D. MINEA
Transilvania University of Brasov,
Department of Neurology,
Brasov, 2200, ROMANIA

     The present paper brings new lights on blood flow patterns in rigid artery bifurcation models, differing in angle of bifurcation. Using the ANSYS 5.4/FLOTRAN package, a numerical analysis in two dimensions was performed, under physiologically relevant flow conditions. For two bifurcation models, one with large angle the other with a small one, the distributions of velocities, shear-stress and pressure in the domain of carotid artery bifurcation have been obtained. It is argued and proved that the vascular geometry at the bifurcation level represents a risk factor in atherogenesis, the relevant factors for this process being the flow separation, reversal flow regions and wall shear stress.

Key words:

finite element simulation, blood flow, bifurcation, atherosclerosis.

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2.

NONLINEAR BEHAVIOUR OF PITCHED ROOF STEEL FRAMES
SUBJECTED TO SEQUENTIAL LOADS

B.H.M. CHAN, S.L. CHAN and S.S. LAW

Dept of Civil and Structural Engineering
The Hong Kong Polytechnic University
HONG KONG, P.R. CHINA

     This paper investigates the importance of sequential loads on the ultimate behaviour of pitched roof steel frames. In most previous studies related to inelastic or advanced analysis, loads are assumed to apply proportionally, which contrasts to the more realistic cases of invariant gravitational loads and varying lateral loads due to wind and seismic forces. Based on the previous work on the inelastic and large deflection analysis, the tangent modulus method is coded in a computer program. Numerical examples are given to demonstrate the discrepancy between these two approaches and to indicate the potential danger of using the over-simplified proportional load assumption in design and analysis of semi-rigid pitched roof steel frames.

Key words:

second-order analysis, sequential load, proportional load, pitched roof steel frame, semi-rigid frame.

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3.

FUZZY LOGIC SYSTEM FOR SUPERFICIAL DEFECTS
CLASSIFICATION IN METAL PATCHES

V. NIOLA

Mechanic Department for Energetic, University of Naples,
Facolta di Ingegneria DIME, Universita di Napoli,
via Claudio 21 cap. 80125, Napoli, ITALIA
e-mail: vniola@cds.unina.it

M. LONGOBARDI
GEPIN Engineering S.p.A. , Centro Direzionale
di Napoli - Isola E3 - 80100 Napoli, ITALIA
e-mail: marco.longobardi@gepinengineering.it

     The system achieved is an integration of the identification system, we planned and carried out, as we previously described (Niola et al., 1999). From the depth map onwards, that is the output of the identification system, the classification system, operating on the single lines of the map, reconstructs through interpolation the level lines of the image, which are to be fitted to Fuzzy set; in order to do this, a mixed neuro-fuzzy technique is adopted.
     The so achieved input Fuzzy sets, level lines that have been modelled, are compared to the output Fuzzy sets, which reproduce a parameterisation of the defect according to its depth, by means of inference rules planned on purpose.
     The final result will give a quantification of the defect found, besides pointing out the area in which it has been noticed.

Key words:

fuzzy set, membership functions, level lines, superficial defects, adaptive neural-fuzzy, modelling, classification.

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4.

THEORETICAL ANALYSIS OF THE HYDRODYNAMIC
CHARACTERISTICS OF ELECTRORHEOLOGICAL FLUID IN
A PARALLEL DUCT FLOW

K. SHIMADA

Akita Prefectural University
Faculty of System Science and Technology
Department of Machine Intelligence and System Engineering
84-4 Aza-Ebinokuchi, Tsuchiya, Honjoh, Akita, 015-0055, JAPAN
e-mail: shimada@akita-pu.ac.jp

H. NISHIDA
Toyama Polytechnic College
1289-1 Kawabuchi, Uozu, Toyama, 937-0856, JAPAN

H. YAMAGUCHI
Doshisya University, Department of Mechanical Engineering
Kyotanabe, Kyoto, 630-0321, JAPAN

     Theoretical analysis was conducted of the hydrodynamic characteristics of the two-dimensional flow of electrorheological fluid between parallel plates by using the mechanical dynamic model proposed herein. The model includes the Voigt model and a slider. It can present four types of relations between shear stress and shear rate. The theoretical results were compared with the experimental data. The theoretical analysis explains the experimental results qualitatively. The qualitative tendency is the same for the four types of relations between shear rate and shear stress. Based on the theoretical results, velocity distribution of flow in four types of relations is not influenced by shear stress and shear rate. This finding differs from that for rotational flow around a rotating disk. The pressure difference depends on apparent viscosity. The local Reynolds number depends on the local velocity at a low given flow velocity and on the local kinematic viscosity at a high given flow velocity.

Key words:

fluid dynamics, internal flow, viscoelastic fluid, electrorheological fluid, pressure difference, two-dimensional flow, mechanical dynamic model, viscosity, Reynolds number, electric field.

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5.

TWO-STAGE ATOMIZATION MODEL FOR LIQUID JET
DISINTEGRATION IN GAS ATOMIZERS

Y.M. SHTEMLER, M.P. LEVITSKY and I.R. SHREIBER

Institute for Industrial Mathematics
4/24 Hanachtom Str., Beer-Sheva 84249, ISRAEL

S.P. LEVITSKY
School of Engineering
71 Bazel Str., Beer-Sheva 84100, ISRAEL

Y. BERKOVICH
Israel Electric Corporation
POB 10, Haifa 31000, ISRAEL

     Atomization of a liquid jet in a convergent-divergent gas nozzle is studied both theoretically and experimentally. The jet enters the nozzle through a central tube and is primarily disintegrated in the vicinity of the tube exit. An integral model allows cumbersome calculations to be avoided. The model uses idealized schemes for the coarsely and finely dispersed mixture after primary and secondary atomization, respectively. Comparison of theoretical results with experimental data demonstrates the applicability of the model for prediction of the atomizer's geometry and operating conditions necessary for producing the finest possible mixture.

Key words:

modeling, liquid disintegration, atomization shock.

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6.

VIBRATION OF ANNULAR ELLIPTIC ORTHOTROPIC PLATES USING
TWO DIMENSIONAL ORTHOGONAL POLYNOMIALS

S. CHAKRAVERTY

Central Building Research Institute, Roorkee University
Roorkee, 247-667, U.P., INDIA

R.B. BHAT
Department of Mechanical Engineering, Concordia University
Maisonneuve Boulevard West, Montréal
Québec H3G 1M8, CANADA

I. STIHARU
Department of Mechanical Engineering, Concordia University
1455 De Maisonneuve Boulevard West, Montréal
Québec H3G 1M8, CANADA

     The free vibration natural frequencies of specially orthotropic annular elliptic and circular plates are analyzed by the Rayleigh-Ritz method, using two-dimensional boundary characteristic orthogonal polynomials generated following a recurrence scheme as assumed shape functions. The first eight natural frequencies are reported here for various values of aspect ratios of the outer and inner ellipse. Results are given for various boundary conditions at the inner and outer edges of the annular plate. The influence of the material property as it changes from isotropic to orthotropic on the natural frequencies is presented graphically. When the inner hole of the annular plate becomes zero i.e. for rectangular orthotropic full circular and elliptic plates, the results are compared with those that are available in the existing literature, and are found to be in good agreement. Presented results may be used as bench marks for validating those obtained by approximate methods such as the finite element method.

Key words:

vibration of orthotropic elliptic plates, orthogonal two-dimensional polynomials, polynomials generation recurrence scheme, boundary conditions of plate, annular elliptic plates.

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7.

STOCHASTIC FINITE ELEMENT METHOD FOR SENSITIVITY
ANALYSIS OF STRUCTURES

B. BHATTACHARYYA

Department of Applied Mechanics, Bengal Engineering College
Howrah - 711 103, INDIA

S. CHAKRABORTY
Department of Civil Engineering, Bengal Engineering College
Howrah - 711 103, INDIA

     The conventional sensitivity analysis of structures is based on the assumption of complete certainty of design parameters. However, occurrence of uncertainty is unavoidable in structures. In the present work, an attempt has been made to study the response sensitivity, considering the effect of uncertainty in structural design parameters. The random parameters are modeled as Gaussian stochastic process and simulated through covariance matrix decomposition. The advantages of Neumann expansion technique has been utilized in deriving the finite element solution of the response sensitivity within the framework of Monte Carlo simulation. Numerical examples are presented to explain the accuracy and efficacy of Neumann expansion method over direct simulation the process.

Key words:

sensitivity, uncertain parameter, stochastic finite element, Monte Carlo simulation, Neumann expansion.

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8.

ON COUPLE-STRESS FLUID HEATED FROM BELOW IN POROUS
MEDIUM IN THE PRESENCE OF ROTATION

R.C. SHARMA

Himachal Pradesh University
Department of Mathematics
Summer Hill, Shimla - 171 005, INDIA

SUNIL
Regional Engineering College
Department of Applied Sciences
Hamirpur, (H.P.) - 177 005, INDIA

M. PAL
Government Degree College
Department of Mathematics
Palampur, (H.P.) - 176 061, INDIA

     A layer of a couple-stress fluid heated from below in a porous medium is considered to include the effect of uniform rotation. For the case of stationary convection, the couple stress may hasten the onset of convection in the presence of rotation while in the absence of rotation, it always postpones the onset of convection. For the case of stationary convection, rotation postpones the onset of convection. Graphs have been plotted by giving numerical values to the parameters, to depict the stability characteristics. Rotation is found to introduce oscillatory modes in the system, which were non-existent in its absence. A sufficient condition for the non-existence of overstability is obtained.

Key words:

couple-stress fluid heated from below, porous medium, rotation.

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9.

ON THE PLANE STEADY FLOWS OF A VISCOUS INCOMPRESSIBLE
FLUID OF FINITE ELECTRICAL CONDUCTIVITY IN THE PRESENCE OF
A MAGNETIC FIELD

R.K. NAEEM and S.M. SHAD AHSAN

University of Karachi, Department of Mathematics
Karachi-75270, PAKISTAN

     Basic equations describing the motion of a viscous incompressible fluid of finite electrical conductivity in the presence of a magnetic field (1) for constant vorticity flows are recast in a new form. It is indicated that the other flow variables can be expressed either in terms of the magnetic flux function 'fi' or the stream function 'psi' where these functions satisfy a partial differential equation whose every solution, including Naeem (1996), is a solution to the basic flow equations and (2) for variable vorticity flows an unknown function f(r) is introduced in the basic flow equations. The solutions are determined and one solution admits, as a particular case, Naeem's solution by appropriately choosing the arbitrary constants therein. Some applications of the solutions to physically possible situations are also presented.

Key words:

plane steady flows, viscous incompressible fluid, magnetic field, MFD flows, electrically conducting viscous fluid.

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10.

RADIATIVE EFFECTS IN NON-DARCY AXISYMMETRIC FREE CONVECTION IN A POROUS MEDIUM

M.A. EL-HAKIEM

South Valley University
Faculty of Science, Mathematics Department
Aswan, EGYPT

R.S.R. GORLA
Cleveland State University
Mechanical Engineering Department
Cleveland, Ohio 44115, U.S.A.

     An analysis is presented for the effect of radiation on non-Darcy axisymmetric free convection in a saturated porous medium. Similarity solutions are obtained for two cases: variable surface temperature condition and uniform surface heat flux condition. Discussion is provided for the effects of radiation, non-Darcy parameter and lateral surface mass flux parameter on heat transfer. The rate of heat transfer in the non-Darcy case is less than in the corresponding Darcy case.

Key words:

radiation, porous media, non-Darcy model and free convection.

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11.

VISCOUS-INVISCID INTERACTIONS FOR SURFACE-COOLED AXISYMMETRIC BOUNDARY-LAYER FLOWS

J.W. ELLIOTT and M.E. STRANGE

Department of Mathematics,
University of Hull, Hull HU6 7RX. U.K.

     A theoretical, high Reynolds number, investigation into the combined influence of surface cooling and curvature on the stability and transition properties of a compressible axisymmetric boundary-layer is presented. Here we consider the boundary-layer flow along a semi-infinite circular cylinder where the temperature of the cylinder surface is kept significantly below the free-stream temperature and the cylinder radius is comparable with the boundary-layer thickness. Here we concentrate on linear, viscous-inviscid interactive Tollmien-Schlichting modes, rather than the inviscid, inflectional kind.

Key words:

surface cooling, axisymmetric flow, boundary layer.

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12.

MACROSCOPIC DESCRIPTION OF THE NON-LINEAR
ELECTRO-MECHANICAL COUPLING IN FERROELECTRICS

U. BÖHLE, M. KAMLAH, D. MUNZ and C. TSAKMAKIS

Forschungszentrum Karlsruhe GmbH, Institut für Materialforschung II
Postfach 3640, D-76021 Karlsruhe, GERMANY

     Our objective is the construction of a phenomenological ferroelectricity model for general electro-mechanical loading histories, which is simple enough to be implemented in an FE-code with reasonable expenditure. In this paper, we motivate and verify the one-dimensional formulation of such a model. This is done by introducing remanent polarization and remanent strain as internal variables besides stress, strain, electric field and polarization. Polarization induced anisotropy is taken into account to the extent deemed necessary. For the sake of simplicity, no rate effects are included. By bilinear approximation the following characteristic phenomena of macroscopic ferroelectricity are represented: dielectric hysteresis, polarization induced piezoelectricity, butterfly hysteresis, ferroelastic hysteresis, mechanical depolarization, field dependent coercitive stress.

Key words:

piezoceramics, ferroelectricity, phenomenological modeling, finite element implementation.

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