Archive issue - vol.3 No.4



   No.   Author(s) - Title
Pages

   1.
 

  -- 75-th Anniversary of Professor Zinovii Pinkhusovich SHULMAN
 

535-537
 

   2.
 

 Mohammadein A., El-Kabeir S. M., El-Hakiem M. A. and Gorla R.S.R -- Variable viscosity effects on natural convection in micropolar fluid at an axisymetric stagnation point
 

539-552
 

   3.
 

 Shang D.Y., Wang B.X. and Takhar H.S. -- Measurements of the velocity field of the laminar boundary layer for water free convection along an isothermal vertical flat plate
 

553-570
 

   4.
 

 Lee C.C. and Allaire P.E. -- Nonlinear transient analysis of point rub effects in a flexible rotor
 

571-588
 

   5.
 

 Grzeszczyk S. and Lipowski G. -- Effects of low-calcium fly ash on the rheology of fresh cement pastes
 

589-600
 

   6.
 

 Kurashige M. and Yamamoto K. -- Evaluation of interlaminar shear stresses in a fiber-reinforced laminated beam by the ifrm theory
 

601-619
 

   7.
 

 Singh P.C., Patra B. and Maulik T.N. -- Two collinear griffith cracks in an orthotropic strip with punches
 

621-653
 

   8.
 

 Layek G. -- Numerical computation of viscous flow field past circular cylinder
 

655-677
 

   9.
 

 Wroński S., Molga W., Rudniak L. and Hubacz R. -- Modelling of solute migration and its adsorption in porous layers
 

679-694
 

   10.
 

 Kiełbasa J. -- Hot-wire anemometer with the modulated overheating ratio-an instrument for measuring non-isothermal flows
 

695-714
 

 



2.

VARIABLE VISCOSITY EFFECTS ON NATURAL CONVECTION
IN A MICROPOLAR FLUID AT AN AXISYMETRIC STAGNATION POINT

A. A. MOHAMMADEIN, S. M. El-KABEIR,

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

Rama Subba Reddy GORLA,
Mechanical Engineering Department,
Cleveland State University,
Cleveland, Ohio 44115, USA

     A three-dimensional boundary layer solution is presented for the natural convection in a micropolar fluid in the vicinity of an axisymmetric stagnation point on heated vertical surfaces. The effects of variable viscosity are included. The governing equations for the velocity, microrotation and temperature fields are solved numerically.

Key words:

natural convection, micropolar fluids, axisymmetric stagnation flow.

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3.

MEASUREMENTS OF THE VELOCITY FIELD OF THE LAMINAR
BOUNDARY LAYER FOR WATER FREE CONVECTION ALONG
AN ISOTHERMAL VERTICAL FLAT PLATE

De-Yi SHANG

Department of Fenous Metallurgy,
Northeastern University, Shenyang, CHINA.

Bu-Xuan WANG
Department of Thermal Engineering,
Tsinghua University, Beijing, CHINA.

H.S. TAKHAR
Manchester School of Engineering,
University of Manchester,
Manchester, M13 9PL, U.K.

     The velocity field of laminar free convection for water flowing past an isothermal vertical flat plate is measured for different temperature conditions using the laser Doppler velocimetry. In the experiment, the temperatures on the vertical surface and in the ambient water are controlled at tw=40oC and t*=20oC and tw=60oC and t*=20oC, respectively. The laser Doppler velocimeter is employed using a technique of frequency deviation shift so that it can accurately measure a smaller velocity field of a fluid, such as the velocity of water free convection. For each temperature condition the velocity field wx is measured at heights of 0.05, 0.10, 0.15, and 0.20m. For comparison of the measured results with calculated values, corresponding numerical calculations considering variable thermophysical properties are carried out. By the use of similarity variables, the numerical solutions are transformed to the corresponding dimensionless values, and the experimental data are transformed to the associated dimensionless velocities. The experimental data and the numerical solutions of the velocity field are listed in the tables and plotted in figures. A very good agreement between the measured and calculated values is observed.

Key words:

free convection, laminar boundary layer, laser Doppler velocimetry, vertical plate.

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4.

NONLINEAR TRANSIENT ANALYSIS OF POINT RUB EFFECTS
IN A FLEXIBLE ROTOR

C.C. LEE,

Consulting Design Engineer
Solar Turbines, Inc.
SAN DIEGO, CA

P.E. ALLAIRE,
Wade Professor
Mechanical, Aerospace and Nuclear Engineering
University of Virginia
Charlottesville, VA 22901

     Rubs occur in industrial rotating machinery in common practice. However, the vibration spectrum produced by different rub conditions is very different and not always easy to interpret. This paper presents a nonlinear analysis of a single mass rotor subject to a point rub with dry friction (Coulomb damping) and compares the results to experimental data. Experimentally, subsynchronous vibrations occur at whirl ratios of 1/N(N=2,3,4...) relative to operating speed with shaft orbits of complicated Lissajous shapes. These results have not been fully explained in the literature. A point rub dry friction model is used, different from previous authors. The nonlinear point rub transient analysis used numerical integration of the equations of motion forward in time to determine the rotor response. The results obtained matched the experimental results relatively well in terms of both whirl ratios of 1/N and the Lissajous shapes. Shaft orbits were found to be a mix of forward and backward precession, rather than the strictly backward whirl often cited in the literature for rubs. Orbit frequency spectrums were found using a Fast Fourier transform numerical algorithm. At the whirl ratio of 1/3, the analysis showed that the rotor only hit the point rub during every two out of three shaft revolutions. It was also found that the rub friction coefficient had little effect on the nonlinear transient results for this rotor and rub model.

Key words:

dry friction, nonlinear analysis, point rub, single mass rotor.

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5.

EFFECTS OF LOW-CALCIUM FLY ASH ON
THE RHEOLOGY OF FRESH CEMENT PASTES

Stefania GRZESZCZYK and Grzegorz LIPOWSKI

Technical University of Opole,
45-233 Opole, ul. St. Mikolajczyka 5, POLAND

     Results of the effect of fly ash upon rheological properties of cement pastes have been presented. Bituminous fly ash when added to cement have been found to produce a decrease both in the yield shear stress value and plastic viscosity of cement pastes the greater the higher the fly ash content. A relation between the fine fraction share in the fly ash and the flowability degree of cement pastes was found. The fine fraction content of the fly ash has been proved to be a better parameter to evaluate the influence of the fineness upon the rheology of cement pastes than Blain's specific surface area is.

Key words:

rheology, cement paste, fly ash.

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6.

EVALUATION OF INTERLAMINAR SHEAR STRESSES
IN A FIBER-REINFORCED LAMINATED BEAM BY THE IFRM THEORY

Michio KURASHIGE and Kazunari YAMAMOTO

Iwate University,
Department of Mechanical Engineering
Ueda 4-3-5, Morioka 020-8551, JAPAN

Kazumi WATANABE
Yamagata University,
Department of Mechanical Engineering
Johnan 4-3-16, Yonezawa 992, JAPAN

     By using the linear IFRM theory, interlaminar shear stresses are estimated for a fiber-reinforced laminated beam subjected to a line force. The analysis for this estimation is fully three-dimensional. The beam has three layers. Its core is reinforced in the width direction, whereas its skins in the longitudinal direction. The skins are also assumed to have infinitesimal thickness for the sake of analytical simplicity. In spite of this assumption, inextensibility of the skin layers is valid, since the IFRM theory postulates that the materials are completely inextensible in fiber directions. The analytical results explain very well the observations of delamination shapes and justify applicability of various beam theories to the theoretical analysis of the observations in beam impact tests by use of a line nose impactor. It is also shown that the IFRM theory can explain the observed slight deviation of the delamination from the interface at its early stage.

Key words:

IFRM theory, fiber-reinforced beam, interlaminar shear stress, impact test, delamination

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7.

TWO COLLINEAR GRIFFITH CRACKS IN
AN ORTHOTROPIC STRIP WITH PUNCHES

P.C. SINGH

Department of Mathematics
College of Textile Technology
Serampore - 712201, W.B. INDIA

B. PATRA
Department of Mathematics
Bengal Engineering College (D.U.)
Howrah - 711 103, W.B. INDIA

T.N. MAULIK
Technical Teachers Training Institute
Block-FC, Sector-III
Salt Like City, Calcutta - 700091, W.B. INDIA

     Integral transform technique is employed to solve the elastodynamic problem of steady-state propagation of two symmetrically situated identical collinear Griffith cracks along the mid plane of orthotropic strip of finite thickness 2h with centrally situated moving punches along the boundaries of the layer. The problem is reduced to the solution to a pair of simultaneous singular integral equations with Cauchy type singularities which have finally been solved through finite Hilbert transform technique. For large h, analytical expressions for the local stress field near the crack tip and the stress intensity factors are obtained. Graphical plots of the numerical results are also presented.

Key words:

Griffith crack, punch, singular integral equation, stress intensity factor, orthotropic material, Yoffe model, Mach number, subsonic propagation, local stress field.

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8.

NUMERICAL COMPUTATION OF VISCOUS FLOW
FIELD PAST CIRCULAR CYLINDER

Gorachand LAYEK

Physics and Applied Mathematics Unit
Indian Statistical Institute
203, B. T. Road, Calcutta--700 035, India

     Incompressible viscous flow past a circular cylinder has been studied numerically in this work, under laminar conditions. A control-volume based finite-difference scheme in a staggered grid has been used to solve unsteady Navier-Stokes equations in body-fitted orthogonal co-ordinates. The farfield boundary has been mapped into a finite one. The pressure Poisson equation and pressure-velocity correction formulae have been derived. The convergence value achieves the level of 0.5*10-5 after a few iterations. It is noted that secondary eddies appear periodically at higher Reynolds numbers. The results are compared with available experimental data and it is found that important quantities like Strouhal numbers, drag coefficients and separation angles match well with established values.

Key words:

Staggered grid, secondary eddy, pressure Poison equation, pressure-velocity corrections.

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9.

MODELLING OF SOLUTE MIGRATION AND
ITS ADSORPTION IN POROUS LAYERS

S. WROŃSKI, E. MOLGA, L. RUDNIAK and R. HUBACZ

Department of Chemical and Process Engineering,
Warsaw University of Technology
ul. Waryńskiego 1, 00-645 Warszawa, POLAND

     The immobilization of pollutants by irreversible sorption in agglomerates immersed directly into the porous layer has been considered. A general model for migration and sorption of soluble contaminants in a porous layer has been formulated and the method of its solution has been proposed. The calculations have been carried out to display the model effectiveness and flexibility. The influence of the size of agglomerates, the density and geometry of their distribution on the decontamination efficiency has been studied. Also the effect of mass transfer parameters on this efficiency has been investigated.

Key words:

soil decontamination, sorption agglomerates, migration of pollutants

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10.

HOT-WIRE ANEMOMETER WITH THE MODULATED OVERHEATING RATIO - AN INSTRUMENT FOR MEASURING NON-ISOTHERMAL FLOWS

Jan KIEŁBASA

Strata Mechanics Research Institute
Polish Academy of Sciences - CRACOW

     The paper presents the method for simultaneous measurements of flow velocity and the temperature of the medium, using a single wire probe operating in a constant-temperature system wherein the overheating ratio undergoes sine modulations. Theoretical bases for these measurements are presented here together with some examples of velocity and temperature distribution patterns in the temperature and velocity wake formed behind the hot wire used to provide a test environment for the proposed scheme.

Key words:

hot-wire anemometer, non-isothermal flow, velocity and temperature measurement

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