Abstracts of papers for

Previous issue vol. 46, no. 4 (2005)

vol. 47, no. 1 (2006)

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Contents of issue 1, vol. 47

1. Professor Zbigniew Dżygadło: In memoriam
2. M. Ezzat, M. Zakaria, A. Samaan, A. Abd-El Bary: Free convection effects on a perfectly conducting couple stress fluid
3. M. Milanese, J. Pouzo, R. Moroso, H. Acuña: Staged Z-pinch experiment in a small device
4. J. Wojnar, R. Wojnar: On the Smoluchowski flow in zeta-potential
5. B. Sharma, M. Agarwal,R.C. Chaudhary: MHD fluctuating free convective flow with radiation embedded in porous medium having variable permeability and heat source/sink

Professor Zbigniew Dżygadło: In memoriam

On March 21st 2005, we have lost our distinguished colleague Prof. Zbigniew Dżygadło. For many years, he participated in the Editorial Board and he was elected the Editor-in-Chief of our journal.

He has devoted all his life to the educational and scientific activities, mainly on behalf of the Military University of Technology in Warsaw. He graduated the MUT in 1953 and started the fruitful career as a university teacher and scientific researcher. He got His doctor's degree and professor title there. He was the teacher of hundreds of aviation engineers, he had promoted 25 pupils to doctor's degree. Many of them obtained the professor titles. He should be considered a founder of the school of aero-elasticity research. He shaped his younger colleagues to keep to the straight and narrow.

His main scientific achievements are placed in linear and non-linear vibrations of mechanical systems and aero-elasticity. He is the author or co-author of over 200 scientific papers, three scientific books about vibrations and aviation, and 2 textbooks. He had managed many projects useful for the aviation industry.

He was the member of many scientific committees in the universities and in the Polish Academy of Sciences. He was a member of the Polish Society of Theoretical and Applied Mechanics, and was elected the Chairman of the Society. He had been also the Chairman of the Polish Institute of Aviation, and he performed many managerial functions in the MUT.

His activities were well recognised by his colleagues and superiors. He was honoured by several state decorations and awards.

We have lost a good and honest Colleague and Teacher.

Contents

M. Ezzat, M. Zakaria, A. Samaan, A. Abd-El Bary: Free convection effects on a perfectly conducting couple stress fluid

We have introduced a magnetohydrodynamic model of boundary-layer equations for a perfectly conducting couple-stress fluid. This model is applied to study the effects of free convection currents with thermal relaxation on the flow of a polar fluid through a porous medium, which is bounded by a vertical plane surface. The state space formulation developed in Ezzat [1] and [2] is introduced. The formulation is valid for problems with or without heat sources. The resulting formulation, together with the Laplace transform technique, are applied to a variety of problems. The solution to a thermal shock problem and to the problem of the flow in the whole space with a plane distribution of heat sources are obtained. It is also applied to a semispace problem with a plane distribution of heat sources located inside the fluid. A numerical method is employed for the inversion of the Laplace transforms.

The effects of Grashof number, material parameters, Alfven velocity, relaxation time, Prandtl number and the permeability parameter on the velocity, the temperature and the angular velocity distributions are discussed. The effects of cooling and heating of a couple-stress fluid have also been discussed. Numerical results are given and illustrated graphically for the problems considered.

Contents

M. Milanese, J. Pouzo, R. Moroso, H. Acuña: Staged Z-pinch experiment in a small device

A simple device based in a small Z-pinch is designed, constructed and then used for evaporating and compressing a metallic exploding wire by a cylindrical plasma shell of hydrogen or argon. Time-resolved local current derivative is measured in two different points of the plasma path and the dynamic evolution of the shell, and the compression of the metallic plasma wire is studied. This study is made by varying the wire diameter and the gas filling pressure. A more effective compression is reached by using argon for the shell imploding and copper for the exploding wire stages, respectively.

Contents

J. Wojnar, R. Wojnar: On the Smoluchowski flow in zeta-potential

Two-scale expansion of functions describing stationary incompressible flow in electric field is used at first to recover the Smoluchowski formula for electrolyte incompressible flow, conditioned by zeta-potential of electric double layer (EDL) and to observe that the pressure is not constant along the depth of the EDL. Next, the analogous formula for non-incompressible electrolytes is derived.

Contents

B. Sharma, M. Agarwal,R.C. Chaudhary: MHD fluctuating free convective flow with radiation embedded in porous medium having variable permeability and heat source/sink

The study of free convective two-dimensional unsteady flow with radiation through a porous medium of variable permeability and transverse magnetic field in presence of a heat source/sink, bounded by an infinite vertical porous plate with uniform suction, has been made. The permeability of a porous medium fluctuates with time about a constant mean. Approximate solutions for velocity, temperature and skin friction are obtained and the effects of heat source/sink, radiation, variable permeability, Prandtl number and magnetic field parameter on velocity, temperature and skin friction are shown and discussed with the help of graphs and a table.

Contents