
Professor Zbigniew Dżygadło:
In memoriam

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

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

J. Wojnar, R. Wojnar:
On the Smoluchowski flow in zetapotential

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 EditorinChief 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 aeroelasticity research. He shaped his
younger colleagues to keep to the straight and narrow.
 His main scientific achievements are placed in linear and nonlinear vibrations
of mechanical systems and aeroelasticity. He is the author or coauthor 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. AbdEl Bary:
Free convection effects on a perfectly conducting couple stress fluid

We have introduced a magnetohydrodynamic model of boundarylayer equations for a perfectly
conducting couplestress 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 couplestress
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 Zpinch experiment in a small device

A simple device based in a small Zpinch is designed, constructed and then used for
evaporating and compressing a metallic exploding wire by a cylindrical plasma shell of hydrogen
or argon. Timeresolved 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 zetapotential

Twoscale 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 zetapotential 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
nonincompressible 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 twodimensional 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
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