The effect of the internal heat generation on the free convection from a vertical flat plate embedded in a porous medium saturated with the non-Newtonian 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.

     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 non-dimensional form. These equations are then transformed into a set of nonsimilar boundary layers, which are solved numerically using a very efficient implicit finite-difference method known as the Keller-box 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.

     Rayleigh-Taylor instability of Walters' B' elastico-viscous 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.

     The problem of propagation of shock waves in non-ideal 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.

     In the paper, a dynamic analysis of gas-lubricated 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.

     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.

     The problem of critical states and initial post-buckling equilibrium paths of thin-walled girders (beam-columns) built of plate and/or shell elements subjected to compression and bending has been solved. Plate and shell elements can be made of multi-layer orthotropic materials. The problem has been solved within the first order approximation of Koiter’s asymptotic theory, using the transition matrix method. The results of numerical calculations have been presented in the form of plots.

     The solutal analog of the Rayleigh-Benard convection in a reactive micropolar fluid is studied numerically using the Rayleigh-Ritz 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 non-reactive fluid system. The results have possible industrial applications.

     Past earthquakes (e.g., 1985 Mexico earthquake) have demonstrated the severe seismic vulnerability of asymmetric buildings due to coupled lateral-torsional 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 elasto-plastic or bilinear hysteresis behaviour for the structural load-resisting 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) elasto-plastic, b) stiffness degrading, c) strength deteriorating, and d) stiffness degrading as well as strength deteriorating hysteresis models for the load-resisting elements. These responses are expressed in terms of the maximum displacement demand and hysteretic energy demand in load-resisting 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.

     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 Brinkman-Forchheimer-extended 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.

     The unsteady motion of a dusty visco-elastic Maxwell type conducting fluid under arbitrary pressure gradient through a long uniform tube of rectangular cross-section is studied. Expressions for the velocities of the fluid and particle are obtained by using Laplace transform technique.

     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 Navier-Stokes 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, non-physical 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.

     A theoretical estimate is made to evaluate performance characteristics in terms of steady state and stability of two-layered externally pressurized porous gas journal bearings. Assuming only radial flow in the porous medium and considering two-dimensional flow in the bearing clearance, basic equations are solved to find load capacity and stability margin. It has been observed that a two-layered bearing gives higher stability when compared with a single-layered one.