The vapour explosion is a violent explosive phenomenon which may occur when two kinds of liquid of different temperature contact suddenly. Analysis of this phenomenon is needed in terms of safety evaluation of nuclear reactors, examination of volcanic eruptions and assurance of safety of various industrial processes. We have developed a simulation method applicable to coarse mixing of the vapour explosion. This process, including complex thermo-hydrodynamics, requires handling of multi-phase and multi-component. We employed CHAMPAGNE which is a general-purpose multi-phase flow code and modified it make it suitable for the analysis of the vapour explosion. Specifically, we improved interfacial heat transfer models and incorporated compensation for numerical dilution of the dispersed liquid. After some model calculations we simulated the MIXA experiment done at Winfrith. Details of the code modification and the simulation results are presented in this paper.

The operator splitting algorithm has been applied in FEM analysis of fluid flow and heat transfer to improve the computational efficiency through the use of the optimum FEM models and the optimum solvers independently for convection and diffusion. The need for decoupling convection and diffusion operators in FEM calculations comes from the behavioural error analysis, where conditions have been studied for a proper representation of major physical features of the convective-diffusive transport phenomenon on a coarse grid. The accuracy and efficiency of the algorithm have been verified by solving two pertinent benchmark problems of recirculating flow and free convection. The results obtained show that solutions of both equal- and unequal-order FEM interpolations are free from wiggles and spurious pressure modes and they fit fairly well the results reported elsewhere.

A new, original numerical method of free particles, for mechanics of continuous media, has been developed. The free particle hydrocodes (HEFP), based on this method, are the powerful tools that can be used to simulate, in the sense of computational physics, events with very high dynamic effects. In the paper, computational simulation of several attractive and practically important problems like: processes of the detonation, high velocity impacts and hypervelocity planetary impacts, shaped charge jet formation, explosive forming of projectiles, penetrating of the armour plate, is posed. All of them include shocks, very large deformations of solids, processes of cratering with impact jets generation and targets penetration. The method of free particles is a very useful for magnetohydrodynamical (MHD) simulation, too. It is possible to simulate ideal MHD and non-ideal MHD processes, and such exemplary results are also presented. In the paper, physical, mathematical and numerical models as well as results of some complex, unsteady, spatially two-dimensional simulations are presented.

A new type of the externally heated engine is the subject of the present paper. Air can be used as a working medium of the engine. Heat delivered to the working air may come from a combustion chamber or another heat generator of an arbitrary type. The engine construction and the thermodynamic cycle performed by the engine are original ones. The engine operation has been investigated basing on the presented computer simulation. As a result, the time-dependent pressures and temperatures in each part of the engine have been determined. The engine power and efficiency have also been calculated. When the lowest basic pressure of the engine cycle is equal to 1 MPa, the power of 30 kW per 1 liter of the cylinder volume and the efficiency 0.38 at 1500 rev/min can be achieved. The main aim of this paper is to present a numerical investigation of the engine operation for higher values of the basic cycle pressures. It has been shown that for the pressure equal to 3 MPa, the power of about 100 kW per 1 liter and the efficiency 0.40 at 1500 rev/min can be theoretically obtained. The mechanical losses of the engine are not taken into account during the power and efficiency calculations.

The problem of dislocation motion in monocrystals is faced in the framework of the continuum theory of dislocations. The presented approach is based on the defects balance law. A constitutive model is formulated which relates the driving forces with the dislocation velocity. The model makes use of the relations between the plastic deformation tensor and the tensor of dislocation density. Given a crystal under certain boundary and initial conditions, the evolution of both dislocation field and elastic-plastic deformations is obtained by solving the coupled system of equations resulting from the equilibrium equation and the dislocation balance for each time step. The set of equations is discretized by the finite element method. As an example the movement of an edge dislocation field inducing shear band deformation in a monocrystal is considered.

The paper presents the method of algebraic vorticity moments. It may be used to solve problems of viscous liquid motion in 2-D and 3-D cases. Its essence lies in the integration of a set of ordinary differential equations. The unknown functions of those equations defined as ${1 \over m!n!} \int_{E_2} {\omega{x^m}{y^n}\d x\d y}$ allow to find the vorticity field and next the velocity. We also show a number of 2D numerical examples.