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Statistical analysis of the results of molecular dynamics (MD) calculation of gas-phase “self-assembling” of nanoclusters during metal vapor condensation revealed the laws of energy transfer between metallic clusters and inert gas atoms. A model is proposed to determine the parameters of heat exchange between clusters and the environment at the initial stage of condensation. This model is based on averaged MD data on the interaction between small clusters and argon atoms. The parameters that can be used to transfer information from MD to a macroscopic condensation model are numerically determined. The results obtained can be used to describe nucleation to predict a nanoparticle size distribution in the production of metallic powders.

The results of the molecular-dynamic calculations of gas-phase nanocluster “self-assembly” during metal vapor condensation have been statistically analyzed parting terms of a computational scheme suitable for describing condensation. The laws of collisions and the growth of small copper clusters are revealed. The parameters that describe the interaction between clusters and metal atoms and are used to transfer information to a macroscopic nucleation model are determined. The results can be used for describing nucleation for predicting a nanoparticle size distribution in the production of metal nanopowders.

A statistical analysis of the results of molecular-dynamic calculations of metal (Cu or Ti) vapor condensation in an inert gas (Ar) medium has been performed. Condensation proceeds with the formation of small particles consisting of metal atoms—clusters. The internal energy of the metal cluster—the sum of the kinetic energy of the atoms in the center of mass system and potential energy—is chosen as the key characteristic describing its state. It is shown that the internal energy value gives the possibility for the prediction of the duration of the cluster existence, from birth to decay, i.e., it describes the ability of the cluster to grow. The temporal evolution of the distribution function of the clusters over the internal energy values is presented.

A molecular dynamics study was carried out on the dependence of the radii of small metal clusters that form in the process of gas-phase copper condensation on the number of atoms in them. The radii are calculated with the molecular-kinetic theory formulas from molecular-dynamic simulating data on the number of collisions between clusters. It was found that the dependence of the radii on the number of particles has a form close to the classical n1/3. However, the average cluster radii are about 40% larger than the case in which the cluster is considered a drop of a bulk fluid.

A computing scheme for a mesoscopic description of a nucleation process has been built using a statistical analysis of the results of molecular dynamics simulation of a supersaturated metallic vapor. The parameters that enter into equations for cluster growth rate and heat release during condensation are found by a direct statistical computation in a molecular dynamics method. The rates of cluster formation calculated by a molecular dynamics method agree well with the numerical model developed in this work.

The phenomenon of evaporation from the surface of a liquid droplet into a neutral noncondensible gas was numerically studied by taking forced convection gaseous flow into account. The mathematical model considers the effects of surface tension, gravitational force, viscosity of both liquid and gaseous media, as well as the Stefan flow from the droplet surface, possible free gravitational convection, and the Marangoni convection in droplets, and it is designed to describe diffusion-limited evaporation. We consider the diffusion-limited evaporation process when the diffusive gas flux to the droplet surface is compensated by the convective Stefan flow from the surface. The results indicate an interaction of the liquid and gaseous media. Convective gas flows cause the liquid to move and a vortex to occur in the droplet. The flow velocities in a vortex are 103 times less than the characteristic velocity of forced convection flow in air. The droplet surrounded by gaseous flow changes its shape and oscillates, which causes a gas-density wave. Calculations have shown that the diffusion-limited evaporation rate does not change in the presence of forced convection, which contradicts most of the known experimental works. The possible reason for this discrepancy is the presence of non-equilibrium conditions at the liquid–gas interface in experiments. This leads to a consequent change of the evaporation mode to non-diffusive, while the numerical model postulates the Stefan condition and diffusion-limited evaporation.

We discuss the problem of dimer formation during the homogeneous nucleation of atomic metal vapor in an inert gas environment. We simulated nucleation with molecular dynamics and carried out the statistical analysis of double- and triple-atomic collisions as the two ways of long-lived diatomic complex formation. Close pair of atoms with lifetime greater than the mean time interval between atom–atom collisions is called a long-lived diatomic complex. We found that double- and triple-atomic collisions gave approximately the same probabilities of long-lived diatomic complex formation, but internal energy of the resulted state was essentially lower in the second case. Some diatomic complexes formed in three-particle collisions are stable enough to be a critical nucleus.

Statistical analysis of the results of molecular-dynamic modeling for nucleation of metal (Cu) vapors in inert gas atmosphere (Ar) is carried out. Features of the initial stage of nucleation are considered for estimation of the probability of the growth of small atomic clusters within a supersaturated nonequilibrium medium and the efficiency of heat removal from them during collisions with inert gas atoms and other metal atoms.

The efficiency of the vapor phase condensation of metallic nanoclusters and nanopowders is determined by setting optimum process parameters, the possibilities of experimental estimation of which is limited. In this work, mathematical and physical models are developed to perform computer analysis of the vapor phase condensation to describe the macroscopic characteristics of the process (temperature regime, gas mixture dynamics, diffusion and convective transport of clusters) with allowance for the properties of the components on a microscopic level.

The results of a numerical solution of the problem of vibrations of a torsion viscosimeter filled with an incompressible viscoplastic liquid are presented. It has been shown that in the vicinity of the rotation axis there appears a dead zone, whose boundary changes in the process of vibrations. The influence of plastic properties of the liquid on the characteristics of viscosimeter vibrations has been determined. A method for identifying viscoplastic properties by the observed parameters of vibrations is proposed.

The condensation of metal vapor in an inert gas is studied by the molecular dynamics method. Two condensation regimes are investigated: with maintenance of partial pressure of the metal vapor and with a fixed number of metal atoms in the system. The main focus is the study of the cluster energy distribution over the degrees of freedom and mechanisms of the establishment of thermal equilibrium. It is shown that the internal temperature of a cluster considerably exceeds the buffer gas temperature and the thermal balance is established for a time considerably exceeding the nucleation time. It is found that, when the metal vapor concentration exceeds 0.1 of the argon concentration, the growth of clusters with the highest possible internal energy occurs, the condensation rate being determined only by the rate of heat removal from clusters. © 2012 Pleiades Publishing, Ltd.

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The problem of decaying rotation of a disk floating on the surface of a viscoelastic fluid in a cylindrical container is solved by numerical methods. The motion is found to have the form of decaying oscillations observed previously for water. In addition to the viscosity coefficient, the constructed mathematical model of the viscoelastic fluid has two more independent parameters: shear modulus and time of relaxation of elastic stresses. Elastic parameters of water are determined through comparisons with experimental data. © Springer Science+Business Media, Inc. 2008.

Metal melts have such conductivity, that magneto-hydrodynamic effects can be easily observed even in moderate magnetic fields (around 0.01T) under conditions achieved in conventional physicochemical experiments. This fact gives an opportunity to create new methods of analyzing metal melts properties. Current work represents the experiments with the oscillating cup viscometer placed in the uniform steady longitudinal magnetic field. The oscillation' parameters dependencies on magnetic induction of the applied magnetic field have been measured. To record the motion of the viscometer the new optical scheme, which allows writing down quasi-continuously viscometer's angle position, has been implemented. Estimation of oscillation' parameters values (oscillation' decrement and period) has been evaluated with the aid of wavelet analysis and optimization methods. Field dependences of oscillation' parameters were being used for liquid gallium viscosity and electrical conductivity determination with the help of the viscosimetric theory, that was earlier suggested by us. © 2008 IOP Publishing Ltd.

The behavior of a liquid drop constrained between two rigid plates is studied. The problem is solved numerically in the following cases: (1) the free oscillations of the drop when the plates are motionless; (2) the forced oscillations when the upper plate makes a translational vibration in the normal direction. The possibility of viscosity and surface tension determination in such experiments is shown. © 2007 IOP Publishing Ltd.

The results of numerical solution of the problem on flow of an incompressible viscoplastic fluid in the gap between two rotating cylinders have been presented. The criterion of formation of the boundaries of stagnant zones has been developed. A comparison of the results of numerical calculations to the analytical solution has been made. The time of establishment of stationary flow in the gap has been determined. © Springer Science+Business Media, Inc. 2007.

Forced linear oscillations of a viscous drop placed on a horizontal surface vibrating in perpendicular direction are investigated. The problem is solved for two cases: (1) constant contact angle, and (2) pinned contact line. Phase-frequency and amplitude-frequency characteristics of oscillations of the drop apex are found for the first axisymmetrical mode of oscillations. The independence of the difference of oscillation phases of the drop apex and the substrate on fluid density, viscosity, surface tension, and drop size as well as on presence or absence of the gravity force was demonstrated.

The open system consisting of a sessile drop, a neutral gas, and a substrate is analyzed by numerical methods. The mode with constant contact angle is considered. The model takes into account evaporation from drop surface, free and forced convection in gas, buoyancy, and Marangoni effect in the liquid phase. It was established that every considered mechanical and thermodynamical disturbance of the system leads to the drop surface oscillations, and thus a drop in an open air oscillates almost inevitably. The displacement of the liquid-gas interface due to oscillations is analyzed in terms of its impact on the accuracy of measurement of the surface tension by sessile drop method.