Issue 3

JTAM, Sofia, vol. 19 Issue 3 (1988)


St. Radev
Inst. Mech. Biomech., Bulg. Acad. Sci., Acad. G. Bonchev Str., Bl. 8, Sofia 1113, Bulgaria

JTAM, Sofia, vol. 19 Issue 3 pp. 013-013 (1988), [Full Article]

Governing the Structure of Clusters Nucleated in Supersonic Flow

L.S. Bartel, L. Harsanyi
Dept. of Chemistry University of Michigan Ann Arbor, Michigan, 48109 USA

Research at the University of Michigan has shown that one can exercise a significant degree of control over the size and structure of clusters nucleated in supersonic flow. Depending upon the initial temperature, pressure, carrier gas and nozzle design, a given vapor can sometimes be induced to condense to either supercooled liquid clusters or to solid. In the case of solid clusters, the constituent molecules can sometimes be induced to pack in either of two (or sometimes more) distinctly different ordered lattices. Computer simulations of homogeneous nucleation and cluster growth provide useful clues to account for observations.

JTAM, Sofia, vol. 19 Issue 3 pp. 015-018 (1988), [Full Article]

Linearized Analysis of a One-speed BGK Model in the Case of Strong Condensation

C. Cercignani, A. Frezotti
Dipartimento di Matematira Politecnico di Milano Piazza Leonardo da Vinci 32 Milano, 20133 Italy

In this paper an analytical approach is proposed to the problem, based on the linearization of the solution of a one-dimensional B.G.K. model around the downstream equilibrium Maxwellian distribution function. The solution of the linearized equation is a poor approximation of the solution of the full nonlinear equation but nevertheless it retains some of the properties of the latter as far as the number of free parameters is concerned.

JTAM, Sofia, vol. 19 Issue 3 pp. 019-023 (1988), [Full Article]

Equilibrium Cluster-size Distribution in a Finite System

S.F. Chekmarev
The USSR Academy of Sciences - Syberian Branch, Inst. of Thermophysics, Novosibirsk, 630090 USSR

An equilibrium cluster size distribution in a finite system is studied by using the Mayer cluster-expansion formalism. The mean cluster-size distribution function is compared with computer results obtained by Rao, Berne and Kalos and shows quite a good agreement.

JTAM, Sofia, vol. 19 Issue 3 pp. 024-031 (1988), [Full Article]

Kinetic Theory Based on New Upwind Methods for Inviscid Compressible Flows

S.M. Deshpande, J.C. Mandal
Dept. Aerospace Engineering, Indian Institute of Sciences, Bangalore, 560012 India

A new class of Boltzmann equation based on upwind methods, called Kinetic Numerical Method (KNM) and Kinetic Flux Vector Splitting Method (KFVS), have been developed using the well-known fact that the Euler equations of gas dynamics are the moments of the Boltzmann equation when the distribution function is a Maxwellian one. Various schemes of solution have been applied to the test case of one-dimensional shock propagation problem and results show their ability in obtaining accurate wiggle free solutions.

JTAM, Sofia, vol. 19 Issue 3 pp. 032-038 (1988), [Full Article]

On the Solar Wind – Comet Plasma Interactions

I. Mastikov, M. Kartalev
Inst. Mech. Biomech., Bulg. Acad. Sci., Acad. G. Bonchev Str., Bl. 8, Sofia 1113, Bulgaria

The paper discusses a generalization of the MHD approach, when simulating the solar wind — cosmic plasma interaction. Unlike the models known in literature and the Ohm's law, the authors account for the comet ion loading effect. Thus, new terms appear in the magnetic induction equation and in the Rankin-Hugoniot relationships on discontinuities. On the basis of such a model, the authors give an interpretation of the discontinuity surfaces, registered by the space crafts VEGA and GIOTTO. An essentially new interpretation of these surfaces is proposed.

JTAM, Sofia, vol. 19 Issue 3 pp. 039-045 (1988), [Full Article]

Entropy Production, Heat and Mass Transfer in Aerosol Flows

H. Lang
Max-Plank-Inslitut für Stroemungsforschung, Bunsenstr. 10, Goettingen, D-3400

The entropy produced by the transfer of heat and mass between droplets and vapor is calculated for an aerosol flow. Assuming a near equilibrium situation, general relationships are given for the heat and mass transfer between droplets and the vapor, using irreversible thermodynamics. The general results are demonstrated by considering an aerosol containing two chemical species.

JTAM, Sofia, vol. 19 Issue 3 pp. 046-050 (1988), [Full Article]

Rarefied Gas Flow during Evaporation and Filtration in High-Porous Media

V.G. Leitsina, V.V. Levdanski, N.V. Pavlyukevich
The Luikov Heat and Mass Transfer Institute, Byelorussian Academy of Sciences, 15 P. Brovka Str., Minsk, 229728 USSR

Boundary-value problems of the kinetic theory of gases, which describe evaporation from a hurried phase boundary and filtration in a high-porous layer, are solved. The dusty gas model is used. In the equation for the distribution function of gas molecules, the collision integral is replaced by an effective external force. Expressions for the rates of evaporation and filtration, applicable in the entire range of Knudsen numbers, are given.

JTAM, Sofia, vol. 19 Issue 3 pp. 051-055 (1988), [Full Article]

Inelastic Scattering and Sticking of Light Particles on Surfaces

J.R. Manson1, G. Armand2
1Clemson University, Dept. Physics and Astronomy, Clemson, S.C., 29631 USA
2Centre d’Etudes Nucléaires de SaclayService de Physique des Atomes et des Surfaces, Gif sur Yvette, France

The report presents a general theory for the inelastic surface scattering of light particles at thermal energies. This theory can be used to obtain inelastic differential reflection coefficients for scattered particles, the thermal attenuation of elastic difraction intensities, and the capture and sticking probabilities for adsorption by the surface bound states.

JTAM, Sofia, vol. 19 Issue 3 pp. 056-056 (1988), [Full Article]

On Some Features of Electron Beam Evaporation

G. Mladenov, T. Dyakov, M. Kardjiev
Inst. of Electronics, Bulg. Acad. Sci., 76 Lenin Blvd., Sofia, 1184 Bulgaria

Results of experimental investigation on electron beam evaporation with different electron beam power densities are reported. The analysis of experimental data has shown that some very important characteristics of vapour streams of evaporated material can be con-Dolled by observing the charged particle current, collected by the electron probe. Some peculiarities of the spatial distribution of the steam density in the vacuum chamber may be explained by the change of the surface shape due to the electron beam action. On the basis of the proposed model some conditions for the efficiency of electron beam evaporation are prescribed.

JTAM, Sofia, vol. 19 Issue 3 pp. 057-059 (1988), [Full Article]

Vapor Flow in a Vacuum Vapor-Deposition Chamber

K. Nanbu
Inst. High Speed Mechanics. Tohoku University, Katahira 2-1-1, Sendai, 980 Japan

Two-dimensional rarefield flows in a vacuum vapor-deposition chamber are explained by use of the direct simulation Monte Carlo method. The vapor evaporated from a crucible expands into the evacuated chamber and is deposited into a film at the upper wall. The effects of the flow structure on the Knudsen number, the deposition probability and the size and location of the crucible are examined.

JTAM, Sofia, vol. 19 Issue 3 pp. 060-065 (1988), [Full Article]

Monte Carlo Simulation Method for Solving Gas Dynamics Kinetic Problems

N.A. Nurlibaev, V.E. Yanitski
Computing Centre of the USSR Acad. Sci., 40 Vavilov Str., Moscow, 117333 USSR

The paper reviews statistical methods for calculating non-equilibrium relaxation processes and transfer in a compound gas mixture, these methods being developed at the Computing Centre of the USSR Academy of Sciences. They are in particular applied to the numerical study of kinetic condensation and evaporation, as well as to non-equilibrium chemical reactions.

JTAM, Sofia, vol. 19 Issue 3 pp. 066-069 (1988), [Full Article]

Monte Carlo Simulation of the Vapour-Gas Flow Between Two Coaxial Cylinders

St. Radev, St. Stefanov
Inst. Mech. Biomech., Bulg. Acad. Sci., Acad. G. Bonchev Str., Bl. 8, Sofia 1113, Bulgaria

Vapor flow between two coaxial cylinders and in the presence of a neutral gas is investigated by employing the method of direct statistical simulation. The flow model is created by using a uniform orthogonal grid and by dividing the first quadrant of the Cartesian coordinate system. The flow macroparameters are given in a cylindrical coordinate system. The problem is solved for moderate Knudsen numbers.

JTAM, Sofia, vol. 19 Issue 3 pp. 070-077 (1988), [Full Article]

Dendritic Pattern Formation

Y. Saito1, G. Goldbeck-Wood2, H. Müller-Krumbhaar3
1Dept. Chemistry, Faculty of Science and Technology, Keio University, 3-1 4-1 Hiyoshi, Kohoku-ku, Yokohama 223, Japan
2Institut für Festkorperforschung der Kernforschungsanlage Jülich, Jülich D-5170, Postfach 1913

An extended abstract is presented of a work on the numerical study of dendritic crystal growth in the case when the crystallization front moves into a super-cooled or super-saturated region. Under these conditions the dendrites are approximately parabolic needle crystals with tree-like side branches. The numerical results give the first confirmation of the validity of some recent analytical predictions about the role of the crystal anisotropy.

JTAM, Sofia, vol. 19 Issue 3 pp. 078-080 (1988), [Full Article]

Equations of Two-Velocity Two-Temperature Gasdynamics of Gas Mixtures

M.Sh. Shavaliev
The USSR Acad. Sci. - Sibernian Branch, Inst. of Theoret. Appl. Mechanics, Novosibirsk, 630090 USSR

The equations of Navier-Stokes and Burnet levels for the two-velocity and two-temperature gas dynamics of monoatomic gas mixtures are derived in the paper. For this purpose the system of moment equations for the two-velocity and two-temperature mixtures, corresponding to 13 moments approximation in one-component gas, is used.

JTAM, Sofia, vol. 19 Issue 3 pp. 081-088 (1988), [Full Article]

Strong Evaporation and Condensation on a Plane Condensed Phase

Y. Sone, K. Aoki, T. Yamada, H. Sugimoto
Dept. Aeronautical Engineering, Kyoto University, Kyoto, 606 Japan

Steady evaporation and condensation of a gas on its plane condensed phase is studied numerically on the basis of the kinetic theory. Investigating the time development of solutions of the initial and boundary value problem of the kinetic equation in the semi-infinite domain for various initial and boundary data, the authors look for possible steady solutions, and examining these in detail, they determine the steady solution.

JTAM, Sofia, vol. 19 Issue 3 pp. 089-093 (1988), [Full Article]

A Kinetic Model of Gas-Solids Suspensions with Vapourizing Particles

V.A. Tsibarov
Leningrad University, Faculty of Mathematics and Mechanics, Petrodvorets, 2 Bibliotechnaya Sq., Leningrad, 198904 USSR

The paper presents a flow model of a gas-solid suspension, employing the methods of gas kinetic theory and considering physical and chemical changes and evaporation phenomena. The kinetic equations of a weakly unequilibrium flow are solved at different rates of development of the physical and chemical processes and for different relations between the Foker-Plank and the colliding operator.

JTAM, Sofia, vol. 19 Issue 3 pp. 094-098 (1988), [Full Article]

Dusty Knudsen Layers in Cometary Gas Dynamics

T. Ytrehus, E. Gjernes
The Norwegian Institute of Technology, Div. Applied Mech., 7034 Trondheim - NTH, Norway

The Knudsen layer problem for strong evaporation in the presence of solid particles is considered, using a moment solution of the Boltzmann equation. Effects of particle mass flux and temperature upon the macroscopic flow parameters are identified under conditions relevant to cometary gas dynamics.

JTAM, Sofia, vol. 19 Issue 3 pp. 099-104 (1988), [Full Article]