Issue 1

JTAM, Sofia, vol. 24 Issue 1 (1993)

The 80-Anniversary of Academician G. Brankov

Editorial Board

JTAM, Sofia, vol. 24 Issue 1 pp. 009-010 (1993), [Full Article]

Dynamics of Multicomponent Systems Based on the Orthogonality Principle

G. Bojadziev1, L. Lilov2
1Institute of Mechanics, Bulgarian Academy of Sciences, Sofia
2University of Sofia

The subject of this work is to formulate evolutionary equations of complex systems with components of heterogeneous physical features. The energy as a general measurement for matter transfer together with the universal law of conservation of energy are assumed as a basis of the approach proposed here. The power flow and the power potential are taken as fundamental energy characteristics. An important feature of each system is its topology, which can be determined by a general energy graph, characterizing the energy alteration in the system. The state of the system is described by means of four groups of equations – flow, potential equations, equations of energy transformation and descriteration laws for each particular kind of energy. The system of equations thus obtained, give the principle of orthogonality which is the mathematical expression of the law of energy conservation.

JTAM, Sofia, vol. 24 Issue 1 pp. 011-026 (1993), [Full Article]

Augmented Lagrangians for General Optimal Control Problems

S. Grozdev
Institute of Mechanics, Bulgarian Academy of Sciences, Sofia

The paper is devoted to the Multiplier Method (known as Penalty Shifting Method or Augmented Lagrangian Method) independently introduced by Hestenes and Powell. It is considered an optimal control problem in a general form including state equations of elliptic, parabolic or hyperbolic types with final or distributed observations. An augmented Lagrangian is introduced and it is shown that its unconstrained minimization is equivalent to finding the saddle points of the ordinary Lagrangian function, which corresponds to the primal constrained problem.

JTAM, Sofia, vol. 24 Issue 1 pp. 027-032 (1993), [Full Article]

Analysis of Monte Carlo Data for a Model System of Adsorbed Diatomic Molecules

E. Litov, A. Genchev, J. Brankov
Institute of Mechanics, Bulgarian Academy of Sciences, Sofia

A simple statistical mechanical model of a monolayer of diatomic molecules adsorbed on a solid surface is considered. The presence of intermolecular interactions makes the problem of determining the macroscopic properties of the system unsolvable by analytical methods. Numerical data obtained by an approporate Monte Carlo simulation method for lattices of increasing size is analyzed in the light of finite-size scaling hypotheses corresponding to the three different types of the critical singularity which emerges in the limit of an infinite number of degrees of freedom.

JTAM, Sofia, vol. 24 Issue 1 pp. 033-045 (1993), [Full Article]

Experimental Investigations on Mechatronic System for Vibration Technological Processes

Al. Kazakoff
Institute of Mechanics, Bulgarian Academy of Sciences, Sofia

In this paper are presented the obtained results of series of experimental investigations on plane and space vibrations of a rigid body. The body is handled in space on elastic vibroisolators and can be concerned as one mass dynamic sysytem. One single disbalanced axle, mounted on the rigid body, rotated by an electric motor and a belt kinematic pair, creates mono frequency and poly frequency plane and space vibrations, due to the adjustement of the dynamic system using the non linear geometric linkages between the coordinates. A vibration machine model is constructed and produced, and series of experimental investigations con-firming the obtained theoretical results are carried out. Vibration movement is described by its quantitative and qualitative characteristics. Especially important are the qualitative characteristics, because they define the character of movement and confirm the existence of poly frequency space vibrations.

JTAM, Sofia, vol. 24 Issue 1 pp. 046-059 (1993), [Full Article]

The Axial Motion Effect on the Dynamic Response of a Vibrating Two-Span Beam, Supported on an Axially Vibrating Column

G. Michaltsos, D. Sophianopoulos
National Technical University, Athens, Greece

The dymanic behaviour of a two-span beam, acted upon by a moving load, including the longitudinal motion effect is considered. After determining the orthogonality condition for the beam, as well as its eigenf requencies and normal modes, one can easily establish the dynamic response of the beam. Dynamic and static influence lines of characteristic displacements and internal forces are assessed for two different velocities of the moving force. Comparisons between static and dynamic solutions indicate that the dynamic effect of the moving load may be considerable.

JTAM, Sofia, vol. 24 Issue 1 pp. 060-073 (1993), [Full Article]

Rationalization of the Calculation of Stresses in Deposits

V. Dundakov, C. Kouyumdjiev
Technical University of Rousse

The questions regarded in this work are connected with the application of a method for determining of stresses in deposits. The computations are reduced significantly by rationalization of the relationships for a particular case. The influence of deposits discretization upon the accuracy and the opportunities for well-founded neglecting of small values in the formulae are examined. Recommendations are given for using the obtained results in case of real data processing in the laboratory practice.

JTAM, Sofia, vol. 24 Issue 1 pp. 074-083 (1993), [Full Article]

Numerical Modelling of Gas-Liquid Flow

I. Bozdouganov1, Z. Zapryanov1, Yu. Buyevich2
1University of Sofia, Bulgaria
2University of Perm, Russia

In the present paper it is assumed that the bubble-liquid mixture can be considered within the framework of a model of two interacting and interpenetrating continuous media. For simplicity it is supposed that the continuous phase is an inviscid liquid. The model of inviscid liquid for continuous phase used describes the process of suspension motion qualitatively. It has been found out that the concentration of the bubbles influences strongly the velocity field due to the increasing of the quasi-Stokes force.

JTAM, Sofia, vol. 24 Issue 1 pp. 084-094 (1993), [Full Article]

Numerical Calculation of Added Mass and Damping Coefficients for Twin Hull Vessel

S. Spassov
Bulgarian Ship Hydrodynamics Centre, Varna

The present investigation concesrns the 2-d potential flow problem of forced oscillations of twin hull vessels with arbitrary shape cross sections of the hulls. Numerical calculations based on the boundary integral method are made for heave, sway and roll motions. The comparison between the numerical results of added mass and damping coefficients with the experimental data has given a good agreement. The forms which are considered correspond to drilling ships, oceanographic ships, SWATH, other types of catamarans, etc.

JTAM, Sofia, vol. 24 Issue 1 pp. 095-102 (1993), [Full Article]

International Gearninig Conference to be Held in Great Brinain

K. Arnaudov

JTAM, Sofia, vol. 24 Issue 1 pp. 103-103 (1993), [Full Article]