The article shows the results of mathematical simulation of convective turbulent heat transfer in the closed domain with heat-conducting walls and the source of heat emission. The system of equations in the model of thermal conductivity for the solid walls and Navier-Stokes equations for gas are solved. The article examines the possible versions of the calculation of the turbulent regime in the geometrically simple air region by means of conducting the simulation within the framework of algebraic models (Van Driest and Prandtl-Reichardt), and k-ε model. On the basis of the obtained results the authors made a conclusion about the possibility of applying the algebraic model of Prandtl to describe the integral characteristics of turbulent flows in the conditions of natural convection in a geometrically simple area when the air heated by the heat source is moved by the lifting force. Besides, the temperature fields for a typical real object of heat supply are simulated in the article. The values of the dimensionless heat exchange coefficient at the air-wall interface are determined. The comparative analysis of two quite significantly different approaches to determine the average temperature in the heated room, i. e. the traditional balance approach and the approach based on the considered system of partial differential equations is executed. It is concluded that the balance models of the calculation of the temperature regime can adequately describe real temperatures of heat supply objects only for very large values of the characteristic times of the processes in question.
In the present-day machine-building creating of high-performance machining processes, subject to the requirements of resources, energy and ecology is one of the most important problems. The part of parameters of the mathematical model remained constant, while others varied. The research result contain arithmetical mean working errors of cross-sections of the part, calculated for ten equidistant points of each cross section, as well as an arithmetic mean and quadratic deviation of error. The subject of research is the technology system of combined cutting-deforming proccessing, because manufacturing application of this method shows its great potential in achieving of high quality and performance.
The consideration of damping in structural dynamics problems is an important and non-trivial problem. Its complexity, not least, is due to the need to set the correct data for the materials used and to select a model suitable for analysis. In this paper, we consider some models of viscoelastic materials from the point of view of the possibilities of using these models for the harmonic analysis of the damping properties of various materials in the linear region of elastic deformations. The proposed analysis is based on the use of parameters of viscoelastic materials specified in the form of coefficients of the differential equation of small forced vibrations. It is shown that the considered models are characterized by a different frequency dependence of the parameters of the simulated materials. This opens up the possibility of combining the model with the frequency characteristics of its parameters, approaching the frequency characteristics of the parameters of the studied viscoelastic materials.
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