Thermophysics and Aeromechanics最新文献

The gas temperature measurements at the level of the inner wall of Ranque vortex tubes of the square and circular cross sections with variations in the cold mass fractions for both tubes showed the presence of three characteristic zones of temperature growth, which do not change over a wide range of the cold mass fraction. These zones are typical when analyzing the flow in a vortex tube within the framework of the flow crisis concept.

The work is devoted to the study of random statistical processes in two-phase flows. The objective is to obtain new computational and experimental data on the influence of previously undetermined factors on the trajectories of particle motion, their segregation, and the formation of a locally continuous flow field of the dispersed phase in supersonic turbulent two-phase flows. The results of computational and experimental study of the flow features of a two-phase supersonic flow are presented. A new experimental method was applied for analysis of influence of random statistical factors on the particle distribution in a high-speed carrier flow. The physical basis of the proposed method is to indicate the flow rate of the dispersed phase by means of particle adhesion to an obstacle installed in the flow. In order to analyze the segregation of the dispersed phase in the flow, the approach of quasi-continuumization of individual particle trajectories is applied. The method obtains a locally continuous flow stress field for dispersed phase flow. Empirical coefficients resulting from the influence of random statistical factors on the motion of dispersed particles in a two-phase flow are determined. The obtained computational and experimental data clarify the prediction of the distribution and segregation of dispersed phase particles with a size of 15–40 microns in a supersonic free flow.

In a model experiment, the process of interaction of an external artificial disturbance with the leading edge of a straight wing model was investigated. The characteristics and features of the development of boundary layer disturbances, generated as a result of the interaction of external disturbances, and the blunted leading edge of the wing model have been obtained. The research was carried out in a subsonic low-turbulence wind tunnel using a hot-wire anemometry method for detecting disturbances. Localized disturbances generated in the incoming flow were shown to induce longitudinal streaky structures in the boundary layer of the straight wing. High-frequency wave packets (precursors) appeared at the boundaries (fronts) of longitudinal structures. The dynamics of the development of wave packets and localized longitudinal structures in the boundary layer above the wing profile in a gradient flow was studied.

The paper presents the experimental results on the disposal of infected medical waste using low-temperature plasma. It is shown that infected medical waste can be processed using plasma technology. During plasma destruction of these materials, their biological disinfection with production of chemically inert, safe slag is guaranteed.

Measurements of full pressure pulsations in the mixing layer of a supersonic, strongly underexposed jet were performed. The resulting pressure was converted into a longitudinal velocity, which allowed determining the main characteristics of the layer: its growth rate and thickness, longitudinal and transverse dimensions of disturbances, intensity, and spectral composition of turbulence. The layer under consideration was in a state of saturation, with a wide range of disturbances being realized within. The measured growth rate of the layer turned out to be four times higher than that calculated by a statistically generalized method. The intensity of disturbances of the longitudinal velocity component was determined in the considered layer by two groups of disturbances — low-frequency and high-frequency — with approximately equal inputs. From the analysis of the measurement results, it follows that the mass transfer across the layer is inversely proportional to the lengths of the vortices, and in the upper part of the frequency range of intense disturbances it is many times higher. The high mass transfer across the layer causes its intensive mixing and rapid growth rate.

In this review paper, using the example of AM–Pb and AM–Bi melts (AM is an alkali metal), modern ideas on the nature of chemical short-range order in liquid metal systems with partial ionic bonding are briefly presented. Generalization and analysis of the experimental data obtained by the authors on the volumetric properties and mutual diffusion in liquid alloys of alkali metals with lead and bismuth have been carried out. The behavior of these properties is shown to generally agree with existing simple models that assume the presence of ionic complexes in melts, which gradually dissociate with increasing temperature. At the same time, the need to refine the structure of polyanionic complexes in liquid AM–Bi systems is confirmed.

A method of panoramic temperature measurement based on registering the fluorescence of thin-walled coatings on the inner surface of a flying vehicle model is considered. The method allows investigations in optically polluted flows of high-enthalpy short-duration wind tunnels. The temperature and heat fluxes on the aerodynamic model surface are retrieved by means of combining the results of temperature measurements with the numerical solution of an adjoint problem of the flow around the flying vehicle. Implementation of this method in practice is performed in the flow of a hotshot wind tunnel based at ITAM SB RAS.

The paper is concerned with an experimental study of heat transfer and boiling crisis development on a biphilic silicon surface made using a set of methods, including chemical vapor deposition and laser texturing. It is shown that the use of a biphilic surface with the proposed configuration of hydrophobic zones on a superhydrophilic base leads simultaneously to an increase in heat transfer by 60% and an increase in the critical heat flux by 76% as compared to an unmodified surface.

Results of a numerical study of supersonic flows formed in channels with a square cross section are reported. Configurations consisting of a constricting entrance section formed by four compression wedges aligned at a right angle to each other and a subsequent channel with a constant cross section are considered. The initial shock waves formed on the nose compression wedges pairwise intersect each other in dihedral corners of the configuration along the swept lines, and a complex system of reflected and subsequent interacting shock waves of the general three-dimensional position is formed further downstream. The data are obtained in a supersonic range of freestream Mach numbers M = 2–4 for compression wedge angles of 3° and 8° in flows with both regular and irregular interaction of the initial shock waves in dihedral corners of the configuration.

The results of experimental measurements are presented to assess the correlation characteristics of disturbances in the boundary layer of a flat plate with a sharp leading edge and pulsations of the incoming flow in cases of natural pulsations and influence of an N-wave for Mach 2 on the leading edge. The parameters of the cross-correlation of signals from two constant-temperature anemometry (CTA) are obtained digitally. The frequency ranges with apparent correlation between the mass flow rate pulsations measured by the probes are determined.