Results of numerical and experimental investigations of the efficiency of distributed air blowing through a perforated region of the surface of an axisymmetric body of revolution in an essentially incompressible flow with the Reynolds number ReL = 4,24·106 are reported. The blowing factor Cb is varied in the interval 0-0.00885. The Reynolds number Re** based on the momentum thickness δ** ahead of the perforated region is 5600. As the streamwise coordinate х increases, stable reduction of local friction is observed up to the distance of 600 δ** from the blowing region; the maximum value of local friction reaches 56.5% directly in the region of blowing with the maximum intensity. It is found that spontaneous blowing, which occurs due to the natural difference between the barometric and static pressures in the wind tunnel test section, can also ensure reduction of the skin friction coefficient whose value in the above-noted flow region in the main operation regime is 28.5%. Specific features of the flow around the body of revolution in the case of a rough perforated surface is analyzed through numerical simulations, and it is demonstrated that it is necessary and important to take into account this factor accompanying the blowing process.
A model of a thermochemical plume in the subduction zone is presented here, based on experimental modeling and theoretical analysis, as well as geological and geophysical data. A thermochemical plume originates at the boundary between the upper and lower mantle when a chemical additive is present in the crustal layer of the subducting oceanic lithospheric plate, which lowers the melting point of the crustal layer substance. The structure of thermal gravitational flows in the plume conduit melted out in the crustal layer was established due to experimental modeling. The heat power at the plume base and the heat power transferred by the plume conduit to the surrounding mantle were determined. The depth of location of a primary magma chamber, from which the thermochemical plume originates and rises to the surface of the continent, where the volcano is formed, was determined depending on the crustal layer thickness, the rate of subduction, and the angle of subducting lithospheric plate inclination. The primary magma chamber is formed in a region where the rates of subduction and melting of the crustal layer are equal in magnitude and directed oppositely. A model of the origin of a thermochemical plume on the primary chamber roof is presented, and the conditions of the plume conduit outcrop are determined. Based on theoretical modeling, geological and geophysical data on the depth of the primary chamber origin, the thermal and hydrodynamic conditions for the existence of a thermochemical plume incipient from the primary chamber and responsible for volcano formation on the surface were found.
The results are reported on the study of burning titanium particles with the diameter of 200 - 550 µm while free fall in air. Video with the rates of 25 and 500 fps captures the particle trajectories. The mathematical procedure for averaging of particle trajectories was developed. The trajectories can be classified into classes with the particle size variation within each class about 20 - 30 µm. The evolutions of particle coordinate x(t) and particle velocity v(t) as functions of time t (until the event of particle fragmentation) were presented as generalized functions for each of the size-classes. The comparison of empirical curves x(t) and v(t) with the analytical solutions for this problem about a spherical particle motion under gravity and aerodynamic drag forces gives the effective aerodynamic drag coefficient for a burning-in-air titanium particle in the format Cd = A /Re, where Re is the Reynolds number. For the particles within the tested size range, the parameter А is independent of the particle diameter and equals about 61 ± 2 for the particle motion with the Reynolds number varying from 1 to 10. If we take the aerodynamic drag coefficient Cd = 61/Re and the air viscosity equal to 5,07·10-5 Pa·s, then the motion of burning titanium particles in air can be described by the known analytical solution for a problem of spherical particle motion driven by forces of gravity and drag within the accuracy provided by the empirical equations.
Computational experiments in the field of thermal radiation emitted by combustion products of rocket engines allow tracing the effect of determining factors on the emission characteristics, which serves to plan, predict, and interpret a physical experiment. The paper considers the influence of the condensed phase (aluminum oxide particles), the gas phase and its individual components (H2O and CO2) on spectral and integral radiation energy flux densities and emissivity factors in various sections of the flow of heterogeneous combustion products of a model solid-propellant rocket engine (SPRE). A comparison of the emission characteristics of incomplete combustion products and combustion products is performed for the chamber and initial section of the plume of the first-stage SPRE of Trident II (D5). The calculations of spectral radiation intensity of an initial section of the plume are compared with the results of other authors.
E.Yu. Shadrin1, I.S. Sadkin1,2, E.P. Kopyev1, I.S. Anufriev1,2, V.V. Leshchevich3, S.Yu. Shimchenko3 1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia 2Novosibirsk State Technical University, Novosibirsk, Russia 3Luikov Heat and Mass Transfer Institute of NAS, Minsk, Belarus
Keywords: superheated steam, spraying burner, liquid fuel, steam, atomization, shadow photography method, disperse composition
The characteristics of a fuel spray atomized by a steam jet were studied using the method of shadow photography. The studied method of forming a two-phase flow for dispersing liquid fuel allows application of a wide range of hydrocarbons and increases the service life of the combustion equipment due to the absence of fuel spraying nozzles. Using a long-focus macroscopic lens, the dispersed composition of spent engine oil was measured at various fuel supply frequencies: 10, 25, and 40 Hz. The dispersed phase velocity was determined using the PIV-algorithms; it amounted to 60 m/s for all studied regimes. It is shown that the frequency of liquid fuel supply does not affect the size and velocity of the formed fuel droplets.
In the current study, we conducted a numerical analysis of water-TiO2 nanofluidand entropy generation in a wavy channel under constant heat flow( q") by using a two-phase mixture model. The analyses were carried under a laminar forced convection flow condition. Reynolds numbers (Re) are considered in the range of 50≤Re≤600, with the volume fraction of nanoparticles φ are considered in the range of 1 ≤ φ ≤ 5 %. The governing equations are solved by using Ansys-Fluent software 14.5.The validation of the outcomes has demonstrated a strong consensus between the results and the literature's data. The effect of various Re, φ, and wavy amplitudes (α) on the flow behavior and heat transfer are examined. Moreover,the distribution of the static temperature, streamlines, total entropy generation Sg,t, Bejan number (Be) contours have been presented and discussed. Results showed that the heat transfer rate improves when φ , Re, and α increase. The heat transfer is enhanced when using a wavy wall compared to a straight wall. The performance evaluation criterion (PEC) increases with φ and Re. Therefore, it is recommended to use large values for each of φ and Re in the wavy channel from engineering and economics perspectives. Concerning Sg,t, Sg,t,h Be, we conclude that these parameters decrease when φ and Re increase, except Sg,v is increased with φ and Re.
A.B. Kruglov, V.I. Rachkov, I.G. Merinov, V.S. Kharitonov, L.P. Paredes
a:2:{s:4:"TEXT";s:59:"National Research Nuclear University “MEPhI”, Moscow,Russia";s:4:"TYPE";s:4:"text";}
Keywords: pulse heating method, thermal conductivity coefficient of lead, impurities in lead, thermal resistance of contact of lead melt and steel
The article presents the results of measuring the coefficient of thermal conductivity of lead in the temperature range of 350-1000 °C using the pulse heating method. The methodology of processing experimental data is described. The estimates of the experimental data error are given. The difference in the content of impurities in the lead samples is shown to have an in significant effect on the thermal conductivity coefficient of the lead melt. The deviation of the experimental data on the thermal conductivity of lead from the proposed interpolating dependence does not exceed ±2 %. The obtained data are compared with the known recommended dependences for calculating the thermal conductivity coefficient of lead.
A comprehensive study of the thermophysical properties of an ultralight eutectic Mg-Li alloy (with a lithium content of 23 at.%), promising for use in the aerospace industry has been carried out. New reliable experimental data have been obtained for thermal conductivity, thermal diffusivity, specific heat capacity, density, linear thermal expansion coefficient and relative elongation of the alloy in the temperature range of 300 - 759 ÷781 K. The obtained results have been compared with well-known literature data on thermal conductivity and thermal expansion for Mg-Li system alloys. Approximation equations and a table of reference data of the studied properties are presented. The relative density change during melting of eutectic has been determined.
S.D. Sleptsov1, N.A. Savvinova2 1Kutateladze Institute of Thermophysics SB RAS Novosibirsk, Novosibirsk, Russia 2North-Eastern Federal University, Yakutsk, Russia
Keywords: ice, melting, Stefan problem, anisotropic scattering, selectivity, substrate
Numerical calculation of the influence of various types of opaque substrates on ice melting was carried out using mathematical modeling methods. It is shown that while maintaining a constant low temperature of the left boundary of the heat-conducting substrate, ice melting does not depend on its thermophysical properties. The threshold value of thermophysical properties, below which the dependence on the substrate must be taken into account, is found.
4 August, 2007 is the 75th anniversary of the well known scientist, scientific administrator and head of scientific school of Tymen Division of Khristianovich Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences, Doctor of Physical and Mathematical Sciences, Professor Amir A. Gubaidullin.
