Volume 95, №6
REFLECTION AND REFRACTION OF HARMONIC WAVES AT THE BOUNDARIES OF A POROUS MEDIUM SATURATED WITH A BUBBLY LIQUID
Refl ection and transmission of acoustic waves at the interface between water and a porous medium saturated with
bubbly liquid and the porous medium saturated with a bubbly liquid–water interface at normal incidence of these
waves on the indicated interfaces have been studied theoretically. It is shown that there exists a range of frequencies,
for which refl ection of acoustic waves from the interface between water and a porous medium saturated with bubbly
liquid is similar to refl ection of these waves from a free surface, and for refl ection of acoustic waves from the medium
saturated with bubbly liquid/water interface it is similar to refl ection from a rigid wall
Author:
I. K. Gimaltdinov, L. F. Sitdikova
Keywords:
acoustic wave, porous medium, refl ection coeffi cient, transmission coeffi cient
Page:
1347
INVESTIGATION OF THE DIFFUSION PROPERTIES OF PLANT CAPILLARY-POROUS COLLOIDAL MATERIALS WITH REGARD TO THEIR SHRINKAGE
Based on the zonal method, the temperature and concentration dependences of the moisture diff usion coeffi cient
in materials subject to shrinkage in the process of drying (plates cut from apple, carrot, and beet) were found
experimentally. The concentration dependences of the moisture diff usion coeffi cient in these materials were determined
from drying curves obtained in the absence of external diff usion resistance. Shrinkage of materials was determined
experimentally, the temperature dependences of the obtained diff usion coeffi cients were described on the basis of the
theory of activated molecular diff usion of moisture in the material. It is shown that the temperature dependence of the
moisture diff usion coeffi cient in the indicated materials is described satisfactorily by the Arrhenius equation, on the
basis of which, for these materials, formulas were obtained that express the dependence of the coeffi cient of moisture
diff usion in them on their moisture content and temperature and that can be used in engineering calculations.
The obtained data on the moisture diff usion coeffi cient in the studied materials are compared with similar data
obtained for other materials. It is shown that the concentration dependences of the moisture diff usion coeffi cients of
materials subject to shrinkage during drying have the same nature and order of magnitude as similar dependences
for materials without shrinkage. The drying curves calculated using the obtained formulas were compared with the
experimental drying curves, which showed their satisfactory similarity.
Author:
S. P. Rudobashta, V. M. Dmitriev
Keywords:
convective drying, diff usion, Arrhenius equation, kinetic calculation
Page:
1357
THEORETICAL AND EXPERIMENTAL STUDIES OF CONVECTIVE DEHYDRATION OF SPICY-AROMATIC RAW MATERIALS
Various methods of drying spicy-aromatic raw materials are described. The kinetic laws governing the process of convective drying of the ginger and galangal roots have been established. The stadial regimes of dehydration, in accordance with which the temperature of the drying agent in the fi rst stage of the process is maintained at a level of 60o
C and in the second at 45o
C are substantiated and developed scientifi cally. The established regimes make
it possible to reduce the expenditures of heat in drying and ensure the most complete preservation of the natural
components of the starting material. A mathematical model of heat and mass transfer, phase transformations, and
shrinkage is proposed, which can be used to establish dehydration regimes. The calculation of the total duration of
the process of drying by V. V. Krasnikov′s method is presented.
Author:
Yu. F. Snezhkin, R. A. Shapar′, E. V. Gusarova
Keywords:
spicy-aromatic raw materials, ginger, galangal, essential oils, heat and mass transfer, convective drying, stadial dehydration, intensifi cation, energy saving
Page:
1366
ONE MORE PARAMETER DETERMINING THE STRATIFICATION OF SOLUTIONS IN SMALL-VOLUME DROPLETS
A thermodynamic approach has been used to consider the eff ects of the composition and size of micro- and nanosized
droplets of binary stratifying organic mixtures on phase equilibria. Using the examples of water–phenol and
polybutadiene–polystyrene systems, it has been shown that, unlike macroscale structures, in microsized droplets, it
is not only the volume fraction of coexisting phases but also mutual solubility of components that vary as a function
of the initial composition of a mixture. The initial composition of the mixture also determines the pattern of solubility
dependences on the droplet volume, which is due to the occurrence of various mechanisms of reduction in the free
energy of the system in mixtures of various compositions
Author:
A. V. Shishulina, A. V. Shishulina
Keywords:
disperse systems, phase transformations, core–shell, solution stratifi cation, solubility
Page:
1374
MODIFIED CARBON SORBENTS BASED ON WALNUT SHELL FOR SORPTION OF TOXIC GASES
The results of synthesis on the basis of nanocarbon for protection against a broad range of toxic chemical substances
are presented. The analysis of the specimens′ structure shows that activation contributes to the formation of a great
number of small pores and the development of a porous texture of sorbents, which leads to an increase in the specifi c
surface. Activated specimens have a micromesoporosity confi rmed by appropriate isotherms of low-temperature
adsorption of nitrogen. It is shown that the procedure of activation results in specimens with various acidity, and
this surface property has a marked eff ect on the characteristics of materials. The results of investigation of the
breakthrough time for vapors of inorganic and organic substances show that Cu and Co ion impregnations are the
most suitable for the production of a universal sorbent. Due to this, this paper presents the technology of obtaining
activated charcoals impregnated with ions of various metals that can surpass sorption properties of commercial
reference materials
Author:
Z. A. Mansurov, L. F. Velasco, P. Lodewyckx, E. O. Doszhanov, S. Azat
Keywords:
sorption materials, nanostructure, toxic gases, adsorption
Page:
1383
DESIGNING DEVICES FOR UNIFORM STEADY-STATE HEATING WITH THE METHOD OF EVOLUTIONARY STRUCTURAL OPTIMIZATION
The problem of topology optimization of a heat-conducting object for the criterion of uniformity of the steadystate temperature fi eld in an assigned domain was formulated for the fi rst time. To solve the problem, the authors
proposed a method of evolutionary topology optimization on the basis of solution of a system of linear equations with
a fi ctitious vector of the right-hand side (heat load). The method is distinguished by the technique of formation of a
vector whose components are considered as weight factors. The power distribution function of the weight coeffi cients
was proposed. Selection of the objective function (temperature at the node, average temperature in an assigned
domain, and uniformity of the temperature fi eld) is controlled by the vector of the fi ctitious heat load. The method
was tested on three problems: of minimization of the average temperature of a plate with a uniform heat generation,
of minimization of the temperature diff erence in an assigned domain of a square plate, and of optimization of the
structure of a mold for vulcanizing an industrial rubber article. The method has shown high effi ciency and versatility
Author:
A. O. Glebov, S. V. Karpushkin, E. N. Malygin
Keywords:
heat treatment, uniform heating, fi nite-element method, topology optimization
Page:
1393
HEAT EXCHANGE AND MAGNETIC HYDRODYNAMICS OF A LIQUID IN A SPHERICAL LAYER AT SMALL MAGNETIC REYNOLDS NUMBERS
Results of numerical simulation of the unsteady heat exchange in a layer of an electrically conducting liquid between two concentric spheres and of the magnetic hydrodynamics of this liquid at small magnetic Reynolds numbers (Rem = 10–1
, 10–2
, 10–3
, 10–4
, 10–5
, and 10–6
) and the homochronicity numbers Ho = 0.1 and 10 are presented. The
infl uence of the Joule heat dissipation in this layer on the evolution of the liquid fl ow structure, the temperature and
magnetic-induction fi elds, and the distributions of local Nusselt numbers in it, depending on the values of Rem and
Ho, was investigated.
Author:
S. V. Solov'ev
Keywords:
mathematical simulation, unsteady heat exchange, magnetic hydrodynamics, Joule heat dissipation, spherical layer
Page:
1406
FILM FLOW OF THE HEAT-TRANSFER AGENT IN A CLOSED THERMOSYPHON
Simulation of the infl uence of the parameters of fi lm fl ow of the heat-transfer agent under gravity on the operation
of a closed thermosyphon has been performed. It has been shown that in the stationary regime, the fi lm thickness is
under 100 μm. The main factors governing the effi ciency of the thermosyphon are the power of the heat source, the
area of the condenser, and also the viscosity and thermal conductivity of a liquid heat-transfer agent. The stability of
fi lm fl ow to a short-duration increase in the heat-source power has been considered.
Author:
S. P. Fisenko
Keywords:
fi lm, condensation, evaporation, stationary regime, Freon, stability
Page:
1421
STUDYING THE STRUCTURE OF A CEMENT COMPOSITE MODIFIED BY HYDROTHERMAL SiO2 NANOPARTICLES AND MCNTs BY THE IR-SPECTROSCOPY METHOD
The infl uence of hydrothermal small doses of SiO2 nanoparticles (NPs) and multiwalled carbon nanotubes (MCNTs) separately and combined with adding a polycarboxylate superplasticizer (SP) at the water–cement ratio W/C = 0.21 has been studied by the IR-spectroscopy method. From the shift of the frequency of absorption of silicon–oxygen tetrahedrons SiO4 to the region of reciprocal electromagnetic-radiation (EMR) wavelengths 900–1100 cm–1, it has been established that the nanoparticles added increase their kinetics and the degree of their polycondensation. The infl uence on the degree of polycondensation of silicon–oxygen tetrahedrons was more signifi cant than on the rate of hydration of clinker minerals and the gross amounts of hydration products of cement. The eff ect of infl uence on the kinetics and the degree of polycondensation of silicon–oxygen tetrahedrons depended on the chemical composition of the added nanoparticles (SiO2, MCNTs, and SiO + MCNTs) and on the age of hardening of the cement composite: it was more pronounced at the age of 28 days than at the age of 1 day for the combination of nanoparticles (SiO2 + MCNTs) and was absent at the age of 4 h. Increase in the dehree of polycondensation of silicon–oxygen
tetrahedrons corresponds to the rise in the crystallinity of a CSH gel and to the increase in the volume density of
packing of nanogranules of the gel, and also determines the increment in the mechanical characteristics of the
cement composite.
Author:
E. N. Polonina, V. V. Potapov, S. A. Zhdanok, S. N. Leonovich
Keywords:
cement composite, SiO2 nanoparticles, multiwalled carbon nanotubes, IR spectroscopy, shift of the frequency of EMR absorption, degree of polycondensation of silicon–oxygen tetrahedrons, CSH-gel structure
Page:
1426
INCREASING THE STRENGTH OF SOLDERED JOINTS BY INTRODUCING CARBON NANOTUBES INTO SOLDERING PASTES
An increase in the strength of soldered joints obtained by refl ow soldering pastes based on lead-free solders by
introducing carbon nanotubes into the composition of pastes by means of ultrasonic vibrations has been achieved.
The infl uence of the content of carbon nanotubes in the paste on the mechanical properties of soldered joints and the
solderability of coatings of electronic components has been studied.
Author:
S. A. Zhdanok, V. L. Lanin, V. A. Emel′yanov, A. V. Krauklis
Keywords:
soldering pastes, carbon nanotubes, strength of joints, ultrasonic oscillations
Page:
1437
MATHEMATICAL STUDY OF HEAT TRANSFER IN A STAGNATION FLOW OF A HYBRID NANOFLUID OVER A STRETCHING/SHRINKING CYLINDER
The steady two-dimensional incompressible boundary-layer, stagnation-point fl ows of an ordinary nanofl uid and a
hybrid CuO + MgO nanofl uid over a stretching/shrinking cylinder were investigated using the dimensionless master
Prandtl equations. It was established that the thermal conductivity of the hybrid nanofl uid is higher, it transfers a
larger amount of heat from the curved surface of the cylinder, and the skin friction force acting on its fl ow is larger,
as compared to those of the ordinary nanofl uid, and that the skin friction force acting on the fl ows of these fl uids
increases with increase in the volume fraction of nanoparticles in them.
Author:
T. Poornima, P. Sreenivasulu, B. Souayehc
Keywords:
hybrid nanofl uid, heat source, radiation, stagnation point, stretching/shrinking cylinder
Page:
1443
ANALYSIS OF THE EFFICIENCY OF DISK PUMPS
An analytical solution for the pressure drop in the disk pump is obtained. It is shown that the characteristics of a
disk pump are determined by fi ve dimensionless parameters instead of nine dimensional ones. Three criteria are
considered that limit the parameters of the pump for implementation of the laminar regime of fl uid fl ow in the pump.
Analysis of the fl ow rate-pressure head fl ow characteristics of pumps in dimensionless comparative coordinates
clearly demonstrates the hydrodynamic effi ciency of pumps. It is shown that the drop in the pump head often occurs
at the stage of transition from the disks to the pump outlet. It is shown that the left-ventricular circulatory support
pump developed earlier by the present authors is the most eff ective of those considered in this article.
Author:
A. E. Medvedev, Yu. M. Prikhod′ko, V. M. Fomin, V. P. Fomichev
Keywords:
: disk pump, viscous liquid, boundary layer, mathematical simulation
Page:
1455
MATHEMATICAL SIMULATION OF TURBULENT MIXING IN A STATIC MIXER
Results of investigation of the turbulent mixing of liquid fl ows in a static mixer are presented. It was established that,
in the case where liquids infl ow into such a mixer with equal velocities, their movement in the radial direction in
the mixer is absent. In this case, the main mechanism providing the mixing of liquid fl ows in a static mixer is their
molecular diff usion, and, therefore, the intensity of mixing of the liquid fl ows is low. An increase in the diff erence
between the velocities of the liquid fl ows at the inlet of a static mixer leads to their turbulization, with the result that
the mixing of the liquids is substantially intensifi ed, and a homogenous distribution of their mass fractions in the
mixture is attained at a smaller distance from the inlet cross section of the mixer. When the diff erence between the
velocities of the liquid fl ows at the inlet of a static mixer is large, at the center of the mixer channel there arises a
recirculation fl ow zone in which the liquids are mixed intensively
Author:
O. V. Matvienko, V. A. Romashchenko
Keywords:
mixing, turbulence, static mixer, diff usion, gasoline, oxygenate, computational fl ow dynamics
Page:
1464
EXPERIMENTAL INVESTIGATIONS OF THE COOLANT FLOW IN THE FUEL ASSEMBLY OF THE FISSILE CORE OF THE REACTOR OF A SMALL NUCLEAR POWER PLANT
The results are presented of experimental investigations of the coolant fl ow in a bundle of fuel elements of a
fuel assembly of a RITM-type reactor of a small nuclear power plant. The goal of this work is to investigate the
redistribution of the fi eld of axial and transverse velocities of the fl ow, and also the axial coolant fl ow downstream of
a plate-type spacer grid of a fuel assembly. To achieve the set goal, a number of experiments were conducted in an
aerodynamic research stand on a scaled model of a bundle of fuel elements of a fuel assembly with plate-type spacer
grids. We selected a region covering a third of the entire cross section of the model and including all standard regular
cells and cells adjacent to the casing, the stiff ener angle and the central displacer pipe as a region to be investigated.
The coolant fl ow pattern is represented by cartograms of transverse and axial velocity distribution, and also by
dependence diagrams of distribution of axial velocities and coolant fl ow rates through characteristic cell types. The
experimental results can be used for engineering feasibility demonstration of design solutions in designing RITMtype reactor fi ssile cores. The obtained experimental database on coolant fl ow in cassette-type fuel assemblies can
be used for verifi cation of advanced CFD (computational fl uid dynamics) programs (of both foreign and domestic
development) and programs of cellwise thermohydraulic calculation of fi ssile cores in proving a reliability of their
thermal performance.
Author:
S. M. Dmitriev, A. A. Dobrov, D. V. Doronkov, D. S. Doronkova, A. N. Pronin, V. I. Polunichev, A. V. Ryazanov, A. E. Khrobostov
Keywords:
nuclear reactor, cassette fi ssile core, fuel assembly, fuel element, spacer grid, coolant fl uid dynamics, axial velocity, transverse velocity, axial fl ow
Page:
1479
NUMERICAL SIMULATION OF THE PROPAGATION OF A VORTEX RING AND OF THE TRANSFER OF A PASSIVE IMPURITY BY IT
Numerical simulation of hydrodynamic processes accompanying the formation and propagation of vortex rings
produced by a piston generator has been performed. The infl uence of the characteristics of a vortex ring on the
transfer of a passive impurity is considered. Numerical calculations were carried out using nonstationary Navier–
Stokes equations and adaptive grid structures. The geometric and dynamic characteristics of the vortex ring are
obtained which correspond to the self-similar law of its dynamics and experimental data.
Author:
K. N. Volkov, V. N. Emel′yanov, and I. E. Kapranov
Keywords:
computational gas dynamics, vortex dynamics, vortex ring, vorticity, passive impurity
Page:
1489
CONJUGATE NONSTATIONARY HEAT TRANSFER IN THE COURSE OF SUPERSONIC SPATIAL FLOW PAST A SPHERICALLY BLUNTED CONE MADE FROM A COMBINED MATERIAL
The fl ow at diff erent angles of attack past a spherically blunted cone, the spherical and conical parts of which
are made of diff erent materials is considered. It is shown theoretically that the manufacture of the side surface
of such a body from a highly thermally conductive material provides heat removal from its spherical part, which
experiences maximum thermal loads and, accordingly, a decrease in the maximum body temperatures in this
area. Dimensionless expressions are obtained for estimating the decrease in the maximum temperatures of a
conical body in the area of its spherical bluntness, when the body is immersed in a fl ow at diff erent angles of
attack, by choosing the geometry of the body and materials that have the necessary thermophysical characteristics
to cover it.
Author:
V. I. Zinchenko, V. D. Gol'din
Keywords:
supersonic fl ow, aerodynamic heating, conjugate heat transfer, angle of attack, heat-shielding materials, laminar boundary layer
Page:
1498
INVESTIGATION OF NONSTATIONARY GAS-DYNAMICAL CHARACTERISTICS IN THE RESONATOR CAVITY
Mathematical simulation of a nonstationary fl ow of an ideal gas in the resonator cavity is presented. The infl uence
of the resonator depth on the amplitude and frequency characteristics of fl ow parameters is studied. The frequency
characteristics determined by numerical simulation of a two-dimensional gas fl ow are compared with the results obtained in acoustic linear approximation. The results presented in the work revealed that the nature of the fl ow — the
frequency and amplitude of pulsations — is determined by the passage of perturbations along the inner and outer
contours of the separating streamline. On increase in the resonator depth, a nonmonotonic increase in the amplitude
of fl ow oscillations is noted. There are also dips in the magnitude of the pressure amplitude at the same depth of the
resonator or when the frequency of natural oscillations in the resonator is less than the jet oscillation frequency.
Oscillations in the resonator occur in the fi rst mode, when the frequency of natural oscillations for the fi rst mode in
the resonator corresponds to the frequency of oscillations of the separating streamline. It is shown that, depending
on the resonator confi guration, the required parameters and correction coeffi cients will have diff erent values for
diff erent fl ow regimes. The paper studies in detail the confi gurations and modes of operation of the resonator and
fi nding the discrete frequencies of natural oscillations, as well as presents a mathematical model of the process of
resonator self-excitation on the basis of the theory of nonstationary fl ow.
Author:
N. I. Sidnyaev
Keywords:
resonator, natural oscillations, pressure, frequencies, fl ow around, geometry, noise, pulsations, technique
Page:
1508
NUMERICAL ANALYSIS OF THE EXPLOSIVE FORMATION OF ALUMINUM PARTICLES AT VELOCITIES OF UP TO 16 km/s WITH THE USE OF COMBINED CUMULATIVE COATINGS
Explosive propelling devices are used to test objects of rocket and space technology for resistance to the eff ects of
meteoroids and fragments of space debris. Based on numerical simulation carried out with the use of computational
complexes ANSYS/AUTODYN and ERUDIT, the possibilities of obtaining aluminum particles with velocities of up to
16 km/s with the aid of shaped charges with a combined cumulative coating are considered. For achieving this goal,
the thickness of the jet-forming part of the coating was built up degressively, with the surfaces limiting it having the
shape of the surfaces of a semiellipsoid or a semisuperellipsoid of revolution
Author:
S. V. Fedorov, V. I. Kolpakov, E. P. Vinogradova, I. A. Bolotina
Keywords:
meteoritic impact, high-velocity compact element, explosion, shaped charge, combined coating, degressive thickness, numerical simulation
Page:
1520
INFLUENCE OF NONISOTHERMALITY ON THE DYNAMICS OF GRAVITATIONAL SETTLING OF A SINGLE SOLID SPHERE AT LOW REYNOLDS NUMBERS
New experimental data are presented on the laws governing gravitational settling of a single cooled and heated
solid spherical particle in a viscous liquid in the range of Reynolds numbers Re = 0.001–1. A decrease in the rate
of stationary settling of a cooled particle and, conversely, an increase in the velocity of a heated particle are shown.
Empirical dependences of the rate of settling of a solid sphere on the diff erence of the temperatures of the particle
and liquid in the case of heating and cooling of the particle were obtained. The processing of experimental data on
the eff ective temperature has been carried out
Author:
V. A. Arkhipov, S. A. Basalaev, N. N. Zolotorev, K. G. Perfi l'eva, S. N. Polenchuk,A. S. Usanin
Keywords:
solid sphere, gravitational settling, cooled particle, heated particle, settling rate, coeffi cient of hydrodynamic resistance, temperature diff erence, eff ective temperature, experimental study
Page:
1531
HEAT TRANSFER DURING THE TUBE FLOW OF AN He–Xe GAS MIXTURE WITH A SUBSTANTIAL PRESSURE GRADIENT DUE TO THE STRONG HEATING OF THE TUBE
Numerical investigation into the heat transfer during the fl ow of a helium–xenon gas mixture in a heated tube
has been performed in a wide range of Reynolds numbers and values of the heat fl uxes into the tube wall with the
diff erential turbulence model. A comparison has been made of the obtained calculation results and experimental
data and the integral and local characteristics of the fl ow and heat transfer have been analyzed.
Author:
V. G. Lushchik, M. S. Makarova
Keywords:
helium–xenon mixture, tube, diff erential turbulence model, relaminarization
Page:
1539
HEAT TRANSFER IN A LIQUID METAL UPFLOW IN A PIPE WITH MIXED TURBULENT CONVECTION COMPLICATED BY THE INFLUENCE OF MAGNETIC FIELD
The results of a study of heat transfer in the case of a liquid metal upfl ow in a vertical heated pipe without a
magnetic fi eld, as well as in the presence of longitudinal or transverse magnetic fi elds, are presented. With the use of
microthermocouple probes, profi les of the averaged velocity and of temperature, distribution of local heat transfer
coeffi cients, and fl uctuation characteristics of temperature in the fl ow were obtained. In the absence of a magnetic
fi eld, a decrease in the heat transfer coeffi cients compared to a purely turbulent level was found, which agrees
qualitatively with the general laws governing heat transfer in mixed convection for nonmetals. Studies carried out
in a longitudinal magnetic fi eld have shown that in the confi guration of an upward fl ow too, one cannot avoid the
infl uence of thermogravitational convection, which only increases in a laminarized fl ow, leading to an increase in
instabilities and to the appearance of low-frequency velocity and temperature pulsations. In a transverse magnetic
fi eld with an upward fl ow, interesting eff ects were also revealed, associated with the action of electromagnetic forces
and thermogravitational convection on the hydrodynamics of averaged fl ow and fl uctuation characteristics of heat
transfer
Author:
N. A. Luchinkin, N. G. Razuvanov, O. N. Polyanskay, M. A. Sokolov, E. A. Burdyukov
Keywords:
liquid metals, hydrodynamics, heat transfer, magnetic fi eld, thermogravitational convection
Page:
1548
EFFECTS OF VISCOUS DISSIPATION AND PRESSURE WORK ON THE EXTENDED GRAETZ PROBLEM FOR A GASEOUS SLIP FLOW IN A MICROCHANNEL WITH WALLS HAVING A CONSTANT TEMPERATURE
Analytical studies are performed on the problem of a thermally developing laminar gaseous slip fl ow through a
parallel-plate microchannel with constant wall temperatures subject to the infl uences of axial conduction, pressure
work, and viscous dissipation. The temperature profi les and local Nusselt numbers are obtained assuming that the
fl ow is hydrodynamically fully developed in a heating zone of semi-infi nite length. The obtained solution is based
on the use of the self-adjoint formalism involviпg the rearrangement of the energy equation into a system of the
fi rst-order partial diff erential equations. For simplifi ed limiting cases, the analytical results are compared with
the available analytical and numerical ones, and a good agreement is found, which supports the validity of this
solution. The eff ects of axial heat conduction, rarefaction, pressure work, and viscous dissipation on the heat transfer
characteristics are studied and discussed in detail.
Author:
Y. Haddout, E. Essaghir, A. Oubarra, J. Lahjomri
Keywords:
heat transfer, forced convection, slip fl ow, axial heat conduction, rarefaction, self-adjoint formalism
Page:
1560
MATHEMATICAL ANALYSIS OF THE STRUCTURE OF ULTRAHYDROPHOBIC SURFACES OBTAINED BY ATMOSPHERIC PLASMA SPRAYING OF ZIRCONIUM OXIDE. 1. INVESTIGATION OF 2D PROFILES
A geometry analysis has been conducted of 2D profi les of slices of coating surfaces produced by air plasma spraying of zirconium oxide ZrO2 powder. Two scale levels of roughness of such surfaces have been identifi ed: mini- and microlevels. Correlation was detected between the ratio of the degree of roughness at these levels to the equilibrium wetting angle of a water drop. The possibility of producing superhydrophobic coatings with wetting angles exceeding 160oC has been predicted.
Author:
A. P. Yankovskii, I. P. Gulyaev, O. B. Kovalev
Keywords:
air-plasma spraying, roughness, zirconium oxide, wetting angles, hydrophobicity, geometry analysis of a surface
Page:
1570
2. INVESTIGATION OF 3D PROFILES
A geometry analysis has been conducted of 3D profi les of slices of surfaces of coatings produced by the method of air-plasma spraying of zirconium oxide ZrO2 powder. Correlation between the equilibrium angle of wetting a water
droplet and the ratio of surface roughness degrees at mini- and microlevels detected earlier in analysis of similar
2D profi les has been confi rmed. A possibility of producing ultrahydrophobic and hydrophilic coatings of various
spraying regimes has been predicted.
Author:
A. P. Yankovskii, I. P. Gulyaev, O. B. Kovalev
Keywords:
air-plasma spraying, roughness, zirconium oxide, wetting angles, hydrophobicity, hydrophilicity, geometry analysis of a surface
Page:
1580
DETERMINATION OF THERMOPHYSICAL CHARACTERISTICS OF MATERIALS BY TEMPERATURE MEASUREMENTS ON THE LINE OF A SPECIMEN'S CONJUGATION WITH A HALF-SPACE
Consideration has been given to the coeffi cient inverse heat conduction problem for determination of thermophysical
characteristics of a material by temperature measurements on the line of a specimen's conjugation with a semiinfi nite
layer of another material with known thermophysical properties. Accounting for heat sink in a thermophysical
experiment makes it possible to raise the accuracy of determining the thermophysical characteristics of a material
with preservation of its structure and to avoid the need for a laborious eff ort to ensure the adiabaticity of the specimen's
back surface. Based on the analysis of sensitivity coeffi cients, measurement times have been identifi ed that are the
most informative for determining thermophysical characteristics. The proposed methodology removes limitations
on the selection of a heating regime for a material and expands a Fourier-number-permissible measurement range.
Author:
V. A. Zverev, A. V. Teploukhov
Keywords:
thermophysical characteristics, inverse heat conduction problem, plate, half-space.
Page:
1586
COMPARISON OF THE PROPERTIES OF THE MgO–Y2O3 AND MgO–Gd2O3 CERAMIC COMPOSITES OBTAINED BY THE METHOD OF HOT COMPACTION
Data are presented for comparison of the optical, mechanical, and thermophysical properties of the MgO–Y2O3 and MgO–Gd2O3 ceramic composites consolidated through the hot compaction of the corresponding nanopowders obtained from the glycine-nitrate precursors by the method of self-propagating high-temperature synthesis. It is shown that the MgO–Y2O3 ceramics having a lower density, a higher thermal conductivity, and a larger microhardness, as compared to those of the MgO–Gd2O3 ceramics, is the material of choice for the infrared shielding windows transparent for the radiation with a wavelength falling within the range 3–5 μm.
Author:
D. A. Permin, A. V. Belyaev, V. A. Koshkin, S. S. Balabanov, P. A. Popov, M. S. Boldin, A. A. Murashov, K. E. Smetanina, I. V. Ladenkov
Keywords:
composite ceramics, self-propagating high-temperature synthesis.
Page:
1595
NUMERICAL SIMULATION OF THE NONSTATIONARY BURNING OF A SOLID PROPELLANT IN THE COMBUSTION CHAMBER OF A CONTROLLABLE SOLID-PROPELLANT PROPULSION SYSTEM
The nonstationary burning of a solid propellant in the combustion chamber of a controllable solid-propellant
propulsion system under the conditions where the pressure in this chamber changes was simulated on the basis
of the conjugate physical-mathematical model of the burning of a ballistic powder with regard for the processes
proceeding in the condensed and gas phases of the solid propellant at the fourth-kind boundary conditions on the
surface of its charge. Quantitative data on the deviation of the dynamic parameters of the gas in the combustion
chamber of such a system from the experimental ones in the case where these parameters are calculated with account
of the nonstationarity of burning of a solid-propellant charge in it and in the case where the quasistationary burning
law is used for determining the dependence of the rate of burning of this charge on the pressure in the combustion
chamber have been obtained.
Author:
A. Yu. Krainov, V. A. Poryazov, K. M. Moiseeva
Keywords:
ballistic powder, combustion chamber, variable pressure, nonstationary burning
Page:
1604
NONSTATIONARY DIFFUSION IN HYDROLYTIC DEGRADATION OF A POROUS POLYMERIC MATRIX
The paper aims to develop a mathematical model for the investigation of degradation of a porous matrix of polylactic
acid implanted in a bone tissue based on the study of kinetics of hydrolytic degradation of the matrix due to the
action of a body fl uid and diff usion of lactic acid released as a result of a chemical reaction. The numerical solution
of nonstationary nonlinear equation of lactic acid diff usion through the host tissue obtained by the fi nite diff erence
method allows one to establish a relationship between the lactic acid density in the bone tissue with time and the
density during the implanted matrix degradation as well as the density profi le of lactic acid in the bone tissue as a
function of the kinetic reaction parameters for diff erent porosities. The validation of the model is verifi ed using the
available experimental data.
Author:
E. A. Paz Estévez, R. Fagundo Mesa, N. V. Pavlyukevich
Keywords:
hydrolytic degradation, porous matrix, diff usion, polylactic acid, mathematical modeling, chemical reaction, Arrhenius law
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