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Thermophysics and Aeromechanics

2015 year, number 2

1.
Investigation of the structure and properties of titaniumstainless steel permanent joints obtained by laser welding with the use of intermediate inserts and nanopowders

A.N. Cherepanov1, A.M. Orishich1, N.B. Pugacheva2, and V.P. Shapeev1
1Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
2Institute of Engineering Science UB RAS, Ekaterinburg, Russia
E-mail: ancher@itam.nsc.ru
Keywords: laser welding, dissimilar materials, insert, titanium, stainless steel, structure, mechanical properties, numeri-cal modeling
Pages: 135142

Abstract >>
Results of an experimental study of the structure, the phase composition, and the mechanical properties of laser-welded joints of 3mm thick titanium and 12Kh18N10T steel sheets obtained with the use of intermediate inserts and nanopowdered modifying additives are reported. It is shown that that such parameters as the speed of welding, the radiation power, and the laser-beam focal spot position all exert a substantial influence on the welding- bath process and on the seam structure formed. In terms of chemical composition, most uniform seams with the best mechanical strength are formed at a 1m/min traverse speed of laser and 2.35kW laser power, with the focus having been positioned at the lower surface of the sheets. Under all other conditions being identical, uplift of the focus to workpiece surface or to a higher position results in unsteady steel melting, in a decreased depth and reduced degree of the diffusion-induced mixing of elements, and in an interpolate connection formed according to the soldering mechanism in the root portion of the seam. The seam material is an over-saturated copper-based solid solution of alloying elements with homogeneously distributed intermetallic disperse particles (Ti(Fe, Cr)2 and TiCu3) contained in this alloy. Brittle fracture areas exhibiting cleavage and quasi-cleavage facets correspond to coarse Ti(Fe, Cr)2 intermetallic particles or to diffusion zones primarily occurring at the interface with the titanium alloy. The reported data and the conclusions drawn from the numerical calculations of the thermophysical processes of welding of 3mm thick titanium and steel sheets through an intermediate copper insert are in qualitative agreement with the experimental data. The latter agreement points to adequacy of the numerical description of the melting processes of contacting materials versus welding conditions and focal-spot position in the system.

DOI: http://dx.doi.org/10.1134/S0869864315020018
																								



2.
Spectral diffusion model of heavy inertial particles in a random velocity field of the continuous medium

I.V. Derevich
Bauman Moscow State Technical University, Moscow, Russia
E-mail: DerevichIgor@bmstu.ru
Keywords: turbulence, dispersed flow, turbulent spectrum, inertia of particles, Lagrange and Euler correlations, Karman spectrum, Saffman spectrum
Pages: 143162

Abstract >>
Based on the spectral expansion of Euler correlation of the carrier medium the authors have obtained a closed system of functional equations for the Lagrange spectra of heavy inertial particles and the velocity fluctuations of the carrier medium on the particle trajectory. To split the fourth moments the approximation of quasinormality and velocity fluctuations of particles is performed by a random Gaussian process. The approximate self-consistent method is proposed for solving the resulting system of functional equations. The spectrum of Euler correlations of medium velocity fluctuations is modeled by Saffman and Karman distributions. The influence of the spatial microstructure of turbulence, the particles inertia and velocity slip on the intensity of chaotic motion and the coefficient of turbulent diffusion of dispersed particles has been studied.

DOI: http://dx.doi.org/10.1134/S086986431502002X
																								



3.
Features of eddy diffusion of momentum and heat in stably stratified flows of environment

A.F. Kurbatskiy1,2 and L.I. Kurbatskaya3
1Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
3Institute for Computational Mathematics and Mathematical Geophysics SB RAS, Novosibirsk, Russia
E-mail: kurbat@itam.nsc.ru
Keywords: turbulence, planetary boundary layer, upper troposphere and lower stratosphere, eddy diffusivity for momentum and heat
Pages: 163176

Abstract >>
The study was performed on features of eddy transport of momentum and heat in the lower atmosphere, which includes the planetary boundary layer as well as upper troposphere and lower stratosphere; the study used a three-parametric method for modeling of stratified turbulent flows. A focus was put on analysis of behavior of vertical diffusivities of momentum and heat: data were obtained through direct measurements and through simulation with three-parametric turbulence model with account for effects of internal gravitational waves which support momentum transfer under condition of very stable stratification (while possessing considerable wavy dynamics). It was demonstrated that the profile of vertical diffusivity for momentum, which was calculated using three-parametric turbulence model, is in agreement with data on direct measurements when measured either within a stable stratified planetary boundary layer or beyond this layer, in free atmosphere.

DOI: http://dx.doi.org/10.1134/S0869864315020031
																								



4.
On the similarity with respect to the density Froude number of the flow in turbulent wake of a towed body in a linearly stratified medium

N.P. Moshkin1, A.V. Fomina2, and G.G. Chernykh3,4,5
1Lavrentyev Institute of Hydrodynamics SB RAS, Novosibirsk, Russia
2Novokuznetsk Institute (branch) of the Kemerovo State University, Novokuznetsk, Russia
3Institute of Computational Technologies SB RAS, Novosibirsk, Russia
4Siberian State University of Telecommunications and Information Sciences, Novosibirsk, Russia
5Novosibirsk State University, Novosibirsk, Russia
E-mails: chernykh@ict.nsc.ru, moshkin@gmail.com, fav@rtdc.ru
Keywords: stratified fluid, turbulent wake, density Froude number, numerical modelling
Pages: 177184

Abstract >>
The flow in a far turbulent wake of a towed body has been modeled with respect to the density Froude number in a linearly stratified medium. It is shown that at sufficiently high values of the density Froude number, there is a similarity of the parameters of the wake and of the internal waves generated by it.

DOI: http://dx.doi.org/10.1134/S0869864315020043
																								



5.
Formation of vortex structures in channels with mass injection and their interaction with surfaces in solid-fuel rocket engines

B.Ya. Benderskiy and A.A. Chernova
Kalashnikov Izhevsk State Technical University, Izhevsk, Russia
E-mail: alicaaa@gmail.com
Keywords: gas dynamics, topology, singular points, combustion chamber, power installation
Pages: 185190

Abstract >>
The topological features of the structure of combustion products flow in the flow paths with different shapes of channel cross sections at power installations are considered. The results of mathematical modeling of internal gas dynamics of the flow paths of power installations are compared with experimental data.

DOI: http://dx.doi.org/10.1134/S0869864315020055
																								



6.
Simulating nonlinear waves on the surface of thin liquid film entrained by turbulent gas flow

I.S. Vozhakov, D.G. Arkhipov, and O.Yu. Tsvelodub
Novosibirsk State University, Novosibirsk, Russia
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
E-mail: vozhakov@gmail.com
Keywords: falling film, gas flow, model system, stability, evolution of perturbations
Pages: 191202

Abstract >>
A new system of equations has been derived to simulate the dynamics of long-wave perturbations on the surface of a thin layer of viscous liquid, flowing down a vertical plane and blown by co-current turbulent gas flow. The analysis of linear stability of the unperturbed flow has been performed. It has been found that at moderate Reynolds numbers of liquid, Benjamin linear model and model of boundary conditions transfer to the unperturbed level for a disturbed gas flow give qualitatively similar results. With decreasing Reynolds number differences between the results obtained by different turbulence models become more pronounced. In the case of small Reynolds numbers of fluid, the system of equations results in a single evolution equation for film thickness deviation from the undisturbed level. Some solutions of this equation have been considered.

DOI: http://dx.doi.org/10.1134/S0869864315020067
																								



7.
Influence of uniform magnetic field on laminar regimes of natural convection in an enclosure

N.S. Bondareva1 and M.A. Sheremet1, 2
1Tomsk State University, Tomsk, Russia
2Tomsk Polytechnic University, Tomsk, Russia
E-mail: Michael-sher@yandex.ru
Keywords: natural convection, uniform magnetic field, Boussinesq approximation, laminar regime, numerical modelling
Pages: 203216

Abstract >>
A numerical analysis of spatial laminar regimes of natural convection in an enclosure is conducted in the presence of a uniform magnetic field. The mathematical model formulated in dimensionless natural variables velocitypressuretemperature has been implemented numerically by the method of control volume. The influence of the Rayleigh number (103 ≤ Ra ≤ 105) and the Hartmann number (0 ≤ Ha ≤ 100), the orientation of the magnetic induction vector (0 ≤ φ ≤ π / 2) as well as of the geometric parameter (0.2 ≤ A ≤ 5), which reflects the enclosure relative length, on the velocity and temperature distributions as well as the average Nusselt number on a typical isothermal boundary has been studied in detail. A possibility of describing the integral heat exchange in the spatial object under consideration on the basis of the two-dimensional model has been established.

DOI: http://dx.doi.org/10.1134/S0869864315020079
																								



8.
Combined effects of suction/injection and wall surface curvature on natural convection flow in a vertical micro-porous annulus

B.K. Jha, B. Aina, and S.A. Muhammad
Ahmadu Bello University, Zaria, Nigeria
E-mail: ainavicdydx@gmail.com, basant777@yahoo.co.uk, shehukurami@yahoo.com
Keywords: natural convection, micro-porous-annulus (MPA), suction/injection, velocity slip and temperature jump
Pages: 217228

Abstract >>
This study investigates analytically the hydrodynamic and thermal behaviour of a fully developed natural convection flow in a vertical micro-porous-annulus (MPA) taking into account the velocity slip and temperature jump at the outer surface of inner porous cylinder and inner surface of outer porous cylinder. A closed form solution is presented for velocity, temperature, volume flow rate, skin friction and rate of heat transfer expressed as a Nusselt number. The influence of each governing parameter on hydrodynamic and thermal behaviour is discussed with the aid of graphs. During the course of investigation, it is found that as suction/injection on the cylinder walls increases, the fluid velocity and temperature is enhanced. In addition, it is observed that wall surface curvature has a significant effect on flow and thermal characteristics.

DOI: http://dx.doi.org/10.1134/S0869864315020080
																								



9.
Modelling of turbulent flow in a radial reactor with fixed bed

U.K. Zhapbasbayev, G.I. Ramazanova, and O.B. Kenzhaliev
Joint-stock company KazakhstanBritish Technical University, Almaty, Kazakhstan
E-mail: uzak.zh@mail.ru
Keywords: radial reactor, fixed bed, κ–ε turbulence model, coupling conditions
Pages: 229243

Abstract >>
The data of the computation of turbulent flow in the CFπ and CPπ configurations of the radial reactor with a fixed bed are presented. The Reynolds motion equations have been solved jointly with the κε turbulence model. To couple the parameters of flows at the interface free part fixed bed the classical continuity equations were used. The computational data are obtained for the averaged and turbulent characteristics, and it is shown that the flow in the fixed bed causes the generation of the turbulence kinetic energy and its dissipation rate; the flow in the CFπ configuration is distributed more uniformly as compared to the CPπ configuration of the radial reactor. Computed data are compared with the experimental ones.

DOI: http://dx.doi.org/10.1134/S0869864315020092
																								



10.
Investigation of regimes of gas hydrate formation in a porous medium, partially saturated with ice

M.K. Khasanov
Sterlitamak Branch of Bashkir State University, Sterlitamak, Russia
E-mail: hasanovmk@mail.ru
Keywords: porous medium, gas hydrate, filtration
Pages: 245255

Abstract >>
The features of gas hydrate formation at gas injection into a porous medium, initially filled with gas and ice, are investigated. The self-similar solutions to the single-dimensional problem, describing distribution of the main parameters in a layer, were derived. It is shown that there are the solutions, according to which the gas hydrate formation can occur in three different regimes. The critical diagrams for such regimes are plotted.

DOI: http://dx.doi.org/10.1134/S0869864315020109
																								



11.
Resistance to destruction of material samples in supersonic high-temperature flow

V.A. Zabaykin1, A.N. Prokhorov2, and P.K. Tretyakov1
1Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
2Central Institute of Aviation Motors, Moscow, Russia
E-mail: vaz@itam.nsc.ru
Keywords: supersonic high-temperature flow, archeater, heat-resistant materials, combustion
Pages: 257260

Abstract >>
Resistance to destruction of metallic and nonmetallic objects in high-temperature supersonic flow was studied in experiments. The significant role of gas-dynamic structures on the zone of heat-up and ignition of metals was demonstrated. As the critical temperature was achieved, sample combustion or erosion commences, thus determining the sample destruction rate.

DOI: http://dx.doi.org/10.1134/S0869864315020110
																								



12.
90th Anniversary of Evgeniya M. Khabakhpasheva

Editorial Board
Siberian Branch of the RAS, Novosibirsk, Russia
Pages: 261262

Abstract >>
February 20, 2015 marked the 90th anniversary of Professor Evgeniya M. Khabakhpasheva, Honored Scientist of Russia and Doctor of Technical Sciences.

DOI: http://dx.doi.org/10.1134/S0869864315020122
																								



13.
70th Anniversary of Viktor V. Kozlov

Editorial Board
Siberian Branch of the RAS, Novosibirsk, Russia
Pages: 263264

Abstract >>
April 24, 2015 is the 70th anniversary of the distinguished scientist in the field of fluid mechanics, Doctor in Physics and Mathematics, Professor Victor V. Kozlov.

DOI: http://dx.doi.org/10.1134/S0869864315020134