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Thermophysics and Aeromechanics

2014 year, number 4

Stability of the laminar flow on a body of revolution at incidence

A.V. Dovgal, B.Yu. Zanin, and A.M. Sorokin
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
Keywords: axisymmetric body, asymmetric flow, boundary-layer separation, hydrodynamic stability

Abstract >>
An asymmetric incompressible gas flow past a body of revolution was studied in a subsonic wind tunnel. Characteristics of the velocity field at the stern of the experimental model, where a laminar boundary-layer separation and concomitant destabilization of the flow occur under axisymmetric conditions, were determined. Declination of the axis of symmetry of the body within several angular degrees results in a radical change of the time-average velocity field, the amplitude distribution of growing hydrodynamic disturbances, and their spectral distribution.

Computations of instability and turbulent mixing by Nikiforovs model

A.N. Razin and I.V. Bolshakov
Institute of Theoretical and Mathematical Physics, Russian Federal Nuclear Center — VNIIEF, Sarov, Nizhny Novgorod Region, Russia
Keywords: turbulence, Nikiforovs model, computations of model experiments

Abstract >>
The results of modeling several laboratory experiments, including a large class of advanced experimental studies of turbulent flows, are presented. The results of the Meshkovs cylindrical and planar experiments on the confluence of two zones of turbulent mixing, the experiments of Poggi, Barre, and Uberoi have been carried out using the Nikiforovs model. The presented results attest that the Nikiforovs model qualitatively describes the considered class of flows if the mean gas-dynamic quantities are computed with a high accuracy in the technique, and the width of the front of the finite-difference shock wave does not depend on the size of the computational grid cell.

Formation of the turbulent boundary layer at air blowing through a wall with an abrupt change in boundary conditions

V.I. Kornilov and A.V. Boiko
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
Keywords: experiment, incompressible turbulent boundary layer, flat plate, air blowing, friction, abrupt change in the boundary conditions

Abstract >>
Development of an incompressible turbulent boundary layer with air blowing through a finely perforated flat surface, consisting of a permeable region and impermeable region behind, was studied experimentally. The mass flow rate of injected air Q per an area unit was varied from 0 to 0.2 (kg/s)/m2. Detailed data about the internal structure of the boundary layer in the flow region, characterized by an abrupt change in the flow conditions at the boundary of permeable and impermeable regions, were obtained. A consistent decrease in the local values of skin friction coefficient along a permeable sample and with an increase in the values of Q, reaching 90% at maximal Q, is shown. The role of the flow region behind the zone with an abrupt change in the boundary conditions, essential from the viewpoint of skin friction reduction, is revealed.

On the numerical modeling of the dynamics of homogeneous isotropic turbulence

M.K. Baev1 and G.G. Chernykh1,2,3
1 Institute of Computational Technologies SB RAS, Novosibirsk, Russia
2 Siberian State University of Telecommunications and Information Systems, Novosibirsk, Russia
3 Novosibirsk State University, Novosibirsk, Russia
Keywords: homogeneous isotropic turbulence, Karman—Howarth equation, numerical modeling

Abstract >>
Using a series of mathematical models based on the closed Karman—Howarth equation, the numerical modeling of the dynamics of homogeneous isotropic turbulence was carried out. Computational results agree with known experimental data. Mathematical models are compared.

Determination of true temperature of opaque materials via spectral distribution of thermal radiation intensity: application of Wiens displacement law

S.P. Rusin
The Joint Institute for High Temperatures of RAS, Moscow, Russia
Keywords: Wiens displacement law, emissivity, true temperature

Abstract >>
The equation for the derivative connecting surface spectral emissivity, wavelength, and thermodynamic (true) temperature of an opaque heated body at the point of spectral maximum of thermal radiation was obtained. It is suggested to solve the problem of determining the true temperature of an opaque surface in two stages. At the first stage, the spectral range, most comfortable for approximation of body emissivity, is distinguished using a special function (relative emissivity), and the true temperature is determined. At the second stage, the true temperature is determined again using the resulting equation for the derivative. The dimensionless parameter that connects the radiative properties of material with the peak wavelength and characterizes deviation from Wiens displacement law was found. If the absolute value of this parameter is low, the value of true temperature obtained at the first step can be specified at the second stage. This approach is illustrated by experimental data obtained at comparison of spectral radiance of the temperature lamps.

Heat transfer characteristics for disk fans

Yu.M. Prikhodko, V.P. Chekhov, and V.P. Fomichev
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
Keywords: disk fan, friction machine, heat transfer

Abstract >>
Multiple-disk fans belong to the class of friction machines; they can be designed in two variants: centrifugal disk fans and diametrical disk fans. Flow patterns in these two types of machines are different, and they possess different heat transfer characteristics. The paper presents results of experimental study for a centrifugal disk fan under atmospheric pressure with air taken as working gas. The radial temperature distribution for a disk was obtained at different rotation speed of the rotor and different heating of the disks. Heat transfer characteristics of a centrifugal disk fan and a diametrical disk fan were compared. The research results demonstrate a higher heat transfer efficiency for centrifugal design versus diametrical disk design.

Self-oscillations in a Rijke tube with receiver positioning at its entrance

B.I. Basok and V.V. Gotsulenko
Institute of Engineering Thermophysics, NASU, Kiev, Ukraine
Keywords: self-oscillations, limit cycle, acoustic parameters, Rijke tube, instability

Abstract >>
A mathematical model with lumped parameters of self-oscillations, self-excited in a Rijke tube with receiver positioning at its input, was obtained. The influence of electric heater capacity and the size of input volume (the receiver) on the conditions of self-excitation and the form of the considered self-oscillations was considered.

In-water gas combustion in linear and annular gas bubbles

V.S. Teslenko, A.P. Drozhzhin, R.N. Medvedev, and I.S. Batraev
Lavrentyev Institute of Hydrodynamics SB RAS, Novosibirsk, Russia
Keywords: heat generator, underwater mover, gas combustion in water, combustion, annular bubble, pulse of force

Abstract >>
A new pulsed-cyclic method of in-water gas combustion was developed with separate feed of fuel gas and oxygen with the focus on development of new technologies for heat generators and submerged propellers. The results of calorimetric and hydrodynamic measurements are presented. In-water combustion of acetylene, hydrogen, and propane was tested with the operation frequency of 2–2.5 Hz and with a linear injector. The combustion dynamics of combustion of stoichiometric mixture with propane (C3H8+52) was studied for a bubble near a solid wall; the produced gas bubble continues expansion and oscillations (for the case of linear and annular bubbles). It was demonstrated that gas combustion in annular bubbles produces two same-magnitude pulses of force acting on the wall. The first pulse is produced due to expansion of combustion products, and the second pulse is produced due to axial cumulative processes after bubble collapse. This process shapes an annular vortex which facilitates high-speed convective processes between combustion products and liquid; and this convection produces small-size bubbles.

Dynamics of detonation waves in a channel with variable cross section and filled with bubbly fluid

A.S. Topolnikov1 and I.K. Gimaltdinov1,2
1 Bashkir State University, Ufa, Russia
2 Branch of Ufa Aviation-Technical University, Sterlitamak, Russia
Keywords: detonation wave, bubbly fluid, bubble compression, method of control volume

Abstract >>
The flow of bubbly fluid comprising a mixture of bubbles filled with explosive and inert gases, which is driven through a converging channel, was studied. Depending on the velocity of the hummer hitting the bubbly fluid boundary, the flow may be accompanied by the development of detonation waves which compress the bubbles with inert gas.

Characteristics of dual-combustion ramjet

Yu.P. Gounko and V.V. Shumskiy
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
Keywords: ramjet, air-intake, dual-combustion chamber

Abstract >>
The authors discuss a possibility to use a diverging dual-combustion chamber as applied to high-supersonic boost ramjets operating at flight Mach numbers up to f = 8–10. Due to diverging, this chamber allows beginning the ramjet operation from flight Mach numbers Mf ini = 23. The diverging combustion chamber is characterized by a ratio of its exit cross-sectional area relative to the cross-sectional area of air-intake throat. This expansion area ratio is determined at Mf = Mf ini, but it should be the same at all flight Mach numbers Mf => Mf ini, and depends on two factors: the location of a normal shock in the air-intake throat and the condition of reaching the critical velocity at the chamber exit. The dual-combustion chamber provides heat supply in its alone channel first to the subsonic flow and then, along with acceleration of the flying vehicle, to the supersonic flow, which is bound with a decrease in relative heating of working gas. Calculations of characteristics of an exemplified dual-combustion ramjet considered with a two-dimensional air-intake were performed in the range of Mf = 37.

Numerical investigation of the influence of crystallization of ultrafine particles of aluminum oxide on energy characteristics of solid-propellant rocket engine

N.N. Dyachenko and L.I. Dyachenko
Tomsk State University, Tomsk, Russia
Keywords: multiphase flow, distribution function, coagulation, crushing, crystallization, ultrafine ensemble of particles

Abstract >>
The results of numerical investigation of a multiphase flow considering coagulation, crushing and crystallization of the particles of polydispersed condensate in the nozzles of solid-propellant rocket engine are presented. The influence of particles crystallization on the energy characteristics of the engine is shown.

The heating and acceleration dynamics of Al2O3 particles in the axisymmetric heterogeneous flow emanating from a plasma torch with inter-electrode inserts

A.A. Mikhalchenko1, V.I. Kuzmin1, D.V. Sergachev1, E.V. Kartaev1, S.N. Ivanchik2, and I.S. Ivanchik2
1 Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
2 Novosibirsk State Academy of Water Transport, Novosibirsk, Russia
Keywords: low-temperature plasma, plasma torch with inter-electrode inserts, axisymmetric two-phase flow, temperature and velocity of Al2O3 particles

Abstract >>
Measured data on the temperature and velocity of Al2O3 particles of size fraction 34±6 μm in the jet emanating from a DC plasma torch with inter-electrode inserts under conditions of axisymmetric heterogeneous flow are reported. The velocity and temperature of individual particles were measured using a laser-optical diagnostic complex, which was a combination of a bifocal laser anemometer and a pyrometer based on a compact spectrometer. For measuring the temperature of individual particles in the particle-laden plasma jet, three-color pyrometry was used. The obtained data on the characteristics of particles in the jet emanating from the plasma spray torch with inter-electrode inserts equipped with a unit for radial-annular injection of powder into the plasma jet show that the implemented conditions for processing powder materials allow reaching a high homogeneity of the aggregate state of particles in the jet flow (~ 100 % of melted particles).

70th Anniversary of Viktor I. Terekhov

Editorial Board
Siberian Branch of the RAS, Novosibirsk, Russia

Abstract >>
August 5, 2014 was the 70th anniversary of the Honoured Scientist of the Russian Federation, Doctor of Technical Sciences, Professor Viktor I. Terekhov.