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Thermophysics and Aeromechanics

2016 year, number 4

Direct numerical simulation of the turbulent flows of power-law fluids in a circular pipe

A.A. Gavrilov1 and V.Ya. Rudyak2
1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
2Novosibirsk State University of Architecture and Civil Engineering,  Novosibirsk, Russia
Keywords: non-Newtonian fluids, power-law fluids, turbulent flows, direct numerical simulation, flow in a circu-lar pipe, turbulence anisotropy, viscosity pulsations
Pages: 473486

Abstract >>
Fully developed turbulent pipe flows of power-law fluids are studied by means of direct numerical simulation. Two series of calculations at generalised Reynolds numbers of approximately 10000 and 20000 were carried out. Five different power law indexes n from 0.4 to 1 were considered. The distributions of components of Reynolds stress tensor, averaged viscosity, viscosity fluctuations, and measures of turbulent anisotropy are presented. The friction coefficient predicted by the simulations is in a good agreement with the correlation obtained from experiment. Flows of power-law fluids exhibit stronger anisotropy of the Reynolds stress tensor compared with the flow of Newtonian fluid. The turbulence anisotropy becomes more significant with the decreasing flow index n. An increase in apparent viscosity away from the wall leads to the damping of the wall-normal velocity pulsations. The suppression of the turbulent energy redistribution between the Reynolds stress tensor components observed in the simulations leads to a strong domination of the axial velocity pulsations. The damping of wall-normal velocity pulsations leads to a reduction of the fluctuating transport of momentum from the core toward the wall, which explains the effect of drag reduction.

DOI: 10.1134/S0869864316040016

Dynamic compliance of multilayer coatings

V.M. Kulik
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
E- mail:
Keywords: forced deformation, flat pressure wave, compliant coating, multilayering, dynamic compliance, ratio of elasticity modulus to density of different layers
Pages: 487498

Abstract >>
The algorithm for calculation of dynamic compliance of multilayer coatings was developed. The compliance modulus and phase lag of coating surface motion vs. the current pressure depend on viscoelastic properties of materials, ratio of wavelength to layer thickness l/H, and ratio of wave velocity to propagation velocity of shear vibrations in the base layer V/Ct,20 Dynamic compliance of the two-layer coating consisting of a thick base layer and thin durable outer layer was calculated. The elasticity modulus of the outer layer ranged up to eight values of elastic modulus of the inner layer; the density of the outer layer either remained equal to the density of the inner layer or increased proportionally to the elastic modulus. Depending on  V/Ct,20 two scenarios of compliant coating interaction with the turbulent flow were distinguished: resonant and broadband ones. It is shown that the vibration properties of two-layer coatings can be significantly better than the properties of the monolayer coatings. This makes it possible either to increase the coating strength or to work efficiently at lower velocities.

DOI: 10.1134/S0869864316040028

Effect of nose shape on the shock standoff distance at nearsonic flows

Z. Eghlima and K. Mansour
Amirkabir University of Technology, Tehran, Iran
Keywords: shock standoff distance, transonic flow, blunt body, sharp body
Pages: 499512

Abstract >>
This paper describes a numerical solution of the bow shock shape ahead of some blunt and sharp axisymmetric noses containing sphere, blunt cone, and sharp cone at steady transonic flow in the Mach number range of 1.01 to 1.2. For validating the results, one sphere and three blunt cones are modeled, and their shock standoff distance is compared with other experimental and numerical studies. The flow over other noses with similar geometric parameters is then solved and compared with each other. In this study, the Reynolds-averaged NavierStokes equations are solved using the SpalartAllmaras turbulence model. The purpose of this study is to determine the shock standoff distance for some blunt and sharp noses at low supersonic free flight speed. The shock standoff distance is determined from the Mach number curve on the symmetry line. The present numerical simulations reach down to M=1.01 a range where it is almost very difficult to set in xperimental
studies. The shock wave locations were found to agree well with previous numerical and experimental studies. Our results are closer to the experimental results compared to other numerical studies. In addition, the results for shock standoff distances over paraboloids in these speed ranges have not been previously published as far as we know.

DOI: 10.1134/S086986431604003X

Experimental investigation of acoustic self-oscillation influence on decay process for underexpanded supersonic jet in submerged space

V.Yu. Aleksandrov, K.Yu. Arefyev, and M.A. Ilchenko
Central Institute Aviation Motor named after P.I. Baranov, Moscow, Russia
Keywords: mixing layer, jet nozzle, acoustic self-oscillations, spectral characteristics, shock wave structures
Pages: 513521

Abstract >>
Intensification of mixing between the gaseous working body ejected through a jet nozzle with ambient medium is an important scientific and technical problem. Effective mixing can increase the total efficiency of power and propulsion apparatuses. The promising approach, although poorly studied, is generation of acoustic self-oscillation inside the jet nozzle: this impact might enhance the decay of a supersonic jet and improve the mixing parameters. The paper presents peculiar properties of acoustic self-excitation in jet nozzle. The paper presents results of experimental study performed for a model injector with a set of plates placed into the flow channel, enabling the excitation of acoustic self-oscillations. The study reveals the regularity of under-expanded supersonic jet decay in submerged space for different flow modes. Experimental data support the efficiency of using the jet nozzle with acoustic self-oscillation in application to the systems of gas fuel supply. Experimental results can be used for designing new power apparatuses for aviation and space industry and for process plants.

DOI: 10.1134/S0869864316040041

Heat transfer characteristics of decaying swirl flow through a circular tube with co/counter dual twisted-tape swirl generators

W. Changcharoen1, P. Samruaisin1, P. Eiamsa-ard2, and S. Eiamsa-ard1
1Mahanakorn University of Technology, Bangkok, Thailand
2Phetchaburi Rajabhat University, Phetchaburi, Thailand
Keywords: decaying swirl flow, heat transfer, friction factor, dual twisted tapes
Pages: 523536

Abstract >>
The influence of co/counter dual-twisted tapes (CoT/CT) on heat transfer rate in a circular tube has been investigated experimentally. In the experiment, the dual-twisted tapes are placed at the entry of the test tube in two arrangements: (1) each of dual twisted tape was twisted in the same direction that can produce co-swirl flow at the entry and (2) each of dual twisted tape was twisted in the opposite direction that can produce counter-swirl flow. Dual tapes were twisted in three different twist ratios (y/w = 3, 4, and 5) for generating different swirl intensities at the entry of the test section while the single twisted tape (ST) was also the test for comparison. The aim at using the dual twisted tapes is to create co/counter-rotating swirl flows having a significant influence on the flow turbulence intensity at the entry section leading to higher heat transfer enhancement. Average Nusselt numbers of CoT/CT are determined and also compared with those obtained from other similar cases, i.e., ST. The experimental results on the heat transfer rates indicated that the tubes with the dual twisted tapes (CoT/CT) are higher than those with the single tape at the entry section (x/D = 0 to 10). The heat transfer rates at longer distance became lower due to high interaction of each swirl. In addition, the mean Nusselt number and friction factor for the swirl generator created by the CT is nearly similar to CoT results.

DOI: 10.1134/S0869864316040053

On hydrate growth in aquatic gas solution

V.Sh. Shagapov1,2, Yu.A. Yumagulova2, and O.A. Shepelkevich3
1Institute of Mechanics of Ufa Scientific Center RAS, Ufa, Russia
2Institute of Mechanics and Mechanical Engineering  of Kazan Scientific Center RAS, Kazan, Russia
3Birsk Branch of the Bashkir State University, Birsk, Russia
Keywords: gas hydrate, diffusion, heat transfer, aquatic gas solution
Pages: 537542

Abstract >>
The solution was obtained for a problem of gas hydrate growth in water with dissolved gas. The rate of hydrate formation depends on gas diffusion to the contact with gas hydrate. Three versions of problem configuration were considered: planar, radial, and spherical symmetry. For these cases, the values of the self-similarity coordinate were obtained: this parameter controls the growth of gas hydrate in water with gas dissolved and the level of top temperature in the hydrate zone. Analysis was performed for temperature fields related to heat release during hydrate formation.

DOI: 10.1134/S0869864316040065

Geometry of the vapor phase in explosive near-wall boiling-up

P.A. Pavlov
Institute of Thermophysics of Ural Branch RAS, Ekaterinburg, Russia
Keywords: boiling, condensation, fluctuation nucleation, wetting line, dry area
Pages: 543552

Abstract >>
Methods for calculating the geometric characteristics of the vapor phase in explosive wall boiling-up processes on a metal wall are analyzed. A monotonic growth of superheat in the liquid above the equilibrium evaporation temperature is specified. We show that the choice of the model for bubble interaction has a profound influence on the geometric characteristics which define the value of the heat flux. Computer simulation was employed to obtain the dependence of dry area on time in two interaction models. We have found that, for a model with instantaneous bubble coalescence, the dry area can be evaluated by the Kolmogorov formula using a correction factor for the most probable triple interaction. An approximation of the distribution length of wetting line over the lifetime of wetting-line segments is obtained. The possibility of using the obtained data for calculation of rapid condensation is analyzed.

DOI: 10.1134/S0869864316040077

Mathematical simulation of melting inside a square cavity with a local heat source

N.S. Bondareva1 and M.A. Sheremet1,2
1Tomsk State University, Tomsk, Russia
2Tomsk Polytechnic University, Tomsk, Russia
Keywords: melting, natural convection, heat conduction, Boussinesq approximation, laminar regime, numerical simulation
Pages: 553565

Abstract >>
Numerical simulation of transient melting regimes inside an enclosure in the presence of a local heat source has been carried out. Mathematical model formulated in terms of dimensionless variables such as stream function, vorticity, and temperature has been numerically solved by finite difference method. Effects of the Rayleigh number 4∙105 ≤ Ra ≤ 5∙107, Stefan number 2.21 ≤ Ste ≤ 5.53, and dimensionless time on velocity and temperature fields as well as on the local Nusselt number along the heat source surface have been analyzed in detail. The transient effects of the considered process at high values of the Rayleigh number have been identified.

DOI: 10.1134/S0869864316040089

Calculation of combined conduction-radiation heat transfer reduction using thick concentric spheres with temperature-dependent emissivity as radiation shields

F. Jabbari and S. Saedodin
Semnan University, Semnan, Iran
Keywords: radiation heat transfer, conduction, radiation shields, thick spheres, temperature-dependent emissivity, analytical study
Pages: 567574

Abstract >>
In this study, the rate of conduction-radiation heat transfer between two thick concen-tric spheres is analytically investigated because of the ever-increasing importance of radiation shield applications. The heat transfer rate, the percentage of reduction in heat transfer, temperature and emissivity of surfaces are calculated when one and two thick radiation shields are placed between two thick spheres. The calculations show that the use of a radiation shield with a lower emissivity is better than two radiation shields with a higher emissivity to reduce the heat transfer rate. In addition, optimal combinations of radiation shields with different materials are proposed.

DOI: 10.1134/S0869864316040090

The effect of constant electric field on zirconium oxidation by supercritical CO2

A.V. Shishkin and A.A. Vostrikov
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: zirconium, oxidation, zirconium dioxide, supercritical CO2, electric field
Pages: 575580

Abstract >>
The oxidation of zirconium by supercritical CO2 (20.2 and 14.1 MPa, and 823 K) results in the formation of a layer of the monoclinic ZrO2 and amorphous carbon. In the constant electric field (E = 293 kV/m) when a sample of irconium is the anode, the formation of amorphous carbon leads to a growth of leakage current and a twelve-fold increase in the rate of zirconium oxidation.

DOI: 10.1134/S0869864316040107

Evaluating the efficiency of thermo-electric conversion of heat from gas com-bustion in a small-scale system with counterflow heat exchange

S.S. Minaev1, I.A. Terletskii1, and  S. Kumar2
1Far Eastern Federal University, Vladivostok, Russia
2Indian Institute of Technology, Mumbai, India
Keywords: combustion, thermoelectricity, microsystems
Pages: 581589

Abstract >>
The efficiency of thermoelectric conversion of heat from gas combustion was evaluated in a small-scale system consisting of two channels with opposing gas flows and thermocouples located in the separating wall. Combustion occurred in the chamber fed with fresh mixture heated by combustion products through heat-conducting walls of the channel. In the channel walls, there were thermoelectric converters. It has been shown that in this system, the maximum conversion efficiency of heat from gas combustion may be close to the maximum efficiency of thermoelectric conversion calculated by the maximum acceptable working temperature of the hot side of the converter. This conclusion is valid in the case when the adiabatic combustion temperature of the gas mixture is below the maximum allowable operating temperature of the hot side of the thermoelectric converter. The considered system is promising for the burning of low-calorific gas mixtures and does not require additional energy for cooling the cold side of the thermoelectric con-verter.

DOI: 10.1134/S0869864316040119

Comparative analysis of turbulence model effect on description of the processes of pulverized coal combustion at flow swirl

M.Yu. Chernetskiy1,2,3, V.A. Kuznetsov1, A.A. Dekterev1,2, N.A. Abaimov3, and A.F. Ryzhkov3
1Siberian Federal University, Krasnoyarsk, Russia
2Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
3Ural Federal University, Ekaterinburg, Russia
Keywords: pulverized coal combustion, vortex furnace, RANS-methods, Reynolds stress model
Pages: 591602

Abstract >>
The effect of two-parameter k-ε and k-ω SST turbulence models and Reynolds stress model RSM on the description of processes at pulverized coal combustion in a fur-nace with a swirl burner is calculated in the present work. The mathematical model, which included the description of carrier phase motion based on the RANS approach, calculation of radiation transport through the P1 method, motion of particles based on the Lagrangian approach, combustion in the gas phase based on the hybrid model, and coal particle burning in the diffusion-kinetic approximation, was chosen for calculations. The calculated data were compared with experimental results on combustion of pulverized coal flame in the presence of flow swirl at the fire test bench with capacity of 2.4 MW. Comparative analysis showed that k-ε and k-ω SST turbulence models and Reynolds stress model have a little effect on distribution of axial and tangential velocities, temperature, and concentration of gases in the fur-nace.

DOI: 10.1134/S0869864316040120

Heat and mass transfer in a coal-water fuel particle at the stage of thermal treatment

V.V. Salomatov1, S.V. Syrodoy2, and G.V. Kuznetsov2
1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
2Tomsk Polytechnic University, Tomsk, Russia
Keywords: convective-radiative heat transfer, evaporation, filtration, pyrolysis, ignition, coal-water fuel (CWF)
Pages: 603612

Abstract >>
The problem of heat and mass transfer has been solved numerically under the conditions of coal-water fuel particle ignition. The concurrent processes of evaporation, filtration of steam, thermal decomposition of the organic part of coal, thermal and chemical interaction of steam and coke carbon, and oxidation of products of their reaction and volatiles by the external oxidizer have been taken into account. The scales of influence of individual thermophysical and thermochemical properties of coals on the characteristics and conditions of ignition of coal-water slurry have been determined. 

DOI: 10.1134/S0869864316040132

Plasma gasification of carbonaceous wastes: thermodynamic analysis and experiment

V.E. Messerle1,2, A.L. Mosse3, and A.B. Ustimenko4
1Institute of Combustion Problems, Almaty, Kazakhstan
2Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russi
3A.V. Luikov Heat and Mass Transfer Institute NAS, Minsk, Belarus
4Research Institute of Experimental and Theoretical Physics, Almaty, Kazakhstan
Keywords: waste, plasma gasification, synthesis gas, calculation, experiment
Pages: 613620

Abstract >>
Thermodynamic calculations of the plasma gasification process of carbonaceous wastes in air and steam ambient were carried out. A maximum yield of synthesis gas in such processes is predicted to be achieved at a temperature of 1600 K. On a specially developed plasma facility, plasma gasification experiments were performed for carbonaceous wastes. From the organic mass of carbonaceous waste and from its mineral mass, respectively, a high-calorific syngas and a neutral slag consisting predominantly of ferric carbide, calcium monosilicate, silica and iron, were obtained. A comparison between the experiment and the calculations has shown a good consistency between the data.

DOI: 10.1134/S0869864316040144

Study of aerodynamic structure of flow in a model of vortex furnace using Stereo PIV method

I.S. Anufriev, P.A. Kuibin, E.Yu. Shadrin, D.K. Sharaborin, and O.V. Sharypov
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: vortex furnace, particle image velocimetry, vortex core structure
Pages: 621624

Abstract >>
The aerodynamic structure of flow in a lab model of a perspective design of vortex furnace was studied. The chamber has a horizontal rotation axis, tangential inlet for fuel-air jets and vertical orientation of secondary injection nozzles. The Stereo PIV method was used for visualization of 3D velocity field for selected cross sections of the vortex combustion chamber. The experimental data along with total pressure minimum criterion were used for reconstruction of the vortex core of the flow. Results fit the available data from LDA and simulation.

DOI: 10.1134/S0869864316040156

Effect of viscosity on thermocapillary breakdown of a falling liquid film

D.V. Zaitsev1, A.A. Semenov1, and O.A. Kabov1,2
1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
2Tomsk Polytechnic University, Tomsk, Russia
Keywords: film breakdown, threshold heat flux, thermal capillarity, viscous liquids
Pages: 625628

Abstract >>
Thermocapillary breakdown of a liquid film flowing due to gravity over a vertical plate with a heater of 150×150 mm is studied in a wide range of liquid properties (in particular, dynamic viscosity at the initial temperature varies from 0.91×10-3 to 16.9×10-3 Pa×s) and film Reynolds number (Re = 0.15-53.5). It is found that liquid viscosity has a significant effect on the threshold heat flux corresponding to film breakdown. To take into account the effect of liquid properties, the breakdown criterion traditionally used in literature was modified. This allowed successful generalization of all data obtained.

DOI: 10.1134/S0869864316040168