|
|
2021 year, number 4
|
M.M. Katasonov, V.S. Kaprilenskaya, V.V. Kozlov, A.M. Pavlenko
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
Keywords: straight wing, flow separation, laminar-turbulent transition, suction for boundary layer, 3D rightness element on a surface
Abstract >>
A model of straight wing was used for study of the effect of distributed flow suction on the flow structure and on disturbance growth in the boundary layer past a single 3D roughness element installed on the wing surface (at Reynolds number Rec = 240 000). This kind of suction reduces the intensity of natural velocity pulsations by factor of 5. The acoustic-enhanced disturbance intensity drops by 90 times. The effect of distributed suction on the middle flow occurs due to eliminating the flow separation at the trail end of the wing. At the zone downstream the suction site, the boundary layer becomes laminar and uniform (two-dimensional) for the entire span of the wing.
|
|
A.S. Epikhin1,2, T.G. Elizarova3
1Ivannikov Institute for System Programming RAS, Moscow, Russia
2Bauman Moscow State Technical University, Moscow, Russia
3Keldysh Institute of Applied Mathematics RAS, Moscow, Russia
Keywords: numerical simulation, underexpanded jet interaction, shock-wave structures, regularized (quasi-gas dynamic) equations, QGDFoam, OpenFOAM
Abstract >>
The paper presents the results of numerical simulation of complex shock-wave structures arising from an underexpanded jets impingement on an inclined flat plate. The plate deflection angles equal to 45º, 60º, and 90º are investigated, which corresponds to different types of shock waves interference. The gas-dynamic characteristics are calculated using the OpenFOAM software package with the QGDFoam solver. This solver based on a system of regularized (quasi-gas dynamic) equations. The numerical simulation results of the flowfields and pressure distributions at the plate are compared against the results of the Kurganov -Tadmor scheme and with experimental data. The features of the applied numerical approach for simulation complex shock-wave structures with triplet points, contact discontinuities, and low-entropy flows are identified.
|
|
I.I. Mazhul
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
Keywords: numerical simulation, supersonic flow, rectangular channel, streamwise ribbed surface, streamwise vortex structures
Abstract >>
Results of numerical simulations of a supersonic flow in a channel with a rectangular cross section having a streamwise ribbed lower surface are reported. The channel contains a constricting input section, where the cowl lip generates a shock wave incident onto the lower surface, and a subsequent constant-area section. The present numerical simulations are performed for a viscous three-dimensional flow with the use of the Reynolds-averaged Navier-Stokes equations and k-w SST turbulence model. The computations are performed for the free-stream Mach number М = 4.
|
|
S.M. Dmitriev, A.E. Khrobostov, M.A. Legchanov, S.S. Borodin, A.A. Barinov, I.A. Konovalov, A.A. Chesnokov, M.A. Makarov
Nizhny Novgorod State Technical University n.a. R.E. Alekseev, Nizhny Novgorod, Russia
Keywords: concurrent flow, stratification, spatial conductometry
Abstract >>
This paper presents the results of experimental study for turbulent flow performed using a conductometry measurement system. Processing of experimental data produces the estimates for average tracer concentration in the cells of the conductometry sensor, the dispersion for parameter representation, as well as autocorrelation functions and the histograms of probability distribution functions for the measured signal. The experimental data was compared with the results of GEMIX benchmark, which has a similar problem statement and tailored for a study of isothermal and nonisothermal mixing processes (the outcome parameters are found using the PIV method). This comparison demonstrates matching for typical wavelengths concerning the ordered flow structures developing at the streams interface. We also observe compliance for turbulent kinetic energy profiles within the central region of experimental model. Meanwhile, the outer zones have a significant discrepancy with the GEMIX-calculated data. This can be explained by a difference in measurement methods and a higher spatial resolution of the PIV method exceeding that for the conductometry method.
|
|
S.A. Valger
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
Keywords: unstructured grids, polyhedral meshes, aerodynamics of urban developments, separation flows, software systems, ANSYS Fluent
Abstract >>
The issue of applicability of unstructured computational grids in the problems of numerical modeling of the aerodynamics of buildings is considered. The analysis of the computational performance and discretization errors on unstructured grids with polyhedral and tetrahedral forms of the grid element is performed on the test problem of the flow around square-section prism. The results of numerical modeling obtained on various types of grids are compared with experimental data on velocity profiles and turbulent kinetic energy in characteristic vertical and horizontal sections in the vicinity of the prism, as well as on the characteristic sizes of separation zones on the prism cover and behind it. When using a polyhedral computational grid, the calculation time is shown to be significantly less, compared to calculations on grids based on tetrahedra, while the calculation results qualitatively and quantitatively reproducing the experimental data. Non-stationary modeling on a polyhedral computational grid is carried out in this work using a vortex-resolving turbulence model. Calculations using the vortex-resolving approach allow refining the parameters of the recirculation zone behind the prism. The calculations are performed in the Fluent 2020R1 solver.
|
|
N.A. Pribaturin1,2, P.D. Lobanov2, V.V. Randin2, O.N. Kashinsky2, A.S. Kurdyumov2, M.A. Vorobyev2, S.M. Volkov2
1Novosibirsk Branch of Nuclear Safety Institute RAS, Novosibirsk, Russia
2Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: experiment, fuel assembly, fuel element, shear stress, spacer grid
Abstract >>
To assess the spacer grid effect on the liquid flow disturbance, the shear stress on the surface of a vertical rod - a fuel element simulator - was measured in seven-rod models of fuel assemblies differing in spacer grid sizes, diameter of rods (fuel element simulators), and relative distance between them. Data on axial distribution of shear stress are presented. An increase in the averaged and pulsation wall shear stresses directly behind the grid due to liquid flow disturbance and extinction of this effect far from the grid is shown. The results of this research can be applied to verify the design codes used in hydrodynamic predictions of reactors.
|
|
S.V. Klinkov, V.F. Kosarev, V.S. Shikalov
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
Keywords: cold gas spraying, heat transfer, surface temperature, nozzle velocity
Abstract >>
Results of a study of the evolution of substrate temperature during nozzle movement under cold gas spraying conditions are reported. A model for calculating the substrate temperature is proposed and verified. Calculated data for typical ranges of nozzle velocity, substrate thickness, and initial substrate temperature encountered in the spraying practice, were obtained. It is shown that there exists an optimum initial substrate temperature at which the variation of temperature in the spray spot proves to be minimal.
|
|
A.A. Rodionov1,2, S.V. Starinskiy1,3, Yu.G. Shukhov1, A.V. Bulgakov1,4
1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
3Novosibirsk State University
4Institute of Physics CAS, Prague, Czech
Keywords: pulsed laser deposition, thin films, non-stoichiometric silicon oxide, laser ablation in background gas
Abstract >>
The nanosecond laser ablation technique was used to synthesize thin silicon oxide films of various stoichiometry in vacuum and in a background gas. The local oxidation degree of specimens was evaluated using three different characterization methods. It was found that, on increasing the distance to the laser-plume axis, there occurred a monotonic increase in the oxygen content of the films due to their oxidation inhomogeneity. A profound increase in ablated mass, related with an increased reverse flow of substance to the target, was found to occur when the pressure of the ambient mixture was reduced from 60 to 20 Pa. A comparison was made of the oxidation efficiencies of the films heated at the stage of their synthesis and at the stage of annealing of already formed films. It is shown that the composition of the films could be controlled by varying the inert-gas pressure at the constant pressure of the chemically active component in ambient mixture.
|
|
M.Yu. Plotnikov1, E.V. Shkarupa2
1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
2Institute of Computational Mathematics and Mathematical Geophysics SB RAS, Novosibirsk, Russia
Keywords: Direct Simulation Monte Carlo simulation, atomic hydrogen, heterogeneous reactions
Abstract >>
Heat transfer between the surface of a heated wire and ambient gas within the framework of the two-step mechanism of heterogeneous dissociation of hydrogen is studied by the Direct Simulation Monte Carlo method. This mechanism includes four heterogeneous reactions and takes into account the occupancy of activation sites on the surface. Based on the heat balance analysis performed, a dissociation rate constant is proposed, which yields the values of the power spent on gas heating and heterogeneous reactions that coincide with experimental data. The influence of the dissociation rate constant on the occupancy of surface sites and also on the probabilities of dissociation, recombination, and adsorption due to particle-surface collisions is analyzed.
|
|
H.C. Zhang1, H. Chen2, L. Xiang2, Z.G. Zuo1, S.H. Liu1
1Tsinghua University, Beijing, China
2Aerospace Propulsion Institute, Shanxi, China
Keywords: cavitation instabilities, thermodynamic effect, Venturi pipe with cavitation
Abstract >>
It is known that thermodynamic effect of cavitation could not be ignored in liquids such as cryogenic liquids, refrigerants, and high temperature water. This effect could delay and suppress the further development of cavitation, thus improve the suction performance in cases of hydraulic machinery. However, the influence of thermodynamic effect on cavitation instabilities has not been adequately discussed. For this purpose, a series of systematically designed experiments of Venturi cavitation in a blow-down type cavitation tunnel have been carried out, using water as the working liquid at different temperatures. For the first time, the cavitation instabilities were analyzed and identified with controlled degrees of thermodynamic effect The mean cavitation length and three types of cavitation instabilities were recognized through an image post-processing method. A decrease of is observed with an in-creasing For all conditions, cavitation surge (system instability), cloud shedding, and oscillations of the attached cavitation length occur at small, middle, and large pressure recovery number ( ) conditions, respectively. The thermodynamic effect mainly influences the range of for different cavitation instabilities. Cavitation surge and transition from cloud shedding to oscillations of attached cavitation length shift to a lower with an increasing
|
|
A.Sh. Agazhanov, D.A. Samoshkin, S.V. Stankus
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: the alloy of zirconium and niobium E-110, phase transformations, thermal conductivity, thermal diffusivity, heat capacity
Abstract >>
A comprehensive experimental study of the thermophysical properties of the zirconium alloy E-110 (Zr-1 at. % Nb), which is used as a structural material for fuel rods of modern reactors, has been carried out. New experimental data on the thermal diffusivity a and the isobaric heat capacity cp in the temperature range of 293-1275 K have been obtained. Based on the measurement results, the thermal conductivity l for the a-phase of the alloy has been calculated. The estimated error of the obtained data is 2-4 %, 3-5 %, and 2-3 % for a , l , and cp , respectively. The comparison with the known literature data has been carried out. A table of recommended temperature dependences of all the studied properties has been developed.
|
|
R. Cao1, D. Yu2
1Northeast Electric Power University, Jilin, China
2Harbin Institute of Technology, Harbin, China
Keywords: reheat cycle, multi-staged fuel injection, hydrogen fueled scramjet, specific thrust, specific impulse
Abstract >>
Multi-staged fuel injection is a good choice for hydrogen fueled scramjet engine to overcome the restriction of thermal choke and over-temperature. From a thermodynamic perspective, the multi-staged fuel injection is the practical application of reheat cycle. A parametric performance model has been developed for the hydrogen-fueled scramjet with multi-staged fuel injection to analyze its performance. The key parameters which affect the engine performance of scramjet with multi-staged fuel injection are total combustor area expansion ratio, reheat times and distribution ratio of area expansion. These parameters were carefully analyzed to provide some direct and transparent results for engine designers. The results showed that the specific thrust of scramjet can be greatly improved by increasing the total combustor area expansion ratio and reheat times, and/or choosing an appropriate distribution proportion of area expansion ratio. The effect of increasing the total combustor area expansion is most obvious for performance enhancement.
|
|
V.G. Prikhodko, I.V. Yarygin, V.N. Yarygin
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: supersonic nozzle, discharge into vacuum, back flow, screen
Abstract >>
The features of the gas outflow into vacuum are considered. The possibility of reducing the back flows by locally increasing the ambient pressure in the region of the nozzle discharge edge is shown.
|
|
S.I. Shtork1,2, I.V. Litvinov1,2, E.Yu. Gorelikov1,2, D.A. Suslov1,2
1Novosibirsk State University, Novosibirsk, Russia
2Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: pico-hydroturbine, axial turbine, laser Doppler anemometer (LDA), swirling parameter, hydro-turbine efficiency
Abstract >>
The paper presents the results of detailed experimental studies of the flow characteristics behind the impeller of an air model of a propeller-type pico-hydroturbine with an impeller diameter of 0.1 m. Using the method of laser-Doppler anemometry, distributions of two components of averaged velocities and pulsations were measured under the conditions varying from partial load to severe overload. It is shown that when the regime of hydroturbine operating deviates from the optimal one, the flow at the impeller outlet becomes swirling. Based on the data obtained, the character of evolution of the integral swirling parameter, which determines the swirling flow state, has been revealed. A trend for a sharp increase in the swirling parameter with a decrease in the air flow rate was found. Due to this increase, the degree of swirling reaches quickly a critical level at which the vortex disintegrates with the development of a central dip in the axial velocity profile and displacement of the flow to the channel walls. With an increase in the flow rate, a slower increase in the swirling parameter takes place, which remains below the threshold value even for a large overload. As a result, the maxima of the tangential velocity are located near the flow axis, and the profile of the axial velocity remains uniform over the flow cross section. Information about the flow characteristics can be used when adjusting the hydraulic unit regime to optimal conditions and developing recommendations for expanding the range of regulation of the hydroturbine operation while maintaining high efficiency.
|
|
Yu.M. Kozlovskii, S.V. Stankus
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: superconducting tapes, Amperium, SuperOx, linear thermal expansion coefficient, relative elonga-tion, dilatometric method
Abstract >>
The results of a dilatometric study of the linear thermal expansion coefficient of superconducting tapes “Amperium” and “SuperOx” in the temperature range of 100-370 K are presented. Temperature dependences are obtained, and reference tables of recommended values of thermal properties are calculated. The effect of film deformation on the measurement results is investigated. The design of the sample holder, eliminating the tape bending is developed. The linear thermal expansion coefficient of the tapes is compared with the thermal expansion of the metal layers of the films. It is shown that the difference in the relative expansion in the temperature range from 100 to 293 K does not exceed 0.05 %.
|
|
Abstract >>
On August 7, 2021, the famous scientist, specialist in the field of viscous gas dynamics, Doctor of Physical and Mathematical Sciences, Professor Anatoly A. Maslov, turned 75 years old.
|
|
