Thermophysics and Aeromechanics

Kraiko, A. N.

2022 Thermophysics and Aeromechanics

doi: 10.1134/s0869864322060014

It is shown that the “new methodologies of processing and using” of the results calculated for rotating detonation engines, as well as those of recent measurement of forces acting on the rotorless ramjet models in “hot” and “cold” tests in supersonic test benches, which are developed and promoted by S.M. Frolov and V.I. Zvegintsev with their colleagues, are incorrect.

Zvegintsev, V. I.

2022 Thermophysics and Aeromechanics

doi: 10.1134/s0869864322060026

The traditional approach to measuring the thrust of air-breathing jet engines (ABJEs) was proposed by B.S. Stechkin in 1929. In this approach, the thrust is determined as the difference between the momenta of the gas flows at the engine inlet and outlet. This approach involves some methodological and terminological problems. Based on the critical analysis of available concepts, the present article proposes a new approach to the determination of ABJE thrust in the form of the reduction of the initial drag of the aircraft + ABJE assembly observed when the propulsion system operates with fuel supply and energy release. For the thrust thus obtained, we propose using the term “real thrust”. It is shown that the proposed approach eliminates terminological problems and simplifies the technique for measuring the thrust characteristics of ABJEs. The paper considers various options in applying the proposed approach to the determination of the “real thrust” for different cases of using and modeling ABJEs, including the calculation of flight trajectories of ABJE-powered aircraft.

Pakhomov, M. A.; Philippov, M. V.; Chokhar, I. A.; Terekhov, V. I.

2022 Thermophysics and Aeromechanics

doi: 10.1134/s0869864322060038

We present the experimental results on the thermal efficiency in a wall gas jet blown through inclined cylindrical holes along a smooth surface, and when a secondary flow is blown through cylindrical holes into a transverse trench. The thermal efficiency fields of the wall jet were measured using an infrared camera. In the case of blowing into a trench, the experimental data are characterized by an insignificant influence of the injection parameter on the thermal efficiency of the wall jet for all the trenches under study. It has been established that an increase in the trench depth leads to an increase in the thermal efficiency of the wall gas jet. The maximum increase in thermal efficiency is achieved for a trench with relative depth h/d = 0.94. The data of measurements presented are compared with the experimental and numerical results of other authors for the cases of blowing through the holes into a transverse trench.

Kornilov, V. I.; Popkov, A. N.

2022 Thermophysics and Aeromechanics

doi: 10.1134/s086986432206004x

Results of experimental and numerical studies of the properties of a turbulent boundary layer modified with a control action in the form of distributed air blowing through a high-technology perforated wall are presented. The wall is part of the surface of an elongated axisymmetric body in a low-velocity gas flow. The Reynolds number Re** based on the momentum thickness δ** ahead of the perforated region formed by holes 0.14 mm in diameter with microchannels with a small aspect ratio is 2660. The area-averaged blowing coefficient Cb varies in the interval 0–0.00885. As the streamwise coordinate increases up to the distance of 550δ** from the blowing region, the local friction is seen to decrease consistently; the greatest value of the local friction is 64 % directly in the blowing region in the case of the maximum blowing intensity.

Raschektaeva, E. P.; Stankus, S. V.

2022 Thermophysics and Aeromechanics

doi: 10.1134/s0869864322060051

The thermal conductivity of the R-32/R-125 (15/85) mixture was investigated in the range of temperatures of 305–411 K and pressures of 0.1–1.8 MPa. Measurements were carried out by the stationary method of coaxial cylinders. The error of the experimental data on thermal conductivity was 1.5–2.5 %, and the measurement errors of temperature and pressure did not exceed 0.05 K and 4 kPa, respectively. A generalizing equation for calculating the thermal conductivity as a function of pressure and temperature was obtained. The thermal conductivity on the dew line and in the ideal gas state was determined.

Dutova, O. S.; Bezverhii, P. P.

2022 Thermophysics and Aeromechanics

doi: 10.1134/s0869864322060063

Using the previously established dependence of the excess viscosity on the internal energy density, a simple low-parameter equation was obtained to describe the krypton viscosity coefficient in a wide range of state parameters. It was shown that the proposed low-parameter equation for calculating the viscosity coefficient of liquid and gas allows for reliable extrapolation beyond the limits of the studied area.

Yatskikh, A. A.; Afanasev, L. V.

2022 Thermophysics and Aeromechanics

doi: 10.1134/s0869864322060075

The paper presents the results of numerical simulation for the development of localized disturbances emerging from a single source or two synchronous sources of laminar boundary disturbances allocated on the plate with the flow at Mach number M = 2 (variants for different distances between two sources were considered). Simulation was performed using the FlowVision software package at the flow parameters typical of T-325 wind tunnel (ITAM SB RAS). The problem was studied in the range of the linear development of disturbance. The study demonstrates that, depending on the distance between the sources, the generated disturbances might either enhance or decay downstream. The frequency-wave analysis of disturbance structure was performed. Two separated synchronous local sources generate the disturbances with wave spectra: these spectra exhibit nodes and antinodes and their positions depend on the distances between two sources.

Terekhov, V. I.; Terekhov, V. V.; Chokhar, I. A.; Lun, N. Yan

2022 Thermophysics and Aeromechanics

doi: 10.1134/s0869864322060087

A technique is described and the results of an experimental study of the aerodynamic structure of turbulent streamlining, velocity fluctuations, and pressure fields on the surface of a single trench dimple located on the wall of a flat rectangular channel are presented. The trench dimple cross section is a cylindrical segment with hemispheres at its edges. The measurements were carried out with a two-component laser-Doppler anemometer at two angles of the dimple inclination relative to the flow direction φ = 0 and 45°. The development of the flow in the direction transverse to the trench, as well as along it, was studied. The fundamental difference between the velocity fields and their fluctuations in a trench located normally and at an angle to the flow is shown.

Sorokin, D. V.; Shatilov, D. A.; Andryushchenko, V. A.; Makarov, M. S.; Naumkin, V. S.; Smovzh, D. V.

2022 Thermophysics and Aeromechanics

doi: 10.1134/s0869864322060099

The paper is the study of electric resistance of a graphene layer washed by a liquid with different flow rate parameters. Experiments demonstrate that if the fabricated composite (graphene upon a PET/EVA polymeric substrate) is submerged into distilled water, the sample resistance increases by 120 %. Meanwhile, the flow of liquid near the graphene layer decreases this gain in the electric conductivity. The effect offers a general design of a flow rate sensor based on the graphene layer taken as a flow-sensitive matrix. The study demonstrates that this design of graphene flow sensor (tested for distilled water) exhibits a linear dependency of the sensor resistance on the flow rate.

Molochnikov, V. M.; Mikheev, A. N.; Mazo, A. B.; Kalinin, E. I.; Klyuev, M. A.; Pashkova, N. D.

2022 Thermophysics and Aeromechanics

doi: 10.1134/s0869864322060105

Results of an experimental study and direct numerical simulation of the steady flow in a channel branching region modeling the proximal anastomosis of femoral artery are reported. The Reynolds number was Re = 1500, which value corresponded to the maximum blood flow during the period of heart contractions. The ratio of the rates of the liquid flows through the branch and main channel was a varied parameter. Regularities in the development of the flow structure in the main channel and in the branch region are revealed, with much attention having been paid to flow separation regions. The occurrence of secondary flows localized within the separation regions has been established. The ranges of the flow rate ratio at which flow turbulence signs appear in the mixing layer at the interface between these regions are identified.