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The goal of the study is to study the gas-dynamic structure of a supersonic underexpanded jet in the presence of a liquid spray as applied to the topic of gas-liquid nozzles. The wave structure is detected by methods of shadowgraphy and adaptive transparency visualization. Laser Doppler anemometry is used to measure the spray velocity and also to determine its concentration and droplet size. It is found that the flow in the two-phase core is qualitatively different from the gas jet flow. The transformation of the Mach disk in a wide range of gas flow regimes and liquid flow rates is studied. A crucial role of the gradient region of the jet in the vicinity of the Mach disk in the process of liquid atomization is demonstrated.

Two diametrically opposite internal grooves were introduced in the diverging section of a supersonic nozzle. Experiments were conducted to find the effect of grooves at three different nozzle pressure ratios (NPRs), i.e., 3.6, 5.5, and 7.2 and comparisons were made with circular jet without grooves. Data reported here are for a design exit Mach number of 1.8 with an area ratio 1.44. Results are presented as pitot pressure decay along the extended geometric center-line of the nozzle and the radial distribution of pitot pressure at various axial ( x ʹ =1, 3, 5, and 8) locations. Empirical relations have been developed to identify the lengths of various regions involved in the pitot pressure decay (along X -direction). Groove effectiveness was used as a parameter to find the effect of grooves on the jet decay characteristics. The jet from grooved nozzle exhibited totally different results compared to that from plain circular nozzle. Results show that grooves played a more significant role at overexpansion condition of the nozzle than at under-expansion case. Schlieren flow visualization technique was used to capture the shock cell structure of the jets for the same NPRs and it was found that the structure of the jet emanating from the grooved nozzle was highly distorted. To understand decay characteristics, supersonic core length and the pitot pressure decay lengths for 50 % decay and 90 % decay were determined from the pitot pressure data along the extended centerline of the nozzle. A significant reduction in spatial pressure fluctuations and supersonic core length were observed at overexpansion condition of the nozzle when grooves were introduced.

The fluid dynamics of a water fluid jet with supercritical state parameters outflowing from a high-pressure vessel through a thin nozzle is investigated. The numerical modeling of the jet was carried out using a system of equations for a gas-vapor-liquid mixture which includes the conservation laws for mass, momentum and energy formulated in with one-pressure, one-velocity, and two-temperature approximation. The simulation takes into account the contact heat and mass transfer processes of evaporation and condensation under equilibrium condition using a modified solver reactingTwoPhaseEulerFoam within the OpenFOAM free open package. The process of barrel shock formation in a supersonic boiling jet with developing the Mach disk is demonstrated. It was found that the outflow process is accompanied by formation of vortex zones near the jet symmetry axis and this induces periodic pulsations in pressure and mass velocity inside the jet. Finally, this generates the acoustic pulses series preceding the main jet flow. Justification of reliability for the applied numerical method implemented through the OpenFOAM package solver is offered through comparing the numerical and analytical solutions for the Sedov problem of a strong point explosion in a two-phase gas-droplet mixture (for the planar case). The comparative analysis of simulation and the experimental photography for the supersonic nitrogen jet ejected from a cylindrical nozzle of a high-pressure reservoir is presented. The numerical results obtained using the OpenFOAM package demonstrate a satisfactory agreement with analytical solution and experimental data.

Heat exchange devices involving confined heated cylinders in crossflow require wake stability to minimize hydraulic losses, which are typically accompanied by a considerable loss in heat transfer. To address this problem, passive wake control for laminar flow past a cylinder is introduced in the form of wavy channel walls around the cylinder. The resultant effects on heat transfer and drag are investigated in detail for a range of Reynolds numbers (Re = = 20 - 200), blockage ratios ( b = 0.5 - 0.9) and Prandtl numbers (Pr = 0.25 -100). For the given range of parameters, it is shown that the wavy channel reduces cylinder drag by a minimum of ~ 36 % and a maximum of ~ 95 %, at the expense of ~ 8 % and ~ 40 % loss in heat transfer, respectively, compared to the plane channel. Thermal-hydraulic performance of the wavy channel compared to the plane channel for Pr = 0.744, is improved by ~ 14 % for b = 0.5 and ~ 160 % for b = 0.9. Therefore, the performance enhancement brought about by the wavy channel provides an appropriate trade-off between drag reduction and heat transfer loss.

The problems of interaction between gas dynamics and combustion are considered using the well-known database of experimental results on the boundary layer with ethanol combustion. Gas dynamics is represented by streamlines, combustion is represented by isotherms. The influence of an increased degree of air turbulence (up to 18%), acceleration in a narrowing channel, and the influence of the height of a flame stabilizing fin (3 and 6 mm) on the flow structure in individual cross-sections and in the boundary layer as a whole are studied. It is shown that immediately behind the barrier, where the signs of kinetic reaction of the gas mixture are manifested, the streamlines intersect, and during combustion in a narrowing channel with low air turbulence, the isotherms and streamlines become equidistant near the flame front, as in the case of diffusion response. Mass transfer on the liquid fuel surface remains conservative to changes in the gas-dynamic parameters of the air flow.

The present paper aims to investigate the effect of longitudinal curvature on film cooling performance through a single row of cylindrical holes. Four different longitudinal curvature cases are considered by changing the curvature heights. Detailed film effectiveness distributions are presented for several blowing ratios. The ANSYS CFX has been used for this computational simulation. The turbulence is approximated by a shear stress transport (SST) model. The numerical results are compared with experimental data.

Temperature distribution was measured during the development of natural convection in a vertical rectangular cavity 364 mm high, 185 mm wide and 40 mm deep, filled with a lead-bismuth melt and with the temperature difference maintained on its vertical sidewalls. The initial temperature difference was set by changing the electric power supplied to the heated wall, and, accordingly, by changing the heat removed from the opposite wall. The measurements were carried out in a quasi-stationary regime of free convection, when the flow parameters and temperature distributions over the cavity cross-section were constant for several hours. As a result of the performed measurements, the temperature profiles along the width and depth of the rectangular cavity were obtained.

The processes of heat transfer in air and liquid plate-finned heat exchangers of a thermoelectric cooling system are considered. The flow modes in interfin channels are analyzed, and the local heat-transfer coefficients are determined. From the numerical solution of the two-dimensional thermal-conduction problem, the dependences of the thermal resistances of the heat exchangers on their geometric parameters are obtained. The influence of thermal resistances on the cooling capacity and on the coefficient of performance of the thermoelectric cooling system is determined. Optimization of heat exchangers in terms of fin thickness and interfin spacing has been performed.

A numerical method of inductive drag reduction by means of improving the aerodynamic performance of the tip elements of lifting systems is presented. The method allows one to optimize the distribution of the intensity of free vortices at the wing tips in the Trefftz plane for a prescribed lift force and unchanged base wing geometry. Optimization calculations of various lift systems are performed, including the STR-40DT short-range airplane developed at the Chaplygin Siberian Scientific Research Institute of Aviation (SibNIA). Good agreement of the numerical and experimental results is noted.

The results of the formation of overstocked 15-year pine stands (with initial density of trees 35.6 thousand per ha) in the Krasnoyarsk forest-steppe the thinning aimed at reducing their density with keeping only the trees of a certain cenotic position (dominant, co-dominant and suppressed) in order to obtain information about the possible equalization of their forest inventory indicators in the process of their growth are presented. It was found that after thinning the dominant trees stand had density of 4.3 thousand per ha, had the best growth characteristics (mean height and mean diameter) and upheld that tendency through the whole observation period. After 7 years mean diameter of dominant trees increased from 4.8 ± 0.1 to 9.4 ± 0.2 cm, mean height increased from 4.8 ± 0.1 до 8.1 ± 0.1 m. Stem timber volume increased 5.0 times to the value of 141.63 m³ per ha, relative density - from 0.51 to 1.27. Stand density for co-dominant trees decreased to 6.6 thousand per ha after the thinning. The mean diameter of co-dominant trees increased 2.6 times and amounted 6.1 ± 0.1 cm, the mean height increased from 3.4 ± 0.1 to 5.7 ± 0.1 m. Stem timber volume increased from 7.92 to 60.06 m³/ha, relative density increased 3.7 times (1.00). After the thinning the suppressed trees underwent a long (1-2 years) adaptation period, had disproportional growth in height and decreased growth in diameter (relative height 244). Stand density for suppressed trees pine Pinus sylvestris L. decreased to 6.3 thousand per ha after the thinning. The mean diameter of the suppressed trees after 7 years after the thinning changed from 0.9 ± 0.1 to 4.2 ± 0.1 cm, the mean height - from 2.3 ± 0.1 to 3.8 ± 0.1 m. Timber volume increased from 1.09 to 17.23 m³ per ha, relative density increased from 0.07 to 0.69.