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Supersonic gas-liquid jets of a coaxial atomizer at high liquid concentrations are studied experimentally. A complex of optical techniques is used for studying the droplet sizes: visualization and particle image velocimetry, laser Doppler anemometry, and Malvern Spraytec instrument. The research shows that the velocity and concentration profiles change with flow rate growth: an extended region with small droplet velocities appears behind the bow shock wave; in this case, the concentration decreases significantly slower than that at low liquid flow rates. A small increase in the jet energy at liquid flow rates greater than 100 l/h and a noticeable increase in the droplet size testify that the gas jet capabilities for breaking up the liquid in the described regimes are exhausted.

Experimental study was performed on dynamics of vapor bubble rising in the annular channel at subatmospheric pressure. The gas bubble is formed during boiling of an overheated degassed liquid in an annular channel restricted by two glass tubes with the diameters of 25 and 16 mm. It was demonstrated that the dynamics of vapor cavity while rising the vapor bubble in the annular channel demonstrates a qualitative difference from the dynamics for an ascending gas bubble. The behavior is similar to a Taylor vapor bubble behavior in a round tube with a small diameter. One of typical features of vapor cavity behavior in an annular channel is possibility of vapor cavity decay after bubble collapse during the pulsation flow mode.

Reflections of hydraulic jumps on shallow water are studied. Theoretical criteria of the transition between the regular and Mach reflections are derived, and it is shown that there is a domain of wave incidence angles where both types of reflection are possible. Numerical simulations reveal a hysteresis of this transition, which is consistent with theoretical predictions. It is shown that the hysteresis can be obtained by smoothly varying both the angle of the wedge generating the hydraulic jump and the free-stream Froude number.

This work examines the transition from kinetic to diffusion combustion using optical diagnostic methods. Experimental data were obtained on the temperature fields, composition and velocity of gas near the leading edge of a hydrogen flame flowing from a 2×20 mm slit into the air. The distribution of the rate of combustion products formation, intensity of heat release and pressure was obtained using the method of balances in equations of energy, momentum and matter transfer. It is shown that during the transition to diffusion combustion, heat release along the flame length decreases more slowly than the rate of water formation.

The problem of hydrodynamic stability of a boundary layer with diffusion combustion is formulated in the Dan-Lin-Alekseev approximation and at constant Prandtl and Schmidt numbers; it is reduced to solving a system of the tenth-order ordinary differential equations with homogeneous boundary conditions. With Lewis numbers equal to unity, it may be lowered to the eighth order. In the inviscid approximation, the stability problem is reduced to the integration of a single second-order differential equation. Based on the obtained stability equations and calculations of stationary flow parameters, the stability of a supersonic boundary layer with diffusive combustion on a permeable plate with hydrogen supply through its pores is studied for the first time by direct numerical modeling. With the Mach number M = 2, the possibility of flame flow stabilization is established using calculations. It is shown that within the framework of the inviscid theory of stability, it is possible to obtain quite reliable data on the maximum degrees of the growth of disturbances.

The paper studies the quality of water spraying by a pneumatic injection system designed for water injection into the input system of a piston internal ignition engine. The system consists of a two-cylinder piston compressor with compression of water-air mixture phase in the compressor’s cavities. The piston compressor has connection to the atomizer through long channels. The droplet sizes were measured through automatic image processing by the Shadow Photography method. The velocity field of droplets was measured by the 2D-PIV method . Experimental results demonstrated that the injection system offers a high quality of spraying for the air/water mass ratio higher than 0.46. The value of Sauter mean diameter was less than 31.1 µm.

The research considers the microwave treatment of snow-and-ice mass with the stages of heating and melting. A nonlinear mathematical model for two-phase Stephan problem was developed for the case of laminar set of dielectrics. We offer approximate analytical solutions for taking into account the thermophysical and electrophysical properties of layers; this approach allows parametric analysis.

The papers analysis the flow patterns for air flow around cubic-shaped buildings. Experimental and simulation data were compared for the flow problems with different scales. Geometry parameters for the models can be varied from 0.025 to 6 m, meanwhile the range of Reynolds number for considered data is from 10⁴ to 10⁶. The study proves that the problem is scalable one: this creates a foundation for running the lab-scale wind tunnel experiments.

Using an ultrasonic interferometer in the temperature range from 293 to 393 K at pressures from 0.13 to 1.5-2.8 MPa, the speed of sound U was measured in helium-xenon gas mixtures with a helium content of 60.34, 71.72, and 85.32 at. %. The measurement errors of temperature, pressure and speed of sound were ±20 mK, ±4 kPa and ± (0.15-0.30) %, respectively. By approximating the experimental data for each composition, equations were obtained to describe changes in the speed of sound as a function of pressure and temperature over the entire measurement range. The existing reference and experimental data on the speed of sound in inert gases and He-Xe mixtures were analyzed. A method for calculating U of mixtures with a helium content above 71.7 at. % He to a temperature of 1500 K and a pressure of up to 7 MPa was developed.

Numerical simulation was applied to the processes of heat and moisture transfer and for ice-water phase transition in a season-thawed soil layer. Analysis was performed for consequences of natural wildfire on the soil temperature and the thawing depth as a function of water retention by soil for the condition of Siberian permafrost zone. Calculations demonstrate that the permafrost thawing depth increases due to burnout of the top organic horizon. The quantitative indexes of natural wildfire impact depend on water retention properties of the upper organic horizon of soil.