Home – Home – Jornals – Thermophysics and Aeromechanics 2013 number 1

Stability of the flow of the heated liquid film is studied in the presence of the thermocapillary effect. To describe the waves in the film, the integral model is used. According to results of linear analysis of stability, the thermocapillary effect expands the area of instability only at low Peclet values Pe, and at high values of Pe, the instability area narrows. Wave evolution in the film on a substrate with the fixed temperature was simulated numerically. Results of numerical simulations agree with the linear theory of stability.

The problem of stabilized combined motion of the gas flow and liquid film in a microchannel under the action of local heating with consideration of evaporation processes was set in selected variables. The exact solutions to the linearized problem were derived. The analytical formulas for calculation of the film thickness stabilized below the heater and the total rate of liquid evaporation were obtained. The technique of approximate calculation of total heat transfer is shown. Exemplary calculations are presented.

The solutions of the Laplace equation involving the diverging infinite series are used in the classical works at the analysis of the problem of the gravitational rise of a gas bubble in a tube filled with ideal fluid (the Taylor bubble). In the present work, an approximate method is proposed for a correct analysis of the above problem. The ideal fluid flow around a body of revolution in a tube is constructed by the method of the superposition of elementary solutions. The satisfaction of the free surface condition in the critical point neighborhood and the passage of the main parameter to the limit lead to the sought expression for the dimensionless velocity of the gas bubble — Froude number.

Experimental values of complexes of aerodynamic derivatives were obtained in a wind tunnel and analyzed for subsonic flow of a passenger aircraft model with harmonic oscillations on the rolling and yawing angles. It was demonstrated that for near-critical angles of attack, the complexes of aerodynamic derivatives taken for rolling and yawing have a string dependency on the normalized oscillation frequency. It was proven that this dependency is driven by derivatives with respect to angular velocities and angular acceleration. A mathematical model for aerodynamic loads was developed; it can be applied for aircraft flight dynamic problems and has satisfactory approximation to experimental aerodynamic characteristics.

In the present paper, we discuss results of an experimental study of performance characteristics of a 3D inlet with a flow-metering device at free-stream Mach numbers М = 1.75 and 2. The inlet was designed using gas-dynamic design methods. The initial external compression in the inlet is achieved using a V-shaped body called a waverider. The inlet is provided with a special device for its starting, also permitting regulation of the internal channel cross-sectional area in the throat region with the help of paired rotary panels, throat doors. The flow-rate and total-pressure loss characteristics in the throat of the model inlet were determined as functions of the degree of opening of the throat doors.

In the present paper, we discuss a procedure for designing of cylindrical air inlets for high flight speeds with the use of V-shaped bodies for forming a plane flow with an initial oblique compression shock. In design regime, characteristics of such air inlets can be obtained by means of simple calculations performed in a broad range of governing parameters. The difference between the performance characteristics of a typical cylindrical inlet in design and off-design flow conditions was elucidated with the help of 3D numerical calculations.

The work deals with the two-phase flow investigation. The computations were done for a continuous coagulation model within the framework of the phenomenological multi-fluid model of the medium. A conclusion was drawn that the diminution of the particles size leads to a reduction of two-phase losses in the nozzle unit of the solid-fuel engine.

The temperature dependence of the density of eutectic alloy of lead–potassium system (90.7 at. % Pb) was investigated using gamma-ray attenuation technique over the temperature range 293–950 K of solid and liquid states. The density changes during solid–liquid phase transition were directly measured for the first time. The approximating dependences for the density have been obtained, and a comparison of the data of this work with previously published results has been carried out. The reference tables for the temperature dependences of thermal properties of the alloy have been compiled in the entire examined range, and their errors have been estimated.

A molecular dynamics method was used to calculate the pressure p* and the internal energy e* of a liquid and a crystal in stable and metastable states in a system of 2048 particles, which interaction is described by a modified Lennard—Jones potential. For the liquid phase, calculations were performed along 13 isotherms from the range of reduced temperature T*=0.35-3.0, and for the crystal phase, along 16 isotherms from the range T*=0.1-3.0. The thermal p*=p*(ρ*, T*) and caloric e*=e*(ρ*, T*) equations of state for liquids and crystals have been constructed. The parameters of crystal–liquid phase equilibrium have been determined from the conditions of phases coexistence at positive pressures and in the region of negative pressures, where the coexistent phases are metastable. The spinodal of a stretched liquid has been approximated. It has been found that with a temperature decrease the metastable extension of the melting line meets the spinodal of the liquid phase. The point of their meeting, the endpoint of the melting curve, is the point of termination of crystal–liquid phase equilibrium without the onset of identity of the phases.

Results of mathematical simulation of the ceramics molding process by the hot casting method are presented. The mathematical model describes the motion of beryllia liquid thermoplastic slurry in a form-building cavity subject to solidification. Velocity and temperature profiles providing homogeneous properties of the beryllia ceramics in the process of molding by the hot casting method are obtained.

Measuring results for axial distribution of gas temperature of high-frequency torch discharge burning in the air at atmospheric pressure are presented. The distribution of electric field over the discharge axis was calculated based on the model of discharge in the form of heterogeneous electric line of finite length. It is shown that the experimentally observed linear character of electric field change along the discharge axis is conditioned by its axial heterogeneity.

Possibilities and limitations of the optical diagnostic methods for small-size (about 1 μm) droplets in the gas-droplet flows are discussed. Here we show the possibility for restoration of the functions of droplet distribution and droplet average size on the basis of measurements of ultradispersed particle parameters formed from microdroplet flows after droplet evaporation.

Speed of sound in the gaseous refrigerant R-409A has been measured by ultrasonic interferometer in the tem-perature range from 293 to 373 K and at pressures from 0.05 to 0.58 MPa. The experimental uncertainties of the temperature, pressure, and speed of sound measurements were estimated to be within 20 mK, 4 kPa, and 0.1–0.2 %, respectively. On the basis of the obtained data, the isobaric molar heat capacity was calculated for the ideal-gas state. A comparison of the obtained results with the calculated speed of sound on the basis of REFPROP program was carried out.