Home – Home – Jornals – Advanced Search

A systematic analysis has been performed for many-years experimental data obtained in the wind tunnel T-203 (SibNIA) for testing the models of passenger and transport aircraft for the case of harmonic oscillation at the pitch angle for low subsonic velocities. The key features of behavior of aerodynamic derivatives coefficients and dependencies of current values of normal force coefficient and longitudinal moment coefficient on the angle of attack have been demonstrated for the stalling modes of streamlining. It was demonstrated that at near-critical angles of attack, we have a strong dependency of aerodynamic derivatives of pitch moment on the normalized oscillation frequency for the range of natural values; this makes the traditional mathematical model of aerodynamic loads (uses the aerodynamic derivatives at fixed frequencies of oscillation)  unfit for the considered scope of experimental tasks.

An experimental study of the flow over a single open shallow cavity is reported. Pressure fluctuations were measured using two cavity models at free-stream Mach numbers 0.3, 0.5, and 0.6. At certain conditions, resonance of acoustic waves inside cavity with disturbances in the shear layer over cavity was observed. Pressure fluctuation characteristics were analysed using Fourier, wavelet, and Hilbert - Huang transforms. Those methods have allowed us to accurately examine the transition of the flow over cavity into resonant state.

An open-type pressure recovery system (PRS) for chemical oxygen-iodine laser was designed and fabricated. As a first stage, an active diffuser was used in which the ejecting gas supply was organized through nozzles disposed around the channel periphery. The second stage was a supersonic ejector. Numerical simulation data for the viscous turbulent flow with heat release through the diffuser gas-dynamic channel, and also data obtained by testing the active diffuser in operation on a model facility equipped with a vacuum chamber, are reported. The obtained data were used to develop a full-scale setup with exhaust of laser gas into the atmosphere; this has allowed us to optimize the performance characteristics of the setup and substantially improve its mass-dimensional characteristics. Special attention was paid to parameter matching and synchronization of laser start with the operation of PRS components.

On the basis of experimental research and numerical simulation, flow regularities in a 50-millimeter hydrocyclone with injector have been revealed. It is shown that the injected liquid comes out mostly through the lower outlet. At tangential injection toroidal vortex impeding main flow discharge through the lower outlet is formed.

A physical-mathematical model of the heat and mass exchange process and condensation capture of sub-micron dust particles on the droplets of dispersed liquid in a sprayer scrubber is proposed and analysed. A satisfactory agreement of computed results and experimental data on soot capturing from the cracking gases is obtained.

The process of wave formation in the falling films of liquid nitrogen was simulated numerically in the framework of the hydrodynamic model of Kapitsa ⎯ Shkadov. The typical wave characteristics were calculated for different inlet Reynolds numbers. The effect of parameters of small initial perturbations on wave formation was studied. Satisfactory agreement of numerical simulation results and experimental data is shown.

The surface tension effect is introduced according to the continuum model for the surface tension force. A smooth variation of the mollified function of the volume fraction (the color function) across the interface between immiscible fluids occurs due to the convolution of the original color function with the smooth kernel function. The polynomial eighth-degree kernel formulated for plane two-dimensional flows bounded by solid walls or symmetry planes is tested for the Rayleigh - Taylor instability problem.

The mathematical modelling of unsteady regimes of natural convection in a closed cylindrical region with a heat-conducting shell of finite thickness was carried out in the presence of a local heat source under the conditions of convective heat exchange with the ambient medium. The mathematical model was constructed in dimensionless variables "stream function - vorticity vector - temperature" in the cylindrical coordinate system. The influence of the Rayleigh number, 10⁴ ≤ Ra ≤ 10⁶, of the unsteadiness factor 0 < τ < 300, of the thermal conductivity ratio λ_2,1 = 5.7·10⁻⁴, 4.3·10⁻², and the energy source sizes on both local characteristics (streamlines and temperature fields) and on the integral complex (the mean Nusselt number on typical boundaries) was analysed in detail. Thermohydrodynamic peculiarities due to the geometry of the object of research were established.

The single-phase Stefan problem was modelled numerically in approximation of the classical solution in application to melting of a flat semitransparent sample by radiant-conductive technique in a wide range of emissivity of the phase transition front.

Measurement results for temperature dependences of kinematic viscosity in Bi-Pb melts are presented. Measurements were carried out in the temperature range between liquidus and 1400 K. The distinctive feature of experiments was their performance at heating after sample melting and further cooling. On the experimental temperature dependences of kinematic viscosity the values of viscosity at fixed temperature and activation energy of viscous flow have been calculated. Special attention was paid to non-coincidence of the curves obtained at heating and cooling. The specified anomaly is explained by the concept of metastable micro-coherence of the studied melts.