Home – Home – Jornals – Advanced Search

The processes of spraying, spatial propagation, and deposition of aerosol particles generated impulsively using the energy of energetic materials. Such aerosols are produced for the purpose of decontaminating harmful gases or aerosol formations. A mathematical description of the evolution of the decontaminating aerosol cloud is proposed, and the results of experiments on spraying an aerosol of titanium oxide particles are presented.

This paper presents the results of calculations of liner implosion without the formation of shock waves under the influence of a current up to 70 MA and a magnetic field induction up to 20 MGs (magnetic pressure up to 16 Mbar) in devices with a disk explosive magnetic generator. It is shown that during deep implosion of two-layer (Cu-W) and (Cu-Ta) liners, the shockless pressure in tungsten and tantalum can reach 40 Mbar (hydrodynamic cumulation). The inner part of the liner, whose mass is more than 32% of its total mass, may remain in a solid-state dynamically strengthened state at a temperature of its copper skin layer up to 38 eV.

The impact interaction of composite projectiles with thin metal plates is studied, and a method for evaluating the ballistic limit and residual velocity of the projectile is proposed. The composite cylindrical projectile consists of a deformable highly porous nose part and a hard non-deformable tail. The velocity of the projectile is considered in the range 200-850 m/s. The problem is solved numerically in a two-dimensional axisymmetric formulation. The motion of the medium is described using the Lagrange method. The calculation results are compared with experimental data. It is shown that the results obtained are in good agreement with the results of calculations using available analytical models and experimental data.

An analytical (exact) solution of equations of a two-dimensional boundary layer of a non-Newtonian viscous fluid in the case with mass transfer is obtained with the use of the Ostwald-Reiner power-law model in a particular case with n = 2 (dilatant fluid). It is noted that the apparent viscosity in this case is described by an expression that coincides with the equation for turbulent viscosity of a Newtonian fluid derived by the Prandtl mixing length model. For the particular case under consideration, it is found that there is an analogy between the flows of a non-Newtonian fluid and a Newtonian fluid with turbulent viscosity.

The laminar--turbulent transition in transonic flows is studied with the use of thin-film surface hot-wire probes. For determining oscillations recorded by the thin-film probe in the boundary layer, coherence spectra are constructed between the data obtained by the thin-film probe and by the hot-wire probe, which was used to perform measurements across the entire boundary layer. Based on the analysis of these spectra, it is demonstrated that the most accurate and complete data are obtained by the thin-film probe in the intermittency region.

The dynamics of an acoustic signal passing through a bubble curtain has been studied by mathematical modeling. The case is considered where the gas (methane) inside the bubbles is under hydrate formation conditions. The effects of the hydrate formation process, the initial radius of bubbles, and the volume gas fraction on the attenuation coefficient and phase velocity of the wave propagating in a deep-water sea (located at a large depth) bubble curtain are investigated. The reflection and transmission coefficients of acoustic waves at the boundaries separating single- and two-phase regions are obtained. It is found that the hydrate formation process increases the wave attenuation coefficient by more than two orders of magnitude at low frequencies (below 1 kHz).

Distributions of the amplitude of controlled disturbances in space and time and their frequency-wave characteristics are obtained from experimental results on weakly nonlinear development of the wave train in the region of a stationary wake inside the boundary layer on a flat plate at the Mach number M = 2. A stationary streamwise disturbance is generated by a pair of weak oblique shock waves. Controlled disturbances are inserted into the flow by a local high-frequency glow discharge located inside the model. The development of controlled disturbances is analyzed on the basis of the linear theory of hydrodynamic stability. Typical resonant wave triplets are identified. It is found that flow inhomogeneity suppresses the mechanisms of interaction of controlled disturbances.

The results of a numerical study of heat transfer in a gas-droplet turbulent flow behind a single square barrier with variations in the initial mass concentration and diameter of dispersed phase particles are presented. When flowing around a barrier, adding droplets to the flow leads to a significant intensification of heat transfer (almost twice) compared to a single-phase air flow. It is shown that when a two-phase flow flows around a transverse barrier, the coordinates of the maximum heat transfer intensity and the flow reattachment point differ by approximately 12%. An increase in the barrier height leads to a decrease in heat transfer intensity.

For a nonlinear parabolic reaction - diffusion system, solutions are constructed and investigated that have the form of a diffusion wave propagating in a medium at rest with a finite velocity. For the first time, for cases of spherical and cylindrical symmetry, the problem of initiating a diffusion wave by boundary conditions specified on a sphere (circular cylindrical surface) is considered. A theorem of existence and uniqueness of a solution in the class of analytic functions is proved. An exact solution is constructed, which is presented in the form of explicit formulas. A step-by-step iterative algorithm is proposed, based on the collocation method and expansion in radial basis functions. Numerical calculations are performed, for the verification of the results of which the exact solution is used.

The influence of spanwise-uniform roughness elements (streaks) on the transition to turbulence in the boundary layer on a swept wing with domination of crossflow instability in the presence of unsteady and steady free-stream vortices is studied. The measurements are performed for rectangular (in the plane parallel to the flow and normal to the wall) roughness elements shaped as streaks of different heights, which have two different widths in the chord direction. The experiments are performed in a low-turbulence wind tunnel at low subsonic velocities of the incident flow with the use of hot-wire anemometry. The studies are conducted in the range of unit Reynolds numbers (based on the streamwise component of velocity at the boundary layer edge at the beginning of the rough surface region) 0.687 ·10⁶ - 1.568 · 10⁶ 1/m. The results are obtained in 76 regimes of measurements for two types of free-stream vortex disturbances generated by two turbulizing grids: with domination of unsteady disturbances and combination of steady and unsteady disturbances.