№ 3 (2025)

Liquid jet flows in the presence of a ventilated cavity with a negative cavitation number are investigated. The studies carried out in the Institute of Mechanics of Moscow State University show that under certain conditions cavitation-induced self-oscillations can occur in the hydraulic system with highly intense pressure fluctuations. The results of an investigation of the axisymmetric model of a pulsed jet generator with liquid jet outflow through a central orifice in a diaphragm and gas blow from the periphery beyond the diaphragm are presented. The two-phase medium outflow was realized through a convergent conical nozzle. The influence of the generator parameters and the distance to a wall (screen) on the efficiency of its operation is investigated. A narrow range of comparatively small blowing, in which high-frequency pressure oscillations are recorded, while the amplitude of impact pressure pulses on the screen is considerably higher than the amplitude of pulses in high-frequency generation regimes, is revealed. This flow regime can be due to the development of two-phase structures on the unstable jet boundary interactioning with the convergent nozzle walls. The evidence for the possible existence of this flow regime has been given by the solution of the plane problem of interaction between a finite jet and an inclined plate for different pressures on the jet surfaces. The problem was solved exactly using the methods of theory of functions of a complex variable for quasi-doubly-periodic theta functions.

Supersonic viscous gas flow past the upper surface of a blunt finite-length plate is considered in the interaction regime. The temperature factor effect on the pressure disturbances initiated by mounting a wedge at the plate end, the aerothermodynamic flow characteristics, and the disturbance propagation upstream are investigated. Numerical calculations are carried out within the framework of the solution of the stationary two-dimensional Navier–Stokes equations.

The stability of spatially periodic flows of homogeneous and stratified fluid is investigated with regard for bottom friction. The Galerkin method with three basis Fourier harmonics is used to solve the stability problem. A system of ordinary differential equations for the amplitudes of the Fourier harmonics is formulated. A solution to the linearized version of the system is obtained and an expression for the increment of disturbance growth is found. It is established that at the nonlinear stage of development the exponential growth of linear disturbances is replaced by the regime of establishing steady-state periodic disturbances in form of closed cells. These disturbances reduce the averaged horizontal velocity of the flow. Analytical expressions for the spatial period and amplitude of steady-state disturbances are obtained.

Free internal waves in a uniformly stratified fluid are considered in the Boussinesq approximation with regard for the Earth’s rotation. It is shown that the dispersion relation, derived with taking into account the horizontal component of the angular velocity of the Earth’s rotation at constant wave frequency, is reduced to the canonical equation for second-order curves in the plane of horizontal wave numbers. If the wave frequency is higher than the inertial frequency and less than the Brunt-Vaisälä frequency, the frequency isolines are ellipses. If the wave frequency is higher than the buoyancy frequency, then the frequency isolines are hyperbolas; and if the wave frequency is equal to the Brunt-Vaisälä frequency, then the isolines are two straight lines parallel the direction to the east. The vertical wave momentum fluxes are obtained as functions of the direction of wave propagation. It is shown that the fluxes are maximum in absolute value when the wave propagates to the north or to the south. A comparison of the vertical momentum fluxes of internal and sub-inertial waves at the same length and the maximum wave amplitude is carried out. It is shown that the vertical momentum flux of sub-inertial waves is higher than that of internal waves and weakens with weakening of stratification.

The vortex structures formed behind a delta wing in supersonic flow are considered. The dependence of these structures on the angle of attack and the oncoming flow Mach number is studied, together with their effect on the aerodynamic properties of a downstream straight wing. The regimes with M = 2 and 3 and α = 10°, 14°, and 20° are considered. The numerical data are obtained using the hybrid multiprocessor supercomputer K-60 system in the Common Use Center of the Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences.

The results of numerical study of the flow in a channel with an annular radial jet injected along the Coanda surface are given. To describe the flow of the gas medium, the two-dimensional axisymmetric Reynolds-averaged Navier–Stokes (RANS) equations are used in combination with equations of the semi-empirical − −ω SST turbulence model. The effect of the total pressure and the width of radial jet on the velocity and static pressure distributions is studied and changes in the local structure developed at the sub- and supercritical pressure in the jet are described.