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The full Navier-Stokes equations are used to study the linear stability of plane Poiseuille flow in a channel with the lower wall corrugated along the flow, due to which the flow has two velocity components. The generalized eigenvalue problem is solved numerically. Three types of disturbances are considered: flat periodic (the Floquet parameter is zero), flat doubly periodic (finite values of the Floquet parameter), and spatial. Neutral curves are analyzed in a wide range of the corrugation parameter and Reynolds number. It is found that the critical Reynolds number above which disturbances that increase over time appear depends in a complex way on the dimensionless amplitude and period of corrugation. It is shown that in the case of flow in a channel with corrugated wall, three-dimensional disturbances are usually more dangerous. The exception is the small amplitude of corrugation, at which plane disturbances are more dangerous.

This paper presents the results of a statistical analysis of the turbulent structure in a free bubbly jet at a Reynolds number of 12500 based on PIV measurements of the carrier-phase velocity. The distributions of higher-order statistical moments for velocity fluctuations (skewness and excess coefficients) and the energy spectra of turbulence for single-phase and gas-saturated jets were obtained after applying the procedure of statistical filtering to instantaneous velocity fields. The influence of the dispersed phase (bubbles with an average diameter of 0.8 mm) with a volume gas fraction of 0, 1, 2, and 3% for the specified characteristics of the continuous phase was analyzed.

A description of a small climatic wind tunnel designed for studying the icing processes at the Khristianovich Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences is presented, The use of such a wind tunnel offers a possibility not only of studying the physics of the icing process, but also of testing methods of anti-icing control, validating numerical methods used for calculating the icing processes, etc.

The longitudinal structures generated by external vortical and thermal waves in subsonic and supersonic boundary layers have been studied. Particular attention is paid to setting boundary conditions on the external boundary of the boundary layer. It has been found that disturbances of the longitudinal velocities inside the boundary layer can be several times higher than the amplitude of the external vortical wave. The generation efficiency decreases with increasing Mach number. It has been shown that the influence of thermal external waves on the flow structure in the boundary layer is much weaker than the influence of the vortex structure of the flow

The influence of various physical mechanisms at the stage of collapse of a vapor bubble and the subsequent formation of a cumulative jet in the process of laser-induced boiling near the end of a thin waveguide immersed in a cold liquid is studied numerically. Depending on the intensity of evaporation, three process modes are identified and described.

Three-dimensional numerical simulations of the air flow in the full human bronchial tree in situations of obstructive and chronical pulmonary diseases are performed. Based on the previously developed three-dimensional analytical model of the lower respiratory airways, the air distributions in the lungs (from the trachea to alveoli) in situations with lung injuries and bronchial asthma are calculated. Breathing modeling is based on a numerical technique of stage-by-stage computations, which allows one to avoid the loss of solution accuracy caused by the difference in the bronchus scales; moreover, the time needed to calculate the air flow in the lungs can be reduced by several times by using this technique.

The results of numerical simulation within the framework of a two-dimensional shallow water model of the interaction of a solitary wave with a stationary semi-submerged body with a rectangular cross section are presented. A comparison of these results with the results of calculations based on a model of irrotational three-dimensional flows showed that for small amplitudes of the incident wave, the modeling accuracy is satisfactory. It has been established that neglecting the diffraction of a solitary wave on the surface of a cylinder when using a one-dimensional model of shallow water leads to overestimates of the maximum values of the wave runup on the edge of the cylinder and the force loads on it.

A high-velocity flow in an axisymmetric nozzle containing a central body and pylons is studied. The influence of the geometry of the main and additional pylons on the gas-dynamic and thrust characteristics at the nozzle exit in the flow regime with n_pr= 2.25 ( n_pr is the ratio of the pressure in the settling chamber to the ambient pressure) is determined. Azimuthal nonuniformity of the flow at the nozzle exit is detected. The maximum azimuthal nonuniformity is observed in the wake behind the pylons. It is shown that a three-dimensional transonic flow is formed in the nozzle duct with the pylons mounted in the minimum free-area cross section; local supersonic regions closed by weak shock waves are formed in this flow. It is found that the formation of such a shock wave structure is responsible for nozzle thrust reduction by 12%.

Approximations of the profiles of the longitudinal and transverse velocity components in the boundary layer calculated for the flows around a swept wing and a body of revolution by means of solving the full Navier-Stokes equations and using the boundary layer profiles from the self-similar one-parameter family of the Falkner-Skan-Cooke profiles and two-parameter family of profiles proposed by Gaster are compared. A significant advantage of using the approximation of the numerical profiles near three-dimensional separation by profiles from the two-parameter family is demonstrated.

The process of occurrence of an internal crack of a mixed type (I and II fracture modes) in the wall of a pipe made of an ideal elastoplastic material under the action of combined tensile (compression) and bending loads has been studied. The process of destruction of such materials is described using a modified Leonov-Panasyuk-Dugdale model, which uses an additional parameter - the diameter of the plastic zone (prefracture zone width). The case of complex loading is considered, when the crack trajectory is necessarily curved, therefore the angle of the trajectory break is determined using a force integral criterion based on the asymptotics of the stress field in the vicinity of the crack tip. To obtain critical fracture parameters, a two-parameter (dual) strength criterion is proposed in the case of a complex stress state. An analysis of the parameters included in the resulting analytical model was carried out. The dimensionless geometric parameters of the structure are found numerically using the finite element method. Diagrams of quasi-brittle fracture have been constructed.