Home – Home – Jornals – Advanced Search

The influence of the shape of the jet head on its impact on a wall covered with a thin layer of liquid has been studied. The conditions characteristic of the impact of the jet arising on the surface of a cavitation bubble upon its collapse near the wall have been considered. It has been established that changing the shape of the jet head can lead to a significant change in the size of the area of maximum loading of the wetted wall and in the magnitude and pattern of loading. In particular, with an increase in the degree of sharpening of the jet head, the pressure on the wall decreases and its spatial distribution becomes more uniform. Dependences of the maximum pressure and integrated wall load on the jet shape were obtained.

The influence of the dimensionless angular and linear parameters of interaction of water droplets shaped as a sphere, an ellipsoid, and a conventionally liquid disk on the characteristics (regimes) of their collisions in air (rebound, coagulation, spreading, or fragmentation) is studied by using a system of high-speed video recording. Conditions of stable realization of this interaction are determined. Charts of the corresponding regimes are constructed and compared with available data. The characteristic sizes, the number of liquid fragments formed in collisions, and total areas of the evaporation surface are calculated. It is demonstrated that the liquid surface area in the case of collisions of conventionally liquid disks is significantly (by several times) greater than that in the case of spherical droplets.

Three-dimensional deformation of two bubbles and bubbles in a cluster in an ideal incompressible fluid exposed to an acoustic field is investigated using the boundary element method for potential flows. The dependence of the dynamics of two interacting bubbles on the frequency and amplitude of the acoustic field and the distance between them is studied. The values of the parameters of the acoustic field and the cluster for which jets are formed and the bubbles are deformed or remain spherical are determined. The behavior of two central bubbles in a structured cluster exposed to an acoustic field with different frequency and amplitude is investigated as a function of the distance between the bubbles of the cluster. A comparative analysis of the deformation of the investigated bubbles in the presence and absence of adjacent bubbles is performed.

Theoretical model describing the movement of particles of saline water in oil flowing over a larger droplet of fresh water has been developed to solve the problem of cleaning oil from salts. The results of calculations of the effect of the radius and the initial velocity of a drop of fresh water on the coagulation of fresh and saline water droplets are presented.

The nonstationary process of extracting material from a porous body simulated by a system of semi-infinite capillaries into a moving liquid is studied; the transfer rate of the material in the flow is a linear function of the cross flow coordinate. The case where the liquid velocity at the interface becomes zero is considered. It is assumed that the diffusion in the flow is quasi-stationary. Analytical dependences at the boundary of the porous material and the flow region are found for mass transfer characteristics of practical interest (concentration, diffusion flow, total diffusion flux and the total yield of the target component through the cross section of the porous body).

Stress relaxation in a nano-sized rod containing structural defects in the course of constant-rate uniaxial straining is studied, and the reasons for the onset of this phenomenon are determined. Under the assumption that structural defects can serve as carriers of irreversible deformation of a higher level than dislocations, the problem is solved by the molecular dynamics method. It is found that stress relaxation is accompanied by the transition of the entire system to a steady state with a deeper potential minimum as compared to the system energy before the stress relaxation process, resulting in a temperature increase and reduction of the strain tensor components.

The stress state in the neighborhood of the common edge of a freely supported composite wedge-shaped plate under transverse load has been studied. The materials of the constituent plates are cylindrical orthotropic. The problem is solved using the classical theory of anisotropic plates. Equations are derived for the hypersurface which, in the space of physical and geometric parameters, is the boundary of the region of parameters for which the neighborhood of the common edge of the composite plate is in a low-stress state (the stresses at the points of the common edge of the composite plate are limited).

A variational principle is used to study the oscillations of a reinforced thin cylindrical shell with a filler under axial compression with allowance for friction on their contact surface. The dependences of frequencies of natural oscillations on the number of waves in a circumferential direction are constructed.

Nonlinear elasticity model in current state variables is used to study the plane strain dynamics of an incompressible body, and a system of nonlinear equations of displacement and pressure is obtained. In the absence of bulk forces and in the assumption of quadratic elastic potential, the resulting equations that describe plane waves, self-similar motions, and stress fields in these motions are solved and studied. It is shown that several solutions of a certain type are possible both in wave and self-similar cases.

The dynamic buckling of an elastic cylindrical shell with a general boundary condition (composed of stiffness and damping) under an axial impact by a rigid body is considered. A dynamic equation is derived to obtain the axial stress and radial displacement of the shell. Then, by substituting the results into the energy equation, the critical condition for the dynamic buckling of the shell is obtained. The influence of the general boundary condition on the critical velocity of the impactor is analyzed. The results reveal that the boundary condition exerts no effect on the dynamic buckling of the shell before the stress wave becomes reflected from the fixed end face of the shell. After reflection, the critical velocity decreases with increasing impactor mass and stiffness, but increases with increasing damping. At times smaller than the instant when the stress wave reaches the fixed end face of the shell, the dynamic buckling occurs earlier at greater values of damping and stiffness. After stress wave reflection, the earlier dynamic buckling is observed at smaller values of damping and stiffness.