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For the first time, various collapse scenarios have been identified for a low-density hemispherical cavity formed by gas heating during the combustion of a pulsed submillimeter electric discharge near a dielectric surface. Two distinct collapse mechanisms were observed: one driven by the loss of stability of the cavity boundary in the contact zone with the surface, and another driven by instability in the part of the cavity farthest from the surface. It was established that both “bubble” collapse scenarios occur stochastically under invariant experimental conditions. Using the PIV method, velocity field distributions in the cavity region were obtained at different time instants. Based on high-speed velocity imaging data, it is hypothesized that the specific collapse scenario realized is determined by the shape of the conductive channel at the moment of electrical breakdown.

Two methods for obtaining crack-free joints by explosive welding of low-ductility 30KhGSA steel with varying hardness have been experimentally investigated: 1. the use of welding regimes that produce a flat, non-wavy interface zone; 2. the application of a ductile interlayer, which allows the use of welding parameters corresponding to the mechanical properties of the interlayer material. A characteristic length scale was constructed to distinguish flow regimes of the material with varying deformation intensities, enabling estimation of the thicknesses of the plastic strain localization band and the region of intense plastic deformation. It is shown that the minimum interlayer thickness that avoids fragmentation during joint plastic deformation is determined by the thickness of the strain localization band. For the first time, the feasibility of explosive welding using an interlayer produced by detonation spraying has been demonstrated.

This paper presents several aspects of the application of physics-informed neural networks using the example of a two-dimensional steady-state problem of flow around an obstacle, modeled by the Navier-Stokes equations. The influence of the activation function, quantitative parameters of the training dataset, adaptive regularization, and adaptive meshing on the quality and accuracy of the solutions is investigated within a fixed neural network architecture. The interrelation between these factors and the modeling quality is analyzed to identify optimal conditions for improving the accuracy and stability of the solutions.

A method is presented for estimating the average sound velocity in the annular space of a mechanized well, which is subsequently used to determine the gas-liquid interface (dynamic level). The proposed approach takes into account the distribution and variation of the gas composition, thermobaric conditions, and the presence of phase transitions. The key stage in solving the problem is determining the gas composition distribution from the wellhead to the gas-liquid interface. The approach is based on the laws of thermodynamics for equilibrium processes. The method has been tested on more than 100 wells across several oil fields in Western Siberia. The convergence of the analytical approach was verified by comparing its results with field experimental measurements of sound velocity obtained by echo sounding.

The primary goal of this study is to investigate the mechanism of forced transition to turbulence in the laminar boundary layer of a swept wing, dominated by crossflow instability, using spanwise-periodic arrays of cylindrical turbulators. Measurements were carried out using hot-wire anemometry in a low-turbulence wind tunnel at ITAM SB RAS (Novosibirsk) at low subsonic freestream velocities on a model of a 25-degree swept wing. The Reynolds number based on cylinder height ranged from 565 to 3613. All major characteristics of the boundary layers were obtained, which are essential for constructing transfer functions for jumps in integral boundary layer parameters-important for numerical simulation of flows over swept wings with turbulators. The turbulence spectra were shown to be consistent with the Kolmogorov and Heisenberg laws. Empirical formulas by Falkner and Hama for the evolution of integral parameters in a three-dimensional boundary layer were verified and refined. This article represents Part 2 of the study.

The propagation of a wave with a step profile and a finite-duration impulse from a liquid into a porous medium saturated with either a bubbly or a “clean” liquid is studied. The effect of such waves on a solid wall with a saturated porous layer located in front of it is investigated. It is shown that the numerical results qualitatively agree well with known experimental data.

The frequency spectrum and mode shapes of flexural vibrations of rectangular plates in contact with a liquid or gas are determined. An expression is derived for the distributed transverse load on a plate hinged along its contour. The plate surfaces are in contact with a medium characterized by varying density and pressure. The medium may be either compressible or incompressible. The effects of mean pressure, curvature of the mid-surface, and the added mass of the gaseous medium on the plate’s bending behavior are evaluated.

The deformation of an elastic body containing two thin anisotropic inclusions intersecting at a right angle is studied based on a mathematical model with unilateral boundary conditions. The inclusions intersect at an interior point of one of them, forming a T-shaped configuration within the elastic medium. One of the inclusions is debonded from the matrix, resulting in a crack. Boundary conditions on the crack surfaces are specified in the form of inequalities. To solve the problem numerically in the region with a cut, a domain decomposition method with the Uzawa algorithm is used. To determine the displacement functions of the semi-rigid inclusion, a method based on decomposing the space into a direct sum of subspaces is applied.

This paper investigates a three-dimensional normal contact problem involving an elastic wedge with one traction-free face and an infinite periodic straight-line system of rigid indenters arranged along the wedge edge (dihedral angle). The system of indenters induces infinite normal displacements on the wedge face (a special case being the half-space). To regularize the divergent kernel of the integral equation governing the contact pressures, an additional periodic system of normal forces is introduced outside the contact region. This system is aligned with the array of indenters and shares the same period. The forces in the regularizing array are equal in magnitude and directed opposite to those applied by the indenters. Two regularization cases are considered: one where the regularizing force chain is applied off the wedge edge (first case), and another where it acts directly on the edge (second case). To solve the regularized integral equation, the Galanov numerical method is employed, which simultaneously determines both the contact area and the contact pressure distribution.

Solutions of the diffusion wave type are constructed and analyzed for a system of two degenerate nonlinear parabolic equations. The problem of initiating a diffusion wave is considered for an arbitrary form of nonlinearity in the system and for arbitrary directions of motion of the zero fronts of the two target functions. A theorem is proved on the existence of four different analytical solutions depending on the propagation directions of the zero fronts. A new numerical method is proposed, which for the first time enables the solution of the problem for the case of oppositely directed motion of the two zero fronts. A new exact solution is explicitly constructed and used to verify the computational results. A numerical experiment is performed, demonstrating the convergence of the numerical method and its effectiveness across various problem parameters.