Journal of Applied Mechanics and Technical Physics最新文献

Based on the volume-of-fluid (VOF) multiphase model and the fluid-structure interaction (FSI) model, combined with the overset grid technology of the STAR-CCM+ software, a computational model for the oblique entry of truncated projectiles into water is established. The hydrodynamic characteristics and structural response characteristics of the projectile for various water entry angles are calculated and analyzed, and the evolution law of cavitation is determined. The numerical results are found to be in good agreement with experimental data.

The propagation and disintegration of nonlinear internal waves at the hydrophysical test site of the Pacific Oceanological Institute FEB RAS on the shelf of the Sea of Japan have been studied in the summer-autumn period for a number of years. The mechanisms of generation and propagation of nonlinear internal wave trains due to internal tide decay have been determined by continuous measurements of the vertical temperature and velocity distribution at depths of 20–60 m using bottom stations and by a regular study of the distributions of the main hydrodynamic characteristics along selected paths. In addition, other short-period sources of thermocline deformation have been detected that can be attributed to the propagation of bottom and surface vortex structures. The high spatiotemporal resolution of the temperature field in the neighborhood of bottom stations made it possible to reveal the fine structure of wave perturbations of various types. Multilayer shallow-water models for wave-train propagation have been developed and verified using the results of field and laboratory experiments.

An algorithm for solving an inverse problem of forming a ribbed panel made of the AK4-1 alloy (analog of the AA2018 and Al-Cu₂-Mg₂-Ni₁ alloys) at a temperature of 200°C is proposed. The problem is reduced to solving a sequence of auxiliary direct problems on the stress-strain states of the elements of the panel structure. The structural elements are taken to be T-beams subjected to pure bending. The resultant moment for obtaining a desired shape is calculated by the Nelder–Mead simplex algorithm. Two approaches to obtaining goal-shaped parts are considered: deformation under the plastic flow condition and under the creep condition. The material models used in the study take into account the difference in the mechanical properties under tension and compression, as well as the presence of damage accumulated in the material. The calculations are performed with allowance for elastic springback of the part after load removal.

The classical two-dimensional Cauchy–Poisson problem for an ocean modelled as an incompressible fluid with an elastic bottom is considered here. In accordance with the linear theory, the problem is formulated as an initial-value problem for the velocity potential in the fluid region, dilation potential, and rotational potential in the elastic medium below the fluid region. The Laplace transform in time and the Hankel transform in space are used in the mathematical analysis to obtain the form of the free surface depression and ocean bed vertical displacement component in terms of multiple infinite integrals. These integrals are evaluated asymptotically by the method of steepest descent. Variation of the ratio of the ocean bed amplitude to the free surface amplitude for different forms of the prescribed initial axially symmetric surface depression or the impulse for different values of elasticity parameters is investigated. The results obtained in the study are compared to the analytical solution of the problem in the case with a rigid bottom.

The possibility of changing the silicon surface morphology at certain glow discharge parameters is shown. It is established that oxidation is the main process influencing the surface morphology during glow discharge plasma treatment. As a result of processing in the investigated parameter range, various stages of the surface oxidation process are observed: the formation of a uniform oxide layer and the formation of nano- and microstructures of silicon oxide. It is shown that these processes lead to surface modification, which acquires stable hydrophilic and superhydrophilic properties.

This paper presents a three-dimensional direct numerical simulation of the chaotic dynamics of the free surface of a dielectric fluid placed in an external tangential electric field. The physical model includes the effects of energy pumping (external force), energy dissipation (viscosity), and surface tension. As the external electric field strength increases, a transition from the turbulence of dispersive capillary waves (at zero field) to anisotropic electrohydrodynamic wave turbulence is observed. In the strong field limit, where the fluid motion becomes highly anisotropic, a cascade of small-scale capillary waves is formed that propagates perpendicular to the external field direction. In this regime of motion, a new turbulence spectrum occurs that differs from the classical spectrum of capillary turbulence.