Journal of Applied Mechanics and Technical Physics最新文献

The amplification of a shock-wave pulse transmitted through a sand layer is investigated as a function of layer thickness. It is shown that, as the thickness of the sand layer increases to a certain value, the amplitude of the probing pulse first increases and then decreases. The formation of pressure peaks occurs almost simultaneously throughout the entire sand layer.

This study examines the behavior of a three-component electrolyte in a microdevice using a spherical ion-selective granule under an applied electric field and pressure gradient. In practical applications, one of the electrolyte components corresponds to charged analyte particles with an initially low concentration. It is shown that the analyte concentration in the granule wake can be increased, with the enrichment factor being independent of the initial concentration. The physical mechanism of this phenomenon is described, and the values of the potential and pressure differences and the characteristics of the electrolyte components and the granule required to achieve this enrichment are provided.

Integration in Lagrangian variables was performed for a submodel of steady-state ideal gas motions with constant pressure in the flow region. A general solution was obtained for the invariant submodel of stationary-type rotational isobaric motions. Examples of helical gas motions with constant pressure are considered.

This paper presents the results of developing a concept for a vacuum aerodynamic facility based on the AT-303 vacuum wind tunnel at the Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch of the Russian Academy of Sciences. The layout, geometry, design features, and advantages of the proposed facility are described. Estimates of its operating parameters and performance characteristics are provided.

This paper presents a computationally efficient ray-tracing boundary treatment for the lattice Boltzmann method, which accurately handles complex geometries using only discrete surface meshes, eliminating the need for analytical curvature descriptions. The key innovation is a robust geometric intersection algorithm that leverages ray-segment (2D) and ray-plane (3D) tests to precisely locate boundary points, requiring no pre-processing while maintaining second-order accuracy via the conventional bounce-back scheme. Validations—including 2D cylinders (Re = 100), NACA0012 airfoils (Re = 500), and 3D spheres—show exceptional agreement (≤3% error in drag with 64–128 vertices; <10% deviation from high-fidelity benchmarks). The method’s simplicity, accuracy, and seamless CAD compatibility make it ideal for industrial LBM applications in the automotive, aerospace, and energy sectors.

This paper presents the results of a numerical simulation and stability analysis of the flow in a boundary layer on a plate with a surface microrelief. The microrelief consists of long slots (recesses) oriented at various angles relative to the incoming flow at a Mach number M = 2. The slots under consideration have a depth-based Reynolds number Re_h ≈ 1000 and a width that is small compared to the instability wavelength. Numerical simulation is used to determine the specific features of the flow past a plate with inclined slots and to study the evolution of time-localized disturbances. A stability analysis of the flow is performed within the framework of linear theory, based on averaged profiles of the boundary layer parameters. The computational results show that the presence of inclined slots induces a crossflow in the boundary layer, which leads to an increase in the disturbance growth rates. The obtained data are in good agreement with experimental observations and explain the destabilizing effect of inclined slots on the boundary layer.

An experimental study of hydraulic fracturing in thick-walled concrete cylinders with a central hole is conducted using a high-pressure fluid test rig. The cylinders are made of sand-based concrete using GTs 50 alumina cement. Estimates of the ultimate pressure obtained from local and nonlocal failure criteria are compared with the experimental data. It is shown that satisfactory agreement between the calculated ultimate loads and the experimental failure data under a nonuniform stress field is achieved using nonlocal failure criteria.

One-dimensional unsteady flows of an incompressible non-Newtonian viscoelastic fluid between parallel plates are considered using the Johnson–Segalman model with multiple relaxation times. A distinctive feature of the model under consideration is its hyperbolicity over a wide range of flow parameters. A general model of this type with (n) relaxation times (modes) is obtained, and a change of variables is made, allowing the model equations to be written in a conservative (divergent) form. A series of calculations of unsteady flows in various regimes is performed, showing the occurrence of the shear banding effect as the mean flow velocity increases. The wall shear stress versus shear rate relation and the flow rate versus pressure gradient relation were obtained for steady plane Couette and Poiseuille flows, respectively. The resulting curves were validated by comparison with several sets of experimental data. The structure of steady solutions exhibiting shear banding, obtained as a numerical limit of unsteady solutions, is investigated. A selection rule is formulated for steady-state solutions that are asymptotically attained in unsteady numerical simulations. The hysteresis phenomenon under cyclic changes in flow velocity is analyzed.

This paper presents the results of experiments on fabricating a composite material based on PTS-1 titanium reinforced with a TiN phase at volume fractions of 4, 8, 12, 21% by hot pressing. A powder mixture of titanium and titanium nitride was mechanically treated in a high-energy planetary ball mill and sintered at temperatures of 1200, 1300, and 1400°C. The sintered samples contain primary (alpha )-Ti and (beta )-Ti phases and secondary (delta )-TiN and (varepsilon )-Ti₂N phases. An increase in the titanium nitride concentration induces a (beta leftrightarrow alpha ) polymorphic transformation, forming an (alpha )-Ti–TiN eutectoid. Raising the sintering temperature increases the grain size of the titanium (beta )-phase by 250%. Due to the high concentration of titanium nitride, the structure of the composite undergoes a transformation, increasing the relative density by 99%, the material hardness by 97%, and Young’s modulus by 63%.

The mechanical properties of a new diamane-reinforced copper composite were studied by molecular dynamics simulation. The Young’s modulus and tensile strength of the Cu–diamane composite were determined to be 117 and 16.4 GPa, respectively. These values can be increased by increasing the number of diamane layers in the composite.