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The flow in a nonuniformly rotating (librating) cylinder with ends symmetrically inclined relative to the cross section is experimentally investigated. Due to librations, inertial waves are supported; at certain frequencies, they are focused on a closed path, called a wave attractor. The velocity of the pulsation flow changes nonmonotonically with frequency and reaches its maximum value when the attractor takes a square shape. With an increase in the oscillation amplitude, new vorticity centers appear in a threshold way, corresponding to inertial waves with a frequency different from the libration frequency. The Fourier analysis of perturbations in the supercritical regime shows that, in addition to the fundamental frequency, the spectrum contains two additional harmonics that satisfy the triadic resonance condition.

The interaction of a step-like pressure wave with a spherical gas-liquid cluster in a cylindrical channel filled with a liquid has been studied numerically. It has been shown that the cluster generates a solitary pressure wave of large amplitude. The influence of a bubble cluster on the dynamics of multiple reflection of a pressure wave from the boundaries of the cylindrical channel has been investigated. The results of numerical calculations are in good agreement with experimental data

The paper reports the results of liquid-fuel model combustor calculations based on different numerical approaches to develop a verified simulation method of combustor operation. Both steady and transient studies were carried using different RANS turbulent models and the detached eddy simulation (DES) method, and their results were compared with experimental data obtained by optical methods. RANS and hybrid eddy-resolving DES approach. Conducted comparison of the obtained results with the data of the non-contact optical experiment. The results show that the the greatest differences experiment and calculations are observed for the near-axial flow field where recirlulation backflow is formed. This vortex structure can be properly resolved in a DES solution as well as in transient calculations based on the SAS SST model. The use of the above-mentioned approaches in combination with the flamelet combustion model provides maximum accuracy in predicting the parameters of a reacting swirling flow including velocity and temperature distributions in the combustion chamber

Results of simulations of supersonic turbulent flows in a channel with due allowance for conjugate heat transfer between the air flow and a copper plate modeling the sensitive element of a thermocouple are reported. Numerical simulations are performed for free-stream Mach numbers M_∞ 3, 4, and 5. It is shown that the simulation results agree well with experimental data obtained in a hotshot wind tunnel. It is found that the conjugate heat transfer with the model walls made of steel can be ignored at times of the order of 100 ms.

A generalized mathematical model for the non-isothermal filtration of natural gas in a porous medium and a modified quasi-stationary model of gas hydrate formation (deposition) in pipelines were used to solve a conjugated problem for the case of joint operation of the “gas-bearing reservoir-well” system and predict the changes in temperature, pressure, gas moisture content, and well flow area. It is found that the presence of a thick permafrost layer accelerates hydrate formation inside the well. It is shown that when taking into account the salinity of formation waters, the duration of complete plugging of the well with hydrates increases

In this study, nonlinear forced vibrations of a bimorph piezoelectric nanobeam are investigated by using the nonlocal elasticity theory. This nanoactuator is modeled using the Euler-Bernoulli beam theory. The Hamilton principle is used to obtain the equations of motion. The derived equations are discretized by applying the mode shapes of multi-span beams as test functions in the Galerkin decomposition method. The discretized equations are then solved using the perturbation method. A parametric study is conducted to show the significance of size effects on the dynamic behavior of nanoactuators. The results show that an increase in the nonlocal parameter leads to a decrease in the fundamental natural frequency of the nanobeam and to an increase in the response amplitude.

By solving the plane problem of the mechanics of a rod strip having a fixed finite-length section on one of its front surfaces, it has been shown that when studying deformation processes with consideration of the compliance of the fixed section, it is necessary to take into account the change in the stress-strain state parameters and the mathematical models used for their description. This change occurs across the boundary between the unfixed and fixed sections. Within the framework of the classical Kirchhoff-Love model, it is impossible to take into account the compliance of the fixed section of the rod. However, within the framework of the simplest refined Timoshenko shear model, this is possible if the section is fixed only on one of the front surfaces. Exact analytical solutions of two simplest linear problems of static transverse bending of a flat rod with fixed sections of finite length on one of the front surfaces are found. One-dimensional finite elements for modeling unfixed sections of flat rods and sections on one of the front surfaces were constructed using the refined Timoshenko shear model. Numerical experiments were performed, showing the necessity of taking into account the change in the rod strain-stress parameters across the boundary between the fixed and unfixed sections.

The boron nitride nanosheet (BNNS), a graphene-like structure with excellent mechanical properties, is one of the most promising candidates for a reinforcement element to design innovative nanocomposites. Herein, we have investigated the BNNS, which serves for surface enhancement of the aluminum matrix via molecular dynamics simulations. The results show that the boron nitride nanosheet coating enlarges the critical yield strength, hardness, and modulus of elasticity. With an increase in the number of boron nitride layers, the strengthening effect is more significant. Meanwhile, a higher system temperature degrades the interfacial energy and weakens the mechanical properties of the BNNS/Al systems.

The problem of stability of cylindrical shells made of composite material, taking into account momentum and nonlinearity of their subcritical stress-strain state. Geometrically non-linear the stability problem is solved by finite element methods and linearization of Newton -Kantorovich. Critical loads are determined in the process of solving a nonlinear problem using Sylvester's criterion. Hypothesized Timoshenko finite elements of composite cylindrical shells natural curvature, in the approximation of displacements of which in explicit form, rigid displacements are highlighted, which significantly affects solution convergence. The stability of the circular cylindrical shell made of polymer composite material, under combined loading by torsional and bending moments and internal pressure. Studied the influence of the laying method monolayers, non-linearity of deformation, internal pressure on critical loads at which buckling occurs shells

This paper proposes a model of static transverse elastic deformations of a magnetic gel sample shaped as a strongly elongated cylinder, which is under the action of a transverse uniform magnetic field and the force of gravity. Theoretical results obtained within the framework of the proposed model are in qualitative agreement with the results of laboratory experiments