Journal of Applied Mechanics and Technical Physics最新文献

A rotationally symmetric flow of an aqueous solution of a polymer in a layer bounded from below by a solid wall rotating with a specified angular velocity around the axis perpendicular to this plane and by a flat free surface from above is considered. The influence of the relaxation viscosity on the solution behavior and the dependence of the fluid layer thickness on time in various regimes of plane rotation are studied.

This paper describes a study of strength and stability of oval composite cylindrical shells under axial compression. The geometrically nonlinear problem for the shell is solved using the finite element method. The geometric dimensions of the shell are close to those of fuselages of modern passenger aircrafts. The other phenomena described in this paper are the effect of the cross-sectional out-of-roundness of the shell, the nonlinearity of the initial stress-strain state, and the stacking of monolayers by thickness on the critical loads and weight efficiency of composite and metal shells.

Arrhenius activation energy, zero nanoparticles flux, and internal heat generation effects on natural convection about an isothermal cylinder of elliptic cross section filled with a nanofluid are numerically analyzed in this paper. The nanofluid model involves Brownian motion and thermophoresis effects. The boundary condition of the zero nanoparticle flux causes the results to be more realistic and useful. By using a suitable coordinate transformation, the nonsimilar governing equations are achieved and then solved by Keller box method. Performing the comparisons with previously published work obtains the good agreement. The dimensionless temperature profiles and the Nusselt number results for the main parameters are presented in graphical and tabular forms. The physical aspects of the problem are discussed in details.

Thermophoretic motion of a spherical evaporating droplet in a viscous binary gas medium at arbitrary relative temperature differences in its vicinity is theoretically described in a quasistationary approximation at low Reynolds and Peclet numbers. A system of gas-dynamic equations is solved, including a velocity-linearized system of Navier–Stokes equations, as well as heat and mass transfer equations. The properties of a gaseous medium are described with account for the power-law dependence of the transfer (viscosity, diffusion, and thermal conductivity) and density coefficients on temperature. The resulting numerical estimates suggest that the dependences of the thermophoretic force and the velocity of the droplet on the average temperature of its surface are nonlinear.

An experimental study is performed on the influence of surface slots (grooves) with a depth of 0.18 mm (the depth-based Reynolds number is ({{operatorname{Re} }_{h}} approx 1000)) with orientation angles (varphi = 0^circ ), 30°, 45°, and 90° on the stability of a supersonic boundary layer on a flat plate. Experiments with natural disturbances at the free-stream Mach number ({text{M}} = 2) are performed. It is found that the maximum rates of the spatial growth of disturbances decrease as the slot orientation angle decreases from (varphi = 90^circ ) to zero. At (varphi = 0^circ ) and 30°, they become smaller than the corresponding values for a smooth plate. The results obtained show that the instability of the first mode of the supersonic boundary layer, which determines the laminar-turbulent transition at ({text{M}} = 2), can be stabilized by small-depth slots with moderate angles of their orientation ((0^circ leqslant varphi < 40^circ )).

This paper presents the results of mechanical tests of specimens of the explosive under study. Stress–strain curves and Poisson’s ratio versus strain curves at a temperature of 20, 60, 80, 100°C are plotted. Temperature dependences of the mechanical characteristics of the explosive are obtained. The rigidity, strength, and deformability of the explosive are shown to decrease with increasing temperature.

A mathematical model of solution filtration has been formulated taking into account the osmotic effect in porous media containing semipermeable inclusions. The nonlinear problem of osmotic convection has been solved for the model using the Galerkin method. The properties and characteristics of convection due to osmosis have been studied.

This paper presents a theoretical study of the effect exerted on the stress-strain state in a shell mold by the contact angle between the support filler (SF) surface and the shell mold at which the spherical shell mold is not destroyed by the temperature stresses arising in it. We formulate the problem of optimization of the resistance of the spherical shell mold as a function of the contact angle of its support filler while the solidifying spherical casting within it cools down. The problem is solved using Navier equations, a heat equation, and a numerical method. The numerical scheme and the algorithm developed for solving the problem are given. It is shown that the crack resistance of the ceramic shell mold is determined by the normal stress value. The resulting resistance of the spherical ceramic shell mold is analyzed with account for the dependence of the shear modulus of the mold material on the support filler temperature.

The formation of streamwise and transverse vortices in a subsonic air jet and in an air jet with the addition of helium due to the natural instability of the flow is shown using a high-resolution direct shadow method.

Solutions to a problem of a solid circular rod made of orthotropic creep material and subjected to torsion by a constant torque are generalized to the case of an annular rod. Calculations are carried out using the Bhatnagar–Gupta method, the method based on the principle of minimum additional dissipation, and the finite element method. It is shown that the characteristic parameter method can be used to estimate a stress-strain state. The resulting analytical dependences of the twist angle rate on time at the steady-state stage of creep can be used to determine the shear parameters of the orthotropic Hill potential in torsion experiments or to refine them if these parameters were obtained via other approaches.