卷 60, 编号 6 (2019)

The energy approach to the study of a hydroelastic system consisting of an elastic blood vessel, viscous fluid flow, and an aneurysm has been developed to evaluate the various energy components of the system: viscous flow dissipation energy and the stretching and bending energies of the aneurysm wall. To calculate the total energy of the system, we have developed a computing complex including commercial and free software and self-developed modules. The performance of the complex has been tested on model geometric configurations and configurations corresponding to blood vessels with cerebral aneurysms of real patients and reconstructed by angiographic images. The calculated values of the Willmore functional characterizing the shell bending energy are consistent with theoretical data.

Taking into account the effect of viscous dissipation in the energy equation, we numerically explore the flow of an incompressible micropolar fluid with heat and mass transfer through a resistive porous medium between plane channel walls. By exploiting a similarity transformation, the governing partial differential equations are transformed into a system of nonlinear coupled ordinary differential equations, which are solved numerically for various problem parameters by means of quasi-linearization. It is found that the effect of viscous dissipation is to increase the heat and mass transfer rate at both the lower and upper walls of the channel.

A problem of the far field of internal gravity waves excited by an oscillating point source of perturbations in a stratified medium with a shear flow is solved. A model distribution of the shear flow velocity by depth is considered and an analytical solution to this problem is obtained in the form of the characteristic Green function expressed in terms of the modified Bessel functions of the imaginary index. Expressions for dispersion relations are obtained and integral representations of solutions are constructed. The dependences of the wave characteristics of the excited fields on the main parameters of the used stratification models, flows, and generation regimes are investigated.

This paper describes an overdetermined system of equations that describe three-dimensional layered unsteady flows of a. viscous incompressible fluid at a. constant pressure. Studying the compatibility of this system makes it possible to reduce it to coupled quasilinear parabolic equations for velocity components. The reduced equations allow constructing several classes of exact solutions. In particular, polynomial and spatially localized self-similar solutions of the equations of motion are obtained. The transition to the ideal fluid limit is investigated.

A numerical algorithm for solving equations of fluid dynamics for the case of a stable stratified flow with a bluff body in the form of a thin vertical barrier generating internal waves is developed and verified with the use of the OpenFOAM software. Numerical simulations of this flow are performed for different Froude numbers for steady and unsteady regimes of wave breaking; it is demonstrated that the results predicted by the proposed algorithm are qualitatively consistent with other available data. The reasons for the differences in the computed drag coefficient from the data obtained previously are discussed.

In order to investigate the double-reverse-jet film cooling (DRJFC), the multi-field coupling calculating method is used to study the effect of geometric parameters on the resultant vortex structure and conjugate thermal-elastic property. The traditional streamwise film cooling is also investigated for comparison. The results indicate that the formation of effective anti-kidney vortices is the key to enhance the dimensionless temperature of DRJFC holes. At low blowing ratios, the streamwise or lateral distance between two DRJFC holes should be increased to widen the transverse shift of the jets, thus, to increase the cooling performance. At high blowing ratios, the lateral distance should be decreased to prevent two jets from separating apart so that the malfunction of the anti-kidney vortices could be avoided. The stress concentration resulting from the nonuniform temperature distribution is considered.

Results of studying the growth of diamond structures on steel specimens with the use of intermediate layers of molybdenum or tungsten carbide cemented by cobalt are reported. The interlayers are deposited by means of detonation spraying. Subsequent deposition of diamond films onto the clad steel specimens is formed by the gas jet method and a special thermocatalytic reactor with extended activating surfaces. The nucleation process on the interlayer surfaces is intensified by preliminary seeding of the specimens in a colloid solution containing nanodiamonds. Information about the phase and structural composition of the resultant specimens and about the film surface morphology is obtained by scanning electron microscopy, Raman spectroscopy, and X-ray diffraction analysis. The tribology of the specimens is studied with the use of hardness nansensors and by the Rockwell hardness indentation method.

The kinetic equations of creep are used to compare damage accumulation in rods under tension in two forming modes: at constant stresses and at constant strain rates corresponding to strain rates in steady-state creep for the same stresses. It is found that from the point of view of increasing the residual service life at the production stage, forming to the required strain value with specified kinematics is preferable to forming at constant stresses for materials on whose strain-time diagrams for σ = const, the fracture strain decreases monotonically with increasing stress. Forming at constant stresses is preferable for materials on whose strain-time diagrams for σ = const, the fracture strain increases monotonically with increasing stress. Calculation results for several alloys are presented.

The influence of hole diameter on the fracture of quasi-brittle geomaterial in the stress concentration zone under non-uniformly distributed compression has been studied theoretically and experimentally taking into account the size effect. The failure load is determined using modified nonlocal criteria derived from the average stress criterion, the point stress criterion, and the fictitious crack criterion and containing a. complex parameter that characterizes the size of the fracture process zone and takes into account not only the material structure, but also the plastic properties of the material, the geometry of the sample, and loading conditions. The calculation results are compared with experimental data.

Finite deformation of a panel under the influence of pressure is considered. The statement of the problem in displacements with equilibrium conditions represented via true stresses in Lagrangian coordinates is proposed. It is proven that the initial equations are satisfied when the panel is uniformly curved during deformation. The use of the previously proposed defining relation makes it possible to determine a differential relationship of the laws of pressure and curvature with time at an arbitrary strain rate. Ideally plastic and superplastic deformations are considered. The dependences of pressure on the curvature and strain time are obtained at which superplasticity occurs. It is revealed that, in this case, the range of stable changes in the curvature does not depend on the strain rate, and the threshold stress does not affect the time it takes to reach a given curvature of the panel.