Vol 51, No 1 (2016)

Flow in a prismatic channel of the melts of the SKI-3 and SKMS30-ARKM-15-based rubber mixtures widely used in the chemical industry is numerically investigated. The description of these media, which exhibit viscoelstic properties when being processed, requires a particular approach that would take their rheological behavior and various anomalies into account. Amidst many rheological equations governing flows of rheologically complex media the equation that would ensure not only the good reliability of the results but also the feasibility in its practical use should be selected. The special features of viscoelastic fluids clearly manifest themselves in the flow in a prismatic channel of a noncircular cross-section. Secondary flows characteristic of the viscoelastic flows in such channels force the fluid particles to move in spiral trajectories along the channel. In the numerical calculations the Phan-Thien–Tanner (PTT) rheological model is used; its parameters are obtained on the basis of experimental data. The calculations are performed using the COSMOL Multiphysics software complex. the method of solution was tested against the analytical solution of the PTT fluid flow in a round tube which was compared with the numerical solution.

The influence of an electric field on spreading of a thin conducting liquid layer over a plane rigid substrate is investigated theoretically. The conductivity of the liquid is assumed to be so low that the effect of the magnetic field of the currents generated in the liquid under the action of the electric field can be neglected. The spreading is assumed to be so slow that the quasi-steady approximation can be used to calculate the electric field strength which can be considered to be equal to zero inside the liquid. Equations that describe variations in the layer shape are obtained in the lubrication theory approximation. The general formulation of the problem is considered. The solution of the problem is obtained in parametric form when the effect of the gravity force and the surface tension can be neglected. Variations in the layer thickness along the substrate are so smooth that the charge distribution over its surface can be assumed to be the same as that over the substrate surface in the absence of the liquid.

The study continues the cycle of investigations concerned with the modeling of the methods of controlling flow regimes in compressible boundary layers. The effect of distributed heat and mass transfer on the stability parameters of a supersonic boundary layer is considered at amoderate supersonic Mach number M = 2. Emphasis is placed on the modeling of both the normal injection, when only the V component of the mean velocity is nonzero, and injection in other directions, including the tangential injection, when only the U component is nonzero on the wall. The formulation of the problem is similar with that of the gas curtain influence on the small fluctuation development. It is assumed that the effect of the injection of a similar gas with different temperatures is analogous to the injection of a gas with different densities, namely, the cold gas injection mimics the heavy gas injection, and vice versa. For this reason, in this study this modeling is realized by means of varying the temperature factor (wall heating or cooling). The case, in which the so-called “cutoff” regime is realized, that is, the velocity disturbances on a porous surface can be taken to be zero, is also considered.

Flow structure and heat and mass transfer in a swirling two-phase stream is numerically modeled using the Reynolds stress transport model. The gas phase is described by the 3DRANS system of equations with account for the inverse influence of particles on the transport processes in the gas. The gas phase turbulence is calculated using the Reynolds stress transport model with account for the presence of disperse particles. The two-phase nonswirling flow behind an abrupt tube expansion contains a secondary corner vortex which is absent from the swirling flow. The disperse phase is redistributed over the tube cross-section. Large particles are concentrated in the wall region of the channel under the action of the centrifugal forces, while the smaller particles are in the central zone of the chamber.

The problem of detonation initiation in a supersonic flow of a stoichiometric propane-air mixture in a plane elbowed channel of constant width is considered. In the bend zone the channel walls are made in the shape of circles of given radii, whose lengths are determined by the given angle of the channel turn. An investigation is performed within the framework of the single-stage combustion kinetics using a numerical method based on the Godunov scheme and included in an original program complex, or a “virtual experimental setup”, developed for performing multiparameter calculations and flow visualization. The critical conditions of detonation generation are determined as functions of the oncoming flow velocity, the channel turn angle and width, and the radii of curvature of the walls.

The free surface of a liquid film exposed to a laser beam is deformed and suffers a rupture. Depending on the thermal load intensity and the thermal properties of the liquid the rupture can be accompanied by the formation of secondary droplets over the film crown. This process is investigated using a mathematical model describing the motion of the thin layer of a viscous nonisothermal liquid. The model is based on the two-dimensional Navier–Stokes equations. The boundary conditions at the film-gas and film-liquid interfaces necessary for the solution of these equations are derived in the explicit form. The results of the solution of model problems are presented.

The results of the optimal contouring of asymmetric plane nozzles under some additional constraints are presented. One of the constraints is due to the asymmetric arrangement of the unknown nozzles relative to the combustion chamber exit. The investigation is based on the numerical integration of the Reynolds-averaged Navier–Stokes equations and direct optimization methods using genetic algorithms and the representation of the optimized contours in the form of the Bernstein–Bézier curves.