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A model was developed for solids-liquid flow with any solids concentrations. The model includes the two-phase flow equations for the entire flow. It includes also the rheology law and the particle transfer equation with account for interphase slipping. The statistical model of turbulence accounts for the turbulence modulation by particles. The model was tested on a problem about a steady state flow with suspended heavy particles in a horizontal pipe. Comparison with experimental data and other accurate simulations demonstrated that this new model is useful for predicting the features of turbulent suspension flows. The secondary flows in a pipe show three-layered structure of the two-phase flow.

Two-dimensional flow around a semi-circular profile at the zero angle of attack and at Re = 50000 on the self-oscillatory period is extensively studied by the URANS method involving the standard semi-empirical SST turbulence models, the SST turbulence model with the correction for streamline curvature modified within the Rodi-Leschziner-Isaev and Smirnov-Menter approaches, as well as involving Hanjalic's four-parameter eddy viscosity elliptic relaxation model and its analog - eddy viscosity elliptic blending model proposed in the present work. This has been done with the use of different-structure grids (multiblock with structured overlapping and unstructured composite). Different numerical approximation methods realized in six codes (VP2/3, SigmaFlow, Fluent, CFX, OpenFOAM, and StarCCM+) are used. An underestimation (up to 30%) of time-averaged integral aerodynamic loads is revealed by means of the standard near-wall SST model. This is explained by the high vortex viscosity production in the profile wake. Wind tunnel tests show that the location of cutoff washers on the semi-circular profile provides a quasi-two-dimensional flow around it and allows applying measurement data to verify two-dimensional turbulent flow. The best agreement of experimental results and numerical predictions when comparing the Strouhal number and time-averaged surface pressure coefficient distributions is achieved using both the modified SST model with the correction for streamline curvature and the modified eddy viscosity elliptic blending model. When the SST model with the correction for streamline curvature, modified within the Rodi-Leschziner-Isaev, Smirnov-Menter and Durbin approaches, is used, all the above codes yield close predictions of a vertical aerodynamic load on the oscillation period.

In this paper, we present the results of a systematic numerical study of the flow and mixing modes of fluids in micromixers of various configurations, in particular, an analysis of passive micromixers, the most widely used in practice, as well as the main methods to intensify mixing. The advantages of microstructure reactors can significantly reduce reaction times and increase productivity compared to traditional bulk reactors. Four different geometries of micromixers, including the straight T-shaped microchannel, were considered. The effect of the geometrical patterns of micromixers, as well as of the Reynolds number on flow regimes and mixing efficiency were analyzed. The Reynolds number varied from 1 to 300. Unlike other studies, the efficiency of the considered mixers was for the first time compared with the cost of pressure loss during pumping. As a result, the efficiency of the most optimal micromixer in terms of hydraulic mixing and the optimal operation ranges were determined. It was shown that the maximum normalized mixing efficiency in the entire range of Re numbers was noted for mixer, in which a vortex-based intensification of mixing occurs due to the flow swirling in cylindrical chambers. This mixer allows mixing the fluids 600 times more efficiently than a straight T-mixer, while all other conditions being equal.

A model of laminar flow of a highly concentrated suspension is proposed. The model includes the equation of motion for the mixture as a whole and the transport equation for the particle concentration, taking into account a phase slip velocity. The suspension is treated as a Newtonian fluid with an effective viscosity depending on the local particle concentration. The pressure of the solid phase induced by particle-particle interactions and the hydrodynamic drag force with account of the hindering effect are described using empirical formulas. The partial-slip boundary condition for the mixture velocity on the wall models the formation of a slip layer near the wall. The model is validated against experimental data for rotational Couette flow, a plane-channel flow with neutrally buoyant particles, and a fully developed flow with heavy particles in a horizontal pipe. Based on the comparison with the experimental data, it is shown that the model predicts well the dependence of the pressure difference on the mixture velocity and satisfactorily describes the dependence of the delivered particle concentration on the flow velocity.

This paper presents a developed methodology for calculating heat and mass transfer processes in a cylindrical evaporation cell. The mathematical model reproduces all significant features of the evaporation cell geometry. In this cell, a layer of liquid is formed on a substrate with a diameter of 51 mm, heated below. To simulate heat transfer during film evaporation on a heated substrate, a numerical technique based on the Volume of Fluid method was used. The developed model was used to study the process of dry spot formation during film evaporation. The calculated data are compared with the experiment on the profile of the free surface of the film during evaporation and rupture. In general, results of this testing demonstrated good agreement with experiment. As a result, it was shown that developed numerical method makes it possible to describe process of formation dry spots.

The article considers the influence of the relief, river, and urban development on the formation of vortex structures in the atmosphere and the spread of pollutants in the city of Krasnoyarsk in winter. The weak influence of urban development on the appearance of large vortex structures over the river is shown. However, in the ground layer, it significantly changes the flow pattern and determines the character of the distribution of pollutants.

The paper presents the numerical simulation of the distribution of pollutants in winter in the atmosphere of Krasnoyarsk city. The source of the pollution is the suburban areas of the city of Krasnoyarsk, in which coal stove heating prevails. A micro-scale mathematical model based on the solution of the system of non-stationary Reynolds equations is used for modeling. The influence of various factors, such as elements of terrain and urban development, on the distribution of pollutants is studied in the paper.

A computational study of the micromixer form influence on the mixing efficiency and pressure drop in a wide range of Reynolds numbers 1 ≤ Re ≤ 300 was carried out. It was found that as the number of segments increases, the pressure drop and mixing efficiency also increase in the whole range of Reynolds numbers. The obtained results were compared with the similar in the formulation of the problem and the initial conditions one for the T-type micromixer with a direct mixing channel of the corresponding length. The dependence of the relative reduced mixing efficiency on the Reynolds numbers was obtained. It is revealed that the use of micromixers with a complex geometric shape allows the mixing processes to intensify, especially at low Reynolds numbers.

The paper presents the results of a numerical simulation of the process of cleaning the annulus of a horizontal well. The effect of the cuttings particle size on the efficiency of cuttings removal from the annulus of the well was studied. The geometry of a real well was used as the calculation model. Cutting particles with sizes from 2 to 5 mm were considered in the numerical study. Velocity profiles of the solid phase (cuttings particles) in annular channels were obtained in the course of conducted numerical simulation.

In the vicinity of a semicircular airfoil with slot suction of air provided with a 0.2-diameter (chord) vortex cell installed on the backside of the wing, at low speeds and zero angle of attack the pattern of the unsteady separated air-flow undergoes substantial changes, those changes being accompanied with the displacement of flow separation point toward the trailing edge. The slot suction of air and its blowout into the near wake in such an airfoil is organized using a discharge channel with a fan; from this channel, the air jet is discharged into atmosphere tangentially to the airfoil base, with the pressure drop in the fan being equal to twice the pressure head. Under such conditions, the integral force characteristics of the wing show dramatic changes: the lift force, initially being ultra-low negative, becomes positive, and the drag decreases two-fold. The static pressure decreases by two or three times on the upper arch of the profile, and it increases by two times on the lower part of the airfoil, the level of pressure pulsations decreasing by more than ten times.

The paper presents test results of the method for numerical simulation of liquid fuel spraying based on the Eulerian-Lagrangian model. This model describes the fluid flow inside the injector and directly behind it using the Euler-VOF method, while the dispersed medium (droplets) formed at a certain distance from the injector is described using the Lagrange approach. When using the VOF (volume of fluid method), the dynamical adjustment of the calculation grid at the phase interface is applied. Turbulence is modeled by the large eddy simulation (LES) method. The research results were compared with the data of direct numerical simulation (DNS) [1]. The calculation results based on the Eulerian-Lagrangian model show an acceptable agreement with the data of direct numerical simulation in terms of the main characteristics of the spraying. Thus, the structure of the two-phase flow, the parameters, and shape of the drops, as well as the speed and direction of their movement are determined qualitatively correctly.

Flow patterns and mixing efficiency of fluids with different inlet flow rate pulsation frequencies in T-shaped micromixer were numerically investigated at Reynolds numbers Re = 100 and Re = 180. The flow rate pulsations were set sinusoidal with different frequencies of 0; 1; 10 and 50 Hz. The relative mixing efficiency means the mixing efficiency of active mixer regarding the mixing efficiency of an identical passive mixer without pulsations at the input; it was considered as the main value. The dependences of such value on the pulsation frequencies were obtained. It was found that active micromixers are much more efficient than the passive ones. Herewith, in the engulfment regime, the mixing efficiency increases twofold regarding the passive mixer, and in the region, before the onset of the engulfment regime, the mixing efficiency increases by about 170 times. In addition, it was found that the increase in mixing efficiency is almost independent of the frequency of pulsations.

Results of unsteady two-dimensional numerical simulations for the turbulent flow over the semi-cylindrical profile at Reynolds number 45000 are presented. Three different turbulence RANS eddy viscosity models are used for the simulation. The calculations show the formation of alternating large-scale vortices shed in the wake of the body. The calculated averaged pressure distribution on the contour demonstrate a good agreement with the experimental data. A series of calculations have been performed for the estimation of influence of mesh resolution in the wake of streamlined body on the unsteady solution accuracy. It was found that a mesh size ~0.04 of chord length is sufficient to resolve the vortex street.