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Adaptation of a mathematical model of gas diffusion combustion for different flow rates of CO–H2 and a constant coal flow rate is carried out. It is shown that the results of calculating the main characteristics of the flame are in satisfactory agreement with experimental data and can be used to determine the structure of pulverized coal–gas flow, gas composition, particle and gas temperature, carbon combustion efficiency, etc. The proposed model is suitable for analyzing the stability of coal–gas flame and the transient processes accompanying changes in the mode of supply of the fuel-oxidizer medium.

This paper presents a study of the influence of various factors on heat transfer in microchannels associated with the use of the velocity slip (including thermal creep) and temperature jump boundary conditions on the walls. These factors can affect heat transfer both individually and together, but their effect on heat transfer in the microchannel has still not been practically studied. An attempt to eliminate this lack was made in this paper. It was shown that as the slip length increases the value of the heat flux density increases by about 40% and the average heat transfer coefficient increases by about 50% compare to no-slip conditions. Wherein, the pressure drop significantly decreased, that is, two positive effects took place simultaneously. The presence of thermal creep also reduced the pressure drop in the channel and increased the average heat transfer coefficient, but this effect was significantly less than the effect of the slip length. On the other hand, the taking into account of a temperature jump on the wall led to a certain increase in the pressure drop, but the heat transfer coefficient increased.

The viscosity coefficient and thermal conductivity of suspensions with single-wall carbon nanotubes have been experimentally studied. The nanotube mass concentrations are varied from 0.05 to 0.25 wt %. The suspensions exhibit non-Newtonian behavior. The dependences of the rheological suspension parameters on the nanotube concentration are obtained. It is established that the properties of the carrier liquid affect the viscosity coefficient and thermal conductivity of the suspensions.

The authors have performed numerical simulation of pressure pulsations in the draft tube of a hydraulic turbine that are excited by large-scale vortex structures. Numerical simulation of unsteady transfer in the draft tube in different operating regimes of the turbine has been carried out. It has been shown that the structure of flow in the outlet diffuser corresponds to vortex-core flow. Calculated data have been compared with experimental results and their agreement has been shown. To suppress pressure pulsations, a study has been made of the influence of various structural inserts into the draft tube, such as fins, a cross piece, and a hollow cylinder in the draft-tube cone. Consideration has been given to the influence of various constructions on the structure of flow behind the wheel and on pressure pulsations on the draft-tube wall. A comparison has been made of the constructions and optimum parameters have been selected to stabilize the flow in the diffuser of the hydraulic-turbine draft tube.

Experimental investigation of the deposition of nanoparticles in a circular channel in a constant magnetic field has been carried out. The dynamics of growth of nanoparticles deposits on the channel walls depending on the Reynolds number and magnetic field strength has been studied in the experiments. The influence of magnetic field on pressure drop at different Reynolds numbers has been investigated. Characteristic profiles of the zones of nanoparticles depositions have been obtained for the first time; the sizes of the deposition areas and the rates of their formation depending on the Reynolds numbers, magnetic field strength and time have been determined.

The experiment investigation of laminar forced convection of nanofluids with Al2O3, TiO2, ZrO2 and diamond nanoparticles was carried out. Nanoparticle concentration varied in the range from 0.25 to 6 vol% in the experiments. The nanoparticle size ranged from 5 to 150 nm. The dependence of heat transfer coefficient and pressure drop from the concentration, size, material of the nanoparticles was studied. It was shown that adding nanoparticles to the coolant significantly influences the heat transfer coefficient in the laminar flow regime. It is shown that with increasing nanoparticles concentration, the local and average heat transfer coefficients at a fixed Reynolds number increase. The effect of nanoparticles material on the heat transfer coefficient has been also demonstrated. It was shown the effect of properties of the base fluid on the heat transfer coefficient nanofluids was considered. The effect of rheology nanofluids on the heat transfer coefficient was analyzed.

Paper reports on optical diagnostics and numerical simulation of the flow structure and transport of a passive scalar in a turbulent swirling jet with vortex core breakdown. Based on the measurements of the instantaneous velocity and concentration fields by PIV and PLIF techniques, the Reynolds stresses and Reynolds fluxes are evaluated and compared to those obtained from URANS and LES simulations. Based on the experimental data and LES-simulation results, the local convective and turbulent transport of the passive scalar are analyzed.

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.

The flow and mixing modes of non-Newtonian fluids in a T-shaped micromixer were studied by numerical simulation in the range of Reynolds numbers 1–250. The non-Newtonian fluid was described using the power-law model. The exponent n was varied: 0.3, 0.5, and 0.8. The mixing efficiency and pressure drop in the channel were correlated with the exponent n and Reynolds number. The exponent n was shown to significantly affect the flow structure before and especially after the transition from symmetric to asymmetric flow modes.

In the present paper, the regimes of flow and mixing of water and a nanofluid with aluminum oxide nanoparticles in a T-shaped microchannel have been studied numerically. The Reynolds number was varied from 10 to 400, and the volume concentration of nanoparticles was varied from 0 to 10%. Nanofluids with mean sizes of particles from 50 to 150 nm were considered. The viscosity coefficient of the nanofluid was taken from experimental data. In all cases, it exceeded the viscosity coefficient of water and depended on not only the concentration of nanoparticles, but also on their sizes, and the viscosity of the nanofluid with smaller particles was higher than the viscosity of the nanofluid with large particles. It has been established that there exist regimes of steady irrotational flow, steady vortex flow with two horseshoe vortices, and steady flow with two vortices in the mixing channel. It has been shown that when the flow goes from the regime with horseshoe vortices to the flow conditions with two single vortices, the mixing efficiency increases several times. It has been established that the flow conditions and the mixing efficiency largely depend on the volume concentration of particles and their sizes.

In the present study, we report on the results of an experimental study of pressure pulsations in the flow duct of a medium-scale hydrodynamic bench with Francis turbine. In various regimes, integral and pulsation characteristics of the turbine were measured. With the help of high-speed filming, the structure of the flow behind the turbine runner was analyzed, and the influence of this structure on the intensity and frequency of pressure pulsations in the flow duct was demonstrated.

We report on the examination of several approaches to simulate computationally the unstable regime of a model Kaplan turbine operating at off-design load. Numerical simulations complemented by laboratory experiments have been performed for a 60:1 scaled-down laboratory turbine model using two Reynolds-averaged Navier–Stokes (RANS) models (linear eddy viscosity model (LEVM), and a Reynolds stress model (RSM), including realizable , k-ω SST, and LRR), detached eddy simulation model (DES), and large eddy simulation model (LES). Unlike the LEVM, the RSM, DES, and LES reproduced the mean velocity components and the intensities of their fluctuations and pressure pulsations well. The underperformance of the LEVM is attributed to the high eddy viscosity as a consequence of an excessive production of the turbulent kinetic energy due to the models’ inability to account for the turbulent stress anisotropy and the stress-stain phase lag, both naturally accounted for by the RSM. This led to a much larger model...

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 systematic measurements of the thermal conductivity coefficient of nanofluids at room temperature. In total, more than fifty various nanofluids based on water, ethylene glycol, and engine oil containing particles of SiO2, Al2O3, TiO2, ZrO2, CuO, and diamond were studied. The nanoparticles volume concentration ranged from 0.25 to 8% and the particles size ranged from 10 to 150 nm. It is shown that the thermal conductivity of nanofluids is not described by the classical theories (Maxwell’s and so forth). The nanofluid thermal conductivity coefficient is a complicated function not only of the particle concentration, but also the particles size, their material, and type of base fluid. Measured thermal conductivity coefficients almost always exceed the values calculated by the Maxwell’s formula, though nanofluids with sufficiently small particles may have thermal conductivity coefficients even lower than those predicted by the Maxwell theory. However, in all cases, the nanofluid thermal conductivity coefficient enhances with increasing particle size. It is convincingly shown that there is no direct correlation between the thermal conductivity of the nanoparticle material and the thermal conductivity of nanofluid containing these particles. The base liquid also significantly influences the effective thermal conductivity of the nanofluid. It has been confirmed that the lower the thermal conductivity of the base fluid, the higher the relative thermal conductivity coefficient of the nanofluid.

The experiment investigation of turbulent forced convection of nanofluids with SiO 2 and Al 2 O 3 nanoparticles was carried out. Nanoparticle concentration varied in the range from 0.5 to 2 vol.% in the experiments. The nanoparticle size ranged from 10 to 100 nm. The dependence of heat transfer coefficient and pressure drop from the concentration, size, material of the nanoparticles and temperature was studied. It was shown that adding nanoparticles to the coolant significantly influences the heat transfer coefficient in the turbulent flow regime. It is shown that with increasing nanoparticles concentration, the local and average heat transfer coefficients at a fixed Reynolds number increase. Decrease in heat transfer coefficient with increasing particles concentration may take place at a fixed flow rate. It is shown that, the heat transfer coefficient of the nanofluid in turbulent regime increases with increasing nanoparticles size at a fixed flow rate, while has a certain maximum at a fixed Reynolds number. The effect of nanoparticles material on the heat transfer coefficient and pressure loss has been also demonstrated. It is found that the inlet temperature is another factor having a significant effect on turbulent heat transfer performance of nanofluids.

The paper presents experimental data on the laminar-turbulent transition in the nanofluid flow in the pipe. The transition in the flows of such fluids is shown to have lower Reynolds numbers than in the base fluid. The degree of the flow destabilization increases with an increase in concentration of nanoparticles and a decrease in their size. On the other hand, in the turbulent flow regime, the presence of particles in the flow leads to the suppression of smallscale turbulent fluctuations. The correlation of the measured viscosity coefficient of considered nanofluids is presented.

Flow patterns and mixing of liquids with different viscosities in T-type micromixers are numerically investigated on the Reynolds number range from 1 to 250. The viscosity ratio of the mixing media varied from 1 to 2; its effect on the flow structure and the mixing is studied. The dependences of the mixing efficiency and the pressure difference in the channel on the viscosity ratio and the Reynolds number are obtained. It is shown that the viscosity ratio has a considerable effect on the flow structure before and after transition from the symmetric to the asymmetric flow pattern. The self-similar behavior of the asymmetric flow pattern is established.

Turbulent flow of nanofluids based on the distilled water with aluminum and silicon oxide particles of different sizes in a cylindrical channel is studied. The results of the measurements of the heat transfer coefficient and the pressure difference are presented. The maximum volume concentration of the particles was not greater than two percents. The dependence of the heat transfer coefficient on the nanoparticle concentration and their sizes and material is studied. It is shown that a considerable increase in the nanofluid heat transfer coefficient, compared with the corresponding value for water, may generally be expected. At the same time, the heat transfer coefficient of a nanofluid depends on the nanoparticle size and material; because of this, under certain conditions the nanofluid heat transfer coefficient can turn out to be lower than that of the baseline fluid. Situations, when this can occur, are established. It is for the first time experimentally shown that the nanofluid viscosity coefficient depends not only on the nanoparticle size but also on its material.

Some results of experimental studies of the vortex-core reconnection phenomenon in the flowthrough duct of a combined-flow turbine were presented. The studies were performed on a medium-scale hydrodynamic test bench, the design of which was maximally similar to real hydroturbines. Using high-speed recording in a regime with a 75% load in a suction-pipe diffuser, the reconnection of a precessing vortex-core with detachment of vortex rings was observed. Aperiodic pressure surges due to the reconnection of a vortex and the formation of vortex rings were experimentally detected.

A superhydrophobic phenomenon during fluids flow through microchannel due to the presence of the textures on the walls of the channels was considered. A numerical study of fluids flow and mixing in the microchannel at different Reynolds numbers and average roughness sizes has been carried out. The shift in the critical Reynolds number of the transition from the vortex symmetric flow regime to the vortex asymmetric (engulfment) regime towards lower values in the T-shaped microchannels with textured walls was found. The substantially unsteady structures in the straight microchannels with textured walls at Reynolds numbers of about 1000 were obtained.

A spatial mathematical model of the evaporation system using film flows has been developed. A numerical study of several modes of film flow in an evaporation cell at a heater temperature below the boiling point has been carried out. The characteristics of the film flow and the features of the coupled heat and mass transfer processes in the gas-film-metal substrate system have been studied. Good agreement between the calculation and the experiment on the main parameters of the wave motion of the film and the heat transfer characteristics has been obtained.

The work is devoted to experimental and computational studies of the behavior of water drop in a flow behind incident shock wave and verification of calculations on this basis. High-Speed visualization of the water drop interaction with the flow behind incident shock wave was obtained in the experiments at shock wave Mach numbers Ms=1.109–1.34 and Weber numbers We = 208–2260. Conditions consistent with the experiments are simulated in the calculations. The numerical approach is based on the use of the volume of fluid (VOF) method to resolve the phase interface, large eddy simulation (LES) model to describe turbulence, and adapted dynamic grid technology. The structure of the flow near and in the wake of a drop, the features of the flow around a drop, the type of the shape evolution, and the character of the mass entrainment were studied. Comparison of simulation results with experimental data indicates good agreement with the main integral characteristics of the process, i.e. morphology, dynamics, and induction time of droplet breakup.

Intensification of heat transfer processes is an important and relevant task, and one way to solve it is the use of liquids with various nanoparticles, called “nanofluids.” Therefore, an experimental study of the convective heat transfer of nanodiamonds suspensions in a circular straight pipe was carried out in this paper. Ethylene glycol was used as the base liquid. The concentration of nanoparticles ranged from 0.25 vol.% to 2 vol.%. The Reynolds numbers varied from 5 to 100. The values of the viscosity and the thermal conductivity coefficients of the resulting nanofluids were also measured experimentally. It was found as a result of these measurements, that the dependence of the thermal conductivity on the concentration of nanoparticles is described by the Maxwell equation. The dependence of the nanofluids viscosity coefficient on the nanoparticles concentration was significantly differ from the Einstein equation, it was much higher. It was found as a result of experimental studies of convective heat transfer, that as the concentration of nanoparticles increases, the heat transfer coefficient also increases, and for a maximum concentration, it was 15% higher then for the base fluid.

The experiment-calculated investigation of forced convection of nanofluids based on CuO nanoparticles was carried out. Nanoparticle concentration varied in the range from 0.25 to 2 vol.% in the experiments. The considerable heat transfer intensification was obtained. The power applied to the pump for pumping the nanofluid was measured. A strong influence of the polymer used to stabilize the transport properties of nanofluids was shown. The Newtonian behavior for 0.25%-nanofluid, and non-Newtonian behavior, that described well with power-law model, for all other cases, were obtained. The hydrodynamic description and the model of homogeneous nanofluids are used for modelling. As is shown by the results, such a model satisfactorily describes in some cases the data of full-scale experiment of nanofluids forced convection in laminar flow regimes.

The paper presents results of numerical simulation of unsteady three-dimensional flow in the two high-head hydraulic turbines. The numerical technique for calculating of low-frequency pressure pulsations in a hydraulic turbine is based on the DES turbulence model and the approach of rotated reference frame. The paper also presents the analysis of the flow structure behind the runner of the turbines, as well as shows the effect of the flow structure on the frequency and intensity of non-stationary processes in the turbines. Besides, the behavior of the pulsations in the hydraulic turbines was defined. Comparison of the calculation results with the experimental data has shown close agreement between theory and experiment.

Numerical technique for calculating pressure pulsations in the high-head hydro turbines is presented in the paper. The numerical technique is based on the use of DES turbulence model and the approach of “frozen rotor”. This technique is applied for simulating unsteady turbulent flow in a flow path of a high head hydropower plant. The flow structure downstream the runner and its influence on the intensity of non-stationary processes is analyzed. It is shown that the low-frequency pressure pulsations in water turbines are mainly caused by the precessing vortex rope downstream the runner. The vortex dynamics basically determines the pulsational characteristics of turbine operation. It is found that the averaged velocity components of flow downstream the runner can serve as indicators, which characterize the intensity of transient phenomena in the draft tube of water turbine. The comparison of simulation results with the experimental data shows reasonable agreement in the integral characteristics (efficiency, flow rate, power) as well as pulsational characteristics (intensity and frequency) of the flow and turbine operation.

The heat transfer coefficient of a nanofluid in a cylindrical channel under constant heat flux density at the walls is measured experimentally. The studied fluid was prepared based on distilled water and CuO nanoparticles with an average size of 55 nm. To stabilize the nanofluid, a biopolymer was used. The volume concentration of nanoparticles was in the range from 0.25 to 2%. It is shown that the nanofluid is Newtonian at the lowest concentration of nanoparticles, and in all other cases, its rheology is described well by the model of a power-law fluid. A correlation of the dependence of the parameters of this model on the concentration of nanoparticles is obtained. It is found that the presence of nanoparticles greatly intensifies the heat transfer.

The viscosities of all nanofluids considered are shown to be dependent on the size of nanoparticles. It has been established that the greater the nanofluid viscosity, the smaller the size of particles. The measurements carried out in this study make it possible for the first time to fix experimentally the fact of the dependence of the viscosity of nanofluids on the particle material.

The features of the nanofluid flows modeling are analyzed. In the first part the thermophysical properties (viscosity and thermal conductivity) of nanofluids are discussed in detailed. It was shown that the transport coefficients of nanofluids depend not only on the volume concentration of the particles but also on their size and material. The viscosity increases with decreasing the particle size while the thermal conductivity increases with increasing the particle size. The heat transfer of nanofluid in cylindrical channel and laminar-turbulent transition in some flows are considered. The heat transfer coefficient is determined by the flow mode (laminar or turbulent) of the nanofluid. However it was shown that adding nanoparticles to the coolant significantly influences the heat transfer coefficient. The laminar-turbulent transition begins in all cases earlier (at smaller Reynolds numbers) than for base fluid. In conclusion the possibility of the use of traditional similarity criteria are discussed.

The viscosity and thermal conductivity of the fluid are determined by the transport of the impulse and energy in the system considered. In turn, these transports are defined by and depend on the interaction of the fluid molecules. The situation in the fluid under confined conditions (e.g., in a nanochannel) is more complicated, because the transport of the impulse and energy in fluids is highly dependent on the interaction of the fluid molecules with the wall atoms (or molecules). Therefore, the viscosity and thermal conductivity of such a fluid are the properties of the entire “fluid+wall” system. In this chapter, the statistical theory of transport processes in fluids under confined conditions is proposed. The considered system is the specific two-fluid system consisting of fluid and wall molecules. In the chapter, the new constitutive relations for the fluid under confined conditions are proposed. As a result, the Green-Kubo formulas were generalized. Using this new formula and the molecular dynamics method, the viscosity coefficient of the fluid in a nanochannel was studied. It is shown that the viscosity coefficient depends, to a large extent, on the properties of interaction of fluid molecules with channel wall atoms.

The rheological properties of several tens of nanofluids based on water, ethylene glycol, and engine oil with nanoparticles of various oxides and diamond is studied experimentally. Particle concentrations and their sizes were varied within quite wide range. Tested nanofluids did not contain any dispersants, while the base fluid was Newtonian liquid. It is revealed that in some cases, nanofluids are characterized by non-Newtonian rheological behavior. In the last part of the paper the effect of the nanoparticles on the properties of drilling fluids is discussed.

In this work, the authors present results of adaptation and testing of the hot-wire method for determination for the thermal-conductivity coefficient of nanofluids. A mathematical model of heat transfer with allowance for free convection has been constructed to elucidate the parameters of an experimental setup and the range of its applicability. The experimental procedure has been tested on measurements of the thermal conductivities of water and ethylene glycol. The thermal-conductivity coefficient of a nanofluid has been measured at room temperature. The nanofluid under study was prepared on the basis of ethylene glycol and alumina nanoparticles. The concentrations of the nanoparticles ranged from 0.5% to 2% by volume. Good agreement has been obtained between the measured values of the thermal-conductivity coefficient and the data of other authors.

This paper discusses the current state of knowledge of the thermophysical properties of nanofluids. The viscosity, thermal conductivity and heat transfer of nanofluids are considered. Experimental and molecular dynamics data are presented. It is shown that viscosity and thermal conductivity of nanofluids generally cannot be described by classical theories. The transport coefficients of nanofluids depend not only on the volume concentration of the particles but also on their size and material. The viscosity increases with decreasing the particle size while the thermal conductivity increases with increasing the particle size. The reasons for this behavior are discussed. The heat transfer coefficient is determined by the nanofluid flow mode (laminar or turbulent). The use of the nanofluids as a coolant significantly affects the magnitude of the heat transfer coefficient. In laminar flow the heat transfer coefficient of nanofluids in all cases is much more than that of base fluids. It is shown that a 2%-nanofluid intensifies the heat exchange more than twice compared to water. The effect of using nanofluids in turbulent mode depends not only on the thermal conductivity of the nanofluid, but also on its viscosity.

The article presents the initial stage of developing a hybrid mathematical model for describing the recovery of oil from a natural sand reservoir. The hybrid model means that part of the computational domain (microchannel structure in the space between particles) is calculated by one- dimensional models is based on the hydraulic circuit theory, and another part (large cracks and caverns) is calculated by computational fluid dynamics methods (CFD). The article also describes a unique algorithm for building a network model based on preliminary CFD calculation. The last section of the article presentation compares of results of calculation CFD and network models.

Numerical modeling of the unsteady flow in the draft tube of the test bench hydro turbine is conducted. The hybrid RANS-LES methods for modeling turbulent flows are compared. The intensity and frequency of pressure fluctuations, which are induced by the vortex core precession under the runner, and the integral characteristics are considered. An analysis of the synchronous and asynchronous parts of pressure fluctuations is done; the generating and influence of the synchronous component of fluctuations are considered. The vortex core interaction with the draft tube elbow is considered.

A new Eulerian algorithm is proposed for computing incompressible flows with moving boundaries of arbitrary geometry. The algorithm can be regarded as an extension of Hirt’s classical volume-of-fluid method. The results of its implementation and testing are presented. A comparison of the numerical results with experimental data and computations of other authors reveals good agreement.

Laminar convective heat transfer of water–alumina nanofluid in a circular tube with uniform heat flux is investigated numerically on the basis of two-component model, which takes into account nanoparticle transport by diffusion and thermophoresis. A new expression for thermophoretic mobility is suggested on the basis of existing experimental results and theoretical concepts. It is shown that thermophoresis leads to a significant reduction of nanoparticle volume fraction in the boundary layer near the wall. The corresponding viscosity reduction causes the velocity increase near the wall and flattening of velocity profile near the tube axis to keep the mass flow rate constant. The decrease of wall shear stress leads to the decrease of the required pressure drop. The calculations for two-component model provide higher values of the local and average heat transfer coefficients in comparison with the one-component model. The difference does not exceed 10% and decreases with increasing the thermal Peclet number. The calculations for one-component model show the independence of local and average Nusselt numbers on the nanoparticle volume fraction. The results for two-component model predict the increase of Nusselt number when the thermophoretic effect becomes stronger. The effectiveness of water–alumina nanofluid is analyzed by plotting the average heat transfer coefficient against the required pumping power. It is shown that the nanofluid shows better performance than the base fluid in the range of low pumping power and, correspondingly, low inlet velocity.

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.

The paper deals with the numerical simulation of the flow in the Francis-99 hydraulic turbine at three different problem formulations, namely, the application of the method of rotating coordinate system, sliding mesh model, and consideration of a compressible fluid. The pulsations intensity and pressure pulsation spectra obtained by numerical simulation and experimentally are compared. It is shown that the simulation of a problem considering compressible fluid, and that conducted by the sliding mesh method gives significantly greater pressure amplitudes. It is also shown that the precessing vortex core is a source of pressure waves in the entire turbine flow path.

The paper presents a verification of calculation modeling methods of atomizing of a gas and gas-liquid stream from a pneumatic nozzle based on the experimental data obtained in the IT SB RAS. Turbulent supersonic flow of compressible gas is considered here. Mathematical model includes description of gas phase motion based on the RANS (Reynolds Averaged Navier-Stokes) and URANS (Unsteady RANS) approach using two-parameter turbulence model k-ω SST and Reynolds Stress Model (RSM). The Lagrange method was used to model flow of water droplets. Dispersed phase is solved by tracking a large number of droplets through calculated flow field. Dispersed phase can exchange momentum, mass, and energy with fluid phase. Comparative analysis showed an acceptable qualitative and quantitative agreement between calculation and experiment, both for subsonic and supersonic flow.

An experiment-calculated investigation of forced convection of nanofluids based on Al2O3nanoparticles was carried out. The hydrodynamic description and a model of homogeneous nanofluids were used. The homogeneous nanofluids model assumes that the hydrodynamics and heat transfer can be described by conventional Navier-Stokes and heat transfer equations with the physical parameters corresponding to nanofluids. The results showed that this model very well described the experimental data in some cases. However, in some other cases, there are discrepancies between experiment and theory that can be explained by the real heterogeneity of nanofluids and the errors in the experimental determination of thermal conductivity and viscosity of nanofluids.

Results of the experimental and numerical simulation for swirl flow in combustion of a lean methane-air mixture in a model combustor at atmospheric pressure are represented. The panoramic method for the flow velocity measurement and the calculation by a large eddy method were used for the investigation of the nonstationary turbulent flow. The numerical modeling for the breakdown of the vortex core of the flow and the topology of large-scale vortex structures forming in it showed the close fit to the experiment. The analysis of obtained data showed that for the case of the intensive swirl of the flow as well as in the case of the flow without combustion, dynamics of the flow with combustion was determined by the global azimuthal instability mode corresponding to the intensive precession of the vortex core. The flame had the similar characteristics of the stability and compactness in the case of stabilization by the low swirl; however, velocity pulsations in the flow corresponded to the development of only local instability modes. Thus, the other kind of vortex breakdown in the case of the low swirl, for which the central recirculation zone is lacking, is not only favorable in view of the reduction of the NOx emission, but also remains a possibility for the effective use of the active control method for the flow and combustion. In particular, the given result may be used for the elimination of the thermoacoustic resonance in combustors.

Flow regimes and mixing pattern in a T-type micromixer at high Reynolds numbers were studied by numerical solution of the Navier-Stokes equations and by micro-PIV and micro-LIF experimental measurement. The Reynolds number was varied from one to one thousand. The cross section of the mixing channel was 200 μm×400 μm and its length was 3000 μm. Five different flow regimes were identified: (i) stationary vortex-free flow (Re 400). Maximum mixing efficiency was obtained for stationary asymmetric vortex flow. In this case, an S-shaped vortex structure formed in the flow field. Also the numerical investigation of flow and mixing in the T-shaped micromixer with asymmetrical inlet conditions for different Reynolds numbers was carried out. The good agreement between calculation and experiment was obtained as a result.

Flow regimes and mixing performance in a T-type micromixer at high Reynolds numbers were studied by numerical solution of the Navier–Stokes equations. The Reynolds number was varied from 1 to 1000. The cross section of the mixing channel was 100 μm × 200 μm, and its length was 1400 μm. The transverse inlet channels were symmetric about the mixing channel, and their cross-section was 100 μm × 100 μm, and the total length was 800 μm. Five different flow regimes were identified: (i) stationary vortex-free flow (Re 400). Maximum mixing efficiency is obtained for nonstationary asymmetric vortex flow. In this case, an S-shaped vortex structure is formed in the flow field. The effect of the slip conditions on the flow pattern and mixing efficiency is studied. The slip length varied from 1 to 70 μm in the calculations. It was shown that the mixing can be controlled by hydrophobic coating.

The paper presents an experimental study of oscillatory response in the Francis turbine of hydraulic unit. The experiment was performed on large-scale hydrodynamic test-bench with impeller diameter of 0.3 m. The effect of air injection on the intensity of pressure pulsations was studied at the maximum pressure pulsations in the hydraulic unit. It was revealed that air delivery into the water-conveyance system of the turbine results in almost two-fold reduction of pressure pulsations.

The paper presents an experimental study of the relationship between the vibration of the water turbine unit and the pressure pulsations in the flow path. It is shown that the air injection into the flow path leads to a decrease in the hydraulic turbine vibration associated with the formation of the precessing vortex core.

The paper presents an experimental study of oscillatory response in the Francis turbine of hydraulic unit. The experiment was performed on large-scale hydrodynamic test-bench with impeller diameter of 0.3 m. The effect of air injection on the intensity of pressure pulsations was studied at the different regimes in the hydraulic unit. It was revealed that air delivery into the flow path system of the turbine results in almost two-fold reduction of pressure pulsations, but for optimal regimes, there is an increase in pressure pulsations.

Experimental study of the magnetic nanofluids forced convection in a constant magnetic field was carried out. Dependence study of the magnetic nanofluid heat transfer coefficient on the effect of a constant magnetic field was made. The effect of a constant magnetic field on the pressure drop during the magnetic nanofluid flow was shown.

In the present work, the regimes of the flow and mixing of fluids in a T-shaped micromixer in the range of the Reynolds numbers from 1 to 1000 are investigated systematically with the aid of numerical modeling. The flow and mixing regimes are shown to alter substantially with increasing Reynolds numbers. Five different flow regimes have been identified in the total. The dependencies of the friction coefficient and mixing efficiency on the Reynolds number are obtained. A sharp increase in the mixing efficiency at a flow transition from the symmetric to asymmetric steady regime is shown. On the other hand, the mixing efficiency slightly drops in the laminar-turbulent transition region. A substantial influence of the slip presence on walls on flow structure in the channel and mixing efficiency has been revealed.

We propose a numerical algorithm for simulating steady laminar flows of an incompressible fluid in annular channels with eccentricity and rotation of the inner cylinder. This algorithm enables us to describe this class of flows for wide ranges of the annular channel and flow parameters. We present the implementation details and the results of testing this numerical method. For a series of flows in an annular clearance, we compare the numerical results to available analytic solutions and experimental data. In all cases under consideration the simulated data agree well with the available experimental, analytical, and numerical solutions.