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The relevance of paper is due that to the fact the power grid complex of the Russian Federation has a significant impact not only on the economy of the country, but also on the comfort level of citizens. The aim of the study: to analyse the problematic issues of power grid development in the Russian Federation and to propose possible solutions using the principles of «lean production». The basis of the study was formed by the works of authors: K.K. Sevostyanova, T.S. Ilyinskaya, Y.L. Alexandrov, E.V. Skubrii, Y.D. Alexandrov and others. As a result, it was concluded that part of the problems typical for the electric grid complex of the Russian Federation can be solved by creating a Unified Electronic Platform for suppliers and territorial grid organizations.

The paper presents the results of numerical simulations of high-velocity turbulent air flows in a plane channel with a variable cross section exhibiting sudden expansion with allowance for coupled heat transfer with copper plates modeling the sensitive elements of heat flux probes. The simulations are performed for conditions of a high-enthalpy short-duration wind tunnel whose specific features are the short duration of the test regime and unsteady “falling” conditions at the model channel entrance. The wave structure of the supersonic flow, which affects the heat fluxes at the walls, is analyzed for various Mach numbers at the model channel entrance. The numerical algorithm is validated on the basis of experimental data on heating of the sensitive elements of heat flux probes for unsteady input conditions at the channel entrance. The influence of the Mach number, static parameters, and stagnation parameters on the rate of heating of the sensitive elements located at various points in the channel is studied numerically. The heat fluxes calculated under constant and “falling” conditions at the channel entrance are compared. It is shown that the accuracy of heat flux modeling can be increased by taking into account the intensity of fluctuations of the flow parameters and their changes along the channel.

Fuel rod assemblies with dense packing are promising from the point of increasing the conversion rate and heat transfer in small modular reactors. The main feature of the flow in the dense packing is the formation of quasi-periodic large-scale velocity pulsations in a gap between fuel rods, which intensify mixing between the subchannels and greatly increase heat transfer between the fuel rods and the coolant. The large-scale pulsations relate directly to the pitch-to-diameter (P/D) ratio of the rod bundle and the Reynolds number (Re). In this work, the unsteady flow structure in a gap between a flat wall and three rods with a relative pitch P/D = 1.077 is experimentally studied using the PIV method with high time resolution. The averaged flow characteristics, including the three-dimensional ones, are presented. The influence of the Re number on flow oscillations in the gap was studied. The spatial most energy-intensive flow modes were analyzed using the POD method. The results obtained indicate the presence of several traveling waves propagating along the flow. Modulation of flow oscillations in the gap was detected. These investigation results are in good agreement with the results of other authors.

Turbulent flows in a flat diffuser are characterized by the presence of two local maxima in the profiles of longitudinal velocity pulsations. The mechanism of formation of a turbulent flow structure in a flat diffuser was experimentally studied. For this purpose, the parameters of the flow kinematic structure in a diffuser with an opening angle of 2.5° were measured. The profiles of velocities and turbulent characteristics of the flow in the typical cross-sections of the channel were obtained using the optical measurement method; based on these profiles the secondary flows in the diffuser were identified. A physical model of formation of the turbulent flow structure is proposed. Within the framework of this model, a high degree of turbulent pulsations far from the wall is associated with the convection of turbulence from the near-wall region into the flow core by a secondary flow in the form of an averaged spiral motion of the medium in a flat diffuser.

The paper presents a method of molecular modeling of fluid transport coefficients, which is an alternative to the method of molecular dynamics. The transport coefficients are determined using fluctuation-dissipation theorems. The dynamics of molecules is calculated stochastically, with intermolecular forces being set using the appropriate created database. A distribution function of intermolecular forces is constructed and a formula is obtained for its analytical approximation. The method effectiveness is demonstrated by the example of calculating the viscosity and thermal conductivity coefficients of liquid argon and benzene. The obtained data are compared with the data of experimental and molecular dynamic modeling and their good agreement is established. With the same modeling accuracy, the developed method is shown to be significantly more time-efficient compared to the molecular dynamics method.

Supersonic gas-liquid jets of a coaxial atomizer at high liquid concentrations are studied experimentally. A complex of optical techniques is used for studying the droplet sizes: visualization and particle image velocimetry, laser Doppler anemometry, and Malvern Spraytec instrument. The research shows that the velocity and concentration profiles change with flow rate growth: an extended region with small droplet velocities appears behind the bow shock wave; in this case, the concentration decreases significantly slower than that at low liquid flow rates. A small increase in the jet energy at liquid flow rates greater than 100 l/h and a noticeable increase in the droplet size testify that the gas jet capabilities for breaking up the liquid in the described regimes are exhausted.

Experimental study was performed on dynamics of vapor bubble rising in the annular channel at subatmospheric pressure. The gas bubble is formed during boiling of an overheated degassed liquid in an annular channel restricted by two glass tubes with the diameters of 25 and 16 mm. It was demonstrated that the dynamics of vapor cavity while rising the vapor bubble in the annular channel demonstrates a qualitative difference from the dynamics for an ascending gas bubble. The behavior is similar to a Taylor vapor bubble behavior in a round tube with a small diameter. One of typical features of vapor cavity behavior in an annular channel is possibility of vapor cavity decay after bubble collapse during the pulsation flow mode.

Reflections of hydraulic jumps on shallow water are studied. Theoretical criteria of the transition between the regular and Mach reflections are derived, and it is shown that there is a domain of wave incidence angles where both types of reflection are possible. Numerical simulations reveal a hysteresis of this transition, which is consistent with theoretical predictions. It is shown that the hysteresis can be obtained by smoothly varying both the angle of the wedge generating the hydraulic jump and the free-stream Froude number.

This work examines the transition from kinetic to diffusion combustion using optical diagnostic methods. Experimental data were obtained on the temperature fields, composition and velocity of gas near the leading edge of a hydrogen flame flowing from a 2×20 mm slit into the air. The distribution of the rate of combustion products formation, intensity of heat release and pressure was obtained using the method of balances in equations of energy, momentum and matter transfer. It is shown that during the transition to diffusion combustion, heat release along the flame length decreases more slowly than the rate of water formation.

The problem of hydrodynamic stability of a boundary layer with diffusion combustion is formulated in the Dan-Lin-Alekseev approximation and at constant Prandtl and Schmidt numbers; it is reduced to solving a system of the tenth-order ordinary differential equations with homogeneous boundary conditions. With Lewis numbers equal to unity, it may be lowered to the eighth order. In the inviscid approximation, the stability problem is reduced to the integration of a single second-order differential equation. Based on the obtained stability equations and calculations of stationary flow parameters, the stability of a supersonic boundary layer with diffusive combustion on a permeable plate with hydrogen supply through its pores is studied for the first time by direct numerical modeling. With the Mach number M = 2, the possibility of flame flow stabilization is established using calculations. It is shown that within the framework of the inviscid theory of stability, it is possible to obtain quite reliable data on the maximum degrees of the growth of disturbances.