Home – Home – Jornals – Thermophysics and Aeromechanics 2015 number 1

The results of the numerical modeling of the flow over configurations consisting of two adjacent wedges with swept leading edges located on a flat surface of the pre-compression ramp are presented. The flow around compression wedges with different sweeps of leading edges is considered: zero sweep (χ = 0), positive sweep (χ > 0), and negative sweep (χ < 0). Swept wedges deflect the flows compressed by them either to the sides opposite to the configuration symmetry plane (χ > 0) or, on contrary, one towards another (χ < 0). The computations have been done with solution of the averaged Navier—Stokes equations and with the use of the SST κ-ω turbulence model at the freestream Mach number М = 6. The difference in flow structure is analyzed, which includes, in particular, quasi-conical three-dimensional separations of the turbulent boundary layer on the pre-compression surface, which are induced by shock waves generated by swept wedges. The characteristics of the side flow spread on compression wedges of different sweep are presented.

Results of an experimental study of the evolution of short-duration isolated wave packets in flat-plate boundary layer at Mach number M = 2 are reported. The influence of the wave packets on the laminar-turbulent transition onset is examined. Interaction of the wave packets with natural disturbances is studied. The spatio-wave structure of the wave packets is investigated in detail. The spreading angle of the wave pack-ets and their propagation velocities are evaluated.

A 3D turbulent separated flow in the neighborhood of a plate-mounted bluff body, a parallelepiped with side length ratio 1:1:2, has been numerically simulated. The 3D structure of the flow in the vicinity of the body was revealed, and the distributions of flow quantities were obtained. Numerical data for the 3D separated flow obtained with the help of several turbulence models were compared to experimental data on the profiles of mean flow velocity and turbulence kinetic energy. It is shown that restriction of the production term for turbulence kinetic energy allows a reduction in turbulence viscosity level and improves the prediction accuracy for separation zones.

A semi-empirical model of the hydrodiode is considered. The model is based on the balance equation for the liquid flow across a two-membrane hydrodiode. Results of the quantitative study are compared to experimental data.

Results of the numerical study of hydrodynamics and heat transfer in a laminar flow of viscoelastic fluid in a flat slot channel are presented in the present paper. The model of nonlinear viscoelastic fluid of Phan-Thien—Tanner is used to describe the viscoelastic properties of fluid. The solution to the stated problem by software package “COMSOL Multiphysics” is considered. The method of solution is verified, and results are compared with data of the other authors. It is determined that in the flow of viscoelastic fluid in a flat slot channel, the maximal contribution of heating due to dissipation is approximately 7–8 %.

The paper presents the results of testing a methodology for calculating two-phase flows in mini- and microchannels. The numerical methodology is based on the known fluid-in-cell method (VOF method) and the CSF procedure to account for surface tension forces. Solutions of several test problems of two-phase flow in microchannels, including the water-oil emulsion flow and gas-liquid flow in microchannels of the T-type and the stationary slug flow in a circular minichannel, were considered with the aid of this technique. Comparisons of numerical results with experimental data were carried out. A good agreement between the results was obtained.

The approximate kinetic analysis was carried out for the problem of strong condensation based on conservation equations for molecular fluxes of mass, momentum, and energy within the Knudsen layer. The closing relation was the condition for conservation of condensation flux between the Knudsen layer boundary and the mixing layer. Approximate analytical solution of the problem was obtained in the form of pressure ratio vs. temperature ratio (Mach number as a parameter). The analytical solution demonstrates a good agreement with available simulation data.

Method of measuring the lifetime of the superheated liquid was used to determine temperatures of the limit superheating of the solution of oxygen-nitrogen-helium. The method of calculating the properties of this solution (temperature of limit superheating, saturated vapor pressure, and density) based on the data on the properties of solutions of oxygen-helium and nitrogen-helium was proposed. The surface tension of the solution of oxygen-nitrogen-helium was determined in a special experiment.

Investigation results on the arc plasmatorch for water-steam heating are presented. The construction arrangement of steam plasma generator with copper electrodes of the stepped geometry was firstly implemented. The energy characteristics of plasmatorch and erosion of electrodes reflect the features of their behavior at arc glow in the plasma-forming environment of steam. The results of numerical study of the thermal state of the composite copper-steel electrodes had a significant influence on optimization of anode water-cooling aimed at improvement of its operation life.

The equations were obtained for description of heat transfer in composite bodies with reinforcement with a set of smooth tubes with pumping of incompressible liquid coolant. The appropriate boundary-value problem of heat transfer was formulated with the following qualitative analysis. The steady temperature fields in cylindrical shells with spiral-shaped tube reinforcement (with liquid coolant flow) were simulated. The influence on the temperature fields from the side of reinforcement geometry parameters, flow direction and velocity, tubes cross sections was studied. It was found that these characteristics allow significant variation of temperature field in its gradients within the composite item: this open ways for effective control of temperature fields.

The article presents the results of an experimental study of the influence of powder nanomodifiers of refractory compounds on the mechanical properties, macro– and microstructure of heat-resistant alloys ZhS–6K and Inconel 718. It is shown that the introduction of nanomodifiers into the melt leads to the refinement of the alloy structure: the average grain size decreases 1.5–2 times, and their morphology becomes similar to equiaxial at significant reduction of the particle size in the carbide phase. The service life of ZhS–6K alloy under cyclic loading at 600 ºC increases 2.7 times, and at 975 ºC by 40 %, and relative elongation increases more than twice. The mechanical properties of Inconel 718 significantly increase: long-term strength at 650 ºС increases 1.5–2 times, and the number of cycles before the collapse at 482 ºС grows more than three times. It has been found out that addition of nanomodifiers to the melt, in alloys, forms clusters of particles of refractory compounds at borders and joints of the formed grain structure that may help slowing down the processes of recrystallization (prevents the increase in the size of the contacting grains by their associations) and stabilizes the strength properties of the alloys at higher temperatures.

The prominent scientist in the field of heat and power engineering, Honorary Professor of the Ural Federal University, Honored Scientist of the RSFSR Albert P. Baskakov passed away on January 21, 2015.