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The article considers the development of a near-wall separation vortex, arising at a supersonic flow around the external dihedral angle due to the pressure drop between its faces, in the range of angles of attack α = 0.5° - 6°. The processes of origin and development of separation and secondary vortices at the angle increase are investigated in detail. Particular attention is paid to the flow structure change in the vortex location zone. A clear violation of the flow self-similarity in the front part of the model in the zone of vortex system formation is shown.

The study is aimed at measuring the gas flow temperature by thermocouples whose time of reaching the equilibrium temperature is comparable with the measurement time, and heat release to structural elements of the transducer can be rather large. Results of numerical simulations of the gas flow in the temperature transducer used for measuring the stagnation temperature in high-enthalpy hotshot wind tunnels are presented. A coupled problem of the air flow around the temperature transducer is solved, and the flow field inside the stagnation chamber is calculated with allowance for heat losses to input wires and structural elements of the transducer. The data obtained are considered as results of a virtual experiment and are treated by methods of experimental aerodynamics. The retrieved results are compared with the initial numerical values of the stagnation temperature in the flow impinging onto the transducer. Sources of uncertainties arising in temperature measurements are determined, and the applicability of experimental methods for determining the stagnation temperature in short-duration wind tunnels, including those with parameters decreasing during the run, is justified. It is shown that the method of “two thermocouples” can be successfully used to determine the stagnation temperature even if the heat losses to transducer elements are comparable with heat input from the gas flow. The values of the retrieved stagnation temperature correspond to the flow temperature in the transducer within 1.2 - 3% depending on the initial temperature of the thermocouple.

The volumetric properties of liquid indium-lead alloys containing 20 and 33 at. % Pb have been measured using gamma-ray attenuation technique at temperatures from the liquidus line to 880 K. The density changes of these alloys during solid-liquid phase transition have been calculated. The obtained experimental values of the molar volume and the volume thermal expansion coefficient of melts and the results of calculations according to the laws for an ideal solution and data of other authors have been compared.

The implemented research shows that coalbed gas content in face area is proportional to pyrite content of coal, calculated with respect to iron and sulfur contents determined on X-ray fluorescent spectrometer. These results confirm the hypothesis on methane formation in coal during recovery of carbon oxides in the presence of iron-bearing minerals, in particular, pyrite, and water, and explain different contents of methane in the same rank coals. The obtained inverse proportion between the coalbed gas content in the face area and the sorption surface of coal allows supposing that methane accumulations concentrate mainly in the “solid solution” and in the closed porosity, i.e. in the coal structure. For this reason, it is more difficult and longer to recover such methane from coal than methane accumulated in open pores and fractures, which quickly leaves coal in face area.

The study focuses on the connection between two processes: deformation of proppant under the action of rock pressure and the rock pressure change after injection pressure release. The modeling of proppant deformation (mechanics of granular medium) uses the discrete element method, and the rock pressure redistribution (rock mechanics) is modeled using the earlier developed model of rock as a medium with internal energy sources and sinks, and the finite element method. The numerical modeling shows that depending on the loading history and on the rock mass properties, the mode of deformation can be both stable and unstable. For the stable mode of deformation, the pressure balance is calculated at the created fracture boundary, and the change in the proppant porosity is estimated. In the unstable mode, rock mass experiences dynamic events induced by rock pressure.

The authors investigate the physical and mechanical properties of hornstone, gabbro-dolerite and rich chalcopyrite-pyrrhotine ore subjected to flooding at the Oktyabrsky deposit in the Talnakh ore province. The analysis of the petrography, chemistry and mineralogy of the test samples showed no substantial differences in their properties after flooding. The comparison of the strength and deformation characteristics of rocks from the uniaxial compression and tension testing results demonstrate the decrease of both in water-saturated rocks and the increase in the room-temperature dried samples. The limit strength, elasticity modulus and internal friction angles have smaller values in rocks after drying than in the initial samples.

The authors implemented a series of lab-scale cyclic shear deformation tests of granular medium. The steady-state boundary conditions kept for the hundreds of thousands shear cycles result in the time-varying response of the test medium. The periods of stress fluctuations of the order of tens, hundreds and thousands cycles are observed in the medium. The time-varying response of the medium is connected with periodic formation and deformation of clusters and force chains in the medium. The DEM-based numerical modeling of cyclic shear of a granular medium with the same loading program as in the tests shows the adequacy of the discrete element method and the agreement of the numerical and experimental data.

The article describes the studies on the geomechanical behavior of the large pitwall rock mass using the seismic method. The on-site measurements of elastic wave velocities in rock mass enabled determining the elastic characteristics of rocks, which allowed an inference on the rock mass stability. It is shown that the seismic method provides sufficiently reliable data on the time history of the geomechanical behavior of the large-area pitwall rock mass, and enables the geomechanics and stability control. The long-term experience of using the seismic method to ensure pitwall rock mass stability is presented as a case-study of Zhelezny Open Pit Mine, Kovdor Mining and Processing Plant. The proposed approach is applicable at deep open pit mines.

The authors show that data on characteristics of drill mud penetration zone improve reliability of geoinformation obtained from borehole geology and geophysics. The developed procedure for the data interpretation takes into account the geomechanics and hydrodynamics of drilling. A part of the drill mud penetration zone is represented by mudcake which prevents direct measurement of porosity and permeability. The article describes the experimental studies on growth of the mudcake on the samples of low-permeable sandstone from the Jurassic reservoir rock mass using an original facility. The petrophysical nonuniformity of the mudcake was determined. The repeated measurements revealed the mudding zone.

The article describes the numerical studies on propagation of hydraulic fracture in the nonuniform-stress elastic environment around a cylindrical cavity. The modeling used the extended method of finite elements. The scope of the modeling embraced different variants of the principal stress orientation relative to the cavity and a disk-shaped initiation fracture. The influence of the stress ratio and stress level on the fracture path is described. The main types of the created fractures are shown. The conditions when the created fracture reaches the cavity surface or propagates along it are analyzed. The features of the fracture propagation and opening pressure are described for the fractures of various shapes depending on the volume of the injection fluid.