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Results of optical and gas-dynamic investigations of the microwave discharge plasma under conditions of gas-jet synthesis of diamond are reported. The data are analyzed for determining the temperature and composition of the mixture in the discharge chamber for the purpose of further optimization of the method. The influence of the flow rate of the injected gas mixture on the macroparameters of the gas mixture flow at the exit of the discharge chamber is studied. The temperature and pressure measured in the discharge chamber are used for the numerical analysis of the mixture composition depending on the injected gas flow rate. It is demonstrated that the mixture composition at the exit of the discharge chamber correlates with the rate of diamond synthesis.

Numerical analyses of turbulent boundary layer parameters and skin-friction drag reduction on a flat plate under the effect of air micro-blowing with the use of the SST k-w turbulence model are performed. The macroscale characteristics of a huge number of microjets are simulated by using a microporous wall model (MPWM) incorporated into ANSYS FLUENT by user-defined functions. Numerical results obtained within the Mach number range M=0.2-0.5 (Reynolds number Re=2.88x106-7.20x106) confirm the experimental data of other researchers. Furthermore, a slight increase in the boundary layer thickness, displacement thickness, and momentum thickness, as well as a decrease in the velocity gradient and shear friction are well captured. In comparison to a simple flat plate, applying air micro-blowing reduces the skin-friction coefficient by 51% at the Mach number M=0.4 and blowing fraction of 0.008. Additionally, the skin-friction coefficient decreases as the blowing fraction and Mach number increase.

This paper describes a problem of measuring a gas flow temperature using thermocouples for which the time it takes to reach an equilibrium temperature is shorter than the duration of the measurement process. Results for the numerical simulation of a gas flow in a sensor used to measure a stagnation temperature in short-term wind tunnels are presented. The conjugate problem of a sensor in a supersonic flow is solved and the flow field inside the stagnation chamber is calculated. The temperature of the thermocouple place at the end of the stagnation chamber is determined. The results of simulating the thermocouple readings depend on time and the oncoming flow parameters. The obtained readings of the stagnation temperature sensor are taken as virtual experiment data, which are processed using experimental aerodynamics methods. The “step process” and “two thermocouples” methods are used to restore the stagnation temperature. A difference in thermocouple readings is a normalized thermocouple hardware function. True temperature readings are restored by deconvolution. The restored readings are compared with the initial values of the stagnation temperature in the incoming flow to the sensor. The sources of measurement errors are determined, and the applicability of experimental methods for determining the stagnation temperature in short-term aerodynamic installations, including those with parameters decreasing with time, is substantiated.

The present study elaborates the response of a heat source along with thermomechanical loading in a modified Green-Lindsay generalized thermoelastic half-space with nonlocal and two-temperature parameters. The problem is formulated for the model under consideration by reducing the governing equations into a dimensionless form. The problem is solved by using the Laplace and Fourier transforms. The physical field quantities, such as the stresses, displacement vector components, thermodynamic temperature, and conductive temperature, are found in the domain obtained after the Laplace and Fourier transforms. Numerical inversion techniques are used to recover the equations in the physical domain. Results obtained by using various thermoelasticity theories are compared.

In the present study, entropy generation in a non-axisymmetric steady-state incompressible viscous flow over a single rotating porous disk is investigated analytically. The dimensionless form of the local and total entropy generation caused by frictional and thermal effects are derived. The effects of the injection rate and Brinkman number on the entropy generation are revealed. It is found that there exists an optimal injection rate for each Brinkman number, which minimizes the total entropy generation.

A mathematical model of unsteady oil flow to a vertical well in a circular reservoir taking into account degassing in the bottomhole zone is proposed. The effects of saturation pressure and gas factor on pressure recovery curves and their derivatives are investigated. It is shown that the saturation pressure value characterizes the radius of the degassing zone. The change in permeability in this zone is affected by both the saturation pressure and the gas factor. Based on the proposed model and using the theory of inverse problems, a method was developed for interpreting the results of hydrodynamic studies of vertical wells operating with bottomhole pressure below the saturation pressure. This method can be used to evaluate the saturation pressure and permeability of the reservoir from pressure recovery curves.

Fluid flow in a hydraulic fracture and the reservoir surrounding the fracture and the dynamics of pressure and flow rate in transient well operation were studied theoretically. Solutions describing the relationship between fluid flow rate and pressure evolution in the fracture were obtained. The main dependences of reservoir parameters and fracture characteristics on time were determined.

In order to improve the accuracy and efficiency of solving the simulation model of high-frequency pulse electrochemical machining of a cross groove, a multi-physics coupling model based on the turbulent bubble flow model coupling the electric field and temperature field models is established. The direct current average voltage is proposed to replace the high-frequency pulse voltage. Experimental results are also provided.

This paper describes the study of a linear formulation of a problem of the stability of boundary layers with a pressure gradient, which are formed in a flow around surfaces with a single-layer viscoelastic coating. Calculations account for a change in the external flow velocity in the longitudinal direction, and experimental dependences describing the coating characteristics and frequency are used. The e N method is used to estimate the influence of a compliant coating on the position of a laminar-turbulent transition region is estimated. It is shown that, even in the case of a sufficiently rigid coating, a laminar-turbulent transition in a boundary layer with a favorable pressure gradient can be delayed along the longitudinal coordinate by approximately 41%.

Effect of preliminary heat treatment of CuA_l10Fe₃Mn₂ bronze particles in the working chamber of a furnace with varying atmosphere on the process of applying coatings by cold gas-dynamic spraying and their properties is experimentally studied. It is shown that an temperature rise in the working chamber of the furnace reduces the microhardness of the material from HV_0.025 = 240 to HV_0.025 = 115. It is noted that the spraying process is accompanied by an increase in the specific mass of the coatings from 1.62 to 3.50 kg/m2. It is shown by the study of the surface structure and physical characteristics that, for the coatings obtained from the original bronze powder, porosity is 2%, the arithmetic mean of the absolute values of profile deviations within the base length R_a = 27 µm, and microhardness is HV₁ = 250. For the coatings obtained from heat-treated bronze powder, porosity is 5%, R_a = 21 µm, and microhardness is HV_0.1 = 300.