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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.

The problem of optimizing the bearing capacity of a stringer panel with a hole and a straight crack propagating from its contour is considered. The goal is to determine a hole contour at which the stress intensity factor in the vicinity of the crack tip is equal to zero (i.e., the crack is immobile) and at which the maximum circumferential stress is the smallest. A minimization problem is solved using the method of successive approximations, the minimax criterion, and the simplex algorithm.

This paper presents a volumetric feeder of non-free-flowing powders which is comparable in dosing precision to weighing systems. The efficiency of the main units was studied numerically (using the discrete element method) and experimentally. A continuous high-precision volumetric feeder design is proposed.

The spatial vibrations of a pipeline on two supports vibrating in the vertical direction with equal amplitudes and phases are considered. The pipeline movement consists of rotation (rolling) around a straight line passing through the supports and bending deformation. It is assumed that the bending occurs in the rolling plane without torsional deformation. Nonlinear equations of bending and angular motion of the pipeline are used. The pipeline movement was studied in the case where the bending is much more influenced by the internal pressure of the medium in the pipe than by its weight. The ranges of input parameters in which the upper and lower bent states of the pipeline are stable are determined by analogy with the Kapitza pendulum. Numerical calculations were carried out for a reinforced magnesium tube filled with methane.

The initiation of an edge annular longitudinal shear crack (III fracture mode) during torsion of a circular cross-section bar made of an elastoplastic material with ultimate strain is considered. The fracture process of such materials is described using a modified Leonov-Panasyuk-Dugdale model, which uses an additional parameter - the diameter of the plastic zone (the width of the prefracture zone). To obtain the critical parameters of quasibrittle fracture, a double (sufficient) strength criterion for mode III cracks in an elastoplastic material is proposed. Diagrams of quasibrittle fracture of a circular shaft with an edge crack are plotted. For quasiductile and ductile types of fracture, the ultimate loads are found numerically by the finite element method. The difference between the numerical and analytical models is that the characteristics of the investigated materials correspond to the deformation modes in full-scale yielding. It is found that the results of numerical experiments are in good agreement with the results of calculations using the analytical model of fracture of specimens during torsion in the mode of small-scale plastic flow.