Home – Home – Jornals – Journal of Applied Mechanics and Technical Physics 2026 number 4

Data on the seeding particle distribution in the flow of a supersonic wind tunnel with electric-arc heating of the working gas are presented. The application of statistical approaches based on gray-level co-occurrence matrices (GLCM) to identify textural features corresponding to different boundary-layer flow regimes is discussed.

Experimental and computational data on the icing of a 300-mm-chord airfoil at freestream temperatures of -5 and -15 °C are compared. It is found that, at low Reynolds numbers, classical models do adequately reproduce the overall ice shape, but fail to resolve small-scale features (e.g., ridges, needles, and rivulets). The smoothing of these features is particularly pronounced for mixed-phase icing. For small unmanned aerial vehicles, this limitation is critical because small-scale ice on thin leading edges significantly alters the flow structure and heat transfer. The study demonstrates that ignoring small-scale ice structures makes it impossible to accurately predict the icing process, which calls into question the applicability of existing numerical models for analyzing the unmanned aerial vehicle icing.

Results of measurements of wall pressure fluctuations generated during the interaction of a supersonic underexpanded jet (with microjets at its nozzle exit) with an obstacle containing a coaxial orifice are presented. It is found that, within a certain range of linear parameters, microjet injection into the main supersonic jet reduces the amplitude of self-sustained oscillations caused by acoustic feedback between the nozzle and the obstacle. Outside this range, however, the presence of microjets does not significantly reduce the pressure fluctuations near the nozzle exit caused by periodic variations in the gas mass flow rate through the central orifice.

A computational framework based on the smoothed particle hydrodynamics (SPH) method for simulating the motion of multi-link fish-like bodies is presented and validated. The framework couples SPH with a multibody dynamics approach to solve the hydroelasticity problem (fluid-structure interaction) for fish-like swimmers. The solver is thoroughly verified against three benchmark problems. Comparison with published numerical results demonstrates that the proposed framework is capable of reproducing the key hydrodynamic features, including reverse Kármán vortex streets, thrust generation mechanisms, and motion-dependent performance characteristics. The developed and validated framework provides a computationally efficient tool for the design, control, and optimization of bio-inspired underwater vehicles.

The effect of a vertical AC electric field on a layer of a dielectric viscoelastic Navier-Stokes-Voigt fluid, salted from below and heated either from below or from above, is investigated using linear stability theory. The eigenvalue problem is solved exactly for stress-free boundary conditions, while the Galerkin method is employed for rigid boundaries. A numerical analysis of the influence of the electric field on the system is performed for both stationary and oscillatory convection modes. It is found that stationary convection occurs at low values of the concentration Rayleigh number, while a transition to oscillatory convection takes place at higher values. The Navier-Stokes-Voigt parameter plays a significant role in stabilizing the onset of oscillatory convection. The system is shown to be more stable when heated from above than when heated from below. The results obtained are in good agreement with available data in the literature.

A three-dimensional mathematical model for the propagation of a spontaneous hydraulic fracture in a poroelastic medium is presented, accounting for the prestressed state induced by a pre-existing propped fracture. The indicator curve behavior for an injection well experiencing spontaneous hydraulic fracturing is analyzed, and a physical interpretation of its characteristics is provided. A step-rate injection test is simulated, and the effects of the impermeable caprock thickness and the prestress due to the propped fracture on the indicator curve shape and fracture initiation pressure are evaluated. The slope of the indicator curve beyond the fracture initiation point is found to depend significantly on the fracture length and conductivity, as well as on poroelastic effects. In particular, increasing caprock thickness is revealed to raise the fracture initiation pressure due to additional stresses generated by elevated pore pressure-an effect that cannot be captured by two-dimensional models without further modifications. The simulation results demonstrate the sensitivity of the fracture initiation pressure to changes in reservoir pressure and confirm the need to account for three-dimensional poroelastic effects and prestress in the engineering design of waterflooding systems.

A mathematical model of real-gas flow to a vertical well in a fractured-porous reservoir is proposed, incorporating the pressure dependence of fracture porosity and permeability. The behavior of the bottomhole pressure and its time derivative is analyzed as a function of various formation parameters. A method for interpreting gas-dynamic well test data in fractured-porous reservoirs is developed, accounting for the pressure dependence of fracture permeability within the framework of inverse problem theory. Test calculation results are presented.

A two-dimensional problem of water-wave scattering by a completely submerged thin vertical porous barrier in the ocean is considered. The fluid is assumed to be bounded above by a free surface and below by a permeable seabed. Using Green’s integral theorem, the boundary-value problem is reduced to a hypersingular integral equation of the second kind expressed in terms of the potential difference across the plate. The equation is solved numerically using a collocation method with a finite series of Chebyshev polynomials of the second kind. The reflection and transmission coefficients are obtained as integrals involving the potential difference. The energy dissipated by the porous plate is also evaluated. Numerical results for the coefficients are presented, and the corresponding energy identity is verified. A significant effect of dual porosity is observed.

A mathematical model of conjugate heat transfer and a numerical method for estimating the temperature distribution in a model electronic unit of an unmanned aerial system filled with hydrogen and exposed to external airflow are presented. The three-dimensional mathematical model for the external aerodynamics and internal gas dynamics is based on the Reynolds-averaged Navier-Stokes equations, closed by the ideal-gas equation of state (for both air and hydrogen), the SST turbulence model, and appropriate initial and boundary conditions. The thermal state of the unit is described by the heat conduction equation. The two problems are solved in a coupled manner, thereby implementing a conjugate heat-transfer model between the external air and the internal hydrogen through the solid walls, whose thermophysical properties (heat capacity, thermal conductivity, and density) are specified as functions of temperature. The heat dissipation from the circuit boards of the model electronic unit is prescribed as a thermal boundary condition on the surfaces of the heat-generating components. Temperature distributions in various cross sections of the structure are obtained.

The linear stability of a combination of two mutually perpendicular flows in an inclined plane layer is investigated: a convective flow driven by a transverse temperature difference and a plane Poiseuille flow induced by a horizontal pressure gradient. Stability regime maps are constructed in the Reynolds number-Grashof number plane for various layer inclination angles, as well as disturbance regime maps in the inclination angle-Reynolds number plane. When the temperature of the upper boundary of the layer exceeds that of the lower boundary, the combined flow can be stabilized at Reynolds numbers higher than the critical Reynolds number for the plane Poiseuille flow without thermal stratification.

For a power-law temperature dependence of the viscosity coefficient, the problem of steady Poiseuille flow in a channel with nonuniformly heated walls is reduced to a three-parameter boundary-value problem for a system of third-order ordinary differential equations. In the absence of a pressure drop, the problem admits a solution describing the temperature distribution in a fluid at rest. This solution exists over a finite interval between the negative and positive critical values of the dimensionless temperature gradient at the channel walls. At small values of the Péclet number (based on the pressure drop), the first solution branch bifurcates from the quiescent state. Two additional branches are found when the wall temperature gradient exceeds the critical values. Thus, in the region of negative gradients, two solutions exist for the same parameter values, differing in flow rate and wall heat flux. For wall temperature gradients exceeding the positive critical value, the third branch is a continuation of the first. A distinctive feature of the second and third branches is that, as the Péclet number tends to zero, the flow rate tends to a nonzero value.

A new approach to measuring the local heat transfer coefficient during condensation of saturated water vapor on the surface of a horizontal pipe is proposed. The heat transfer coefficient values are determined from direct measurements of the heat flux density using gradient heat flux thermometry and of the pipe surface temperature using thermocouples. Results are presented for a test section supplied with saturated water vapor at a temperature close to 100 °C and a flow rate varying from 4 to 10 kg/h; the cooling water flow rate was 130 kg/h. Angular distributions of temperature, heat flux density, and heat transfer coefficient during condensation are constructed. Depending on the vapor flow rate, either mixed or film condensation is found to develop on the surface. The proposed approach provides a relative uncertainty in the local heat transfer coefficient of less than 8 %.

This paper describes a modification of the Sieverts method for measuring hydrogen absorption and desorption isotherms (PCT isotherms) for a sample of an AB₅-type intermetallic compound with the composition LaNi_4.8Al_0.2. The modification consists in performing measurements by stepwise changing the temperature of the working vessel containing the sample at a fixed hydrogen concentration, rather than by adding or removing discrete hydrogen portions at a constant temperature. Hydrogen absorption and desorption isotherms obtained by the classical and modified methods for the same sample are compared. The modified Sieverts method is shown to be more accurate than the classical version, due to the elimination of cumulative measurement error.

A numerical model of spinodal decomposition of a thermally unstable, partially miscible liquid under pulsed heating is developed. The model is based on a system of differential equations describing heat and mass transfer. Simulations are performed over time intervals of up to 40 ms. When a cylindrical probe is heated, the surrounding liquid separates into two immiscible phases. Due to the surface tension gradient (Marangoni effect), droplets of these phases move both toward and away from the probe, leading to a significant enhancement of heat transfer. The resulting time-dependent probe power and the relative change in the heat transfer coefficient are in good agreement with experimental data obtained from pulsed heating of an aqueous PPG-425 solution.

A physical and mathematical model of ice accretion on an axisymmetric body rotating in an airflow containing ice particles with various sphericities is proposed. Upon impact with the surface, a portion of the particle mass is deposited. A numerical study is performed to determine the ice shape, accounting for possible detachment by centrifugal force. The effects of viscosity and turbulence of the carrier gas on the processes under consideration are taken into account.

The problem of verifying computational results for liquid-metal coolant flow in nuclear reactor fuel assemblies with spacer grids is addressed. The verification results demonstrate that the CADFlo software package provides high accuracy in simulating both laminar and fully developed turbulent flows. For heat transfer problems involving liquid-metal coolants in fuel assemblies, good agreement is obtained between the computed temperature distributions and hydraulic resistance coefficients and the experimental data.

Wave reflection in a nonlocal biothermoelastic medium described by a hyperbolic two-temperature model is investigated within the framework of the refined Lord-Shulman model. A two-dimensional half-space with impedance-type boundary conditions is considered. The governing equations are reduced to dimensionless form and solved using potential functions. The existence of three longitudinal waves and one transverse wave is demonstrated. Reflection coefficients and the corresponding energy ratios are obtained. The refined Lord-Shulman model is compared with the classical model. Although the plane-wave reflection problem is idealized, it provides a useful theoretical basis for studying the influence of biological tissue parameters on the energy of reflected waves.

An experimental study of plastic strain localization during static uniaxial tensile testing of steel specimens with asymmetric edge stress concentrators is performed. The study employs modern thermal imaging equipment capable of recording the temporal evolution of temperature fields during deformation. The proposed experimental methodology, based on infrared thermography, is shown to be applicable for investigating the kinetics of elastoplastic deformation and for determining the ultimate state of the material in the stress concentration zone.

The synthesis of a composite material based on the metal hydride alloy TiFe_0.85Mn_0.05 and ABS polymer is presented. The thermal properties of the samples are studied using thermogravimetric analysis and differential scanning calorimetry. The morphology of the composite material is examined by scanning electron microscopy. The effect of the polymer on the hydrogen sorption characteristics of the intermetallic compound TiFe_0.85Mn_0.05 is investigated. The maximum hydrogen mass fraction in the synthesized composite material is found to be 1.3 % at a temperature of 30 °C and a pressure of 30 atm.

A method for enhancing the corner strength of thin-walled square tubes by incorporating four corner reinforcements consisting of stiffeners with or without lightweight polyurethane foam fillers is proposed and validated. Three-point bending tests of thin-walled square tubes with corner reinforcement are simulated using the ABAQUS/Explicit software package. The numerical results show that corner reinforcement significantly changes the cross-sectional deformation mode of the tubes. The specific energy absorption of tubes with corner reinforcements is substantially higher than that of unreinforced tubes. Based on an analysis of the cross-sectional deformation, it is proposed to remove the two lower corner reinforcements to further increase the specific energy absorption. The specific energy absorption of a tube reinforced with only the two upper corner reinforcements is 2.24 times higher than that of a conventional hollow square tube and also exceeds that of the proposed configurations with four reinforcements.