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The variable N-factor method, which is one of the most effective modern approaches for predicting the laminar-turbulent transition location in boundary layers, is improved. The determination of the threshold N-factor for swept wings is refined by taking into account the range of transverse roughness scales on the wing leading edge that are dangerous from the standpoint of cross-flow instability and boundary-layer receptivity. The proposed modification does not require additional numerical analysis, as it is based on standard linear stability theory calculations and empirical data on the efficiency of boundary-layer receptivity to roughness in the generation of cross-flow instability vortices. The resulting dependences of the critical N-factor on the dimensionless leading-edge roughness are presented and calibrated against our own experimental data.

The interaction of a plane oblique shock wave with a vortex system arising from flow separation at the edge of a dihedral model with an opening angle of 270° is examined. The shock generator, which is a thin plate, and the model are positioned at the same angle of attack of 16°. A downstream-expanding separation vortex is generated by the pressure difference between the upper and side faces of the model, while the shock wave incident from the generator causes extensive boundary-layer separation on the surface of the side face. The complex interaction between the shock-induced separated flow and the stalled flow leads to the formation of a cylindrical vortex detached from the surface.

The effect of preloading on the porosity change of water-saturated clay soils is investigated. A numerical model of one-dimensional filtration in a porous medium with variable permeability dependent on the applied load is employed for the analysis. The boundary conditions are specified in terms of filtration velocities, and the load effect is modeled through changes in the permeability coefficient. The results obtained are shown to be in good agreement with experimental data. The proposed description of porosity evolution enables more accurate prediction of soil behavior during fluid filtration.

A numerical study of the problem of symmetric capillary filling with a viscous incompressible fluid in the nonisothermal case is performed. The flow is described using the Pavlovskii model. In this problem, the dynamic contact angle issue arises when the impingement angle differs from 0 or π. This issue originates from the incompatibility between the free-surface boundary conditions and the no-slip condition on the solid wall in the vicinity of the moving three-phase contact line. To close the formulation, the no-slip condition is replaced by a generalized Navier slip condition. The influence of the dynamic contact angle on the temperature near the three-phase contact line is investigated for flows with low capillary numbers.

A method for controlling the heat flux density during boiling of water in the context of modeling a two-phase cooling system for power electronics is examined. The challenge of increasing thermal loads and amplifying power devices lies in the inability to remove such high heat fluxes from the power module. The most efficient heat removal mechanism, boiling, is limited by the onset of a boiling crisis. A simplified method for enhancing vapor removal from the heat transfer surface using adiabatic inserts is proposed. The inserts break up vapor bubbles into smaller ones, reducing the likelihood of vapor film formation on the surface. Additionally, they promote liquid sliding along the unheated isothermal insert wall, unimpeded by vapor bubbles. The primary experimental technique is gradient heatmetry. The dependence of the local heat flux density on the simulated power module temperature is obtained for various fin pitches with adiabatic inserts. The effectiveness of the proposed heat flux density control method is demonstrated.

Results of a numerical analysis of the transition from steady to oscillatory laminar flow in gravitational convection of an incompressible fluid in a closed cavity heated from the side are presented for various Grashof and Prandtl numbers. The influence of the nonlinear dependence of convective flow on the Prandtl number on the flow structure and its temperature and concentration stratification is demonstrated.

The influence of tube walls on laser-induced subcooled boiling at the end of a thin laser fiber placed in a tube is investigated numerically. It is shown that, in the case of tubes with a radius fourfold greater than the bubble radius at maximum expansion, the velocity of the cumulative jet formed upon collapse of the vapor bubble is equal to that in an unbounded space. As the tube radius decreases, the jet velocity decreases due to rebound , which is bubble re-expansion that prevents jet formation. A further reduction in radius leads to a predominance of axial fluid flow within the tube and subsequent jet destruction. The influence of tube radius and length, as well as fiber length, on the bubble shape and volumetric flow rates through the tube end sections is demonstrated. Dimensionless parameters at which the volumetric flow rate through these sections reaches its maximum are identified, which is particularly important for medical applications.

Heterogeneous boron carbide-based ceramics with vanadium diboride additions, produced by uniaxial hot pressing, are investigated. During sintering, vanadium diboride was synthesized by carboborothermic reduction from vanadium oxide, as confirmed by X-ray diffraction analysis. The microstructure of the B₄C-VB₂ heterogeneous ceramics consists of uniformly distributed vanadium diboride grains in a boron carbide matrix. Increasing the vanadium diboride molar fraction from 0 to 5% is found to increase the fracture toughness of the ceramics from 2.0 to 5.5 MPa·m^1/2.

This paper describes the Love wave propagation in a layer overlying a half-space consisting of relatively thin layers, with slip at the contact boundaries. The slip contact conditions in the finely layered medium are specified by a linear Winkler-type condition for shear stresses. This medium is described by an asymptotically exact homogenized model that includes second-order terms in a small parameter-the layer thickness. Dispersion relations for Love waves are derived. Typical dispersion curves and through-thickness wave profiles are constructed. A parametric analysis is performed, revealing differences from the case of a homogeneous half-space.

The characteristics of the elastoplastic transition and subsequent hardening in the strain curve segment up to 4% deformation are investigated in homogeneous AMg5 alloy specimens and in specimens containing a friction stir weld. Depending on the strain rate, the elastoplastic transition is found to occur through the formation and propagation of localized plasticity autowaves of switching or excitation types. These autowaves form at stress concentrators, such as weld seam boundaries.