Home – Home – Jornals – Thermophysics and Aeromechanics 2026 number 4

This review summarizes the results of recent experimental studies on the diffusion combustion of hydrogen microjets. It examines the influence of nozzle geometry, jet profile and exit velocity, and gravitational factors on flame structure. Particular attention is paid to the combustion of hydrogen mixtures and the interaction mechanisms between a circular supersonic air jet and a coaxial (co-flowing) hydrogen stream.

This study experimentally investigates the influence of silicon substrate temperature and titanium dioxide (TiO2) nanofluid concentration on the dynamics of the three-phase contact line and the morphology of deposits formed during droplet evaporation. The nanofluid was produced via pulsed laser ablation in liquid. Mass concentrations of 8.7 × 10⁻⁴ wt% and 2.1 × 10⁻³ wt% were examined at substrate temperatures ranging from 80 to 140 °C. It was found that the addition of TiO2 nanoparticles extends the duration of the three-phase contact line pinning stage. Consequently, the contact line diameter changes in a stepwise manner, leading to the formation of concentric ring structures of deposited material with a characteristic spacing. At surface temperatures of 80 and 100 °C, radial capillary transport dominates, resulting in the formation of a "coffee ring." Increasing the surface temperature to 120°C initiates nucleate boiling, which expands the deposition zone, whereas at 140°C, fully developed nucleate boiling disrupts steady particle transport and leads to a redistribution of the deposit.

Based on a system of equations, including equations for the saturated vapor pressure and density, the saturated liquid density, and the ‘’apparent’’ heat of vaporization, the phase equilibrium line of mercury is described in the temperature range from the triple point to the critical point. The saturated vapor pressure line within the proposed approach satisfies the requirements of the scaling theory of the critical point, and the saturation line is developed using the Clausius-Clapeyron equation, the mean diameter, and the order parameter of the renormalization group. All of these equations are consistent with respect to critical indices and parameters. Within the proposed model of the phase equilibrium line of mercury, all components of the equations describing the vapor and liquid branches of the coexistence curve have exponents calculated using scaling theory.

This paper systematizes current data on the vacuum disintegration of materials of diverse nature-ranging from gold-bearing clay rocks to biopolymers and pharmaceutical substances. It is demonstrated, both experimentally and theoretically, that these processes are governed by a unified physical principle: the non-equilibrium phase transition of capillary- or chemically bound water during a rapid decrease in ambient pressure. Four dominant disintegration mechanisms are identified (degassing-induced cracking, sublimation fragmentation, thermal-gradient cracking, and capillary cavitation), and order-of-magnitude estimates of the resulting stresses are provided. A dimensionless regime criterion is introduced to determine the disintegration type independently of the specific material. The existence of an optimal initial moisture content is demonstrated (20-25% for clays, 10-15% for starch). Examples of industrial implementation in the pharmaceutical and food industries, as well as in soil vacuum leaching, are presented; prospects for applying the method across various technological chains are discussed.

This paper presents the results of an experimental study on the wave characteristics of an R1233zd(E) refrigerant film flowing down a vertical flat surface. The experiments were conducted under saturation conditions at a temperature of 26.7°C and an absolute pressure of approximately 1.4 bar. The film Reynolds numbers investigated-Re_f = 520, 1040, and 1560-correspond to the laminar-wavy flow regime. High-speed video recording was used to determine the length, phase velocity, and passage frequency of large three-dimensional waves. It is shown that as the liquid flow rate increases, the length of the large waves decreases, whereas their phase velocity and passage frequency increase. The measured phase velocities are compared with experimental data for a liquid nitrogen film and with calculated estimates based on the Kholpanov-Shkadov approximation and the correlation by Nosoko et al. It is demonstrated that the Kholpanov-Shkadov relationship significantly overestimates the phase velocity of large waves, while the correlation by Nosoko et al. better captures the order of magnitude but yields an underestimate.

Efficient thermal management in modern compact electronics requires surfaces with controlled wettability and strong wicking capability. Although laser-textured silicon is widely studied for its optical response, its wetting and capillary transport properties remain less explored. In this work, silicon wafers were processed using a nanosecond Nd:YAG laser to create two types of textured surfaces, GraySi and BlackSi. The resulting microstructures were characterized in terms of morphology, wettability, and wicking performance using the Wi number. BlackSi exhibited significantly greater wicking capability (Wi = 2.3) compared to GraySi (Wi = 1.3). The evaporation behavior of water droplets was also investigated. Laser texturing was shown to reduce evaporation time due to enhanced hydrophilicity and, importantly, to modify the evaporation mode: BlackSi maintained a constant contact radius regime, while GraySi transitioned to a mixed regime.

The results of mathematical modeling of the flow structure, turbulence characteristic and heat transfer in a convective column occurring during the ground forest fire are presented. The detailed analysis of the temperature, vertical velocity and turbulent kinetic energy distributions along the column's height is conducted. The regression relationships for the change in velocity and temperature along the convective column axis with height are obtained.

The work is devoted to studying the dependence of the boiling process on a porous heater on the force of gravity using a numerical hybrid model based on the method of lattice Boltzmann equations and the heat transfer equation. To test the model, we first studied the dynamics of the growth and separation of a single bubble during boiling on a single flat heater at various values of the gravitational acceleration (from 0.2 g to normal g). The obtained dependences of the separation diameter, separation frequency and average heat flow on the force of gravity confirmed qualitative agreement with the data available in the literature. As a result of modeling the boiling process on a porous heater with an ordered structure of solid heat-conducting rectangular elements, boiling curves and the dependence of the heat transfer degradation coefficient on the thermal pressure were obtained for various values of the acceleration of gravity. It is shown that with a decrease in gravity, the heat flux removed from the porous heater decreases throughout the entire range of thermal pressures, and the boiling crisis begins at a lower thermal pressure.

This study provides numerical and experimental validation for forming a planar detonation front within a pulsed detonation prechamber (PDP) designed for simultaneous, full-area ignition of high-speed flows. Using a two-stage simulation and experimental test rig, optimal geometries and operating conditions for a stoichiometric methane-oxygen mixture were established for the prechamber, manifold, and pre-detonation tube. Investigations demonstrate high convergence between numerical and experimental results for a single detonation pulse, confirming the invariance of the planar detonation wave front regardless of pre-filling conditions. Analysis substantiates that measured velocity peaks up to 3,500 m/s, exceeding the 2,380 m/s Chapman-Jouguet velocity, result from the geometric effect of apparent phase velocity, supporting application in advanced air-breathing engines.

The density of liquid rubidium-lead alloys containing 40, 45, 55, and 60 at. % Pb was measured for the first time using the gamma-ray attenuation method (transmission of a narrow gamma-ray beam through the sample) in the temperature range from the liquidus to ~1000 K. Based on the obtained results and data for the Rb₅₀Pb₅₀ melt previously investigated by the authors, the concentration dependencies of the molar volume, relative excess molar volume, and volumetric thermal expansion coefficient were determined for the liquid Rb-Pb system. These dependencies deviate significantly from those characteristic of ideal solutions, confirming a tendency toward the formation of chemical short-range order in the liquid state.

This paper presents the results of the verification and validation of a computational method for modeling two-phase immiscible flows of non-Newtonian fluids in porous media with interface resolution. The mathematical model is based on solving the Navier-Stokes equations within the framework of the well-known Volume of Fluid (VOF) method, accounting for interfacial tension forces and fluid rheology via a non-linear viscoplastic medium model based on the generalized viscosity approach. The developed method was tested on problems involving the displacement of model hydrocarbons by a xanthan gum biopolymer solution in a microfluidic chip simulating a porous medium and in a digital model of an actual core sample with a resolution of 200×200×200 voxels. The calculation results were compared with data from a microfluidic experiment and with calculations performed using the Ansys Fluent CFD code. The testing demonstrated that the numerical simulation results for polymer flooding obtained using the developed method show good qualitative and quantitative agreement with microfluidic experimental data and numerical solutions obtained using Ansys Fluent.

As part of efforts to incorporate luminescent pressure transducers (LPTs) into the suite of experimental diagnostic methods, numerical modeling of the flow within the gas-dynamic duct of a wind tunnel was conducted, specifically addressing the analysis of the sonic boom near-field. Expected pressure levels generated by a test model were determined for the surfaces of both flat and curved measurement plates, which serve as substrates for the LPT coating. It was demonstrated that, compared to a flat plate, a curved plate provides a larger measurement area; however, the flat plate yields lower measurement uncertainty.

Inhalation drug delivery is becoming crucial in the treatment of a wide range of conditions, including those not directly related to the respiratory system. The therapy effectiveness is determined by deposition - the drug deposited proportion in the target areas of the respiratory tract. Despite constant improvements in inhalation devices, drug deposition in the therapeutic target rarely exceeds 60%. This is due to the inhaler design features and the dispersed system physicochemical properties, as well as patient inhalation technique errors. Pathological changes in physiological barriers and the architecture of the tracheobronchial tree also have a critical impact on deposition, potentially significantly reducing it. Conversely, maximum deposition may be limited by imperfect delivery systems and the distribution of drug particles by size, velocity, and target areas of the respiratory tract. In this study, we propose a predictive model for managing aerosol flows in the airways, aimed at achieving maximum deposition, taking into account the individual anatomical and physiological characteristics of the patient (airway physiology and airway architecture). The mathematical apparatus for spatial modeling was developed in the COMSOL Multiphysics environment using the Heat Transfer, Fluid Flow, and Particle Tracing modules, as well as user-defined functions. It was found that increasing body temperature from 309.75 K to 312.15 K enhances aerosol evaporation, reducing their diameter and redistributing deposition between airway compartments. It was shown that airway architecture critically influences deposition asymmetry: for geometries with pronounced anatomical asymmetry, the difference in deposition between the right and left bronchus reaches 60-80%, while for symmetrical geometries it does not exceed 10%. The obtained results substantiate the need for personalization of inhalation therapy based on body temperature and individual anatomy of the patient, which opens up opportunities for increasing the effectiveness of the treatment of bronchopulmonary diseases.

The processes of microdroplet formation and sorting in a deterministic lateral displacement (DLD) array involving immiscible liquid flows were experimentally investigated. It is shown that as large dispersed-phase slugs move along the DLD array, daughter microdroplets detach via a mechanism resembling the tip-streaming regime. It was found that microdroplets predominantly follow streamlines and are distributed among the DLD chip's outlet channels, whereas large slugs move along displacement trajectories determined by the array geometry. The results demonstrate the potential of using DLD arrays for the simultaneous formation and sorting of microdroplets.

The work uses the neurosurrogate optimization method to refine the skeletal chemical-kinetic mechanism of KCPsur, which predicts the combustion rate of the model 4-component surrogate aviation fuel SU4 (a mixture of n-decane, isocetane, methylcyclohexane and tetralin). Multilayer perceptron trained on 34 variations of 5 pre-exponential multipliers of rate constants of chemical reactions that have the highest sensitivity coefficient of laminar combustion rate (flow rate) A-factor sensitivity) at 27 control points, was used instead of time-consuming calculations of the speed of propagation of laminar flames in the CHEMKIN software package. To optimize the rate constants of the selected reactions responsible for the conversion of tetralin, the gradient descent method was used, which made it possible to obtain a refined KCPsur_neural mechanism. The new chemical-kinetic model more accurately describes the laminar flame propagation velocity (LBV) of kerosene-air mixtures under lean and near-stoichiometric conditions (φ = 0.70 - 1.05) at pressures up to 8 atm, surpassing the accuracy of the original KCPsur and, in some cases, the detailed CRECK mechanism. An important feature of KCPsur_neural is its ability to correctly describe the concentration profiles of a number of important intermediates in the flame of a SU4/O₂/Ar mixture, which indicates a weak influence of the rate constants of refined reactions on the structure of the studied flames. This opens up the possibility of using two independent neurosurrogate models in the future to optimize fuel combustion mechanisms: one to optimize them with respect to LBV, the other to describe the flame structure with the formation of separate training samples of a smaller total dimension. It is shown that the proposed approach speeds up the optimization of reaction rate constants by approximately 106 times when using a limited training set. The results demonstrate the high effectiveness of using machine learning to overcome the rigidity of reduced combustion models and expand their applicability to conditions relevant to aircraft engine combustion chambers.

A numerical study of the dynamics of far-field shock waves from a slender body of revolution with a disk has been carried out. The disk is placed in front of the body at an angle to the freestream airflow. The possibility of reducing the intensity of far-field shock waves is demonstrated. An increase in the freestream velocity reduces the range of disk inclination angles over which a decrease in shock waves intensity can be achieved.