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A flat methane-air mixture flame was numerically simulated in a longitudinal electric field at various fuel-to-fuel ratios. A computational code developed in the OpenFOAM based on the reactingParcelFoam solver was used for numerical calculations. The results showed that the predicted value of the ion current correlates with the experimental data. The best agreement is achieved in the lean (φ ≤ 0.8) and rich (φ ≥ 1.3) flames. The greatest discrepancy is recorded for the regime of fuel-air equivalence ratio φ = 0.9. The maximum ion current is achieved at φ = 1.1, which corresponds to the experimental results. The obtained data demonstrate the adequacy of the developed code in predicting the flame current value. Calculation data indicate an increase in CH concentration by 20.5% and O concentration by 2.0% when exposed to an electric field; the interaction of these components is the initiating reaction in the formation of charged particles in hydrocarbon flames.

Stationary perturbations of equations of the boundary layer stability are studied for subsonic and supersonic flow past a plate. For two-dimensional perturbations, the results obtained are in good agreement with existing literature data. Three-dimensional perturbations resembling longitudinal structures are studied for the first time. It is established that the amplitude of boundary layer perturbations of longitudinal velocity and temperature has a bell-shaped form, whose maxima position in the Dorodnitsyn-Howarth variables is conservative with respect to changes in the Mach number, Reynolds number, and wave number along the lateral coordinate. Moreover, the intensity of perturbation attenuation along the longitudinal coordinate and the phase shift of the boundary layer perturbation increase with an increase in the above quantities. The largest phase changes are observed for the lateral velocity.

Using a modified mean flux method, a numerical analysis was performed for highly asymmetric scattering phase functions. To solve the radiative transfer equation, the delta-Eddington approximation is used. Radiative-conductive heat transfer in a flat layer of an anisotropically scattering medium was calculated for the Henyey-Greenstein phase function and the transport approximation as an example.

T effect of wettability parameters of a porous heater material on heat transfer during boiling was investigated using a hybrid numerical model based on the lattice Boltzmann method and the heat transfer equation. By simulating the boiling process on a porous heater with a regular hexagonal structure of rectangular metal heat-conducting elements at various thermal heads, boiling curves and coefficients of heat transfer enhancement/degradation were obtained for lyophilic, lyophobic, and neutral heater materials. The results showed that at moderately low thermal heads, the heat transfer coefficient on the lyophobic heater is higher than that for a surface with neutral wettability due to earlier initiation of the vapor phase, while at high thermal heads, heat transfer on the lyophilic heater is the greatest. It was also shown that the temperature of boiling beginning is minimal for lyophobic heaters and maximal for lyophilic heaters, and the boiling crisis does not occur on a porous heater of any wettability even at the maximum heat heads considered.

The problem of ignition and combustion of a region expanding over time is considered. Combustion was initiated using a pulsed-periodic energy source. The influence of pulse frequency and flow velocity on ignition was revealed. Autoignition of a laminar hydrogen jet diluted with nitrogen in a co-current heated air flow was numerically simulated. A transient reacting mixing layer between two flows (air and fuel) with different velocities and temperatures was studied.

Percolation theory is widely used to study heat transfer and other kinetic processes in systems with disordered structures. This paper proposes a phenomenological approach combining methods of percolation theory and multifractal analysis to model a percolation cluster in a three-dimensional infinite medium with multifractal properties. Based on the developed model, unambiguous numerical values for topological critical indices and the critical conductivity index were obtained, previously unknown relationships between critical indices were revealed, threshold conditions that separate qualitatively different regimes of system behavior in the scales of correlation length were determined, and a relationship between the systems order parameter and the golden ratio was established, which indicates the universal nature of the identified dependences.

Percolation theory is widely used to study heat transfer and other kinetic processes in systems with disordered structures. This paper proposes a phenomenological approach combining methods of percolation theory and multifractal analysis to model a percolation cluster in a three-dimensional infinite medium with multifractal properties. Based on the developed model, unambiguous numerical values for topological critical indices and the critical conductivity index were obtained, previously unknown relationships between critical indices were revealed, threshold conditions that separate qualitatively different regimes of system behavior in the scales of correlation length were determined, and a relationship between the systems order parameter and the golden ratio was established, which indicates the universal nature of the identified dependences.

Experimental results on the temperature distribution in a jet of nitrogen flowing from a long pipe into a vacuum under laminar and turbulent flow conditions are presented. A temperature increase downstream was observed under turbulent flow conditions compared to laminar flow conditions. It is concluded that the temperature increase is associated with the turbulent energy relaxation.

Despite numerous studies, many aspects of ignition and propagation of combustion and detonation waves in combustible mixtures remain insufficiently understood, complicating the scientifically sound management of such processes. This paper presents new data on the various stages of ignition and flame front propagation in a flat (two-dimensional) channel of constant cross-section. The experimentally observed main flame instabilities (manifested in the significant non-uniformity and non-stationarity of the combustion front), the phenomenon of flame blowoff (disappearance of glow), and the effect of flame transition to a self-sustaining propagation mode are discussed. Attention is drawn to the problems of the emergence of new ignition sources in the flame front, including explosive micro-sources that facilitate the subsequent transition of combustion to detonation. A number of new features in the physics and dynamics of flame propagation are identified.

Despite extensive research, many aspects of ignition and propagation of combustion and detonation waves in combustible mixtures remain poorly understood, complicating scientifically sound control of such processes. The first part of this paper presented new experimental data on various stages of ignition and flame front propagation in a flat (two-dimensional) channel of constant cross-section. This paper presents results on the little-studied area of combustion wave behavior with changing channel geometric dimensions (so-called flame diffraction). Characteristic processes in the behavior of a turbulent flame as it transitions from a narrow channel to a wide one are established: from flame breakdown and loss of front glow with incomplete combustion of the mixture in a wide channel to the emergence of new explosive microcenters due to the development of expanding flame instabilities and collisions of turbulent flame tongues, leading to the generation of detonation-like waves.