卷 89, 编号 7 (2025)

We discussed the incoherent decomposition method, which allows us to describe the intermediate asymptotics of perturbation growth in the theory of kinematic dynamo and the theory of transport of passive scalar. This approach allows to take a fresh look at the nature of dynamo at large Prandtl numbers.

In fully developed turbulence, according to Kolmogorov's hypothesis, an extended range of scales, called the inertial range, exists, in which neither external nor viscous forces play an appreciable role, and all statistical properties are determined by the dissipation rate of kinetic energy. Turbulent flows, in which the influence of external forces on scales corresponding to the inertial interval is of fundamental importance, are common in nature. Then, the usual integrals of motion, such as the energy of velocity pulsations, hydrodynamic helicity, etc. cease to be so and other quadratic quantities that include scale dependence become integrals of motion. At the same time, from the point of view of the usual integrals of motion, cascade processes become non-conservative. In this work, this idea is developed in frame of shell models of MHD-turbulence. The approach introduced allows us to describe some special regimes of cascade processes in MHD-turbulence.

The correlation analysis of the interaction of nonlinear waves on the surface of a magnetic fluid in the regime of developed magneto-hydrodynamic wave turbulence is carried out. It is shown that the horizontal magnetic field leads to compression of the resonant interaction curve. From the physical point of view, this process corresponds to anisotropic transfer of magnetic energy into the energy of capillary waves traveling perpendicular to the external field direction.

We investigated the features of deformation of microemulsion droplets with low interfacial tension at the droplet-medium interface under the influence of magnetic fields in a wide temperature range. The nature of the temperature dependence of the microdroplet deformation parameter on the intensity of both constant and alternating magnetic fields has been established. Differences in the deformation patterns of microdroplets obtained from magnetic fluids with different structural states have been revealed.

We studied the features of the photo-thermocapillary effect in magnetic colloids. The effect of the magnetic field on the manifestation of the effect in such media was studied, the features of changing the size and shape of the thermocapillary response depending on the dimensional parameters of the cell with the sample were established. A conclusion is made about the possibility of successful control of the effect using a magnetic field.

Magnetic fields play an important role in the structure and evolution of accretion disks. There are strong arguments related to the action of the dynamo mechanism. The structure of the magnetic field that can be obtained using various approximations is discussed. Particular attention is paid to the possibility of the emergence of essentially non-axisymmetric solutions.

The occurrence of the magnetic fields of galaxies is usually explained by the action of the dynamo mechanism. Nevertheless, at distances of the order of 15-20 kpc, the action of the dynamo is significantly weakened. The magnetic field in these regions can be described by other mechanisms, for example, magnetorotational instability. In this work, solutions that correspond to both the mechanisms of dynamo and magnetorotational instability have been found.

We presented the results of a numerical study of the flow of an electrically conductive fluid under the influence of a transverse magnetic field, considering the varying electrical conductivity of the wall of a round pipe measuring 40×2 mm². The fluid under investigation is a simulated salt melt (a 20% aqueous solution of potassium hydroxide), whose concentration allows for achieving the maximum value of the Hartmann number.

The use of Z-pinch facilities makes it possible to carry out well-controlled and diagnosable laboratory experiments to study laboratory jets having scaling parameters close to those of jets of young stars. It was found that a low-concentration region is formed after the first supersonic ejection, allowing subsequent ejections to propagate collimated. An exact solution of the generalized Grad-Shafranov equation for axisymmetric plasma flows was also obtained and the interaction of the plasma ejection with the gas was numerically modelled, which agrees well with the experimental data.

We presented an induction sensor for controlling the boundary and conductivity of the medium. A refined mathematical model of the device is given. The dependencies of the sensor signal on the distance to the electrically conductive cylinder and on the position of its upper boundary are obtained experimentally and numerically. The behaviour of the system response on media with different electrical conductivity: copper, duralumin, stainless steel and lead-tin cylinders with different mass fraction of copper powder is studied.

We compared three different approaches for forecasting a time series of the solar activity index: iterations of a single-step model, an independent single-step forecast for each subsequent month, and a single multi-step forecast for the entire period. In each approach we use a neural network model as the forecasting model with the aid of a theoretical series of solutions obtained from the physical model.

The stability of the mixing layer in a cylindrical cell between two counter-rotating vortex flows created by electromagnetic forces is numerically investigated. The flow is shown in the process of instability development. The resulting Kelvin–Helmholtz instability becomes a source of small disturbances and leads to turbulent mixing of the liquid. The second and third flow modes make the greatest contribution to the development of disturbances.

A complex of computational and experimental studies of liquid metal flows in a combined pipe-in-channel system with double cooling in a transverse magnetic field and without it has been performed. The results of numerical simulation are compared with the experiment. The configuration of the flow and its structure significantly depends on the presence of a transverse magnetic field, as well as on the connection of a natural circulation loop and its cooling.