Fluid Dynamics最新文献

Asymmetry of a core-collapse supernova explosion is an effective mechanism for a large kick velocity generation of neutron stars and black holes, formed during such violent and bright events. In this work, we conduct MHD simulations of a magnetorotational supernova explosion with an offset dipole field for two progenitor models of massive stars with zero-age main sequence masses of 20 and 35 ({{M}_{ odot }}). The offset position of the dipole field results in a development of equatorially asymmetric outflows, leading to a formation of kick velocity of the protoneturon star. The results show, that the initial mass of the massive star could strongly affect the acquired protoneutron star kicks, while their estimated values are in order of several hundreds of kilometers per second at ( sim 1) s after the core bounce.

The influence of  V.B. Baranov on the author’s work on the calculations of transport coefficients in partially ionized two-temperature plasma in magnetic field is considered, and the results of this work are presented briefly.

Since cometary dust interacts with electrons and ions of the surrounding plasma, as well as with solar radiation, the dust becomes charged. As a result, it is possible to treat the medium surrounding the comet nucleus as a dusty plasma. The purpose of the present paper is to discuss plasma-dust processes in comet physics. It is shown that plasma-dust processes can have significant manifestations in the formation of the bow shock formed due to the interaction of the comet’s coma with the solar wind, as well as in situations when the comet is far from the Sun.

Interstellar dust particles penetrate the heliosphere because of the relative motion of the Sun and the local interstellar medium. Inside the heliosphere, trajectories of dust grains deflect from the initial direction due to the action of three forces: gravitational attraction to the Sun, solar radiation pressure, and electromagnetic force. As a result, the distribution of dust grains becomes highly inhomogeneous. In our previous works, we demonstrated that under the influence of electromagnetic force, the envelopes of trajectories, or caustics, appear. We also studied the effects of velocity dispersion and the time-dependent magnetic field on the formation of caustics. The main goal of this work is to expand our knowledge about caustics. For this purpose, we apply two models of dust distribution in the heliosphere: 1) a kinetic model based on the solving of the kinetic equation for the velocity distribution function, and 2) a fluid cold gas model based on the solving of the continuity equation in the lagrangian form. For the first time, we perform simulations for particles of different sizes and discuss the physical reasons why the density singularities appear at the caustics. We also study the effects of combined gravity and solar radiation pressure on the dust distribution near the caustics.

In this study, we examine the influence of hydrogen–proton (H–p) and hydrogen–hydrogen (H–H) elastic collisions, along with charge transfer with angular scattering, on the velocity redistribution of hydrogen atoms within a plasma layer. To achieve this, we developed a kinetic model to explore H atom behavior in a homogeneous plasma region, assessing how these effects influence the maxwellization of the H atom distribution function relative to the case where only charge exchange is considered. The homogeneous layer results provide a simplified but valuable demonstration of how elastic collisions impact H atom behavior, creating a foundation for future studies in more complex, spatially varying plasma environments. Calculations of the distribution functions at various distances reveal that combined H–p and H–H collisions lead to faster maxwellization and blur the distinction between hydrogen atoms that have undergone charge exchange and those that have not interacted with protons.

When simulating relativistic gas flows, complex flows are often formed in zones that are much smaller than the entire calculation domain. The processes that take place outside such zones may greatly affect not only the behavior but also the formation of the complex flows. The use of adaptive grids is a universal method of calculation domain discretization in calculating such multi-scale flows. An approach describing adaptive grids with a “Garden” technique is proposed. As the name suggests, this approach is to divide the calculation domain into equal grid cells (an external grid), which are also divided (internal grids), and a microgrid is the atomic structure in each of the internal grids. The microgrids consist of cells whose numbers are fixed. All necessary operations are performed with the microgrids. In this paper, we use Adaptive Mesh Refinement (AMR) with the “Garden” technique for the simulation of relativistic gas flows.

This paper presents the results of numerical modeling of laminar flows of a viscous incompressible fluid in a flat diffuser with and without vibration effects. Two methods of flow symmetrization in a flat diffuser are considered: by means of periodic vibration action at the inlet to the diffuser and on its walls. Modeling has shown that it is possible to symmetrize the flow of a viscous liquid in the diffuser by using a weak harmonic vibration action, the speed of which can be less than 0.01% of the speed of the main flow.

We discuss the results of our studies of the dynamics and structure of extended envelopes of hot Jupiters. For calculations we used 3D numerical model, based on the approximation of multicomponent magnetohydrodynamics and allowing calculate the super-Alfvén, sub-Alfvén, and trans-Alfvén regimes of the stellar wind flow around the planet. The main attention in the work is paid to aspects of further development and testing of the model. Thus, the analysis of the calculation results taking into account magnetic viscosity showed that at short times of the order of the orbital period, the effects of magnetic field diffusion are insignificant and can be excluded from the calculations of fast-flowing processes associated with the impact of coronal mass ejections on the envelope. To take into account the processes occurring in the inner parts of the atmosphere, a modification of the code for the case of a spherical mesh was carried out, and 1D aeronomic model was developed. This provides a more correct specification of the initial and boundary conditions in the upper atmosphere of hot Jupiter and opens up new possibilities for obtaining a self-consistent solution that includes both the inner atmosphere and the exoplanet’s envelope. In general, the developed tools create a good basis for interpreting observations of the planned space mission “Spektr-UF/WSO-UV” and, in the long term, will allow determining the parameters of the stellar wind and coronal mass ejections from the host stars of these exoplanets.