The dynamics of the structure of an infinite vortex tube in ideal gas under explosive external energy deposition near its axis is studied. With neglect of viscosity and heat conduction, it is discovered that the tube is destroyed under arbitrarily small power of energy release and the time of vortex destruction decreases as the total power of energy release increases. The physical model of the flow explaining the revealed relationships is constructed. The analytical relations assessing the problem parameters for the practical use of explosives in destruction of large-diameter vortices are obtained. The estimates show that the proposed method can be applied in practice.

The problem of the infinite vortex tube structure dynamics in an ideal gas with an explosive external supply of energy near its axis solution is considered. It was found that, neglecting viscosity and heat conductivity, the tube collapses at an arbitrarily low power of energy release, while the decay time of the vortex decreases with increasing total power of energy release. A physical flow pattern that explains the discovered patterns is constructed. Analytical relations for the practical use of explosives in the destruction of large-diameter vortices are obtained. Estimates show that the proposed method is practically feasible.

Based on the selected options of room-and-pillar systems, there are distinguished the main criteria and technical-and- economic indices having an impact on rationality of mining systems' use when decreasing the depth of room work conductance.

The paper gives further development of the method of a plate single-sided probe, which makes it possible to reconstruct the total electron velocity distribution function in an axially symmetric nonequilibrium plasma with an arbitrary degree of anisotropy. The method is improved for plasma diagnostics without the assumption of any symmetry. The theory of the method is developed and analytical relations are obtained connecting the Legendre components of the second-order derivative of the probe current with respect to the potential of the probe and the electron distribution function. The method is experimentally tested in the plasma of a positive column of a helium glow discharge. New possibilities of the method for investigating plasma near the boundaries are demonstrated and non-traditional information is obtained on the processes of escape of charged particles from the plasma volume on the walls.

Поступилo в Редакцию 10 апреля 2017 г

We have analyzed the precision and systematic errors of the familiar method of a plane single-ended probe for measuring the anisotropic distribution functions for electrons and ions in plasma. Analytic relations that connect the plasma parameters and the required number of terms in a series are obtained under the conditions when anisotropy is due to the presence of an electric field in the plasma. It has been shown that ten terms of the series are usually sufficient to adequately describe the ion distribution function, except for the case of strong fields. For strongly anisotropic charged particle distribution functions, the spline interpolation technique for experimental data is proposed and tested, which substantially reduces the systematic error for a preset number of terms in the series. It has been shown for abundant actual plasma objects with the mirror symmetry that the number of required orientations of a plane probe for the experimental distribution function can be reduced by half compared to the most general case of the absence of any symmetry for a fixed number of terms in the Legendre series, while for the same number of orientations, the number of terms in the series, which are determined from these measurements, doubled accordingly.