Instability of the boundary layer on a curved surface

The excitation of instability of the boundary layer on a curved surface in the limit R (R is the Reynolds number) is analyzed.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 176–179, January–February, 1990.I am grateful to O. S. Ryzhov for his interest in the work.     

Initiation of detonation by a high-voltage discharge in powdered explosives with nanosize inert admixtures

It is shown that admixtures of a copper nanopowder in a high-disperse low-sensitivity explosive of the FOX-7 type sharply increase the sensitivity of the mixture to the action of a high-voltage electric discharge and facilitate detonation. The percolation model of propagation of the electric breakdown over a powdered mixture with nanosize admixtures and the model of initiation of detonation by a high-voltage discharge in the mixture of a brisant explosive with an inert admixture are developed. These models are in qualitative and quantitative agreement with experimental data.     

On the initiation of detonation in high explosives by a high-current electron beam

A critical analysis of experimental work on the initiation of high explosives (HE), high-current electron beam of nanosecond duration. It is demonstrated that there is no unambiguous evidence for the initiation of detonation in HE by the electron beams described in the reviewed works. The results of experiments on the effects of a pulsed electron beam on model paraffin samples are presented, which show that the geometric parameters of the sample and the presence of copper oxide nanopowder in it influence its resistance to the action of the beam. It is shown that the main effect on the sample is produced by cathode plasma beam and that the selection of the sample geometry and introduction of nanopowders can enhance the action of a high-current electron beam.     

Method for analyzing the gas jet impinging on a liquid surface

The impingement of a gas jet on a liquid surface in the stable-state regime is analyzed theoretically. We consider the case of the perpendicular jet action. It is found that for describing analytically the processes occurring in this case, it is necessary to employ the balance equation for forces at the interface and not the balance equation for pressures at the lowest point of cavity, which was used in most available publications. Recommendations for experimental studies of a gas jet impinging on a liquid surface are formulated. We report on the results of experiments confirming the correctness of our theoretical analysis and making it possible to determine the empirical value of the shape factor. The experiments were carried out with air and epoxy resin. The cavity formed on the liquid surface had radius R₀ = 1–8 mm and depth h = 0.2–12.5 mm.     

Numerical simulation of the formation of compact strikers from low-sphericity linings

We consider the physicomathematical formulation of the problem of explosive formation of a penetrator from a low-sphericity copper lining. Calculations are made for the formation of a penetrator for a phlegmatized hexogen charge for two models of the behavior of the lining material (copper), and the results are compared with the experimental data.     

Initiation of combustion in multilayer energetic compositions with a high-current electron beam

Experimental results on the ignition of energetic two- and three-layer potassium picrate- and lead(II, IV) oxide-based compositions with a high-current electron beam of nanosecond duration are reported. It is shown that the sustainability of explosive transformations in layered compositions depends on the boundary conditions and the additional impact of the cathode flame (high-temperature metal plasma).     

Influence of velocity nonuniformity in a medium on the penetration of cumulative jets and extended flyer plates

Obstacle materials into which plane cumulative jets with an initial impact velocity of 2.5–3.5 km/s penetrate are studied metallographically. The results suggest that penetration takes place in the nonuniform velocity field of the medium. A refined hydrodynamic model for the fast penetration of jets and flyer plates is put forward and verified experimentally.     

Oscillations of the plastic wave front under high‐rate loading

Two models of elastoplastic wave propagation in metals under uniaxial deformation are considered. The first model treats plastic deformation as being due to dislocation motion during heterogeneous formation of dislocations. The second model assumes that plastic deformation occurs by motion of dipoles of partial disclinations. It is shown that in both cases, certain conditions can give rise to damped oscillations of the plastic wave front, which were detected in shock loading experiments with flat specimens made of 28Kh3SNMFA steel.     

Incomplete active polarimetry: Measurement of the block-diagonal scattering matrix

The problem of measurement of block-diagonal scattering matrix as being part of the so-called incomplete or partial Mueller polarimetry is addressed. It has been shown that non-zero elements of the scattering matrix with block-diagonal structure can be measured using only two elliptical polarizations of input light. Optimal pairs of these polarizations are derived. Utilization of the optimal input polarizations results in halving measurement time and decreasing measurement errors by 30%.