The detonation burning of a fuel mixture resulting from a double explosion

A study is made of the propagation of a multifront detonation burning in a fuel mixture consisting of a gaseous fuel and an oxidant with additions of combustible solid or liquid particles arising as a result of a double point explosion. In such combustible media it is possible for there to be propagation of several detonation or burning fronts following one after the other. The easily igniting gaseous fuel burns in the first detonation wave, which propagates in the gaseous mixture with particles which are heated by the products of the explosion, ignite and burn in the second detonation wave or in the flame front. Self-similar regimes of propagation of such waves in an idealized formulation were studied in [1].Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 126–131, March–April, 1985.     

Blast wave propagation in air from a gaseous charge

In the point explosion problem it is assumed that an instantaneous release of finite energy causing shock wave propagation in the ambient gas occurs at a space point. The results of the solution of the problem of such blasts are contained in [1–4]. This point model is applied for the determination of shock wave parameters when the initial pressure in a sphere of finite radius exceeds the ambient air pressure by 2–3 orders of magnitude. The possibility of such a flow simulation at a certain distance from the charge is shown in papers [4, 5] as applied to the blast of a charge of condensed explosive and in [6, 8] as applied to the expansion of a finite volume of strongly compressed hot gas. In certain practical problems the initial pressure in a volume of finite dimensions exceeds atmospheric pressure by a factor 10–15 only. Such cases arise, for example, in the detonation of gaseous fuel-air mixtures. The present paper considers the problem of shock wave propagation in air, caused by explosion of gaseous charge of spherical or cylindrical shape. A numerical solution is obtained in a range of values of the specific energy of the charge characteristic for fuel-air detonation mixtures by means of the method of characteristics without secondary shock wave separation. The influence of the initial conditions of the gas charge explosion (specific energy, nature of initiation, and others) is investigated and compared with the point case with respect to the pressure difference across the shock wave and the positive overpressure pulse.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 110–118, May–June, 1986.     

Onset of liquid-phase flow as a result of the accumulation of gaseous products

The flow of a gaseous mixture of hydrocarbons and carbon dioxide through a model reservoir with a stationary hydrocarbon liquid phase has been investigated theoretically and experimentally. The possibility of the onset of liquid-phase flow as a result of the accumulation of gaseous products is demonstrated.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 185–188, March–April, 1990.     

Self-similar electrical skin explosion of a conductor

We examine the problem of the electrical explosion of a conductor with flat boundary in a strong magnetic field. We estimate the role of heat conduction in order to determine the critical electrical fields in which fusion and vaporization of the metal take place. The characteristic features of the explosion of a layered medium are examined.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, Vol. 10, No. 3, pp. 21–26, May–June, 1969.The author wishes to thank L. M. Barkov for discussions of the questions examined above.     

Motion of gas due to a point explosion in an inhomogeneous atmosphere

The problem of a strong point explosion in an atmosphere with exponential dependence of the density on the altitude was considered in detail in the monograph [1]. As the blast wave becomes weaker, it is necessary to take into account the counterpressure and the gravitational force. Then in the central hot region of the explosion the gas-dynamic processes are intensified, and the method of calculating the flow parameters in the neighborhood of the point of energy release becomes important. The singularity at this point can be eliminated by including dissipative factors in the treatment; it is then possible to use standard difference methods in the hot central region. In the present paper, the qualitative and quantitative effects of the counterpressure and gravitation are analyzed. A model of the explosion with a simple mechanism of energy dissipation — heat transfer by radiation — is considered. The calculations of the explosion are continued until the formation of the mushroom cloud. The results are compared with the data of other authors.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zfaidkosti i Gaza, No. 6, pp. 144–151, October–December, 1981.     

Motion of a gas mixture through a porous medium with sorption

Solutions are investigated of a system of linear partial differential equations describing the motion of a gaseous (liquid) mixture through an undeformable homogeneous porous medium with sorption at interfaces between gaseous (liquid) and solid phases, the kinetics of which are described by a linear equation. If the porous medium consists of spherical granules, the problem is solved in quadratures. For the case of symmetric granules with arbitrary symmetry parameter, various approximate solutions are obtained; first and central moments are used as criteria for the accuracy of the approximations.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 95–100, September–October, 1970.     

Explosion of a body in flight

Little attention has been paid up to now in the theory of explosions to such an important and interesting problem as the explosion of a body in flight. A formulation of the problem presented by such an explosion in connection with the problem of simulating the explosion of a meteorite body flying at cosmic velocity is given in [1]. In this case the kinetic energy of the translational motion may be comparable to or even in excess of the internal energy of the explosive transformation, which will lead to a significant distortion of the flow pattern compared with the usual explosion process. An analysis of the effect of the initial velocity of particles on the course of an explosion in idealized formulations in the framework of one-dimensional flows with plane, cylindrical, and spherical waves was first made in [2–4]. The asymptotic flow properties were found in these papers. It is shown that if the internal energy E_o and the kinetic energy K_o are separated (the specification of the latter for a fixed mass is equivalent to specification of the initial momentum), some intermediate self-similar regimes corresponding to a short pulse [2] or to flows with a sink [3, 4] are observed, these becoming the solution for a strong explosion at long times [1]. The time of transition from one qualitative regime to another depends on the ratio K_o/E_o. In the present paper the next step in the investigation of the question is taken. An axisymmetric, basically realistic flow model is studied.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 126–129, September–October, 1984.     

One case of the explosion of a symmetric variable-thickness surface charge

Within the framework of the model of explosion phenomena proposed by M. A. Lavrent'ev, the plane problem of determining the shape of the excavation during the explosion of a constant-thickness surface charge is solved (when the pulse pressure is constant over the width of the charge). The problem of determining the shape of the excavation during the explosion of a surface charge whose section thickness varies linearly is considered below for the same model of explosion phenomena called solid-liquid [2]. (The problem reduces to a homogeneous linear Hilbert boundary-value problem with discontinuous coefficients. The solution is obtained in closed form, and recommendations are given for its practical realization.)Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 154–161, May–June, 1976.     

Numerical investigation of the expansion of a cloud of dispersed particles or drops under the influence of an explosion

The results are given of a numerical investigation into the expansion of clouds of fine disperse particles or drops suspended in air under the influence of a blast wave. Two possible situations are simulated: an explosion in front of a cloud and an explosion in the region of a cloud (explosion with simultaneous formation of a drop region behind the shock front). The influence that the determining parameters have on the range and extension of the expansion zone is analyzed, and the results of the numerical experiments are generalized by means of empirical dependences.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 82–90, January–February, 1982.We thank K. I. Kozorezov for drawing our attention to the subject of the investigation and A. L. Gonor for a helpful discussion.     

Container for Localization of an Explosion of a Compact High–Explosive Charge with an Inert Shell

Results of an experimental study of fragmentation effects in the explosion and the piercing power of the fragments of inert masses in the form of hemispherical aluminum and soft–steel shells enclosing the spherical charge of a high explosive under their action on flat steel, aluminum, steel–net, and claydite—concrete barriers are given. A design of the lightest spherical explosion–proof container with a load–carrying steel or glass–reinforced plastic shell protected by a splinter–proof layer capable of withstanding an explosion of a high–explosive charge (with a twofold safety factor) with an inert steel shell is proposed.     

Growth of a main crack under the influence of gas moving inside it

The motion of a gas or liquid in a growing main crack is examined in connection with the problem of the hydraulic fracture of an oil-bearing bed [1, 2] and evaluation of the quantity of gaseous products escaping from the cavity formed by the underground explosion into the atmosphere by way of the crack [3]. The studies [1, 2] formulated and solved a problem on the quasisteady propagation of an axisymmetric crack in rock under the influence of an incompressible fluid pumped into the crack. An exact solution was obtained in [4] to the problem of the hydraulic fracture of an oil-bearing bed with a constant pressure along the crack. The Biot consolidation theory was used as the basis in [5] for an examination of the growth of a disk-shaped crack associated with hydraulic fracture of a porous bed saturated with fluid. A numerical solution to a similarity problem on the motion of a compressible gas ina plane crack was obtained in [6]. Here we examine the problem of the propagation of a main crack (plane and axisymmetric) under the influence of a gasmoving away from an underground cavity.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 116–122, July–August, 1986.We thank V. M. Entova for his remarks, which helped to improve the investigation.     

Asymmetric impact of a jet with an ideal noncompressible liquid

The problem of impact of a jet belongs among classical problems. The question of asymmetric impact of a jet is of special importance in view of the development of new methods for treating metals by means of explosive energy and, in the first instance, welding by explosion [1, 2].Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 5, pp. 40–44, September–October, 1986.     

Problem concerning a plane explosion in a heterogeneous atmosphere with account taken of the post-breakthrough stage

The problem is considered concerning a plane explosion in an exponential and standard atmosphere. The heterogeneity of the medium exerts an extremely marked influence on the gas flow. As shown in [1], under the conditions of an exponential atmosphere the upper part of the shock-wave front recedes to an infinite distance, after a finite time. This phenomenon has received the name breakthrough of the atmosphere. A numerical investigation of a powerful plane explosion in an exponential atmosphere at the stage before breakthrough is contained in [2]. In [3], asymptotic boundary conditions are proposed which permit the gas flow after breakthrough to be calculated. In the present paper, a numerical solution of this problem is obtained at an interval of time which exceeds by a factor of 10–15 the time of break-through. The effect of counterpressure and gravity is studied. Some results are given for a plane explosion in a standard atmosphere.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 124–131, May–June, 1976.The authors thank L. A. Chudov for attention to the project and for useful advice.     

Particle deposition on a channel wall in a turbulent disperse flow with gradient

Kinetic ideas about the motion of a set of particles (droplets) in a turbulent gas flow with gradient are used to derive a Fokker-Planck equation for the case of sufficiently large particles (more than few microns). This equation describes the process in which they are deposited on the wall of a channel. Satisfactory agreement has been obtained between the numerical solution to this equation for the deposition rate and the experimental data published in the literature. Under the assumption that the parameters of the carrier gaseous flow vary fairly slowly, a generalized equation is derived for particle diffusion in turbulent flow. This takes into account the intensity gradient of transverse pulsations in the velocity of the carrier gaseous flow.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 57–63, July–August, 1985.     

Calculation of reflection of a blast wave by a plane

Some results are given of calculation of the reflection of a blast wave by a rigid flat surface. A model of the explosion with a simple energy dissipation mechanism is considered, radiation being taken into account in the approximation of radiative heat conduction. The pressure distribution on the surface and the flow pattern in the region of propagation of the incident and reflected shock waves are obtained.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 179–182, September–October, 1982.We thank L. A. Chudov for helpful discussions of the work.     

Oscillographic study of electrical explosion in copper and gold

An oscilloscope is used to measure electrical resistance as a function of enthalpy in copper and gold during the process of electrical explosion of wire samples. The enthalpy at the initial point of the explosion process was greater in value than at the melting point of the metal. The electrical explosion phenomenon is considered from the viewpoint of the kinetics of the liquid-metalvapor transition under impulse-heating conditions. The degeneration of the initial point of the electrical explosion for liquid-phase heating over periods less than 10^–7 sec is explained by disruption of the stability of homogeneous-vapor-nucleus formation.Translated from Zhurnal Prikladnoi Mekhaniki Tekhnicheskoi Fiziki, No. 3, pp. 54–58, May–June, 1974.     

Shock adiabats and the near zone in an explosion in a drilling mud

Shock adiabats have been determined for drilling muds of various densities, and the effects of the muds on the near zone in an explosion are examined.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 77–82, May–June, 1973.     

Thermal convection in a cylindrical enclosure with intense internal heat generation in the presence of a longitudinal magnetic field

Steady convection in a gaseous medium with intense heat generation is considered without making use of the Boussinesq approximation. The effect on convection of the thermal boundary conditions at the walls of the enclosure is investigated, together with the influence of a longitudinal magnetic field which is effective when the medium is strongly heated and becomes electrically conducting.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.3, pp. 11–18, May–June, 1992.The authors are grateful to the participants in the G. A. Lyubimov seminar for discussing their work.     

The nature of the electrical impulse in an explosion

The mechanism for the formation of an electric impulse on the explosion of ordinary explosive substances is analyzed. A double electrical layer with voltage of the order kT 0.2–0.6 V is formed in the detonation wave. When the detonation wave passes to the outer surface of the charge, electrons adhere to molecules of air and explosion products. As the charged explosion products fly apart, the distance between the positive and negative charge s increases and the voltage increases to a magnitude of the order of a kilovolt. The asymmetric separation of the charged explosion products is the cause of the impulse. Theoretical estimates are compared with experiments [1].Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, Vol. 11, No. 2, pp. 72–75, March–April, 1970.The authors are grateful to Ya. B. Zel'dovich and Yu. P. Raizer for useful discussions.     

Effect of the casing on the initial parameters of the underwater explosion of a cylindrical charge of explosive

An experimental determination was made of the initial parameters of shock waves in water with the explosion of cylindrical charges of TNT in casings. It is shown that these parameters depend mainly on the dynamic rigidity of the material and the relative weight of the shell. It is established that during the process of the expansion of the casing of the charge with an explosion in limited volumes of water there is formed a region of extremely rapid expansion, whose boundary can be identified with the boundary between the detonation products and the water after destruction of the casing, coinciding in time with the arrival of the cavitation front.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 165–168, January–February, 1973.