Flow of a gas behind a Chapman-Jouguet detonation wave in the vicinity of a line of discontinuity of a surface wave curvature

This paper discusses questions of constructing a solution of the gasdynamic equations near a line of curvature discontinuity at the surface of a detonation wave, propagating under Chapman—Jouguet conditions. It describes the construction of the solution in two cases: in a flow arising with the initiation of a detonation along a half-plane in a quiescent homogeneous combustible gas and in a flow arising with the initiation of a detonation along a half-line under these same conditions.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 120–126, January–February, 1978.     

Errors in stress measurements in soils under short-term loads

The results of experimental investigations of systemic errors in stress measurements in sandy soils by strain gauges under short-term loads produced by detonation of a plane charge are presented. The effect of rigidity of sensitive elements of the gauges and the effects of stress concentrations around the gauge body on the stress field measured are analyzed. A comparison of the experimental results with the theoretical calculations of [1, 2] is offered. It is shown that the systemic errors will not exceed ± 3–7% if certain easily achieved requirements with respect to the gauges are fulfilled. The question of evaluating systemic error in stress measurement in soils under low intensity static loads has been examined in [3–6].Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 146–154, July–August, 1972.In conclusion, the authors thank N. V. Zvolinskii and A. M. Skobeev for their valuable advice and evaluation of the study, and A. I. Kotov, V. P. Sutyrin, and L. G. Romanov for participation in the conduct of the experiments and processing of the results.     

Detonation Wave Propagation in Rotational Gas Flows

This paper studies the propagation of detonation and shock waves in vortex gas flows, in which the initial pressure, density, and velocity are generally functions of the coordinate — the distance from the symmetry axis. Rotational axisymmetric flow having a transverse velocity component in addition to a nonuniform longitudinal velocity is considered. The possibility of propagation of Chapman–Jouguet detonation waves in rotating flows is analyzed. A necessary conditions for the existence of a Chapman–Jouguet wave is obtained.     

Solving Problems of Elasticity of Conical Shells

The problem of a local action of normal pressure on a thin circular shell is solved by the method of asymptotic synthesis. A conical shell under the action of local radial loads is considered as an example.__________Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 5, pp. 150–165, September–October, 2005.     

Existence of Solutions for Steady Detonation of Gas Suspensions

The existence of solutions of the traveling–wave type is studied for a system of equations that describes a one–dimensional motion of a suspension of evaporating particles in a viscous and heat–conducting chemically reacting gas. Using topological methods, it is shown that solutions corresponding to weak, strong, and Chapman—Jouguet detonation exist under certain restrictions on energy release and mass transfer.     

Measurement of contact area, contact pressure and compaction under tires in soft soil

This paper reports about measurements of the contact area of agricultuural tires in a soil bin. Four tires of the dimensions 12.5/80-18, 13.6–28, 16.9–34 and 16.9–26 were tested on a soft sandy loam. Because the existing models for predicting the footprint are complicated, a simplified model has been established, yielding good results. Measured different contact areas of all four tires are nearly constant related to wheel load except for a small increase at higher loads. Using rated loads and applying the appropriate inflation pressure, the ground pressure of a group of similar tires in loose sandy loam is independent of the tire dimensions. Measured soil compaction under at tire a various wheel loads is compared with results obtained by a mathematical model.     

箱型结构内部爆炸破坏研究进展

结构内部爆炸破坏机理和规律是常规武器毁伤效能预测与评估、建筑物和舰船抗爆防护设计的重要支撑。基于结构内爆炸载荷、内部爆炸作用下结构塑性响应、内部爆炸作用下箱壁结构破坏模式、内部爆炸作用下多箱型结构破坏模式和分布四个方面详细论述了箱型结构内部爆炸破坏的研究现状及存在的问题,并对内部爆炸后续研究给出了建议。建议研究并建立更加复杂的结构内部爆炸载荷和破坏效应描述模型、内部爆炸作用下箱壁的动力响应机理、多箱型结构与内部爆炸波产生的耦合效应、内部爆炸作用下结构的破坏模式和破坏范围的快速准确预测方法等。     

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.     

One-dimensional diffusional model of heterogeneous (gas-film) detonation

The detonation process in a tube filled with a gaseous oxidant (oxygen) and which has a thick layer of fuel (carbon with a low vapor pressure) deposited over its entire perimeter is examined; the weight ratio of fuel to oxidant considerably exceeds the stoichiometric ratio. It is assumed that the rate of heat release is determined by the diffusional (noninstantaneous) process of mixing of the vaporizing fuel and the oxidant. An estimate is made of the effect on the detonation parameters of heterogeneity in the composition over the cross section of the tube and of friction and heat losses. Dependences of the detonation parameters (propagation velocity, pressure profile in the front, distance to the Chapman—Jouquet plane) on the thermophysical properties of the fuel and oxidant are obtained.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoe Fiziki, No. 3, pp. 86–95, May–June, 1974.     

Wave motions in viscoelastic tubes. Forced oscillations

A characteristic of small blood and lymphatic vessels is the capacity of the wall to change its rheological properties and lumen by active contraction of the annular muscle cells contained in it [1–3]. A model of flow in the vessels taking this feature into account has been proposed in [4, 5], where a linear stability analysis is also given. A consequence of wall activity is the existence of auto-oscillatory flow conditions [6–8], which have also been discovered in the numerical solutions of the corresponding problems [9, 10]. Up to the present time flows have only been studied under steady conditions at the ends of the vessel and in the environment. The wall of an actual blood vessel is subject to various actions, frequently of a periodic nature: pressure pulsations at entry and rhythmically changing external forces applied from the surrounding tissues. Data exist on the sensitivity of vessels to transient actions [11–13], in particular on the relationship of their hydraulic resistance to frequency and amplitude of the action. There has been frequent discussion of the hypothesis that bv contraction of muscles in its walls or by external compression the vessel can act as a valveless pump [14, 15]. Within the framework of the quasione-dimensional approximation given below [4] the movement of liquid along a viscoelastic tube in the presence of small amplitude periodic external actions has been studied. A general solution of the problem has been constructed and concrete examples are given illustrating the features of forced wave motions in a tube having passive and active properties.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No, 4, pp. 94–99, July–August, 1984.     

On regular reflection of detonation waves

The boundaries of regular reflection of detonation waves by a rigid wall are calculated. It is assumed that detonation is initiated at the point of reflection when a shock wave is incident on the wall at a finite angle in a gas fuel mixture, the detonation propagating instantaneously along the reflected front.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 178–180, March–April, 1983.     

Hurling of shells by hollow charges

Results of the numerical solution of the problem of one-dimensional hurling of shells by hollow explosive charges are elucidated. The results of the numerical solution are compared with asymptotic formulas. Numerous domestic and foreign papers have been devoted to the question of hurling shells by explosive charges. A numerical solution of the problem of convergence of a ring to the center under the effect of detonation products is presented in [1–3]. The problem of hurling a shell by a hollow explosive charge with an internal lining is considered in [4]; the solution of the problem of hurling a shell by a hollow explosive charge without the cavity lining is presented in [5] on the basis of the energy-balance equations; however, the complete picture of the processes occurring in the detonation products is not considered.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 161–166, May–June, 1976.     

Estimates of the motion of detonation waves in a gravitating gas

According to present ideas [1, 2], the light elements contained in the outer layers of stars may be detonated when there is gravitational collapse of the core of the star accompanied by neutrino emission that initiates the detonation. The main attention in investigations has been devoted to the physical processes associated with the thermonuclear reactions and the propagation of the radiation, less attention being paid to the gas dynamics as a whole. The present paper considers the spherically symmetric problem of the adiabatic motion of a gravitating perfect gas in the presence of a detonation wave resulting from an inhomogeneous gravitational collapse of gas at zero pressure or a loss of equilibrium. Following a method developed by Golubyatnikov [3, 4], the authors construct a system of integrodifferential inequalities that, in particular, determine the law of motion of a detonation wave through a known initial state of the gas. The corresponding self-similar problems are investigated as examples.Translated from Izvestiya Akademii nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 140–145, March–April, 1984.     

On stream inhomogeneities in a pulsed electromagnetic accelerator

In a number of papers [1–7] carried out on various pulsed electromagnetic accelerators the appearance of a lamellar structure in the stream of accelerated ionized gas occurs having an oscillation frequency of several megahertz. The majority of authors relate the development of irregularities in the stream with local peculiarities in the flow of electric currents (secondary breakdowns [6], the formation of micropinches [3–5], the motion of a current spiral [2], etc.). Notwithstanding the generality of many properties of the irregularities recorded under various conditions, no unified point of view exists as yet concerning the nature of their development.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 143–149, July–August, 1970.     

Structure of detonation waves in gas suspensions of fuel containing the oxidant

The structure of detonation waves in air suspensions of unitary fuels (fuels containing an oxidant such as gunpowder and high explosives) is investigated. In such systems, complete combustion of the particles is possible at a high mass concentration of the fuel. As a result, the structure of detonation differs from that in gas-drop [1–3] and gas [4, 5] mixtures. The shock adiabats characteristic for air suspensions [6, 7] are used to investigate the field of integral curves which describe the structure of detonation waves in disperse media. Calculated distributions of the parameters which characterize the gas and particles in the detonation front are given. The influence of the rate of combustion of the particles and the intensity of interphase friction on the structure of the detonation is investigated. Results of the calculation of the structure of relaxation shock waves in gas suspensions of the solid fuel of rockets are given in [8]. Unsteady problems of convective combustion and the transition of combustion of air suspensions into detonation are analyzed in [9, 10].Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 47–53, September–October, 1981.     

Interaction of the vortex structures formed in parallel pulsed jets

The experimental investigation of the lateral interaction of the heads of pulsed jets and primary shock waves at various nozzle spacings and pressure ratio numbers is described. The various stages of formation of a composite pulsed jet issuing from a multinozzle block are classified and the flow development mechanisms are explored. It is shown for both a block and a single nozzle the shock wave travels with almost the same velocity, whereas the jet front formed at the exit from a single nozzle moves much more slowly than the jet front formed beyond a nozzle block. Long-lived lateral bursts of gas, whose dimensions are an order greater than those of the jet bursts, are detected. Their long period of existence considerably increases the stabilization time of the steady-state structure and parameters as compared with a single pulsed jet with the same flow rate.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 153–159, November–December, 1987.     

Parameters of nonuniform shocks in aluminum

A method of recording the pressure profile and mass velocity behind the front of a two-dimensional shock excited in a flat plate by a load moving over its surface is described. Results obtained for the case of detonation of a layer of explosive on the surface of an aluminum plate are presented.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 147–152, July–August, 1971.In conclusion, the authors are grateful to E. I. Silkin, A. N. Tkachenko, and N. I. Shishkin for interest manifested in the research.     

Optimization of the action of a pulsed water cannon with powder drive

The system of equations of the internal ballistics of a pulsed water cannon with powder drive is obtained. The variational problem of determining the combustion surface of the powder charge for the purpose of obtaining the pressure pulse giving a maximum jet dynamic pressure coefficient is formulated. A numerical solution algorithm is constructed and an example of the calculations is presented.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.6, pp. 156–159, November–December, 1993.     

Similarity motions of a gas in the case of local supply of mass and energy in a fuel mixture

One-dimensional nonstationary similarity motions of a gas with exothermic reactions behind shock waves are analyzed. The thickness of the region of chemical reactions is ignored. New solutions are obtained for the problems of flows of a chemically active gas with the formation of shock and detonation waves. In particular, it is shown that in the framework of the adopted schemes of the combustion process a solution with five strong-discontinuity surfaces can be constructed. The results are given of numerical solutions for supercompression detonation and Chapman-Jouguet detonation.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 70–77, July–August, 1979.     

Wave Processes in a Protective Shield

A one-dimensional problem of the interaction between a pulsed pressure wave and a plane shield separating two media with different acoustic impedances is solved. The exact solution is derived and used for establishing the applicability criteria for different approximate solutions of the problem under consideration.__________Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, 2005, pp. 180–185.Original Russian Text Copyright © 2005 by Sozonenko.