Interaction of a heterogeneous detonation wave propagating in a cellular regime with a cloud of inert particles

Interaction of heterogeneous cellular detonation propagating in a plane channel with a cloud of inert particles is numerically studied. It is demonstrated that the presence of inert particles alters the detonation wave structure and its velocity.     

Reflection of a shock wave in a dusty cloud

The problem of shock-wave passage along a cloud of particles adjacent to a solid surface is studied numerically and analytically. The wave pattern of the flow near the shock wave reflected from this surface is analyzed within the framework of the equilibrium approximation of mechanics of heterogeneous media. The conditions of the transition from regular to irregular reflection from the substrate of the refracted shock wave inside the cloud are obtained analytically. The results of numerical simulations of a nonequilibrium flow in the two-velocity two-temperature approximation are compared with data obtained in the equilibrium approximation. Nonequilibrium and equilibrium flows are found to become more similar as the particle size decreases. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 1, pp. 121–131, January–February, 2007.     

Drag of nonspherical particles in a flow behind a shock wave

The early stage of velocity relaxation of nonspherical particles in a flow behind an incident shock wave is considered by the method of multiframe shadowgraphy. A procedure of processing the data on the motion of a free body for determining its acceleration is proposed; in combination with the diagnostic method used, the procedure forms something like a noncontact aerodynamic balance. Novel data on the drag of bodies of irregular shape in a flow behind a shock wave with Mach numbers of 0.5–1.5 and Reynolds numbers of 10⁵ typical of dust explosions are obtained. It is found that the values of drag of a nonspherical bluff body and a sphere under these conditions are similar and exceed the drag of a sphere in a steady flow by a factor of 2 to 3.Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 1, pp. 81–88, January–February, 2005.     

Interaction of a normally incident shock wave with a porous material layer on a solid wall

Interaction of an incident shock wave with a layer of a porous material located near a solid wall is studied with the use of two mathematical models. The layer is modeled by a mixture of solid and gaseous phases. The mathematical models used are the equations of mechanics of equilibrium heterogeneous media with allowance for the gas pressure only and the model of two compressible media with identical partial pressures of the components. Verification of the approaches used is performed by comparisons of numerical results with experimental data.     

Interaction of a shock pulse with a contact discontinuity

Passing of a triangular moderate-intensity pulse through a constant discontinuity is considered. Decay of the shock wave that passed into the second gas is analyzed. Damping of the detonation wave after burnout of the combustible mixture is discussed. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 4, pp. 102–107, July–August, 2007.     

Reflection of a shock wave from a rigid wall in a mixture of a liquid metal and solid particles

The problem of reflection of shock waves and expansion waves from a rigid wall in a mixture of liquid iron and small molybdenum crystals is considered. The study is performed within the framework of equilibrium and nonequilibrium approximations of mechanics of heterogeneous media with different pressures of the components. The mathematical model is verified by fitting the dependence of the equilibrium-frozen velocity of sound on the initial pressure in the mixture with available experimental data. In the equilibrium approach, the dependence of the type of the reflected wave on the type of the incident wave is determined. Direct numerical calculations within the framework of the nonequilibrium model of mechanics of heterogeneous media confirmed the validity of the reflection chart obtained. The possibility of significant compacting of molybdenum particles in reflected waves is revealed. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 4, pp. 97–107, July–August, 2000. This work was performed within the framework of the Integration Project No. 97-24 of the Siberian Division of the Russian Academy of Sciences.     

Effect of collision dynamics of particles on the processes of shock wave dispersion

Based on numerical simulations of two-dimensional unsteady flows of gas suspensions, the contribution of particle collisions to dispersion processes during interaction of shock waves with dense dust layers is analyzed. A model of collision dynamics of the two-phase medium based on molecular-kinetic approaches is used. The model is tested by using a problem of a shock wave passing along a dense layer of particles; the model predictions are found to agree well with available experimental data. The problem of interaction of a blast wave with a dense layer on a flat surface is also considered. A comparative analysis of various mechanisms acting on particles and the influence of the initial parameters of the layer on the particle lifting dynamics is performed. A weak effect of the Saffman force and inhomogeneity of the layer surface (waviness) and a significant effect of the Magnus force on dispersion of the layer directly behind the shock wave are demonstrated. In some cases, the contribution of the particle collision dynamics is found to be comparable with the Magnus force effect. Dust lifting due to the development of the Kelvin–Helmholtz instability occurs at late stages of the process.     

Interaction of weak shock waves with a layer of a powdered medium

Results of analytical and numerical studies of the interaction of linear and weakly nonlinear air shock waves with an infinite layer of a powdered medium and with a finite-thickness layer are presented. Approximate analytical expressions for phase-pressure distributions in the powdered medium are obtained. It is found that the gas pressure at the “gas-powder” interface is continuous for linear waves and experiences a sudden change for nonlinear waves. The dependences of phase pressures on a shielded solid wall obtained by solving a general nonlinear system of equations of motion of a powdered medium and an approximate analytical solution of linear equations are compared. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 3, pp. 131–140, March–April, 2000.     

Detonation wave structure in a vacuum with unitary fuel particles

The structure of steady state detonation in a vacuum with unitary fuel particles is studied. It is shown that the detonation structure lacks a shock wave frozen in the gas, and that the detonation wave zone consists of a contact discontinuity with jump in gas temperature and continuous pressure, a compression relaxation wave with contact discontinuity in the ignition plane and adjacent combustion zone. Parameters of the two-phase flow in the reaction zone are calculated.Novosibirsk. Translated from Fizika goreniya i Vzryva, Vol. 27, No. 6, pp. 109–115, November–December, 1991.     

Attenuation of a shock wave in organoplastic

The attenuation of a plane shock wave in organoplastic was experimentally and numerically investigated during its interaction with an overtaking rarefaction wave. Measurements were carried out with manganin gauges, An earlier formulation model of the dynamic deformation of composites was used in calculations. A comparison of calcualted and experimental data has shown their good agreement.Lavrent'ev Institute of Hydrodynamics, Russian Academy of Sciences, Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol 31, No. 2, pp. 125–130, March–April, 1995.     

Ignition of a heterogeneous cloud of particles by a radiant flux

The paper deals with the ignition of a heterogeneous cloud of a gas suspension of reacting particles by an external radiant flux. Depending on the parameters of the problem, the ignition and bulk inflammation regimes are distinguished. An increase in the external-flux intensity and dispersed-phase particle size favors transition of bulk inflammation to ignition. The inflammation coordinate is independent of the mass concentration of the dispersed phase. Allowance for heat radiation by particles leads to an insignificant shift of the inflammation coordinate inside the cloud and to an increase in the induction period of inflammation.Translated from Fizika Goreniya i Vzryva, Vol. 32, No. 4, pp. 19–24, July–August, 1996.     

Numerical study of dispersion of a rough dense layer of particles under the action of an expanding shock wave

Interaction of an expanding shock wave with a layer of particles having a rough surface is considered within the framework of the collisional model of a gas suspension. The influence of roughness on the shape of the contact boundaries in the gas phase and on the boundaries of the cloud of particles is analyzed. The development of the Richtmyer–Meshkov instability is demonstrated. Factors of particle dispersion are determined. Instability evolution is found to increase the amplitude of surface disturbances, and the development of collision dynamics favors smearing of finger-type structures. If the particle motion is essentially random, the pattern of cloud spreading is similar to that observed in experiments.     

Ignition of petn particles by a gas-detonation wave

Ignition ofPETN particles by a gas-detonation wave in a gas suspension has been studied experimentally. The critical pressure at which the total rate ofPETN decomposition increases sharply has been found using a method of multiwave pyrometry with variation in the pressure of the initial gas mixture from 0.1 to 0.4MPa. It is shown that this can occur owing to a large increase in thePETN surface area because of the fragmentation of melting particles in a high-enthalpy flow of gas. Lavrent’ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 2, pp. 133–138, March–April, 1997.