Bubble detonation as a self-sustained solitary wave with energy release

Previous experiments have shown that a bubble detonation wave is a resonant or self-sustained solitary wave in a bubble medium. Bubble detonation is modeled by a solitary wave with energy release in bubbles. The equation describing a solitary wave of small amplitude is shown to be an analog of nonlinear Boussinesq equation of the fourth order. A comparison of the solution obtained with averaged experimental pressure profiles shows that the analytical solution is suitable for describing bubble detonation waves with a finite pressure amplitude. In the model proposed, the time of action of solitary-wave compression on a separate bubble is several times the bubble oscillation period. This result agrees with experimental data and confirms the presence of a collective resonant effect in a bubble medium. Satisfactory agreement is obtained between experimental and theoretical data on the pressure profile and extent and velocity of bubble detonation waves. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 6, pp. 104–111, November–December, 2007.     

The effect of liquid compressibility,heat loss,and the induction period of the chemical reaction on the structure of a bubble-detonation wave

Calculations were performed of the structure of a bubble detonation wave in a chemically reactive gas-liquid medium with bubbles arranged in layers. With the liquid compressibility taken into account, the amplitude of pressure pulsations decreases, and they move to the leading edge. It is shown that the wave profile depends weakly on the method of calculating the induction period of the reactive mixture and method of taking into account heat losses. A comparison is made of the calculated and experimental pressure profiles of the bubble-detonation wave.     

The effect of bubble size on the detonation wave characteristics

Detonation waves in various monodispersed media containing gas bubbles with a specified diameter were investigated experimentally. The investigation centered on the effect of the bubble size on the critical initiation conditions, the structure and on the properties of the detonation waves in bubbly media. Lower and upper bubble diameter limits were detected for the existence of detonation waves. The behavior characteristics of the gas bubbles of various diameters in the detonation wave are explained. M. A. Lavrent'ev Hydrodynamics Institute, Siberian Division, The Russian Academy of Sciences, 630090 Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 31, No. 5, pp. 83–91, September–October, 1995.     

Bubble detonation conditions

Initiation of bubble detonation in the system “inert liquid-explosive gas bubbles” by a detonation wave in a gas was studied experimentally. Compression-wave pressure profiles were determined as functions of the length of the initiation section and the initial pressure of the explosive gas mixture in it. It was shown that because of the effect of the explosive-gas volume between the diaphragm and the upper boundary of the bubble medium, the pressure in front of the initiating wave increased much more slowly than the initial pressure. The optimal length of the initiation section was found, and the critical (minimum) initiation pressure in it and at the shock-wave front were determined. It was found that for a fixed gas volume concentration in the bubble medium, the pressure in the initiation section increased insignificantly as the length of the section decreased. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 2, pp. 84–90, March–April, 2007.     

Bubble detonation in polydisperse media

Detonation waves in polydisperse bubble media have been studied experimentally. Data on the critical initiation conditions and on the structure and properties of detonation waves were obtained. The characteristics of detonation waves in poly- and monodisperse media were compared. The behavior of gas bubbles with various diameters in the detonation wave have been investigated. Lavrent’ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 3, pp. 114–119, May–June, 1997.     

Reflection of a bubble-detonation wave from a rigid obstacle

The process of detonation-wave reflection from a rigid obstacle in mono- and polydisperse bubble media is studied experimentally. The evolution of the reflected wave formed upon interaction of the detonation wave with the butt-end of a shock tube is traced. The structure of the detonation and reflected waves is studied and the wave pressures are measured at various parameters of the bubble media. The damping constants of the reflected waves are determined. In addition, the velocities of the detonation and reflected waves are measured. The effect of the gas-bubble size on the characteristics of these waves is investigated. The energy-dissipation mechanisms in the detonation and reflected waves in the bubble media are analyzed qualitatively. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 3, pp. 107–113, May–June, 2000. This work was supported by the Russian Foundation for Fundamental Research (Grant No. 98-03-32325).     

Transformation of shock waves at the interface of bubble media

The transition of shock waves from a bubble medium into a liquid or into another bubble medium with different properties is considered experimentally. Data on the structure, velocity, and pressure in the shock wave incident onto the interface, transmitted wave, and reflected wave are obtained. Experimental results are compared with numerical data. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 2, pp. 97–104, March–April, 2006.     

Steady Detonation in a Bubbly Medium

It is shown that the Iordanskii–Kogarko model contains a steady-state solution for a detonation wave in chemically active bubbly media under the following minimum requirements to the model: compressibility of the liquid and allowance for acoustic losses. The rule for choosing the velocity is formulated. The wave structure of the reaction zone and the velocity of steady bubble detonation are calculated. Key words: detonation, bubbly liquid, reacting gas bubbles, acoustic losses, soliton, solitary wave.     

Mathematical model of continuous detonation in an annular combustor with a supersonic flow velocity

A two-dimensional unsteady mathematical model of a continuous spinning detonation wave in a supersonic incoming flow in an annular combustor is formulated. The wave dynamics in a combustor filled by a gaseous hydrogen-oxygen mixture is studied. The possibility of continuous spin detonation with a supersonic flow velocity at the diffuser entrance is demonstrated numerically for the first time; the structure of transverse detonation waves and the range of their existence depending on the Mach number are studied. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 6, pp. 83–91, November–December, 2008.     

Low-velocity detonation limits of gaseous mixtures

Low-velocity detonation regimes in acetylene-oxygen mixtures are studied experimentally. Data are obtained on the kinematics of detonation waves and on the boundaries of the high-velocity, galloping, and low-velocity detonation regions. In lean mixtures, the lower pressure limit for the detonation regimes in narrow channels is found to be an order of magnitude lower than assumed previously under the assumption that the limiting detonation is always spin detonation. The major structural characteristics of low-velocity detonations are calculated. The boundary between low-velocity and galloping detonation is found to correspond almost exactly to equality between the induction time in a particle and the time for it to move from shock wave to flame. Nearly harmonic oscillations of the flame are observed with periods that are related to the longitudinal size of low-velocity detonation waves. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 3, pp. 89–96, May–June 1999.     

A unified theoretical model for breakup of bubbles and droplets in turbulent flows

Pressure has a significant effect on bubble breakup, and bubbles and droplets have very different breakup behaviors. This work aimed to propose a unified breakup model for both bubbles and droplets including the effect of pressure. A mechanism analysis was made on the internal flow through the bubble/droplet neck in the breakup process, and a mathematical model was obtained based on the Young–Laplace and Bernoulli equations. The internal flow behavior strongly depended on the pressure or gas density, and based on this mechanism, a unified breakup model was proposed for both bubbles and droplets. For the first time, this unified breakup model gave good predictions of both the effect of pressure or gas density on the bubble breakup rate and the different daughter size distributions of bubbles and droplets. The effect of the mother bubble/droplet diameter, turbulent energy dissipation rate and surface tension on the breakup rate, and daughter bubble/droplet size distribution was discussed. This bubble breakup model can be further used in a population balance model (PBM) to study the effect of pressure on the bubble size distribution and in a computational fluid dynamics‐population balance model (CFD‐PBM) coupled model to study the hydrodynamic behaviors of a bubble column at elevated pressures. © 2014 American Institute of Chemical Engineers AIChE J, 61: 1391–1403, 2015     

Continuous spin detonation of hydrogen-oxygen mixtures. 1. Annular cylindrical combustors

A comprehensive numerical and experimental study of continuous spin detonation of a hydrogen-oxygen mixture in annular combustors with the components supplied through injectors is performed. In an annular combustor 4 cm in diameter, burning of a hydrogen-oxygen gas mixture in the regime of continuous spin detonation is obtained. The flow structure is considered for varied flow rates of the components of the mixture and the combustor length and shape. The dynamics of the transverse detonation wave is numerically studied in a two-dimensional unsteady statement of the problem with the geometric parameters of the combustors consistent with experimental ones. A comparison with experiments reveals reasonable agreement in terms of the detonation velocity and pressure in the combustor. The calculated size and shape of detonation fronts are substantially different from the experimental data. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 2, pp. 32–45, March–April, 2008.     

Diffraction estimate of the critical energy for initiation of gaseous detonation

A criterion for the excitation of detonation is proposed: the critical initiation energy equals the work performed by the expanding detonation products along a path length equal to the longitudinal dimension of a cell. The initial radius of the layer is chosen to be equal to the radius of the detonation wave diffracted at 90° edge at the time the axial rarefaction wave converges on the axis of the gaseous charge. Formulas are obtained for estimating the critical energy for initiation of plane, cylindrical, and spherical detonation waves. The calculated values are in good agreement with experiment. Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 4, pp. 72–76, July–August, 1998.     

Detonation of a Column of a Chemically Active Bubbly Medium in a Liquid

The problem of a detonation wave propagating in a cylindrical column of a chemically active bubbly medium screened by a liquid from the tube walls is formulated and numerically solved within the framework of the Iordanskii–Kogarko two-phase model with allowance for energy dissipation due to acoustic radiation of bubbles. The wave structure of the reaction zone and the detonation velocity of the bubbly medium column are calculated. It is found that the self-sustaining wave can propagate with a velocity greater than the velocity of one-dimensional bubble detonation by a factor of 1.5–2.5.     

Detonation waves in polydisperse bubble media

Detonation waves in polydisperse and monodisperse bubble media are studied experimentally. The data on the critical initiation conditions and the structure and properties of detonation waves are obtained. Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 6, pp. 71–76, November–December 1998.     

Effect of the degree of dispersion on the detonation wave structure in pressed TNETB

A VISAR interferometer was used to study the reaction zone in steady-state detonation waves in pressed TNETB at different initial densities (1.23–1.71 g/cm³) and degrees of dispersion (5 and 80 μm) of the initial powdered high explosive (HE). The initial density range in which a pressure rise was observed instead of the theoretically predicted chemical spike is shown to depend on the degree of dispersion of the HE. The unusual change in the parameters in the reaction zone is explained by the heterogeneous structure of pressed HEs, whose decomposition has a local nature and proceeds partially at the compression wave front. A technique for recording wave profiles using LiF windows was developed, which confirmed that all qualitative features observed when using aluminum foils ≈200 μm thick and a water window reliably reflect the detonation wave structure. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 5, pp. 90–95, September–October, 2007.     

Critical energy of bubble detonation wave initiation by a wire explosion

Initiation of bubble detonation by a short shock wave generated by exploding a wire located in a chemically active bubbled medium is studied experimentally. Critical energies of detonation initiation are determined for different volume fractions of bubbles. It is demonstrated that this method of initiation transforms the compression wave to a detonation wave at a length of ≈0.3 m. In the case of a wire explosion in a gas-liquid medium, the critical energy of bubble detonation initiation can be reduced by more than two orders of magnitude, as compared with initiation by a gas detonation wave.     

基于气泡群相间作用力模型的加压鼓泡塔流体力学模拟

目前,多数文献报道了冷态加压湍动鼓泡塔内流动特征,并且通过实验数据回归相关经验关联式。然而,此类关联式适用范围有限,难以直接外推到工业鼓泡塔反应器条件。因此,在FLUENT平台上建立了基于气泡群相间作用力的、动态二维加压鼓泡塔计算流体力学模型。通过数值模拟考察了操作压力为0.5~2.0 MPa,表观气速为0.20~0.31 m·s^-1,内径0.3 m鼓泡塔内流场特性参数分布,并且与冷态实验数据进行比较。结果表明,采用修正后的气泡群曳力模型、径向力平衡模型以及壁面润滑力模型描述气泡群相间作用力,能够较为准确地反映平均气含率和气含率径向分布随操作压力和表观气速变化的规律。     

Mathematical modeling of a rotating detonation wave in a hydrogen-oxygen mixture

A two-dimensional unsteady mathematical model of spin detonation in an annular cylindrical ramjet-type combustor is formulated. The wave dynamics in the combustor filled by a hydrogen-oxygen mixture is studied numerically. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 4, pp. 90–101, July–August, 2007.     

Effect of Al/O Ratio on the Detonation Performance and Underwater Explosion of HMX‐based Aluminized Explosives

The performance of detonation and underwater explosion (UNDEX) of a six‐formula HMX‐based aluminized explosive was examined by detonation and UNDEX experiments. The detonation pressures, detonation velocities, and detonation heat of HMX‐based aluminized explosive were measured. The reliability between the experimental results and those calculated by an empirical formula and the KHT code was verfied. UNDEX experiments were carried out on the propagation of a shock wave and a bubble pulse of a 1 kg cylindrical HMX‐based aluminized explosive underwater at a depth of 4.7 m. Based on the experimental results of the shock wave, the coefficients of similarity law equation for the peak pressure and attenuation time constant of shock wave were in acceptable agreement. The bubble motion during UNDEX was simulated using MSC.DYTRAN software, and the radius time curves of bubbles were determined. The effect of the aluminum/oxygen ratio on the performance of the detonation and UNDEX for an HMX‐based aluminized explosive was discussed.