An energetic propagating vapor explosion can occur if hot and cold liquids, such as molten metal and water, are suddenly mixed. Such explosions are a hazard in the metallurgical, pulp and paper, and nuclear industries. The nature of the interaction depends on the rate of energy release which is limited by the rate at which the hot liquid fragments break up, which in turn depends on the surrounding pressure and flow fields. For low flow rates, vapor bubble growth and collapse leads to drop breakup whereas for high flow rates, the drop is directly shattered by the relative flow. Experiments are being carried out to investigate the transition from one fragmentation mechanism to another for a molten drop in water as the ambient flow velocity is increased. Diagnostics include flash X-ray radiography, high-speed photography, and fast-response pressure instrumentation. A high-frequency induction furnace is being installed to investigate high-temperature molten metals of interest to the nuclear industry. Wave propagation in vapor explosions is being investigated with Hugoniot analysis including various nonequilibrium effects (in collaboration with Prof. S. McCahan of Univ. of Toronto). Relevant publications are 3, 4, 5, 11, 17.
Rapid Evaporation of a Superheated Liquid
Very high rates of evaporation can occur if a liquid is heated to the superheat limit (see publications 6, 7, 8) or if a volatile liquid is suddenly depressurized. The latter situation is relevant to the dynamics of an accidental BLEVE (or "boiling liquid expanding vapor explosion") associated with the failure of a vessel containing a pressure-liquefied gas. Experiments are being carried out to investigate the dynamics of the evaporation process and the subsequent pressure buildup in the case of a partially-vented vessel. Relevant publications are 9, 16.
Reactive Waves in Liquid/Gas Media
High-speed pressure waves have been observed to propagated in liquid/gas mixtures in which one or both of the components can sustain a chemical reaction. Such waves are a concern in a variety of chemical process industries. For example, so-called "bubble detonations" have been observed to propagate in a mixture consisting of combustible bubbles in an inert liquid. The objective of this experimental investigation is to determine the critical limiting conditions for the propagation of the wave and the mechanism for wave failure. Relevant publications are 13, 17, 19.
Detonation Propagation in Heterogeneous Condensed Explosives
The generation of "hot-spots" plays an important role in the propagation of a detonation wave in a heterogeneous condensed explosive. To investigate the propagation mechanism, detonation propagation in a model heterogeneous explosive consisting of a packed bed of mono-sized particles saturated with liquid sensitized nitromethane is being investigated experimentally in lab and field experiments (in collaboration with Prof. M. Brouillette of U. de Sherbrooke and Dr. J. J. Lee of Caltech). Two distinct propagation mechanisms are observed for "small" and "large" particles. In the large particle limit, the propagation of the detonation in the porous medium is tracked using the Detonation Shock Dynamics model of Bdzil and Stewart (in collaboration with Drs. T. Aslam and L. Hill of Los Alamos National Laboratory). Relevant publications are 1, 2.
Rapid Acceleration of Solid Particles
Solid particles can be rapidly accelerated to supersonic speeds with the use of condensed explosives for the generation of high-strength surface coatings. The dynamics of this process are being investigated experimentally (in collaboration with Drs. F. Zhang and S. Murray of DRES). A relevant publication is 10.
Shock Waves in Heterogeneous Media
The objective of this study is to produce a quantitative model for the propagation of shock waves in laminates consisting of rigid and compressible materials. Emphasis is placed on accurately characterizing the rate-dependent losses within the compressible layer. The model is validated with results in which the compressible material is subjected to an air blast wave. The goal is to maximize the attenuation of the peak pressure and impulse of the blast wave, with application to the protection of structures and personnel against blast waves from accidental explosions. A relevant publication is 12.
The self-propagating high-temperature synthesis (SHS) process is being used to synthesize various metal-sulfur compounds in lab and microgravity experiments (in collaboration with Prof. J. Lee and Dr. S. Goroshin). Relevant publications are 14, 18.