A series of experiments have been carried out to study shock-initiated combustion in a converging lens geometry. For heavy gas bubbles, the acoustic impedance mismatch results in a focusing of the transmitted shock wave known as the shock focusing phenomenon. The increase in temperature and pressure that result from this phenomenon are used to ignite a combustible gas mixture near the downstream pole of the bubble. The characteristics of the ignition and propagation of the reaction front are studied experimentally in conjunction with the hydrodynamic bubble morphology. The experiments cover a range of incident shock wave Mach numbers (1.35

A preliminary experimental study was made to determine the behavior of an air bubble subsequent to the impingement of a shock wave or sharp pressure front upon it. An observed feature of the motion is the formation of a liquid jet similar to those created during the detonation of a shaped explosive charge. Two types of bubbles were observed. One is a long air bubble rising in a shock tube partially filled with water. As first shown by G.I. Taylor the upper interface is nearly spherical. The other is a nearly spherical bubble. Jets are observed in both cases and therefore indicate the need to consider this phenomenon in cavitation damage and cavitation hysteresis studies. In view of the significant effects of very dilute solutions of long chain molecules on cavitation, work on a short pulse duration argon laser was done which shows promise as a means of obtaining holographic information on the dynamic behavior of these molecular groups. Operating pressure of the argon gas is found to be important for short optical pulse generation. Methods of obtaining the holograms pertinent to this application are discussed. (Author).

The main goal of this program was to establish a qualitative and quantitative connection, based on the appropriate dimensionless parameters and scaling laws, between shock-induced distortion of astrophysical plasma density clumps and their earthbound analog in a shock tube. These objectives were pursued by carrying out laboratory experiments and numerical simulations to study the evolution of two gas bubbles accelerated by planar shock waves and compare the results to available astrophysical observations. The experiments were carried out in an vertical, downward-firing shock tube, 9.2 m long, with square internal cross section (25×25 cm2). Specific goals were to quantify the effect of the shock strength (Mach number, M) and the density contrast between the bubble gas and its surroundings (usually quantified by the Atwood number, i.e. the dimensionless density difference between the two gases) upon some of the most important flow features (e.g. macroscopic properties; turbulence and mixing rates). The computational component of the work performed through this program was aimed at (a) studying the physics of multi-phase compressible flows in the context of astrophysics plasmas and (b) providing a computational connection between laboratory experiments and the astrophysical application of shock-bubble interactions. Throughout the study, we used the FLASH4.2 code to run hydrodynamical and magnetohydrodynamical simulations of shock bubble interactions on an adaptive mesh.