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The phenomenon of photochemical initiation of gaseous detonation waves has been experimentally and theoretically investigated. In the experiments, the flash photolysis technique has been employed and the initiation phenomenon has been directly observed through schlieren photography, while in the theoretical phase, the non-steady reacting flow-field of a photochemically ignited gas mixture has been numerically analyzed. The results conclusively show that the direct detonation initiation can be generated by an intense ultra-violet radiation, and it is shown that the initiation mechanism is mainly attributed to the rapid shock wave amplification occurring in a non-uniformly photo-dissociating gas mixture. It was found that the shock wave amplification is due to the coherent energy release from the non-uniformly reacting gas mixture to the shock wave and that the induction time gradient field generated by the flash photolysis plays an important role in the shock amplification process. / Further insight into the fundamental mechanisms of shock wave amplification has been obtained by considering a relatively simple theoretical model. This model illustrates the important role of the induction time gradient field in the shock wave amplification. Finally the concept of shock wave amplification in an induction time gradient field has been further extended to include the problem of transition to detonation in a non-uniformly preheated mixture.

Thesis (M.S.)--University of Texas at El Paso, 2007. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (M.S.)--University of Wisconsin--Madison, 1967. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2006. / Sathya Hanagud, Committee Member ; Min Zhou, Committee Chair ; David McDowell, Committee Member ; Jianmin Qu, Committee Member ; Naresh Thadhani, Committee Member ; Karl Jacob, Committee Member. Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 32-34). Also available via the Internet.

A time-resolved holographic interferometer specially suited for high-speed visualization of the gas flow in shock tube experiments has been developed. Holographic interferometry, which is based on the recording of two coincident holograms at different times so that one of them acts as a reference field, can accurately reveal the density distribution in a gas. The device described here fills the need for a practical method to record short sequences of holographic interferograms documenting the evolution of shock wave reflections that are not self-similar in time. Multiple hologram recording was implemented on an existing holographic interferometric system through the technique of spatial frequency multiplexing, in which the holograms are overlaid but the reference beam is angled differently for each exposure. Because the object beam is not involved in the multiplexing process, the imaging optics of the original system could be left unmodified. The upgrade only entailed the introduction of an angular sweeping system in the reference beam path. The beam multiplexing assembly was initially based on a spinning mirror design, which produced fairly satisfactory recordings of non-interferometric holographic sequences but was incapable of accurately overlaying a second set of exposures establishing the reference field for each image. The mechanical sweeping system had other drawbacks as well, among them the tendency to create extraneous fringes in the holographic images because of the unavoidable angular motion of the reference beam over the duration of a laser pulse. A solid-state multiplexing system was then devised in which the reference beam was split into several branches, each aimed at the film from a different direction and individually shuttered by a ferroelectric liquid crystal light valve. Beam sweeping was achieved by opening the shutters in sequence as the laser was pulsed, but it was also possible to record the reference exposure on all images simultaneously with a single laser pulse by having all shutters open at the same time. A prototype three-image system was constructed and successfully tested by recording interferometric sequences of a shock wave reflecting off a model at framing intervals down to 100 μs. / Graduate

Cavitation is the formation of vapour filled bubbles in a liquid. They can be generated either by the reduction of the ambient water pressure at constant temperature or by a temperature increase at constant pressure. In the results of the experiments presented in this work a range of different diameter cavitation bubbles were generated by focusing pulses of near IR radiation (le = 1064 nm) from a Q-switched Nd:YAG laser of varying energy in a small water tank. Single exposure high speed shadow photography and Schlieren techniques are used to visualise the oscillating motion of the cavitation bubbles with high temporal and spatial resolution. The optical analysis of the cavitation bubble in free water shows a smooth symmetrical oscillating motion during the first cycle. When the bubble is collapsing near a solid boundary the motion becomes asymmetrical. The Schlieren images in combination with matching plots of a thin film polyvinylidene fluoride (PVDF) pressure transducer confirm the formation of a liquid jet as well as different shock wave emissions for certain bubble to boundary parameters. They also indicate the importance of the resulting fluid flow to stresses induced in the solid boundary. In an attempt to visualise the fluid flow field around an oscillating cavitation bubble the IR laser radiation is focused in a solution of copper sulphate (CUS04) for contrast enhancement. High speed photography in combination with an accurately positioned Schlieren knife edge displays the heated path of the laser beam and the different shapes of the cavitation bubble. For the case of a bubble in free space the marked laser path indicates radial fluid flow only. For a bubble in front of a solid boundary the marked laser path clearly shows the motion of the fluid into the toroidal shaped bubble during the collapse process. For this case the marked paths are similar to numerically calculated streamline plots. In contrast to the solid boundary a flexible boundary was also used. The interaction of the cavitation bubble with the flexible boundary visualises partially the movement of the water but is found to still destroy some of the symmetry of the bubble.