Thesis (M.S.)--Ohio State University. / Includes bibliographical references (leaves 111-115). Available online via OhioLINK's ETD Center

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 136-142).

No description available.

This thesis is concerned with the experimental determination of the fundamental flame characteristics in a dust-air mixture and the influence of turbulence on flame propagation. Experiments were carried out in a tube having a 0.19 meter inside diameter and a length of 0.93 meter, and 1.86 meter with both ends closed. A dispersion system was developed giving a good quality uniform dust suspension. A comparative method for the estimation of dust flame characteristics, based on well defined methane-air flame characteristics, was developed and employed to estimate the characteristics of a flame propagating in a cornstarch dust-air mixture. A systematic study of the influence of dispersion-induced turbulence on the dust flame propagation was carried out. The influence of obstacles on flame propagation also was investigated. Some mechanisms of flame propagation in a cornstarch dust-air mixture have been proposed and discussed. In the conclusion, general remarks concerning the dust flame characteristics and the influence of turbulence on flame propagation are made. The future direction of research is also indicated.

No description available.

Safety cases must be produced by offshore operators to assess the risks posed to the personnel by potential accidents. On an offshore platform two of the major hazards are fires and explosions resulting from an accidental hydrocarbon release. The overpressures generated during an explosion can threaten the integrity of the platform structure. It is therefore important to be able to estimate the overpressures generated, should an explosion occur, and to predict the frequency of such an event. A methodology has been developed to predict the frequency of explosions of different magnitudes occurring in a module on an offshore platform. This methodology combines established risk assessment techniques, such as event tree analysis and fault tree analysis, with fluid flow modelling. Assumptions have been made in the methodology to simplify the calculation procedure. These assumptions relate to the conditions under which the leak occurs, the build up of gas in air concentration and the probability calculations. Frequency predictions are required to be as accurate as possible to enable the acceptability of the risk to be determined and reduced to a level which is as low as reasonably practicable. Hence each of the assumptions within the methodology has been addressed, to determine a more complete prediction tool. Once an accurate frequency for the explosion occurring has been determined, the risk to personnel must be minimised to an acceptable yet practical level. On existing designs it is impractical to alter the layout of the platform. However the nature of the safety systems may be changed. These safety features include isolation, blowdown, mitigation and detection systems. An optimisation study presents three schemes to identify the optimum configuration of the safety systems, in terms of the overpressures generated, as a means of reducing the risk to the platform.

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

A novel approach to modelling highly compressible and reactive flows is formulated to provide high resolution closure of turbulent-scale reaction rates in the presence of very rapid transients in pressure and energy. For such flows, treatment of turbulent-micro scales are generally unattainable through traditional modelling techniques. To address this, the modelling strategy developed here is based on the Linear Eddy Model for Large Eddy Simulation (LEM-LES); a technique which has only previously been applied to weakly compressible flows. In the current formulation of the Compressible LEM-LES (CLEM-LES), special treatment of the energy balance on the model subgrid is accounted for in order for the model reaction rates to respond accordingly to strong shocks and rapid expansions, both of which may be present in reactive and supersonic flow fields. In the current study, the model implemented is verified and validated for various 1D and 2D flow configurations in a compressible Adaptive Mesh Refinement (AMR) framework. In 1D test cases, laminar and turbulent flame speeds and structure have been reproduced. Also, detonation speeds and initiation events are also captured with the model. For 2D model validation, unsteady and turbulent detonation propagation and initiation events, in a narrow channel, are simulated. Both test cases involve premixed methane-oxygen mixture at low pressures. The model is found to capture well the two-dimensional detonation cellular structure, behaviour, and initiation events that are observed in corresponding shock tube experiments. Furthermore, the effect of turbulent mixing rates is investigated though a single tuning constant. It was found that by increasing the intensity of turbulent fluctuations present, detonations exhibit larger and more irregular cell structures. Furthermore, the intensity of turbulent fluctuations is found to also have an effect on initiation events.

I have an interest in transposing elements of sound, time, and motion into other forms. The thesis exhibition, small Trinity, presents my efforts to capture the essence of an explosion as a sculpture. The resulting objects provide viewers with the chance to examine an explosion in a stilled state, but also to consider the enormous powers we humans wield. Comprising the exhibition are three series: Exploded Vases (2014-15), Cast Explosions (2015) and small Trinity (2016). In each, an experimental methodology is applied to tracing, capturing and then casting the shape of small explosions in a manner that is raw and un-manipulated. For the title series, small Trinity (2016), I set a goal of casting an explosion 1/1,000,000th of the power of the first atomic bomb, Trinity (1945). Through a series of successively larger explosions and casts, the goal was achieved and presented as a series of aluminium, concrete and resin sculptures.