Hypervelocity flows with thermal and chemical nonequilibrium with Profs S. Girimaji, R. Bowersox, and S. North (TAMU), R. Lucht (Purdue) and G. Elliott (UIUC). AFOSR MURI Technical feasibility of hypersonic flight depends to an significant degree on our ability to understand transition and turbulence in hypersonic flows with chemical and thermal nonequilibrium. Experimental investigations are being carried out in a high stagnation enthalpy expansion tube. The goals of this work include the development of molecular-filter based laser diagnostic techniques and laser induced fluorescence techniques to measure velocity, density, and temperature for fundamental studies in several reacting, turbulent, high-speed flow fields. Shock-induced pore collapse as a mechanism for detonation initiation in energetic materials DOE Center for Simulation of Advanced Rockets The formation of local regions of energy release or hot spots is critical to detonation initiation in heterogeneous energetic materials. Aging, thermal damage, and mechanical damage potentially change the material structure and therefore the detonation characteristics, affecting both ignition performance and safe handling. The problem is extremely complex involving a very large spectrum of length and time scales, thermal and mechanical fluid-structure coupling, and multi-species chemical kinetics. Dynamic, spatially-resolved experimental measurements are being made in a model problem to i) identify the dominant mechanisms occurring during asymmetric pore collapse (jetting, hydrodynamic impact etc.) and assess their role in detonation initiation and ii) provide data for comparison and validation of numerical codes developed by the Illinois ASCI Center. Investigation of Diffusion, Instability, and Mixing in Detonation Shear Layers with Drs. T.L Jackson (CSAR), L. Massa (CSAR) In detonation waves, the reaction rate behind the leading shock is extremely sensitive to perturbations in the post-shock temperature. As a result, self-sustaining gaseous detonations exhibit a complex, unstable and unsteady structure. Recent experiments have shown unusual features in high activation energy chemical systems including triple point shear layer instability between gas of different degree of reaction and the formation of intriguing, intensely luminescent regions or hotspots in the vicinity of the triple point shear layers. Simulations are being performed to examine shear layer stability and structure at the conditions of detonation triple points. Wave Propagation through mm-scale channels Development of integrated miniaturized fluidic systems will depend on optimizing the interaction of multiple components such as valves, injectors, pumps, and channels. Optimizing both devices that operate on steady-state assumptions and devices where unsteadiness is cultivated, for example mixers or pulsed delivery systems, will require an understanding of the transient fluid mechanics. A fundamental experimental investigation of wave propagation in a channel is being carried out. In an experiment in which a weak shock wave is introduced into a mm-scale channel, significant late-time pressure rises are observed at length over diameter ratios of 3000. We investigate the possibility that such pulsed devices could be used for precise delivery of samples, avoiding the dramatic pressure drops experienced in steady-state fluidic systems. Detonation propagation and failure in narrow channels with M. Short (TAM) This is an integrated experimental and numerical investigation into the failure mechanism of self-sustaining gaseous detonations introduced into a narrow channel. Existing empirical scalings predict detonation failure (decoupling) when the channel dimension is on the order of the characteristic length scale of the detonation instability, the cell width. We investigate whether given the large surface area to volume ratios in these mm-scale channels, viscous effects can augment the failure mechanism. Applications of this work include the design of improved detonation arrestors, and prevention of detonation in cracks in solid propellants and energetic materials.