Interactions of shock tube exhaust flows with laminar and turbulent flames

The interactions of flow features emitting from open-ended shock tubes with free-standing propane flames have been investigated using high-speed schlieren imaging and high-frequency pressure measurements, with additional data from validated numerical modeling. Both compressed air-driven interactions with non-pre-mixed laminar diffusion flames (small-scale) and explosively-driven interactions with turbulent non-pre-mixed turbulent flames (large-scale) were tested for various flame locations and shock tube stagnation pressures (and therefore Mach numbers). In the small-scale tests it was observed that the flames were not significantly influenced by the passage of either the initial shock if placed close to the tube exit, or the weaker pressure waves downstream if the flame was placed further away. Four types of interaction were classified, three of which led to permanent extinguishment of the flames. The most effective mechanism of extinguishment for a flame in-line with the exhaust was the axial exhaust jet of expanding air, which served to push the flame off the fuel source either at close range (Type I) or more slowly at a distance (Type II), after which rapid cessation of combustion occurred. With the flame positioned to one side of the path of the jet, strong loop vortices achieved a similar overall outcome of extinguishment, albeit with very different flame behavior in reaction to the strong turbulence and vorticity induced by the passing flow (Type III). In all cases bar one, the disruption to the fire triangle caused by these flow effects was sufficient to extinguish – rapidly and permanently – the flame. However, at a sufficient lateral offset of the flame from the shock tube exit, the strength of rotating flow being entrained into the diffusing vortex ring was not sufficient to remove and disperse the heat from the extinguished flame (Type IV), such that re-ignition could occur. By contrast, in the large-scale tests with a significantly different shock pressure profile and a flame approximately 1 order of magnitude greater, extinguishment in all cases for all shock strengths and locations was achieved by the shock itself (accelerating combustion) and the following “blast wind” impulsively moving the flame off the fuel source, with the vortices having negligible effect at the given testing locations (Type V)

CASTRO: A New Compressible Astrophysical Solver. II. Gray Radiation Hydrodynamics

We describe the development of a flux-limited gray radiation solver for the compressible astrophysics code, CASTRO. CASTRO uses an Eulerian grid with block-structured adaptive mesh refinement based on a nested hierarchy of logically-rectangular variable-sized grids with simultaneous refinement in both space and time. The gray radiation solver is based on a mixed-frame formulation of radiation hydrodynamics. In our approach, the system is split into two parts, one part that couples the radiation and fluid in a hyperbolic subsystem, and another parabolic part that evolves radiation diffusion and source-sink terms. The hyperbolic subsystem is solved explicitly with a high-order Godunov scheme, whereas the parabolic part is solved implicitly with a first-order backward Euler method.Comment: accepted for publication in ApJS, high-resolution version available at https://ccse.lbl.gov/Publications/wqzhang/castro2.pd

A spectroscopic study of the structure of amorphous hydrogenated carbon

A range of amorphous hydrogenated carbon (a-C:H) samples have been studied using inelastic neutron spectroscopy (INS) and Fourier transform infrared (FTIR) spectroscopy. Using these complementary techniques, the bonding environments of both carbon and hydrogen can be probed in some detail, with the INS data providing not only qualitative but also quantitative information. By comparing the data from each of the samples we have been able to examine the effects of different deposition conditions, i.e. precursor gas, deposition energy and deposition method, on the atomic-scale structure of a-C:H

SOSORT 2012 consensus paper: reducing x-ray exposure in pediatric patients with scoliosis

This 2012 Consensus paper reviews the literature on side effects of x-ray exposure in the pediatric population as it relates to scoliosis evaluation and treatment. Alternative methods of spinal assessment and imaging are reviewed, and strategies for reducing the number of radiographs are developed. Using the Delphi technique, SOSORT members developed consensus statements that describe how often radiographs should be taken in each of the pediatric and adolescent sub-populations

Epson; 24- Pin Dot Matrix Printer LO- 2180

218 Ha