Experimental study of the interaction between aluminum and hydrogen fluoride in biocidal explosions

The research presented in this thesis was performed in order to develop a technique for quantitatively measuring the temperature and concentration of hydrogen fluoride (HF) in complex, turbulent flows. These diagnostics were used to investigate the potential suppression of the biocidal species due to aluminum interaction in situ. In the field of counter chemical and biological warfare, explosives are used to evolve spore-killing, and neutralizing agents. Current efforts involve collaboration between experimental and computational laboratories to develop thermochemical models for the biocidal environment. Experiments were conducted to make time resolved, optical measurements that assess the degree of chemical non-equilibrium in these events. From the data collected, the amount of HF generated and rate of equilibration in the biocidal environment was able to be determined. Two different types of experiments were conducted. The initial set of experiments was designed to closely replicate the detonation of a counter weapon of mass destruction (C-WMD) armament. These tests involved the use of high explosives coupled to solid state halogen fuels. The second thrust area was to create an explosion that replicated the kinetics of the post C-WMD detonation, but simplified the environment to allow higher quality measurements. The simplified explosions used gas phase halogen fuel (1,1-difluoroethane) diffused into a propane/air explosion with pneumatically injected powdered particulates. The results showed that neither the presence of aluminum, nor alumina, suppressed the HF population in the first second of the explosion. The data suggested that if the injected aluminum ignites, it preserves higher concentrations at lower temperatures

Diode laser gas sensing for high-speed temperature and speciation measurements inside explosive fireballs

There is a need for fundamental science to defeat weapons of mass destruction. Prompt bioagent defeat strategies invoke energetic materials to generate spore killing temperatures and halogen compounds. Developing predictive models for the bioneutralization efficiency of materials requires accurate experimental data to underpin the computational efforts. Certain thermodynamic parameters such as pressure are easily obtained in explosively driven flows. The temperature and chemistry of the interior of post-detonation fireballs is largely unmeasured at the current time. The present work was carried out in order to develop, demonstrate, and transfer technologies for making cost effective, high-speed, quantitative measurements of temperature and chemical speciation in near-field, post-detonation fireballs. This document presents the details of a hardened gauge that enables the fielding of a wide variety of proven tunable diode laser absorption techniques in explosive applications. In addition, details of the theory, application, and data analytics for the relevant spectroscopic measurements are also addressed. The developed hardware and technique were used to measure temperature at 30 kHz in chambered explosive fireballs by sweeping a tunable diode laser over a water vapor absorption band in the near infrared spectrum. Additional efforts were made to characterize the multiphase temperature of explosive fireballs. In addition to measuring temperature, a second tunable diode laser diagnostic was interfaced with the probe to measure atomic iodine in explosive fireballs as it is a halogen useful in agent defeat applications. Test data presented in this document were collected at a variety of scales ranging from milligrams of spark ignited thermites in a 2-liter chamber, to 10s of grams of aluminized, plastic explosives in an 1800-liter chamber. All data validate the ability of the combined probe and data analytics to survive the implicitly destructive intensity of explosive detonation and make high-speed optical measurements of temperature and atomic iodine concentration inside explosive fireballs

Turbulence and aeration in hydraulic jumps: free-surface fluctuation and integral turbulent scale measurements

In an open channel, a change from a supercritical to subcritical flow is a strong dissipative process called a hydraulic jump. Herein some new measurements of free-surface fluctuations of the impingement perimeter and integral turbulent time and length scales in the roller are presented with a focus on turbulence in hydraulic jumps with a marked roller. The observations highlighted the fluctuating nature of the impingement perimeter in terms of both longitudinal and transverse locations. The results showed further the close link between the production and detachment of large eddies in jump shear layer, and the longitudinal fluctuations of the jump toe. They highlighted the importance of the impingement perimeter as the origin of the developing shear layer and a source of vorticity. The air–water flow measurements emphasised the intense flow aeration. The turbulent velocity distributions presented a shape similar to a wall jet solution with a marked shear layer downstream of the impingement point. The integral turbulent length scale distributions exhibited a monotonic increase with increasing vertical elevation within 0.2 < Lz/d1 < 0.8 in the shear layer, where Lz is the integral turbulent length scale and d1 the inflow depth, while the integral turbulent time scales were about two orders of magnitude smaller than the period of impingement position longitudinal oscillations

Physical modeling of unsteady turbulence in breaking tidal bores

A tidal bore is an unsteady flow motion generated by the rapid water level rise at the river mouth during the early flood tide under macrotidal and appropriate bathymetric conditions. This paper presents a study that physically investigates the turbulent properties of tidal bores. Results from some experimental measurements of free-surface fluctuations and turbulent velocities conducted on smooth and rough beds are reported. The free-surface measurements were conducted with Froude numbers of 1-1.7. Both undular and breaking bores were observed. Using an ensemble-averaging technique, the free-surface fluctuations of breaking tidal bores are characterized. Immediately before the roller, the free-surface curves gradually upwards. The passage of the bore roller is associated with some large water elevation fluctuations; the largest free-surface fluctuations are observed during the first half of the bore roller. The turbulent velocity measurements were performed at several vertical elevations during and shortly after the passage of breaking bores. Both the instantaneous and ensemble-averaged velocity data highlight a strong flow deceleration at all elevations during the bore passage. Close to the bed, the longitudinal velocity component becomes negative immediately after the roller passage, implying the existence of a transient recirculation. The height and duration of the transient are a function of the bed roughness, with a higher and longer recirculation region above the rough bed. The vertical velocity data presented some positive, upward motion beneath the front with increasing maximum vertical velocity with increasing distance from the bed. The transverse velocity data show some large fluctuations with nonzero ensemble average after the roller passage that highlight some intense secondary motion advected behind the bore front. DOI: 10.1061/(ASCE)HY.1943-7900.0000542. (C) 2012 American Society of Civil Engineers

Do Small Headgroups of Phosphatidylethanolamine and Phosphatidic Acid Lead to a Similar Folding Pattern of the K+ Channel?

Phospholipid headgroups act as major determinants in proper folding of oligomeric membrane proteins. The K+-channel KcsA is the most popular model protein among these complexes. The presence of zwitterionic nonbilayer lipid phosphatidylethanolamine (PE) is crucial for efficient tetramerization and stabilization of KcsA in a lipid bilayer. In this study, the influence of PE on KcsA folding properties was analyzed by tryptophan fluorescence and acrylamide quenching experiments and compared with the effect of anionic phosphatidic acid (PA). The preliminary studies suggest that the small size and hydrogen bonding capability of the PE headgroup influences KcsA folding via a mechanism quite similar to that observed for anionic PA

Bubble Entrainment, Spray and Splashing at Hydraulic Jumps

The sudden transition from a high-velocity, supercritical open channel flow into a slow-moving sub-critical flow is a hydraulic jump. Such a flow is characterised by a sudden rise of the free-surface, with some strong energy dissipation and air entrainment, waves and spray. New two-phase flow measurements were performed in the developing flow region using a large-size facility operating at large Reynolds numbers. The experimental results demonstrated the complexity of the flow with a developing mixing layer in which entrained bubbles are advected in a high shear stress flow. The relationship between bubble count rates and void fractions was non-unique in the shear zone, supporting earlier observations of some form of double diffusion process between momentum and air bubbles. In the upper region, the flow consisted primarily of water drops and packets surrounded by air. Visually significant pray and splashing were significant above the jump roller. The present study is the first comprehensive study detailing the two-phase flow properties of both the bubbly and spray regions of hydraulic jumps, a first step towards understanding the interactions between bubble entrainment and droplet ejection processes

De-studentification: emptying housing and neighbourhoods of student populations

This is the accepted version of a paper subsequently published in the journal, Environment and Planning A. The definitive version is available at: http://dx.doi.org/10.1177/0308518X16642446International scholarship on student geographies and urban change continues to advance knowledge of the intense commodification of student lifestyles and student housing. The main aim of this paper is to consider some of the hitherto under-researched wider knock-on effects of more commodified student housing markets. Here we present findings from the first-ever empirical study of de-studentification. Using the case study of Loughborough, we demonstrate how de-studentification is a process of change that has been stimulated by the increased supply of purpose-built student accommodation. We show that de-studentification leads to the depopulation and decline of some classical studentified neighbourhoods. Moreover, these urban transformations have several significant implications for pre-existing conceptualisations of urban change and student geographies. Notably, the impacts of de-studentification pose important questions for the conceptual boundaries of studentification – a prerequisite of de-studentification – and although, to date, dominant conceptualisations of studentification are wedded to upgrading-led representations of urban gentrification, it is shown that de-studentification, conversely, leads to physical downgrading and emptying of neighbourhoods in distinct phases. We therefore argue for a process-led definition of de-studentification, to illustrate how studentified neighbourhoods are gradually ‘emptied’ of student populations and student housing. More broadly, it is asserted that new student geographies are being created by the deepening neoliberalisation and commodification of higher education, which, in turn, will have unintentional consequences for wider social, cultural and economic relations in university towns and cities, such as emergent community cohesion and changing senses of place