Inaug.-diss.--Rostock.

Thesis (Ph. D.)--University of Chicago, 1908. / "Reprinted from the Physical review, vol. XXV., no. 2, August, 1907." Also available on the Internet.

In the literature there is limited data available on the behaviour of discharges with three dimensional trajectories, although these are the most commonly found in the flows exiting (ocean) outfalls. The necessary three dimensional trajectory data requires cumbersome experimental systems and specialised laboratory setup. Therefore, results from two dimensional trajectory experiments are commonly extrapolated to enable prediction of the flow trajectories and dilutions of discharges that follow three dimensional paths. Importantly, there are also still some aspects of the behaviour of discharges with two dimensional trajectories that are not entirely clear. Non-buoyant flows discharged at an angle to the ambient flow, oblique discharges, behave either like a strongly advected jet or a momentum puff, depending on the discharge angle. Previous research indicated that the transition angle lies between 20° and 40°. Furthermore there is no clear distinction made between the cross sectional flow structure of buoyant and non-buoyant discharges in a cross flow, advected thermals and momentum puffs, and flow prediction models, like Visjet or Corjet, which assume these flows spread at the same rate. The primary objectives of this research are to create a more comprehensive dataset for discharges with three dimensional trajectories; to ascertain the transitional discharge angle that separates flows that behave as a strongly-advected jet or a line momentum puff, and to establish whether there is a difference in the cross sectional concentration profiles of buoyant and non-buoyant discharges in a cross flow. The application of a double Gaussian distribution will be carried out for line advected thermals complimenting earlier work with line momentum puffs. The work feeds into these models and therefore can have an indirect impact on outfall design. A light attenuation system is employed to study the various discharges and the dynamic range is extended by developing a multiple dye system. This enables the evolution of the discharges to be measured over much greater distances. The light attenuation system is described in detail to substantiate the experimental results. The new data shows that the mean tracer distributions for buoyant and non-buoyant discharges in a cross flow are distinct, with the former having a greater peak separation than the latter. This leads to differences in the relationships between peak and centreline concentrations. In addition, while the experimental spreading rates for the two flows are similar, the different forms of the puff and thermal profiles require distinctly different spreading rates for standardised flow profile models, such as the ‘top hat’ models. Differences are also evident in the conversions needed to estimate peak values from the predictions of these standardised profiles and the implications of these differences are discussed in the context of integral models, which are commonly employed to predict the behaviour of such flows. The experimental data from the oblique discharge experiments showed that flows discharged at acute angles up to 32.4° displayed strongly advected jet behaviour, flows discharged at obtuse angles greater than 39.0° displayed momentum puff behaviour, while the intermediate 35.9° discharge appeared as some combination of the aforementioned flows. A comprehensive experimental investigation into the behaviour of discharges with 3D trajectories has been carried out. The flows were released horizontally at an angle of 90°, 45°, or at 22° to the ambient current and the ambient to initial velocity ratio varied from 0.0042 to 0.057, extending the range of initial conditions previously considered. The experiments show limited variability in trajectory and dilution results around the average values. This provides the basis for conducting future experiments with fewer repetitions. The flows with initial discharges angles of 90° and 45° to the ambient motion, display initially line momentum puff and afterwards advected thermal behaviour. The consistent appearance of the characteristic double peaked distributions alleviates previously published concerns about the ability to transfer the understanding gained from discharges that follow a two dimensional path. However, the different orientations of the two peaks within these flow regimes introduces additional complexity into the transition region. In experiments with an initial discharge angle of 22° the double peak distribution did not develop until the flow evolved into an advected thermal, which was consistent with expectations based on the experiments with oblique discharges.

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An atmospheric pressure argon glow discharge is shown to detect trace levels of carbohydrates in aqueous flowing systems, using either of two glow discharge solution interface configurations. The first configuration consists of an oscillating glow discharge sustained between a flowing aqueous cathode and platinum anode. Picomole and micromolar mass and concentration detection limits, respectively, are obtained for sucrose in an aqueous flow injection system when monitoring discharge oscillation frequency or discharge current. The second configuration consists of a non-oscillating glow discharge sustained between metallic electrodes near the flowing output of a high performance liquid chromatography system. A conductivity detector detects the acidic product formed when each carbohydrate elutes and is exposed to the glow discharge. This detector yields femtomole and nanomolar mass and concentration detection limits, respectively, for a variety of carbohydrates and competes with the best of the commercially available liquid chromatography carbohydrate detectors. An increase in the discharge electrode spacing or reduction in the liquid flow rate increases detector sensitivity, since the discharge area and solution exposure time are increased, respectively. The aqueous carbohydrate products formed from exposure to the glow discharge are similar to those formed from exposure to high energy radiation. Acid, hydrogen peroxide, and an absorbing species all form in amounts proportional to carbohydrate concentration and glow discharge exposure time, with yields approximating those encountered when using high energy radiation. / Graduation date: 1997

Three aspects of glow discharges have been studied: glow discharge oscillations, sputtering, and coupling between cathode and anode regions the two most important regions in a glow discharge. Cathode and anode processes are tightly coupled by electron and ion coupling effects. Both electron and ion coupling effects were observed by studying excited Ar atoms in the cathode and anode regions and observing laser-induced space charge variations and the optogalvanic effect. Laser-induced space charge variations in the glow discharge were observed by the change in potential of an electrical probe. This signal, called the optopotential signal, provides useful information about the cathode and anode processes, and may become another useful spectroscopic detection method. Glow discharge oscillations are old phenomena but our mechanistic understanding of the processes involved continues to grow. A mechanism study is important especially now since a new type of sensitive GC detector is being developed based on this phenomenon. A SPAN model of glow discharge oscillation is proposed: source formation, propagation, accumulation, and neutralization of space charges. Electrode coupling couples the neutralization and source formation processes thus completing the feedback loop necessary for some of the observed oscillations to occur. Four modes of oscillations were found. Emission, space potential and current monitoring, and forced oscillations were used to monitor and identify the mechanisms. Studies of cathodic sputtering with gas flow rates up to 2.13 L/min/jet were carried out in an Atomsource sputtering atomizer with Ar as the jet gas and Cu as the cathode sample. These flow rates are 20-fold greater than those normally used and were found to increase net sputtering yield significantly. A fourfold increase in net sputtering yield was observed when the number of jets in use was decreased from six to one, with the gas flow rate and other conditions held constant. Possible explanations for these effects are offered. / Graduation date: 1996

Thesis (Ph. D.)--University of Illinois. / "Scholastic record." Reprinted from the Physical review, vol. XXXI, no. 3, September, 1910.