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Browsing by Author "Sandborn, Virgil A., committee member"

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    Electrohydrodynamic flow in a barbed plate electrostatic precipitator
    (Colorado State University. Libraries, 1988) McKinney, Peter J., author; Davidson, Jane H., advisor; Wilbur, Paul J., committee member; Sandborn, Virgil A., committee member; Meroney, Robert N., committee member
    The large scale secondary flows and turbulence induced by the inhomogeneous negative corona discharge in the conventional wire-plate precipitator are known to reduce collection efficiencies, particularly in applications with high mass loadings of fine particulates. Electrohydrodynamic theory suggests that a modification in electrode geometry is necessary to control the electrically induced flow. A plate-plate precipitator using a barbed plate discharge electrode is designed to provide a more uniform current density distribution. Electrical and fluid dynamic characteristics of four model barbed plate electrodes, with varying plate-to-plate and barb spacing, are evaluated and compared to characteristics of a laboratory wire-plate precipitator in a specially designed wind tunnel facility. Current voltage characteristics of each electrode are presented and the visual appearance of the corona discharge discussed. Hot-film anemometer measurements of the turbulent flow field downstream of the active precipitator include mean and turbulence intensity profiles, as well as spectral analysis of the flow. Gas eddy diffusivities are estimated from integral length scale calculations. A laser light sheet is used to visualize the flow in the inter-electrode space. Results show that the electrical characteristics of the planar electrodes are well within the range needed for industrial precipitation and that the scale of the current in homogeneities within the precipitator are reduced. Fluid dynamic measurements confirm that electrode geometry has a significant effect on the electrohydrodynamic turbulence production. Turbulence intensity data indicate that the point discharges in the planar geometry cause higher turbulence levels than the wire discharges. Turbulent diffusivites are correspondingly higher in the planar geometry. These results indicate that mixing may actually be enhanced in the suggested design. Flow field measurements made downstream of the precipitator may not however be representative of the electrically induced flow within the precipitator. Plate end effects observed in the visualization procedure may have a significant effect on the downstream flow and bias the measurements. Additional study is necessary to determine if the planar geometry is a viable design. The most important test of any new precipitation design is measurement of its particle collection efficiency.
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    Sand dispersion in a laboratory flume
    (Colorado State University. Libraries, 1968) Yang, Tsung, author; Shen, H. W., advisor; Simons, Daryl B., committee member; Richardson, Everett V., committee member; Sandborn, Virgil A., committee member; Mielke, Paul W., committee member
    This study is concerned mainly with the longitudinal dispersion of sand particles along the bed of an alluvial channel under conditions of steady, uniform flow. Attention is focused on developing a general one-dimensional stochastic model to describe and predict the longitudinal dispersion process. The method of approach used by Sayre and Conover (1967) for a two-dimensional stochastic model, which described the movement of sand particles along an alluvial bed, is adapted here for the development of a general one-dimensional stochastic model. The parameters used in this general one-dimensional stochastic model can be obtained either from longitudinal dispersion and transport data, or from bed configuration data, or from a combination of both. The statistical analysis of ripple bed configurations indicates that the distribution of bed elevation closely follows a normal distribution, and may possess the ergodic property. The Aris moment equations are used to solve the problem of sand dispersion along an alluvial bed as a special case of the problem of dispersion of suspended sand particles near the bed. The Aris moment equations used in this study are modified forms of the conservation of mass equations for the transport, deposition, and re-entrainment of suspended sediment. When appropriate initial and boundary conditions are used, there is excellent agreement between solutions of the Aris moment equation and results given by the general one—dimensional stochastic model. Fine, medium, and coarse sized radioactive sand grains were used as tracer particles in experiments at two different flow conditions, namely, ripple and dune conditions. In spite of the irregularities of the experimental longitudinal dispersion curves caused by the irregularities of the bed configurations, the mean longitudinal displacement and the variance of the longitudinal distribution of the tracer particles were found to increase linearly with time, as required by the stochastic model. The shape of the experimental longitudinal dispersion curves could also be fairly well represented by the general one-dimensional stochastic model.
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    Steady upward flow from water tables
    (Colorado State University. Libraries, 1965) Arbhabhirama, Anat, author; Corey, Arthur T., advisor; Kemper, William D., committee member; Hanks, R. John, committee member; Sandborn, Virgil A., committee member
    The rate of upward flow from water tables is an important factor in irrigated areas for determining the depth at which water tables should be maintained. This study attempted to relate the maximum rate of upward flow to measurable soil parameters under various conditions of the soil-water system, and to determine more precisely the effect of hysteresis. Theoretical solutions were developed to determine the maximum upward flow rate as a function of depth of water table and necessary soil parameters. To verify these solutions, laboratory investigations were conducted. The experiments were conducted so that the ambient conditions did not affect the upward flow rates. Upward flow was induced at the top of the soil columns by means of an outflow siphon. An inflow siphon was connected to an inflow barrier at · the bottom of the soil column to maintain the water table as desired. Three conditions of the soil-liquid system were used, i.e., drainage, imbibition and imbibition-drainage cycles. The results gave good agreement between the theoretical solution and experimental results for both drainage and imbibition cycles. The imbibition-drainage cycle was conducted to study the effect of hysteresis. This effect caused the maximum rates of upward flow to drop 20 to 50 percent below the theoretical values.