VTechWorks Repository :: Browsing by Author "Wiggert, James M."

Browsing by Author "Wiggert, James M."

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Analysis of hydrologic systems
Chiang, Tsung-Ting (Virginia Tech, 1968-01-16)
It was found that the systems analysis technique is a useful tool for hydrologic systems and is not only applicable to artificial hydrologic systems but also to natural catchments. The general equation describing the relationship between surface runoff and rainfall excess of a hydrologic system is a second order nonlinear equation. The damping coefficient for hydrologic systems is approximately unity and the other parameters in the transfer function (Eq. 5-4) such as the time constant and the nonlinear parameter depend on basin characteristics and input intensity.
Analysis of hydrologic systems
Chiang, Tsung-Ting, 1936-; Wiggert, James M. (Water Resources Research Center, Virginia Polytechnic Institute, 1968)
Boundary layer transport of small particles
McCready, David (Virginia Polytechnic Institute and State University, 1984)
The transport of small particles across the aerodynamic boundary layer that developed over a smooth, flat, acrylic plate and their subsequent deposition was investigated. The velocity boundary layer over the flat plate was characterized for a wind tunnel mainstream velocity of 2 m/s. Particle deposition was quantified with respect to location on the experimental plate with a microscope. The deposition of 0.8, 0.9, 1.1, and 2.0 micron diameter unit density, polystyrene latex microspheres on to oil-coated, uncoated, upper, and lower surfaces was investigated. Although experimental deposition velocities exhibited run-to-run variation, they were significantly greater than those reported in the literature. A turbulent flow deposition model which included eddy diffusion, Brownian diffusion, inertial, and gravitational deposition mechanisms underestimated the experimental deposition velocities. The experimental plate was nonconductive and could not be electrically grounded. It appears the electrostatic attraction mechanism was responsible for the increased experimental deposition velocities; this mechanism was not included in the deposition model. There was no significant resuspension of 42 micron diameter microspheres deposited to an initially moist experimental plate after 6 hours in the wind tunnel at a mean air velocity of 2 m/s.
Corona switching: an osmogene mitigation technique
Atkinson, R. Dwight (Virginia Polytechnic Institute and State University, 1988)
Odorous gases such as hydrogen sulfide have long been associated with wastewater treatment plants, especially those with long forced mains which allow septic conditions to develop. With the encroachment of urban and suburban populations, many wastewater treatment plants are no longer located far enough from residential areas to prevent odor problems. This has lead to renewed efforts to develop odor control techniques. The application of high energy coronas as a means to oxidize odorous gases has been limited by the relatively small size of the corona region around a given charged wire, approximately 1 centimeter at an applied voltage of 35 kilovolts. Attempts to enlarge the effective corona region by spacing wires such that their coronas would overlap have failed due to corona extinction, the destructive interference of the electric fields surrounding adjacent charged wires. This study demonstrates that corona extinction can be avoided in a system of closely spaced wires flanked by grounded plates if the wires are energized individually instead of' simultaneously. By employing a rapid load-switching technique an essentially continuous corona sheet can be produced. A bench-scale device utilizing the rapid switching principle was constructed and its ability to remove odorous gases, including hydrogen sulfide, was demonstrated. The influence of parameters such as flowrate, inlet concentration, switching frequency, temperature, and humidity on removal efficiency was evaluated.
Determination of fractured aquifer characteristics from evaluation of pump tests of wells in the crystalline rocks of the Blue Ridge allocthon
Dawson, James W. (Virginia Polytechnic Institute and State University, 1988)
The Precambrian age rocks of the Blue Ridge thrust sheet near Roanoke, Virginia, comprise an igneous and metamorphic assemblage with the predominance of porosity and permeability of the formations attributed to secondary factors. Aquifer characteristics of transmissivity, storage coefficient, hydraulic conductivity and fracture NL) permeability are determined from evaluation of pump tests conducted on ground water supply wells developed in this fractured aquifer. Evaluation of pump test data indicates that aquifer response is similar to a double porosity medium in some instances. Comparison of pump tests at locations close to, and further removed from, the leading edge of the Blue Ridge Thrust Fault indicate little variability in fracture permeability. The data suggest that deep circulation of ground water in the Blue Ridge allochthon may be more likely than previously thought.
An examination of stream reaeration coefficients and hydraulic conditions in a pool-and-riffle stream
Smoot, James Lloyd (Virginia Polytechnic Institute and State University, 1988)
Oxygen transfer between flowing surface waters and the atmosphere can be mathematically described as a first-order reaction and is known as stream reaeration. The first-order rate coefficient or stream reaeration coefficient is a necessary input parameter to stream water-quality models and is partially controlled by the hydraulic conditions of the stream. These coefficients may vary for a given stream reach because of varying hydraulic characteristics brought about by streamflow changes. Hydraulic measurements and reaeration coefficient determinations were made on four pool-and-riffle reaches of Middle Fork Beargrass Creek near Louisville, Kentucky using the hydrocarbon gas tracer technique. Measurements were made on each reach for up to seven streamflow conditions ranging from extremely low to medium. Contrary to published findings applicable to reaches not characterized by a series of pools and riffles, the reaeration coefficient was shown to increase with increasing streamflow for all four reaches studied. Therefore, stream water-quality models developed for these, or similar, stream reaches using reaeration coefficients determined at normal streamflow conditions may over estimate the influence of atmospheric reaeration under a much lower flow condition, such as extreme low flow--the selected critical condition for which water-quality models are commonly developed. Twenty-five published equations used for estimating stream reaeration coefficients were evaluated using the measured hydraulic and reaeration data and were shown to generate highly variable and generally inaccurate predictions. Over half of the equations generated mean prediction errors of more than 50 percent. The best equation overall generated a mean prediction error of 15 percent. The equations were also shown to be highly sensitive to the methods used for determining the input parameter values. Four equations were statistically developed from the data collected in this research. Two of the equations provided more accurate estimates for the four studied reaches than any of the 25 published equations. Mean prediction errors for the two were 1.2 and 9.2 percent. For verification, the developed equations were also evaluated against the 25 published equations using published reaeration and hydraulic data from 39 hydrocarbon gas tracer measurements on other streams. The two developed equations which were most accurate for the four study reaches were also determined to be superior to all of the 25 published equations using the verification data. Mean prediction errors for the two equations using the verification data were 2.3 and 5.5 percent.
A finite element analysis of dissolved oxygen drawdown and sulfate production in strip mine spoil dams due to pyritic chemical reaction
Amend, Joseph Henry (Virginia Tech, 1975-05-06)
The problem of dissolved oxygen drawdown and sulfate production in strip mine spoil dams due to chemical reaction between an excess of pyrite, water, and dissolved oxygen is investigated. A finite element analysis is used to solve the diffusion-convection equation assuming steady state conditions and no internal oxygen sources. Oxygen recharge along the free surface is permitted. The analysis is performed in three steps. Step one calculates the nodal piezometric heads and elemental bulk fluid velocities. Steps two and three determine the nodal dissolved oxygen and sulfate concentrations. Solutions are presented for a wide range of soil permeabilities and dissolved oxygen reaction coefficients. It is found that as the dissolved oxygen reaction coefficients. decreased, the dissolved oxygen deficit decreased and the sulfate concentration increased. From these results it was found that the maximum dissolved oxygen deficit occurs at an internal point in the dam and the maximum sulfate concentration occurs on the downstream face of the dam. The computer program used in the analysis is written in FORTRMi IV computer language and requires a minimum of programming knowledge to implement.
Formulation of the particle size distribution effects on the rheology and hydraulics of highly-concentrated suspensions
Dabak, Turgay (Virginia Polytechnic Institute and State University, 1986)
A formulation was developed for the rheological characterization of highly concentrated suspensions, accounting for the physical effects of particle size distribution. A number of dimensionless parameters were developed signifying the physical characteristics of the solids and the vehicle fluid, and functionally related to the yield-stress and a flow parameter. Each of these expressions of the formulation contains an empirical dimensionless coefficient accounting for the interparticle and fluid/solid interactions that are not explained by the physical parameters involved. A formulation and a methodology were also developed for predicting the shear viscosity behavior of highly concentrated suspensions at low and high shear-rates through the use of three parameters signifying effects of particle size distribution. A number of applications were made using various non-coal and limited coal-liquid mixture data reported in the literature to demonstrate the general validity of the formulations. A methodology was proposed for the analysis of the particle size distribution effects on the overall optimum energy efficiency during hydraulic transportation and particle size reduction. The computer model developed for this purpose was employed to evaluate the transportation energy consumption and the energy consumed in the grinding process to prepare the slurry, in pipes of various sizes and lengths for a coal slurry of various specified particle size distributions and concentrations. Correlations obtained indicated the sensitivity of transportation energy efficiency to various parameters including the maximum packing concentration, relative concentration, specific surface area of particles, surface area mean size, pipe size and length, and annual mixture throughput. The results of combined energy calculations have shown that the particle size distribution and related physical parameters can significantly affect the energy efficiency due to both grinding and transportation, and the delivered cost of slurry fuels.
Ground water management in Virginia: a comparative evaluation of the institutional framework
Cox, William E. (Virginia Tech, 1976-03-05)
The general purpose of this study is the examination of the institutional framework for ground water management, with specific consideration given to Virginia as a case study. The following objectives are encompassed within the general goal of institutional evaluation: (1) identification of the physical determinants of institutional structure, (2) description of current management institutions in Virginia, (3) comparative evaluation of the Virginia institutional framework, and (4) development of institutional guidelines of general applicability and specific recommendations for Virginia. The principal physical characteristic of ground water that determines institutional requirements for management is the dependence of the resource on a broad range of natural processes and the resulting propensity toward a variety of externalities. These external effects exist among individual water uses and also involve a variety of land use practices, indicating the need for a management framework with the capability for integration of a broad scope of considerations. The oldest institutional framework for ground water decision-making consists of private rights that define the limits of individual action affecting the resource. Private rights are significant with regard to withdrawal of ground water, use of land that affects the resource, and use of aquifer storage space through artificial recharge operations. Development of rights in these areas has proceeded at varying rates among the states and has reached differing results, but private rights in general have been relatively ineffective in restraining excessive pumping and other activities adversely affecting the resource. The institutional framework for ground water management also encompasses a variety of statutory laws and programs involving all levels of government, Primary responsibilities of the federal government consist of quality protection and data collection. Developing federal planning procedures have a potentially significant impact on ground water management. In Virginia, state law establishes an administrative ground water allocation system for application within specially designated districts. The state also regulates a number of activities that threaten ground water quality and carries out a data collection and management program. The primary authority of the local level of government concerning ground water is land use control. The development of guidelines for improved ground water management institutions involves a variety of issues. One of the most basic consists of the dgree of governmental involvement and the division of responsibilities among the levels of government. Due to the traditional inability of private control measures to constrain ground water externalities and the need for mechanisms to provide for planning and other non-regulatory management functions, direct governmental involvement and control appear inevitable ag burdens placed on the resource increase, With regard to vesting of governmental authority, considerations of managerial capabilities and perspectives indicate that the state level of government should exercise primary authority. Other issues addressed in the general guidelines and the Virginia recommendations include the feasibility of an allocation program applicable solely to ground water, guidelines for determination of "beneficial use," scope of exemptions from controls, criteria for permit issuance, permit duration, and the scope and administrative structure of ground water quality protection programs.
Instantaneous unit hydrograph response by harmonic analysis
Phillippe, Jonathan T. (Jonathan Thomas), 1939-; Wiggert, James M. (Water Resources Research Center, Virginia Polytechnic Institute, 1969)
The integration of nonstructural methods into flood loss reduction programs:an evaluation of a remaining obstacle
Kelley, Donald M. (Virginia Tech, 1986-12-17)
Current U.S. Army Corps of Engineers water resources planning guidance directs the planners to consider all design alternatives with economic efficiency as the primary criterion. Recent criticism of the flood loss reduction planning is directed at the Corps. One criticism is that the traditional design practices of the Corps address only large flood events. The emphasis on large flood events precludes the use of nonstructural methods, whose economically feasible range is at smaller scales. However, the advantage of having nonstructural measures available to federal water resources planners is widely recognized. This study seeks to demonstrate that nonstructural means are at a disadvantage in the Corps planning process. It examines the institutional framework that directs the planning of these projects. Using data from Corps reports, the economically feasible ranges and optimal sizes are determined for selected nonstructural measures through a series of case studies. The resulting optimal sizes are compared to those recommended in the Corps reports. The optimal sizes of the nonstructural alternatives developed for this study are smaller than the recommended levels. In the current budget climate, the implementation of flood loss reduction projects may occur more frequently with the increased use of nonstructura1 measures since they require less investment.
Lift on a sphere in shear flow near flat channel bed
Ying, Ker-Jen (Virginia Tech, 1991)
The lift and drag forces exerting on a sphere immersed in a shear flow above a flat channel bed are evaluated by solving the steady three-dimensional Navier-Stokes equations. The numerical technique which combines the Newton iteration method and the finite element method is used to solve the non-linear Navier-Stokes equations. The technique first linearizes the non-linear terms in the partial differential equations, then solves the linearized equations by the finite element method. The Newton iteration method is used to linearize the non-linear equations. Since the iteration method requires a good initial guess, the linear solution of the partial differential equations is used for the initial guess, where the linear solution is the obtained by solving the differential equations without non-linear terms. The computer model developed can evaluate the lift coefficients of a sphere stationed at various distance from the channel bed. The computational results agree very well with the experimental measurements cited in the literature. The lift coefficient of the sphere changes with the undisturbed approaching velocity profile as well as the gap ratio which is the ratio of the distance between the sphere and the channel bed and the diameter of sphere. For fixed gap ratios, higher Reynolds number gives smaller lift coefficient than that of the lower Reynolds number. On the other hand, the lift coefficient also changes with the diameter of sphere for each fixed gap ratio. For small gap ratios, the lift coefficient increases as the diameter of sphere increases. For large gap ratios, the lift coefficient increases in the negative (downward) direction as the diameter of sphere increases.
Nondimensional analysis of spatially varied flow in rectangular channels
Johnson, Robert Wayne (Virginia Tech, 1966-08-05)
A nondimensional form of the basic differential equation for spatially varied flow with increasing discharge was developed in section VI. The main purpose of this thesis is the application of this nondimensional equation to rectangular channels of various roughness values. A rectangular channel with continuous flow was constructed in order to establish uniform flow. The channel roughness was altered by placing screen wire and wooden cubes in the channel. Manning roughness coefficients were determined from the observed values for uniform depth. The law of conservation of linear momentum was used to develop a differential equation for spatially varied flow with increasing discharge. By defining certain dimensionless parameters, this equation was altered to a dimensionless form. An IBM 7040 computer was used to solve this nondimensional equation for various conditions of slope, roughness, and discharge. When the channel slope and roughness were held constant, the theoretical profiles varied slightly over a wide range of discharge.
Numerical studies of unsteady flow of the James River
Contractor, Dinshaw N.; Wiggert, James M. (Water Resources Research Center, Virginia Polytechnic Institute and State University, 1972)
A solution of the two parameter gamma model to relate unit hydrograph features to basin characteristics
Cruise, James Franklin (Virginia Tech, 1977-11-15)
The problem of correlating unit hydrograph features to topographic and man-made basin characteristics received attention in this report. The unit graph features considered herein were the peak discharge and the time lag of basin response. In order to facilitate the desired regression analysis, the two-parameter gamma model proposed by Edson was utilized in the investigation. The parameters of the model were obtained by the simultaneous solution of the equations for unit graph peak and lag using observed unit hydrographs for 16 basins in the Piedmont region of North Carolina and 14 basins located in Northern Virginia. In the opinion of many, these parameters are a better measure of the complex relationship which exists between the runoff from a basin and the topographic features of that basin than are the values of the unit graph peak and lag time themselves. The basin characteristics utilized in the investigation were: basin area, length of the longest streamcourse in the basin, average stream slope between points 10 percent and 85 percent downstream of the headwaters, and the percent of the impervious area contained in the basin. This last factor served as a measure of the amount of urban development present in the watershed. The investigation was hampered by a regrettable lack of sufficient data to derive regression equations of good reliability. This fact was due to the reduction of the data into groups by narrow geographical ranges. Thus, the number of stations available for analysis in anyone group was insufficient for purposes of a reliable regression analysis. From the investigation, it appears that the most significant basin characteristics affecting runoff are length, slope, and urban development. The strongest regression equations were derived using those three characteristics. It appears that the length and slope factors give better results when combined in the form (L/√S).
A study of nutrient distributions and productivity potential in lake sediments
Burns, Bruce Bennett (Virginia Tech, 1974-03-15)
The purpose of this investigation was to study the sediment in the upper reaches of Claytor Lake. The lake is a manmade impoundment on the New River near Radford, Virginia. Eleven core samples, varying in length from 66 cm. to 141 cm, were taken from the lake. The concentration of various water quality parameters were determined for segments of the entire length of each core. An in vitro assay was performed in the laboratory to determine the productivity potential of the nutrients contained in the sediments. Results of this investigation showed that sufficient nutrients are contained in the sediments to sustain algae growth. These nutrients, when released under controlled conditions, were found to sustain abundant growth of three algal genera: S. capricornutum, A. flosaguae, and M. aeruginosa. Several nutrients were found to exhibit trends with sediment depth and also to correlate with each other. Particle size distributions were also determined on several of the sediment samples. Several nutrients were found to correlate with particle size of the sediment.
A synthetic unit sedimentgraph for ungaged watersheds
Chen, Victor J. (Virginia Polytechnic Institute and State University, 1984)
The concept of the unit sediment graph is important and useful in the study of non-point source pollutant transport, in the estimation of sediment yield and in the design of sediment basins. At the present time, a physically sound method of deriving unit sediment graphs for ungauged small watersheds is not available. Based on synthetic principles as well as linear and time-invariant principles, applied to the systems approach of hydrology, a synthetic model has been developed to derive the unit sediment graph and to generate the sediment graph for an ungauged watershed. The model is limited to the generation of single peak sediment graphs where the sediment particle sizes of interest range from 0.002 mm to 1.0 mm. Seven small watersheds located in the lower Potomac River Basin were selected for this study. For each watershed about 12 storm events were included in the study. Available hourly rainfall and streamflow data were collected and used for model calibration. Results of both"spatial" and"temporal" verification show that agreement between the synthetic and actual sediment graphs is fairly good. A new rigorous definition regarding the unit sediment graph has been established. The study is based on a one-hour unit sediment graph which is defined as the direct sediment graph resulting from 1 unit of effective sediment yield of a storm of 1-hour duration generated uniformly over the basin at a uniform rate. Thus, the one-hour sediment graph of a storm for a specified watershed can be generated by convolving the one-hour unit sediment graph with the effective sediment erosion of one hour duration provided that the rainfall record and characteristics of that watershed are known.
Treatment of overflows from combined sewers
Colston, Newton V. (Virginia Tech, 1968-04-15)
Introduction: Automation and the danger of over productivity have created unprecedented amounts of leisure time in the United States. We are now in the process of finding that major potential recreational areas have been seriously polluted by the by-products of the same automation and productivity which have created our leisure time. Increasing urbanization has been accompanied by progressively more stringent demands on water quality and quantity while steadily impairing the same parameters . One of the major sources of water quality impairment due to concentrated urban growth is combined sewer overflow...

Browsing by Author "Wiggert, James M."

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