Simulating dioxane transport in a heterogeneous glacial aquifer system (Washtenaw County, Michigan) using publicly available models and data

The primary challenge in groundwater and contaminant transport modeling is obtaining the data needed for constructing, calibrating and testing the models. Large amounts of data are necessary for describing the hydrostratigraphy in areas with complex geology. Increasingly states are making spatial data available that can be used for input to groundwater flow models. The appropriateness of this data for large-scale flow systems has not been tested. This study focuses on modeling a plume of 1,4-dioxane in a heterogeneous aquifer system in Scio Township, Washtenaw County, Michigan. The analysis consisted of: (1) characterization of hydrogeology of the area and construction of a conceptual model based on publicly available spatial data, (2) development and calibration of a regional flow model for the site, (3) conversion of the regional model to a more highly resolved local model, (4) simulation of the dioxane plume, and (5) evaluation of the model's ability to simulate field data and estimation of the possible dioxane sources and subsequent migration until maximum concentrations are at or below the Michigan Department of Environmental Quality's residential cleanup standard for groundwater (85 ppb). MODFLOW-2000 and MT3D programs were utilized to simulate the groundwater flow and the development and movement of the 1, 4-dioxane plume, respectively. MODFLOW simulates transient groundwater flow in a quasi-3-dimensional sense, subject to a variety of boundary conditions that can simulate recharge, pumping, and surface-/groundwater interactions. MT3D simulates solute advection with groundwater flow (using the flow solution from MODFLOW), dispersion, source/sink mixing, and chemical reaction of contaminants. This modeling approach was successful at simulating the groundwater flows by calibrating recharge and hydraulic conductivities. The plume transport was adequately simulated using literature dispersivity and sorption coefficients, although the plume geometries were not well constrained.

Computational study of internal and external condensing flows and experimental synthesis to investigate their attainability and stability in ground-based and space-based environments

This doctoral thesis presents the computational work and synthesis with experiments for internal (tube and channel geometries) as well as external (flow of a pure vapor over a horizontal plate) condensing flows. The computational work obtains accurate numerical simulations of the full two dimensional governing equations for steady and unsteady condensing flows in gravity/0g environments. This doctoral work investigates flow features, flow regimes, attainability issues, stability issues, and responses to boundary fluctuations for condensing flows in different flow situations. This research finds new features of unsteady solutions of condensing flows; reveals interesting differences in gravity and shear driven situations; and discovers novel boundary condition sensitivities of shear driven internal condensing flows. Synthesis of computational and experimental results presented here for gravity driven in-tube flows lays framework for the future two-phase component analysis in any thermal system. It is shown for both gravity and shear driven internal condensing flows that steady governing equations have unique solutions for given inlet pressure, given inlet vapor mass flow rate, and fixed cooling method for condensing surface. But unsteady equations of shear driven internal condensing flows can yield different “quasi-steady” solutions based on different specifications of exit pressure (equivalently exit mass flow rate) concurrent to the inlet pressure specification. This thesis presents a novel categorization of internal condensing flows based on their sensitivity to concurrently applied boundary (inlet and exit) conditions. The computational investigations of an external shear driven flow of vapor condensing over a horizontal plate show limits of applicability of the analytical solution. Simulations for this external condensing flow discuss its stability issues and throw light on flow regime transitions because of ever-present bottom wall vibrations. It is identified that laminar to turbulent transition for these flows can get affected by ever present bottom wall vibrations. Detailed investigations of dynamic stability analysis of this shear driven external condensing flow result in the introduction of a new variable, which characterizes the ratio of strength of the underlying stabilizing attractor to that of destabilizing vibrations. Besides development of CFD tools and computational algorithms, direct application of research done for this thesis is in effective prediction and design of two-phase components in thermal systems used in different applications. Some of the important internal condensing flow results about sensitivities to boundary fluctuations are also expected to be applicable to flow boiling phenomenon. Novel flow sensitivities discovered through this research, if employed effectively after system level analysis, will result in the development of better control strategies in ground and space based two-phase thermal systems.

Hydrogeochemical controls on uranium in aquifers of the Jacobsville Sandstone

The occurrence of elevated uranium (U) in sandstone aquifers was investigated in the Upper Peninsula of Michigan, focusing on aquifers of the Jacobsville Sandstone. The hydrogeochemical controls on groundwater U concentrations were characterized using a combination of water sampling and spectral gamma-ray logging of sandstone cliffs and residential water wells. 235U/238U isotope ratios were consistent with naturally occurring U. Approximately 25% of the 270 wells tested had U concentrations above the U.S. Environmental Protection Agency Maximum Contaminant Level (MCL) of 30 μg/L, with elevated U generally occurring in localized clusters. Water wells were logged to determine whether groundwater U anomalies could be explained by the heterogeneous distribution of U in the sandstone. Not all wells with relative U enrichment in the sandstone produced water with U above the MCL, indicating that the effect of U enrichment in the sandstone may be modified by other hydrogeochemical factors. Well water had high redox, indicating U is in its highly soluble (VI) valence. Equilibrium modeling indicated that aqueous U is complexed with carbonates. In general, wells with elevated U concentrations had low 235U/238U activity ratios. However, in some areas U concentrations and 235U/238U activity ratios were simultaneously high, possibly indicating differences in rock-water interactions. Limited groundwater age dating suggested that residence time may also help explain variations in well water U concentrations. Low levels of U enrichment (4 to 30 ppm) in the Jacobsville sandstone may make wells in its oxidized aquifers at risk for U concentrations above the MCL. On average, U concentrations were highest in heavy mineral and clay layers and rip up conglomerates. Uranium concentrations above 4 ppm also occurred in siltstones, sandstones and conglomerates. Uranium enrichment was likely controlled by deposition processes, sorption to clays, and groundwater flow, which was controlled by permeability variations in the sandstone. Low levels of U enrichment were found at deltaic, lacustrine and alluvial fan deposits and were not isolated to specific depositional environments.

A REMOTE SENSING APPROACH TO CHARACTERIZE THE HYDROGEOLOGY OF MOUNTAINOUS AREAS: APPLICATION TO THE QUITO AQUIFER SYSTEM (QAS), ECUADOR

Climate change, intensive use, and population growth are threatening the availability of water resources. New sources of water, better knowledge of existing ones, and improved water management strategies are of paramount importance. Ground water is often considered as primary water source due to its advantages in terms of quantity, spatial distribution, and natural quality. Remote sensing techniques afford scientists a unique opportunity to characterize landscapes in order to assess groundwater resources, particularly in tectonically influenced areas. Aquifers in volcanic basins are considered the most productive aquifers in Latin America. Although topography is considered the primary driving force for groundwater flows in mountainous terrains, tectonic activity increases the complexity of these groundwater systems by altering the integrity of sedimentary rock units and the overlying drainage networks. Structural controls affect the primary hydraulic properties of the rock formations by developing barriers to flow in some cases and zones of preferential infiltration and subterranean in others. The study area focuses on the Quito Aquifer System (QAS) in Ecuador. The characterization of the hydrogeology started with a lineament analysis based on a combined remote sensing and digital terrain analysis approach. The application of classical tools for regional hydrogeological evaluation and shallow geophysical methods were useful to evaluate the impact of faulting and fracturing on the aquifer system. Given the spatial extension of the area and the complexity of the system, two levels of analysis were applied in this study. At the regional level, a lineament map was created for the QAS. Relationships between fractures, faults and lineaments and the configuration of the groundwater flow on the QAS were determined. At the local level, on the Plateaus region of the QAS, a detailed lineament map was obtained by using high-spatial-resolution satellite imagery and aspect map derived from a digital elevation model (DEM). This map was complemented by the analysis of morphotectonic indicators and shallow geophysics that characterize fracture patterns. The development of the groundwater flow system was studied, drawing upon data pertaining to the aquifer system physical characteristics and topography. Hydrochemistry was used to ascertain the groundwater evolution and verify the correspondence of the flow patterns proposed in the flow system analysis. Isotopic analysis was employed to verify the origin of groundwater. The results of this study show that tectonism plays a very important role for the hydrology of the QAS. The results also demonstrate that faults influence a great deal of the topographic characteristics of the QAS and subsequently the configuration of the groundwater flow. Moreover, for the Plateaus region, the results demonstrate that the aquifer flow systems are affected by secondary porosity. This is a new conceptualization of the functioning of the aquifers on the QAS that will significantly contribute to the development of better strategies for the management of this important water resource.

Becoming most fully ourselves : gender, voice, and ritual in dissertations

The writing and defense of the dissertation serve both as demonstration one is able to do the work of a scholar and as a rite of initiation. In contrast to much academic writing, dissertations generally adhere to narrowly conceived notions of academic discourse. I explore this within the context of an academic community in which under-representation remains a serious issue. This dissertation is about women writing dissertations. I draw from conversations with fifteen women, in or beyond, the process; friends’ anecdotes; published accounts; and, autobiographically, my experience. I suggest the dissertation’s initiatory role is at least as important as its scholarly role; during the process one establishes a sense of self as scholar, writer, and researcher. Students come to the dissertation with some notion of self as writer and scholar – a culturally negotiated sense that is more, or less, congruent with the culturally established self required for successful completion of the dissertation. The degree of congruence (or alternatively, harmony and dissonance) shapes the process of doing a dissertation. I argue that both the community and the language in which dissertations must generally be written are gendered masculine. Negotiating a voice that is acceptable in a dissertation while maintain fidelity to a sense of who one is seems more problematic as one’s distance from the center of dominant culture increases. Believing that agency lies in altering the reiteration of such processes, I worked with my committee to find ways to alter the process yet still do a dissertation I write in a variety of voices – essay and poetry as well as analytical – play with visual qualities of text, and experiment with non-verbal interpretations. These don’t exhaust possibilities, but do give a sense of how the rich variety of expression found in academe cam be brought into the dissertation. I thus demonstrate that one need not reconstitute herself through characteristic academic discourse in order to be initiated into the community of scholars. I suggest both the desirability of encouraging flexibility in the language, form, and process, of dissertations, and the theoretical necessity for such flexibility if the academic community is to become diverse. The writing and defense of the dissertation serve both as demonstration one is able to do the work of a scholar and as a rite of initiation. In contrast to much academic writing, dissertations generally adhere to narrowly conceived notions of academic discourse. I explore this within the context of an academic community in which under-representation remains a serious issue. This dissertation is about women writing dissertations. I draw from conversations with fifteen women, in or beyond, the process; friends’ anecdotes; published accounts; and, autobiographically, my experience. I suggest the dissertation’s initiatory role is at least as important as its scholarly role; during the process one establishes a sense of self as scholar, writer, and researcher Students come to the dissertation with some notion of self as writer and scholar – a culturally negotiated sense that is more, or less, congruent with the culturally established self required for successful completion of the dissertation. The degree of congruence (or alternatively, harmony and dissonance) shapes the process of doing a dissertation. I argue that both the community and the language in which dissertations must generally be written are gendered masculine. Negotiating a voice that is acceptable in a dissertation while maintain fidelity to a sense of who one is seems more problematic as one’s distance from the center of dominant culture increases. Believing that agency lies in altering the reiteration of such processes, I worked with my committee to find ways to alter the process yet still do a dissertation I write in a variety of voices – essay and poetry as well as analytical – play with visual qualities of text, and experiment with non-verbal interpretations. These don’t exhaust possibilities, but do give a sense of how the rich variety of expression found in academe cam be brought into the dissertation. I thus demonstrate that one need not reconstitute herself through characteristic academic discourse in order to be initiated into the community of scholars. I suggest both the desirability of encouraging flexibility in the language, form, and process, of dissertations, and the theoretical necessity for such flexibility if the academic community is to become diverse. The writing and defense of the dissertation serve both as demonstration one is able to do the work of a scholar and as a rite of initiation. In contrast to much academic writing, dissertations generally adhere to narrowly conceived notions of academic discourse. I explore this within the context of an academic community in which under-representation remains a serious issue. This dissertation is about women writing dissertations. I draw from conversations with fifteen women, in or beyond, the process; friends’ anecdotes; published accounts; and, autobiographically, my experience. I suggest the dissertation’s initiatory role is at least as important as its scholarly role; during the process one establishes a sense of self as scholar, writer, and researcher Students come to the dissertation with some notion of self as writer and scholar – a culturally negotiated sense that is more, or less, congruent with the culturally established self required for successful completion of the dissertation. The degree of congruence (or alternatively, harmony and dissonance) shapes the process of doing a dissertation. I argue that both the community and the language in which dissertations must generally be written are gendered masculine. Negotiating a voice that is acceptable in a dissertation while maintain fidelity to a sense of who one is seems more problematic as one’s distance from the center of dominant culture increases. Believing that agency lies in altering the reiteration of such processes, I worked with my committee to find ways to alter the process yet still do a dissertation I write in a variety of voices – essay and poetry as well as analytical – play with visual qualities of text, and experiment with non-verbal interpretations. These don’t exhaust possibilities, but do give a sense of how the rich variety of expression found in academe cam be brought into the dissertation. I thus demonstrate that one need not reconstitute herself through characteristic academic discourse in order to be initiated into the community of scholars. I suggest both the desirability of encouraging flexibility in the language, form, and process, of dissertations, and the theoretical necessity for such flexibility if the academic community is to become diverse. The writing and defense of the dissertation serve both as demonstration one is able to do the work of a scholar and as a rite of initiation. In contrast to much academic writing, dissertations generally adhere to narrowly conceived notions of academic discourse. I explore this within the context of an academic community in which under-representation remains a serious issue. This dissertation is about women writing dissertations. I draw from conversations with fifteen women, in or beyond, the process; friends’ anecdotes; published accounts; and, autobiographically, my experience. I suggest the dissertation’s initiatory role is at least as important as its scholarly role; during the process one establishes a sense of self as scholar, writer, and researcher Students come to the dissertation with some notion of self as writer and scholar – a culturally negotiated sense that is more, or less, congruent with the culturally established self required for successful completion of the dissertation. The degree of congruence (or alternatively, harmony and dissonance) shapes the process of doing a dissertation. I argue that both the community and the language in which dissertations must generally be written are gendered masculine. Negotiating a voice that is acceptable in a dissertation while maintain fidelity to a sense of who one is seems more problematic as one’s distance from the center of dominant culture increases. Believing that agency lies in altering the reiteration of such processes, I worked with my committee to find ways to alter the process yet still do a dissertation I write in a variety of voices – essay and poetry as well as analytical – play with visual qualities of text, and experiment with non-verbal interpretations. These don’t exhaust possibilities, but do give a sense of how the rich variety of expression found in academe cam be brought into the dissertation. I thus demonstrate that one need not reconstitute herself through characteristic academic discourse in order to be initiated into the community of scholars. I suggest both the desirability of encouraging flexibility in the language, form, and process, of dissertations, and the theoretical necessity for such flexibility if the academic community is to become diverse.

Parametric combustion modeling for ethanol-gasoline fuelled spark ignition engines

Ethanol-gasoline fuel blends are increasingly being used in spark ignition (SI) engines due to continued growth in renewable fuels as part of a growing renewable portfolio standard (RPS). This leads to the need for a simple and accurate ethanol-gasoline blends combustion model that is applicable to one-dimensional engine simulation. A parametric combustion model has been developed, integrated into an engine simulation tool, and validated using SI engine experimental data. The parametric combustion model was built inside a user compound in GT-Power. In this model, selected burn durations were computed using correlations as functions of physically based non-dimensional groups that have been developed using the experimental engine database over a wide range of ethanol-gasoline blends, engine geometries, and operating conditions. A coefficient of variance (COV) of gross indicated mean effective pressure (IMEP) correlation was also added to the parametric combustion model. This correlation enables the cycle combustion variation modeling as a function of engine geometry and operating conditions. The computed burn durations were then used to fit single and double Wiebe functions. The single-Wiebe parametric combustion compound used the least squares method to compute the single-Wiebe parameters, while the double-Wiebe parametric combustion compound used an analytical solution to compute the double-Wiebe parameters. These compounds were then integrated into the engine model in GT-Power through the multi-Wiebe combustion template in which the values of Wiebe parameters (single-Wiebe or double-Wiebe) were sensed via RLT-dependence. The parametric combustion models were validated by overlaying the simulated pressure trace from GT-Power on to experimentally measured pressure traces. A thermodynamic engine model was also developed to study the effect of fuel blends, engine geometries and operating conditions on both the burn durations and COV of gross IMEP simulation results.