7,547 research outputs found

    UMSL Bulletin 2023-2024

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    The 2023-2024 Bulletin and Course Catalog for the University of Missouri St. Louis.https://irl.umsl.edu/bulletin/1088/thumbnail.jp

    Graduate Catalog of Studies, 2023-2024

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    The Effects of Salt Precipitation During CO2 Injection into Deep Saline Aquifer and Remediation Techniques

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    The by-products of combustion from the utilisation of fossil fuels for energy generation are a source of greenhouse gas emissions, mainly Carbon dioxide (CO2). This has been attributed to climate change because of global warming. Carbon capture and storage (CCS) technology has the potential to reduce anthropogenic greenhouse gas emissions by capturing CO2 from emissions sources and stored in underground formations such as depleted oil and gas reservoirs or deep saline formations. Deep saline aquifers for disposal of greenhouse gases are attracting much attention as a result of their large storage capacity. The problem encountered during CO2 trapping in the saline aquifer is the vaporisation of water along with the dissolution of CO2. This vaporisation cause salt precipitation which eventually reduces porosity and impairs the permeability of the reservoir thereby impeding the storage capacity and efficiency of the technology. Salt precipitation during CO2 storage in deep saline aquifers can have severe consequences during carbon capture and storage operations in terms of CO2 injectivity.This work investigates and assesses, experimentally, the effects of the presence of salt precipitation on the CO2 injectivity, the factors that influence them on selected core samples by core flooding experiments, and remediation of salt precipitation during CO2 injection. The investigation also covered the determination of optimum range of deep saline aquifers for CO2 storage, and the effects of different brine-saturated sandstones during CO2 sequestration in deep saline aquifers. In this investigation, three (3) different sandstone core samples (Bentheimer, Salt Wash North, and Grey Berea) with different petrophysical properties were used for the study. This is carried out in three different phases for a good presentation.• Phase I of this study involved brine preparation and measurement of brine properties such as brine salinity, viscosity, and density. The brine solutions were prepared from different salts (NaCl, CaCl2, KCl, MgCl2), which represent the salt composition of a typical deep saline aquifer. The core samples were saturated with different brine salinities (5, 10, 15, 20, 25, wt.% Salt) and testing was conducted using the three selected core samples.• Phase II entailed the cleaning and characterisation of the core samples by experimental core analyses to determine the petrophysical properties: porosity and permeability. Helium Porosimetry and saturation methods were used for porosity determination. Core flooding was used to determine the permeability of the core samples. The core flooding process was conducted at a simulated reservoir pressure of 1500 psig, the temperature of 45 °C, with injection rates of 3.0 ml/min respectively. Interfacial tension (IFT) measurements between the CO2 and various brine salinities as used in the core flooding were also conducted in this phase. Remediation scenarios of opening the pore spaces of the core samples were carried out using the same core flooding rig and the precipitated core samples were flooded with remediation fluids (low salinity brine and seawater) under the same reservoir conditions. The petrophysical properties (Porosity, Permeability) of the core samples were measured before core flooding, after core flooding and remediation test respectively.• In phase III of the study, SEM Image analyses were conducted on the core samples before core flooding, after core flooding, and remediation test respectively. This was achieved by using the FEI Quanta FEG 250 FEG high-resolution Scanning Electron Microscope (SEM) interfaced to EDAX Energy Dispersive X-ray Analysis (EDX).xivResults from Bentheimer, Salt Wash North, and Grey Berea core samples indicated a reduction in porosity, permeability impairment, as well as salt precipitation. It was also found that, at 10 to 20 wt.% brine concentrations in both monovalent and divalent brine, a substantial volume of CO2 is sequestered, which indicates the optimum concentration ranges for storage purposes. The salting-out effect was greater in divalent salt, MgCl2 and CaCl2 as compared to monovalent salt (NaCl and KCl). Porosity decreased by 0.5% to 7% while permeability was decreased by up to 50% in all the tested scenarios. CO2 solubility was evaluated in a pressure decay test, which in turn affects injectivity. Hence, the magnitude of CO2 injectivity impairment depends on both the concentration and type of salt species. The findings from this study are directly relevant to CO2 sequestration in deep saline aquifers as well as screening criteria for carbon storage with enhanced gas and oil recovery processes. Injection of remediation fluids during remediation tests effectively opened the pore spaces and pore throats of the core samples and thereby increasing the core sample's porosity in the range of 14.0% to 28.5% and 2.2% to 12.9% after using low salinity brine and seawater remediation fluids respectively. Permeability also increases in the range of 40.6% to 68.4% and 7.4% to 17.2% after using low salinity brine and seawater remediation fluids respectively. These findings provide remediation strategies useful in dissolving precipitated salt as well as decreasing the salinity of the near-well brine which causes precipitation.The SEM images of the core samples after the flooding showed that salt precipitation not only plugged the pore spaces of the core matrix but also showed significant precipitation around the rock grains thereby showing an aggregation of the salts. This clearly proved that the reduction in the capacity of the rock is associated with salt precipitation in the pore spaces as well as the pore throats. Thus, insight gained in this study could be useful in designing a better mitigation technique, CO2 injectivity scenarios, as well as an operating condition for CO2 sequestration in deep saline aquifers

    The generation, propagation, and mixing of oceanic lee waves

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    Lee waves are generated when oceanic flows interact with rough seafloor topography. They extract momentum and energy from the geostrophic flow, causing drag and enhancing turbulent mixing in the ocean interior when they break. Mixing across density surfaces (diapycnal mixing) driven by lee waves and other topographic interaction processes in the abyssal ocean plays an important role in upwelling the densest waters in the global ocean, thus sustaining the lower cell of the meridional overturning circulation. Lee waves are generated at spatial scales that are unresolved by global models, so their impact on the momentum and buoyancy budgets of the ocean through drag and diapycnal mixing must be parameterised. Linear theory is often used to estimate the generation rate of lee waves and to construct global maps of lee wave generation. However, this calculation and subsequent inferences of lee wave mixing rely on several restrictive assumptions. Furthermore, observations suggest that lee wave mixing in the deep ocean is significantly overestimated by this theory. In this thesis, we remove some common assumptions at each stage of the lee wave lifecycle to investigate the reasons for this discrepancy and to motivate and inform future climate model parameterisations. Firstly, we investigate the way that seafloor topography is represented in lee wave parameterisations, finding that typical spectral methods can lead to an overestimate of wave energy flux. Next, we make the case for considering lee waves as a full water column process by modelling the effect of vertically varying background flows and the ocean surface on lee wave propagation. Finally, we take a holistic view of topographic mixing in the abyssal ocean, finding that deep stratified water mass interfaces may modify the nature of the lee wave field, and themselves contribute to mixing and upwelling in the deep ocean through topographic interaction.Open Acces

    Circulation Statistics in Homogeneous and Isotropic Turbulence

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    This is the committee version of a Thesis presented to the PostGrad Program in Physics of the Physics Institute of the Federal University of Rio de Janeiro (UFRJ), as a necessary requirement for the title of Ph.D. in Science (Physics). The development of the Vortex Gas Model (VGM) introduces a novel statistical framework for describing the characteristics of velocity circulation. In this model, the underlying foundations rely on the statistical attributes of two fundamental constituents. The first is a GMC field that governs intermittent behavior and the second constituent is a Gaussian Free field responsible for the partial polarization of the vortices in the gas. The model is revisited in a more sophisticated language, where volume exclusion among vortices is addressed. These additions were subsequently validated through numerical simulations of turbulent Navier-Stokes equations. This revised approach harmonizes with the multifractal characteristics exhibited by circulation statistics, offering a compelling elucidation for the phenomenon of linearization of the statistical circulation moments, observed in recent numerical simulation. In the end, a field theoretical approach, known as Martin-Siggia-Rose-Janssen-de Dominicis (MSRJD) functional method is carried out in the context of circulation probability density function. This approach delves into the realm of extreme circulation events, often referred to as Instantons, through two distinct methodologies: The First investigates the linear solutions and, by a renormalization group argument a time-rescaling symmetry is discussed. Secondly, a numerical strategy is implemented to tackle the nonlinear instanton equations in the axisymmetric approximation. This approach addresses the typical topology exhibited by the velocity field associated with extreme circulation events.Comment: Ph.D. Thesis - preliminary versio

    Development of core competencies for field veterinary epidemiology training programs

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    A workforce with the adequate field epidemiology knowledge, skills and abilities is the foundation of a strong and effective animal health system. Field epidemiology training is conducted in several countries to meet the increased global demand for such a workforce. However, core competencies for field veterinary epidemiology have not been identified and agreed upon globally, leading to the development of different training curricula. Having a set of agreed core competencies can harmonize field veterinary epidemiology training. The Food and Agriculture Organization of the United Nations (FAO) initiated a collective, iterative, and participative process to achieve this and organized two expert consultative workshops in 2018 to develop core competencies for field veterinary epidemiology at the frontline and intermediate levels. Based on these expert discussions, 13 competencies were identified for the frontline and intermediate levels. These competencies were organized into three domains: epidemiological surveillance and studies; field investigation, preparedness and response; and One Health, communication, ethics and professionalism. These competencies can be used to facilitate the development of field epidemiology training curricula for veterinarians, adapted to country training needs, or customized for training other close disciplines. The competencies can also be useful for mentors and employers to monitor and evaluate the progress of their mentees, or to guide the selection process during the recruitment of new staff

    Reynolds number dependence of turbulence induced by the Richtmyer-Meshkov instability using direct numerical simulations

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    This paper investigates the Reynolds number dependence of a turbulent mixing layer evolving from the Richtmyer-Meshkov instability using a series of direct numerical simulations of a well-defined narrowband initial condition for a range of different Reynolds numbers. The growth rate exponent of the integral width and mixed mass is shown to marginally depend on the initial Reynolds number Re0, as does the minimum value of the molecular mixing fraction. The decay rates of turbulent kinetic energy and its dissipation rate are shown to decrease with increasing Re0, while the spatial distribution of these quantities is biased towards the spike side of the layer. The normalised dissipation rate and scalar dissipation rate are calculated and are observed to be approaching a high Reynolds number limit. By fitting an appropriate functional form, the asymptotic value of these two quantities is estimated as 1.54 and 0.66. Finally, an evaluation of the mixing transition criterion for unsteady flows is performed, showing that even for the highest Re0 case the turbulence in the flow is not yet fully developed. This is despite the observation of a narrow inertial range in the turbulent kinetic energy spectra, with a scaling close to -3/2

    Dynamical description of spatio-temporally varying turbulent energy cascades

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    The spatio-temporally varying turbulent energy cascade dynamics in forced homogeneous/periodic turbulence is investigated with direct numerical simulations (DNS) and Helmholtz decompositions. The local in space and time cascade dynamics vastly differs from its spatio-temporal average manifestation. At scales larger than the Taylor scale, the solenoidal interscale transfer at most locations at most times increases or decreases the energy at the given scale in the frame moving with larger scales, i.e. Lagrangian transport. The solenoidal interscale transfer derives from the non-local in space vortex stretching/compression and tilting effects of its spatial vicinity. The irrotational cascade dynamics reduces to an exact balance between irrotational transport, irrotational interscale transfer and pressure-velocity. The typical fluctuations of these processes vastly exceed their spatio-temporal average values and the typical dissipation fluctuations. At scales below the Taylor scale, viscous effects increase in importance in the solenoidal dynamics. At the Kolmogorov scale solenoidal interscale transfer, Lagrangian transport and viscous effects are all important. In regions of low and moderate small-scale energy, and to a somewhat lesser extent in regions of high small-scale energy, there is rarely a local balance between interscale transfer and viscous effects. Lagrangian transport acts as a non-local in time and space link between interscale transfer and viscous effects. The spatially-averaged manifestation of the local cascade dynamics is an unsteady and approximately unidirectional energy cascade, which can be approximated with a hypothesis connecting the present interscale transfer with the future dissipation. The hypothesis can be used to develop non-equilibrium corrections to the low-pass filtered dynamics and second-order structure function scaling consistent with DNSs. We use the phenomenology of a time-lagged energy cascade to motivate a new redistributive dissipation scaling. The non-equilibrium dissipation scaling typically reduces to the redistributive dissipation scaling at low and moderate Reynolds numbers.Open Acces

    Transition Physics and Boundary-Layer Stability: Computational Modeling in Compressible Flow

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    Laminar-to-turbulent transition of boundary layers remains a critical subject of study in aerodynamics. The differences in surface friction and heating between laminar and turbulent flows can be nearly an order of magnitude. Accurate prediction of the transition region between these two regimes is essential for design applications. The objective of this work is to advance simplified approaches to representing the laminar boundary layer and perturbation dynamics that usher flows to turbulence. A versatile boundary-layer solver called DEKAF including thermochemical effects has been created, and the in-house nonlinear parabolized stability equation technique called EPIC has been advanced, including an approach to reduce divergent growth associated with the inclusion of the mean-flow distortion. The simplified approaches are then applied to advance studies in improving aircraft energy efficiency. Under the auspices of a NASA University Leadership Initiative, the transformative technology of a swept, slotted, natural-laminar-flow wing is leveraged to maintain laminar flow over large extents of the wing surface, thereby increasing energy efficiency. From an aircraft performance perspective, sweep is beneficial as it reduces the experienced wave drag. From a boundary-layer transition perspective, though, sweep introduces several physical complications, spawned by the crossflow instability mechanism. As sweep is increased, the crossflow mechanism becomes increasingly unstable, and can lead to an early transition to turbulence. The overarching goal of the present analysis then is to address the question, how much sweep can be applied to this wing while maintaining the benefits of the slotted, natural-laminar-flow design? Linear and nonlinear stability analyses will be presented to assess various pathways to turbulence. In addition, companion computations are presented to accompany the risk-reduction experiment run in the Klebanoff-Saric Wind Tunnel at Texas A&M University. Linear analyses assess a wide range of various configurations to inform experimentalists where relevant unstable content resides. A comparison between simulation and experimental measurements is presented, for which there is a good agreement
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