Membrane separation is known as an economic and environmental friendly mode of separation and is used in various types of separation processes. The major challenges regarding membrane separation are the internal and external fouling of the membrane which reduces the permeate flux of the membranes by inducing extra resistance to flow. Synthetic membranes are designed and implemented to separate solutes or particles in a feed stream by rejecting them and permitting the liquid to pass through the membrane pores; however, most of the feed streams, such as wastewaters, contain more than one type of solute. This yields a distribution of particle sizes in the feed. Many wastewaters contain supracolloidal particles (1-100µm). Most membrane separations aim to remove these particles from the feed solution. Wastewaters also contain colloidal particles (0.001-1µm). These particles are less concentrated than supracolloidal particles in the feed but they are more problematic since they are able to penetrate into the membrane pores and cause internal fouling which is the main source of irreversible flux decline. Fouling mechanisms are traditionally classified into four types. Among these mechanisms, standard pore blocking (pore constriction) refers to internal fouling while the other types model external fouling. On the effect of pore geometry, as a morphological factor, studies to date have been limited to external membrane fouling. However, it is believed that up to 80% of the permeate flux can be affected by pore constriction which is caused by particle penetration and deposition into membrane pores (internal fouling). The effect of pore geometry, as a factor, in flux decline due pore constriction of membranes was investigated in this work. Pore constriction by particles was approximated by maximum particle deposition onto the interior wall of the pores and simulated using MATLAB image processing toolbox (MIPT). Sixteen different basic geometries were considered for the simulation of pore constriction by particles. These include circular pores, 3 groups of rectangular, triangular and oval geometries at four different aspect ratios (3, 7, 15 and 30) and three combined geometries of star, cross and a rectangle with rounded ends. The simulation of maximum particle deposition onto pore walls was carried out for a range of particle diameters to pore hydraulic diameters (λ) of 0.1 to the complete rejection of the particle by the pore. As the result of the simulation, the ratio of the available pore cross-sectional area after pore constriction to initial pore cross-sectional area (α) and the ratio of pore channel hydraulic diameter after pore constriction to initial pore hydraulic diameter (β) were measured and recorded. It was observed that for λ<0.2 (small particles compared to pore size) some geometries showed the same values of α and β. However, for λ>0.2, other geometries showed different values of α and β. It was also observed that several geometries reject the particle at different λ ratios. Using the values of α and β, the fluxes of membranes having different pore geometries, after pore constriction by particles, were calculated and compared. These results show that for a very small particle size, compared to pore size, there is no preference for a specific geometry over another; however, for intermediate particle sizes, membranes having triangular and star pore shapes provide higher fluxes compared to other membranes. The effect of pore aspect ratio (PAR) on the flux of membranes after pore constriction was also examined. In order to compare the combined effect of pore geometry on particle rejection and pore constriction, fluxes of membranes having different pore shapes were compared in light of several pore size distributions (PSDs). For this part of the study, the pore geometries of circular, rectangular, triangular and oval were considered at four PARs. Different values for the hydraulic diameter of the largest rejecting pore (D_(H,LRP)) were observed for different geometries. Rectangular pores showed the largest values of D_(H,LRP), at a constant PAR, which affirms their superior rejection behavior. The overall flux of the membranes after pore constriction was determined by a combination of three effects: the position of D_(H,LRP) in the PSD, the pore constriction behavior of the pore geometry and the shape of the PSD. Generally, for the PSDs for which most of the pores in the membrane physically reject the particles, membranes having rectangular pores showed higher fluxes, due to the greater rejection of particles. However, for PSDs for which a major number of pores are constricted by the particles, membranes with triangular pores offered higher flux after membrane pore constriction. The results of this work indicate a new direction for the design of membranes having defined pore geometries.

Membrane separation is known as an economic and environmental friendly mode of separation and is used in various types of separation processes. The major challenges regarding membrane separation are the internal and external fouling of the membrane which reduces the permeate flux of the membranes by inducing extra resistance to flow. Synthetic membranes are designed and implemented to separate solutes or particles in a feed stream by rejecting them and permitting the liquid to pass through the membrane pores; however, most of the feed streams, such as wastewaters, contain more than one type of solute. This yields a distribution of particle sizes in the feed. Many wastewaters contain supracolloidal particles (1-100µm). Most membrane separations aim to remove these particles from the feed solution. Wastewaters also contain colloidal particles (0.001-1µm). These particles are less concentrated than supracolloidal particles in the feed but they are more problematic since they are able to penetrate into the membrane pores and cause internal fouling which is the main source of irreversible flux decline. Fouling mechanisms are traditionally classified into four types. Among these mechanisms, standard pore blocking (pore constriction) refers to internal fouling while the other types model external fouling. On the effect of pore geometry, as a morphological factor, studies to date have been limited to external membrane fouling. However, it is believed that up to 80% of the permeate flux can be affected by pore constriction which is caused by particle penetration and deposition into membrane pores (internal fouling). The effect of pore geometry, as a factor, in flux decline due pore constriction of membranes was investigated in this work. Pore constriction by particles was approximated by maximum particle deposition onto the interior wall of the pores and simulated using MATLAB image processing toolbox (MIPT). Sixteen different basic geometries were considered for the simulation of pore constriction by particles. These include circular pores, 3 groups of rectangular, triangular and oval geometries at four different aspect ratios (3, 7, 15 and 30) and three combined geometries of star, cross and a rectangle with rounded ends. The simulation of maximum particle deposition onto pore walls was carried out for a range of particle diameters to pore hydraulic diameters (λ) of 0.1 to the complete rejection of the particle by the pore. As the result of the simulation, the ratio of the available pore cross-sectional area after pore constriction to initial pore cross-sectional area (α) and the ratio of pore channel hydraulic diameter after pore constriction to initial pore hydraulic diameter (β) were measured and recorded. It was observed that for λ<0.2 (small particles compared to pore size) some geometries showed the same values of α and β. However, for λ>0.2, other geometries showed different values of α and β. It was also observed that several geometries reject the particle at different λ ratios. Using the values of α and β, the fluxes of membranes having different pore geometries, after pore constriction by particles, were calculated and compared. These results show that for a very small particle size, compared to pore size, there is no preference for a specific geometry over another; however, for intermediate particle sizes, membranes having triangular and star pore shapes provide higher fluxes compared to other membranes. The effect of pore aspect ratio (PAR) on the flux of membranes after pore constriction was also examined. In order to compare the combined effect of pore geometry on particle rejection and pore constriction, fluxes of membranes having different pore shapes were compared in light of several pore size distributions (PSDs). For this part of the study, the pore geometries of circular, rectangular, triangular and oval were considered at four PARs. Different values for the hydraulic diameter of the largest rejecting pore (D_(H,LRP)) were observed for different geometries. Rectangular pores showed the largest values of D_(H,LRP), at a constant PAR, which affirms their superior rejection behavior. The overall flux of the membranes after pore constriction was determined by a combination of three effects: the position of D_(H,LRP) in the PSD, the pore constriction behavior of the pore geometry and the shape of the PSD. Generally, for the PSDs for which most of the pores in the membrane physically reject the particles, membranes having rectangular pores showed higher fluxes, due to the greater rejection of particles. However, for PSDs for which a major number of pores are constricted by the particles, membranes with triangular pores offered higher flux after membrane pore constriction. The results of this work indicate a new direction for the design of membranes having defined pore geometries.

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The purpose of this study was first to develop a method by which a detailed porosity classification system could be utilized to understand the relationship between pore/pore-throat geometry, genetic porosity type, and facies. Additionally, this study investigated the relationships between pore/pore-throat geometry, petrophysical parameters, and reservoir performance characteristics. This study focused on the Jurassic Smackover reservoir rocks of Grayson field, Columbia County, Arkansas. This three part study developed an adapted genetic carbonate pore type classification system, through which the Grayson reservoir rocks were uniquely categorized by a percent-factor, describing the effect of diagenetic events on the preservation of original depositional texture, and a second factor describing if the most significant diagenetic event resulted in porosity enhancement or reduction. The second part used petrographic image analysis and mercury-injection capillary pressure tests to calculate pore/pore-throat sizes. From these data sets pore/pore-throat sizes were compared to facies, pore type, and each other showing that pore-throat size is controlled by pore type and that pore size is controlled primarily by facies. When compared with each other, a pore size range can be estimated if the pore type and the median pore-throat aperture are known. Capillary pressure data was also used to understand the behavior of the dependent rock properties (porosity, permeability, and wettability), and it was determined that size-reduced samples, regardless of facies, tend to show similar dependent rock property behavior, but size-enhanced samples show dispersion. Finally, capillary pressure data was used to understand fluid flow behavior of pore types and facies. Oncolitic grainstone samples show unpredictable fluid flow behavior compared to oolitic grainstone samples, yet oncolitic grainstone samples will move a higher percentage of fluid. Size-enhanced samples showed heterogeneous fluid flow behavior while the size-reduced samples could be grouped by the number of modes of pore-throat sizes. Finally, this study utilized petrographic image analysis to determine if 2- dimensional porosity values could be calculated and compared to porosity values from 3-dimensional porosity techniques. The complex, heterogeneous pore network found in the Grayson reservoir rocks prevents the use of petrographic image analysis as a porosity calculation technique.

The purpose of this study was first to develop a method by which a detailed porosity classification system could be utilized to understand the relationship between pore/pore-throat geometry, genetic porosity type, and facies. Additionally, this study investigated the relationships between pore/pore-throat geometry, petrophysical parameters, and reservoir performance characteristics. This study focused on the Jurassic Smackover reservoir rocks of Grayson field, Columbia County, Arkansas. This three part study developed an adapted genetic carbonate pore type classification system, through which the Grayson reservoir rocks were uniquely categorized by a percent-factor, describing the effect of diagenetic events on the preservation of original depositional texture, and a second factor describing if the most significant diagenetic event resulted in porosity enhancement or reduction. The second part used petrographic image analysis and mercury-injection capillary pressure tests to calculate pore/pore-throat sizes. From these data sets pore/pore-throat sizes were compared to facies, pore type, and each other showing that pore-throat size is controlled by pore type and that pore size is controlled primarily by facies. When compared with each other, a pore size range can be estimated if the pore type and the median pore-throat aperture are known. Capillary pressure data was also used to understand the behavior of the dependent rock properties (porosity, permeability, and wettability), and it was determined that size-reduced samples, regardless of facies, tend to show similar dependent rock property behavior, but size-enhanced samples show dispersion. Finally, capillary pressure data was used to understand fluid flow behavior of pore types and facies. Oncolitic grainstone samples show unpredictable fluid flow behavior compared to oolitic grainstone samples, yet oncolitic grainstone samples will move a higher percentage of fluid. Size-enhanced samples showed heterogeneous fluid flow behavior while the size-reduced samples could be grouped by the number of modes of pore-throat sizes. Finally, this study utilized petrographic image analysis to determine if 2- dimensional porosity values could be calculated and compared to porosity values from 3-dimensional porosity techniques. The complex, heterogeneous pore network found in the Grayson reservoir rocks prevents the use of petrographic image analysis as a porosity calculation technique.

A pore-scale understanding of fluid flow underpins the constitutive laws of continuum-scale porous media flow. Porous media flow laws are founded on simplified pore structure such as the classical capillary tube model or the pore-network model, both of which do not include diverging-converging pore geometry in the direction of flow. Therefore, modifications in the fluid flow field due to different pore geometries are not well understood. Thus this may translate to uncertainties on how flow in porous media is predicted in practical applications such as geological sequestration of carbon dioxide, petroleum recovery, and contaminant’s fate in aquifers. To fill this gap, we have investigated the role of a spectrum of diverging-converging pore geometries likely formed due to different grain shapes which may be due to a variety of processes such as weathering, sediment transport, and diagenesis. Our findings describe the physical mechanisms for the failure of Darcy’s Law and the characteristics of Forchheimer Law at increasing Reynolds Number flows. Through fundamental fluid physics, we determined the forces which are most responsible for the continuum-scale porous media hydraulic conductivity (K) or permeability. We show that the pore geometry and the eddies associated therein significantly modify the flow field and the boundary stresses. This has important implications on mineral precipitation-dissolution and microbial growth. We present a new non-dimensional geometric factor β, a metric for diverging-converging pore geometry, which can be used to predict K. This model for K based on β generalizes the original and now widely-used Kozeny (1927) model which was based on straight capillary tubes. Further, in order to better quantify the feasibility of geological CO2 sequestration, we have conducted laboratory fluid flow experiments at reservoir conditions to investigate the controls of media wettability and grain shapes on pore-scale capillary trapping. We present experimental evidence for the snap-off or formation of trapped CO2 ganglion. The total trapping potential is found to be 15% of porosity for a water-wet media. We show that at the pore-scale media wettability and viscous-fingering play a critical role in transport and trapping of CO2. Our investigations clearly show that that in single-phase flow pore geometry significantly modifies pore-scale stresses and impacts continuum-scale flow laws. In two-phase flows, while the media wettability plays a vital role, the mobility ratio of CO2 - brine system significantly controls the CO2 capillary trapping potential- a result which should be taken into consideration while managing CO2 sequestration projects. / text

<div>An improved understanding of energy localization ("hot spots'') is needed to improve the safety and performance of explosives. In this work I establish a variety of experimental and computational methods to aid in the investigation of hot spots. In particular, focus is centered on the implicit relationship between hot spots and energetic material sensitivity. To begin, I propose a technique to visualize and quantify the properties of a dynamic hot spot from within an energetic composite subjected to ultrasonic mechanical excitation. The composite is composed of an optically transparent binder and a countable number of HMX crystals. The evolving temperature field is measured by observing the luminescence from embedded phosphor particles and subsequent application of the intensity ratio method. The spatial temperature precision is less than 2% of the measured absolute temperature in the temperature regime of interest (23-220 C). The temperature field is mapped from within an HMX-binder composite under periodic mechanical excitation.</div><div> </div><div> Following this experimental effort I examine the statistics behind the most prevalent and widely used sensitivity test (at least within the energetic materials community) and suggest adaptions to generalize the approach to bimodal latent distributions. Bimodal latent distributions may occur when manufacturing processes are inconsistent or when competing initiation mechanisms are present.</div><div> </div><div> Moving to simulation work, I investigate how the internal void structure of a solid explosive influences initiation behavior -- specifically the criticality of isolated hot spots -- in response to a shock insult. In the last decade, there has been a significant modeling and simulation effort to investigate the thermodynamic response of a shock induced pore collapse process in energetic materials. However, the majority of these studies largely ignore the geometry of the pore and assume simplistic shapes, typically a sphere. In this work, the influence of pore geometry on the sensitivity of shocked HMX is explored. A collection of pore geometries are retrieved from micrographs of pressed HMX samples via scanning electron microscopy. The shock induced collapse of these geometries are simulated using CTH and the response is reduced to a binary "critical'’ / "sub-critical'' result. The simulation results are used to assign a minimum threshold velocity required to exhibit a critical response to each pore geometry. The pore geometries are subsequently encoded to numerical representations and a functional mapping from pore shape to a threshold velocity is developed using supervised machine-learned models. The resulting models demonstrate good predictive capability and their relative performance is explored. The established models are exposed via a web application to further investigate which shape features most heavily influence sensitivity.</div><div> </div><div> Finally, I develop a convolutional neural network capable of directly parsing the 3D electronic structure of a molecule described by spatial point data for charge density and electrostatic potential represented as a 4D tensor. This method effectively bypasses the need to construct complex representations, or descriptors, of a molecule. This is beneficial because the accuracy of a machine learned model depends on the input representation. Ideally, input descriptors encode the essential physics and chemistry that influence the target property. Thousands of molecular descriptors have been proposed and proper selection of features requires considerable domain expertise or exhaustive and careful statistical downselection. In contrast, deep learning networks are capable of learning rich data representations. This provides a compelling motivation to use deep learning networks to learn molecular structure-property relations from "raw'' data. The convolutional neural network model is jointly trained on over 20,000 molecules that are potentially energetic materials (explosives) to predict dipole moment, total electronic energy, Chapman-Jouguet (C-J) detonation velocity, C-J pressure, C-J temperature, crystal density, HOMO-LUMO gap, and solid phase heat of formation. To my knowledge, this demonstrates the first use of the complete 3D electronic structure for machine learning of molecular properties. </div>