Academic literature on the topic 'Macropore flow'
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Journal articles on the topic "Macropore flow"
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Yi, Jun, Ye Yang, Muxing Liu, Wei Hu, Shulan Lou, Hailin Zhang, and Dongyou Zhang. "Characterising macropores and preferential flow of mountainous forest soils with contrasting human disturbances." Soil Research 57, no. 6 (2019): 601. http://dx.doi.org/10.1071/sr18198.
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Preferential flow can develop in soil macropores, and macropores are sensitive to human disturbances. This study investigated soil macropore features and the main factors controlling preferential flow at four sites with different levels of human disturbance in a mountainous area in Central China. The level of human disturbance decreased with increasing elevation, with the lowest elevation areas covered with coniferous trees (LF) > middle mountain areas covered with tea gardens (TG) > middle mountain areas covered with deciduous trees and mixed shrubs (MF) > subalpine areas covered with evergreen coniferous trees (HF). At each site, the soil macropore structure at 0–20 cm soil depth was analysed using computed tomography scans (0.6 mm resolution) and Image J software. Preferential flow was determined by analysing the breakthrough curve (BTC) of nitrate. The macroporosity, surface area density, mean macropore size, macropore number density, length density and node density were all ranked in the order of HF ≥ MF ≥ TG = LF. Less disturbed sites had stronger evidence of preferential flow as shown by faster breakthrough, longer tails and greater asymmetry of the BTCs. There were significant (P < 0.05) positive influences of soil macropore properties on pore water velocity and the solute dispersion coefficient. The dispersivity parameter was mainly affected by the macropore equivalent hydraulic radius. This study showed that human disturbance in the mountain forest areas significantly decreased soil macropores by changing soil physical properties (e.g. bulk density, texture and soil organic matter content) and root distribution, thus increasing the risk of surface runoff and nutrient losses.
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Larsbo, M., J. Koestel, and N. Jarvis. "Controls of macropore network characteristics on preferential solute transport." Hydrology and Earth System Sciences Discussions 11, no. 8 (August 12, 2014): 9551–88. http://dx.doi.org/10.5194/hessd-11-9551-2014.
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Abstract. In this study we examined the relationships between macropore network characteristics, hydraulic properties and state variables and measures of preferential transport in undisturbed columns sampled from four agricultural topsoils of contrasting texture and structure. Macropore network characteristics were computed from 3-dimensional X-ray tomography images of the soil pore system. Non-reactive solute transport experiments were carried out at five steady-state water flow rates from 2 to 12 mm h−1. The degree of preferential transport was evaluated by the normalised 5% solute arrival time and the apparent dispersivity calculated from the resulting breakthrough curves. Near-saturated hydraulic conductivities were measured on the same samples using a tension disk infiltrometer placed on top of the columns. Results showed that many of the macropore network characteristics were inter-correlated. For example, large macroporosities were associated with larger specific macropore surface areas and better local connectivity of the macropore network. Generally, an increased flow rate resulted in earlier solute breakthrough and a shifting of the peak concentration towards smaller drained volumes. Columns with smaller macroporosities, poorer local connectivity of the macropore network and smaller near-saturated hydraulic conductivities exhibited a greater degree of preferential transport. This can be explained by the fact that, with only two exceptions, global (i.e. sample-scale) continuity of the macropore network was still preserved at low macroporosities. Thus, for any given flow rate pores of larger diameter were actively conducting solute in soils of smaller near-saturated hydraulic conductivity. With less time for equilibration between the macropores and the surrounding matrix the transport became more preferential. Conversely, the large specific macropore surface area and well-connected macropore networks associated with columns with large macroporosities limit the degree of preferential transport because they increase the diffusive flux between macropores and the soil matrix and they increase the near-saturated hydraulic conductivity. The normalised 5% arrival times were most strongly related with the estimated hydraulic state variables (e.g. with the degree of saturation in the macropores R2 = 0.589), since these combine into one measure the effects of irrigation rate and the near-saturated hydraulic conductivity function, which in turn implicitly depends on the volume, size distribution, global continuity, local connectivity and tortuosity of the macropore network.
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Tofteng, Charlotte, Søren Hansen, and Henry E. Jensen. "Film and Pulse Flow in Artificial Macropores." Hydrology Research 33, no. 4 (August 1, 2002): 263–74. http://dx.doi.org/10.2166/nh.2002.0007.
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It is generally recognized that macropore flow may occur in unsaturated soil and that this should be taken into account when modelling flow of water and solutes in soil. The objective of the present study was to examine the water pressure potential conditions at which macropore flow may occur and to elucidate the nature of macropore flow. A laboratory setup consisting of a sand column 20 cm in diameter and 20 cm high with outlet into a 50 cm long glass tube was used. The outlet characteristics of the glass tube was either free to the atmosphere or the glass tube terminated in gravel. The tube diameters used were 3, 4, and 6 mm while the water application rates used were 1.2, 2.2, 12, and 18.5 mm h −1. Experiments covering 26 combinations of tube diameter, water application rate and outlet characteristics were conducted. Water entered the macropores at a water pressure potential in the overlying sand more or less equivalent to the water entry pressure potential of the macropore according to capillary theory. The nature of flow in the macropore was for the tubes of 3 mm and 4 mm in diameter predominantly pulse flow while film flow was more likely to occur in the tube of 6 mm in diameter. During pulse flow events a pressure potential gradient was consistently created in the sand column, the pressure potential decreasing to -20 cm to -30 cm corresponding approximately to the air entry pressure potential of the sand. The pulse flow events occurred repeatedly during the infiltration as long as water application was continued. When film flow occurred after a pulse flow event, the film flow continued at a water pressure potential less than -20 cm in the sand close to the opening of the artificial macropore.
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Larsbo, M., J. Koestel, and N. Jarvis. "Relations between macropore network characteristics and the degree of preferential solute transport." Hydrology and Earth System Sciences 18, no. 12 (December 16, 2014): 5255–69. http://dx.doi.org/10.5194/hess-18-5255-2014.
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Abstract. The characteristics of the soil macropore network determine the potential for fast transport of agrochemicals and contaminants through the soil. The objective of this study was to examine the relationships between macropore network characteristics, hydraulic properties and state variables and measures of preferential transport. Experiments were carried out under near-saturated conditions on undisturbed columns sampled from four agricultural topsoils of contrasting texture and structure. Macropore network characteristics were computed from 3-D X-ray tomography images of the soil pore system. Non-reactive solute transport experiments were carried out at five steady-state water flow rates from 2 to 12 mm h−1. The degree of preferential transport was evaluated by the normalised 5% solute arrival time and the apparent dispersivity calculated from the resulting breakthrough curves. Near-saturated hydraulic conductivities were measured on the same samples using a tension disc infiltrometer placed on top of the columns. Results showed that many of the macropore network characteristics were inter-correlated. For example, large macroporosities were associated with larger specific macropore surface areas and better local connectivity of the macropore network. Generally, an increased flow rate resulted in earlier solute breakthrough and a shifting of the arrival of peak concentration towards smaller drained volumes. Columns with smaller macroporosities, poorer local connectivity of the macropore network and smaller near-saturated hydraulic conductivities exhibited a greater degree of preferential transport. This can be explained by the fact that, with only two exceptions, global (i.e. sample scale) continuity of the macropore network was still preserved at low macroporosities. Thus, for any given flow rate, pores of larger diameter were actively conducting solute in soils of smaller near-saturated hydraulic conductivity. This was associated with larger local transport velocities and, hence, less time for equilibration between the macropores and the surrounding matrix which made the transport more preferential. Conversely, the large specific macropore surface area and well-connected macropore networks associated with columns with large macroporosities limit the degree of preferential transport because they increase the diffusive flux between macropores and the soil matrix and they increase the near-saturated hydraulic conductivity. The normalised 5% arrival times were most strongly correlated with the estimated hydraulic state variables (e.g. with the degree of saturation in the macropores R2 = 0.589), since these combine into one measure the effects of irrigation rate and the near-saturated hydraulic conductivity function, which in turn implicitly depends on the volume, size distribution, global continuity, local connectivity and tortuosity of the macropore network.
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Jiang, Xiaojin, Enheng Wang, Xiangwei Chen, Xiangyou Xia, and Changting Shi. "Field study on macropore flow in typical Black soils of northeast China." Canadian Journal of Soil Science 92, no. 3 (March 2012): 559–66. http://dx.doi.org/10.4141/cjss2010-041.
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Jiang, X., Wang, E., Chen, X., Xia, X. and Shi, C. 2012. Field study on macropore flow in typical Black soils of northeast China. Can. J. Soil Sci. 92: 559–566. Macropores are important preferential pathways for the transport of water and contaminants in soil. A series of hood infiltration experiments were conducted using dye tracers (Brilliant Blue FCF) at pressure heads of −5.0 cm, −3.0 cm, and −1.0 cm at a conventional tilled site on Keshan Farm, northeast China. The study objective was to combine the test method of dye tracing with a hood infiltrometer to analyze soil subjected to conventional tillage methods. Dye staining patterns and macroporous networks were analyzed by excavation, mapping, photography, and image analysis. Results showed that macropore flow began very near the soil surface under three pressures heads of −5.0 cm, −3.0 cm and −1.0 cm, and that a pressure head of −1.0 cm resulted in more lateral flow. Soil deeper than 40.0 cm was less disturbed, which resulted in good continuity. At pressure heads of −5.0, −3.0 and −1.0 cm, the dye staining technique resulted in maximum stained depths of 74.3, 60.7 and 64.7 cm, respectively, with maximum stained widths of 41.6, 41.5 and 47.9 cm, respectively (at depths from 14.0 to 28.0 cm). Soil under a pressure head of −1.0 cm had the highest initial and steady infiltration rates of 13.0 and 4.1 mm min−1, respectively. Soil under a pressure head of −5.0 cm showed the most connectivity. To distinguish the macropores from the interaction area of macropore flow and the soil matrix surrounding the macropores, the stained area was separated into different classes based on dye color.
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Bidwell, V. J., and H. R. Thorpe. "Kinematic cell model of macropore flow from intermittent irrigation pulses." Soil Research 39, no. 4 (2001): 837. http://dx.doi.org/10.1071/sr00070.
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Significant fluctuations in soil water flux were observed in the drainage hydrographs from lysimeters (1220 mm diam., 900 mm deep) of undisturbed field soil, recorded at 5-min intervals, in response to intermittent 1-min pulses of irrigation water (3.4 or 6.8 mm) at irregular time intervals (4–17 min). The hypothetical process for this phenomenon was flow through soil macropores, in association with non-linear sorption into soil micropores. The kinematic wave approach to analysing macropore flow was modelled as a series of bi-continuum cells, which can be expressed as a set of non-linear ordinary differential equations. This non-linear state-space description enables the use of MATLAB software for convenient coding of the model and numerical integration of the model response to transient water flux input. Model simulation of drainage response to the irrigation pulse sequences showed good prediction of the wetting and draining fronts of the hydrograph but gave only indicative prediction of the magnitudes and wavelengths of the flow fluctuations. The model demonstrates the sensitivity of macropore flow to variations in the intervals between irrigation pulses, and supports previous evidence of fluctuations in macropore flow even for single water flux input pulses under laboratory conditions.
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Zhang, Youyan, Zhe Cao, Fang Hou, and Jinhua Cheng. "Characterizing Preferential Flow Paths in Texturally Similar Soils under Different Land Uses by Combining Drainage and Dye-Staining Methods." Water 13, no. 2 (January 18, 2021): 219. http://dx.doi.org/10.3390/w13020219.
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Preferential flow paths have been widely characterized by many visualization methods. However, the differences in preferential flow paths under various land uses and their relationships to hydraulic properties remain uncertain. The objectives of this study are to (1) characterize preferential flow paths under various land uses (forest and orchard) by combining drainage and dye-staining methods and to (2) build a connection between preferential flow paths and hydraulic-related parameters and extract the proportion of preferential flow paths from the compounding effects of matrix flow and preferential flow. The dye-staining experiments were conducted in five sandy soils and one sandy clay loam in situ, including four soils from forest and two soils from orchards. A total of 47 soil cores, 4 cm in height and 9 cm in diameter, were collected in each layer of the dye-stained soils for drainage experiments in the laboratory. Dye coverage and hydraulically equivalent macropore parameters (macroporosity, pore size distribution, and number of macropores) and their relationships were analyzed. The results show that the volume of preferential flow is partly affected by the total macropore volume. The effect of macropores on preferential flow varies by macropore size distribution. Dye coverage exhibited a significant (P < 0.01) correlation with macroporosity (correlation coefficient 0.83). Based on the value of macroporosity or steady effluent rates, the part of the dye coverage that was due to preferential flow on the surface dye-stained soil (resulting from both matrix and preferential flow) could be identified in this study. Compared with orchards, forestland has more preferential flow paths in both surface soil and subsoil. Further studies are needed to quantify the 3-D preferential flow paths and build a connection between preferential flow paths and hydraulic properties.
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Naveed, Muhammad, Per Moldrup, Marcel G. Schaap, Markus Tuller, Ramaprasad Kulkarni, Hans-Jörg Vogel, and Lis Wollesen de Jonge. "Prediction of biopore- and matrix-dominated flow from X-ray CT-derived macropore network characteristics." Hydrology and Earth System Sciences 20, no. 10 (October 6, 2016): 4017–30. http://dx.doi.org/10.5194/hess-20-4017-2016.
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Abstract. Prediction and modeling of localized flow processes in macropores is of crucial importance for sustaining both soil and water quality. However, currently there are no reliable means to predict preferential flow due to its inherently large spatial variability. The aim of this study was to investigate the predictive performance of previously developed empirical models for both water and air flow and to explore the potential applicability of X-ray computed tomography (CT)-derived macropore network characteristics. For this purpose, 65 cylindrical soil columns (6 cm diameter and 3.5 cm height) were extracted from the topsoil (5 cm to 8.5 cm depth) in a 15 m × 15 m grid from an agricultural field located in Silstrup, Denmark. All soil columns were scanned with an industrial X-ray CT scanner (129 µm resolution) and later employed for measurement of saturated hydraulic conductivity, air permeability at −30 and −100 cm matric potential, and gas diffusivity at −30 and −100 cm matric potential. Distribution maps for saturated hydraulic conductivity, air permeability, and gas diffusivity reflected no autocorrelation irrespective of soil texture and organic matter content. Existing empirical predictive models for saturated hydraulic conductivity and air permeability showed poor performance, as they were not able to realistically capture macropore flow. The tested empirical model for gas diffusivity predicted measurements at −100 cm matric potential reasonably well, but failed at −30 cm matric potential, particularly for soil columns with biopore-dominated flow. X-ray CT-derived macroporosity matched the measured air-filled porosity at −30 cm matric potential well. Many of the CT-derived macropore network characteristics were strongly interrelated. Most of the macropore network characteristics were also significantly correlated with saturated hydraulic conductivity, air permeability, and gas diffusivity. The predictive Ahuja et al. (1984) model for saturated hydraulic conductivity, air permeability, and gas diffusivity performed reasonably well when parameterized with novel, X-ray CT-derived parameters such as effective percolating macroporosity for biopore-dominated flow and total macroporosity for matrix-dominated flow. The obtained results further indicate that it is crucially important to discern between matrix-dominated and biopore-dominated flow for accurate prediction of macropore flow from X-ray CT-derived macropore network characteristics.
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Franssen, Jan, Catherine Blais, Michel Lapointe, Francis Bérubé, Normand Bergeron, and Pierre Magnan. "Asphyxiation and entombment mechanisms in fines rich spawning substrates: experimental evidence with brook trout (Salvelinus fontinalis) embryos." Canadian Journal of Fisheries and Aquatic Sciences 69, no. 3 (March 2012): 587–99. http://dx.doi.org/10.1139/f2011-168.
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We investigated the distinct physical controls causing entombment and asphyxiation, the key mechanisms influencing salmonid egg-to-emergence (EtE) survival. Entombment occurs when sediment blocks the interstitial pathways (macropores) that larvae use to emerge from the streambed, while asphyxiation is related to low oxygen flux, which is a function of interstitial flow velocity. EtE survival has been related to substrate composition and flow velocity. However, in streambed sediments these variables are correlated, and few studies have examined the sensitivity of EtE survival to changes in velocity and oxygen flux at fixed substrate composition. EtE survival has not yet been directly related to the size and density of macropores. We incubated brook trout ( Salvelinus fontinalis ) embryos in artificial redds with different sediment compositions and hydraulic gradients to examine independently the effects of substrate composition, macropore geometry, and flow velocity on EtE survival, emergence timing, and fry condition. In situ measurements of macropore size were obtained using a computed tomography scanner. Despite high oxygen concentrations, we observed that entombment or blockage effects caused high embryo mortality in fines-rich substrates with few large macropores, and triggered early emergence of rare survivors. These outcomes could not be mitigated by increased flow velocity and oxygen flux to the egg pocket.
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Sternagel, Alexander, Ralf Loritz, Wolfgang Wilcke, and Erwin Zehe. "Simulating preferential soil water flow and tracer transport using the Lagrangian Soil Water and Solute Transport Model." Hydrology and Earth System Sciences 23, no. 10 (October 22, 2019): 4249–67. http://dx.doi.org/10.5194/hess-23-4249-2019.
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Abstract. We propose an alternative model concept to represent rainfall-driven soil water dynamics and especially preferential water flow and solute transport in the vadose zone. Our LAST-Model (Lagrangian Soil Water and Solute Transport) is based on a Lagrangian perspective of the movement of water particles (Zehe and Jackisch, 2016) carrying a solute mass through the subsurface which is separated into a soil matrix domain and a preferential flow domain. The preferential flow domain relies on observable field data like the average number of macropores of a given diameter, their hydraulic properties and their vertical length distribution. These data may be derived either from field observations or by inverse modelling using tracer data. Parameterization of the soil matrix domain requires soil hydraulic functions which determine the parameters of the water particle movement and particularly the distribution of flow velocities in different pore sizes. Infiltration into the matrix and the macropores depends on their respective moisture state, and subsequently macropores are gradually filled. Macropores and matrix interact through diffusive mixing of water and solutes between the two flow domains, which again depends on their water content and matric potential at the considered depths. The LAST-Model is evaluated using tracer profiles and macropore data obtained at four different study sites in the Weiherbach catchment in southern Germany and additionally compared against simulations using HYDRUS 1-D as a benchmark model. While both models show qual performance at two matrix-flow-dominated sites, simulations with LAST are in better accordance with the fingerprints of preferential flow at the two other sites compared to HYDRUS 1-D. These findings generally corroborate the feasibility of the model concept and particularly the implemented representation of macropore flow and macropore–matrix exchange. We thus conclude that the LAST-Model approach provides a useful and alternative framework for (a) simulating rainfall-driven soil water and solute dynamics and fingerprints of preferential flow as well as (b) linking model approaches and field experiments. We also suggest that the Lagrangian perspective offers promising opportunities to quantify water ages and to evaluate travel and residence times of water and solutes by a simple age tagging of particles entering and leaving the model domain.
Dissertations / Theses on the topic "Macropore flow"
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Rombang, Johan Alexander. "An investigation into subsurface macropore flow using an artificial macropose system." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336690.
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Ratcliffe, Elizabeth B. "Short-term hydrological responses of a forested hillslope during rainstorms, at Panola Mountain Research Watershed, Georgia, USA." Thesis, University of Bristol, 1996. http://hdl.handle.net/1983/099d7ff8-9ba5-41f8-ae62-78f063f8e8be.
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A small-scale filed experiment was conducted on a hillslope plot within the Georgia Piedmont, USA, with the aim of elucidating the hydrological processes which generate storm runoff and its chemistry. Intensive hydrometric and chemical sampling enabled the collection of detailed observations of hillslope processes during rainstorms. The passage of water was traced through a one-dimensional profile in the hillslope, where rainfall, throughfall, forest floor soil water, soil water at 15, 40, 50 and 70 cm depths, groundwaters and streamwaters were monitored, either manually or automatically. Chemical samples for each water type were also collected. From analysis of hydrometric data, several hydrological flowpaths were detected that contribute water to storm runoff. Direct channel rainfall is operative in all storms, although its detection is difficult. Overland flow is in operation at some locations on the hillslope, specially in topographic lows. Macropore and mesopore flow occurred and may lead to groundwater displacement. Groundwater ridging also occurred. Each flowpath was found to vary in its operation, according to a series of controls, namely seasonality, antecedent moisture conditions, rainfall magnitude, duration and intensity, and the timing between rainstorms. Conservative tracers (chloride and temperature) were employed to investigate the contribution of 'old' and 'new' water to storm runoff. The variation in chloride concentrations in samples collected either sequentially or manually at each flowpath was monitored throughout storms. Rainfall, comprising 'new' water, was found to exhibit a distinct chloride chemistry. Most samples contained < 20 μeq/l Cl⁻. A similar trend was observed for samples of through fall and forest floor soil water. Groundwaters and matrix soil waters contained two to three times greater chloride concentrations than in the 'new' waters, due to evaporative mechanisms. Hence, 'new' water could be distinguished from 'old' water on the basis of chloride chemistry. Similarly, the temperature profile of 'new' and 'old' waters were significantly different. During the summer, rainfall ('new' water) is warmer than groundwater ('old' water), and during the winter, the reverse is true. Hence, both chloride and temperature were instrumental in distinguishing 'old' from 'new' waters. Direct channel rainfall, overland flow and macropore flow were important flowpaths for the rapid transport of 'new' water through the system during the growing season. Overland flow contributed some 'old' water during the dormant season. Although macropore flow allowed rapid transit of 'new' water to depth, this led to a groundwater displacement mechanism, which ultimately led to the rapid contribution of 'old' water to storm runoff. The combination of hydrometric and tracer data enabled a conceptual hydrological model to be developed of the responses of the hillslope to storm events.
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Weiler, Markus Helmut Weiler Markus Helmut. "Mechanisms controlling macropore flow during infiltration : dye tracer experiments and simulations /." Zürich : ETH, Eidgenössische Technische Hochschule Zürich, IHW, Institut für Hydromechanik und Wasserwirtschaft, 2001. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=14237.
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Batany, Stéphane. "Influence d’un macropore sur l’écoulement et le transport de solutés en milieu poreux : expérimentations sur sol modèle macroporé et simulations numériques." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1085/document.
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La modélisation des écoulements et du transport dans les milieux poreux est un domaine actif pour, notamment, progresser dans la compréhension du transfert des polluants dans les sols. Les sols présentent fréquemment des hétérogénéités comme des macropores (provoqués par la faune, la flore ou des fissures) et un certain nombre de modèles numériques utilisent les concepts de double ou de multi-perméabilité pour tenir compte de tous les types d’écoulements susceptibles de coexister dans de tels systèmes. Cependant, les modèles classiques semblent sous-estimer l’effet de la macroporosité sur l’écoulement et le transfert préférentiels et restreindre la zone d’écoulement préférentiel au seul volume occupé par la macroporosité. Diverses études expérimentales antérieures à cette thèse ont questionné cette hypothèse. Cette étude se propose de comprendre l’établissement de l’écoulement et du transport préférentiel et en particulier les mécanismes d’échange d’eau et de masse entre un macropore et une matrice poreuse environnante en condition saturée. Pour cela, des traçages de l’eau sont réalisés pour un milieu poreux modèle constitué de billes de verre, traversé par un macropore synthétique et mis en place en colonnes de laboratoire. Elution et transfert dans les colonnes sont caractérisés par suivi de la concentration en sortie et par imagerie par résonance magnétique. Un modèle numérique développé sur la base de la méthode de Boltzmann sur réseau est utilisé pour simuler numériquement des écoulements dans un système macroporé et identifier les mécanismes d’écoulements préférentiels à l’échelle de pores. Les données expérimentales montrent que le transfert du traceur est fortement dépendant du débit d’injection ainsi que du coefficient de diffusion dans l’eau. À fort débit, le transfert semble s’effectuer exclusivement dans le macropore, avec très peu d’échange avec la matrice. Pour des débits plus faibles, la percée présente une inflexion suivie d’un pic. Les images IRM montrent alors un échange significatif de traceur entre le macropore et la matrice poreuse environnante. Les simulations numériques sont utilisées pour calculer le champ de vitesse de l’écoulement dans le système en fonction du débit. Les modélisations numériques montrent que l’écoulement préférentiel est étendu dans la matrice poreuse sur une zone de même dimension que le diamètre moyen des grains indépendamment de la taille du macropore et du débit, dans la gamme de débits simulés. Ces résultats expérimentaux et numériques montrent que l’influence du macropore sur les transferts doit être étendue dans la matrice poreuse sur une zone de la taille des grains pour l’écoulement et sur une zone dépendant du coefficient de diffusion du traceur ainsi que du temps de séjour moyen de celui-ci pour le transfert des solutésFlow and transport modeling through porous media is of primary concern nowadays, especially in order to progress in the understanding of pollutant transfers through soils. Soils present frequently heterogeneities such as macropores (caused by fauna, flora or cracks) and several numerical models use double or multi permeability concepts in order to take into account all flow types that may exist in such porous systems. Nevertheless, classical models seem underestimate the macropore effect on preferential flow and transport by restricting the preferential flow zone only to the volume occupied by the macroporosity. Various experimental studies prior to this thesis have questioned this hypothesis. This study proposes to understand the establishment of preferential flow and transport and in particular the mechanism of flow and solute exchanges between a synthetic macropore and a surrounding porous matrix in saturated condition. For this purpose, water tracing are realized for a model porous media constituted by glass beads, crossed by a synthetic macropore and implemented in laboratory columns. Breakthrough and transport in columns are characterized by monitoring the concentration at the end of the column by magnetic nuclear resonance. A numerical model developed on the basis of lattice-Boltzmann method is used to simul ate flow in macroporous system and identify preferential flow mechanisms at pore scale. Experimental data show that tracer transport is strongly dependent on injection flow rate and the diffusion coefficient in water. At high flow rate, the transport seems to occur exclusively in the macropore, with very little masse exchange with the porous matrix. At lower flow rates, the breakthrough exhibits an inflexion followed by a peak. The MRI images show a significant mass exchange of tracer between the macropore and the surrounding porous matrix. The numerical simulations are used to calculate the flow field in a porous system as a function of flow rate. They show that preferential flow is extended in porous matrix into a zone of same dimension the mean diameter of beads regardless of macropore size or injected flow rate, in the range of simulated flow rates. These experimental and numerical results show that macropore influence on transport should be extended through the surrounding porous matrix into a zone of the same size of grains diameter for flow and into a zone depending on diffusion coefficient as well as mean residence time of the studied tracer for solute transport
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Asare, Seth Ntiri. "Investigation of soil macroporosity and macropore flow in agricultural soils using volume CT scanner." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0007/NQ40361.pdf.
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Vivian, Benjamin James. "The role of rapid recharge processes in the initiation of landslides." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286619.
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Naveed, Muhammad, Per Moldrup, Marcel G. Schaap, Markus Tuller, Ramaprasad Kulkarni, Hans-Jörg Vogel, and de Jonge Lis Wollesen. "Prediction of biopore- and matrix-dominated flow from X-ray CT-derived macropore network characteristics." COPERNICUS GESELLSCHAFT MBH, 2016. http://hdl.handle.net/10150/621951.
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Prediction and modeling of localized flow processes in macropores is of crucial importance for sustaining both soil and water quality. However, currently there are no reliable means to predict preferential flow due to its inherently large spatial variability. The aim of this study was to investigate the predictive performance of previously developed empirical models for both water and air flow and to explore the potential applicability of X-ray computed tomography (CT)-derived macropore network characteristics. For this purpose, 65 cylindrical soil columns (6 cm diameter and 3.5 cm height) were extracted from the topsoil (5 cm to 8.5 cm depth) in a 15 m × 15 m grid from an agricultural field located in Silstrup, Denmark. All soil columns were scanned with an industrial X-ray CT scanner (129 µm resolution) and later employed for measurement of saturated hydraulic conductivity, air permeability at −30 and −100 cm matric potential, and gas diffusivity at −30 and −100 cm matric potential. Distribution maps for saturated hydraulic conductivity, air permeability, and gas diffusivity reflected no autocorrelation irrespective of soil texture and organic matter content. Existing empirical predictive models for saturated hydraulic conductivity and air permeability showed poor performance, as they were not able to realistically capture macropore flow. The tested empirical model for gas diffusivity predicted measurements at −100 cm matric potential reasonably well, but failed at −30 cm matric potential, particularly for soil columns with biopore-dominated flow. X-ray CT-derived macroporosity matched the measured air-filled porosity at −30 cm matric potential well. Many of the CT-derived macropore network characteristics were strongly interrelated. Most of the macropore network characteristics were also significantly correlated with saturated hydraulic conductivity, air permeability, and gas diffusivity. The predictive Ahuja et al. (1984) model for saturated hydraulic conductivity, air permeability, and gas diffusivity performed reasonably well when parameterized with novel, X-ray CT-derived parameters such as effective percolating macroporosity for biopore-dominated flow and total macroporosity for matrix-dominated flow. The obtained results further indicate that it is crucially important to discern between matrix-dominated and biopore-dominated flow for accurate prediction of macropore flow from X-ray CT-derived macropore network characteristics.
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Pechenik, Natalie. "Lateral macropore dominated flow on a clay settling area in the phosphate mining district, peninsular Florida." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0002982.
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Turpin, Karine. "Macropore flow and soil hydraulic properties as affected by manurebiosolids injector implements under variable soil physical conditions." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/27062.
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The aim of this study was to investigate, at various soil water contents, the tillage effects of two different types of injectors on soil hydraulic properties of a loamy clay soil located in Winchester, Ontario, Canada. The two injectors considered are the AerWay SSD (A) and the Kongskilde Vibro-Flex (K). The soil-properties changes associated with the injectors were assessed at ten different soil water contents for both injectors.
The first part of this research involves the evaluation of field saturated hydraulic conductivity (Kfs), matrix flux potential (&phis;m), bulk density (rhob) and volumetric water content (theta) for undisturbed soil (U) and for soil disturbed by injector (D). The field saturated hydraulic conductivities measured on disturbed soil for the Kongskilde (DK) were in 80% of the cases lower than those measured on undisturbed soil (UK). In contrast, Kfs measured on disturbed soil for the AerWay (DA) were higher in 90% of the cases. These results indicate that the Kongskilde reduces the infiltration capacity of the soil, which may be the result of reduced effective porosity via the smearing of the soil surface. They also indicate that the AerWay is facilitating infiltration, most likely by fracturing the soil surface.
The second part of this study involves a dye tracer experiment conducted on disturbed soil to evaluate the movement pathways of water through soil. In contrast to the AerWay, no relation could be established between liquid transport variables and the water content at which the Kongskilde was run. Greatest depths of penetration observed for the AerWay treatment occurred at run average water contents above 29.7 % vol. and below 19.7 % vol. Sorptive capacity of the upper layers was maximized when soil water contents were between 21.7 % vol. and 31.3 % vol.
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McEwen, Amiana Marie. "Abundance, Distribution, and Geometry of Naturally Occurring Macropores in Stream Banks." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/95948.
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Preferential flow paths are areas of substantially higher permeability than surrounding media. Macropores and soil pipes are a type of preferential flow path where conduit-like voids in the subsurface are typically greater than three millimeters in diameter. They are known to occur in agricultural and forest soils, often as a result of biological and physical processes. Macropores also exist in stream banks and have the potential to enhance the exchange of water and solutes between the channel and riparian groundwater, yet the geographic distribution of bank macropores is unknown. Here we determined the abundance, distribution, and geometry of naturally occurring surface-connected macropores in the banks of 20 streams across five physiographic provinces in the Eastern United States. We identified a total of 1,748 macropores, which were present in all 20 streams, with 3.8 cm average width, 3.3 cm average height, 11.5 cm average depth, and 27.9 cm average height above water surface elevation. Macropore abundance, distribution and geometry were statistically different between physiographic provinces, stream orders, and soil textures, with the latter being the most important. Macropores tended to be larger and more abundant in soils with a high cohesiveness and a low hydraulic conductivity compared to soils with a low cohesiveness and high hydraulic conductivity. As a result, streams with greater longitudinal heterogeneity of soil texture also had greater heterogeneity of macropore density. However, macropore size and height above baseflow water surface elevation also increased with stream order and therefore stream size. This work represents the first attempt to characterize macropores across a variety of riverine systems and presents evidence that macropores may play an important role in hyporheic exchange within stream banks. These results may have water quality implications, where macropores may enhance hyporheic exchange yet reduce the filtering capacity of riparian buffer zones.MS
Books on the topic "Macropore flow"
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The role of macropore flow from plot to catchment scale: A study in a semi-arid area. Utrecht: Koninklijk Nederlands Aardrijkskundig Genootschap, 2010.
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Mallawatantri, A. P. Pesticide sorption and degradation in macropores and soil horizons in the Palouse. Pullman, Wash: State of Washington Water Research Center, 1994.
Find full textBook chapters on the topic "Macropore flow"
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Nazarenko, Nelli N., and Anna G. Knyazeva. "Transfer of a Biological Fluid Through a Porous Wall of a Capillary." In Springer Tracts in Mechanical Engineering, 503–20. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-60124-9_22.
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AbstractThe treatise proposes a model of biological fluid transfer in a dedicated macropore with microporous walls. The distribution of concentrations and velocity studies in the capillary wall for two flow regimes—convective and diffusive. The largest impact on the redistribution of concentration between the capillary volume and its porous wall is made by Darcy number and correlation of diffusion coefficients and concentration expansion. The velocity in the interface vicinity increases with rising pressure in the capillary volume or under decreasing porosity or without consideration of the concentration expansion.
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"Macropore Flow." In Encyclopedia of Agrophysics, 436. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-90-481-3585-1_719.
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Germann, P. F. "MACROPORES AND MACROPORE FLOW, KINEMATIC WAVE APPROACH." In Encyclopedia of Soils in the Environment, 393–402. Elsevier, 2005. http://dx.doi.org/10.1016/b0-12-348530-4/00491-4.
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Germann, P. F. "Macropores and Macropore Flow, Kinematic Wave Approach." In Reference Module in Earth Systems and Environmental Sciences. Elsevier, 2013. http://dx.doi.org/10.1016/b978-0-12-409548-9.05212-x.
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Khire, M., and D. Saravanathiiban. "Micropore vs. macropore flow." In Coupled Phenomena in Environmental Geotechnics, 407–12. CRC Press, 2013. http://dx.doi.org/10.1201/b15004-52.
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Nortcliff, S., P. Nelson, V. L. Quisenberry, and R. E. Phillips. "The analysis of soil macropores and the flow of solutes." In Soil Micromorpohlogy: Studies in Management and Genesis, 601–12. Elsevier, 1993. http://dx.doi.org/10.1016/s0166-2481(08)70447-1.
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Keefer, Robert F. "Nature of Soil Erodibility." In Handbook of Soils for Landscape Architects. Oxford University Press, 1999. http://dx.doi.org/10.1093/oso/9780195121025.003.0008.
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Inherent properties of a soil determine the extent to which that soil will erode. These properties are soil texture, soil structure, soil permeability, and the amount of soil organic matter. Soil texture consists of a mixture of soil particle sizes of sand, silt, and clay. Soil texture is also related to water movement into the soil [infiltration] and water movement through a soil (permeability). Sand grains are large and difficult to move; however, they are easily detached. Clay particles often stick together and therefore are difficult to detach; however, once detached the clays remain suspended and are easily carried and separated from the original soil mass by water. Silt is intermediate in size between sand and clay, but silt is both easily detached and easily transported. Thus, any soil that has large amounts of silt will erode easily. Infiltration. Water moves into and within a soil through the large macropores and only a very limited amount in the small micropores. Sandy soils have many large pores allowing water to move into the soils by infiltration. Conversely, clay soils have many microspores through which water passes only very slowly. Therefore, during a moderate storm, runoff and erosion would be greater from a soil with more fine textured clays than from a soil where coarse texture dominates. Permeability. Once water enters a soil, it flows within the soil. The extent of internal movement of water in a soil is the permeability of that soil. A soil aggregate is a soil granule or soil crumb consisting of a number of soil grains, that is, silt or clay, held together by a cementing substance. Aggregation is the condition of a soil having many individual aggregates. Soils that have many large stable aggregate are more permeable and are difficult to detach and erode. An aggregate has stability when it is not broken easily by water. Soil aggregates help keep the soil receptive to rapid infiltration of water and keep water from moving over the soil and eroding it.
Conference papers on the topic "Macropore flow"
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Hager, John P., Todd Halihan, Todd Halihan, Lucie Guertault, Lucie Guertault, Garey Fox, and Garey Fox. "LABORATORY ELECTRICAL RESISTIVITY IMAGING OF MACROPORE FLOW." In Joint 53rd Annual South-Central/53rd North-Central/71st Rocky Mtn GSA Section Meeting - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019sc-327771.
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Hager, John P., Todd Halihan, Lucie Guertault, and Garey Fox. "ERI EVALUATION OF MACROPORE FLOW IN RIPARIAN AREAS." In GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-338452.
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Saravanathiiban, Duraisamy S., and Milind V. Khire. "Macropore Flow Modeling Using the Root Zone Water Quality Model." In IFCEE 2015. Reston, VA: American Society of Civil Engineers, 2015. http://dx.doi.org/10.1061/9780784479087.248.
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Nurul A. Akhand, David R. Lapen, Mark J. Edwards, Edward Topp, Lyne Sabourin, Bonnie R. Ball Coelho, Peter W. Duenk, and Michael Payne. "Tile Water Bacteria and Modeling Macropore Flow in Silt-Loam Structured Field Soils." In 2005 Tampa, FL July 17-20, 2005. St. Joseph, MI: American Society of Agricultural and Biological Engineers, 2005. http://dx.doi.org/10.13031/2013.19817.
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Knyazeva, A. G., and N. N. Nazarenko. "Modeling of flow of multi component biological fluid in macropore with microporous walls." In NEW OPERATIONAL TECHNOLOGIES (NEWOT’2015): Proceedings of the 5th International Scientific Conference «New Operational Technologies». AIP Publishing LLC, 2015. http://dx.doi.org/10.1063/1.4936027.
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Han, Jinju, Youngjin Seo, Juhyun Kim, Sunlee Han, and Youngsoo Lee. "Comparison of Oil Recovery and Carbonate Rock’s Properties Alterations by CO2 Miscible Flooding." In ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/omae2018-78723.
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This present study indicates experimental investigation about the impact of CO2 flooding on oil recovery and rock’s properties alteration in carbonate reservoir under the miscible condition. In order to compare the effect to initial pore characteristic, two type of carbonate rock was used; an Edward white represents homogeneous mainly consisted micropore, whereas an Indiana limestone represented heterogeneous mainly consisted macropore in this study. Under the miscible condition (9.65 MPa and 40°C), five pore volume of CO2 were injected into oil-wet carbonate rock, which was fully saturated with oil and connate water. After CO2 flooding, several analyses for each sample conducted to investigate oil recovery and rock properties change in porosity, permeability, and pore structure by chemical and physical reaction between CO2, water, and carbonate mineral before and after CO2 flooding by using core analysis, MICP, SEM, ICP, and X-ray CT techniques. From the results of oil recovery, it was more effective and larger in Edward white than in Indiana limestone. Because homogeneous characteristic with a large ratio of low permeable micropore in Edward white contributed to occur long reaction time between oil and CO2 for enough miscibility as well as to displace stably oil by CO2. Conversely, heterogeneous pore structure mainly consisted of high permeable conduit (macropore) in Indiana limestone has brought ineffective and low oil production. From the analysis of rock’s properties alteration, we found that, for the homogeneous sample, dissolution dominantly changed pore structure and became better flow path by improving permeability and reducing tortuosity. While plugging by precipitation of mineral particles was not critically affected rock’ properties, despite the sample mainly consisted small pores. In the case of the heterogeneous sample, both dissolution and precipitation critically affected change of rock’s properties and pore structure. In particular, superior precipitation in complex pore network seriously damaged flow path and change of rock’s properties. The largest porosity change markedly appeared in inlet section because of exposing rock surface from fresh CO2 during a long time. In conclusion, it shows that CO2 miscible flooding in carbonate reservoirs significantly affected to alteration of rock’s properties such as porosity, permeability, tortuosity, and pore connectivity, in particular in heterogeneous system compared with in homogeneous system. These experimental results can be useful to characterize carbonate rock as well as to study rock properties alteration on CO2 EOR and CCS processes.
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Di Maggio, Federica, Giulia Barbacini, Nicola Raimondi Cominesi, Dario Reolon, and Marco Pirrone. "AUTOMATIC FLOW-CALIBRATED PERMEABILITY LOG ESTIMATION THROUGH DUAL RANDOM FOREST ALGORITHM: HOW PREDICTIVE ANALYTICS ENHANCES THE CHARACTERIZATION OF HETEROGENEOUS CARBONATE RESERVOIRS." In 2021 SPWLA 62nd Annual Logging Symposium Online. Society of Petrophysicists and Well Log Analysts, 2021. http://dx.doi.org/10.30632/spwla-2021-0064.
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In carbonate reservoirs, the estimation of a reliable permeability log is a long-standing problem mainly because of the inherent multi-scale heterogeneities. The conventional approach relies on core-calibrated algorithms applied to open-hole (OH) logs. In general, this static log-based prediction uses to underestimate the actual dynamic performance of the wells and an ad-hoc integration with production logging tool (PLT) and well test (WT) analyses represents a required step to correct the initial estimation. However, it is critical, and at once challenging, to define the relation between dynamic-based corrections and OH characterization outcomes. An elegant solution is here proposed that makes use of predictive analytics applied on special core analyses (SCAL), nuclear magnetic resonance (NMR) log modeling, and multi-rate PLT/WT interpretations. The methodology is presented for a complex oil-bearing carbonate reservoir and it starts with an advanced NMR characterization performed downhole for more than 100 wells, and after a rigorous calibration with SCAL. The main outputs are a robust porosity partition (in terms of micropore, mesopore and macropore contributions), and a physics-based permeability formula. Although the match with core data demonstrates the reliability of the applied NMR rock characterization, log permeability underestimates the actual dynamic performances obtained from WT, as expected. At the same time, multi-rate PLT data from more than 150 wells are used to compute an apparent permeability value for each perforated interval, automatically consistent with the associated WT interpretation. Finally, both static and dynamic characterization outputs are used as inputs for a dual random forest (RF) template. In detail, the first RF algorithm learns through experience how NMR porosity partition and core-calibrated permeability are related to PLT/WT apparent permeability values, after considering the proper change of scale. Next, the second RF is utilized to estimate the uncertainty associated to the previous step, still in a completely data-driven way. Hence, the so-defined dual model provides a continuous automatic flow-calibrated permeability log, together with its confidence interval, directly from static NMR responses. The presented methodology allows dynamic data to be incorporate efficiently into a static workflow by means of a pure data-driven analytics approach. The latter is able to shed light on the statistical relationships hidden in the available datasets, thus leading to a more accurate permeability estimation. It is also shown how this provides fundamental information for perforation strategy optimization and reservoir modeling purposes in such carbonate rocks.
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Martin J. Shipitalo and Frank Gibbs. "Preferential Flow of Liquid Manure in Macropores and Cracks." In 2005 Tampa, FL July 17-20, 2005. St. Joseph, MI: American Society of Agricultural and Biological Engineers, 2005. http://dx.doi.org/10.13031/2013.18914.
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Wu, Weiwei, and Mukul M. Sharma. "Acid Fracturing Shales: Effect of Dilute Acid on Properties and Pore Structure of Shale." In SPE Hydraulic Fracturing Technology Conference. SPE, 2015. http://dx.doi.org/10.2118/spe-173390-ms.
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Abstract Many microfractures created during hydraulic fracturing are too small to be filled with proppants and are likely closed during production. However, for some shales that are rich in calcite (calcareous mudstones), such as the Bakken and Eagle Ford shale, dilute acids can be used while fracturing to maintain the conductivity of these microfractures under closure stress by non-uniformly etching the fracture surfaces. The mineralogy and pore structure of the shale and their evolution during acid fracturing are critical factors on the surface surface etching profile and the fluid leakoff. Therefore, understanding how acid dissolution changes the microstructure, petrophysical properties and pore structures of shale is essential in the design and application of acid fracturing in shales. In this paper changes in shale properties and pore structure by acid fracturing were demonstrated and visually observed for the first time with a scanning electron microscope. Acidized sections of a shale core sample were carefully isolated, and its microstructure, pore structure and petrophysical properties were systematically studied and compared with non-acidized sections of the core. Microstructure changes were found to be strongly dependent on mineral distribution, and several patterns were identified: channels developed in carbonate-rich regions; cavities or grooves formed in carbonate-rich islands or carbonate rings; and surface roughness was created in mixed zones of scattered carbonate and inert minerals. Inert minerals such as clay, organic matter stay relatively undisturbed in the structure, while some mineral grains can be dislodged from their original locations by dissolution of the surrounding carbonates. Many macropores with size up to 120 µm were created and mesopores mostly associated with clay gained more accessibility. Significantly increased permeability and porosity was measured in an acidized shale matrix. Brinell hardness measurements show that, as expected, the hardness of the shale was reduced by acidizing. This means that for acidizing to work effectively, it is important to not etch the fracture surfaces uniformly. Doing so will result in a reduction in the fracture conductivity under stress. The microstructure changes introduced by acid fracturing demonstrated in this study will result in the formation of surface asperities which is likely to improve the fracture conductivity of induced unpropped fractures. The acidized shale matrix close to the fracture surface with increased abundance of macropores and accessibility to mesopores may serve as a preferred pathway for fluid flow as well.
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Nagayama, Gyoko, Ryuji Ando, Kei Muramatsu, and Takaharu Tsuruta. "Fabrication of Macroporous on No-Mask Silicon Substrate for Application to Microsystems." In 2008 Second International Conference on Integration and Commercialization of Micro and Nanosystems. ASMEDC, 2008. http://dx.doi.org/10.1115/micronano2008-70323.
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We applied the anodic etching (i. e. photo assisted electrochemical etching) to the n type silicon substrate of orientation (100) without masking to fabricate macropores penetrated Si substrate. The anodic etching conditions of the macroporous formation were discussed and the effects of the resistivity, voltage, current density, electrolyte concentration and illumination etc. on the pore size and the porosity were investigated. The pores in high aspect ratio through the cross section of the silicon wafer were obtained with polishing and RIE (reactive ion etching) from the back side. It is found that the pore size at the back side is about 1.5 to 2 times larger than that of the front side. Also, as one example of the applications of porous silicon to microsystems, we demonstrate the results obtained in a micro fuel cell system using a porous silicon membrane (PSM). The PSM was fabricated by a porous silicon wafer which was filled with Nafion dispersion solution with ultrasonic vibrations. It was used as a proton conduction membrane by assembling into the H2 / air feed fuel cell at ambient conditions using conventional electrodes. We found that the Nafion filled PSM worked well and a maximum power density of 89.2 mW/cm2 were achieved under the flow rate of 100ml/min for H2 and 200ml/min for air.