Soil water‐logging and flooding are common environmental stress conditions that can impair plant fitness. Roots are the first organs to be confronted with reduced oxygen tension as a result of ...flooding. While anatomical and morphological adaptations of roots are extensively studied, the root system architecture is only now becoming a focus of flooding research. Adventitious root (AR) formation shifts the root system higher up the plant, thereby facilitating supply with oxygen, and thus improving root and plant survival.
We used Arabidopsis knockout mutants and overexpressors of ERFVII transcription factors to study their role in AR formation under hypoxic conditions and in response to ethylene.
Results show that ethylene inhibits AR formation. Hypoxia mainly promotes AR elongation rather than formation mediated by ERFVII transcription factors, as indicated by reduced AR elongation in erfVII seedlings. Overexpression of HRE2 induces AR elongation to the same degree as hypoxia, while ethylene overrides HRE2‐induced AR elongation.
The ERFVII transcription factors promote establishment of an AR system that is under negative control by ethylene. Inhibition of growth of the main root system and promotion of AR elongation under hypoxia strengthens the root system in upper soil layers where oxygen shortage may last for shorter time periods.
Mechanisms of innate immunity contribute to inflammation, one of the major underlying causes of atherogenesis and progression of atherosclerotic vessel disease. How immune cells exactly contribute to ...atherosclerosis and interact with molecules of cholesterol homeostasis is still a matter of intense research. Recent evidence has proposed a potential role of previously underappreciated cell types in this chronic disease including platelets and dendritic cells (DCs). The pathophysiology of atherosclerosis is studied in models with dysfunctional lipid homeostasis and several druggable molecular targets are derived from these models. Specific therapeutic approaches focussing on these immune mechanisms, however, have not been successfully introduced into everyday clinical practice, yet. This review highlights molecular insights into immune processes related to atherosclerosis and potential future translational approaches targeting these molecular mechanisms.
Abstract Karst aquifers can be particularly vulnerable to human activities and climate change due to their relatively high degree of connection with the surface. This study utilized an ensemble of ...event-based recharge calculation methods to address the problem of structural uncertainty for the example of the Western Mountain Aquifer (WMA), a Mediterranean karst aquifer located in Israel and the West Bank. Spatially distributed recharge estimates derived from the Soil and Water Assessment Tool (SWAT) and the process-based infiltration model (PIM) were compared to site-specific, empirical regression models. The SWAT and PIM mean annual recharge estimates ranged from 32–34.6% of precipitation, almost equating to the results of empirical regression models (32–36%). Future recharge predictions under the influence of climate change were quantified by parameterizing the SWAT and PIM methods with a downscaled regional climate model of Israel. SWAT predicts a 23% decrease in recharge by 2051–2070 relative to 1981–2001. In contrast, PIM shows a 9% decrease, possibly due to the representation of infiltration through preferential flow pathways and exclusion of surface runoff processes. These divergent projections underline key methodological differences in the representation of hydrological processes. Nevertheless, both methods effectively provided good estimates of groundwater recharge. The recharge rates estimated from the various methods were integrated into MODFLOW to assess their relative impacts on groundwater storage dynamics. The ensemble of MODFLOW projected groundwater storage outputs can provide guidance for sustainable groundwater management in the region.
Résumé Les aquifères karstiques peuvent être particulièrement vulnérables aux activités humaines et au changement climatique en raison de leur relativement haut degré de connexion avec la surface. Cette étude a utilisé un ensemble des méthodes de calcul de recharge basée sur des événements pour résoudre la problème de l’incertitude structurelle pour l’exemple de l’aquifère de la montagne occidentale (WMA), un aquifère karstique méditerranéen située en Israël et Cisjordanie. Les estimations de la recharge distribuée spatialement déduite de l’outil SWAT (Evaluation Sol et Eau) et du modèle d’infiltration basée sur les processus (PIM) ont été comparées aux modèles de régression empirique spécifiques au site. Les estimations de la recharge moyenne annuelle à partir des modèles SWAT et PIM sont comprises entre 32 et 34.6% des précipitations, ce qui équivaut presque aux résultats des modèles de régression empiriques (32-36%). Les prévisions de recharge future sous influence de changement climatique ont été quantifiées en paramétrant les méthodes SWAT et PIM avec un modèle climatique régional de descente d’échelle pour Israël. Le modèle SWAT prédit une diminution de 23% de la recharge pour la période 2051-2070 par rapport à la période 1981-2001. En revanche, le modèle PIM indique une diminution de 9%, due probablement à la représentation de l’infiltration par des voies d’écoulement préférentielles et à l’exclusion des processus de ruissellement de surface. Ces projections divergentes soulignent des différences méthodologiques clés dans la représentation des processus hydrologiques. Néanmoins, les deux méthodes ont fourni de bonnes estimations de la recharge des eaux souterraines. Les taux de recharge estimés à partir des différentes méthodes ont été intégrés dans MODFLOW pour évaluer leurs impacts relatifs sur la dynamique de stockage des eaux souterraines. L’ensemble des résultats de projections du stockage des eaux souterraines de MODFLOW peut fournir des orientations pour une gestion durable des eaux souterraines dans la région.
Resumen Los acuíferos kársticos pueden ser especialmente vulnerables a las actividades humanas y al cambio climático debido a su grado relativamente alto de conexión con la superficie. Este estudio utilizó un conjunto de métodos de cálculo de recarga basados en eventos para abordar el problema de la incertidumbre estructural para el ejemplo del Acuífero de la Montaña Occidental (AMO), un acuífero kárstico mediterráneo situado en Israel y Cisjordania. Las estimaciones de recarga distribuidas espacialmente derivadas de Soil and Water Assessment Tool (SWAT) y del modelo de infiltración basado en procesos (PIM) se compararon con modelos de regresión empíricos específicos para cada emplazamiento. Las estimaciones de recarga media anual de SWAT y PIM oscilaron entre el 32-34,6% de las precipitaciones, casi igualando los resultados de los modelos de regresión empírica (32-36%). Las predicciones futuras de recarga bajo la influencia del cambio climático se cuantificaron parametrizando los métodos SWAT y PIM con un modelo climático regional de Israel reducido. SWAT predice una disminución del 23% en la recarga para 2051-2070 en relación con 1981-2001. En cambio, el PIM muestra una disminución del 9%, posiblemente debido a la representación de la infiltración a través de vías de flujo preferenciales y a la exclusión de los procesos de escorrentía superficial. Estas proyecciones divergentes subrayan diferencias metodológicas clave en la representación de los procesos hidrológicos. No obstante, ambos métodos proporcionaron efectivamente buenas estimaciones de la recarga de las aguas subterráneas. Las tasas de recarga estimadas a partir de los distintos métodos se integraron en MODFLOW para evaluar sus efectos relativos en la dinámica de almacenamiento de las aguas subterráneas. El conjunto de resultados del almacenamiento de aguas subterráneas proyectado por MODFLOW puede servir de orientación para una gestión sostenible de las aguas subterráneas en la región.
摘要 岩溶含水层由于与地表的相对高度连接，特别容易受到人类活动和气候变化的影响。本研究利用基于事件的补给计算方法集合，针对位于以色列和西岸的地中海岩溶含水层——西部山脉含水层（WMA）的结构不确定性问题进行了研究。通过土壤和水评估工具（SWAT）以及基于过程的入渗模型（PIM）得出的空间分布补给估计值与现场特定的经验回归模型进行了比较。SWAT和PIM的平均年补给估计值在降水的32-34.6%之间，几乎等同于经验回归模型的结果（32-36%）。未来在气候变化影响下的补给预测是通过将SWAT和PIM方法参数化，使用以色列的降尺度区域气候模型来量化的。SWAT预测到2051-2070年相对于1981-2001年补给量将减少23%。相反，PIM显示减少9%，这可能是由于模型中优先流路径的渗透表示以及排除了地表径流过程。这些不同的预测突出了水文过程表示中的关键方法差异。尽管如此，两种方法都有效地提供了良好的地下水补给估计。从各种方法估计的补给率被整合到MODFLOW中，以评估它们对地下水储存动态的相对影响。MODFLOW集合预测的地下水储存输出可以为该地区的可持续地下水管理提供指导。
Resumo Os aquíferos cársticos podem ser particularmente vulneráveis às atividades humanas e às mudanças climáticas devido ao seu grau relativamente alto de conexão com a superfície. Este estudo utilizou um conjunto de métodos de cálculo de recarga baseados em eventos para abordar o problema da incerteza estrutural para o exemplo do Aquífero Western Mountain (AWM), um aquífero cárstico mediterrâneo localizado em Israel e na Cisjordânia. Estimativas de recarga distribuídas espacialmente derivadas do Soil and Water Assessment Tool (SWAT) e do modelo de infiltração baseado em processos (MIBP) foram comparadas a modelos de regressão empírica específicos do local. As estimativas de recarga anual média do SWAT e do MIBP variaram de 32 a 34.6% da precipitação, quase igualando os resultados dos modelos de regressão empírica (32 a 36%). As previsões de recarga futura sob a influência da mudança climática foram quantificadas por meio da parametrização dos métodos SWAT e MIBP com um modelo climático regional de Israel em escala reduzida. O SWAT prevê uma redução de 23% na recarga até 2051-2070 em relação a 1981-2001. Em contraste, o MIBP mostra uma redução de 9%, possivelmente devido à representação da infiltração por meio de caminhos de fluxo preferenciais e à exclusão dos processos de escoamento superficial. Essas projeções divergentes destacam as principais diferenças metodológicas na representação dos processos hidrológicos. No entanto, ambos os métodos forneceram boas estimativas da recarga de águas subterrâneas. As taxas de recarga estimadas pelos vários métodos foram integradas ao MODFLOW para avaliar seus impactos relativos na dinâmica de armazenamento de águas subterrâneas. O conjunto de resultados de armazenamento de águas subterrâneas projetados pelo MODFLOW pode fornecer orientação para o gerenciamento sustentável das águas subterrâneas na região.
We propose a novel method to measure the specific capillary-associated interfacial area (awn) between non-wetting and wetting fluids by applying kinetic interface-sensitive (KIS) tracers under ...steady-state two-phase co-flow conditions. Seven column experiments were conducted with a column filled with glass beads (diameter d50 = 170 μm), serving as the solid grain network of a porous granular material. The experiments were performed for two flow scenarios, i.e., five experiments were performed for drainage conditions (increasing non-wetting saturation) and two experiments for imbibition conditions (increasing wetting saturation). To obtain different saturation levels in the column and, consequently, different capillarity-induced interfacial areas between the fluids, the experiments were performed for different fractional flow ratios (i.e., the ratio between injection rate of the wetting phase and total injection rate). The concentrations of the KIS tracer reaction by-product were recorded at each saturation level and the corresponding interfacial area was calculated. As a result of the fractional flow condition a wide range of wetting phase saturation is created (0.3 < Sw < 0.8). The measured awn increases with decreasing wetting phase saturation for the range 0.55 < Sw < 0.8, and then is followed by a drop in wetting phase saturation of 0.3 < Sw < 0.55. A good fit for our calculated awn is obtained (RMSE <0.16) using a polynomial model. Additionally, the results of the proposed method are compared to published experimental data and the method's main advantages and limitations are discussed.
•A new method to assess the fluid-fluid interfacial area is employed by using the Kinetic Interface-Sensitive (KIS) tracer.•The measured interfacial area with the KIS tracer is consistent with data from studies using X-ray CMT.•The obtained awn – Sw relation matches a previous polynomial model, with a highest value at Sw = 0.55.
A novel reactive smart tracer method, termed the kinetic interface-sensitive (KIS) tracer test, has been demonstrated in laboratory column experiments to enable measurement of the specific ...capillary-associated fluid–fluid interfacial area in dynamic two-phase flow displacement processes in porous media. Development of the tracer method towards effective application in real field conditions requires investigation of the influence of the porous media heterogeneity on the front size and the specific interfacial area, and, consequently, in how far a kinetic interface-sensitive tracer experiment, and the corresponding breakthrough curves, are affected. This study employs a two-dimensional Darcy-scale two-phase flow reactive transport model to investigate numerically the KIS tracer transport in heterogeneous porous media. Simulations were carried out for the primary drainage process in a domain formed of fine and coarse porous media. Various heterogeneity patterns, having different numbers of inclusions and different geometrical distributions, were studied. It is shown that the shape of the breakthrough curves can be used as an indicator for quantifying the displacement front roughness, the specific interfacial area in the domain, and the domain heterogeneity, e.g., the existence of preferential flow pathways inside the porous media. The results indicate that when the displacement front roughness is small, the concentration breakthrough curves exhibit a linear increase. The slopes of the breakthrough curves linearly depend on the fraction of the bulk volume occupied by the low-permeability sand inclusions. The volume-averaged specific interfacial area and the size of the transition zone can be determined from the slopes of the breakthrough curves.
Abstract
A novel reactive smart tracer method, termed the kinetic interface-sensitive (KIS) tracer test, has been demonstrated in laboratory column experiments to enable measurement of the specific ...capillary-associated fluid–fluid interfacial area in dynamic two-phase flow displacement processes in porous media. Development of the tracer method towards effective application in real field conditions requires investigation of the influence of the porous media heterogeneity on the front size and the specific interfacial area, and, consequently, in how far a kinetic interface-sensitive tracer experiment, and the corresponding breakthrough curves, are affected. This study employs a two-dimensional Darcy-scale two-phase flow reactive transport model to investigate numerically the KIS tracer transport in heterogeneous porous media. Simulations were carried out for the primary drainage process in a domain formed of fine and coarse porous media. Various heterogeneity patterns, having different numbers of inclusions and different geometrical distributions, were studied. It is shown that the shape of the breakthrough curves can be used as an indicator for quantifying the displacement front roughness, the specific interfacial area in the domain, and the domain heterogeneity, e.g., the existence of preferential flow pathways inside the porous media. The results indicate that when the displacement front roughness is small, the concentration breakthrough curves exhibit a linear increase. The slopes of the breakthrough curves linearly depend on the fraction of the bulk volume occupied by the low-permeability sand inclusions. The volume-averaged specific interfacial area and the size of the transition zone can be determined from the slopes of the breakthrough curves.
Résumé
Une nouvelle méthode de traceur réactif intelligent, appelée essai de traçage sensible à l’interface cinétique (KIS), a été démontrée dans des expériences de colonne de laboratoire pour permettre la mesure de la zone interfaciale fluide-fluide spécifique associée aux capillaires dans les processus dynamiques de déplacement de l’écoulement diphasique dans les milieux poreux. Le développement de la méthode de traçage en vue d’une application efficace dans des conditions réelles sur le terrain nécessite d’étudier l’influence de l’hétérogénéité du milieu poreux sur la taille du front et la zone interfaciale spécifique et, par conséquent, dans quelle mesure une expérience de traçage sensible à l’interface cinétique (et les courbes de restitution correspondantes) est affectée. Cette étude utilise un modèle de transport réactif à deux dimensions à l’échelle de Darcy pour étudier numériquement le transport du traceur KIS dans des milieux poreux hétérogènes. Des simulations ont été effectuées pour le processus de drainage primaire dans un domaine formé de milieux poreux fins et grossiers. Différents schémas d’hétérogénéité, avec différents nombres d’inclusions et différentes distributions géométriques, ont été étudiés. Il est démontré que la forme des courbes de restitution peut être utilisée comme indicateur pour quantifier la rugosité du front de déplacement, la zone interfaciale spécifique dans le domaine et l’hétérogénéité du domaine, c’est-à-dire l’existence de voies d’écoulement préférentielles à l’intérieur du milieu poreux. Les résultats indiquent que lorsque la rugosité du front de déplacement est faible, les courbes de percée de concentration présentent une augmentation linéaire. Les pentes des courbes de percée dépendent linéairement de la fraction du volume apparent occupée par les inclusions de sable peu perméables. La région interfaciale spécifique moyenne en volume et la taille de la zone de transition peuvent être déterminées à partir des pentes des courbes de restitution.
Resumen
Se ha demostrado en experimentos de laboratorio en columna un nuevo método de trazador reactivo inteligente, denominado ensayo de trazador cinético sensible a la interfase (KIS), que permite medir el área interfacial específica fluido-fluido asociada a capilares en procesos dinámicos de desplazamiento de flujo bifásico en medios porosos. El desarrollo del método del trazador hacia una aplicación efectiva en condiciones reales de campo requiere la investigación de la influencia de la heterogeneidad del medio poroso sobre el tamaño del frente y el área interfacial específica y, en consecuencia, en qué medida se ve afectado un experimento cinético de trazador sensible a la interfase (y las correspondientes curvas de ruptura). Este estudio emplea un modelo bidimensional de transporte reactivo de flujo bifásico a escala de Darcy para investigar numéricamente el transporte del trazador KIS en medios porosos heterogéneos. Se realizaron simulaciones para el proceso de drenaje primario en un dominio formado por medios porosos finos y gruesos. Se estudiaron varios patrones de heterogeneidad, con diferentes números de inclusiones y diferentes distribuciones geométricas. Se demuestra que la forma de las curvas de ruptura puede utilizarse como indicador para cuantificar la rugosidad del frente de desplazamiento, el área interfacial específica en el dominio y la heterogeneidad del dominio, por ejemplo, la existencia de vías de flujo preferenciales en el interior de los medios porosos. Los resultados indican que cuando la rugosidad del frente de desplazamiento es pequeña, las curvas de avance de la concentración muestran un aumento lineal. Las pendientes de las curvas de penetración dependen linealmente de la fracción del volumen ocupado por las inclusiones de arena de baja permeabilidad. El área interfacial específica promediada por volumen y el tamaño de la zona de transición pueden determinarse a partir de las pendientes de las curvas de penetración.
摘要
一种新型的反应性智能示踪方法，称为动力学界面敏感(KIS)示踪试验，在实验室柱实验中已被证明可以测量多孔介质中动态两相流位于毛细管之间的特定液-液界面积。将示踪方法有效应用于实际现场条件，需要研究多孔介质非均质性对锋面尺寸和单位界面面积的影响，以及相应的动力学界面敏感示踪试验(和相应的穿透曲线)的影响程度。本研究采用二维达西尺度两相流反应传输模型，在非均质性多孔介质中进行数值研究动力学界面敏感示踪剂的传输。模拟了细和粗多孔介质组成的主要排水过程。研究了各种非均质性模式，包括不同数量的组成和不同的几何分布。结果表明，穿透曲线的形状可以用作量化位移前缘粗糙度、领域内单位界面面积以及场的非均质性(例如多孔介质内部的优势流路径)的指标。结果表明，当位移前缘粗糙度很小时，浓度穿透曲线呈线性增长。穿透曲线的斜率线性依赖于低渗透率砂岩组分占据的体积分数。从穿透曲线的斜率可以确定体积平均单位界面面积和过渡区域的大小。
Resumo
Um novo método de rastreador inteligente reativo, denominado teste de rastreador sensível à interface cinética (KIS), foi demonstrado em experimentos de coluna de laboratório para permitir a medição da área interfacial fluido-fluido associada a capilares específicos em processos dinâmicos de deslocamento de fluxo bifásico em meios porosos. O desenvolvimento do método de traçador para uma aplicação efetiva em condições reais de campo requer a investigação da influência da heterogeneidade do meio poroso no tamanho da frente e na área interfacial específica e, consequentemente, até que ponto um experimento de traçador sensível à interface cinética (e o correspondente curvas de determinação) são afetados. Este estudo emprega um modelo bidimensional de transporte reativo de fluxo bifásico em escala de Darcy para investigar numericamente o transporte de traçadores KIS em meios porosos heterogêneos. Simulações foram realizadas para o processo de drenagem primária em um domínio formado por meios porosos finos e grossos. Vários padrões de heterogeneidade, com diferentes números de inclusões e diferentes distribuições geométricas, foram estudados. É mostrado que a forma das curvas de determinação pode ser usada como um indicador para quantificar a rugosidade da frente de deslocamento, a área interfacial específica no domínio e a heterogeneidade do domínio, por exemplo, a existência de caminhos de fluxo preferenciais dentro do meio poroso. Os resultados indicam que quando a rugosidade da frente de deslocamento é pequena, as curvas de determinação da concentração apresentam um aumento linear. As inclinações das curvas de determinação dependem linearmente da fração do volume total ocupada pelas inclusões de areia de baixa permeabilidade. A área interfacial específica com média de volume e o tamanho da zona de transição podem ser determinados a partir das inclinações das curvas de determinação.
The characterization of the karst conduit network is an essential task to understand the complex flow system within karst aquifers. However, this task is challenging and often associated with ...uncertainty. Equivalent porous media approaches for modeling flow in karst aquifers fall short of capturing the hydraulic effect of individual karst features, while process‐oriented karst evolution models imply major computational efforts. In this study, we apply the Stochastic Karst Simulator (SKS) developed by Borghi et al. (2012) to generate karst conduit networks at a regional scale of a highly karstified carbonate aquifer located in the Eastern Mediterranean region and extensively used for water supply. The SKS generates conduit network geometries reasonably quick, using a mathematical proxy that mimics conduit evolution. The conduit simulation is based on a conceptual model of the genesis of the aquifer, consisting of different karstification phases. The stochastic approach of the algorithm enables us to generate an ensemble of conduit network realizations and to represent the uncertainties of these simulations in a Karst Probability Map. With only soft input information to constrain conduit evolution, multiple equivalent realizations yield similar resulting network geometries, indicating a robust approach. The presented methodology is numerically efficient, and its input can be easily adjusted. Subsequently, the resulting stochastic spatial distribution of conductivities can be employed for the parametrization of regional karst groundwater models.
Key Points
We statistically generate multiple sets of karst conduit network geometries using input data based on soft information
The resulting Karst Probability Map accounts for uncertainty in the spatial distribution of the karst conduit network
Our approach can assist in the integration of soft information into the parametrization of karst groundwater models
Knowledge of soil moisture dynamics in the unsaturated soil zone provides valuable information on the temporal and spatial variability of groundwater recharge. This is especially true for the ...Mediterranean region, where a substantial fraction of long-term groundwater recharge is expected to occur during high magnitude precipitation events of above-average wet winters. To elucidate process understanding of infiltration processes during these extreme events, a monitoring network of precipitation gauges, meteorological stations, and soil moisture plots was installed in an area with a steep climatic gradient in the Jordan Valley region. In three soil moisture plots, Hydrus-1D was used to simulate water movement in the unsaturated soil zone with soil hydraulic parameters estimated by the Shuffled Complex Evolution Metropolis algorithm. To generalize our results, we modified soil depth and rainfall input to simulate the effect of the pronounced climatic gradient and soil depth variability on percolation fluxes and applied the calibrated model to a time series with 62 years of meteorological data. Soil moisture measurements showed a pronounced seasonality and suggested rapid infiltration during heavy rainstorms. Hydrus-1D successfully simulated short and long-term soil moisture patterns, with the majority of simulated deep percolation occurring during a few intensive rainfall events. Temperature drops in a nearby groundwater well were observed synchronously with simulated percolation pulses, indicating rapid groundwater recharge mechanisms. The 62-year model run yielded annual percolation fluxes of up to 66% of precipitation depths during wet years and of 0% during dry years. Furthermore, a dependence of recharge on the temporal rainfall distribution could be shown. Strong correlations between depth of recharge and soil depth were also observed.
Due to the duality in terms of (1) the groundwater flow field and (2) the discharge conditions, flow patterns of karst aquifer systems are complex. Estimated aquifer parameters may differ by several ...orders of magnitude from local (borehole) to regional (catchment) scale because of the large contrast in hydraulic parameters between matrix and conduit, their heterogeneity and anisotropy. One approach to deal with the scale effect problem in the estimation of hydraulic parameters of karst aquifers is the application of large‐scale experiments such as long‐term high‐ion conduit pumping tests, stimulating measurable groundwater drawdown in both, the karst conduit system as well as the fractured matrix. The numerical discrete conduit‐continuum modeling approach MODFLOW‐2005 Conduit Flow Process Mode 1 (CFPM1) is employed to simulate laminar and nonlaminar conduit flow, induced by large‐scale experiments, in combination with Darcian matrix flow. Effects of large‐scale experiments were simulated for idealized settings. Subsequently, diagnostic plots and analyses of different fluxes are applied to interpret differences in the simulated conduit drawdown and general flow patterns. The main focus is set on the question to which extent different conduit flow regimes will affect the drawdown in conduit and matrix depending on the hydraulic properties of the conduit system, i.e., conduit diameter and relative roughness. In this context, CFPM1 is applied to investigate the importance of considering turbulent conditions for the simulation of karst conduit flow. This work quantifies the relative error that results from assuming laminar conduit flow for the interpretation of a synthetic large‐scale pumping test in karst.
Key Points
Flow simulation of karst systems with slightly enlarged flow features demands information about conduit flow conditions
For mature karst systems laminar conduit flow equations might be applicable even for fully turbulent conditions
Conduit roughness should be considered as a lumped parameter reflecting wall roughness as well as geometrical conduit properties
We present our new multiscale pairwise‐force smoothed particle hydrodynamics (PF‐SPH) model for the characterization of flow in fractured porous media. The fully coupled multiscale PF‐SPH model is ...able to simulate flow dynamics in a porous and permeable matrix and in adjacent fractures. Porous medium flow is governed by the volume‐effective Richards equation, while the flow in fractures is governed by the Navier‐Stokes equation. Flow from a fracture to the porous matrix is modeled by an efficient particle removal algorithm and a virtual water redistribution formulation to enforce mass and momentum conservation. The model is validated by (1) comparison to a finite‐element model (FEM) COMSOL for Richards‐based flow dynamics in a partially saturated medium and (2) laboratory experiments to cover more complex cases of free‐surface flow dynamics and imbibition into the porous matrix. For the laboratory experiments, Seeberger sandstone is used because of its well‐known homogeneous pore space properties. The saturated hydraulic conductivity of the permeable matrix is estimated from a pore size and grain size distribution analysis. The developed PF‐SPH model shows good correlation with the COMSOL model and all types of laboratory experiments. We employ the proposed model to study preferential flow dynamics for different infiltration rates. Here, flow in the fracture is associated with the term “preferential flow,” providing rapid water transmission, while flow within the adjacent porous matrix enables only slow and diffuse water transmission. Depending on the infiltration rate and water inlet location, two cases can be distinguished: (1) immediate preferential/fracture flow or (2) delayed preferential flow. In the latter case, water accumulates at the surface first (ponding), then the fracture rapidly transmits water to the bottom system outlet. For the immediate fracture flow response, ponding only occurs once the fracture is fully saturated with water. In all cases, preferential flow is much more rapid than diffuse flow even under saturated porous medium conditions. Furthermore, infiltration dynamics in rough fractures adjacent to an impermeable or permeable matrix for different infiltration rates are studied as well. The simulation results show a significant lag in arrival times for small infiltration rates when a permeable porous matrix is employed, rather than an impermeable one. For higher infiltration rates, water rapidly flows through the fracture to the system outlet without any significant delay in arrival times even in the presence of the permeable matrix. The analysis of the amount of water stored in permeable fracture walls and in a fracture void space shows that for small infiltration rates, most of the injected water is retarded within the porous matrix. Flow velocity is higher for large infiltration rates, such that most of the water flows rapidly to the bottom of the fracture with very little influence of matrix imbibition processes.
Key Points
We developed a new SPH approach to study variably saturated flow in fractures adjacent to a porous matrix
We coupled the Navier‐Stokes and Richards equations to study gravity‐driven flow and matrix imbibition dynamics
We validated the model via laboratory experiments and study the effect of ponding on preferential flow dynamics in porous‐fractured media
PDF
