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Urban water systems across the world are grappled with growing social and environmental pressures. To address these pressures, a transition from traditional water management systems towards a more integrated and sustainable approach known as “One Water” is vital. Although cities are enthusiastic about a One Water paradigm, there is a limited scholarly understanding of how to enable this transition. This study, therefore, aimed to improve intellectual comprehension of the factors that influence One Water transitions based on a series of expert interviews that were conducted with a number of utilities across North America. It was found that achieving social–environmental justice is among the most prominent drivers for utilities to start their transition, followed by concerns about climate change, water quality impairments, groundwater depletion and subsidence, and population growth. Our findings revealed that several critical barriers including a lack of regulatory frameworks and existing institutional siloes impede the transition toward One Water. Additionally, our thematic framework revealed that technological, cultural, and institutional actions are required to enable One Water transitions. However, the frequency of actions in the thematic framework sheds light on the point that cultural, institutional, and regulatory solutions are needed more than technological innovations to support the paradigm shift. Finally, our efforts identified nine key elements of a “One Water City” that could be used to characterize progress towards implementation of One Water approaches. Insights from this paper not only provide water managers with an understanding of the perspectives and actions required for enabling the One Water paradigm shift, but also can be used to develop a framework for self-assessment.

Roof runoff has the potential to serve as an important local water source in regions with growing populations and limited water supply. Given the scarcity of guidance regulating the use of roof runoff, a need exists to characterize the microbial quality of roof runoff. The objective of this 2-year research effort was to examine roof runoff microbial quality in four U.S. cities: Fort Collins, CO; Tucson, AZ; Baltimore, MD; and Miami, FL. Seven participants, i.e., homeowners and schools, were recruited in each city to collect roof runoff samples across 13 precipitation events. Sample collection was done as part of a citizen science approach. The presence and concentrations of indicator organisms and potentially human-infectious pathogens in roof runoff were determined using culture methods and digital droplet polymerase chain reaction (ddPCR), respectively. The analyzed pathogens included Salmonella spp., Campylobacter spp., Giardia duodenalis, and Cryptosporidium parvum. Several factors were evaluated to study their influence on the presence of potentially human-infectious pathogens including the physicochemical characteristics (total suspended solids, volatile suspended solids, total dissolved solids, chemical oxygen demand, and turbidity) of roof runoff, concentrations of indicator organisms, presence/absence of trees, storm properties (rainfall depth and antecedent dry period), percent of impervious cover surrounding each sampling location, seasonality, and geographical location. E. coli and enterococci were detected in 73.4% and 96.2% of the analyzed samples, respectively. Concentrations of both E. coli and enterococci ranged from0 log

There is a growing need for integrated approaches that align community priorities with strategies that build resilience to climate hazards, societal shocks, and economic crises to ensure more equitable and sustainable outcomes. We anticipate that adaptive management and resilience learning are central elements for these approaches. In this paper, we describe an approach to build and test a Resilience Learning System to support research and implementation of a resilience strategy developed for the Greater Miami and the Beaches or the Resilient305 Strategy. Elements foundational to the design of this integrated research strategy and replicable Resilience Learning System are: (1) strong partnerships among community members, government and non-government organization leaders, and researchers from multiple academic institutions; (2) contributions of subject matter expertise and local knowledge to identify information and translational gaps, formulate metrics and evaluate outcomes of Resilient305 Strategy actions from the community perspective; and (3) a comprehensive understanding of civic engagement activities, technological tools, and resilience-building capacities, including policy and financial innovations, from which to advance socio-technological, smart and connected regional-to-hyperlocal community translation through co-design/co-production. Initial results on co-produced metrics are provided. This work produces a new, replicable framework for resilience research that includes a comprehensive set of metrics, translation to communities through structured dialogues, a collaborative process involving all stakeholders and researchers, and evaluation of resilience actions to inform new investments and improve understanding and effectiveness over time.

We study ternary amphiphilic fluid flow at pore scale using a “bottom-up” Lattice Boltzmann (LB) model. The model introduces a dipole to capture the amphiphilic structure of surfactant molecules, and characterizes microscopic fluid interactions at the kinetic level. We first verify the established model by three examples, i.e., interfacial tension test, phase separation, and droplet dynamics in shear flow. The numerical results show that surfactants reduce the interfacial tension (IFT), and are able to emulsify the amphiphilic fluids, and the contours of the droplets are quantitatively in agreement with the results of level set method. Then we study the droplet dynamics in a confined environment. The surfactants make the droplet easy to deform and break up in shear flow, but inhibit coalescence due to the Marangoni stress. Moreover, there are four typical patterns for droplet collisions, i.e. coalescence, breakup after coalescence, brushing past, and brushing back. Furthermore, we improve the model by considering the wettability reversal effect caused by surfactant adsorption onto walls, and find that surfactants can decrease the critical Bond number for oil detaching from walls by 90%. Finally, we simulate the surfactant-enhanced aquifer remediation (SEAR) or enhanced oil recovery (EOR) process in a 2D porous medium. Surfactants improve the oil recovery in all wetting conditions, but the surfactant loss due to adsorption onto walls diminishes the effect of IFT reduction.

Understanding the behavior of multiple cavitation bubbles and their interactions is important for developing deeper insight into cavitation phenomena. Using a revised single-component multiphase Lattice Boltzmann method, the weak and strong interactions between two neighboring cavitation bubbles and the mutual interaction among a cluster of cavitation bubbles are simulated. The simulated bubble evolutions have satisfying agreement with previous experimental results. Details of the multiple bubble interactions (the pressure and velocity fields) are presented. In the case of two-bubble interactions, typical phenomena such as bubble toroidal deformation, micro-jets, the thinning of the liquid film, and bubble coalescence are successfully reproduced. The bubble radius changes under two-bubble weak interaction are adequately described by a revised 2-D Rayleigh-Plesset equation. The transition from the strong to weak interactions with increasing initial distance between the two bubbles is analyzed. The behaviors of a cluster of bubbles are also simulated, where the shield effect of outer layer bubbles and the micro-jets are accurately captured. The present multiphase Lattice Boltzmann method is a promising tool to investigate complex cavitation problems.

Traditional economic forecasts had consistently underestimated the hypergrowth of South Florida and its need for freshwater from the 1970s through the 1990s. It was hypothesized that the co...

We develop a semi-analytical model to calculate the entry pressure in rough capillaries based on an energy balance principle and wetting theory on rough surfaces. During the drainage process, we assume fluids form arc menisci at corners of capillary cross-sections depending on the apparent angle, and that there is a wetting phase film adsorbed on the rough surface depending on the wetting condition. A Logistic model is proposed to explain the contact angle dependence on the structure of rough surfaces. Then the capillary entry pressure is calculated by extended MS-P (Mayer, Stowe and Princen) method. We verify the model using the pseudopotential Lattice Boltzmann model and obtain good agreement between the analytical and simulated pressures. Taking capillaries with triangular sections with pillar pillar-type rough surfaces as example, we discuss how rough structures and contact angles influence capillary behaviors. The results reveal that both the wetting phase saturation and entry pressure of rough capillaries are larger than those in smooth capillaries under the same conditions. Moreover, the entry pressure is not sensitive to the roughness factor under strong wetting conditions and is much more sensitive to the pillar asperity height than the other structure parameters.

South Florida's water infrastructure and ecosystems are under pressure from socio-economic growth. Understanding the region's water resources management tradeoffs is essential for developing effective adaptation strategies to cope with emerging challenges such as climate change and sea level rise, which are expected to affect many other regions in the future. We describe a network-based hydro-economic optimization model of the system to investigate the tradeoffs, incorporating the economic value of water in urban and agricultural sectors and economic damages due to urban flooding while also accounting for water supply to sustain fragile ecosystems such as the Everglades and coastal estuaries. Results illustrate that maintaining high reliability of urban water supply under scenarios of reduced water availability (i.e., drier climate conditions) may trigger economic losses to the Everglades Agricultural Area, which will likely become more vulnerable as competition over scarce water resources increases. More pronounced economic losses are expected in urban and agricultural areas when flows to the Everglades are prioritized. Flow targets for coastal estuaries are occasionally exceeded under optimal flow allocations to various demand nodes, indicating that additional storage may be needed to maintain the environmental integrity of the estuarine ecosystems. Wetter climate conditions, on the other hand, generally lead to increased flows throughout the system with positive effects on meeting water demands, although flood mitigation efforts will necessitate additional releases to the estuaries. Strengths and limitations of the hydro-economic model are discussed.

This study estimates economic loss from South Florida croplands when usage of agricultural irrigation water is altered. In South Florida, 78% of the total value of farm products sold is comprised of cropland products. The majority of Florida citrus and sugarcane are produced in the area, and agricultural irrigation was the largest sector of water use in 2010, followed by public water supply. The Florida Department of Environmental Protection announced in December 2012 that traditional sources of fresh groundwater will have difficulty meeting all of the additional demands by 2030. A shortage of water will impose significant damage to the rural and agriculture economy in Florida, which may lead to higher prices and costs for consumers to purchase citrus or other Florida agriculture products. This paper presents a methodology for estimating economic loss when usage of irrigation water is altered, and examines economic values of irrigation water use for South Florida cropland. The efficient allocation of irrigation water across South Florida cropland is also investigated in order to reduce economic cost to the South Florida agricultural sector.

In contrast to typical applications of the pseudopotential Lattice Boltzmann model to two components, quantitative validations and applications for three-component Shan-Chen model are performed here. First, the qualitative and quantitative validations for the following three cases were performed, i.e., three-phase separation, meniscus-induced bubble movement, and the three-phase layered flow. A scheme to control the simulated contact angle of droplets on the interface is provided for the three fluid phase Lattice Boltzmann model. The effects of droplet shape, the strength of gravity, droplet size, and meniscus curvature for the spontaneous motion of droplets and bubbles are investigated in detail. It is found that without gravity, droplets tend to move to the wall on a concave upwards meniscus when they have a big “head” and a small “belly”. Gravity may enhance rather than inhibit the motion towards the wall when the density of the droplet or bubble is relatively small. Finally, smaller droplet size and larger meniscus curvatures enhance the spontaneous movement towards a wall. The conclusions are relevant to practical applications such as water treatment, oil spill remediation, and droplet-based microfluidics.

Climate change poses uncertain, complex, and emerging risks to local governments across the country, particularly in regions prone to flood and storm hazards. While local governments recognize the ...

High nighttime urban air temperatures increase health risks and economic vulnerability of people globally. While recent studies have highlighted nighttime heat mitigation effects of urban vegetation, the magnitude and variability of vegetation-derived urban nighttime cooling differs greatly among cities. We hypothesize that urban vegetation-derived nighttime air cooling is driven by vegetation density whose effect is regulated by aridity through increasing transpiration. We test this hypothesis by deploying microclimate sensors across eight United States cities and investigating relationships of nighttime air temperature and urban vegetation throughout a summer season. Urban vegetation decreased nighttime air temperature in all cities. Vegetation cooling magnitudes increased as a function of aridity, resulting in the lowest cooling magnitude of 1.4 °C in the most humid city, Miami, FL, and 5.6 °C in the most arid city, Las Vegas, NV. Consistent with the differences among cities, the cooling effect increased during heat waves in all cities. For cities that experience a summer monsoon, Phoenix and Tucson, AZ, the cooling magnitude was larger during the more arid pre-monsoon season than during the more humid monsoon period. Our results place the large differences among previous measurements of vegetation nighttime urban cooling into a coherent physiological framework dependent on plant transpiration. This work informs urban heat risk planning by providing a framework for using urban vegetation as an environmental justice tool and can help identify where and when urban vegetation has the largest effect on mitigating nighttime temperatures.

This article describes the simulation of three-dimensional buoyancy-driven bubble rise using a phase-field-based incompressible Lattice Boltzmann model. The effect of the Cahn–Hilliard mobility parameter, which is the rate of diffusion relaxation from non-equilibrium toward equilibrium state of chemical potential, is evaluated in detail. In contrast with previous work that pursues a high density ratio of binary fluids in the hydrodynamic equation, we apply a large dynamic viscosity ratio, together with a matched density pair and a separate compensating gas phase buoyant force, and the numerical results fit previous experimental results well. Through analysis, it is noted that for cases with moderate Reynolds number, a large value of mobility keeps a relatively sharp interface, while smaller values of mobility would result in diffusive interfacial regions. Moreover, for cases with large Reynolds number, small bubbles at the tail tend to separate more easily when the value of mobility is larger. This article offers some potentially useful details for performing phase-field-based simulations.

We study the flow behaviors of emulsion droplets in constricted capillaries using a surfactant Lattice Boltzmann model. We first establish the model by introducing a surfactant component into the pseudopotential multiphase model and characterizing the amphiphilic structure using dipoles. Then we study the flow of emulsion droplets in single or parallel capillaries. The simulations show that single droplet can pass through single throat in three ways, i.e., passing directly, passing with deformation, and snap-off. Multiple droplets may flow through the capillary with coalescence, and can also block the throat by adsorption or bridging, which may induce upstream flow caused by buoyancy. There is a “trap effect” when emulsions flow through parallel throats, and the droplet could be pinched off by obstacles, while the surfactants can inhibit the droplet breakup due to Marangoni effect. The simulations present detailed flow behaviors at pore scale and provide new insights for emulsion flow modeling.

In the oil development process, an immiscible third-phase slug can be injected to the formation temporarily to assist the water flooding, resulting in a three-phase flow underground. In this work, we study slug-assisted water flooding at the pore scale using the three-phase pseudopotential lattice Boltzmann model. We first briefly describe the three-phase pseudopotential model and propose a concise scheme to set the contact angles of the Janus droplet on the solid wall. Then, we simulate the slug-assisted water flooding process in different porous media structures, i.e., a single pore-throat channel, parallel throats, and a heterogeneous porous medium. The simulation results show that oil recovery can be improved effectively with the addition of the third-phase slug. The addition of the third phase results in much more interfacial interaction between different phases, which helps recover trapped oil in pore corners, narrow throats, and the high permeability zone in the porous medium. Moreover, the injection volume, injection timing, contact angle, and viscosity of the third phase influence the oil recovery in different ways. The injected slug can also be trapped in the porous medium, which may result in formation damage. The study explains the enhanced oil recovery mechanisms of slug-assisted water flooding at the pore scale and provides an effective way to design the injection scheme during industrial production.

Using a hybrid thermal Lattice Boltzmann method, the dynamics of laser-produced single cavitation bubbles in bulk liquid and the bubble collapse process near a solid boundary are numerically investigated. The simulated bubble evolutions satisfyingly agree with the theoretical calculations and the previous experimental results. The simulated bubble radius changes in bulk liquid are in good accordance with the calculations of a revised 2-D Rayleigh–Plesset equation that incorporates an extra thermal effect term. The maximum bubble radius is linearly proportional to the bubble collapse time and the input laser energy, which is consistent with the experimental data and bubble dynamics theory. Processes of a single cavitation bubble collapse at various distances from a solid boundary are analyzed in detail. The velocity vectors, density, pressure, and temperature fields are presented. The retarding effect of a solid boundary is successfully reproduced in the LBM simulations and leads to bubble elongation, the formation of micro-jet, bubble toroidal deformation, and the attraction of the bubble to the boundary during the collapse phase. The attraction effect, maximum jet velocity, and maximum pressure at the solid boundary all increase with reduced non-dimensional distance. A critical non-dimensional distance of 2.2 is validated by both the simulation and experiment. The hybrid thermal Lattice Boltzmann method is a reliable tool to investigate non-isothermal cavitation bubble dynamics.

Interdisciplinary research is increasingly called upon to find solutions to complex sustainability problems, yet co-creating usable knowledge can be challenging. This article offers broad lessons for conducting interdisciplinary science from the South Florida Water, Sustainability, and Climate Project (SFWSC), a 5-year project funded by the U.S. National Science Foundation (NSF). The goal was to develop a holistic decision-making framework to improve understanding of the complex natural–social system of South Florida water allocation and its threats from climate change, including sea level rise, using a water resources optimization model as an integration mechanism. The SFWSC project faced several challenges, including uncertainty with tasks, high task interdependence, and ensuring communication among geographically dispersed members. Our hypothesis was that adaptive techniques would help overcome these challenges and maintain scientific rigor as research evolved. By systematically evaluating the interdisciplinary management approach throughout the project, we learned that integration can be supported by a three-pronged approach: (1) Build a well-defined team and leadership structure for collaboration across geographic distance and disciplines, ensuring adequate coordination funding, encouraging cross-pollination, and allowing team structure to adapt; (2) intentionally design a process and structure for facilitating collaboration, creating mechanisms for routine analysis, and incorporating collaboration tools that foster communication; and (3) support integration within the scientific framework, by using a shared research output, and encouraging team members to adapt when facing unanticipated constraints. These lessons contribute to the international body of knowledge on interdisciplinary research and can assist teams attempting to develop sustainable solutions in complex natural–social systems.

This work serves as an important extension of previous work on cavitation simulation [Sukop and Or, Phys. Rev. E 71, 046703 (2005)10.1103/PhysRevE.71.046703]. A modified Shan-Chen single-component multiphase lattice Boltzmann method is used to simulate two different heterogeneous cavitation nucleation mechanisms, the free gas bubble model and the crevice nucleation model. Improvements include the use of a real-gas equation of state, a redefined effective mass function, and the exact difference method forcing scheme. As a result, much larger density ratios, better thermodynamic consistency, and improved numerical accuracy are achieved. In addition, the crevice nucleation model is numerically investigated using the lattice Boltzmann method. The simulations show excellent qualitative and quantitative agreement with the heterogeneous nucleation theories.

The simulation of flow in porous and fibrous permeable media is of high importance in many scientific and industrial applications. Although the finite element models at the representative elementary volume scales are used to solve a huge amount of scientific and engineering problems, they are hardly used to efficiently simulate pore-fluid flow problems at the particle scales. This encourages the development of numerical models to match the needs of such studies. In this paper, we propose a new Gray Lattice Boltzmann numerical model for simulating fluid flow in permeable media. Unlike most previous models, our proposed model has the ability to simulate multi-layers and space-variable permeability while preserving the continuity of the macroscopic velocity field. The model is verified with the available analytical solutions and a derived analytical expression for the case of variable porosity. In addition, we examine the importance of introducing a transition layer with a defined porosity function near the boundaries and interfaces. If this layer exists in practice, then the numerical results reveal that it cannot be neglected, and its impact is significant on the obtained velocity distribution. Finally, in the light of the obtained results, we can state that the proposed model has great potential to simulate complex and heterogeneous media with smoothness and accuracy, so that it may enrich the research content of the emerging computational geosciences.

Quantification of the character and spatial distribution of porosity in carbonate aquifers is important as input into computer models used in the calculation of intrinsic permeability and for next-generation, high-resolution groundwater flow simulations. Digital, optical, borehole-wall image data from three closely spaced boreholes in the karst-carbonate Biscayne aquifer in southeastern Florida are used in geostatistical experiments to assess the capabilities of various methods to create realistic two-dimensional models of vuggy megaporosity and matrix-porosity distribution in the limestone that composes the aquifer. When the borehole image data alone were used as the model training image, multiple-point geostatistics failed to detect the known spatial autocorrelation of vuggy megaporosity and matrix porosity among the three boreholes, which were only 10 m apart. Variogram analysis and subsequent Gaussian simulation produced results that showed a realistic conceptualization of horizontal continuity of strata dominated by vuggy megaporosity and matrix porosity among the three boreholes.

article i nfo Ecosystems of Florida Everglades are highly sensitive to phosphorus loading. Future restoration efforts, which focus on restoring Everglades water flows, may pose a threat to the health of these ecosystems. To determine the fate and transport of total phosphorus and evaluate proposed Everglades restoration, a water quality model has been developed using the hydrodynamic results from the M3ENP (Mike Marsh Model of Everglades National Park) — a physically-based hydrological numerical model which uses MIKE SHE/MIKE 11 software. Using advection-dispersion with reactive transport for the model, parameters were optimized and phosphorus loading in the overland water column was modeled with good accuracy (60%). The calibrated M3ENP-AD model was then modified to include future bridge construction and canal water level changes, which have shown to increase flows into ENP. These bridge additions increased total dissolved phosphorus (TP) load downstream in Shark Slough and decreased TP load in downstream Taylor Slough. However, there was a general decrease in TP concentration and TP mass per area over the entire model domain. The M3ENP-AD model has determined the mechanisms for TP transport and quantified the impacts of ENP restoration efforts on the spatial-temporal distribution of phosphorus transport. This tool can be used to guide future Everglades restoration decisions. Published by Elsevier B.V.

This research develops an integrated methodology to determine the economic value to anglers of recreational fishery ecosystem services in Everglades National Park that could result from different water management scenarios. The study first used bio-hydrological models to link managed freshwater inflows to indicators of fishery productivity and ecosystem health, then link those models to anglers' willingness-to-pay for various attributes of the recreational fishing experience and monthly fishing effort. This approach allowed us to estimate the foregone economic benefits of failing to meet monthly freshwater delivery targets. The study found that the managed freshwater delivery to the Park had declined substantially over the years and had fallen short of management targets. This shortage in the flow resulted in the decline of biological productivity of recreational fisheries in downstream coastal areas. This decline had in turn contributed to reductions in the overall economic value of recreational ecosystem services enjoyed by anglers. The study estimated the annual value of lost recreational services at $68.81 million. The losses were greater in the months of dry season when the water shortage was higher and the number of anglers fishing also was higher than the levels in wet season. The study also developed conservative estimates of implicit price of water for recreation, which ranged from $11.88 per AF in November to $112.11 per AF in April. The annual average price was $41.54 per AF. Linking anglers' recreational preference directly to a decision variable such as water delivery is a powerful and effective way to make management decision. This methodology has relevant applications to water resource management, serving as useful decision-support metrics, as well as for policy and restoration scenario analysis.

Modeling of groundwater levels in a portion of the low-lying coastal Arch Creek basin in northern Miami-Dade County in Southeast Florida USA, which is subject to repetitive flooding, reveals that rain-induced short-term water table rises can be viewed as a primary driver of flooding events under current conditions. Areas below 0.9m North American Vertical Datum (NAVD) elevation are particularly vulnerable and areas below 1.5m NAVD are vulnerable to exceptionally large rainfall events. Long-term water table rise is evident in the groundwater data, and the rate appears to be consistent with local rates of sea level rise. Linear extrapolation of long-term observed groundwater levels to 2060 suggest roughly a doubling of the number of days when groundwater levels exceed 0.9m NAVD and a threefold increase in the number of days when levels exceed 1.5m NAVD. Projected sea level rise of 0.61m by 2060 together with increased rainfall lead to a model prediction of frequent groundwater-related flooding in areas0.9m NAVD. However, current simulations do not consider the range of rainfall events that have led to water table elevations1.5m NAVD and widespread flooding of the area in the past. Tidal fluctuations in the water table are predicted to be more pronounced within 600m of a tidally influenced water control structure that is hydrodynamically connected to Biscayne Bay. The inland influence of tidal fluctuations appears to increase with increased sea level, but the principal driver of high groundwater levels under the 2060 scenario conditions remains groundwater recharge due to rainfall events.

High-value urban zones in coastal South Florida are considered particularly vulnerable to salt water intrusion into the groundwater-based, public water supplies caused by sea level rise (SLR) in combination with the low topography, existing high water table, and permeable karst substrate. Managers in the region closely regulate water depths in the extensive South Florida canal network to control closely coupled groundwater levels and thereby reduce the risk of saltwater intrusion into the karst aquifer. Potential SLR adaptation strategies developed by local managers suggest canal and groundwater levels may have to be increased over time to prevent the increased salt water intrusion risk to groundwater resources. However, higher canal and groundwater levels cause the loss of unsaturated zone storage and lead to an increased risk of inland flooding when the recharge from rainfall exceeds the capacity of the unsaturated zone to absorb it and the water table reaches the surface. Consequently, higher canal and groundwater levels are also associated with increased risk of economic losses, especially during the annual wet seasons. To help water managers and urban planners in this region better understand this trade-off, this study models the relationships between flood insurance claims and groundwater levels in Miami-Dade County. Via regression analyses, we relate the incurred number of monthly flood claims in 16 Miami-Dade County watersheds to monthly groundwater levels over the period from 1996 to 2010. We utilize these estimated statistical relationships to further illustrate various monthly flood loss scenarios that could plausibly result, thereby providing an economic quantification of a “too much water” trade-off. Importantly, this understanding is the first of its kind in South Florida and is exceedingly useful for regional-scale hydro-economic optimization models analyzing trade-offs associated with high water levels.

[1] Lattice Boltzmann flow simulations provide a physics-based means of estimating intrinsic permeability from pore structure and accounting for inertial flow that leads to departures from Darcy's law. Simulations were used to compute intrinsic permeability where standard measurement methods may fail and to provide better understanding of departures from Darcy's law under field conditions. Simulations also investigated resolution issues. Computed tomography (CT) images were acquired at 0.8 mm interscan spacing for seven samples characterized by centimeter-scale biogenic vuggy macroporosity from the extremely transmissive sole-source carbonate karst Biscayne aquifer in southeastern Florida. Samples were as large as 0.3 m in length; 7–9 cm-scale-length subsamples were used for lattice Boltzmann computations. Macroporosity of the subsamples was as high as 81%. Matrix porosity was ignored in the simulations. Non-Darcy behavior led to a twofold reduction in apparent hydraulic conductivity as an applied hydraulic gradient increased to levels observed at regional scale within the Biscayne aquifer; larger reductions are expected under higher gradients near wells and canals. Thus, inertial flows and departures from Darcy's law may occur under field conditions. Changes in apparent hydraulic conductivity with changes in head gradient computed with the lattice Boltzmann model closely fit the Darcy-Forchheimer equation allowing estimation of the Forchheimer parameter. CT-scan resolution appeared adequate to capture intrinsic permeability; however, departures from Darcy behavior were less detectable as resolution coarsened.

The primary and key task of binary fluid flow modeling is to track the interface with good accuracy, which is usually challenging due to the sharp-interface limit and numerical dispersion. This article concentrates on further development of the conservative Allen-Cahn equation (ACE) [Geier et al., Phys. Rev. E 91, 063309 (2015)10.1103/PhysRevE.91.063309] under the framework of the lattice Boltzmann method (LBM), with incorporation of the incompressible hydrodynamic equations [Liang et al., Phys. Rev. E 89, 053320 (2014)10.1103/PhysRevE.89.053320]. Utilizing a modified equilibrium distribution function and an additional source term, this model is capable of correctly recovering the conservative ACE through the Chapman-Enskog analysis. We also simulate four phase-tracking benchmark cases, including one three-dimensional case; all show good accuracy as well as low numerical dispersion. By coupling the incompressible hydrodynamic equations, we also simulate layered Poiseuille flow and the Rayleigh-Taylor instability, illustrating satisfying performance in dealing with complex flow problems, e.g., high viscosity ratio, high density ratio, and high Reynolds number situations. The present work provides a reliable and efficient solution for binary flow modeling.

Batch and column experiments were conducted with eucalyptus mulch and commercial compost to evaluate suitability of highly organic natural media to support anaerobic decomposition of trichloroethylene (TCE) in groundwater. Experimental data for TCE and its dechlorination byproducts were analyzed with Hydrus-1D model to estimate the partitioning and kinetic parameters for the sequential dechlorination reactions during TCE decomposition. The highly organic natural media allowed development of a bioactive zone capable of decomposing TCE under anaerobic conditions. The first order TCE biodecomposition reaction rates were 0.23 and 1.2 d−1 in eucalyptus mulch and compost media, respectively. The retardation factors in the eucalyptus mulch and compost columns for TCE were 35 and 301, respectively. The results showed that natural organic soil amendments can effectively support the anaerobic bioactive zone for remediation of TCE contaminated groundwater. The natural organic media are effective environmentally sustainable materials for use in permeable reactive barriers.