Surfactant flooding is widely used in subsurface applications where high displacement efficiency is needed, such as nonaqueous phase liquid (NAPL) remediation and enhanced oil recovery (EOR). For surfactant/water/oil systems, the partitioning of surfactants in each phase is controlled by external factors, such as salinity. The third phase, microemulsions, which locates between water and oil, can be

Dual-grid models address the computational bottlenecks of large-scale (>103 km2) urban flood modeling with solution updates on a coarse grid that are informed by topographic data on a fine grid. However, dual-grid models may poorly resolve levees, leading to loss of accuracy. Here we present a grid edge classification method whereby specific edges of the coarse grid are flagged to gather nearby topographic

The contamination of groundwater aquifers by chlorinated solvents is a water-resource issue of great importance worldwide. Such contaminants are difficult to treat because they are often released as dense non-aqueous phase liquids (DNAPLs). Research shows that the application of remediation technologies to both the NAPL source and dissolved plume can lead to more efficient remediation, rather than

Coupling multiphase flow with energy transport due to high temperature heat sources introduces significant new challenges since boiling and condensation processes can lead to dry-out conditions with subsequent re-wetting. The transition between two-phase and single-phase behavior can require changes to the primary dependent variables adding discontinuities as well as extending constitutive nonlinear

Reactive transport (RT) through heterogeneous media, may cause chemical heterogeneity if water flux is slow through portions of the medium. In such cases, chemical localization (i.e., the occurrence of reactions that would not occur in well mixed media) may develop, which is especially relevant for biochemical reactions occurring in biofilms. The objective of this work is to study the conditions for

Solute transport through radial advection–dispersion is a common phenomenon in many applications, such as aquifer decontamination, heat exchange for geothermal exploration, and tracer testing. Numerous analytical solutions to the problem of tracer testing in a radially divergent flow field are available for fitting breakthrough curves. However, all of these analytical solutions assume non-uniform flow

Coastal forcing including waves lead to complex and dynamic mixing between discharging groundwater and recirculating coastal water in permeable unconfined nearshore aquifers. This mixing can drive biogeochemical transformations that affect the fate of pollutants in nearshore aquifers and their ultimate discharge to coastal waters. The objective of this study was to examine the effect of time-varying

This study presents a generic data-driven reservoir operation model (GDROM). The hidden Markov-decision tree (HM-DT) is applied to deriving representative operation modules for a reservoir; a classification and regression tree (CART) algorithm is used to identify the application and transition conditions for the operation modules. These two procedures result in the GDROM that is featured by 1) using

Time-lapse electrical resistivity tomography (ERT) is a popular geophysical method to estimate three-dimensional (3D) permeability fields from electrical potential difference measurements. Traditional inversion and data assimilation methods are used to ingest this ERT data into hydrogeophysical models to estimate permeability. Due to ill-posedness and the curse of dimensionality, existing inversion

Flow and multicomponent reactive transport in saturated/unsaturated porous media are modeled by ensembles of computational particles moving on regular lattices according to specific random walk rules. The occupation number of the lattice sites is updated with a global random walk (GRW) procedure which spreads the particles from a lattice site with computational costs comparable to those for a single

Correlated velocity models (CVMs) have proven themselves to be effective tools for describing a wide range of solute transport behaviors in heterogeneous porous media. In particular, spatial Markov models (SMMs) are a class of CVMs where subsequent Lagrangian velocities along transport trajectories depend only on the current velocity, and not on past history. Such models provide a powerful tool for

Groundwater contamination causes significant groundwater supply risks that severely affect humans and livestock, especially in the era of climate change. Consequently, the need to develop and optimize remediation strategies such as pump and treat is indispensable. An effective and efficient strategy can reduce the spread of contaminants and cost of clean-up. However, developing such a strategy is challenging

Shallow bedrock aquifers are prevalent across the Northern Hemisphere and can be the primary source of freshwater for many communities. Cryospheric impacts from climate warming are particularly concerning for bedrock aquifers where recharge is dominated by winter precipitation. For the management and protection of fractured rock groundwater supplies, the processes influencing infiltration and recharge

To solve the time-consuming parameter inversion problem based on swarm evolution algorithm, this study proposes an improved greedy sampling method (GSM) (IGSM) based on model reduction technology to rapidly estimate the hydraulic conductivity of steady-state seepage problem. Different from the traditional GSM, IGSM neither needs to estimate the posterior error bound of the reduced-order model (ROM)

Persistent surface water pools within non-perennial streams provide critical refuges for freshwater species by facilitating their survival during extended dry periods. However, our understanding of how pool water levels recede is limited, hindering our ability to quantify and predict aquatic refuge persistence. We characterise variations in water-level recession rates based on one year of water-level

Scaling up highly heterogeneous aperture distributions of fractures into equivalent permeability tensors enables a substantial reduction in the computational cost of simulating fluid flow in fractured porous media by allowing the employment of coarser grids while keeping the accuracy of an explicit model. This work proposes the adaptation and application of conditional generative adversarial networks

A fully mixed finite element (MFE) model is developed for nonlinear flow and transport in unsaturated fractured porous media with matrix-fracture and fracture-fracture fluid and mass exchanges. The model is based on the discrete fracture matrix (DFM) approach and assumes cross-flow equilibrium in the fractures. The MFE method is employed for the spatial discretization of both flow and transport on

Salt marshes and mangrove forests provide critical ecosystem services such as reduced sediment erosion and increased hydrodynamic buffering. Sediment transport and hydrodynamics can be influenced by specific functional traits of the plants (for example, flexibility vs. rigidity) and community traits (for example, spatial density). While there is a growing body of literature on plant trait and hydrodynamic

For strongly non-linear and high-dimensional inverse problems, Markov chain Monte Carlo (MCMC) methods may fail to properly explore the posterior probability density function (PDF) given a realistic computational budget and are generally poorly amenable to parallelization. Particle methods approximate the posterior PDF using the states and weights of a population of evolving particles and they are

This paper presents a method for constructing approximate semi-analytical solutions for the radially symmetric generalized Boussinesq equation, also known as the porous medium equation (PME). This work is a further extension of analysis done by Telyakovskiy et al. (2016), that studied water injection governed by the Boussinesq equation into an unconfined initially dry aquifer. The newly derived approximate

Two-dimensional (2D) depth-averaged shallow water equations (SWE) are widely used to model unsteady free surface flows, such as flooding processes, including those due to dam-break or levee breach. However, the basic hypothesis of small bottom slopes may be far from satisfied in certain practical circumstances, both locally at geometric singularities and even in wide portions of the floodable area

In this paper, we present a new computationally-efficient and high-resolution depth-averaged two-phase flow model for hydro-sediment-morphydynamic processes, featuring an advance over existing models in terms of accuracy and efficiency of numerical solution. Under the framework of finite volume method (FVM) on unstructured grids, the Harten-Lax-van Leer-Contact (HLLC) approximate Riemann solver is

Assuming that the equilibrium geometry of river channels does not depend on their initial state but solely on boundary conditions, several formulas have been derived that relate the channel depth and width to the river bankfull discharge and bed material. However, due to the existence of a threshold for sediment motion and the strong non-linearity between sediment transport and flow rate, this assumption

Dynamic programming (DP) is an effective method for solving multi-stage decision-making problems and has been extensively applied to the optimization of reservoir operations. However, the method is limited by the dimensionality problem; hence, it cannot be directly applied to optimizing the operations of a reservoir system with more than three reservoirs at current computing power. The progressive

The implementation of nonstationary hydrological frequency analysis (NS-HFA) has often been hampered by the relatively short datasets and the resulting high uncertainty. Most recently, the non-asymptotic Metastatistical extreme value (MEV) and simplified MEV (SMEV) distributions, which rely on the ordinary events rather than the extremes only, have attracted attention in the HFA of both rainfall and

Machine learning methods provide new perspective for more convenient and efficient prediction of groundwater flow. In this study, a deep learning method “GW-PINN” without labeled data for solving groundwater flow equations with wells was proposed. GW-PINN takes the physics inform neural network (PINN) as the backbone and uses either the hard or soft constraint in the loss function for training. A locally

Climate change is expected to have a significant impact on water security, with higher temperatures causing both enhanced droughts and flood extremes. Here, using global flow data from non-urban catchments, we investigate the sensitivity of flood volume to changes in concurrent surface air temperature. We find most of the world shows decreases in flood volumes with increasing temperature. To understand

In this paper we develop a two-dimensional modelling framework suitable to study the morphological evolution of vegetated braided rivers. The mathematical model features a unisize-sediment morphological model, which includes accounting for bank erosion, and a vegetation model. While these model components had already appeared separately in different contexts, here we improve and tailor them for modelling

We propose a novel method to predict fluid flow properties of reservoir rocks from 2D rock images by connecting pore clusters based on their intrinsic properties. Spatial proximity and connecting large clusters with priority are the two basic connecting principles of this method. A few methods from complex networks were used to analyze the topology and connectivity of the connected pore networks, resulting

The adsorption of perfluorooctane sulfonate (PFOS) on sediments is thought to be enhanced by the ‘salting-out effect’ (SOE), which reduces contaminant solubility as water salinity increases. The process of salting-out has been observed for PFOS in surface estuaries and likely operates in ‘subterranean estuaries’, where tide-induced groundwater circulation creates a dynamic saltwater-freshwater mixing

Sediment mobility and memory effects distinguish transport and morphodynamics in fine sediment settings from sandy settings. This paper focuses on the morphodynamic modeling of fine sediment systems, and an adaptation of modeling procedures more commonly used in sand-dominated systems. An extensive dataset of short-term transport and morphological trends along with ancillary data is used to support

Understanding the mechanisms of nanoconfined liquid flow in nanoporous media is crucial for many scientific and engineering applications such as enhanced shale oil recovery and water purification. However, due to molecular interactions which cause slip boundary and heterogeneous viscosity/density in nanoscale space, the conventional continuity equations are no longer applicable. Besides, the pore size

Surface wettability is one of the major factors that regulate immiscible fluid displacement in porous media. However, the role of pore-scale wettability heterogeneity on dynamic immiscible displacement is rarely investigated. This study investigated the impact of pore-scale wettability heterogeneity on immiscible two-fluid displacement and the resulting macroscopic constitutive relations, including

Foam injection is a promising option for soil remediation applications. However, predicting how it will propagate in highly permeable aquifers under groundwater flow is challenging. Here, we have studied pressure and saturation variations during foam propagation. A 2D tank packed with 1 mm glass beads was used to study foam injection in highly permeable porous media under lateral flow. Specifically

Ganglia, or bubbles, trapped by capillary forces inside porous materials occur in a wide range of subsurface and manufacturing applications. In geologic CO2 storage, ganglia are desired as they render the injected CO2 hydrodynamically immobile. But they may evolve by dissolution or mass exchange across the brine, called ripening. In fuel cells and electrolyzers, water/oxygen ganglia must be removed

In this study, we have developed a two-way fully coupled hydrodynamic-vegetation model that includes a spatially and temporally variable drag coefficient of flexible submerged aquatic vegetation (SAV). The developed model consists of a nonhydrostatic wave model (NHWAVE) that solves the Navier-Stokes equations and a numerical model for vegetation stem dynamics that solves the instantaneous forces applied

The dynamic and quasi-static spatiotemporal responses of pore water induced by fluid-mass sources in unsaturated porous media are determined and compared. An explicit fundamental solution for pore water pressure is derived using the known Green's function of dynamic poroelasticity. Based on the order of the low-frequency approximations for the source impulsive time function, different physical regimes

We present a novel approach to adaptive optimal design of groundwater surveys – a methodology for choosing the location of the next monitoring well. Our dual-weighted approach borrows ideas from Bayesian Optimisation and goal-oriented error estimation to propose the next monitoring well, given that some data is already available from existing wells. Our method is distinct from other optimal design

We present results from laboratory experiments of the downslope propagation of a finite volume released gravity current by means of combined PIV/PLIF measurements. The experimental data were used to estimate the global characteristics of the current, such as the propagation speed, the lateral surface and the buoyancy, revealing that thermal theory is a robust model that can predict such quantities

The time step of an explicit time integration scheme for solving time-dependent hyperbolic partial differential equations in a finite volume method (FVM) framework is restricted by the Courant-Friedrichs-Levy (CFL) criterion. Conventional time stepping integrates all grid cells with the same time step. This causes unnecessary computational costs when wave speeds and/or grid spacing vary considerably

A semi-analytical solution of the Richards Equation posed on a two-layered one-dimensional soil supplied with various boundary conditions is derived under a constraint that the constitutive relations are exponentially dependent on the pressure head. It allows for a transformation of the Richards Equation into a linear parabolic partial differential equation that governs a spatial–temporal function

Coreflooding experiments with computed tomography imaging are becoming common practice. They allow to investigate the sub-core scale properties such as relative permeability (kr) and capillary pressure (Pc), and to construct multiphase flow models that not only capture the core average flow, but also the flow on the sub-core (millimeter) scale. This work presents two-phase flow models of imbibition

Smoothed Particle Hydrodynamics (SPH) has successfully been employed in the last decade for macroscopic simulation of fluid flow in porous media. However, there are still certain inconsistencies in the existing models with regard to both the definition of the governing equations and the adopted numerical treatments. In this study, thus, in order for a comparative investigation of the existing practices

Identification of groundwater contaminant sources in a highly-heterogenous geosystems results in a high-dimensional inverse problem and is often solved based on a surrogate model to alleviate the computational burden. Surrogate modeling through deep learning has a great potential for learning complex nonlinear relationships between model inputs and outputs. Most of the developed surrogates, however

Our understanding and modelling of flow instabilities (e.g. viscous, gravitational) in the presence of geological heterogeneity is limited by a lack of experimental observations at relevant scales in consolidated media. Typically, small sample sizes (<50 mm diameter) restrict the scale of heterogeneity, and the development of unstable fingers may be damped by the sample boundaries. Furthermore, there

We use a generalized pore network model in combination with image-based experiments to understand the parameters that control upscaled flow properties. The study is focued on water-flooding through a reservoir sandstone under water-wet and mixed-wet conditions. A set of sensitivity studies is presented to quantify the role of wettability, pore geometry, initial and boundary conditions as well as a

The process of pH-dependent adsorption/desorption controls the transport of solutes in reactive porous media, the greater the adsorption the slower the solute migration. Earlier works show that in the presence of longitudinal hydrodynamic dispersion and pH-dependent adsorption, a fast solute transport phenomenon may arise. However, the effect of transverse dispersion on this fast transport phenomenon

Although global- and catchment-scale hydrological models are often shown to accurately simulate long-term runoff time-series, far less is known about their suitability for capturing hydrological extremes, such as droughts. Here we evaluated simulations of hydrological droughts from nine catchment scale hydrological models (CHMs) and eight global scale hydrological models (GHMs) for eight large catchments:

Vertical recirculation wells used for remediation or heat recovery induce drawdown distribution that varies for confined, unconfined, leaky, and reservoir-covered aquifers. A recirculation well with arbitrary arrangement of extraction and injection screen intervals is simulated with the general well function of Perina and Lee (2006) and Perina (2014) after a minor modification. Distribution of radial

Saline intrusion (SI) in coastal aquifers is a global problem with the potential to contaminate groundwater used by over a billion people. Numerical modelling of SI in coastal aquifers is a key tool for risk assessment, aquifer management and resource regulation, but is extremely challenging because the mixing zone across the saline front is often very narrow, extending over metres or 10’s metres,

Flows involving immiscible displacement of one fluid by another in a porous media are known to destabilize and form fluid fingering. When the non-wetting fluid is a highly mobile gas (air) and the wetting fluid is an in-compressible liquid (water) the classical macroscopic theory is unable to describe the fingered flow. In Part I of this study we have introduced a model that interprets the mixture

A semi-analytical method and the dual-porosity model are used to simulate matrix diffusion between parallel fractures. The semi-analytical modeling parameters can be computed directly using the fracture spacing, aperture, and matrix properties. Those parameters do not require calibration to match an analytical solution for matrix diffusion. The dual-porosity model is applied under the same conditions

Abstract not available

Temperature analysis during a pause in injection operations, known as warmback analysis, has been used in the petroleum industry for evaluating the injection conformance and estimating the location of the flooded front in applications, such as waterflooding oil reservoirs. In this work, methods are introduced to extend the application of temperature warmback analysis to estimate the zonal CO2 injection

We report the discovery of novel regimes of calcium carbonate dissolution in micron-scale confined spaces through microfluidic experiments. In the experiments, hydrochloric acid is injected into a microfluidic chamber with pre-deposited calcium carbonate solids. As the acid flow rate is decreased, the dissolution of calcium carbonate transits from a liquid/solid single-phase reactive transport regime

Large-scale models of fluid flow through fractures are almost exclusively based on Poiseuille flow (the cubic law). When the fracture aperture is time and/or spatially varying, flow is transient, and/or flow rates are modest (Re≥1), Poiseuille flow predictions can deviate substantially from the full Navier–Stokes solution and generally do not satisfy conservation of energy. A new Reduced Dimension

Quantitative descriptions of the temporal and spatial variations of volumetric water content and total water potential in unsaturated soils have for more than nine decades focused on diffusive mechanisms as represented by the Richards equation (Richards, 1931). However, recent laboratory studies (Lo et al., 2017) have revealed short-time transient behavior of water in non-deforming unsaturated soils

Solubility trapping of carbon dioxide (CO2) in deep saline aquifers is considered an effective mechanism of carbon storage. The dissolution of CO2 in aquifer brine may result in gravitational instability, which triggers convective mixing (similar to the well-known Rayleigh–Bénard convection problem). The process starts with the diffusion of CO2 into the brine, followed by the onset of convection (tc)