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A novel framework for describing suffusion in cohesionless soil, incorporating ideally gap-graded soil, is presented in this paper. The key assumption of the proposed simulation is that an erodible particle flow is induced primarily by drag force. The multiphase flow simulation for seepage-soil particle flow phenomena is conducted based on the proposed framework. The validity of the proposed method is checked through a simulation of past laboratory experiments, in which the variation in grain size distributions is grasped by a sieve analysis. The primary results show cumulative fines loss; therefore, a comparison of the cumulative fines loss is mainly discussed in this research. In addition, a discussion is given on the two different parameters affecting the erosion behavior, namely the 𝑝−𝑣𝑎𝑙𝑢𝑒 in the tortuosity function, 𝑇(∅) , and the clogging relaxation time, 𝛽𝑐𝑙𝑜𝑔 . The tortuosity is the ratio of the actual flow path and the distance between its ends, while clogging relaxation time is the parameter that considers the particle flow through the bottleneck. The results show that the numerical simulation provides a good correlation with the experiment, while the 𝑝−𝑣𝑎𝑙𝑢𝑒 is 3 which is the highest value for a geo-material. Moreover, the simulation results of the cumulative fines loss for each particle size also confirm that smaller particles will be fully eroded earlier than larger ones, and that larger particles will slowly become detached from the soil mass.

Particle‐resolved direct numerical simulations are performed to simulate the flow through particle assemblies that are either static or freely moving to demonstrate the influence of particle mobility. To obtain a comprehensive understanding for this influence essential parameters such as the Reynolds number, solids volume fraction, particle‐fluid density ratio, collision parameters and particle shape are varied. The influence of particle mobility is assessed by evaluating the particle‐fluid forces, the particle ensemble structure and particle velocities. It is found that the ability of existing correlations for static particle systems to predict drag and lift forces correctly in dynamic particle‐gas flows is limited and that drift forces perpendicular to the drag force play an important role.

Widespread adoption of redox flow batteries (RFBs) for renewable energy storage is inhibited by a relatively high cost of storage. This is due largely to typical RFBs requiring two flows, two external tanks, and expensive ion-exchange membranes. Here, we propose a potentially inexpensive Zn-Br2 RFB which is membraneless and requires only a single flow. The flow is an emulsion consisting of a continuous, Br2 -poor aqueous phase and a dispersed, Br2 -rich polybromide phase, pumped through the channel separating anode and cathode. With our prototype cell, we explore the effect of polybromide-phase volume fraction and Br2 concentration on cell performance and plating efficiencies. We demonstrate high discharge currents of up to 270 mA/cm2 , plating efficiencies up to 88 %, and dendriteless plating up to the highest Zn loading investigated of 250 mAh/cm2 . We provide mechanistic insights into cell behavior and elucidate paths towards unlocking ultra-low-cost single-flow RFBs with multiphase flow.

This work presents the implementation, verification and the validation of an incompressible Eulerian multi-fluid model for polydisperse flows. The proposed model uses a novel monolithic, i.e. implicitly coupled phase continuity equation for an arbitrary number of fluids, where the breakup source and sink terms are handled implicitly in the block-system. The implemented model is tested for an upward bubbly flow inside a large vertical pipe. The selected flow conditions exhibit both breakup and coalescence. The grid refinement study is conducted on four structured grids with varying levels of refinement. In the validation section, the numerical results are compared to the TOPFLOW experimental measurements. The last presented test examines the performance of the novel implicitly coupled phase continuity equation to the corresponding segregated formulation and the standard segregated formulation. The performance is evaluated by comparing the conservation error over the non- linear iterations. The presented model exhibits good agreement with the experimental measurements and gives stable results on various grids with different levels of refinement. Moreover, the implicit coupling reduces the conservation error during the calculation.

In fractured natural formations, the equations governing fluid flow and geomechanics are strongly coupled. Hydrodynamical properties depend on the mechanical configuration, and they are therefore difficult to accurately resolve using uncoupled methods. In recent years, significant research has focused on discretization strategies for these coupled systems, particularly in the presence of complicated fracture network geometries. In this work, we explore a finite-volume discretization for the multiphase flow equations coupled with a finite-element scheme for the mechanical equations. Fractures are treated as lower dimensional surfaces embedded in a background grid. Interactions are captured using the Embedded Discrete Fracture Model (EDFM) and the Embedded Finite Element Method (EFEM) for the flow and the mechanics, respectively. This non-conforming approach significantly alleviates meshing challenges. EDFM considers fractures as lower dimension finiten volumes which exchange fluxes with the rock matrix cells. The EFEM method provides, instead, a local enrichment of the finite-element space inside each matrix cell cut by a fracture element. Both the use of piecewise constant and piecewise linear enrichments are investigated. They are also compared to an Extended Finite Element (XFEM) approach. One key advantage of EFEM is the element-based nature of the enrichment, which reduces the geometric complexity of the implementation and leads to linear systems with advantageous properties. Synthetic numerical tests are presented to study the convergence and accuracy of the proposed method. It is also applied to a realistic scenario, involving a heterogeneous reservoir with a complex fracture distribution, to demonstrate its relevance for field applications.

Hydrate phase transition may bring hidden dangers for well control safety, even accidents of blowout happen in deep water drilling. Accurate calculation of all the drilling parameters is of great importance for well control safety. In this study, the mathematic models of transient heat transfer and multiphase flow have been established with the consideration of hydrate phase transition. Furthermore, the position where hydrate formation is most likely to occur was predicted with the proposed models, and the factors affecting hydrate formation region were also analyzed. Finally, the analysis of the effect of gas hydrate phase transition on some important parameters in well control, such as the pit gain, gas void fraction, and bottom hole pressure, is presented. The results show that hydrates form near the mud line during the drilling and shut‐in stage, but the hydrate formation region will be narrowed as well killing start. Additionally, the hydrate formation region decreased with the increase of flow rate and increased with the increasing shut‐in time, hydrate inhibitors, and riser insulation are presented to prevent hydrate blockage. More importantly, the gas void fraction and pit gain decrease due to the formation of hydrates, leading to the gas kick early detection not timely and gas kick more “hidden.”

A fast pink-beam X-ray microtomography methodology was developed at the GSECARS 13-BMD beamline at the Advanced Photon Source to study multiphase flow in porous media. The white beam X-ray distribution of the Advanced Photon Source is modified using a 1-mm copper filter and the beam is reflected off a platinum mirror angled at 1.5 mrad, resulting in a pink beam with X-ray intensities predominately in the range of 40-60 keV. Bubble formation in the wetting phase and wettability alteration of the solid phase from x-ray exposure can be a problem with high flux and high energy beams, but the suggested pink-beam configuration mitigates these effects. With a 14-second acquisition time for capturing a complete dataset, the evolving fluid-fronts of nonequilibrium three-dimensional multiphase flow can be studied in real-time and the images contain adequate image contrast and quality to measure important multiphase quantities such as contact angles and interfacial areas. LAY DESCRIPTION: Understanding how fluids are transported through porous materials is pertinent to many important societal processes in the environment (e.g. groundwater flow for drinking water) and industry (e.g. drying of industrial materials such as pulp and paper). To develop accurate models and theories of this fluid transportation, experiments need to track fluids in 3-dimensions quickly. This is difficult to do as most materials are opaque and therefore cameras cannot capture fluid movement directly. But, with the help of x-rays, scientists can track fluids in 3D using an imaging technique called x-ray microtomography (μCT). Standard μCT takes about 15 minutes for one image which can produce blurry images if fluids are flowing quickly through the material. We present a technique, fast μCT, which uses a larger spectrum of x-rays than the standard technique and acquires a 3D image in 14 seconds. With the large amount of x-rays utilized in this technique, bubbles can start to form in the fluids from x-ray exposure. We optimized the utilized x-ray spectrum to limit bubble formation while still achieving a rapid 3D image acquisition that has adequate image quality and contrast. With this technique, scientists can study fluid transport in 3D porous materials in near real-time for the improvement of models used to ensure public and environmental health.

Colloidal transport and deposition are of both environmental and engineering importance. Easier access to x-ray microtomography (XMT) coupled with improved imaging resolution has made XMT a unique and viable tool for visualizing and quantifying these processes. Currently, there is scant information in the literature addressing colloid segmentation and analysis in saturated and unsaturated porous media, in particular related to spatial partitioning of colloids. To support this need, an approach to assign segmented colloidal particles and aggregates to different partitioning classes based on their proximity to different phases is presented here. The method uses different markers for each attachment site (e.g. wetting-nonwetting phase interfaces). An example XMT dataset from a drainage experiment is used to demonstrate the efficacy of the image processing algorithms. Flow conditions, and fluid and colloid properties, can thus be compared to the behaviour of colloids within the porous medium. This algorithm can help elucidate colloidal deposition mechanisms and the importance of different attachment sites, explore the importance of fluid properties, as well as the arrangement and shape of the colloids.Chemical or biological contaminants (pollutants, bacteria etc.) may attach to soil particles, or colloids, and move throughout the environment. This leads to contamination of surface water and groundwater. Our approach to study the fate of these colloids is to use an imaging technique called x-ray microtomography (XMT), which allows us to look inside otherwise opaque materials. Thus, we can directly observe how particles move when in the presence of multiple phases (e.g. water, air, soil) with varying chemical properties and surface characteristics. After the microtomography 3D scans are collected, a challenge that remains is how to process the data to glean meaningful quantitative results. This research provides an approach for how to design an XMT study to answer colloid transport-related questions, how to process the raw data into a quantifiable format, and lastly provides an algorithm that groups colloids together based on where they are located in the porous medium. With this toolset, scientists can investigate the innerworkings of a flow experiment and directly observe and quantify attachment and detachment of colloids under varied experimental conditions. These analyses will complement traditional column transport studies, providing a deeper understanding of the fundamental transport behaviour, and ultimately providing insight in how best to protect our water resources.

Dynamic capillarity commonly exists for multiphase flow in porous media, during which fluid viscosity varies and has strong influence. Displacement experiments are conducted on water‐wet, fractured tight rock at in situ pressure and temperature of an oil reservoir via a specially designed apparatus to investigate the effects of fluid viscosity on the dynamic capillarity. The dynamic effect in the matrix is examined through the measurement and calculation of capillary pressure, the dynamic coefficient, and the fluid flow behavior. The results show that with a higher oil viscosity: (a) both the steady and the dynamic capillary pressures reverse their directions more quickly and behave as larger resistances in the matrix; (b) the difference between the steady and the dynamic capillary pressures becomes around 5%‐19% more significant; (c) water saturation changes more slowly corresponding to the lower water relative permeability, while oil relative permeability quickly becomes lower than that during the basic displacement process; and (d) the dynamic coefficient becomes 2‐3 times higher, and the dynamic contact angle becomes 10%‐25% larger, showing a more variable interface. A contact angle advancement coefficient is proposed to identify the significance of contact angle advancement and the competition between capillary pressure and viscous force. The findings of this study can help for better understanding of multiphase flow in tight reservoirs and enhancing oil recovery.

Image-based pore-scale modeling is an important method to study multiphase flow in permeable rocks. However, in many rocks, the pore size distribution is so wide that it cannot be resolved in a sin...

peer-reviewed In pseudopotential lattice Boltzmann (LB) models for simulating multicomponent flows, interaction forces between the components of a mixture lead to phase separation and interfacial tension. At the macroscopic scale, such LB models solve an advection‐diffusion equation for each component and the Navier‐Stokes equations for the fluid mixture. In this paper, the computational efficiency of the LB method is compared with a finite volume (FV) solver for the same macroscopic‐scale equations for a binary system in a two dimensional domain. The FV implementation replicates the phase separation of the LB model. Differences in the interfacial tension are due to truncation of the Taylor series expansion of the LB interaction force in the FV version. While the computations required to update the domain for each timestep can be completed faster with the FV approach, a smaller timestep is required to achieve stability, which negates the improvement in processing speed. The FV implementation, however, allows independent variation of model parameters, which is not possible in LB. For example, the viscosity can be changed without affecting interfacial tension or the extent of phase separation. Furthermore, it is possible to obtain low interfacial tensions without suppressing phase separation with the FV formulation. The significance of changing the diffusion rate of components on the deformation of a droplet in shear is also demonstrated. For three‐dimensional simulations, the finite volume approach is expected to be faster than LB and would benefit from the demonstrated flexibility in specifying model parameters.

Author(s): Iglesias, RS; Romio, C; Melo, CL; Musse, APS; do Rosario, F; Oldenburg, CM | Abstract: Controlled release of carbon dioxide (CO2) into the soil and atmosphere is performed to test detection and monitoring tools, for which several field laboratories were established by a number of institutions worldwide. Numerical simulations of CO2 behavior in the shallow subsurface region are other forms of validation and verification of the leakage pathways and destinations. These studies aim to improve monitoring and verification of CO2 in case of unexpected leakages for public assurance. In this work, we present the results of a numerical modeling study conducted to simulate the injection of CO2 as carried out during a field test in Viamao, southern Brazil, where 20nkgnday–1 of CO2 was pumped for 30 days through a vertical well 3 m below ground in an altered granitic soil. Multiphase flow simulations were performed with the TOUGH2/EOS7CA software for unsaturated porous media, using field data and injection parameters, including sensitivity tests to permeability direction, diffusivity, and boundary conditions. Results with increased horizontal permeabilities are in better agreement with the field observations. In this condition, mass balance calculations indicate approximately 90% of injected CO2 (20nkgnday–1 during 30 days) remains in the soil after 180 days from injection start, consistent with the measured flow through the soil–atmosphere interface. © 2019 Society of Chemical Industry and John Wiley a Sons, Ltd.

To investigate the flow field near fracture entrance and promote the development of sand fracturing with carbon dioxide as the working fluid, numerical simulation of multiphase flow was conducted with a 3D geological model considering the compressibility of carbon dioxide. The flow field of carbon dioxide alone was firstly investigated to lay the foundation for the analysis of multiphase flow, and then comparative analysis was conducted on the flow field of both the injecting sand from the pipe and the annulus. The results show that jet fracture with carbon dioxide can achieve a 4.46 MPa pressure boost at the fracture tip compared to the annulus pressure, which theoretically validates the feasibility of the mentioned technology. Sand fracturing can achieve a higher pressure boost in the cavity, while it needs greater pump pressure at the surface. Injecting sand from the annulus could decrease the need for pump pressure by 6.62 MPa at the condition of injecting 25% carbon dioxide from the annulus simultaneously, while the pressure difference between the cavity tip and the annulus decreases as a result.

Gas‐liquid‐liquid slug flow in a capillary reactor is a promising new concept that allows one to incorporate gas‐liquid reaction, liquid‐liquid extraction, and facile catalyst separation in a single unit. In order to assess the performance of a gas‐liquid‐liquid slug flow reactor, it is necessary to predict the slug velocity and pressure drop to ascertain residence times and reaction rates. New empirical models for velocity and pressure drop were developed based on existing models for two‐phase gas‐liquid and liquid‐liquid slug flows, and these were validated experimentally., Chem. Eng. Technol.;42(10)

BACKGROUND: Gas–liquid hydrodynamics play an important role in processes across a wide range of applications in chemical technology and biotechnology. In most of these applications, gas is bubbled in the bottom of the reactor to conduct physical mixing or mixing‐induced chemical reaction. In either case, the gas bubble hydrodynamics play a critical role on the overall performance of these processes. In the present study, the gas–liquid multiphase system is simulated using a Eulerian–Eulerian two‐fluid Computational Fluid Dynamics (CFD) model. RESULTS: The physical model is a cylindrical bubble column contactor wherein gas is sparged into liquid through a perforated sparger with a superficial gas velocity of ≈3–40 cm s⁻¹. The CFD model for the contactor is built using the free and open source tool OpenFOAM v.4.0 to simulate the gas–liquid system. The time‐averaged volume fraction distribution was studied at different heights in the column. The effect of drag force and bubble‐induced turbulence are studied to arrive at appropriate closures for the CFD model. The results obtained from the numerical simulations were validated against available experimental results found in literature. CONCLUSION: The recommended models, based on the present CFD study of the bubble column reactor, are the Ishii–Zuber drag closure with the modification that the parameter p is set to 2 for superficial gas velocities ≤20 cm s⁻¹ and is set to 4 for 40 cm s⁻¹ superficial gas velocity) and the mixed k–ϵ model to account for drag correlation and bubble‐induced turbulence closure, respectively. © 2019 Society of Chemical Industry

An experimental study of the dewatering of wood-pulp fiber suspensions by uniaxial compression is presented, to rationalize their dewatering dynamics within a two-phase framework. Twenty-seven pulp suspensions are examined, encompassing materials with different origins, preparation methodologies, and secondary treatments. For each suspension in this library, the network permeability and compressive yield stress are calibrated at low rates of dewatering. Faster compressions are then used to verify that a solid bulk viscosity is essential to match two-phase model predictions with experimental observations, and to parameterize its magnitude. By comparing the results with a suspension of nylon fibers, we demonstrate that none of the wood-pulp suspensions behave like an idealized fibrous porous medium. Nevertheless, the properties of pulp fiber networks can be reconciled within a two-phase framework, and comparisons made between different wood-pulp suspensions and between wood-pulp and nylon fibers, by appealing to potential microstructural origins of their macroscopic behavior.