Recent Submissions

  • Comment on “A periodic grain consolidation model of porous media” [Phys. Fluids A 1, 38 (1989)]

    Khirevich, Siarhei; Patzek, Tadeusz (Physics of Fluids, AIP Publishing, 2019-10-11) [Article]
    In this document, we correct the friction coefficient values presented in Table III in a study by Larson and Higdon [“A periodic grain consolidation model of porous media,” Phys. Fluids A 1, 38 (1989)]. The authors addressed the problem of Stokes flow through periodic arrays of (non)overlapping spheres and determined the friction coefficients. It appears that the volume of the overlapping region of spheres was not taken into account, which affected the total solid concentration and systematically biased the corresponding friction coefficient values. We correct the sphere concentration and friction coefficients, and validate our approach with lattice-Boltzmann simulations. The suggested correction is valid in the case of overlapping spheres only, when the volume of the overlapping region is positive.
  • Generalized Extreme Value Statistics, Physical Scaling and Forecasts of Oil Production in the Bakken Shale

    Saputra, Wardana; Kirati, Wissem; Patzek, Tadeusz (Energies, MDPI AG, 2019-09-25) [Article]
    We aim to replace the current industry-standard empirical forecasts of oil production from hydrofractured horizontal wells in shales with a statistically and physically robust, accurate and precise method of matching historic well performance and predicting well production for up to two more decades. Our Bakken oil forecasting method extends the previous work on predicting fieldwide gas production in the Barnett shale and merges it with our new scaling of oil production in the Bakken. We first divide the existing 14,678 horizontal oil wells in the Bakken into 12 static samples in which reservoir quality and completion technologies are similar. For each sample, we use a purely data-driven non-parametric approach to arrive at an appropriate generalized extreme value (GEV) distribution of oil production from that sample’s dynamic well cohorts with at least 1 , 2 , 3 , ⋯ years on production. From these well cohorts, we stitch together the P50, P10, and P 90 statistical well prototypes for each sample. These statistical well prototypes are conditioned by well attrition, hydrofracture deterioration, pressure interference, well interference, progress in technology, and so forth. So far, there has been no physical scaling. Now we fit the parameters of our physical scaling model to the statistical well prototypes, and obtain a smooth extrapolation of oil production that is mechanistic, and not just a decline curve. At late times, we add radial inflow from the outside. By calculating the number of potential wells per square mile of each Bakken region (core and noncore), and scheduling future drilling programs, we stack up the extended well prototypes to obtain the plausible forecasts of oil production in the Bakken. We predict that Bakken will ultimately produce 5 billion barrels of oil from the existing wells, with the possible addition of 2 and 6 billion barrels from core and noncore areas, respectively.
  • A Non-Isolated Hybrid-Modular DC-DC Converter for DC Grids: Small-Signal Modeling and Control

    Elserougi, Ahmed; Abdelsalam, Ibrahim; Massoud, Ahmed; Ahmed, Shehab (IEEE Access, Institute of Electrical and Electronics Engineers (IEEE), 2019-09-13) [Article]
    This paper presents small-signal modeling, stability analysis, and controller design of a nonisolated bidirectional hybrid-modular DC-DC Converter for DC grid applications. The DC-DC converter can be used to interconnect two different DC voltage levels in a medium-/high-voltage DC grid. Half-bridge Sub-Modules (SMs) and a high-voltage valve are the main components of the converter. The high-voltage valve can be implemented via employing series-connected Insulated-Gate Bipolar Transistors (IGBTs). Operation with zero voltage switching of the involved high-voltage valve is feasible, i.e., there is no concern pertinent to dynamic voltage sharing among the series-connected IGBTs. The power is transferred from one side to another through the involved SMs, where their capacitors are connected in series across the high-voltage side, while they are connected sequentially across the low-voltage side. In this paper, the state-space averaging technique is employed to derive the small-signal model of the presented converter for controller design. Closed-form expression of the duty cycle-to-inductor current transfer function is extracted. Comparison between simulation results of the small-signal model and the detailed circuit model is presented to authenticate the accuracy of the derived small-signal model. Finally, a scaled-down prototype is used to verify the accuracy of the small-signal model.
  • Controlling Factors of Degassing in Crosslinked Polyethylene Insulated Cables

    Youn, Dong Joon; Li, Jingfa; Livazovic, Sara; Sun, Yabin; Sun, Shuyu (Polymers, MDPI AG, 2019-09-03) [Article]
    Here, we analyze the degassing process of a byproduct (methane) formed during the peroxide-induced crosslinking of polyethylene. A diffusion model based on Fick’s law is used to obtain the controlling factors of degassing in a crosslinked polyethylene (XLPE) insulated power cable (132 kV with 18 mm of insulation). We quantitatively analyze different scenarios of the diffusion of methane through the XLPE insulation and two semiconductor layers under various in situ degassing conditions. The analyzed degassing conditions include heat transfer and its effect on the diffusion properties, the different transport and boundary conditions due to the free spaces within the cable conductor, and the nonuniform distribution of methane concentrations within the insulation layers. Our simulation results clearly demonstrate that the free spaces between the copper strands in the cable conductor significantly affect the degassing efficiency. However, the temperature-diffusion coupling has a relatively minor effect on the overall degassing efficiency due to the rapid temperature increase of the polymer layers during the initial stages of degassing. Moreover, we find that the nonuniform distribution of methane in the initial stages also plays an important role in degassing in the cable, but this effect varies significantly during the degassing process.
  • Physical properties of fine-grained sediments with segregated hydrate lenses

    Lei, Liang; Santamarina, Carlos (Marine and Petroleum Geology, Elsevier BV, 2019-09-03) [Article]
    The physical properties of natural gas hydrate-bearing sediments are critical for the analysis of natural systems and for the design of gas production strategies. This work explores the properties of fine-grained sediments containing segregated hydrate lenses. Our analyses show that hydrate formation is grain-displacive when the product of the effective stress and the grain radius is σ′R < 2πΓhw ≈ 0.2-to-0.3 N/m, such as in shallow fine-grained sediments. The assessment of physical properties is particularly challenging in fine-grained sediments with segregated gas hydrate because (1) inherent difficulties in hydrate formation hinder laboratory studies, and (2) segregated hydrate requires large specimens and laboratory devices to avoid boundary effects and to create a representative volume for analysis. We circumvent these challenges through the use of numerical simulations. In these simulations, the properties of the hydrate-free sediment surrounding the segregated hydrate lenses take into consideration the effects of cryogenic suction and grain-displacive hydrate growth. Our results for mechanical properties and conduction show that numerical simulations must properly consider the hydrate morphology, the altered sediment properties, and the sediment-hydrate interfacial conditions (interfaces are rough, jagged and well bonded during hydrate formation, but become weak-frictional on dissociation). In fact, changes in the strength and stiffness of the hydrate-free sediment that surrounds a segregated hydrate mass can be more important on the global properties than the presence of hydrate itself. Numerical simulations highlight distinct anisotropy in mechanical properties and conduction in the presence of segregated hydrate lenses, and the tendency to shear localization when there is a weak-frictional interface. We emphasize that a relatively small fraction of fines can make sediments prone to segregated hydrate formation, therefore proper sediment classification is critical.
  • Improved CPT system with less voltage stress and sensitivity using a step-down transformer on receiving side

    Mostafa, Tarek Mahmoud Atia; Muharam, Aam; Hu, Aiguo Patrick; Hattori, Reiji (IET Power Electronics, Institution of Engineering and TechnologyJBristow@theiet.org, 2019-08-28) [Article]
    This paper proposes a capacitive power transfer (CPT) system with a step-down transformer on the secondary side to reduce the circuit quality factor (Q), and thereby reduce the sensitivity to parameters variations, as well as the voltage stress across the coupling interface. The system operating principle is analyzed mathematically, and the focus is given to understand the effect of the leakage inductance (Llk) of the non-ideal transformer on the system performance. The analytical and simulation results show that at a given constant output power, the voltage across the plates is significantly reduced, and the system becomes less sensitive to the coupling variations by increasing the turns ratio of the step-down transformer. It is found that Llk can be advantageously utilized as a tuning inductor (L) or part of it. The proposed method is verified by building a prototype CPT system that delivered 25 W at an operation frequency of 1 MHz, and an efficiency of more than 70%. Simultaneously, the voltage stress across the single pair of the coupling plates is reduced from 252 V of a conventional CPT system without a step-down transformer, to 50.4 V using a high-frequency transformer with a turns ratio of 5.
  • Haines jumps: Pore scale mechanisms

    Sun, Zhonghao; Santamarina, Carlos (Physical Review E, American Physical Society (APS), 2019-08-27) [Article]
  • Estimation of saturated hydraulic conductivity of coarse-grained soils using particle shape and electrical resistivity

    Won, Jongmuk; Park, Junghee; Choo, Hyunwook; Burns, Susan (Journal of Applied Geophysics, Elsevier B.V., 2019-08-01) [Article]
    Based on the similarity in the underlying mechanisms between electrical and hydraulic conduction in porous media, Archie's equation can be combined with the Kozeny-Carman (KC) equation to estimate the hydraulic conductivity (K) of coarse-grained soils. However, the assumption of the exponent m in Archie's equation, which is equivalent to the assumed porosity at specific soil electrical properties, reduces the accuracy of the value of K predicted using the combination of Archie's equation and the KC equation. Therefore, this study introduces a depolarization factor, which allows the exponent m in Archie's equation to be estimated from the shape of the particles. Consequently, this study proposes a formula for estimating K for coarse-grained soils based on the combination of Archie's equation, the KC equation, and the depolarization factor. Data from laboratory experiments performed in this work and available data from the literature were used to validate the proposed model. In addition, the optimal value for the exponent m was recommended for predicting hydraulic conductivity using the proposed K estimating formula in the absence of particle shape data. Data obtained in the experiments and literature revealed that the proposed model is comparatively reliable in predicting K.
  • An implicit joint-continuum model for the hydro-mechanical analysis of fractured rock masses

    Shin, Hosung; Santamarina, Carlos (International Journal of Rock Mechanics and Mining Sciences, Elsevier Ltd, 2019-07-01) [Article]
    Fractures control the hydro-mechanical behavior of rock masses. Explicit numerical analyses require detailed information on fracture properties, spacing, and orientation. This paper advances an implicit joint-continuum model for the coupled hydro-mechanical analysis of regularly spaced-persistent fractured rock masses. The stiffness tensor combines the compliance of each fracture set and the intact rock; similarly, the permeability tensor adds the fluid transport through fractures and the matrix. The fully coupled hydro-mechanical analysis incorporates the rock mass stiffness and permeability tensors, and satisfies force equilibrium and macroscopic fluid mass balance. We implement the implicit joint-continuum model within a finite element framework and verify the numerical simulator against closed-form solutions for simple boundary conditions. The application of the code to the hydraulic stimulation of a fractured rock mass shows the effect of stress anisotropy and fracture orientation on the development of open-mode discontinuities (i.e., hydraulic fracture) and hydro-shearing. The implicit joint-continuum model can be readily extended to more complex coupled processes, including thermal and chemical phenomena.
  • Generalized Extreme Value Statistics, Physical Scaling and Forecasts of Gas Production in the Barnett Shale

    Patzek, Tadeusz; Saputra, Wardana; Kirati, Wissem; Marder, Michael (American Chemical Society (ACS), 2019-06-27) [Preprint]
    We develop a method of predicting field-wide gas (or oil) production from unconventional reservoirs, using the Barnett shale as an illustration. Our method has six steps. First, divide a field of interest (here Barnett) into geographic/depositional regions, where -- upon statistical testing -- gas and/or oil production are statistically uniform. Second, in each region i, fit a generalized extreme value distribution to every cohort of gas/oil wells with 1,2,…,ni years on production. Third, obtain accurate estimates of uncertainties in the distribution parameters for each regional well cohort. As a result, obtain ni points for the stable mean (P50) well prototypes for each region i, and the corresponding high/low (P10/P90) bounds on well production. Fourth, by adjusting the producible gas/oil in place and pressure interference times between the adjacent hydrofractures, fit each statistical P50 well prototype with a physics-based scaling curve that also accounts for late-time external gas inflow. The physics-scaled well prototypes now extend 10-20 years into the future. Fifth, for each region, time-shift the dimensional, scaled well prototype and multiply it by the number of well completions during each year of field production. Add the production from all regions to match the past field production and predict decline of all wells up to current time. These well productivity estimates are more accurate and better quantified than anything a production decline curve analysis might yield. Sixth, by assuming different future drilling programs in each region, predict field production futures. We hope that the US Securities and Exchange Commission will adopt our robust, transparent approach as a new standard for booking gas (and oil) reserves in shale wells.
  • Direct and Energy-Transfer-Mediated Charge-Transfer State Formation and Recombination in Triangulene-Spacer-Perylenediimide Multichromophores: Lessons for Photovoltaic Applications

    Albalawi, Ahmed; Stappert, Sebastian; Gorenflot, Julien; Li, Chen; Müllen, Klaus; Andrienko, Denis; Laquai, Frédéric (The Journal of Physical Chemistry C, American Chemical Society (ACS), 2019-06-26) [Article]
    We study the dynamics of primary photoexcitations in three symmetric donor–spacer–acceptor–spacer–donor multichromophores with increasing oligophenylene spacer length, following selective donor or acceptor excitation. Energy levels of the donor and acceptor moieties are tailored to facilitate splitting of the excited state into a lower-lying charge-transfer (CT) state, mimicking the functionality of a donor–acceptor interface for charge generation, thus resulting in long-lived charge separation. Ultrafast electronic energy transfer (ET) from the donor followed by fast hole (back)transfer from the acceptor populates the molecules’ CT states. However, the CT efficiency is found to be close to unity, independent of the donor or acceptor photoexcitation. The ratio of CT and recombination rates, which reflects the population of CT states, increases with the oligophenylene spacer length for both direct hole transfer and hole transfer following ET, boosting the population of CT states under continuous excitation. We observe the population of high-lying “dark” excited states following ET from the donor to the acceptor. The “dark” states successively undergo CT and form CT states of higher energy, with decreased recombination rates, while maintaining the high charge generation efficiency. Changes in CT reaction rates are rationalized within the Marcus theory, with driving forces and reorganization energies evaluated by density functional theory and polarizable continuum models. The present study demonstrates the importance of energetically higher-lying states, which cannot be directly photoexcited yet are accessible through ET from local excited states. Similar processes are anticipated in other donor–acceptor systems, which allow for both energy and CT processes, such as bulk heterojunctions of the polymer and small-molecule donor/nonfullerene acceptor typically used in photovoltaic systems.
  • HVDC shunt tap based on three single-phase half-bridge series-connected MMCs operated under 2L modulation

    Elserougi, Ahmed; Massoud, Ahmed; Ahmed, Shehab (IET Generation, Transmission & Distribution, Institution of Engineering and Technology (IET), 2019-06-19) [Article]
    In this study, a cost-effective HVDC shunt tap with low-number of relatively low-voltage semiconductor devices and small-sized passive components is proposed. The proposed architecture is based on employing three single-phase half-bridge Modular Multilevel Converters (MMCs), where the DC sides of MMCs are connected in series across the total DC-link voltage. The MMCs are adopted instead of conventional Two-Level Voltage Source Converters (2L-VSCs) to avoid the complications of series connection of Insulated Gate Bipolar Transistors (IGBTs). The involved MMCs in the suggested architecture are operated with the conventional 2L modulation, which results in insignificant arm inductors and Sub-Modules (SMs) capacitances (in range of µH and µF, respectively). This, in turn, affects positively the converter cost and footprint. Each arm of the involved MMCs can be considered as a high-voltage valve of a 2L-VSC. To maintain the balance of SMs capacitors, each arm of the involved (N + 1)-level MMC has an extra SM (a balancing SM) to select N out of N + 1 SMs during the turn-off condition. The operational concept, design, and assessment of the proposed architecture are presented in this study. Simulation results are provided for substantiation of the proposed concept. Finally, a scaled down single-phase prototype is used for experimental validation.
  • Sand response to a large number of loading cycles under zero-lateral-strain conditions: Evolution of void ratio and small-strain stiffness

    Park, J.; Santamarina, Carlos (Geotechnique, ICE Publishing, 2019-06-01) [Article]
    Geotechnical structures often experience a large number of repetitive loading cycles. This research examines the quasi-static mechanical response of sands subjected to repetitive loads under zero-lateral-strain boundary conditions. The experimental study uses an automatic repetitive loading frame operated with pneumatic pistons. Both vertical deformation and shear wave velocity are continuously monitored during 10 000 repetitive loading cycles. The void ratio evolves towards the terminal void ratio e T as the number of load cycles increases. The terminal void ratio e T is a function of the initial void ratio e 0 and the stress amplitude ratio
  • Soil Properties: Physics Inspired, Data Driven

    Santamarina, Carlos; Park, Junghee; Terzariol, Marco; Cardona, Alejandro; Castro, Gloria M.; Cha, Wonjun; Garcia, Adrian; Hakiki, Farizal; Lyu, Chuangxin; Salva, Marisol; Shen, Yuanjie; Sun, Zhonghao; Chong, Song-Hun (Springer International Publishing, 2019-05-24) [Book Chapter]
    Research and engineering projects during the last century have advanced the understanding of soil behavior and contributed extensive datasets. Nevertheless, the granular nature of soils challenges the accurate prediction of soil properties. In this context, a physics-inspired and data-driven approach helps us anticipate the soil response. The granular nature of soils defines their inherent properties (e.g., non-linear, non-elastic, porous, pervious) and their effective stress-dependent stiffness, frictional strength and dilation upon shear. The revised soil classification builds on the physical understanding of soils (e.g., packing characteristics and the effect of pore fluid chemistry on fines) and the extensive data accumulated in the field. Asymptotically correct compression models adequately fit experimental data and avoid numerical difficulties. Constant volume friction reflects particle shape and it is strongly dependent on stress path. Repetitive loading leads to characteristic asymptotic conditions (terminal density, and either ratcheting or shakedown). Data and physical analyses suggest a power relationship between void ratio and hydraulic conductivity. The pore-scale origin of suction is interfacial tension and contact angle. P-wave velocity is a good indicator of loss of saturation and S-wave velocity measures the skeletal shear stiffness. Permittivity, electrical conductivity and thermal conductivity are sensitive to water content. Finally, ubiquitous sensors, information technology and cellular communication support the development of effective laboratory characterization techniques and allow us to access large databases. These are transformative changes in geotechnical engineering.
  • Transport and Adsorption of Silica Nanoparticles in Carbonate Reservoirs: A Sand Column Study

    Liu, Qi; Sun, Zhonghao; Santamarina, Carlos (Energy and Fuels, American Chemical Society, 2019-05-16) [Article]
    The adsorption of nanoparticles onto mineral surfaces is a major limitation for applications that require long transport distances, such as enhanced oil recovery. This study investigates silica nanoparticle transport and adsorption in long granular columns, with emphasis on the adsorption onto carbonate substrates, given the fact that carbonate reservoirs host more than 60% of the world’s recoverable oil. The grain-scale particle–mineral interactions are characterized by zeta potential measurements. Ionic strength (especially potential-determining ions: Ca2+, Mg2+, CO32–, etc.) inherently influences the zeta potential of carbonates. Derjaguin–Landau–Verwey–Overbeek analyses show that low surface potential and high ionic concentration inhibit the electrostatic double-layer repulsion and lower the energy barrier of adsorption. Adsorption column experiments simulate a variety of fluid chemistry conditions: pH, ionic concentration, and ion type. Alkaline and low-salinity conditions favor silica nanoparticles transport in carbonate reservoirs. Both scanning electron microscopy images and adsorption mass analyses suggest that the adsorption of nanoparticles onto carbonate substrates is multilayered. A two-term adsorption model adequately captures the instantaneous adsorption and the subsequent kinetic adsorption. The instantaneous adsorption constant delays particle transport, and the kinetic adsorption rate determines the concentration profile of nanoparticles along the reservoir at the steady state. High advection velocity and low adsorption rate k1 are required to deliver high nanoparticle concentration to the far field in the reservoir.
  • Computation of Fields from a Magnetic Dipole in a Conductive Medium Using the QS-DGTD Method

    Özakin, M. Burak; Chen, Liang; Ahmed, Shehab; Bagci, Hakan (Institute of Electrical and Electronics Engineers (IEEE), 2019-05-13) [Conference Paper]
    Loop antennas are often used for field generation in low-frequency electromagnetic applications. Since the antenna dimensions are much smaller than the wavelength, the antenna can accurately be replaced by its equivalent magnetic dipole model in simulations. In this paper, low-frequency magnetic dipole radiation fields in a conductive medium are computed using a three-dimensional discontinuous Galerkin Time-Domain (DGTD) scheme. It is shown that this computation can be accelerated using a material scaling scheme under Quasi-Static (QS) approximation, i.e., time step size can be scaled up without sacrificing from the accuracy and the stability of the time marching scheme. Radiated fields from a magnetic dipole in a conductive medium computed by this accelerated scheme are compared to those obtained using analytical expressions. Results are in good agreement.
  • Why coal ash and tailings dam disasters occur

    Santamarina, Carlos; Torres-Cruz, Luis A.; Bachus, Robert C. (Science, American Association for the Advancement of Science (AAAS), 2019-05-09) [Article]
  • Assessment of CO2 Injectivity During Sequestration in Depleted Gas Reservoirs

    Hoteit, Hussein; Fahs, Marwan; Soltanian, Mohamad Reza (Geosciences, MDPI AG, 2019-05-09) [Article]
    Depleted gas reservoirs are appealing targets for carbon dioxide (CO 2 ) sequestration because of their storage capacity, proven seal, reservoir characterization knowledge, existing infrastructure, and potential for enhanced gas recovery. Low abandonment pressure in the reservoir provides additional voidage-replacement potential for CO 2 and allows for a low surface pump pressure during the early period of injection. However, the injection process poses several challenges. This work aims to raise awareness of key operational challenges related to CO 2 injection in low-pressure reservoirs and to provide a new approach to assessing the phase behavior of CO 2 within the wellbore. When the reservoir pressure is below the CO 2 bubble-point pressure, and CO 2 is injected in its liquid or supercritical state, CO 2 will vaporize and expand within the well-tubing or in the near-wellbore region of the reservoir. This phenomenon is associated with several flow assurance problems. For instance, when CO 2 transitions from the dense-state to the gas-state, CO 2 density drops sharply, affecting the wellhead pressure control and the pressure response at the well bottom-hole. As CO 2 expands with a lower phase viscosity, the flow velocity increases abruptly, possibly causing erosion and cavitation in the flowlines. Furthermore, CO 2 expansion is associated with the Joule–Thomson (IJ) effect, which may result in dry ice or hydrate formation and therefore may reduce CO 2 injectivity. Understanding the transient multiphase phase flow behavior of CO 2 within the wellbore is crucial for appropriate well design and operational risk assessment. The commonly used approach analyzes the flow in the wellbore without taking into consideration the transient pressure response of the reservoir, which predicts an unrealistic pressure gap at the wellhead. This pressure gap is related to the phase transition of CO 2 from its dense state to the gas state. In this work, a new coupled approach is introduced to address the phase behavior of CO 2 within the wellbore under different operational conditions. The proposed approach integrates the flow within both the wellbore and the reservoir at the transient state and therefore resolves the pressure gap issue. Finally, the energy costs associated with a mitigation process that involves CO 2 heating at the wellhead are assessed.
  • Negligible Energy Loss During Charge Generation in Small-Molecule/Fullerene Bulk-Heterojunction Solar Cells Leads to Open-Circuit Voltage over 1.10 V

    Babics, Maxime; Duan, Tainan; Albalawi, Ahmed; Liang, Ru-Ze; Cruciani, Federico; Carja, Ionela-Daniela; Gottlieb, Dale; McCulloch, Iain; Vandewal, Koen; Laquai, Frédéric; Beaujuge, Pierre (ACS Applied Energy Materials, American Chemical Society (ACS), 2019-03-29) [Article]
    Solution-processable small molecules (SMs) that can serve as donors in bulk-heterojunction (BHJ) solar cells are practical alternatives to their polymer counterparts. However, SM–fullerene blends commonly suffer severe voltage losses. In general, devices that reach open-circuit voltages (VOC) > 1 V yield low photocurrents in BHJ solar cells with fullerene acceptors (e.g., PC71BM) and modest power conversion efficiencies (PCEs). In this contribution, we report on the design, synthesis, and BHJ device characteristics of a new SM donor, 2F-DRCN5T, yielding a VOC of up to 1.10 V with PC71BM as the fullerene acceptor, while maintaining PCEs > 7% (over 8% achieved upon solvent-vapor-annealing (SVA) treatment). The negligible energy loss during charge generation (ΔECT), the deep-lying HOMO of 2F-DRCN5T inferred from its large ionization potential (IP), the high charge-transfer-state energy (ECT) of the blend, and a reduced nonradiative voltage loss account for the high VOC achieved in BHJ solar cells.
  • Particle Migration and Clogging in Radial Flow: A Microfluidics Study

    Zhao, Budi; Liu, Q.; Santamarina, Carlos (Water Resources Development and Management, Springer Nature, 2019-03-25) [Book Chapter]
    Migratory particles in porous media experience mechanical and chemo-physical interactions with fluids, pore walls and other particles. The resulting forces (buoyant weight, drag, inertia, and electrical particle-particle and particle-wall) determine particle migration, adhesion and pore clogging. We investigate underlying pore-scale phenomena in convergent radial flow using microfluidic chips. Images reveal distinct clogging mechanics as a function of the particle mass density. The heavy glass particles collide with pore walls and the transient increase in the local volume fraction of particles enhances the probability of bridge formation and clogging at pore throats. On the other hand, quasi-buoyant latex particles follow streamlines closely, but can stick to nearby pore walls at pore constrictions as electrical attraction towards the wall overcomes the repulsive forces. A clogged pore increases the tortuosity of streamlines and promotes further clogging at nearby pores. Statistical data gathered through image analyses identify causal interactions between sequential clogging events.

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