Transport in Porous Media最新文献

{"title":"Atomistic MD Assessment of Al2SiO5 Aluminosilicate for Desalination Water/Ion Selectivity and Complementary Machine Learning Forecasting of Reverse Osmosis Performance","authors":"Nour El Haq El Macouti, Mohamed El Bouanounou, Abdelmajid Assila, El Kebir Hlil, Yahia Boughaleb, Abdellatif Aarfane, Abdelowahed Hajjaji, Said Laasri","doi":"10.1007/s11242-026-02331-3","DOIUrl":"10.1007/s11242-026-02331-3","url":null,"abstract":"<div><p>Despite growing global water stress, the rational design of desalination membranes remains constrained by a gap between atomistic transport mechanisms and operational performance prediction. Here, we present, to our knowledge, the first dedicated atomistic desalination transport assessment of Al<sub>2</sub>SiO<sub>5</sub> aluminosilicate as an ultrathin reverse osmosis model membrane candidate, together with complementary machine learning regression models trained on conventional RO operational data. The MD component provides molecular-scale insight into Al<sub>2</sub>SiO<sub>5</sub> water/ion selectivity, whereas the ML component demonstrates system-level forecasting of flux and salt rejection from routine RO monitoring variables. Because the operational dataset was not obtained from Al<sub>2</sub>SiO<sub>5</sub> membranes, the two components are interpreted as complementary rather than directly coupled. Non-equilibrium molecular dynamics simulations were performed for 5 ns at ~ 300 K using an intentionally elevated transmembrane pressure (~ 150 MPa) to access statistically meaningful permeation events on nanosecond timescales. To ensure physically rigorous treatment of long-range interactions, the simulation cell was expanded to a 3 × 3 periodic array in the membrane plane (approximately 37.4 × 42.1 × 160.0 Å), enabling the use of a standard 12.0 Å non-bonded cutoff that satisfies the minimum image convention and is consistent with TIP4P/2005 water and ClayFF aluminosilicate force fields. The results are, therefore, interpreted mechanistically rather than as direct industrial flux predictions. The Al<sub>2</sub>SiO<sub>5</sub> framework remained structurally intact throughout production (RMSD = 0.76 ± 0.16 Å; membrane thickness = 6.66 ± 0.16 Å), with preserved aluminosilicate coordination confirmed by persistent Si–O (~ 1.48 Å) and Al–O (~ 1.70 Å) RDF signatures. Continuous water permeation was observed across the 3 × 3 membrane, with an early-stage permeation rate of 469.5 ± 1.4 water molecules ns<sup>−1</sup> from the 0.2 to 2.0 ns linear regime, corresponding to an MD-apparent permeance of 2.14 × 10<sup>3</sup> LMH bar<sup>−1</sup> under accelerated driving conditions. The later reduction in slope was consistent with finite feed depletion in the nanoscale simulation cell. Ion transport was strongly suppressed, with a final ion rejection of approximately 94.2%: Out of 180 Na⁺ and 180 Cl<sup>−</sup> ions in the feed, only 9 Na⁺ and approximately 12 Cl<sup>−</sup> ions reached the permeate side over the full 5 ns production window. Apparent free-energy profiles provide a mechanistic explanation for this selectivity, revealing substantially higher barriers for Na⁺ (3.06 kcal mol<sup>−1</sup>, ~ 5.1 <i>k</i><sub><i>B</i></sub><i>T</i>) and Cl<sup>−</sup> (2.58 kcal mol⁻<sup>1</sup>, ~ 4.3 <i>k</i><sub><i>B</i></sub><i>T</i>) than for water (0.70 kcal mol⁻<sup>1</sup>, ~ 1.2 <i>k</i><sub><i>B</i></sub><i>T</i>) near the membrane region. At","PeriodicalId":804,"journal":{"name":"Transport in Porous Media","volume":"153 6","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148281029","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental Investigation of the Influence of a Jet Injection on the Gas Flow Field Inside an Idealized Packed-Bed Model with Structured Parallel Bars","authors":"C. Velten,&nbsp;K. Zähringer","doi":"10.1007/s11242-026-02328-y","DOIUrl":"10.1007/s11242-026-02328-y","url":null,"abstract":"<div><p>Industrial processes involving packed beds with gaseous flow are often associated with high energy and resource consumption. A detailed understanding of the flow behaviour within such systems is essential for optimizing performance. In this study, a structured, optically accessible polyhedral model packed bed with an additional side jet injection is employed to investigate two-dimensional airflow fields using Particle Image Velocimetry (PIV). Experiments are conducted for particle Reynolds numbers ranging from 100 to 1000 through the vertical flow inlet, examining the flow within the packing and in the freeboard region above it. In the absence of a side jet, the flow patterns largely follow the geometry of the packing and repeat at similar positions along the bed height. A side jet with volumetric flow rates varied between 2 and 18 L/min, corresponding to jet Reynolds numbers from 1403 to 12624, is then applied to perturb the flow. It introduces significant horizontal velocities and leads to increased flow asymmetries and fluctuations. The high-resolution PIV data enable a detailed analysis of the mean velocity fields and flow fluctuation characteristics, quantified through the turbulent kinetic energy (TKE). Flow structures develop with increasing particle Reynolds numbers and, once formed, remain visible while only their intensity increases further. These findings offer quantitative insights into the interaction between structured packing geometries and gas flow with increasing velocity fluctuations. A comprehensive data framework for validation of numerical simulations and development of new experimental methods is provided with these results.</p></div>","PeriodicalId":804,"journal":{"name":"Transport in Porous Media","volume":"153 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2026-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11242-026-02328-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148237087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Combined Multiscale Core Flooding and Digital Rock Workflow to Determine CO₂ Relative Permeability and Capillary Trapping in a Reservoir Sandstone","authors":"Rukuan Chai,&nbsp;Shehzad Ahmed,&nbsp;Sajjad Foroughi,&nbsp;Takashi Akai,&nbsp;Lionel Esteban,&nbsp;Michael B. Clennell,&nbsp;Miki Koyama,&nbsp;Katsumo Takabayashi,&nbsp;Martin J. Blunt,&nbsp;Branko Bijeljic","doi":"10.1007/s11242-026-02327-z","DOIUrl":"10.1007/s11242-026-02327-z","url":null,"abstract":"<div><p>Accurate characterization of CO₂-brine relative permeability and residual trapping is essential to design reliable carbon sequestration in geological formations. This study presents an integrated workflow that combines special core analysis (SCAL), digital rock physics (DRP) and pore-network modeling (PNM). This workflow is used to quantify and accurately assess the multiphase flow and capillary trapping of CO₂ in reservoir sandstones under subsurface-relevant conditions. This approach links pore-scale mechanisms with core-scale behavior using high-resolution X-ray micro-computed tomography (micro-CT) to capture pore structures, fluid configuration and wettability, alongside PNM. The good agreement between the SCAL and DRP experimental results ensures consistent macroscopic flow properties for the two experiments conducted at different length scales. Both experimental results indicate limited CO₂ mobility in water-wet systems during drainage where limited viscous force is applied. The distribution of CO₂ ganglia volume obtained from micro-CT imaging narrows considerably after waterflooding, indicating successful CO₂ capillary trapping. Furthermore, PNM is used to match the measured relative permeability and capillary trapping. This matched PNM can then be used to predict conditions that are difficult to achieve experimentally, such as reaching the maximum CO₂ saturation after drainage and multiple hysteresis cycles to determine the Land trapping curve. The integrated workflow advances the mechanistic understanding of CO₂ transport and immobilization in geological formations, offering a robust tool for optimizing carbon storage strategies.</p></div>","PeriodicalId":804,"journal":{"name":"Transport in Porous Media","volume":"153 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2026-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11242-026-02327-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148236515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"How to Deal with Heat of Adsorption in Microscopic Mathematical Modeling of Adsorbent–Fluid Systems?","authors":"Taylan Maraş,&nbsp;Melkon Tatlier","doi":"10.1007/s11242-026-02330-4","DOIUrl":"10.1007/s11242-026-02330-4","url":null,"abstract":"<div><p>The placement of the heat of adsorption term in microscopic mathematical models significantly influences predicted transport behavior and system performance. This term may be incorporated either in the thermal energy equation or in the boundary condition at the adsorbent–fluid interface. In this study, the implications of these two formulations were investigated for adsorption heat pumps applications utilizing adsorbent coatings. Results showed that, generally, longer heat pump cycle durations were observed when the heat of adsorption term was included in the boundary condition at the adsorbent–fluid interface. Characteristics of water adsorption isotherms of the adsorbents, including their regeneration temperatures, had notable impact on the results. A dimensionless analysis based on the Fourier/Lewis (Fo/Le) ratio was introduced to interpret the results in terms of underlying transport regimes. It was shown that the discrepancy between the two formulations depended strongly on this ratio, which reflected the relative effectiveness of mass diffusion over the coating thickness. At low Fo/Le values, where mass transfer resistance dominated, the predictions of the two formulations remained relatively close. In contrast, at moderate to high Fo/Le values, the adsorption process became increasingly sensitive to surface thermal conditions, leading to significant divergence between the two approaches. Validation was performed using experimental data for zeolite NaA, based on optimum coating thickness derived from adsorption kinetics. The formulation incorporating the heat of adsorption in the boundary condition was found to provide significantly better agreement with experimental observation, while the other formulation overpredicted the optimum thickness.</p></div>","PeriodicalId":804,"journal":{"name":"Transport in Porous Media","volume":"153 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2026-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148236922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transport Pathway Evolution and Retention Dynamics of Escherichia Coli in Homogeneous and Heterogeneous Porous Media","authors":"Yuanyuan Jia,&nbsp;Zhipeng Tu,&nbsp;Wenjing Zhang,&nbsp;Shutong Jiang,&nbsp;Jiaming Sun,&nbsp;Bo Wan","doi":"10.1007/s11242-026-02329-x","DOIUrl":"10.1007/s11242-026-02329-x","url":null,"abstract":"<div><p>Understanding the migration mechanisms of pathogenic microorganisms in groundwater systems is essential for effective pollution prevention. Unlike traditional studies that rely on idealized homogeneous media, this study applies a dual-pore medium to better represent the structural heterogeneity of natural soils. Besides, the fluorescent <i>Escherichia coli</i> (<i>eGFP-E.coli</i>) is used as a microbial tracer. Combined with high-resolution light reflection visualization technique, microbial migration is visually observed and its spatial and temporal distributions are also quantitatively characterized. The experimental results show: (1) The <i>eGFP-E.coli</i> shows rapid advection–diffusion characteristics in the homogeneous medium, while its migration rate reduces rapidly and shows uneven distribution in the heterogeneous medium through effects of physical retention and preferential flow path remodeling. (2) The gravity flow of water initially facilitates the rapid migration of microorganisms in unsaturated zone, but the capillary blockage effect caused reduces transport efficiency and the bioretention zone is formed as approaching the saturated zone. (3) The homogeneous medium induces uniform water flow to form stable migration corridors, while heterogeneous medium induces localized flow field reconstruction and regulates microbial detachment–reattachment dynamics. These findings provide a foundational understanding of how pore structure heterogeneity and hydraulic dynamics regulate microbial migration at the pore scale. This could serve as a conceptual basis for designs of pollution control barriers and future models that incorporate physicochemical coupled processes.</p><h3>Graphical Abstract</h3>\u0000<div><figure><div><div><picture><source><img></source></picture><span>The alternative text for this image may have been generated using AI.</span></div></div></figure></div></div>","PeriodicalId":804,"journal":{"name":"Transport in Porous Media","volume":"153 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2026-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148172844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tracking Microstructure Variations of CO2–hydrate Formation in Porous Sandstone from µCT Images During Cold CO2 Injection","authors":"Sina Marti,&nbsp;Alv-Arne Grimstad,&nbsp;Torleif Holt,&nbsp;Jørgen F. Lie,&nbsp;Amir Ghaderi,&nbsp;Ane E. Lothe","doi":"10.1007/s11242-026-02324-2","DOIUrl":"10.1007/s11242-026-02324-2","url":null,"abstract":"<div><p>Depleted reservoirs are possible candidates for long-term CO₂ storage, but the risk of the Joule Thomson effect causing near-well cooling and hydrate formation under CO₂ injection is calling for an in-depth understanding of the process in porous media to avoid injection issues.Query Whereas much has been learned from detailed experimental studies on the micro-scale, challenges remain in how these observations upscale to the reservoir scale. In this study, we aim to provide a link between micro- and meso-scale—performing an in-situ core-flooding experiment in a micro-computed tomography (µCT) system, enabling repeated imaging of pore-scale structural evolution throughout a 24.5-cm-long, 3.7-cm-diameter sandstone core. Under controlled pressure and temperature conditions, full µCT scans were acquired at successive cooling steps during CO₂ injection. Hydrate formation initiated at 2 °C and revealed spatially variating microstructural—from patchy/finger-like structures to a fully reacted main hydrate “plug”, larger residual brine “channels”, a diffuse decrease in the amount of hydrate in the upper regions of the vertically oriented core and a spherical shaped zone devoid of hydrate directly under the injection point. Showcasing the higher degree of complexity that should be expected in larger-scale systems. With a relatively simple image processing workflow, our approach shows the feasibility of studying hydrate growth at micro-scale resolution over meso-scale volume with in-house µCT facilities.</p></div>","PeriodicalId":804,"journal":{"name":"Transport in Porous Media","volume":"153 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2026-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11242-026-02324-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148172946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modified Theoretical Model for Temperature-Dependent Electro-Kinetic Properties of Porous Media","authors":"P. W. J. Glover","doi":"10.1007/s11242-026-02321-5","DOIUrl":"10.1007/s11242-026-02321-5","url":null,"abstract":"<div><p>I report theoretical modelling of streaming potential coefficient <i>C</i>_sp and zeta potential <i>ζ</i> in porous media with NaCl electrolytes as a function of temperature up to 150°C. The modelling captures the essential behaviour of both <i>C</i>_sp and <i>ζ</i> as a function of both temperature, salinity and pH, the latter of which also depends on temperature and salinity. The modelling also shows <i>ζ</i> which is negative, decreasing in magnitude with temperature, and as pH becomes smaller. It also shows that <i>C</i>_sp is also negative but has a complex temperature and pH dependence. These behaviours are controlled mainly by the temperature dependence of pH, but also depend on the temperature dependence of the density, viscosity, relative permittivity and electrical conductivity of the pore solution. The model has been compared to experimental data for sandstones up to 150°C, and describes the data reasonably well when using physically reasonable values for the electro-chemical parameters describing the electrical double layer. This modelling has implications for the calculation of electro-kinetic parameters in geothermal reservoirs, CCUS targets and radioactive storage underground.</p></div>","PeriodicalId":804,"journal":{"name":"Transport in Porous Media","volume":"153 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2026-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11242-026-02321-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148146935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Potential-Game Formulation for Thermodynamic Equilibrium of Two-Phase Systems in Pore Networks","authors":"Arman Mojoodi","doi":"10.1007/s11242-026-02326-0","DOIUrl":"10.1007/s11242-026-02326-0","url":null,"abstract":"<div><p>Thermodynamic equilibrium configurations in heterogeneous porous media remain poorly characterized due to the dominance of flow-driven experimental and numerical approaches. We introduce an equilibrium modeling framework that formulates pore-scale phase distribution as an exact potential game, where each pore minimizes total interfacial free energy without external forcing. This approach directly targets equilibrium states—bypassing displacement dynamics—and converges within seconds for networks of thousands of pores. Simulations on mixed-wet networks reveal a fundamental finding: Multiple morphologically distinct equilibrium states coexist under identical energetic parameters, exhibiting water saturations ranging from 0.48 to 0.77 and varying interfacial area distributions. Crucially, all configurations yield a narrowly confined thermodynamic contact angle (<i>θ</i>_t ≈ 94.5°), demonstrating that <i>θ</i>_t is an intrinsic property of the solid–fluid–fluid system rather than a morphology-dependent observable. The predicted <i>θ</i>_t shows close agreement (within 6°) with values inferred from steady-state experiments under intermediate fractional flow, despite the absence of imposed flow or pressure gradients. These results establish that equilibrium wettability cannot be inferred from a single saturation state; instead, it emerges from thermodynamic relationships between multiple equilibrium configurations sharing identical pore geometry and wettability distributions. The framework provides a computationally efficient equilibrium reference (runtime <span>(&lt;10)</span> s) for interpreting pore-scale wettability, benchmarking dynamic simulations, and isolating intrinsic thermodynamic behavior from flow-history effects. By decoupling equilibrium physics from displacement pathways, this work offers a rigorous baseline for distinguishing true wettability signatures from non-equilibrium artifacts in porous media characterization.</p></div>","PeriodicalId":804,"journal":{"name":"Transport in Porous Media","volume":"153 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2026-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148146933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"TauTORT3D: A Geometry-Based Particle Tracing Framework for Tortuosity in 3D Porous Geometries","authors":"Mohd Tauheed,&nbsp;Omar Khaled Saker,&nbsp;Ammar Alsheghri","doi":"10.1007/s11242-026-02322-4","DOIUrl":"10.1007/s11242-026-02322-4","url":null,"abstract":"<div><p>Tortuosity is a key parameter governing transport behavior in complex porous media and plays a critical role in engineering, biological, and environmental applications. In this study, we present TauTORT3D, a geometry-based particle tracing framework implemented in MATLAB for estimating geometric tortuosity and mass transport in three-dimensional porous geometries imported from STL surface meshes. The method is user-friendly, computationally efficient, and capable of identifying connected transport paths through complex pore networks. TauTORT3D employs a voxel-based particle tracking approach in which finite-size spherical particles are propagated through interconnected pore spaces along prescribed directions. Particle motion is governed by continuous geometric fields derived from signed distance functions, enabling robust collision handling and geometrically consistent trajectories without reliance on pore-network abstraction, skeletonization, or continuum flow solvers. Particle trajectories are recorded until exit is reached, from which tortuosity distributions, exit time statistics, and time-dependent mass flux are computed. Parametric studies show that increasing particle number improves statistical sampling without altering the underlying transport behavior, indicating that tortuosity distributions are intrinsic, architecture-driven features. A benchmark study is performed using literature-inspired porous geometries to assess the consistency of the proposed framework, and the results are compared with diffusion-based pore-network simulations implemented in Dragonfly, showing consistent median trends within approximately 3–8%, reflecting differences between geometric and diffusion-based definitions of tortuosity. The framework is applicable to a broad class of porous media and micro-architected structures, including triply periodic minimal surface lattices and cellular foams.</p></div>","PeriodicalId":804,"journal":{"name":"Transport in Porous Media","volume":"153 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2026-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148146934","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Empirical Indicators for Screening Three-Tier Retardation of Decay Chain Radionuclides in Sequential Triple-Continuum Fractured Media","authors":"Neng-Chuan Tien","doi":"10.1007/s11242-026-02320-6","DOIUrl":"10.1007/s11242-026-02320-6","url":null,"abstract":"<div><p>Using a solubility-controlled Th-230–Ra-226 decay-pair transport model in GoldSim, dimensionless screening diagnostics are developed for fractured rock in which retardation proceeds through three successive tiers: deposited-colloid coating, fracture skin, and rock matrix. Two empirical indicators are proposed: the cascade number <i>N</i>_c, quantifying the competition between skin diffusive uptake and fracture advection, and the decay-diffusion number <i>N</i>_d, quantifying the competition between Th-230 decay and Ra-226 back-diffusion from the matrix. Systematic parameter sweeps over pore diffusion coefficient, flow rate, coating and Ra-226 distribution coefficients, and skin thickness across 31 simulations are used to evaluate these diagnostics against model outputs. <i>N</i>_c captures a multi-order-of-magnitude transition in Th-230 outlet flux from advection-dominated to diffusion-bridge-dominated behaviour, while <i>N</i>_d independently governs the Ra-226 secondary peak flux via the matrix retardation factor. The coating distribution coefficient exhibits a threshold response, functioning as an activation switch that determines whether the Th-230 residence time at the fracture wall is sufficient for the diffusion bridge to operate. A sequence sensitivity index evaluated at midstream shows that two fracture-segment arrangements can produce nearly identical outlet fluxes yet diverge considerably at interior observation points, indicating that outlet-based assessments may obscure fundamentally different internal risk distributions. Together, these diagnostics provide a rapid screening tool for performance assessment to determine, before committing to full simulations, whether the three-tier cascade, sequence effects, and midstream monitoring warrant explicit consideration under site-specific conditions.</p><p>Article Highlights</p><ol>\u0000 <li>\u0000 <span>1.</span>\u0000 \u0000 <p>Two dimensionless indicators rapidly screen whether a three-tier retardation cascade matters for a given site.</p>\u0000 \u0000 </li>\u0000 <li>\u0000 <span>2.</span>\u0000 \u0000 <p>Colloid-coating sorption acts as an on/off switch, not a gradual modifier, for daughter–nuclide generation.</p>\u0000 \u0000 </li>\u0000 <li>\u0000 <span>3.</span>\u0000 \u0000 <p>Outlet monitoring alone can mask large internal flux differences caused by fracture-segment ordering.</p>\u0000 \u0000 </li>\u0000 </ol></div>","PeriodicalId":804,"journal":{"name":"Transport in Porous Media","volume":"153 5","pages":""},"PeriodicalIF":2.6,"publicationDate":"2026-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11242-026-02320-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148009297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}