Transport in Porous Media最新文献

This study investigates the thermosolutal convection of a power-law fluid with variable gravity in a vertical through flow that is heated and salted from below. Linear instability analysis investigates the growth of small disturbances in a system. After non-dimensionalizing the governing equations, they are linearized around a base state. The normal mode method applied for solving the perturbation equations. It gives the exponential form to solve stability criteria. The complete study was analyzed by using linear stability analysis; the influence of variable gravity is studied. This theoretical study investigates double-diffusive convection within a porous media filled by power-law fluid. It mainly examines how gravity and concentration gradients influence on thermal solutal convection behavior. The focus is on vertical through flow and its role in the onset and effect of instability.

Predicting the macroscopic properties of thin fiber-based porous materials from their microscopic morphology remains challenging because of the structural heterogeneity of these materials. In this study, computational fluid dynamics simulations were performed to compute volume air flow based on tomographic image data of uncompressed and compressed paper sheets. To reduce computational demands, a pore network model was employed, allowing volume air flow to be approximated with less computational effort. To improve prediction accuracy, geometric descriptors of the pore space, such as porosity, surface area, median pore radius, and geodesic tortuosity, were combined with predictions of the pore network model. This integrated approach significantly improves the predictive power of the pore network model and indicates which aspects of the pore space morphology are not accurately represented within the pore network model. In particular, we illustrate that a high correlation among descriptors does not necessarily imply redundancy in a combined prediction.

This study revisits and extends the analytical model presented by Maas (J Hydrol 347:223–228, 2007), which describes simultaneous downward infiltration of fresh water and upward seepage of fresh or saline groundwater beneath an elongated island. Under steady-state conditions and using the sharp interface approximation, the interface between the two types of water forms a semi-elliptical shape. Notably, the unusual y-linearity of the flow potential provides an analytical advantage, enabling a direct and elegant extension from a one-phase to a two-phase system. For transient conditions, Maas (J Hydrol 347:223–228, 2007) employed a successive steady-state approach based on elliptical shapes. We demonstrate that this approach is physically inconsistent, as the tip of the lens must possess a finite derivative to allow for movement. Instead, we introduce an interface motion equation to track this front dynamically. Additionally, we identify potentially unstable configurations during outward lens migration, where denser salt water temporarily overlays fresh water near the lens tip. To address this, we incorporate diffusion, moving beyond the sharp interface assumption. Finally, we assess the applicability of Maas’s elliptical approximation for interface motion and find it remains robust as long as the approximation that lens thickness is negligible compared to its width is used with caution. These findings broaden the analytical understanding of fresh water lens dynamics in island aquifers and refine the conditions under which simplified models remain valid.

We revisit the classical problem of fully developed Darcy–Brinkman flow through a tube with elliptic cross section. Building upon the exact velocity field originally derived by Narasimhacharyulu and Pattabhiramacharyulu (Proc. Indian Acad. Sci. Sect. A 87:79–83, 1978), we find, for the first time, an exact series expression for the Poiseuille number in this regime. Our results match the earlier Ritz-based approximations and are in close agreement with the finite-element solutions presented here.

We present a pore network approach for the simulation and study of biofilm growth inside porous structures under various limiting conditions. The proposed pore-scale model allows us to resolve the interrelationship between growth and diffusive transport based on the solution of coupled ordinary differential equations. Special focus of this study is on diffusion as well as on metabolically limited conditions, which is realized with different second Damköhler numbers. Instead of relying on idealized geometries, the pore network structures are generated using the effective transport properties of thin sintered particles and fibrous felt porous layers derived from high-resolution X-ray micro-CT scans. The great differences in pore sizes and porosities of the regarded structures result in significantly different effective diffusivities. In addition to that, competitive substrate consumption and inhibition is achieved using the experiment-based kinetic model for S. oneidensis from Tang et al. (Tang et al., Biotechnol. Bioeng. 96:125–133, 2007). The primary nutrients are lactate and oxygen. Acetate is both, a by-product and a potential substrate, theoretically enabling dynamic shifts in substrate utilization. With the chosen parameters and conditions, the second Damköhler number can be varied with a significant impact on biomass distribution inside of the two selected pore networks, especially in dependence on oxygen availability in single pores. The simulation results show that biofilm growth is limited by the transport of dissolved oxygen. Interestingly, significantly more biomass per m³ is produced in the sintered structure because of the generally higher pore utilization degree.

Graphical Abstract

Multiphase flow simulation in porous media is a challenging task with significant industrial implications. Pore Network Modeling (PNM) is an effective method that provides accurate results within a reasonable computational timeframe. However, as the complexity of these systems increases, particularly when simulating whole-core-sized pore networks (Digital Plugs) with millions of elements, there is a growing demand to improve the computational efficiency of PNM. The primary computational bottleneck is the pressure field update process, which involves solving a linear system of balance equations. To address this issue, our research focuses on evaluating the performance of a recently developed multiscale preconditioner for solving this system. We compare its performance against a state-of-the-art algebraic multigrid (AMG) method. Networks where the multiscale preconditioner outperforms AMG are identified, and a multilevel strategy is implemented to extend the capabilities of the method to networks with up to 200 million pore bodies. This shows the multiscale method is a promising alternative to accelerate multiphase simulations in Pore Network Modeling.

Calcium carbonate scaling poses a significant challenge in oil and gas production, hindering recovery and impacting economic viability. This study utilizes microfluidic "reservoir-on-chip" platforms to visualize, quantify, and characterize CaCO₃ precipitation in hydrophobic and hydrophilic porous media to elucidate scaling mechanisms. Traditional methods face limitations in observing the intricacies of scale formation at the pore scale. Microfluidic platforms, however, offer real-time, high-resolution visualization of flow dynamics and scale deposition, enabling the study of key parameters like temperature, solution concentration, and surface wettability. This research investigates the impact of these parameters on CaCO₃ scaling, with a particular focus on wettability's influence on the nucleation process. By elucidating the interplay of different factors, this study aims to provide insights into mitigating and controlling scale formation in oil and gas production. Our findings demonstrate that the covered area by precipitates increased with increasing temperature and concentration for both hydrophobic and hydrophilic surfaces, with more substantial coverage observed on hydrophilic surfaces. Scanning electron microscopy and X-ray diffraction analysis confirmed the presence of calcite, vaterite, and aragonite polymorphs. Furthermore, the findings hold implications for advancing carbon capture, utilization, and storage (CCUS) technologies, particularly mineral carbonation, by providing a deeper understanding of carbonate formation dynamics at the pore scale.

Graphical abstract

Convective dissolution in porous media is pivotal in natural and industrial processes, including the subsurface storage of carbon dioxide (({{CO}_{2}})). Convective dissolution can arise when a denser layer forms at the interface between two fluids and strongly enhances the mass transfer rate with respect to diffusion only. Despite its significance, the interplay between diffusion, convection, and dissolution under realistic thermodynamic conditions remains largely unexplored. In a recent study (Imuetinyan et al. in Transp Porous Media 151:1687–1708, 2024), we investigated the convective dissolution of two miscible liquids in saturated transparent porous media. Here, we extend this approach to study the convective dissolution of a layer of gaseous ({{CO}_{2}}) injected on top of a porous medium saturated with a liquid mixture of cyclohexanol and toluene within a high-pressure cell at different temperatures. In such configuration, convective dissolution is induced by the density difference between the saturating fluid and a ({{CO}_{2}})-rich boundary layer generated at the interface by diffusion. Different Rayleigh numbers (Ra) from (10^{4}, hbox {to},10^5) are investigated by modifying the ({{CO}_{2}}) injection pressure. The system is investigated by shadowgraphy, an optical tool extremely sensitive to density variations. Then, by image variance analysis, we study the temporal evolution of the convective dissolution process, highlighting the diffusion, dissolution and convection phases, and we quantify the onset time of convection and the convective front speed. We find that the dimensionless plume velocity scales as (sim sqrt{textrm{Ra}}), indicating that flow regimes critically impact the convective mixing in porous media.

Carbonate rocks exhibit complex pore structures with wide variability in size, shape and connectivity that challenge accurate multiphase flow modeling. While representing detailed throat geometry and fluid interfaces, the Generalized Network Model (GNM) overlooks sub-resolution porosity by relying on a single micro-CT (µCT) image. To address this limitation, we introduce the multiscale GNM that incorporates unresolved porosity regions using difference maps between dry and brine-saturated µCT images. These regions are simplified into Darcy-type microlinks that represent effective brine-invaded porosity while significantly reducing computational cost. The model is calibrated against mercury intrusion capillary pressure (MICP) and high-resolution differential imaging porous plate (DIPP) drainage data for heterogeneous Ketton and reservoir carbonate samples. Experimental data guide the tuning of model parameters to capture fluid invasion across different pore scales. Our findings highlight that sub-resolution porosity, particularly intermediate-sized pores, plays a key role in sustaining flow and connectivity, challenging the common assumption that unresolved pores are merely water-filled and poorly connected. The multiscale GNM reproduces experimental capillary pressure data and predicts water relative permeability with good quantitative accuracy in a blind test. This work provides a practical and efficient framework for reliable, physically grounded flow predictions in complex multiscale porous media, complementing costly, time-intensive laboratory measurements and reducing the reliance on often unavailable higher-resolution images.