scholarly journals Nucleation and supersaturation in porous media (revisited)

2014 ◽  
Vol 78 (6) ◽  
pp. 1437-1447 ◽  
Author(s):  
M. Prieto
Keyword(s):  
Experimental Data ◽  
Porous Media ◽  
Interfacial Tension ◽  
Induction Time ◽  
Reactive Transport ◽  
Theoretical Calculations ◽  
Transport Processes ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Nucleation Time

Supersaturation-Nucleation-Time (S-N-T) diagrams are shown to be a useful tool to predict nucleation during reactive-transport processes in porous media. Such diagrams can be determined experimentally or estimated from theoretical calculations based on classical nucleation theory. With this aim, a ‘pragmatic’ understanding of the nucleation rate equation is adopted here and the meaning and magnitude of the interfacial tension and induction time discussed. Theoretical diagrams and experimental data are shown to match fairly well as long as there is an appropriate choice of the ‘relevant’ volume for induction-time calculations.

The Effect of Turbulence and Real Gas Models on the Two Phase Spontaneously Condensing Flows in Nozzle

2013 ◽  
Author(s):  
Yogini Patel ◽  
Giteshkumar Patel ◽  
Teemu Turunen-Saaresti
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Navier Stokes ◽  
Two Phase ◽  
Real Gas ◽  
Spontaneous Condensation ◽  
Condensing Flows ◽  
Computational Fluid Dynamics Cfd

The aim of the paper is to analyse the effect of turbulence and real gas models on the process of spontaneous condensation in converging diverging (CD) nozzle by using commercial Computational Fluid Dynamics (CFD) code. The calculations were based on the 2-D compressible Navier-Stokes (NS) equations coupled with two-equation turbulence model, and the non-equilibrium spontaneous condensing steam flow was solved on the basis of the classical nucleation theory. The results were validated to the available experimental data.

Porous media as a canvas for hydro-bio-geo-chemical processes: Facing the challenges

2021 ◽  
Author(s):  
Xavier Sanchez-Vila
Keyword(s):  
Porous Media ◽  
Reactive Transport ◽  
Field Work ◽  
Open Science ◽  
Transport Processes ◽  
Aquifer Recharge ◽  
Music Production ◽  
Emerging Compounds ◽  
Technological Developments ◽  
Large Research

<p>The more we study flow and transport processes in porous media, the larger the number of questions that arise. Heterogeneity, uncertainty, multidisciplinarity, and interdisciplinarity are key words that make our live as researchers miserable… and interesting. There are many ways of facing complexity; this is equivalent as deciding what colors and textures to consider when being placed in front of a fresh canvas, or what are the sounds to include and combine in a music production. You can try to get as much as you can from one discipline, using very sophisticated state-of-the-art models. On the other hand, you can choose to bring to any given problem a number of disciplines, maybe having to sacrifice deepness in exchange of the better good of yet still sophisticated multifaceted solutions. There are quite a number of examples of the latter approach. In this talk, I will present a few of those, eventually concentrating in managed aquifer recharge (MAR) practices. This technology involves water resources from a myriad of perspectives, covering from climate change to legislation, from social awareness to reactive transport, from toxicological issues to biofilm formation, from circular economy to emerging compounds, from research to pure technological developments, and more. All of these elements deserve our attention as researchers, and we cannot pretend to master all of them. Integration, development of large research groups, open science are words that will appear in this talk. So does mathematics, and physics, and geochemistry, and organic chemistry, and biology. In any given hydrogeological problem you might need to combine equations, statistics, experiments, field work, and modeling; expect all of them in this talk. As groundwater complexity keeps amazing and mesmerizing me, do not expect solutions being provided, just anticipate more and more challenging research questions being asked.</p>

scholarly journals Pore-Scale Modeling of Mineral Growth and Nucleation in Reactive Flow

2022 ◽  
Vol 3 ◽  
Author(s):  
Vitalii Starchenko
Keyword(s):  
Reactive Transport ◽  
Surface Reaction ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Classical Nucleation Theory ◽  
Reactive Flow ◽  
Natural Environments ◽  
Pore Scale ◽  
Arbitrary Lagrangian Eulerian ◽  
Mineral Precipitation

A fundamental understanding of mineral precipitation kinetics relies largely on microscopic observations of the dynamics of mineral surfaces exposed to supersaturated solutions. Deconvolution of tightly bound transport, surface reaction, and crystal nucleation phenomena still remains one of the main challenges. Particularly, the influence of these processes on texture and morphology of mineral precipitate remains unclear. This study presents a coupling of pore-scale reactive transport modeling with the Arbitrary Lagrangian-Eulerian approach for tracking evolution of explicit solid interface during mineral precipitation. It incorporates a heterogeneous nucleation mechanism according to Classical Nucleation Theory which can be turned “on” or “off.” This approach allows us to demonstrate the role of nucleation on precipitate texture with a focus at micrometer scale. In this work precipitate formation is modeled on a 10 micrometer radius particle in reactive flow. The evolution of explicit interface accounts for the surface curvature which is crucial at this scale in the regime of emerging instabilities. The results illustrate how the surface reaction and reactive fluid flow affect the shape of precipitate on a solid particle. It is shown that nucleation promotes the formation of irregularly shaped precipitate and diminishes the effect of the flow on the asymmetry of precipitation around the particle. The observed differences in precipitate structure are expected to be an important benchmark for reaction-driven precipitation in natural environments.

Reactive transport of dichloromethane in porous media under dynamic hydrogeological conditions: from experiments to modelling

2020 ◽  
Author(s):  
Maria Prieto Espinoza ◽  
Sylvain Weill ◽  
Raphaël Di chiara ◽  
Benjamin Belfort ◽  
François Lehmann ◽  
...  
Keyword(s):  
Porous Media ◽  
Water Table ◽  
Reactive Transport ◽  
Transport Processes ◽  
Redox Conditions ◽  
Degradation Pathways ◽  
Water Table Fluctuations ◽  
Transport In Porous Media ◽  
Effect Of Water ◽  
Hydrogeological Conditions

<p>Reactive transport in porous media involves a complex interplay of multiple processes relative to flow of water and gases, transport of elements, chemical reactions and microbial activities. In surface-groundwater interfaces, the role of the capillary fringe is of particular interest as water table variations can strongly impact the transfer of gases (e.g. oxygen), the evolution of redox conditions and the evolution/adaptation of bacterial/microbial populations that control biodegradation pathways of contaminants. Although the understanding of individual processes is advanced, their interactions are not yet fully understood challenging the development of efficient reactive transport models (RTM) for predictive applications. In this context, the combination of microbial approaches with isotope measurements and modelling may be useful to understand reactive transport of halogenated pollutants in hydrogeological dynamic systems, to improve processes representation in RTMs, and to reduce model equifinality. Dichloromethane (DCM) is a toxic and volatile halogenated compound frequently detected in multi-contaminated aquifers. Although mechanisms of DCM microbial degradation under both aerobic and anaerobic conditions have been described, little is known about the relationships between the hydrogeochemical variations caused by water table fluctuations, as well as their effects on the diversity and distribution of bacterial communities and degradation pathways.<br>            In this study, two laboratory aquifers fed by contaminated groundwater from the industrial site Thermeroil (France) were designed to collect water samples at high-resolution to investigate the reactive transport of DCM in porous media under steady and dynamic hydrogeological conditions. The effect of water table variations on hydrochemical, microbial and isotopic composition (δ<sup>13</sup>C and δ<sup>37</sup>Cl) was examined to derive DCM mass removal and potential changes in degradation pathways. For the latter, Compound-Stable Isotope Analysis (CSIA) has been used as a tool to evaluate natural degradation of halogenated hydrocarbons. A RTM model (CubicM) is currently being developed to include dual-element CSIA and biological processes - such as growth, decay, attachment, detachment or dormancy – and relate changes in redox conditions with the evolution of DCM degrading populations. A two-phase flow model (i.e. water and gas) has been developed to account for the volatilization and the associated transport processes of halogenated volatile compounds in porous media. Currently, the model is tested on the experimental results to assist in the interpretation of DCM dissipation and the observed biogeochemical and microbial processes to determine the best-suited formalism to address the effect of water table fluctuations on DCM reactive transport in porous media. Such model will enable to assess natural attenuation of DCM at contaminated sites accounting for dynamic hydrogeological conditions.</p>

Impact of chaotic mixing on reactive transport: experiment in porous media at high Pe and Da

2021 ◽  
Author(s):  
Hugo Sanquer ◽  
Joris Heyman ◽  
Tanguy Le Borgne ◽  
Khalil Hanna
Keyword(s):  
Porous Media ◽  
Reactive Transport ◽  
3D Imaging ◽  
Fluid Phase ◽  
Reaction Rates ◽  
Transport Processes ◽  
Chaotic Mixing ◽  
Pore Scale ◽  
Chemical Gradients ◽  
The Impact

<p>Solute transport in porous media plays a key role in a range of chemical and biological processes, including contaminant degradation, precipitation, dissolution and microbiological dynamics. Increasing evidences have shown that the conventional complete mixing assumption at the pore scale can lead to a strong overestimation of reaction rates. Recent 3D imaging experiments of mixing in porous media suggest that these pore scale chemical gradients may be sustained by chaotic mixing dynamics. However, the consequences of such chaotic mixing on reactive processes are unknown.</p><p>In this work, we use reactive transport experiments coupled to 3D imaging to investigate the impact of micro-scale chaotic flows on mixing-limited reactions in the fluid phase.  We use optical index matching and laser-induced fluorescence to characterize the pore scale distribution of reactive product concentration for a range of Peclet and Damkhöler numbers. We use these measurements to develop a reactive lamellar theory that quantifies the impact of pore scale chemical gradients induced by chaotic mixing on effective reaction rates. These results provide new perspectives for upscaling reactive transport processes in porous media.</p>

A Pore-Scale Reactive Transport Model Approach for Investigating the Effect of Soil Physical Properties on Biogeochemical Processes

2020 ◽  
Author(s):  
Amir Golparvar ◽  
Matthias Kästner ◽  
Martin Thullner
Keyword(s):  
Porous Media ◽  
Physical Properties ◽  
Vadose Zone ◽  
Reactive Transport ◽  
Soil Physical Properties ◽  
Transport Processes ◽  
Biogeochemical Processes ◽  
Pore Scale ◽  
Model Approach

<p>The vadose zone hosts a wide range of various microorganisms which provide different soil ecosystem services from nutrient cycling to biodegradation of harmful chemical substances. The efficiency of such in-situ biodegradation is influenced by different biotic and abiotic factors ranging from physical properties of the soil to the redox conditions controlled by the activity of the involved chemical compounds. One important feature of the soil system is the dynamical and simultaneous interplay of these factors, boosting or deteriorating the residing microbial community’s abundance and/or activity and hence shaping biodegradation of vadose zone contaminants. Physical properties of porous media – e.g. the pore geometry, pore size distribution, connectivity as well as the water content – play a major role in enhancing or restricting the bioavailable concentration of contaminants and other reaction partners. Pore-scale phenomena have been shown to be considerably affecting the macro-scale processes, therefore a quantitative bottom-top approach of these mechanisms in situ is adamant. Hence it is of paramount importance to understand the effect of soil physical properties on microbial activity and biodegradation of carbon compounds in soil.</p><p>Pore scale reactive transport processes have a complex, nonlinear dependency on the aforementioned factors, which severely challenges the experimental and/or numerical investigation of biodegradation at in in-situ conditions. However, the recent technological advances, specifically the imaging techniques, have made it easier to study biological and microbial evolution in porous media, but there is still a need for putting all these information together. For this purpose, numerical methods would offer the possibility of simulating a variable/controllable water saturation conditions and considering water/air dynamics and advective and diffusive micro-scale transport of all components in both, air and water phase, in porous medium structures directly obtained from CT scanned samples. Up to now, such pore-sale model approaches considering also the fate of biogeochemically reactive compounds are scarce. In this work we propose a novel reactive transport modelling technique combining the pore-scale numerical characterization of water flow and solute transport in unsaturated porous media and of biogeochemical process. For a variably saturated porous system, the presented model approach is solving the Navier Stokes equation and scalar transport equations for any arbitrary geometry and is simulating the dynamics of biogeochemical processes with any degree of complexity. Simulations are compared to experimental data to assess the effect of soil physical properties on the transport and degradation of contaminants in soil.</p>

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