scholarly journals A pore network study of evaporation from the surface of a drying non-hygroscopic porous medium

AIChE Journal ◽  
2017 ◽  
Vol 64 (4) ◽  
pp. 1435-1447 ◽  
Author(s):  
Alireza Attari Moghaddam ◽  
Abdolreza Kharaghani ◽  
Evangelos Tsotsas ◽  
Marc Prat
Keyword(s):  
Porous Medium ◽  
Pore Network

The impact of porosity on organic matter cycling in a two-dimensional porous medium 

2021 ◽  
Author(s):  
Hanbang Zou ◽  
Pelle Ohlsson ◽  
Edith Hammer
Keyword(s):  
Porous Medium ◽  
Organic Matter ◽  
Carbon Sequestration ◽  
Soil Carbon ◽  
Pore Network ◽  
Pore Scale ◽  
Decomposition Of Organic Matter ◽  
Organic Matter Cycling ◽  
The Impact

<p>Carbon sequestration has been a popular research topic in recent years as the rapid elevation of carbon emission has significantly impacted our climate. Apart from carbon capture and storage in e.g. oil reservoirs, soil carbon sequestration offers a long term and safe solution for the environment and human beings. The net soil carbon budget is determined by the balance between terrestrial ecosystem sink and sources of respiration to atmospheric carbon dioxide. Carbon can be long term stored as organic matters in the soil whereas it can be released from the decomposition of organic matter. The complex pore networks in the soil are believed to be able to "protect" microbial-derived organic matter from decomposition. Therefore, it is important to understand how soil structure impacts organic matter cycling at the pore scale. However, there are limited experimental studies on understanding the mechanism of physical stabilization of organic matter. Hence, my project plan is to create a heterogeneous microfluidic porous microenvironment to mimic the complex soil pore network which allows us to investigate the ability of organisms to access spaces starting from an initial ecophysiological precondition to changes of spatial accessibility mediated by interactions with the microbial community.</p><p>Microfluidics is a powerful tool that enables studies of fundamental physics, rapid measurements and real-time visualisation in a complex spatial microstructure that can be designed and controlled. Many complex processes can now be visualized enabled by the development of microfluidics and photolithography, such as microbial dynamics in pore-scale soil systems and pore network modification mimicking different soil environments – earlier considered impossible to achieve experimentally. The microfluidic channel used in this project contains a random distribution of cylindrical pillars of different sizes so as to mimic the variations found in real soil. The randomness in the design creates various spatial availability for microbes (preferential flow paths with dead-end or continuous flow) as an invasion of liquids proceeds into the pore with the lowest capillary entry pressure. In order to study the impact of different porosity in isolation of varying heterogeneity of the porous medium, different pore size chips that use the same randomly generated pore network is created. Those chips have the same location of the pillars, but the relative size of each pillar is scaled. The experiments will be carried out using sterile cultures of fluorescent bacteria, fungi and protists, synthetic communities of combinations of these, or a whole soil community inoculum. We will quantify the consumption of organic matter from the different areas via fluorescent substrates, and the bio-/necromass produced. We hypothesise that lower porosity will reduce the net decomposition of organic matter as the narrower pore throat limits the access, and that net decomposition rate at the main preferential path will be higher than inside branches</p>

scholarly journals Kinematics in a slowly drying porous medium: Reconciliation of pore network simulations and continuum modeling

2017 ◽  
Vol 29 (2) ◽  
pp. 022102 ◽  
Author(s):  
Alireza Attari Moghaddam ◽  
Abdolreza Kharaghani ◽  
Evangelos Tsotsas ◽  
Marc Prat
Keyword(s):  
Porous Medium ◽  
Pore Network ◽  
Continuum Modeling ◽  
Network Simulations

Dipolar Energy Transfer and Knudsen Diffusion Inside Disordered Porous Media: Interfacial Geometry and Chord Distributions.

1992 ◽  
Vol 290 ◽  
Author(s):  
P. Levitz
Keyword(s):  
Porous Medium ◽  
Energy Transfer ◽  
Hard Spheres ◽  
Knudsen Diffusion ◽  
Pore Network ◽  
Distribution Functions ◽  
Transport Processes ◽  
Distribution Model ◽  
Solid Matrix ◽  
Quenching Efficiency

AbstractThe interfacial geometry of a disordered porous medium strongly influences Knudsen diffusion of gases and interfacial dipolar energy transfer. Some interesting comparison can be made between these two transport processes, involving statistical properties of chords belonging either to the solid matrix or to the pore network. A quantitative analysis of these two mechanisms is proposed, based on a chord distribution model. In a first part, we discuss how chord distribution functions contribute to the stastistical characterization of a porous medium. We show that a direct connection between imaging techniques and small angle scattering provides, in many cases, a reliable description of theses functions. In a second part, interfacial direct energy transfer is analyzed. This one step excitation transfer strongly relies on the interfacial autocorrelation function φ2s(r). An analytic expression of φ2s(r) is given and theoretical predictions compared with available experiments. In a third part and following the seminal work of Derjaguin on the Knudsen diffusion, we critically examine how the self diffusion coefficient can be related to the two first moments of the pore chord distribution. A direct comparison with experimental results and numerical simulations is presented in the case of a model porous medium: the random packing of hard spheres. Finally, we analyze a trapping reaction where an excited gas molecule, diffusing in the Knudsen regime, relaxes primarily by wall effects. We show how the chord distribution of the pore network permits to compute the survival probability of the tagged molecules. Two situations are more closely analyzed: the strong and the very weak wall quenching efficiency.

scholarly journals The Role of Discrete Capillary Rings in Mass Transfer From the Surface of a Drying Capillary Porous Medium

2021 ◽  
Author(s):  
Hafiz Tariq Mahmood ◽  
Evangelos Tsotsas ◽  
Abdolreza Kharaghani
Keyword(s):  
Porous Medium ◽  
Mass Exchange ◽  
Exchange Process ◽  
Three Dimensional ◽  
Network Models ◽  
Pore Network ◽  
Liquid Films ◽  
Pore Network Model ◽  
Mass Exchange Process ◽  
Limiting Condition

AbstractThe mass exchange between the surface of a model capillary porous medium and the adjacent gas-side boundary layer is studied in the limiting condition of isothermal, slow drying. In order to quantify the role and significance of liquid films in the mass exchange process, three-dimensional pore network Monte Carlo simulations are carried out systematically in the presence and absence of discrete capillary rings. The pore network simulations performed with capillary rings show a noticeable delay in transition from the capillary-supported regime to the diffusion-controlled regime. These simulation results differ significantly from the predictions of classical pore network models without liquid films, and they appear to be more consistent with the experiments conducted with real porous systems. As compared to classical pore network models, the pore network model with rings seems to predict favorably the spatiotemporal evolution of wet and dry patches at the medium surface as well as of their relative contributions to the net mass exchange rate. This is apparent when the analytical solution of the commonly used Schlünder’s model is examined against the numerical simulations conducted using classical and ring pore network models.

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