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23Na
Published in Guillaume Madelin, X-Nuclei Magnetic Resonance Imaging, 2022
Porous media. Porous media are materials containing pores, typically filled with liquids or gases. Porous media can be found in many natural materials (rocks, soil, zeolites), biological tissues (bones, wood), and artificial materials (ceramics). Their main properties, such as porosity, permeability, tensile strength, electrical conductivity, tortuosity, wettability, have been extensively studied with 1H NMR (relaxation, line broadening, diffusion) [242]. 23Na NMR has also been proposed to analyze porous media samples, taking advantage of the complex relaxation processes involved for quadrupolar sodium spins 32 in salt solution within the pores, which involve local electric field gradients, and that can be used to probe fluid transport and porous structure [243].
Hydrogeology
Published in Mohammad Albaji, Introduction to Water Engineering, Hydrology, and Irrigation, 2022
Porosity (n) is a directly measurable property of aquifer that describes the fraction of void space in the material, where the void may contain, for example, air or water. This parameter is used in hydrogeology, geology, soil science, and building science. The porosity of a porous medium is a fraction between 0 and 1 that is defined by the ratio:n=VVVTwhere VV is the volume of void-space and VT is the total or bulk volume of material, including the solid and void components.
Permeability of Soils and Rocks
Published in Pat M. Cashman, Martin Preene, Groundwater Lowering in Construction, 2020
Permeability was introduced in Chapter 3 as part of the formulation of Darcy’s law. In essence, permeability is a measure of the ease or otherwise with which a fluid passes through a porous medium. A complication is that the ease of flow is dependent not only on the nature of the porous media but also on the properties of the permeating fluid. In other words, the permeability of a soil or rock to water is different from the permeability to another fluid, such as air or oil (the permeability parameter, independent of the fluid, is known as the intrinsic permeability of a material). Hydrogeology references highlight this by using the term ‘hydraulic conductivity’ to show that the permeability parameter used is specific to water. As a reminder of terminology, this book follows geotechnical engineering practice and uses the term ‘permeability’ to mean hydraulic conductivity, coefficient of permeability or Darcy’s permeability, which applies specifically in relation to the flow of water through porous media.
A study of Cu/Ag nanoparticle shape-augmented heat transfer in Darcy–Brinkman–Forchheimer flow in a square cavity
Published in Waves in Random and Complex Media, 2023
B. Mallikarjuna, B. V. Rathish Kumar
Another attractive tool to enhance heat transfer in industrial and engineering fields is the usage of porous media, for example, the application of metal-based porous materials such as copper or aluminum foams in channels and heat exchangers. Porous media is a material containing pores, which are connected and filled with the base fluid completely; therefore, the fluid can flow through pores. Darcy first describes the flow in porous media with some limitations. The same is modified by Forchheimer and Brinkmann, which corresponds to inertia, and viscous drag effects appear in the momentum equation. This equation can be referred to as the Darcy–Brinkman–Forchheimer equation, which can be found in the literature [25, 26]. The existing literature comprehended on this topic is found in the published monograph by Nield and Bejan [27].
Importance of appropriate segmentation in pore structure analysis of coral reef limestone from CT images
Published in Marine Georesources & Geotechnology, 2023
Hanbo Wan, Xin Huang, Junpeng Wang, Zixin Zhang
There is a general consensus that the physical and mechanical properties of porous media are closely related to their pore structure features. Some researchers have confirmed that the microstructure characteristics of porous rocks, such as the pore shape, could influence the overall mechanical properties of rocks, including the strength, stiffness, bulk modulus and Biot coefficient (Griffiths et al. 2017; Selvadurai and Suvorov 2020). The structural features could also influence the macroscale flow and transport phenomena inside, which thereby determines the permeability and seepage characteristics (Patmonoaji, Tsuji, and Suekane 2020; Ibrahim et al. 2019). Zhang, Ye, and Fu (2021) found that the aperture of the conduit plays a dominant role in the equivalent permeability coefficient (the average permeability of the whole rock volume) in porous rocks. Xie et al. (2022) concluded that under normal conditions, tight sandstone samples with lower connectedness, fewer intergranular dominant pores, and smaller grain sizes showed greater P-wave velocities and S-wave velocities, and vice versa.
Computational fluid dynamics analysis and extended adaptive hybrid functions model-based design optimization of an explosion-proof safety valve
Published in Engineering Applications of Computational Fluid Mechanics, 2022
Chaoyong Zong, Qingye Li, Kunpeng Li, Xueguan Song, Dianjing Chen, Xiaofeng Li, Xuebin Wang
The principle of the equivalent porous method is to use appropriate porous media to simulate the blocking effects of the solid structures on fluid flow. Porous media refers to a combination of multiphase substances with complex internal structures and a large number of voids, such as coal, wood, filters, soil layers and catalytic beds. For CFD model development, directly modeling porous media will require a lot of grids and huge computing resources, which is difficult to use in practical engineering situations. To overcome this, a compromise method is to replace the actual structure with an analytical model, as shown in Figure 6. The flame-retardant sheet of the explosion-proof safety valve system in this paper is made up of five circular screens, in a staggered arrangement. It can be assumed to be a porous medium, and the momentum loss of the flame-retardant sheet system to fluid flow can be calculated based on the permeability and porosity.