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Permeability and seepage
Published in Buddhima Indraratna, Ana Heitor, Jayan S. Vinod, Geotechnical Problems and Solutions, 2020
Buddhima Indraratna, Ana Heitor, Jayan S. Vinod
Permeability is a measure of the rate at which the fluid passes through a porous medium. For water, the apparent velocity of the flow (v) can be related to the hydraulic gradient (i) and permeability (k) via Darcy’s law, as follows: v=kdhdl=ki where dh represents the hydraulic head variation along the flow path dl.
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.
Diffusivity in Drying of Porous Media
Published in Peng Xu, Agus P. Sasmito, Arun S. Mujumdar, Heat and Mass Transfer in Drying of Porous Media, 2020
Chien Hwa Chong, Chung Lim Law, Adam Figiel, Tommy Asni
The movement of molecules in a fluid due to the concentration gradient is known as diffusion, and the degree of moisture movement of every material is known as its diffusion coefficient. Molecular diffusion occurs in various mass transfer processes, for example the drying of porous media. The molecular diffusion that occurred in drying of porous media mainly are moisture movement in liquid form. There are various types of moisture diffusion that can occur inside the structure of porous media during the drying process. Porous media have been used in many aspects of our lives, ranging from foods to building materials like wood, coal, ceramics and more. The complex structure of porous material is characterized using the term porosity. The complex structure affects the drying kinetics and characteristics of porous media. Figure 2.4 shows the entity relationship diagram (ERD) between drying technology and porous media. Physical state, structure and chemical composition of the porous media change along the drying process, for example exhibiting shrinkage, puffing, etc. The mechanisms of heat and mass transfer are affected by the changes of physical state and other properties. Considering the fact that even the same porous material will not have an identical internal structure, the data obtained from other resources may not be used directly. In addition, parameters like temperature, initial moisture content and others also affect the drying rate.
Mixed convection MHD boundary layer flow, heat, and mass transfer past an exponential stretching sheet in porous medium with temperature-dependent fluid properties
Published in Numerical Heat Transfer, Part A: Applications, 2023
Hemanta Konwar, Temjennaro Jamir
Porous medium has important applications in heat transfer processes. Porous medium acts like insulation. Heating or cooling can be controlled by porous medium. A porous medium is a material that has pores or void spaces. Materials like rocks, wood, soil, sand etc. can be considered as porous medium. Porosity and permeability are the most common characteristic of a porous material. Porosity means the quality or state of being porous and permeability measures the ease with which liquids, gases, or certain compounds may move through a substance. The study of porous media can help explain a variety of transport phenomena. Hydrology, which deals with the movement of water through earth and sand structures, is the most important area that relies on the features of porous medium. Because of its importance in petroleum technology, biochemical engineering, geophysics, nuclear reactor cooling, and other domains, transport mechanisms in porous media have received a lot of attention in recent years. Cortell [31] investigated the flow and heat transmission of a fluid through a porous material across a stretched surface with internal heat production or absorption and suction or blowing. Mukhopadhyay and Layek [32] investigated the effects of changing viscosity on flow through a heated stretched sheet embedded in a porous media in the presence of a heat source or sink. Detailed literature review can be found in the books by Pop and Ingham [33], Ingham and Pop [34], Vafai [35], Nield and Bejan [36].
Soret and Dufour effects on MHD mixed convection flow of Casson hybrid nanofluid over a permeable stretching sheet
Published in International Journal of Ambient Energy, 2023
A. R. Deepika, Kamatam Govardhan, Amalendu Rana, Motahar Reza
Figure 9 indicates that an increment in the Eckert number causes an enhancement in the temperature profile. The Eckert number represents the relationship between the kinetic energy and flow enthalpy. The larger values of the Eckert number show that the kinetic energy is higher which results in the greater vibration of fluid. This further increases the collision of fluid molecules, which leads to a rise in temperature. Figure 10 shows the variation of thermal profiles for different porous medium parameters. A porous medium is a solid, or group of solid bodies, having sufficient open spaces in or around the solids which will permit a fluid to flow through or around them. Therefore, when the porous media parameter is increased from 1 to 4, the surface area of the porous media increases, which then led to a rise in the temperature profile.
Finite element analysis of the impact of particles aggregation on the thermal conductivity of nanofluid under chemical reaction
Published in Waves in Random and Complex Media, 2023
Liaqat Ali, Bagh Ali, Taimoor Iqbal
It has been seen that a porous medium with a higher permeability also has a higher porosity value. It is observed that the boundary layer thickness enhances with the enhancement in the porosity parameter. This is because permeability variations lead to declines in heat flux, which leads to an increase in temperature gradient. The microrotation accelerates as the norms adjacent to the cylinder's surface increase, but the negative reaction is identified afield from the surface. The function of on the velocity field is included in Figure 2(d). The velocity field is shown to significantly increase with steadily rising values of λ (1 to 9). It is because the hydrostatic pressure is stronger; higher values of implicate a higher hydrostatic pressure where it coincides with a higher flow field. Figure 2(e) depicts the diminishing pattern of the velocity field across the surging Prandtl number norms, as well as the intensifying influence of flow velocity on the surging norms of the heat source parameter. It is revealed that when the heat source parameter norms increase, the temperature of the fluid boosts up. Figure 5(a–c) depicts a sequential order in the decrement of velocity with intensifying Reynolds (Re) values as well as the radiation parameter. In the thermal radiation case the effect of nanoparticle aggregation on temperature is stronger as compare non-aggregation case.