Search results
Results From The WOW.Com Content Network
The permeability of a medium is related to the porosity, but also to the shapes of the pores in the medium and their level of connectedness. [2] Fluid flows can also be influenced in different lithological settings by brittle deformation of rocks in fault zones ; the mechanisms by which this occurs are the subject of fault zone hydrogeology . [ 3 ]
With reference to the diagram to the right, the flow velocity is in SI units (/), and since the porosity φ is a nondimensional number, the Darcy flux , or discharge per unit area, is also defined in units (/); the permeability in units (), the dynamic viscosity in units () and the hydraulic gradient is in units (/).
The porosity is a measure of the total pore space in the soil. This is defined as a fraction of volume often given in percent. The amount of porosity in a soil depends on the minerals that make up the soil and on the amount of sorting occurring within the soil structure.
Porosity is a fraction between 0 and 1, typically ranging from less than 0.005 for solid granite to more than 0.5 for peat and clay. The porosity of a rock, or sedimentary layer, is an important consideration when attempting to evaluate the potential volume of water or hydrocarbons it may contain.
Specifically, the Ergun equation gives the following permeability and inertial permeability from the Darcy-Forchheimer law: = (), and = . The extension of the Ergun equation to fluidized beds , where the solid particles flow with the fluid, is discussed by Akgiray and Saatçı (2001).
In case of its absence, which is common in most cases, an estimate for permeability can be derived from empirical relationships with other measurements such as porosity, NMR and sonic logging. Darcy's law [10] is applied in the laboratory to measure the core plug permeability with an inert gas or liquid (i.e. that does not react with the rock). [6]
The coefficient of permeability varies with the void ratio as e/sup>/(1+e). For a given soil, the greater the void ratio, the higher the value of the coefficient of permeability. Here 'e' is the void ratio. Based on other concepts it has been established that the permeability of a soil varies as e 2 or e 3 /(1+e). Whatever may be the exact ...
Permeation can occur through most materials including metals, ceramics and polymers. However, the permeability of metals is much lower than that of ceramics and polymers due to their crystal structure and porosity. Permeation is something that must be considered carefully in many polymer applications, due to their high permeability.