Search results
Results from the WOW.Com Content Network
Permeability is typically determined in the lab by application of Darcy's law under steady state conditions or, more generally, by application of various solutions to the diffusion equation for unsteady flow conditions. [8] Permeability needs to be measured, either directly (using Darcy's law), or through estimation using empirically derived ...
Darcy's law is an equation that describes the flow of a fluid through a porous medium and through a Hele-Shaw cell.The law was formulated by Henry Darcy based on results of experiments [1] on the flow of water through beds of sand, forming the basis of hydrogeology, a branch of earth sciences.
Thus the required pressure/flow ratio can be obtained from the ratio of the two manometer readings, and when fed into the Carman equation, yields an "absolute" value of the air permeability surface area. The apparatus is maintained at a constant temperature, and dry air is used so that the air viscosity can be obtained from tables.
Tires: Air pressure in tires should decrease as slowly as possible. A good tire is one that allows the least amount of gas to escape. Permeation will occur over time with the tires, so it is best to know the permeability of the material that will make up the tire with the desired gas to make the most efficient tires.
The movement of a fluid through porous media is described by the combination of Darcy's law with the principle of conservation of mass in order to express the capillary force or fluid velocity as a function of various other parameters including the effective pore radius, liquid viscosity or permeability. [3]
Permeability is measured in the laboratory by encasing a core plug of known length and diameter in an air-tight sleeve (the Hassler Sleeve). A fluid of known viscosity is injected into the core plug while mounted in a steel chamber. The samples are either full diameter core samples that are intervals of whole core cut, typically 6 inches long ...
In multiphase flow in porous media, the relative permeability of a phase is a dimensionless measure of the effective permeability of that phase. It is the ratio of the effective permeability of that phase to the absolute permeability. It can be viewed as an adaptation of Darcy's law to multiphase flow.
In SI units, permeability is measured in henries per meter (H/m), or equivalently in newtons per ampere squared (N/A 2). The permeability constant μ 0, also known as the magnetic constant or the permeability of free space, is the proportionality between magnetic induction and magnetizing force when forming a magnetic field in a classical vacuum.