Permeability (porous media)

In <a href="/facts/Fluid_mechanics/NIy4tRfE">fluid mechanics</a>, <a href="/facts/Materials_science/N5HrXRYW">materials science</a> and <a href="/facts/Earth_science/rQsXCSbM">Earth sciences</a>, the permeability of <a href="/facts/Porous_media/KTMRISJf">porous media</a> (often, a <a href="/facts/Rock_(geology)/FXCJkmop">rock</a> or <a href="/facts/Soil/5Ddpr3QM">soil</a>) is a measure of the ability for fluids (gas or liquid) to flow through the media; it is commonly symbolized as k.
Fluids can more easily flow through a material with high permeability than one with low permeability. 
The permeability of a medium is related to the <a href="/facts/Porosity/UoyAJU8X">porosity</a>, but also to the shapes of the pores in the medium and their level of connectedness. 
Fluid flows can also be influenced in different <a href="/facts/Lithology/WLIJXzGj">lithological settings</a> by brittle deformation of rocks in <a href="/facts/Fault_(geology)/0Fw2ladx">fault zones</a>; the mechanisms by which this occurs are the subject of <a href="/facts/Fault_zone_hydrogeology/dHlfy2NF">fault zone hydrogeology</a>. Permeability is also affected by the pressure inside a material.
The <a href="/facts/International_System_of_Units/S7YLglNz">SI</a> unit for permeability is the <a href="/facts/Square_metre/u5nT9y0W">square metre</a> (m2). A practical unit for permeability is the <a href="/facts/Darcy_(unit)/Tgrxrh97">darcy</a> (d), or more commonly the millidarcy (md) (1 d ≈ 10−12 m2). The name honors the French Engineer <a href="/facts/Henry_Darcy/rl7Pc4rq">Henry Darcy</a> who first described the flow of water through sand filters for potable water supply. Permeability values for most materials commonly range typically from a fraction to several thousand millidarcys. The unit of square centimetre (cm2) is also sometimes used (1 cm2 = 10−4 m2 ≈ 108 d).

Permeability (porous media) open-in-new

Permeability (porous media)