Changes

[[File:lighterstill.jpg]][[File:SHA-POROSITY.jpg|right|frame]]

[[File:lighterstill.jpg]][[File:SHA-POROSITY.jpg|right|frame]]

*[http://en.wikipedia.org/wiki/14th_century]

*[https://en.wikipedia.org/wiki/14th_century]

==Definitions==

==Definitions==

*1a : possessing or full of pores

*1a : possessing or full of pores

*3: capable of being [[penetrated]] <porous national boundaries>  

*3: capable of being [[penetrated]] <porous national boundaries>  

==Description==

==Description==

'''Porosity''' or ''void fraction'' is a measure of the void (i.e., "empty") spaces in a [[material]], and is a fraction of the [[volume]] of voids over the total volume, between 0–1, or as a percentage between 0–100%. The term is used in multiple fields including pharmaceutics, ceramics, metallurgy, materials, manufacturing, [[earth science]]s, [http://en.wikipedia.org/wiki/Soil_mechanics soil mechanics] and [http://en.wikipedia.org/wiki/Engineering engineering].

'''Porosity''' or ''void fraction'' is a measure of the void (i.e., "empty") spaces in a [[material]], and is a fraction of the [[volume]] of voids over the total volume, between 0–1, or as a percentage between 0–100%. The term is used in multiple fields including pharmaceutics, ceramics, metallurgy, materials, manufacturing, [[earth science]]s, [https://en.wikipedia.org/wiki/Soil_mechanics soil mechanics] and [https://en.wikipedia.org/wiki/Engineering engineering].

In gas-liquid [http://en.wikipedia.org/wiki/Two-phase_flow two-phase flow], the void fraction is defined as the fraction of the flow-[[channel]] volume that is occupied by the gas phase or, alternatively, as the fraction of the cross-sectional area of the channel that is occupied by the gas phase. Void fraction usually varies from location to location in the flow channel (depending on the two-phase [[flow]] pattern). It fluctuates with [[time]] and its [[value]] is usually time averaged. In separated (i.e., non-homogeneous) flow, it is related to volumetric flow rates of the [[gas]] and the [[liquid]] phase, and to the [[ratio]] of the [[velocity]] of the two phases (called ''[http://en.wikipedia.org/wiki/Slip_ratio_(gas-liquid_flow) slip ratio)]''.

In gas-liquid [https://en.wikipedia.org/wiki/Two-phase_flow two-phase flow], the void fraction is defined as the fraction of the flow-[[channel]] volume that is occupied by the gas phase or, alternatively, as the fraction of the cross-sectional area of the channel that is occupied by the gas phase. Void fraction usually varies from location to location in the flow channel (depending on the two-phase [[flow]] pattern). It fluctuates with [[time]] and its [[value]] is usually time averaged. In separated (i.e., non-homogeneous) flow, it is related to volumetric flow rates of the [[gas]] and the [[liquid]] phase, and to the [[ratio]] of the [[velocity]] of the two phases (called ''[https://en.wikipedia.org/wiki/Slip_ratio_(gas-liquid_flow) slip ratio)]''.

Used in geology, hydrogeology, soil science, and building science, the ''porosity'' of a porous [[medium]] (such as rock or sediment) [[describes]] the [[fraction]] of void space in the [[material]], where the void may contain, for example, [[air]] or [[water]]. [http://en.wikipedia.org/wiki/Porous]

Used in geology, hydrogeology, soil science, and building science, the ''porosity'' of a porous [[medium]] (such as rock or sediment) [[describes]] the [[fraction]] of void space in the [[material]], where the void may contain, for example, [[air]] or [[water]]. [https://en.wikipedia.org/wiki/Porous]

[[Category: Earth Science]]

[[Category: Earth Science]]