Porous Medium

<p>A <b>porous medium</b> (or a <b>porous material</b>) is a <a href="http://en.wikipedia.org/wiki/Material" title="Material">material</a> containing <a href="http://en.wikipedia.org/wiki/Porosity" title="Porosity">pores</a> (voids). The skeletal portion of the material is often called the "matrix" or "frame". The pores are typically filled with a <a href="http://en.wikipedia.org/wiki/Fluid" title="Fluid">fluid</a> (<a href="http://en.wikipedia.org/wiki/Liquid" title="Liquid">liquid</a> or <a href="http://en.wikipedia.org/wiki/Gas" title="Gas">gas</a>). The skeletal material is usually a <a href="http://en.wikipedia.org/wiki/Solid" title="Solid">solid</a>, but structures like <a href="http://en.wikipedia.org/wiki/Foam" title="Foam">foams</a> are often also usefully analyzed using concept of porous media.

A porous medium is most often characterised by its <a href="http://en.wikipedia.org/wiki/Porosity" title="Porosity">porosity</a>. Other properties of the medium (e.g., <a href="http://en.wikipedia.org/wiki/Permeability_%28fluid%29" title="Permeability (fluid)" class="mw-redirect">permeability</a>, <a href="http://en.wikipedia.org/wiki/Tensile_strength" title="Tensile strength" class="mw-redirect">tensile strength</a>, <a href="http://en.wikipedia.org/wiki/Electrical_conductivity" title="Electrical conductivity" class="mw-redirect">electrical conductivity</a>) can sometimes be derived from the respective properties of its constituents (solid matrix and fluid) and the media porosity and pores structure, but such a derivation is usually complex. Even the concept of porosity is only straightforward for a poroelastic medium.

Often both the solid matrix and the pore network (also known as the pore space) are continuous, so as to form two interpenetrating continua such as in a <a href="http://en.wikipedia.org/wiki/Sponge" title="Sponge">sponge</a>. However, there is also a concept of closed porosity and <a href="http://en.wikipedia.org/wiki/Effective_porosity" title="Effective porosity">effective porosity</a>, i.e., the pore space accessible to flow.

Many natural substances such as <a href="http://en.wikipedia.org/wiki/Rock%28geology%29" title="Rock (geology)">rocks</a> and <a href="http://en.wikipedia.org/wiki/Soil" title="Soil">soil</a> (e.g., <a href="http://en.wikipedia.org/wiki/Aquifer" title="Aquifer">aquifers</a>, <a href="http://en.wikipedia.org/wiki/Petroleum_reservoir" title="Petroleum reservoir">petroleum reservoirs</a>), <a href="http://en.wikipedia.org/wiki/Zeolite" title="Zeolite">zeolites</a>, <a href="http://en.wikipedia.org/wiki/Biological_tissue" title="Biological tissue" class="mw-redirect">biological tissues</a> (e.g. <a href="http://en.wikipedia.org/wiki/Bone" title="Bone">bones</a>, <a href="http://en.wikipedia.org/wiki/Wood" title="Wood">wood</a>, <a href="http://en.wikipedia.org/wiki/Cork%28material%29" title="Cork (material)">cork</a>), and man made materials such as <a href="http://en.wikipedia.org/wiki/Cement" title="Cement">cements</a> and <a href="http://en.wikipedia.org/wiki/Ceramic" title="Ceramic">ceramics</a> can be considered as porous media. Many of their important properties can only be rationalized by considering them to be porous media.

The concept of porous media is used in many areas of applied science and engineering: <a href="http://en.wikipedia.org/wiki/Filtration" title="Filtration">filtration</a>, <a href="http://en.wikipedia.org/wiki/Mechanics" title="Mechanics">mechanics</a> (<a href="http://en.wikipedia.org/wiki/Acoustics" title="Acoustics">acoustics</a>, <a href="http://en.wikipedia.org/wiki/Geomechanics" title="Geomechanics">geomechanics</a>, <a href="http://en.wikipedia.org/wiki/Soil_mechanics" title="Soil mechanics">soil mechanics</a>, <a href="http://en.wikipedia.org/wiki/Rock_mechanics" title="Rock mechanics">rock mechanics</a>), <a href="http://en.wikipedia.org/wiki/Engineering" title="Engineering">engineering</a> (<a href="http://en.wikipedia.org/wiki/Petroleum_engineering" title="Petroleum engineering">petroleum engineering</a>, <a href="http://en.wikipedia.org/wiki/Bio-remediation" title="Bio-remediation" class="mw-redirect">bio-remediation</a>, <a href="http://en.wikipedia.org/wiki/Construction_engineering" title="Construction engineering">construction engineering</a>), <a href="http://en.wikipedia.org/wiki/Geosciences" title="Geosciences" class="mw-redirect">geosciences</a> (<a href="http://en.wikipedia.org/wiki/Hydrogeology" title="Hydrogeology">hydrogeology</a>, <a href="http://en.wikipedia.org/wiki/Petroleum_geology" title="Petroleum geology">petroleum geology</a>, <a href="http://en.wikipedia.org/wiki/Geophysics" title="Geophysics">geophysics</a>), <a href="http://en.wikipedia.org/wiki/Biology" title="Biology">biology</a> and <a href="http://en.wikipedia.org/wiki/Biophysics" title="Biophysics">biophysics</a>, <a href="http://en.wikipedia.org/wiki/Material_science" title="Material science" class="mw-redirect">material science</a>, etc. <a href="http://en.wikipedia.org/wiki/Fluid" title="Fluid">Fluid</a> <a href="http://en.wikipedia.org/wiki/Fluid_dynamics" title="Fluid dynamics">flow</a> through porous media is a subject of most common interest and has emerged a separate field of study. The study of more general behaviour of porous media involving deformation of the solid frame is called <a href="http://en.wikipedia.org/wiki/Poromechanics" title="Poromechanics">poromechanics</a>.</p>

<h2>[<a href="http://en.wikipedia.org/w/index.php?title=Porous_medium&action=edit&section=1" title="Edit section: Pore structure models">edit</a>] Pore structure models</h2>

<p>There are many idealized models of pore structures. They can be broadly divided into three categories:</p>

<ul>

<li>networks of <a href="http://en.wikipedia.org/wiki/Capillary" title="Capillary">capillaries</a>,</li>

<li>arrays of solid particles (e.g., <a href="http://en.wikipedia.org/wiki/Random_close_pack" title="Random close pack">random close pack</a> of spheres).</li>

<li>trimodal</li>

</ul>

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<p>Open cell ceramic</p>

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</li>

</ul>

<ul>

<li><a href="http://en.wikipedia.org/wiki/Nanoporous" title="Nanoporous">Nanoporous materials</a></li>

<li><a href="http://en.wikipedia.org/wiki/NMR_in_porous_media" title="NMR in porous media" class="mw-redirect">NMR in porous media</a></li>

<li><a href="http://en.wikipedia.org/wiki/Percolation_theory" title="Percolation theory">Percolation theory</a></li>

<li><a href="http://en.wikipedia.org/wiki/Reticulated_foam" title="Reticulated foam">Reticulated foam</a></li>

</ul>