Editing Capillary action (section)

== Phenomena and physics ==
[[File:Rising-damp.jpg|thumb|Moderate rising damp on an internal wall]]

[[File:Capillary Flow Experiment.jpg|thumb|Capillary flow experiment to investigate capillary flows and phenomena aboard the [[International Space Station]]]]
Capillary penetration in porous media shares its dynamic mechanism with flow in hollow tubes, as both processes are resisted by viscous forces.<ref name="cappen">{{cite journal |last1=Liu |first1=Mingchao |last2=Wu |first2=Jian |last3=Gan |first3=Yixiang |last4=Hanaor |first4=Dorian A.H. |last5=Chen |first5=C.Q. |title=Tuning capillary penetration in porous media: Combining geometrical and evaporation effects |journal=International Journal of Heat and Mass Transfer |date=August 2018 |volume=123 |pages=239–250 |doi=10.1016/j.ijheatmasstransfer.2018.02.101 |bibcode=2018IJHMT.123..239L |url=https://unsworks.unsw.edu.au/bitstreams/2f5ef787-bf87-4d2c-a9c8-70e55bcff408/download |hdl=1959.4/unsworks_60951 |hdl-access=free }}</ref> Consequently, a common apparatus used to demonstrate the phenomenon is the ''capillary tube''. When the lower end of a glass tube is placed in a liquid, such as water, a concave [[Meniscus (liquid)|meniscus]] forms. [[Adhesion]] occurs between the fluid and the solid inner wall pulling the liquid column along until there is a sufficient mass of liquid for [[gravitational force]]s to overcome these intermolecular forces. The contact length (around the edge) between the top of the liquid column and the tube is proportional to the radius of the tube, while the weight of the liquid column is proportional to the square of the tube's radius. So, a narrow tube will draw a liquid column along further than a wider tube will, given that the inner water molecules cohere sufficiently to the outer ones.{{cn|date=January 2025}}