Editing Convection (section)

{{Short description|Fluid flow that occurs due to heterogeneous fluid properties and body forces}}
{{distinguish|Conviction}}
[[File:Convection-snapshot.png|thumb|400px|right|Simulation of thermal convection in the [[Earth's mantle]]. Hot areas are shown in red, cold areas are shown in blue. A hot, less-dense material at the bottom moves upwards, and likewise, cold material from the top moves downwards.]]

'''Convection''' is single or [[Multiphase flow|multiphase]] [[fluid flow]] that occurs [[Spontaneous process|spontaneously]] through the combined effects of [[material property]] [[heterogeneity]] and [[body forces]] on a [[fluid]], most commonly [[density]] and [[gravity]] (see [[buoyancy]]). When the cause of the convection is unspecified, convection due to the effects of [[thermal expansion]] and buoyancy can be assumed. Convection may also take place in soft [[solids]] or [[mixtures]] where particles can flow.

[[File:Ghillie Kettle Thermal.jpg|thumb|Thermal image of a newly lit [[Kelly Kettle|Ghillie kettle]]. The plume of hot air resulting from the convection current is visible.]]Convective flow may be [[Transient state|transient]] (such as when a [[Multiphasic liquid|multiphase]] [[mixture]] of [[oil]] and [[water]] separates) or [[steady state]] (see [[convection cell]]). The convection may be due to [[Gravity|gravitational]], [[Electromagnetism|electromagnetic]] or [[Fictitious force|fictitious]] body forces. [[Convection (heat transfer)|Heat transfer by natural convection]] plays a role in the structure of [[Earth's atmosphere]], its [[oceans]], and its [[Earth's mantle|mantle]]. Discrete convective cells in the atmosphere can be identified by [[clouds]], with stronger convection resulting in [[thunderstorm]]s. Natural convection also plays a role in [[stellar physics]]. Convection is often categorised or described by the main effect causing the convective flow; for example, thermal convection.

Convection cannot take place in most solids because neither bulk current flows nor significant [[diffusion]] of matter can take place. 
[[Granular convection]] is a similar phenomenon in [[granular material]] instead of fluids.
[[Advection#Distinction between advection and convection|Advection]] is the transport of any substance or quantity (such as heat) through fluid motion.
Convection is a process involving bulk movement of a fluid that usually leads to a net transfer of heat through advection. [[Convective heat transfer]] is the intentional use of convection as a method for [[heat transfer]].