Editing Granular convection (section)

==Applications==

===Manufacturing===
[[File:Raisin Bran Cereal in box (38390064056).jpg|alt=Raisins and bran flakes, inside a cereal box.  Multiple raisins are visible on top of the flakes|thumb|This phenomenon results in [[Raisin|raisins]] tending to rise to the top of a box of [[breakfast cereal]], so that the first servings of the cereal contain more raisins than usual, and only flakes are left at the bottom of the box.]]

The effect is of interest to food manufacturing and similar operations.<ref name=":0" /> Once a homogeneous mixture of granular materials has been produced, it is usually undesirable for the different particle types to segregate.  Several factors determine the severity of the Brazil nut effect, including the sizes and [[density|densities]] of the particles, the [[pressure]] of any [[gas]] between the particles, and the shape of the container. A rectangular box (such as a box of [[breakfast cereal]]) or [[cylinder (geometry)|cylinder]] (such as a can of nuts) works well to favour the effect,{{Citation needed|date=February 2008}} while a container with outwardly slanting walls (such as in a conical or spherical geometry) results in what is known as the '''reverse Brazil nut effect'''.<ref>{{Cite journal|last1=Knight|first1=James B.|last2=Jaeger|first2=H. M.|last3=Nagel|first3=Sidney R.|date=1993-06-14|title=Vibration-induced size separation in granular media: The convection connection|journal=Physical Review Letters|language=en|volume=70|issue=24|pages=3728–3731|doi=10.1103/PhysRevLett.70.3728|pmid=10053947|bibcode=1993PhRvL..70.3728K|issn=0031-9007}}</ref>

===Astronomy===
In [[astronomy]], it is common in low density, or [[rubble pile]] [[asteroid]]s, for example the asteroid [[25143 Itokawa]]<ref>{{Cite APOD |date=22 April 2007 |title=Smooth Sections of Asteroid Itokawa |access-date=}}</ref> and [[101955 Bennu]].<ref>{{cite journal|arxiv=2002.01468|doi=10.1016/j.icarus.2020.113963 |pmc=7571586|title=Ricochets on asteroids: Experimental study of low velocity grazing impacts into granular media|year=2020|last1=Wright|first1=Esteban|last2=Quillen|first2=Alice C.|last3=South|first3=Juliana|last4=Nelson|first4=Randal C.|last5=Sánchez|first5=Paul|last6=Siu|first6=John|last7=Askari|first7=Hesam|last8=Nakajima|first8=Miki|last9=Schwartz|first9=Stephen R.|s2cid=219965690|journal=Icarus|volume=351|page=113963|pmid=33087944 |bibcode=2020Icar..35113963W}}</ref>

===Geology===
In [[geology]], the effect is common in formerly glaciated areas such as [[New England]] and areas in regions of [[permafrost]] where the landscape is shaped into [[hummocks]] by [[frost heave]] — new stones appear in the fields every year from deeper underground. [[Horace Greeley]] noted "Picking stones is a never-ending labor on one of those New England farms. Pick as closely as you may, the next plowing turns up a fresh eruption of boulders and pebbles, from the size of a hickory nut to that of a tea-kettle."<ref>[http://www.osv.org/school/lesson_plans/ShowLessons.php?PageID=P&LessonID=34&DocID=96 excerpt from ''Recollections of a Busy Life''] {{webarchive|url=https://archive.today/20120910004003/http://www.osv.org/school/lesson_plans/ShowLessons.php?PageID=P&LessonID=34&DocID=96 |date=2012-09-10 }}, by Horace Greeley 1869</ref> A hint to the cause appears in his further description that "this work is mainly to be done in March or April, when the earth is saturated with ice-cold water". Underground water freezes, lifting all particles above it.  As the water starts to melt, smaller particles can settle into the opening spaces while larger particles are still raised.  By the time ice no longer supports the larger rocks, they are at least partially supported by the smaller particles that slipped below them.  Repeated freeze-thaw cycles in a single year speeds up the process.

This phenomenon is one of the causes of [[Graded bedding|inverse grading]] which can be observed in many situations including [[soil liquefaction]] during [[earthquake]]s or [[Mass wasting#Flows|mudslides]]. [[Liquefaction]] is a general phenomenon where a mixture of fluid and granular material subjected to vibration ultimately leads to circulation patterns similar to both fluid convection and granular convection. Indeed, liquefaction is fluid-granular convection with circulation patterns which are known as [[Sand boil|sand boils]] or sand volcanoes in the study of soil liquefaction.<ref>{{Cite journal |last=Taslimian |first=Rohollah |date=2024 |title=Turbulent-Fluid-Based Simulation of Dynamic Liquefaction Using Large Deformation Analysis of Solid Phase |url=https://thescipub.com/abstract/ajeassp.2024.51.55 |journal=American Journal of Engineering and Applied Sciences |language=en |volume=17 |issue=2 |pages=51–55 |doi= |issn=1941-7039}}</ref> Granular convection is also exemplified by [[debris flow]], which is a fast moving, liquefied landslide of unconsolidated, saturated debris that looks like flowing concrete. These flows can carry material ranging in size from clay to boulders, including woody debris such as logs and tree stumps. Flows can be triggered by intense rainfall, glacial melt, or a combination of the two.{{Cn|date=March 2025}}