Talk:Granular convection

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A fact from Granular convection appeared on Wikipedia's Main Page in the Did you know column on 2 June 2004. The text of the entry was as follows:

Did you know... that the Brazil nut effect, a law of physics, dictates that when a mixture of granular material is shaken the biggest particles end up on the top?

A record of the entry may be seen at Wikipedia:Recent additions/2004/June.

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The bit about a cereal box helping to combat the Brazil nut effect; is that actually true? Where is the cite? (Have added a {{Fact}} tag). 163.1.167.122 (talk) 22:18, 3 February 2008 (UTC)[reply]

In the photo of the mixed nuts on a flat surface all the nuts are unshelled except the Brazil nut. For purposes of comparison it might be better of all the nuts were either shelled or unshelled.

This is probably not correct in the explanation section:

"The center of mass of the whole system (containing the mixed nuts) in an arbitrary state is not optimally low; it has the tendency to be higher due to there being more empty space around the larger Brazil nuts than around smaller nuts. [citation needed]"

-ok, that's probable correct, but:

"When the nuts are shaken, the system has the tendency to move to a lower energy state, which means moving the center of mass down by moving the smaller nuts down and thereby the Brazil nuts up"

-and this second section is probably incorrect since by moving the Brazil nuts up, you actually moves the system to a higher energy state, since the nuts has similar densities but the big nuts is compact with no open spaces and the volume of the brazil nut - on their way up - is replaced with a volume with lower weight further below. 2001:4643:EBFE:0:2C97:D89E:101E:8892 (talk) —Preceding undated comment added 21:03, 22 July 2016 (UTC)[reply]

Hoagy Solanumy 13:01, 22 April 2007 (UTC)[reply]

Hi

I don't think that the revised sentence did have the same meaning, because in the newer version it's not clear what the counterintuitive behaviour is. The older version makes it clear that the odd thing is the heavier particles ending up on top.

I'll revert but I reckon the sentence could be improved nontheless.

best wishes

Robinh 07:06, 26 August 2005 (UTC)[reply]

There should be a link to the Brazil Nut article from the words "Brazil nuts" at the end of the first paragraph.

The picture of the lone Brazil nut should be labled Brazil nut in the shell or a picture of a shelled Brazil nut should be found.

--64.144.5.34 18:37, 22 April 2007 (UTC)[reply]

Geology

In geology, we call this inverse grading (as opposed to normal grading which is when the finer grains are on the top). Where does the name "Brazil nut effect" come from? Is this the official name for this phenomenon in certain areas of research? --Hamsterlopithecus (talk) 23:53, 8 March 2010 (UTC)[reply]

Credible?

I don't find this article credible. This article states that the density is not a factor. That is ridiculous. This article needs far better references to be credible. Keep in mind that the effect has major commercial and geological consequences, and certainly has been studied in great detail. I saw an article about a year ago which named the effect citing surface area (I believe, but am not sure, that frictional forces were invoked). Note that this article does not mention friction or surface area. Note also that by simply placing the particulates under vacuum, explanations involving air would be either confirmed or rejected, no speculation would be necessary. I conclude that the quality of this article is insufficient for it to be credible. Readers should beware. Note also that by definition convection is a cyclical process, convective cells circulate. The Brazil Nut effect is obviously not a circulation as once the particles have partitioned by size no further flow will occur.Abitslow (talk) 15:25, 17 November 2013 (UTC)[reply]

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I don't think the article should be called "granular convection".

I think "granular segregation" is a more appropriate term. "Granular convection" is just a mechanism in the process of granular segregation (also known as the Brazil nut effect). It is possible for the phenomenon to take place even without convection rolls.