Editing Convection (section)

===Water convection at freezing temperatures===
[[Water]] is a fluid that does not obey the Boussinesq approximation.<ref name=":0">{{Cite journal|last1=Banaszek|first1=J.|last2=Jaluria|first2=Y.|last3=Kowalewski|first3=T. A.|last4=Rebow|first4=M.|date=1999-10-01|journal=Numerical Heat Transfer, Part A: Applications|language=en|volume=36|issue=5|pages=449–472|doi=10.1080/104077899274624|issn=1040-7782|title=Semi-Implicit Fem Analysis of Natural Convection in Freezing Water|bibcode=1999NHTA...36..449B|s2cid=3740709 }}</ref> This is because its density varies nonlinearly with temperature, which causes its thermal expansion coefficient to be inconsistent near freezing temperatures.<ref>{{Cite web|url=https://www.engineeringtoolbox.com/water-density-specific-weight-d_595.html|title=Water - Density, Specific Weight and Thermal Expansion Coefficient|website=www.engineeringtoolbox.com|language=en|access-date=2018-12-01}}</ref><ref name=":1">{{Cite news|url=http://polymer.bu.edu/hes/articles/ds03.pdf |archive-url=https://web.archive.org/web/20060301224729/http://polymer.bu.edu/hes/articles/ds03.pdf |archive-date=2006-03-01 |url-status=live|title=Supercooled and Glassy Water|last1=Debenedetti|first1=Pablo G.|date=June 2003|work=Physics Today|access-date=1 December 2018|last2=Stanley|first2=H. Eugene}}</ref> The [[density of water]] reaches a maximum at 4&nbsp;°C and decreases as the temperature deviates. This phenomenon is investigated by experiment and numerical methods.<ref name=":0" /> Water is initially stagnant at 10&nbsp;°C within a square cavity. It is differentially heated between the two vertical walls, where the left and right walls are held at 10&nbsp;°C and 0&nbsp;°C, respectively.  The density anomaly manifests in its flow pattern.<ref name=":0" /><ref>{{Cite journal|last1=Giangi|first1=Marilena|last2=Stella|first2=Fulvio|last3=Kowalewski|first3=Tomasz A.|date=December 1999|title=Phase change problems with free convection: fixed grid numerical simulation|journal=Computing and Visualization in Science|language=en|volume=2|issue=2–3|pages=123–130|doi=10.1007/s007910050034|issn=1432-9360|citeseerx=10.1.1.31.9300|s2cid=3756976 }}</ref><ref>{{Cite journal|last1=Tong|first1=Wei|last2=Koster|first2=Jean N.|date=December 1993|title=Natural convection of water in a rectangular cavity including density inversion|journal=International Journal of Heat and Fluid Flow|volume=14|issue=4|pages=366–375|doi=10.1016/0142-727x(93)90010-k|bibcode=1993IJHFF..14..366T |issn=0142-727X}}</ref><ref>{{Cite journal|last1=Ezan|first1=Mehmet Akif|last2=Kalfa|first2=Mustafa|date=October 2016|title=Numerical investigation of transient natural convection heat transfer of freezing water in a square cavity|journal=International Journal of Heat and Fluid Flow|volume=61|pages=438–448|doi=10.1016/j.ijheatfluidflow.2016.06.004|bibcode=2016IJHFF..61..438E |issn=0142-727X}}</ref> As the water is cooled at the right wall, the density increases, which accelerates the flow downward. As the flow develops and the water cools further, the decrease in density causes a recirculation current at the bottom right corner of the cavity.

Another case of this phenomenon is the event of [[Supercooling|super-cooling]], where the water is cooled to below freezing temperatures but does not immediately begin to freeze.<ref name=":1" /><ref name=":2">{{Cite journal|last1=Moore|first1=Emily B.|last2=Molinero|first2=Valeria|date=November 2011|title=Structural transformation in supercooled water controls the crystallization rate of ice|journal=Nature|language=En|volume=479|issue=7374|pages=506–508|doi=10.1038/nature10586|pmid=22113691|issn=0028-0836|arxiv=1107.1622|bibcode=2011Natur.479..506M|s2cid=1784703 }}</ref> Under the same conditions as before, the flow is developed. Afterward, the temperature of the right wall is decreased to −10&nbsp;°C. This causes the water at that wall to become supercooled, create a counter-clockwise flow, and initially overpower the warm current.<ref name=":0" /> This plume is caused by a delay in the [[Nucleation of ice|nucleation of the ice]].<ref name=":0" /><ref name=":1" /><ref name=":2" /> Once ice begins to form, the flow returns to a similar pattern as before and the solidification propagates gradually until the flow is redeveloped.<ref name=":0" />