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| {{main|Aeolian processes}}
| | Hello friend. Let me introduce myself. I am Ron but I don't like when people use my complete name. She functions as a monetary officer and she will not alter it whenever quickly. The factor she adores most is flower arranging and she is trying to make it a occupation. My house is now in Kansas.<br><br>Look at my homepage - extended car warranty ([http://unnormal.clan.lc/index.php?mod=users&action=view&id=1612 linked webpage]) |
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| The '''Bagnold formula''', named after [[Ralph Alger Bagnold]], relates the amount of [[sand]] moved by the wind to [[wind speed]] by saltation. It states that the mass transport of sand is proportional to the third power of the [[log wind profile|friction velocity]]. Under steady conditions, this implies that mass transport is proportional to the third power of the excess of the wind speed (at any fixed height over the sand surface) over the minimum wind speed that is able to activate and sustain a continuous flow of sand grains.
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| The formula was derived by [[Ralph Alger Bagnold|Bagnold]] <ref>Bagnold, R.A. 1936. The movement of desert sand. Proceedings of the Royal Society of London A 157(892):594-620.</ref> in 1936 and later published in his book ''[[The Physics of Blown Sand and Desert Dunes]]'' <ref>Bagnold, R.A. 1941. The physics of blown sand and desert dunes. London: Methuen, 265 pp.</ref> in 1941. [[Wind tunnel]] and field experiments suggest that the formula is basically correct. It has later been modified by several researchers, but is still considered to be the benchmark formula.<ref>Greeley, R. and Iversen, J.D. 1985. Wind as a Geological Process, pp. 99 - 100, Cambridge University Press, Cambridge UK.</ref><ref>Sørensen, M. 2004. On the rate of aeolian sand transport. Geomorphology 59:53-62.</ref>
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| In its simplest form, Bagnold's formula may be expressed as:
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| :<math>q = C \ \frac{\rho}{g}\ \sqrt{\frac{d}{D}} u_*^3</math>
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| where <big>''q''</big> represents the mass ''transport'' of sand across a lane of unit width; ''C'' is a dimensionless constant of order unity that depends on the sand sorting; ''<big><math>\rho</math></big>'' is the [[density of air]]; ''g'' is the local gravitational acceleration; ''d'' is the reference grain size for the sand; ''D'' is the nearly uniform grain size originally used in Bagnold's experiments (250 micrometres); and, finally, <math>u_*</math> is [[log wind profile|friction velocity]] proportional to the square root of the shear stress between the wind and the sheet of moving sand.
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| The formula is valid in dry (desert) conditions. The effects of sand moisture at play in most coastal dunes, therefore, are not included.
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| ==See also==
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| *[[Bagnold number]]
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| *[[Saltation (geology)]]
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| *[[Aeolian processes]]
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| *[[Aeolian landform]]
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| *[[Dune]]
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| *[[Barchan]]
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| == References ==
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| {{reflist}}
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| ==External links==
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| *[http://www.lbk.ars.usda.gov/wewc/biblio/bar.htm The Bibliography of Aeolian Research]
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| [[Category:Geomorphology]]
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| {{geophysics-stub}}
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Latest revision as of 16:37, 8 August 2014
Hello friend. Let me introduce myself. I am Ron but I don't like when people use my complete name. She functions as a monetary officer and she will not alter it whenever quickly. The factor she adores most is flower arranging and she is trying to make it a occupation. My house is now in Kansas.
Look at my homepage - extended car warranty (linked webpage)