Deborah number
84397
224240673
2008-07-07T23:16:39Z
SmackBot
433328
Date the maintenance tags or general fixes
{{Unreferenced|date=July 2008}}
The '''Deborah number''' is a [[dimensionless number]], used in [[rheology]] to characterize how "fluid" a material is. Even some apparent solids "flow" if they are observed long enough; the origin of the name, coined by Prof. [[Markus Reiner]], is the line "The mountains flowed before the Lord" in a song by prophetess [[Deborah]] recorded in the [[Bible]] ([[Book of Judges|Judges]] 5:5).
Formally, the Deborah number is defined as the ratio of a [[relaxation time]], characterizing the intrinsic fluidity of a material, and the characteristic time scale of an experiment (or a computer simulation) probing the response of the material. The smaller the Deborah number, the more fluid the material appears.
The equation is thus:
:<math> \mathrm{De} = \frac{t_\mathrm{c}}{t_\mathrm{p}}</math>
where ''t''<sub>c</sub> refers to the relaxation time scale and ''t''<sub>p</sub> refers to the time scale of observation.
{{NonDimFluMech}}
[[Category:Dimensionless numbers]]
[[Category:Fluid mechanics]]
[[ca:nombre de Deborah]]
[[de:Deborah-Zahl]]
[[es:Número de Deborah]]
[[fr:Nombre de Deborah]]
[[ko:데보라 수]]
[[it:Numero di Deborah]]
[[pl:Liczba Debory]]