Deborah number
Physical key figure | |||||
---|---|---|---|---|---|
Surname | Deborah number | ||||
Formula symbol | |||||
dimension | dimensionless | ||||
definition | |||||
|
|||||
Named after | Debora song | ||||
scope of application | Viscoelasticity of fluids |
The Deborah number ( symbol :) is a dimensionless number of rheology . It describes the time dependence of the viscoelastic behavior of a fluid as the ratio of its relaxation time to the observation time :
In the simplest case, the relaxation time would be that from a Maxwell model of the fluid. The "observation time" can e.g. B. the inverse of a shear rate or the frequency of a mechanical excitation can be understood.
The smaller the Deborah number, the more fluid the fluid appears.
history
The inventor of the Deborah number, the Israeli rheologist Markus Reiner , referred to a passage from the Debora song : The mountains poured out before the Lord, Sinai before the Lord, the God of Israel. ( Judgment 5.5 EU ) Accordingly, the mountains are in motion in the face of God, while to human observers they appear to be solid.
Individual evidence
- ^ M. Reiner (1964) Physics Today , Vol. 17, No. 1, p. 62: The Deborah Number
literature
- John M. Dealy: Weissenberg and Deborah numbers - their Definition and Use , 2010 Rheology Bulletin 79 (2), p. 14