Deborah Number
On one end of the spectrum we have an inviscid or a simple Newtonian fluid and on the other end, a rigid solid; thus the behaviour of all materials fall somewhere in between these two ends. The difference in material behaviour is characterized by the level and nature of elasticity present in the material when it deforms, which takes the material behaviour to the non-Newtonian regime. The non-dimensional Deborah number is designed to account for the degree of non-Newtonian behaviour in a flow. The Deborah number is defined as the ratio of the characteristic time of relaxation (which purely depends on the material and other conditions like the temperature) to the characteristic time of experiment or observation. Small Deborah numbers represent Newtonian flow, while non-Newtonian (with both viscous and elastic effects present) behaviour occurs for intermediate range Deborah numbers, and high Deborah numbers indicate an elastic/rigid solid. Since Deborah number is a relative quantity, the numerator or the denominator can alter the number. A very small Deborah number can be obtained for a fluid with extremely small relaxation time or a very large experimental time, for example.
Read more about this topic: Rheology, Dimensionless Numbers
Famous quotes containing the words deborah and/or number:
“Q: What would have made a family and career easier for you?
A: Being born a man.”
—Anonymous Mother, U.S. physician and mother of four. As quoted in Women and the Work Family Dilemma, by Deborah J. Swiss and Judith P. Walker, ch. 2 (1993)
“In view of the fact that the number of people living too long has risen catastrophically and still continues to rise.... Question: Must we live as long as modern medicine enables us to?... We control our entry into life, it is time we began to control our exit.”
—Max Frisch (1911–1991)