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Deborah Number

 

Deborah Number formula

\( De \;=\; \dfrac{  t_r }{ t_o }\)     (Deborah Number)

\( t_r \;=\; De \cdot t_o  \)

\( t_o \;=\;  \dfrac{ t_r }{ De }\)

Symbol English Metric
\( De \) = Deborah Number \(dimensionless\) \(dimensionless\)
\( t_r \) = Material Relaxation Time \(sec\) \(s\)
\( t_o \) = Observation Time \(sec\) \(s\)

Deborah number, abbreviated as De, a dimensionless number, is used in fluid dynamics to describe the relative importance of elastic and viscous effects in a viscoelastic material or fluid.  It characterizes the behavior of materials that exhibit both viscous (flow-like) and elastic (solid-like) properties.  The Deborah number helps to understand whether a material will behave more elastically or more viscously under a given set of conditions.

Deborah Number Interpretation

  • Low Deborah Number (De << 1)  -  Elastic effects dominate, and the material behaves more like a solid, exhibiting elastic deformation.
  • Intermediate Deborah Number (De ≈ 1)  -  The material exhibits both elastic and viscous behaviors, and the response is a combination of the two.
  • High Deborah Number  (De >> 1)  -  Viscous effects dominate, and the material behaves more like a fluid, exhibiting flow behavior.

The Deborah number is commonly used in the study of polymers, gels, and other viscoelastic materials, as well as in various industrial applications such as the design of materials for controlled damping, vibration isolation, and other mechanical properties.

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