Basic Concepts

  • Werner-Michael Kulicke
  • Christian Clasen
Part of the Springer Laboratory book series (SPLABORATORY)

Abstract

The viscosity η is defined as the ratio of the shear stress σ21 and the shear rate γ̇
$$ \eta = \frac{{{\sigma _{21}}}}{{\dot \gamma }} $$
(2.1)
The shear stress σ21, as can be seen in Fig. 2.1, is the force F [N] that is exerted on the surface element A [m2] parallel to the direction of the flow:
$${\sigma _{21}} = \frac{F}{A}$$
(2.2)
The shear stress has the unit [Pa], which is the same as for a pressure. In former times, the unit [dyn/cm2] was often used:
$$1Pa = 1N/{m^2} = 10dyn/c{m^2} = 1kg/\left( {m/{s^2}} \right) $$
(2.3)
The shear rate γ̇ describes how fast the fluid layers move in respect to one another in a laminar flow profile. It is described as the ratio of the velocity difference Δv [m/s] of two fluid layers and the distance Δh between them.

Keywords

Rubber Sulfuric Acid Dichloromethane Cyclohexane Pentane 

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Copyright information

© Springer-Verlag Berlin Heidelberg 2004

Authors and Affiliations

  • Werner-Michael Kulicke
    • 1
  • Christian Clasen
    • 1
  1. 1.Fachbereich 13, Institut für Technische und Makromolekulare ChemieUniversität HamburgHamburgGermany

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