Extensional viscosity
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Extensional viscosity (also known as elongational viscosity) is a viscosity coefficient when applied stress is extensional stress.[1]
- This parameter is often used for characterizing polymer solutions.
Extensional viscosity can be measured using rheometers that apply extensional stress. Acoustic rheometer is one example of such devices.
where
- is the extensional viscosity or elongational viscosity
- is the normal stress:
- is the rate of strain:
For a Newtonian Fluid, the uniaxial elongational viscosity is three times the shear viscosity which can be derived using the continuity equation for incompressible fluids.
See also[edit]
References[edit]
- ^ Barnes, H.A. "A handbook of elementary rheology", Institute of non-Newtonian Fluid Mechanics, 2000