Non-Newtonian fluids, time dependent
The viscosity of the fluid is dependent on temperature, shear rate and time.
Depending on how viscosity changes with time the
flow behaviour is characterised as:
- thixotropic (time thinning, i.e. viscosity decreases with time)
- rheopectic (time thickening, i.e. viscosity increases with time)
Thixotropic fluids are quite common in chemical as well as in food industry. Rheopectic fluids are very rare.
Note: some fluids show time thinning behaviour due to breakdown of structure. This phenomenon is sometimes known as rheomalaxis.
Examples:
- thixotropic: yoghurt, paint
- rheopectic: gypsum paste
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