Thixotropy is the property of some non-Newtonian pseudoplastic fluids to show a time-dependent change in viscosity; the longer the fluid undergoes shear stress, the lower its viscosity. A thixotropic fluid is a fluid which takes a finite time to attain

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Thixotropy is the property of some non-Newtonian
pseudoplastic fluids to show a time-dependent
change in viscosity the longer the fluid
undergoes shear stress, the lower its viscosity.
A thixotropic fluid is a fluid which takes a
finite time to attain equilibrium viscosity when
introduced to a step change in shear rate.
However, this is not a universal definition the
term is sometimes applied to pseudoplastic fluids
without a viscosity/time component. Many gels and
colloids are thixotropic materials, exhibiting a
stable form at rest but becoming fluid when
agitated.
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Solve for apparent viscosity
Notice how this compares with the Hagan-
Poiseuille equation given by 4.11
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Example 4.4
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