**1. n. [Drilling Fluids]**

A fluid described by the two-parameter rheological model of a pseudoplastic fluid, or a fluid whose viscosity decreases as shear rate increases. Water-base polymer muds, especially those made with XC polymer, fit the power-law mathematical equation better than the Bingham plastic or any other two-parameter model. Power-law fluids can be described mathematically as follows:

**See:**
Bingham plastic model,
centipoise,
direct-indicating viscometer,
Herschel-Bulkley fluid,
Newtonian fluid,
non-Newtonian fluid,
plastic fluid,
pseudoplastic,
rheological property,
rheology,
shear rate,
shear stress,
viscosity,
XC polymer

Power-law fluid.