Herschel-Bulkley Equation

$\tau \to$ shear stress (Pa) ${\tau }_0\to$ yield stress (Pa) $k\to$ consistency index (Pa s${}^n$) $\dot{\gamma }\to$ shear rate (s${}^{-1}$) $n\to$ power law index (dimensionless)

n < 1 $\to$ fluid is shear-thinning n > 1 $\to$ the fluid is shear-thickening. n = 1 & ${\tau }_0=0$ $\to$ Newtonian fluid.

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References

1. https://en.wikipedia.org/wiki/Herschel%E2%80%93Bulkley_fluid