# Shear Thinning

## Definition - What does Shear Thinning mean?

Shear Thinning is a behavior of drilling fluids in which the viscosity of a certain drilling fluid decreases under shear strain. This means that the viscosity of fluid decreases whenever the rate of shear increases. This shear thinning behavior of fluid is called non-Newtonian fluid behavior and at times it is also referred to as pseudoplastic fluid behavior.

## Petropedia explains Shear Thinning

The viscosity of a non-Newtonian fluid primarily depends on the rate of shear of the fluid and it decreases whenever the rate of shear increases. Shear thinning behavior is generally not seen in pure liquids with low molecular mass, or ideal solutions of small molecules like sucrose or sodium chloride, but is often seen in polymer solutions, molten polymers, complex fluids and suspensions like ketchup, whipped cream, blood,^{ }paint, and nail polish.

Rate of Shear is of two types, i.e., constant shear rate and stepped shear rate. As it highly depends on viscosity thus its behavior fluctuates such that:

- If the viscosity increases, the rate of shear decreases;
- If the viscosity decreases, the rate of shear increases;
- If the viscosity remains constant, the rate of shear also remains constant.

To portray the behavior of materials it forms four flow curves namely Newtonian, shear thinning, shear thickening and Bingham plastic. Moreover, when the shear rate is multiplied by the viscosity it gives the value of the shear stress.