How to Calculate and Solve for Viscosity of Newtonian Fluids | Rheology

The image above represents viscosity of newtonian fluids.

To compute for viscosity of newtonian fluids, two essential parameters are needed and these parameters are Shear Stress (ζ) and Shear Rate (γ).

The formula for calculating viscosity of newtonian fluids:

η = ζ / γ

Where:

η = Viscosity of Newtonian Fluids
ζ = Shear Stress
γ = Shear Rate

Let’s solve an example;
Find the viscosity of newtonian fluids when the shear stress is 15 and the shear rate is 5.

This implies that;

ζ = Shear Stress = 15
γ = Shear Rate = 5

η = ζ / γ
η = 15 / 5
η = 3

Therefore, the viscosity of newtonian fluids is 3.

Calculating for Shear Stress when the Newtonian Fluids and the Shear Rate is Given.

ζ = η x γ

Where;

ζ = Shear Stress
η = Viscosity of Newtonian Fluids
γ = Shear Rate

Let’s solve an example;
Find the shear stress when the newtonian fluids is 20 and the shear rate is 4.

This implies that;

η = Viscosity of Newtonian Fluids = 20
γ = Shear Rate = 4

ζ = η x γ
ζ = 20 x 4
ζ = 80

Therefore, the shear stress is 80.