What is the Difference Between Kinematic and Dynamic Viscosity?

The difference between kinematic and dynamic viscosity lies in their definitions, units, and the factors they depend on. Here are the key differences:

1. Definition: Dynamic viscosity (also known as absolute viscosity) is the measurement of a fluid's internal resistance to flow, while kinematic viscosity is the ratio of dynamic viscosity to density.
2. Units: Dynamic viscosity is measured in units of Ns/m² (Newton seconds per square meter), while kinematic viscosity is measured in units of m²/s (square meters per second).
3. Dependence on Density: Kinematic viscosity depends on the density of the fluid, whereas dynamic viscosity is independent of density.

In summary, dynamic viscosity is a measure of the force required to move one layer of a fluid over another, while kinematic viscosity is a measure of the velocity at which a fluid flows, taking into account its density. Dynamic viscosity is more related to the interaction between molecules and the effect of formulation changes on molecular interaction and viscosity, while kinematic viscosity is more relevant in oil industries due to the simplicity of its measurement.

Comparative Table: Kinematic vs Dynamic Viscosity

The main difference between kinematic and dynamic viscosity lies in their definition, units, and applications. Here is a table summarizing the differences between the two:

Dynamic viscosity is an intrinsic property of a fluid, defined as the resistance to the flow/movement of one layer of fluid over another. It is the ratio of shear stress to shear strain. Kinematic viscosity, on the other hand, is the ratio of dynamic viscosity to density and relates flow characteristics of a fluid to its density.