# Dynamic viscosity

The SI unit of dynamic viscosity (Greek symbol: $\mu$) is pascal-second ($Pa\cdot s$), which is identical to $\frac{kg}{m\cdot s}$.

The dynamic viscosity is related to the kinematic viscosity by

$\mu=\rho\cdot\nu$

where $\rho$ is the density and $\nu$ is the kinematic viscosity.

For the use in CFD, dynamic viscosity can be defined by different ways:

• as a constant
• as a function of temperature (e.g. piecewise-linear, piecewise-polynomial, polynomial, by Sutherland's law or by the Power law)
• by using Kinetic Theory
• composition-dependent
• by non-Newtonian models