# Dynamic or Kinematic Viscosity

The dynamic description is given by the navier stokes equation, which is analogus to a newtonian momentum balance on a fluid element. The material derivative 

$$
\overbrace{
\left(
\frac{\partial}{\partial t}+\bf{v}\cdot\nabla
\right)
}^{\frac{D}{Dt}}
\left(\rho \mathbf{v}\right)
============================

-\nabla p+\mu\nabla^2\mathbf{v} +\rho \mathbf{g}
$$