1.   It is directly related to the kinetic energy per unit volume associated with the velocity fluctuations,

2.   The same intensity field can in principle be produced by many different patterns of velocity fluctuation.

3.   Relationships between velocity fluctuations at different points are indicated by joint probability distribution functions.

4.   Information about velocity fluctuations at different points is given by correlation measurements.

5.   This term represents the action of the velocity fluctuations on the mean flow arising from the non-linearity of the Navier-Stokes equation.

6.   Writing the last two terms of as shows that the velocity fluctuations produce a stress on the mean flow.