eddy velocity
From Glossary of Meteorology
(Also called fluctuation velocity.) The difference between the mean velocity of fluid flow and the instantaneous velocity at a point.
For example, 
is instantaneous velocity, and U is mean velocity. Over the same interval that defines the mean velocity, the average value of the eddy velocity is necessarily zero.
where u is the eddy velocity,
is instantaneous velocity, and U is mean velocity. Over the same interval that defines the mean velocity, the average value of the eddy velocity is necessarily zero.
