In Fluid Mechanics we come across several non-dimensional numbers, each of them derived following the method outlined. It is important to realise is that these are not just numbers. They have a deeper physical significance. It turns out that each of these numbers is the ratio of a pair of forces. The magnitude of the number indicates the relative importance of the forces for a given flow.
(c) Aerospace, Mechanical & Mechatronic Engg. 2005
University of Sydney