Dynamic Similarity of Flows with Surface Tension as the Dominant Force

Surface tension forces are important in certain classes of practical problems such as ,

1. flows in which capillary waves appear
2. flows of small jets and thin sheets of liquid injected by a nozzle in air
3. flow of a thin sheet of liquid over a solid surface.

Here the significant parameter for dynamic similarity is the magnitude ratio of the surface tension force to the inertia force.

 This can be written as   

The term   is usually known as Weber number, Wb (after the German naval architect Moritz Weber who first suggested the use of this term as a relevant parameter. )

Thus for dynamically similar flows (Wb)_m =(Wb)_p

i.e.,