Dimensionless Numbers in Hydraulics and Fluid Mechanics - The important dimensionless numbers are Reynold's number, Froude's number, Weber's number, Euler's number and Mach's number:
(a) Reynold's number: It is the ratio of the inertia force to the viscous force.
(b) Froude's number: It is the ratio of the inertia force to the gravity force.
(c) Weber's number: It is the ratio of the inertia force to the surface tension force.
(d) Euler's number: It is the ratio of the inertia force to the pressure force.
(e) Mach's number or Cauchy's number: It is the ratio of the inertia force to the elastic force.