text: The Weber number may be written as:
  where
  *  is the drag coefficient of the body cross-section.
  *  is the density of the fluid (kg/m).
  *  is its velocity (m/s).
  *  is its characteristic length, typically the droplet diameter (m).
  *  is the surface tension (N/m).
  The modified Weber number,
  equals the ratio of the kinetic energy on impact to the surface energy,
  where
  and