text: The Ohnesorge number (Oh) is a dimensionless number that relates the viscous forces to inertial and surface tension forces.  The number was defined by Wolfgang von Ohnesorge in his 1936 doctoral thesis.
  It is defined as:
  Where
  * μ is the dynamic viscosity of the liquid
  * ρ is the density of the liquid
  * σ is the surface tension
  * L is the characteristic length scale (typically drop diameter)
  * Re is the Reynolds number
  * We is the Weber number