text: When used in the context of the Boussinesq approximation the densimetric Froude number is defined as
  where  is the reduced gravity:
  The densimetric Froude number is usually preferred by modellers who wish to nondimensionalize a speed preference to the Richardson number which is more commonly encountered when considering stratified shear layers. For example, the leading edge of a gravity current moves with a front Froude number of about unity.