code: def re_general(Vel, Area, PerimWetted, Nu):
      
      #Checking input validity - inputs not checked here are checked by
      #functions this function calls.
      ut.check_range([Vel, ">=0", "Velocity"], [Nu, ">0", "Nu"])
      return 4 * radius_hydraulic_general(Area, PerimWetted).magnitude * Vel / Nu
docs: Return the Reynolds Number for a general cross section.