Or in dimensionless forms F P D D (9.7) P G The ratio of inertial force to viscosity force is 7 DN DD/N FV UNDi -Re(9.8Or in dimensionless forms: = = (9.7) = The ratio of inertial force to viscosity force is = = = (9.8) P V I F F ( ) m V I F F ( ) P D I F F ( ) P G I F F ( ) m D I F F ( ) m G I F F ( ) V I F F 2 4 2 I I ND D N    DI N 2 i NRe