Steady laminar round jets of a viscous liquid falling vertically in the atmosphere

The shape of a laminar, liquid jet emerging from a round vertical tube into the atmosphere and the total axial force exerted on the liquid filament at the tube exit were investigated experimentally over a wide range of flow conditions. An integral invariant of the exact solution was used to check consistency between the two kinds of data. A new equation to predict the jet shape agreed moderately well with the present experimental data as well as with various previous results. The key idea of the present work is that exact knowledge of the total axial force will be very useful to predict reasonably the jet shape at a given flow condition by means of a simplified approach or to check theoretical or empirical results on free falling jets.