Expansion and Contraction of Jets of Newtonian Liquids in Air: Effect of Tube Length

An experimental study of the effect of tube length‐to‐diameter ratio, L/d0, on the expansion and contraction of jets of Newtonian liquids into air is described. For Reynolds numbers based on tube diameter, Red, above 16 the jets contracted. Jet diameter correlated with the degree of development of the velocity profile in the tube, a function of L/d0, and was unaffected by viscous dissipation. At Red = 16 the jet diameter was equal to the tube diameter and was independent of L/d0. When Red < 16 the jets expanded. Jet diameter was affected by viscous dissipation. Most of the data in this range could be correlated as a function of the Reynolds number based upon tube length, ReL, and of the ratio of the Brinkman number to the product of the Prandtl number and ReL. How the stresses acting in the jet and in the tube are influenced by profile development and by viscous dissipation and affect jet diameter is discussed.