Departure-site spacing for liquid droplets and jets falling between horizontal circular tubes

When a liquid film falls from one tube to another below it, the flow can take the form of discrete droplets, individual jets or a continuous sheet. Experiments exploring the effects of thermophysical properties and geometrical parameters on the droplet and jet flow patterns are described. Measurements of droplet and jet departure-site spacing are reported for several fluids over a wide range of liquid flow rates, tube sizes and tube spacing. For the conditions of this study, departure-site spacing increased with decreasing Re for high-Ga fluids and was nearly independent of Re for low-Ga fluids. Departure-site spacing increased slightly with tube diameter for small tubes and was nearly independent of tube size for large tubes. Departure-site spacing was nearly independent of tube spacing for the entire range of experiments; however, a relation between jet shape, jet spacing and tube spacing was observed under some conditions. A qualitative study of liquid-jet shapes shows that this flow feature depends strongly on tube spacing, and comparisons to existing models suggest that further work in this area is needed.