Bouncing jet


What happens when you pour a liquid into a pool of the same liquid? As far as most people think and so did our group until we understood this fascinating phenomenon, both liquids will merge into one body immediately upon contact. The bouncing jet is a phenomenon that happens when a Newtonian liquid is streamed or poured in a pool of the same exact liquid under certain conditions. These conditions occur when the liquid is Newtonian, the pool is of the exact same liquid, and the pool of water is moving [1]. When streamed into the pool, liquid will bounce off the surface of the pool while maintaining separation. This is instead of merging with the pool, if and only if the conditions are satisfied.

Figure 1: a photograph taken by Matthew Thrasher and colleagues at the University of Texas at Austin who built a rotating oil bath into which a stream of (same) oil was dropped. [3]

Water droplet entering stationary water body.

Conditions and Thin Layer of Air

This phenomenon can only occur under certain conditions. Two overshadowing conditions are the fluid must be Newtonian, due to its reliance on Newton’s third law, and the flow must laminar (4). Furthermore, in order to create this the fluid must be identical and pure as any kind of foreign substances on the top of the basin will affect the way the thin layer of air is created.