Fluid pipe
Fluid pipes are a phenomenon driven by surface tension. When a pure water jet impinges on a reservoir, capillary waves are excited and propagate up the jet at the same speed that the jet falls.
Fluid pipe phenomenon may be observed with a kitchen faucet. When the diameter of the stream is 2–3 mm, placing an obstacle in the stream will give the desired effect. Contamination of the reservoir with a surfactant will eliminate the effect of capillary waves up a fluid pipe and results in the jet entering the reservoir as a rigid pipe.
