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Title: Bouncing of a jet off a Newtonian liquid surface

Description: A Newtonian liquid jet can bounce off the surface of a moving bath (see the references below). In the first movie clip, the jet bounces spontaneously as the flow rate decreases rapidly (playback is slowed 8.3 times). The jet and the bath do not mix while bouncing; a thin layer of air separates the jet and the bath. The subsequent sequences show that the jet can bounce twice, that the jet bounces more vertically with smaller bath velocity, and that the bouncing jet can be unsteady but stable. In the last movie clip, the bath is stationary and the bouncing stream is moving. This experiment can easily be done at home by pouring mineral oil into a pan of the same oil.

For the sequence of images showing how a stream is made to bounce twice, the conditions are as follows: the liquid viscosity mu = 106 mPa s, the jet flow rate Q = 0.25 cm^3/s, the jet fall height H = 5.0 cm, and the bath velocity V_{bath} = 18.8 cm/s. The conditions for the movie of the vertically rebounding, unsteady bouncing jet were mu = 361 mPa s, Q = 0.24 cm3/s, H = 4.2 cm, V_{bath} = 0.74 cm/s, the jet rebounds on average 1.1 cm, and the movie plays at 16.7 times slower than real time. For the slow motion movie of the jet poured by hand, the viscosity was mu = 361 mPa s. For the conditions of all other visuals, see the associated Physics of Fluids article below.

A transcript of the narration is available here. Narration by Matthew Thrasher. The music is adapted from Accralate by Kevin MacLeod ( and the music is licensed under Creative Commons "Attribution 2.0." All references are available for download at

Credits: Matthew Thrasher, Sunghwan Jung, Yee Kwong Pang, and Harry L. Swinney

References: [1] M. Thrasher, S. Jung, Y. K. Pang, C.-P. Chuu, and H. L. Swinney (2007) "Bouncing jet: A Newtonian liquid rebounding off a free surface," Physical Review E, 76, 056319.

[2] M. Thrasher, S. Jung, Y. K. Pang, and H. L. Swinney (2007) "Bouncing of a Jet off a Newtonian Liquid Surface," Physics of Fluids, 19, 091110.

[3] M. Thrasher (2005) "A Liquid Stream Bouncing off a Moving Liquid Bath," MA thesis, The University of Texas at Austin.

[4] M. Thrasher (2007) "Geometry and dynamics of fluid-fluid interfaces," PhD dissertation, The University of Texas at Austin.

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Contributed By: Matthew Thrasher

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