We are currently studying dissipationless, dispersive hydrodynamic
phenomena in a viscous fluid conduit system. The controlled intrusion
of a lighter, less viscous fluid (e.g., corn syrup + water) into a
cylinder filled with a very viscous fluid (e.g., corn syrup) can lead
to the formation of an azimuthally symmetric fluid-filled pipe or
conduit. In the video below, we suddenly increase the injection rate
to a larger value, causing the conduit to dilate. Buoyancy causes the
wider portion of the conduit to move faster than the narrower portion.
Viscous forces in the external fluid balance buoyancy by generating
interfacial waves, leading to an expanding oscillatory wavetrain, or
dispersive shock wave (DSW for short).