There are many interesting fluid oscillators:
this is a tilted water wheel driven by gentle water flow
from above. Water begins to fill a cup near the top of
the tilted wheel, which becomes heavy, and falls in a
pendulum oscillation. Meanwhile other cups are filled
as they pass under the water source. This is a close analog
of a heated fluid loop, obeying Lorenz's famous chaos equations.
The result is a chaotic pendulum-like oscillation of the tilted
wheel. [Water drains out steadily through holes in the bottom
of each cup.] The experiment was first devised by Willem Malkus
and Lou Howard at MIT.
