  Oscillation and collective behavior in convection-driven fluid columns are
investigated and discussed in analogy with similar phenomenon observed for the
flickering flames of candle bundles. It is shown experimentally that an
ascending circular Helium gas column performs an oscillation which is similar
in several aspects to the oscillation of diffusion flames. Increasing the
nozzle diameter leads to a decrease in the oscillation frequency, while
increasing the flow rate results in an increase in this frequency. For helium
columns oscillating at nearby frequency and placed close to each other
anti-phase synchronization and beating phenomena is observed. A simple
toy-model based on elementary hydrodynamics describes the observed oscillations
and leads to oscillation frequencies in the right order of magnitude.
