Oscillations and collective behavior in convective flows

Oscillations 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. Experimentally, it is shown 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 are observed. A toy-model based on elementary fluid dynamics describes the observed oscillations and leads to frequencies with the proper trend and values in the right order of magnitude.