Elucidating candle flame oscillation and synchronization on the analogy of meteorological pattern dynamics

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When several candles are bundled together, the size of the combined candle flame oscillates. To understand the mechanism, we carried out the observationnal experiments, the temperature imaging around the oscillating candle flame and the image analysis to obtain the velocity distribution of the air flow above the candle flame. Our results elucidate the flame oscillation begins when cold turbulence grows downward from the upper regions and touches the candle flame. We also show that the velocity of the air flow above the candle flame under the oscillation state is much faster than that under the non-oscillation state. From analogy to meterology, we speculate that the observed cold turbulence is formed by a cloud of uncombusted paraffin vapor generated during combustion. When the cloud above the candle expands downward, it supplies the paraffin for the combustion, and explosive combution occurs. The explosive combustion causes the expansion and subsequent contraction of the flame.