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

当几根蜡烛捆绑在一起时，组合的蜡烛火焰的大小就会振荡。为了了解这一机理，我们进行了观测实验、蜡烛火焰周围的温度成像和图像分析，得到了蜡烛火焰上方的气流速度分布。我们的结果说明，当冷湍流从上部区域向下发展并接触到蜡烛火焰时，火焰振荡就开始了。研究还表明，振动状态下蜡烛火焰上方的气流速度远快于非振荡状态下的气流速度。从类比到气象学，我们推测观测到的冷湍流是由燃烧过程中产生的未燃烧的石蜡蒸汽云形成的。当蜡烛上方的云团向下膨胀时，它为燃烧提供了石蜡，发生了爆炸性燃烧。爆炸性燃烧导致火焰的膨胀和随后的收缩。

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.