Christmas Question Is it still christmas day?
I just lit the christmas pudding. For those unfamiliar with this tradition, one pours alcohol of sufficient concentration over the pudding and makes a bit of fuss around bringing it in on fire and usually in a darkened room.
Anyway, as the flame died down it became confined to circular ring of alcohol, in this case white rum around the base. We ended up with a single small flame rotating at speed around the base. It was doing maybe 1 to 2 Hz, and 50 or 60 cycles so this went on for minutes.
How can christmas spirit (pun intended, sorry) have this effect?
For the particularly time rich at this time of year, god bless you all, what equation would describe the frequency of oscilation?
 A: I think that what is driving this effect is heat transfer from the flame to the fuel and the flammable vapour above the liquid fuel.
Due to a local affect (e.g. geometry of the pudding - affecting ventilation or thickness of the liquid fuel - affecting temperature of the liquid fuel and hence vapourisation rate) there will be a flame in one area of the ring of fuel. In this local area, conditions are suitable for flame (sufficient oxygen, sufficient heat and sufficient vapour concentration). In other areas we can imagine that there is not sufficient vapour concentration and/or heat.
Our local flame causes an increase in heat adjacent to it (primarily radiation from the flame and convection from the flame and plume) and hence creates conditions suitable for flame adjacent to it (i.e. increases vapourisation and hence vapour pressure adjacent to it to flammable conditions). This causes a flame to be viable adjacent to the initial flame. The initial flame consumes available oxygen and falls below flammable limits (it was already on the cusp of flammability limits) hence is extinguished.
This process repeats around the ring of liquid fuel.
