Why does fire on a stick get put out faster when you move your hands (to put out the flame) vertically? I lit an incense stick and just tried to put out the flame. I first moved my hand horizontally and the flame just flickered. The I moved my hands vertically. The flame was extinguished. But it seemed to me that the flame somehow was put out faster when I moved my hands vertically. I could take much less effort and put out the flame if I did it vertically rather than doing it horizontally, it seemed.
I repeated this multiple times and the results where almost always identical.
Why does this happen ? Is it possible that this is just an illusion ?
Thanks !
P.S: I have no idea what to tag this with. Please edit it.
 A: Due to the heat of the flame, the air around it (and the products of the burning) are heated up and their density lowers.  This creates an upward draft that feeds the flame.
When you move your hand vertically with the flame I suspect you're smothering it more in the direction of the air movement; where interference is more likely to stop the reaction.
When you go across you make some drafts that interrupt the air movement; but the main flow from top to bottom isn't interfered with as much.
A: I think this is to do with the structure of a buoyant plume. Your burning incense stick is forming a vertical buoyant plume above the combustion zone. This is due to the heating of surrounding air due to exothermic combustion process. This heated air has a lower density than surrounding air and therefore experiences a buoyancy force upwards. This hot buoyant plume is transferring heat via radiation and convection to the combustion zone, leading to continued release of pyrolysis gases and hence combustion.
When you swipe your hand left-to-right you are moving air lateral to the buoyant plume with minimal disturbance of the plume structure (left sketch). When you swipe your hand from top-to-bottom you are disturbing the entire structure of the plume and for an increase duration of your swipe (right sketch). A higher percentage of your swipe is directly affecting the plume for your top-to-bottom swipe.

This means that you're: (1) disturbing more pyrolysis gases, (2) entraining more cooler air, (3) disturbing the hot plume more - which has the effect of: (1) reducing combustible gases to combustion zone, (2) cooling this plume, reducing heat transfer to the combustion zone, (3) again reducing the heat transfer to the combustion zone.
