The Pecular Behavior of Fire

[Anomalocaris]

Ever wonder why the plume coming out of the back end of a rocket gets so big the higher the rocket goes?

Less air pressure up there, so the exhaust fans out more.

Which causes a major design problem for bell shaped rocket engine exhaust nozzles. The design is governed by the expected rate of expansion of exhaust gas. But exhaust gas expands faster in vacuum of space or thin high atmosphere than in dense lower atmosphere. So an engine bell designed to maximize thrust at sea level loses thrust at altitude, and vice versa.

Hence aerospike.

[Rhondazvous]

Does convection have anything to do with the triangular shape of fire? Oddly enough, I found the word while looking for info about earthquakes.

[Thumpalumpacus]

Yes. Heat rises. As it rises away from the heat source, the heated gases begin to cool. The gases at the circumference of the updraft cool first, because they're exposed to cooler air more than the center of the column. Losing heat, there's more fire tetrahedron, and the flames are foreshortened, leaving the fire looking like a cone.

[Rhondazvous]

Yes. Heat rises. As it rises away from the heat source, the heated gases begin to cool. The gases at the circumference of the updraft cool first, because they're exposed to cooler air more than the center of the column. Losing heat, there's more fire tetrahedron, and the flames are foreshortened, leaving the fire looking like a cone.

Kewl! I guess that accounts for why fire dances.