I’m watching CSI and one of the investigators said “fire is drawn to fire” while they were looking at the dead guys burnt out house. Is this a real fact or a scriptwriter fact? Will two fires burn towards each other? If it is a real fact, why would this be so?
Not exactly. Light the top two corners of a piece of paper on fire. The two fires will move towards each other, but only because that is the only direction they can go to get more fuel. Fires generally follow the path of most flammable fuel and available oxygen. There’s no reason for two separate fires to move towards one another, necessarily.
I should have added “all things being equal” some where in there.
Well yes, there is a reason to adjacent fires would tend to coalesce (ie expand more quickly towards each other than in other directions), radiant heating. Flammable materials located between two fires pick up heat from both sources, while flammables to one side or the other get most of their heat from only one source. The faster the material heats, the faster it ignites.
The effect of adjacent heat sources on the intensity of a fire is easily observable in a bed of hot wood coals. Blow gently on a single coal, and the resultant increase in combustion temperature travels in a wave of visibly hot coals across much of the bed. Or conversely, if you dim a single coal by hitting it wth a drop of water, and all the coals around it will dim as well, as they receive less heat from the extinguished bit of wood. Fire is a highly nonlinear (AKA cooperative) process.
I find this hard to swallow. Keeping in mind that radiant heat obeys the inverse square law, the temperature around each individual fire is going to be vastly more affected by that fire than the other, more distant one. As such, I’d expect the temperature around each fire to be roughly equal in all directions. I suppose if the two fires were very close together, this effect might cause them to tend to move together, but the strength of the effect would drop off very rapidly with increasing distance.
Well if you want to talk about point sources of flame, at an infinite distance from each other…
The inverse square relation gets distorted as you near the actual fire, and begin to confront something that looks, mathematically, more like a plane surface emitting radiation. What does that fall off at, 1/d or so? (no physics book handy). That’d leave plenty of room for synergy between two blazes.
Well, you go set your carpet on fire in two places, say, 3 meters apart. I’ll await the results. 
Plus, the heat from flame A causes the air above it to rise, sucking in nearby air. If flame B was close enough, it might get pulled in a bit.
What Smeghead said but more: Wouldn’t the rising columns of air of both fires cause a lower pressure area in between the two, thus causing them to move towards each other?
Semi-related party trick: If you take a lit candle and blow it out, but then touch a flame to the smoke trail from the wick, the flame will ‘jump’ down the smoke trail and re-ignite the wick. I’ve done this as far as 8 inches from the wick on a big candle, but try it 3 inches away to start. Make sure the candle has been lit for a minute or so to produce enough smoke. Sorta neat looking.
-Tcat
I presume this is the same idea as the one behind the WWII technique of fire bombing, as in Dresden? (Only on a much smaller scale, of course?)