# What happens when two flames meet from opposite sides?

What happens when two flames (whether from dragons or blowtorches) meet head on? Many films make it appears as a front where the two flames repel each other, but my intuition is that, in fact, the two flames would continue as two waves on the surface of a lake.

In short, does anyone have sufficient scientific skills (or experience) to describe what happens when two flames of the same intensity impact directly opposite one another?

Can a dragon block a fire attack with its own fire?

• The same thing as what happens when two streams of water collide. Jan 14, 2019 at 13:09
• A flame is not a wave, it is a flow of hot gas. (That is to say, a flame is a material flow, like a river.) When two such flows intersect they may merge, or they may produce a highly turbulent flow, depending on flow speed and volume. One thing they won't do is pass through one another unmodified. P.S. What is a "chalumal"? Neither Google nor the Oxford English Dictionary know this word. Jan 14, 2019 at 13:33
• @Renan For safety concerns, do add fire-protective clothing, safety glasses, and so on. Otherwise, get a third friend to videotape what happens, post the thing on youtube, call 911 and watch the thing go viral for the next contenders for the Darwin award. Jan 14, 2019 at 14:15
• What is a "chalumal"? Are you mistranslating from French? possibly "blowtorch" < commons.wikimedia.org/wiki/File:Blow_Torch_(3257353199).jpg >? Jan 14, 2019 at 14:47
• Matrix, I edited your question for grammar and structure but I also made a very significant change. You spoke of two flames crossing but your picture and other statements made it clear you really meant them meeting head on. Crossing in the way you described it would imply the flames met at a 90° angle. If my edit was wrong, please change it back. Jan 14, 2019 at 15:43

Flames are not waves, which can cross each other without perturbation.

Flames are basically flows of particles (the combustible) which are undergoing an energetic, exothermic reactions with the comburent (usually air Oxygen).

When the particle flows cross each other they will influence their respective motion, with a "simple" vectorial summation of their velocities, executed according to the principles of conservation of momentum and energy.

• @Matrix, the only wrong part in the image is that the flame to not simply disappear. They would spread around more or less like a disk
– L.Dutch
Jan 14, 2019 at 13:35
• I expect that they will mix rather more than that image suggests too although I have no evidence for that. Jan 14, 2019 at 13:36
• @Matrix Too hard to say, someone would need to do the experiment (or look and see if anyone already did it). Jan 14, 2019 at 13:49
• The MythBusters tried something like this: mythresults.com/fire-vs-ice Jan 14, 2019 at 15:26
• Then give some examples using fuels that you consider to be reasonable choices for the question at hand? Assume air as the medium, since the OP gives us a picture of flying creatures. And maybe just use stationary as an oversimplified starting point if motion is going too far. But put some kind of example in the answer. Jan 15, 2019 at 4:10

Fire is not "a thing" itself, but rather the rapid, exothermic oxidation of some material, normally gas (most or all liquids, that seem to burn are actually evaporating from the heat and only the gas burns).

So if two streams of fire meet, they will in most cases behave, like two colliding streams of gas. Unfortunately I do not seem to be able to find a simulation of this. But here, you can see two streams of water collide. Gas will mostly look similar, but there will be more mixing of the two streams and more turbulences, resulting in a bigger cloud where they meet.

[edit: added from comment]
If angle, strength and surface are no exact match, but roughly right, it will still result in a lot of turbulences and most parts of the streams will disperse. But it quickly gets unpredictable and there may be small clouds of flame that reach one of the participants or cause collateral damage. If you watch the video, you will see, that the streams are not exactly the same. As a result, in the first 3 seconds the right source is hit by a blob of the left stream. After that, the streams reach an equilibrium. But this is partly because the sources are perfectly still.
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This of course only works, if both streams are roughly the same size and power and directly colliding. If one is bigger or has more pressure or they hit each other at an angle, it starts to get complicated.

But in basic principle, yes, you can block a stream of fire with another stream of fire.

• yes but we need have exactly the good angle, strength and surface of stream, so it's not realy realist no? In real life, it's impossible to have exactly all variables in good proportion at same time and maintain them over time... Jan 14, 2019 at 15:29
• If angle, strength and surface are no exact match, but roughly right, it will still result in a lot of turbulences and most parts of the streams will disperse. But it quickly gets unpredictable and there may be small clouds of flame that reach one of the participants or cause collateral damage. If you watch the video, you will see, that the streams are also not exactly the same. As a result, in the first 3 seconds the right source is hit by a blob of the left stream. After that, the streams reach an equilibrium. But this is partly because the sources are perfectly still.
– Till
Jan 14, 2019 at 15:57
• Re, "Fire...only the gas burns." After a camp fire has burned down to a pile of glowing red charcoal, is that not still a "fire?" (I know! I know! It's not exactly dragon fire.) Jan 15, 2019 at 2:56
• @Till - sorry to be pedantic, but gas, as well as plasma (and obviously liquid) are all fluids! See: en.wikipedia.org/wiki/Fluid Otherwise, all good... :) Jan 15, 2019 at 6:49
• @JeremyDavis You're right. This was a translation error of me, since I'm not a native English speaker. I meant liquids.
– Till
Jan 15, 2019 at 7:29

## It boils down to blocking a stream of gas with another stream of gas.

Fire happens when some sort of fuel undergoes combustion. With dragons this is usually presumed to be a flammable gas they are exhaling. The danger of such a fire comes from the combustion heating the gases that result from the combustion and other nearby gases to such a high temperature that they'll burn you or set you on fire if they touch you. So if you want to block a dragon's fire blast, you need to prevent that stream of very hot gases from touching you.

A simple experiment would be to have two people try to blow smoke into each other's faces at the same time. That should be a very rough approximation of what would happen. I suspect that the two streams actually would cancel out and become a cloud of smoke in the middle.

Well since fire has no physical substance they should carry on through each other like, "two waves on the surface of a lake." However fire consumes oxygen so passing through where fire had just burn oxygen, they should both die immediately if in a confined space, while if they are outside, imaginable when two fire breathing creatures meet, then the fire should just lose some or most of its size, with anther possibility being that they will combine into one flame (it would depend on the speed of the fire). However if the fire was being created and maintained by a liquid fuel the effect would be near identical to that of which when water meets water head on.

• Fire most definitely has a physical substance -- it's a flow of hot gas. Hot gas emits light just like any other hot body. Why would anybody believe that fire has no substance? Jan 14, 2019 at 13:25
• @AlexP The Rule of Cool has led to things like that, unfortunately. Jan 14, 2019 at 13:33
• @Renan possibly also a confusion on how the energy propogates? If you know that a ripple is nothing more than a virbration through a substance and heat is a vibration óf the substance you might confuse the two to be interchangeable. Which in part they even are as a ripple will leave some heat energy and heat energy will cause the surrounding material to start vibrating as it passes its energy. And if you then miss that the heat of the fire is an effect rather than the cause (which is the chemical reaction in exothermic fire) then this misconception is the result. Jan 14, 2019 at 15:47
• @Demigan Makes sense, but by Occam's razor I am still blaming cartoons and comics displaying battles of energy streams. Jan 14, 2019 at 15:54