You would think the more wind the faster the fire gets extinguished, I have a feeling the size of the fire matters but i just wonder why and where the line is drawn between a candle and a wildfire in extinguishing it when blowing wind on it goes from a very effective to a super ineffective technique.
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ELI5. Think of it as two competing opposing “forces”. Moving more air through the flames, means the flame has to work harder to heat the additional air in order for the flames to stay alive. So this wind, removes heat from the flames. The opposing thing is that the additional air also brings along more oxygen which allows the flames to burn faster and stronger (as long as there is sufficient fuel).
So a small flame benefits a bit less from the wind bringing oxygen and the air takes away enough heat that the flame dies.
A larger flame with a lot of fuel, say a forest fire, benefits a lot more from additional oxygen and the flame is so large that it can heat the additional air from the wind. So the flames burn even stronger and the wind cannot put it out.
Both factors are at work, it just depends on the situation which factor outweighs the other.
The wind only aggravates the fire to spread, infact it’s not “blowing out” on the candle. The fire looks for other combustible things to “set it on fire”. Since the candle has only one wick, the fire can’t find anything else and dies out.
If the wind is less than what the fire can heat then the wind will make the fire hotter because it introduces more oxygen (fire is rapid oxidation). If the wind is more than what the fire can heat, the burning fuel will cool off until it drops below its combustion point and it goes out.
What this means is a little fire like a candle can only handle a little tiny wind before it will cool faster than it can heat and goes out. A big fire can handle a big wind and will take a massive wind to cool it faster than it heats and go out. Once the fire is big enough, nothing is going to generate a wind fast enough to exceed the speed at which it can heat the fresh air.
Other comments get this right, but I wanted to add that fire needs three things, heat, oxygen, fuel. Remove just one of those things enough and the fire goes out. In this case, as other users have pointed out, wind removes the heat for small fires, but is unable to do so quickly enough in large fires.
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