Okay kiddo, you know how when you light a candle, you see a tall flame that flickers and moves around? Well sometimes, if you have a lot of candles burning together, you might notice that the flames start to group together and get bigger. This is called flame clustering!
What happens is that the hot air rising from each candle flame creates its own mini "wind" that pushes the flames around. When there are a lot of candles burning close together, these mini "winds" can start to interact with each other and create bigger movements in the air. This can cause the flames to cluster together and form bigger flames.
It's kinda like when you and your friends are all playing outside and running around. You might all start off in different places, but as you run around, you start to bump into each other and move around as a group. In the same way, the candle flames start off as individuals, but end up clustering together and becoming a big group.
Scientists study flame clustering because it can happen in other types of fires too, like in forests or in gas explosions. By understanding how it works, they can try to predict and prevent dangerous fires from happening.