I added two particle systems to the wick of the candle. The first emits 15000 particles over 500 frames with just normal velocity, a little upward acceleration and a small amount of random initial velocity. The second system emits only 20 particles over 500 frames: these are invisible but set to act as vortices (in the fields and deflection panel you can now select particle systems as well as objects to emit fields) with random rotation. These have more random velocity variation than the visible particles so don’t stay in sync with them. By tuning the vortex strength and falloff, you can get these turbulent effects.
Also, I added an ipo to the first (visible) system to increase the strength of the brownian motion as time goes on (actually it increases quite sharply after about 75% of the lifetime), to make the particles disperse out as they get towards the top of the path.
It’s a bit too turbulent to be realistic at the moment, and at the same time there’s a large spiral that’s kind of taking over and a bit too obvious, but I think with some tweaking this could be good