the first one… yeah… thats fumalicious…
if anyone can pull that off, you the man. Maybe a combo of 2d and 3d fluids, but thats alot of detail…
the second one :
two 2d fluids, one vertical, one horizontal. the horizontal one will burn along the ground and maybe emit into the vertical one (but this doesnt have to be that fancy, a moving emitter can do too). both are very high res. but from that angle, we can safely assume taht its a long camera shot so we dont need the perspective of a 3d fluid.
maybe the one on the ground would have alot of fuel emitted into it with a slow reaction time. then it will burn along its length naturally...
just some ideas, in fact just thinking them makes me want to try this at home 