on certain occasions i found this expression works
setAttr fluidShape1.is2d 0
it basically converts the "height field" to a legitimate third dimension. Still, this is not particularly helpful for highly detailed deep simulations such as explosions. I think at ilm they did the following:
Imagine a cross section through the middle of a mushroom cloud, says Hammack. Take several of those, rotate them around, interpolate the velocities between, and you end up with an organic, rounded-shaped cylinder from a few unique 2D sims. its a great technique to create fine detail for a complicated, large-scale effect when you're working with something that's semi-symmetrical.
http://www.cgw.com/ME2/dirmod.asp?sid=&...1F4C4C0B45EFD9D