How do you make a fluid emit smoke and fire? I am trying to make a liquid catch fire. However, I do not know how to make the fluid emit in the gas domain. A similar question was posted here:
How to light liquid on fire?
However, in the answer, it is mentioned that you need to make the liquid a mesh emitter. I can make the liquid a mesh, but I can't figure out how to make it emit in the gas domain. Any help would be great!
Since a mesh can only have a single fluid sim applied to it, it is not possible to have both a fluid and a gas simulation at the same time. Instead, you need to add an additional mesh that can follow the fluid simulation to host the gas (smoke and fire) simulation.
Start by setting up and simulating your fluid. Once this is complete, create a new mesh (eg, a sub-divided plane) and use the Shrinkwrap modifier to map this over the fluid. Add the smoke and/or fire simulation to the 'shrunkwrapped' mesh in place of the fluid mesh.
This can produce results similar to the following :

For simplicity I only rendered smoke but the same principle applies to smoke and fire. Also, you could add a particle system to emit particles of smoke/fire from the surface or change the smoke emission with a texture for added variability.