- 2.81a and earlier (pre-mantaflow)
- and 2.82 Alpha (2020-01-05) 5c66739b782e (mantaflow)
Short description of the error
All objects involved in a fluid (gas or liquid) simulation, including domains, effectors, etc, have a modifier in the modifier stack.
However, in all cases except one, the "Apply" button in this modifier is (as far as I can tell) just a synonym for "remove the modifier and the physics settings (destructively!)". It only actually "applies" something when we're dealing with mesh-baked liquid domains.
Such "Apply" button may be misleading and dangerous if a user were to, for instance, try to "freeze" a frame of a smoke simulation, which will just result in them losing all cache.