in classical rigid body newtonian mechanics, and in solid mechanics, people
use: lagrangian framework for governing equations;
in fluid mechanics, popele use: eulerian framework for governing equations;
however, it turns out both are subsets & can be united;
the superset is: arbitrary lagrangian eulerian framewrok (ALE);
so, up to here, ALE has nothing to do with moving boundaries & free-surface
flows;
ALE is about how to formulate your equations;
level set is about how to capture moving interfa