ALE,Overlapping grid etc. Can somebody give some comment for these method?

ALE stands for arbitray Lagrangian-Eulerian description, which uses the advantages of each method without their disadvantages. It is a description for computational domain. In this approach, free surface is determined by the lagrangian method, while the nodes in the interior of the doamin are displaced in an arbitrary prescribed way to avoid mesh crossing. Therefore it is very useful for interface, free-surface and moving boundary problems.