A free surface is a surface separating two different physics and whose position is not known. The determination of the position is therefore part of the problem that has to be solved. A typical example is the interface between the water and the air that appears when computing the performances of a yacht.
The modelisation of the free surfaces is an interesting and challenging problem.
At CMCS, three methods for the motion of the surfaces are mainly used:
- The level set method (LS)
- The volume of fluid method (VOF)
- The ALE method
ALE method is part of the front tracking methods and is used mainly for FSI problems due to its limitation to small displacement of the surface. Front capturing methods (LS and VOF) are used for problems more demanding in terms of flexibility.