Instead of advecting a marker function identifying the different fluids directly, as in the VOF method, the boundary between the fluids can be represented by connected marker points that are moved by the fluid. This approach is usually called front tracking, and in Chapter 4 we discussed the basic idea briefly and gave a short historical overview. In this chapter we describe front tracking in more detail.

The use of connected marker points to track the motion of a complex and deforming fluid interface can lead to several different methods, depending on the details of the implementation. Generally, however, front tracking involves the following considerations:

1. (i) The data structure used to describe the front. Although the use of marker particles simplifies many aspects of the advection of a fluid interface, other aspects become more complex. We use front to refer to the complete set of computational objects used to represent the interface. In addition to the marker points, the front often includes information about the connectivity of the points, as well as a description of the physics at the interface. The management of the front can be greatly simplified by the use of the appropriate data structure. There is a fundamental difference in the level of complexity between fronts in two dimensions and in three dimensions and, in general, any data structure can be made to work reasonably efficiently in two dimensions. […]