Page 143 - The Combined Finite-Discrete Element Method

126 CONTACT DETECTION

Central raw i y

Layer i z

Figure 3.63 The non-empty row of cells (i y ,i z ) is divided into individual cells.

The central row (i y ,i z ) is divided into individual cells (Figure 3.63). For each of
the cells, a singly connected list containing all discrete elements mapped onto that cell
is assembled.
By looping over all discrete elements in row (i y ,i z ), a nonempty cell (i x ,i y ,i z ) is
identified (Figure 3.64). Contact interaction with discrete elements from neighbouring
cells according to the contact mask is performed. Each non-empty cell in the row (i y ,i z )
in turn becomes the central cell. In a similar way, each non-empty row from layer i z in
turn becomes the central row. In the same way, each non-empty layer in turn becomes the
central layer. Only non-empty layers, non-empty rows and non-empty cells are visited.
The pseudo code for NBS contact detection algorithm in 3D is as follows:

1. Loop over discrete elements (k=0;k≤N;)
{ calculate integerised z coordinates of the centre and
place the discrete element onto the corresponding z-list

Central cell
Central raw i y

Layer i z

Figure 3.64 A non-empty cell (i x ,i y ,i z ) is detected.