PREVIOUS.rea
3                      spatial dimension (if negative dump binary re2 and .rea file)
1                       number of fields
#
# ======================= BOX 1 =======================
Box1      
-50 -10 -2                 nelx,nely,nelz (if <0, length to be equally divided)
0 12.0 1.00                 x_0  x_Nelx ratio
0 6.0 1.00                 y_0  y_Nely ratio  1.18
0 1.0 1.00
P  ,P  ,W  ,W  ,P  ,P           bc's  ! west,east,south,north,bottom,top (fixed 3CHAR format)