Multi-Material Model

Currently, DES is only set-up to run one rheology at a time, so all layers in a model must have the same rheology time (e.g. elasto-visco-plastic or elasto-plastic). A multilayer example is available in the folder DynEarthSol/examples/ ; look at files rifting-2d.cfg and rifting-2d.poly. The .poly file holds information about the layer geometry and the configuration file tells DES where to look for that information.

In .cfg file

1. In [mesh] section, specify poly_filename: e.g.,

poly_filename = rifting-2d.poly

2. In [mat] section, specify num_materials: e.g.,

num_materials = 4

• Provide as many values as num_materials for all the material properties (e.g. rho0, lambda, mu, etc): e.g.,

rho0 = [ 2800, 2900, 3210, 3300 ]

• We recommend you draw a schematic such as the one in rifting-2d.poly to illustrate your layers with labeled nodal points (shown below):

In .poly file

In this file, you will define

• node coordinates
• segments connecting coordinates
• regions

1. Node coordinates As in the example .poly file, specify the number of total nodes and number of dimensions. Then specify the node number (starting from 0) and the x- and y-coordinates.

#### node coordinates ####
# npoints ndims 0 0
  13      2     0 0
# i    xi       yi
  0    0.0      0.0
  1    0.0    -35.0e3 
  2    0.0   -150.0e3 
  3  500.0e3 -150.0e3 
  4  500.0e3  -35.0e3
  5  500.0e3    0.0
  6  150.0e3 -150.0e3 
  7  350.0e3 -150.0e3
  8  380.0e3  -35.0e3
  9  250.0e3  -39.0e3
 10  120.0e3  -35.0e3
 11  300.0e3  -35.0e3
 12  200.0e3  -35.0e3

2. Segments As in the example .poly file, specify the number of total segments connecting any 2 nodes. Then specify the segment number (starting from 0) and the nodes it connects (e.g. in the picture of rifting-2d.poly's scheme above, segment 0 connects nodes 0 and 1. Segment 9 connects nodes 10 and 12.) Finally, assign a boundary flag. Flags:

• 0: not a boundary
• 1: left boundary (x0)
• 2: right boundary (x1)
• 16: bottom boundary (z0)
• 32: top boundary (z1)

#### segments ####
# nsegments 1
  16        1
# j  pj0  pj1  bdry_flag
  0   0    1    1  #  1: left (x0)
  1   1    2    1
  2   2    6   16  # 16: bottom (z0)
  3   6    7   16
  4   7    3   16
  5   3    4    2  #  2: right (x1)
  6   4    5    2
  7   5    0   32  # 32: top (z1)
  8   1   10    0  #  0: not a boundary
  9  10   12    0
 10  12    9    0
 11   9   11    0
 12  11    8    0
 13   8    4    0
 14  10    6    0
 15   8    7    0

3. Holes In tectonic moeling, there is no reason to deal with an undergroun empty space.

#### holes, must be 0 ####
0

4. Regions As in the example .poly file, specify the number of total regions. Then specify the region number (starting from 0) and a point within that region (we recommend choosing a fairly central node here). The mattype specifies which value in the .cfg file [mat] paramter should be applied to the region. Finally, specify the max element size (m^2) for the region. If there is no upper limit on element size, use -1.

#### regions ####
# nregions
  4
# k  xk    zk   mattype  size
  0 250e3 -20e3 0        2e7  # max. element size (in m^2)
  1 250e3 -80e3 1        4e7
  2   1e3 -80e3 1        -1   # no upper limit on elem size
  3 450e3 -80e3 1        -1