In Kratos, information about the geometry of the problem is contained in files having the .mdpa extension.
A detailed description of the mdpa file format is available here.
The MPMApplication requires two mdpa files, typically named file_name_Grid.mdpa and file_name_Body.mdpa, with the suffixes _Grid and _Body highlighting their distinct roles.
file_name_Grid.mdpa: contains information about the nodes, elements and conditions of the background grid. This grid is used for computing the Finite Element solution and provides the domain where the material points move.file_name_Body.mdpa: defines the initial mesh discretisation of the continuum to be simulated by means of the Material Point Method. Indeed, in theMPMApplication, the body is first discretised with a mesh and then a certain number of material points (based on theMATERIAL_POINTS_PER_ELEMENTparameter defined in theParticleMaterials.jsonfile) are placed within each element of the mesh. Finally, the mesh initially discretising the body and contained in the filefile_name_Body.mdpais disregarded, therefore serving only to define the initial position of the material points.
file_name_Grid.mdpa
Begin ModelPartData
// VARIABLE_NAME value
End ModelPartData
Begin Properties 0
End Properties
Begin Nodes
1 -7.13647000000000000 -2.77405000000000000 0.0
2 -7.136469999999999 0 -1.04399666666666650 0.0
3 -5.148614285714286 0 -2.77405000000000000 0.0
4 -5.404419192431123 0 -0.17896999999999963 0.0
5 -7.13647000000000000 +0.68605666666666700 0.0
6 -3.70035665111947360 -0.90015846792814620 0.0
7 -3.16075857142857330 -2.77405000000000000 0.0
11 -3.91619588299583340 +0.88743014490059560 0.0
12 -7.13647000000000000 +2.41611000000000000 0.0
13 -2.16683071428571640 -1.04199919243112230 0.0
14 -5.148614285714286 0 +2.41611000000000000 0.0
17 -1.17290285714285810 -2.77405000000000000 0.0
18 -2.16683071428571640 +0.68405919243112300 0.0
20 -3.16075857142857330 +2.41611000000000000 0.0
21 -0.17897500000000166 -1.04199919243112230 0.0
22 -0.17897500000000166 +0.68405919243112300 0.0
23 -1.17290285714285810 +2.41611000000000000 0.0
24 0.814952857142855300 -2.77405000000000000 0.0
25 1.808880714285713000 -1.04199919243112320 0.0
26 0.814952857142855300 +2.41611000000000000 0.0
27 1.808880714285713000 +0.68405919243112300 0.0
30 2.802808571428570000 -2.77405000000000000 0.0
32 3.317802552771939000 -0.87099133333333360 0.0
34 2.802808571428570000 +2.41611000000000000 0.0
35 3.649111838486223000 +0.85906200000000020 0.0
38 4.790664285714286000 -2.77405000000000000 0.0
39 5.046469192431123000 -0.17896999999999963 0.0
40 4.790664285714286000 +2.41611000000000000 0.0
41 6.778520000000000000 -2.77405000000000000 0.0
42 6.778520000000000000 -1.04399666666666650 0.0
43 6.778520000000001000 +0.68605666666666700 0.0
44 6.778520000000000000 +2.41611000000000000 0.0
End Nodes
Begin Elements Element2D3N
1 0 12 5 14
2 0 2 1 3
3 0 42 43 39
4 0 5 2 4
5 0 41 42 38
6 0 43 44 40
7 0 39 43 40
8 0 42 39 38
9 0 4 2 3
10 0 5 4 14
11 0 23 20 18
12 0 3 7 6
13 0 30 38 32
14 0 34 26 27
15 0 17 24 21
16 0 40 34 35
17 0 20 14 11
18 0 7 17 13
19 0 26 23 22
20 0 24 30 25
21 0 18 20 11
22 0 18 11 6
23 0 6 11 4
24 0 4 11 14
25 0 6 4 3
26 0 21 24 25
27 0 21 25 27
28 0 27 25 32
29 0 32 25 30
30 0 22 23 18
31 0 22 18 13
32 0 13 18 6
33 0 13 6 7
34 0 32 38 39
35 0 32 39 35
36 0 35 39 40
37 0 32 35 27
38 0 27 35 34
39 0 27 26 22
40 0 27 22 21
41 0 21 22 13
42 0 21 13 17
End Elements
Begin SubModelPart Grid
Begin SubModelPartNodes
1
2
3
4
5
6
7
11
12
13
14
17
18
20
21
22
23
24
25
26
27
30
32
34
35
38
39
40
41
42
43
44
End SubModelPartNodes
Begin SubModelPartElements
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
End SubModelPartElements
End SubModelPart
Begin SubModelPart DISPLACEMENT_BCs
Begin SubModelPartNodes
1
3
7
17
24
30
38
41
End SubModelPartNodes
End SubModelPart
file_name_Body.mdpa
Begin ModelPartData
// VARIABLE_NAME value
End ModelPartData
Begin Properties 0
End Properties
Begin Nodes
8 -3.8769883038607390 -0.42505600000022326 0.0
9 -2.9082800012962800 -0.98434000000044710 0.0
10 -3.8769883032125985 +0.69351200112283560 0.0
15 -1.9395716961392613 -0.42505600000022390 0.0
16 -2.9082800000000000 +1.25279600000044700 0.0
19 -1.9395716954911204 +0.69351199887761120 0.0
28 2.34508276758495500 -0.94395950357364110 0.0
29 2.34508276818629870 +0.09384750461520013 0.0
31 3.24384999879731100 -1.46286300714728260 0.0
33 3.24385000000000000 +0.61275100714728270 0.0
36 4.14261723241504500 -0.94395950357364180 0.0
37 4.14261723301638900 +0.09384750253208292 0.0
End Nodes
Begin Elements MPMUpdatedLagrangian2D3N // Body1
43 0 16 10 9
44 0 8 9 10
45 0 15 19 16
46 0 9 15 16
End Elements
Begin Elements MPMUpdatedLagrangian2D3N // Body2
47 0 33 29 31
48 0 28 31 29
49 0 36 37 33
50 0 31 36 33
End Elements
Begin SubModelPart Body1
Begin SubModelPartNodes
8
9
10
15
16
19
End SubModelPartNodes
Begin SubModelPartElements
43
44
45
46
End SubModelPartElements
End SubModelPart
Begin SubModelPart Body2
Begin SubModelPartNodes
28
29
31
33
36
37
End SubModelPartNodes
Begin SubModelPartElements
47
48
49
50
End SubModelPartElements
End SubModelPart