Example: Truncated Brick Mesh with Surface Regions
The objective is to create a structured mesh with materials and truncation defined by surfaces. The command createpts/brick is used to build a hex mesh. The hex mesh is colored by surface regions and then connected into a Delaunay tet mesh. Material cell colors are interpolated on to the tet mesh to maintain the cube shapes of the hex elements. When truncated the mesh is stair-stepped instead of dips and peaks if truncating by surface directly. The stair-step top needs careful methods to find the boundary tops and sides. The zone_outside_minmax is used in this example.
The result will have stair-step geometries by will satisfy the Delaunay critera for modeling applications.
This example command file creates the surfaces and mesh, there are no input files to read except the macro file included here.
LaGriT command file: lagrit_input_brick_trunc.lgi.txt
LaGriT macro called by command file: reset_truncated_nodes_imt.mlgi.txt
LaGriT output report: lagrit_output_brick_trunc.txt
Input Regular Hex Mesh and Surfaces Output Truncated tet Mesh
Truncated tet mesh with outside top boundary nodes
Truncated tet mesh with nodes defined by material regions
Steps for this Example:
Step 1. Create hex mesh using createpts/brick multiple calls for change in vertical resolution.
define/XMIN/ 0.
define/YMIN/ 0.
define/ZMIN/ 0.
define/XMAX/ 20.
define/YMAX/ 10.
define NX 21
define NY 11
# Vertical spacing
define/ZMAX/ 18.
define/Z2 / 10.
define/Z1 / 5.
define/ZMIN/ 0.
cmo/create/cmohex///hex
cmo/select/cmohex
# Vertical spacing from middle to top
createpts/brick/xyz/NX NY 28 / XMIN YMIN Z2 / XMAX YMAX ZMAX
# Vertical spacing from middle 1 to middle 2
createpts/brick/xyz/NX NY 11 / XMIN YMIN Z1 / XMAX YMAX Z2
# Vertical spacing bottom to middle
createpts/brick/xyz/NX NY 6 / XMIN YMIN ZMIN / XMAX YMAX Z1
cmo/printatt/cmohex/ -xyz- minmax
quality
Step 2. Create or Read Surfaces to define Material Regions
# Use x coordinates to compute z based on sin()
# y coordinate detirmines length of surface
define / XMAX / 20.
define / NX / 40
define / YMAX / 10.
define / NY / 10
define SCALE_VAL 2.
cmo / create / mosurf / / / quad
cmo select mosurf
quadxy /NX NY/0. 0. 0./ XMAX 0. 0./XMAX YMAX 0./0. YMAX 0./ 1 1 1
createpts/brick/xyz/NX,NY,1/1 0 0 / connect
math/sin/mosurf/zic/1,0,0/mosurf/xic
scale / 1 0 0 / relative / xyz / SCALE_VAL SCALE_VAL SCALE_VAL
cmo / setatt / mosurf / imt / 1 0 0 / 1
cmo / setatt / mosurf / itetclr / 1 0 0 / 1
resetpts / itp
cmo / printatt / mosurf / -xyz- / minmax
trans / 1 0 0 / 0. 0. 0. / -1. -1. 8.0
dump / surf_sin_01.inp / mosurf
cmo/printatt/mosurf/ zic minmax
cmo/copy/mosurf2/mosurf
cmo/select/mosurf2
trans / 1 0 0 / 0. 0. 0. / -1. 0. 6.8
dump / surf_sin_02.inp / mosurf2
cmo/printatt/mosurf2/ zic minmax
Define Geometry using Regions defined by Surfaces
cmo select cmohex
surface / s1 / intrface / sheet / mosurf
surface / s2 / intrface / sheet / mosurf2
# set interfaces equal to one surface
region / r1 / lt s1 and le s2
region / r2 / gt s1 and lt s2
region / r3 / ge s2
# interfaces are not equal to surface
mregion / mr1 / lt s1 and lt s2
mregion / mr2 / gt s1 and lt s2
mregion / mr3 / gt s2
setpts
settets
resetpts/itp
Connect point distribution into Delaunay tet mesh
cmo/create/cmotet
copypts/cmotet/cmohex
# remove duplicate points, reset attributes
filter/1,0,0
rmpoint/compress
cmo / setatt / cmotet / imt / 1 0 0 / 1
cmo / setatt / cmotet / itp / 1 0 0 / 0
# connect without adding points
connect noadd
resetpts / itp
quality
Interpolate Cell and Node Materials from Hex Mesh for brick shaped geometry
interpolate/map/cmotet itetclr /1,0,0/ cmohex itetclr
interpolate/voronoi/cmotet imt /1,0,0/ cmohex imt
cmo/printatt/cmotet/itetclr minmax
# remove cells above material 2
# check for material 3 nodes left behind
eltset/edel/ itetclr / gt 2
rmpoint element eltset,get,edel
rmpoint/compress
resetpts/itp
cmo/printatt/cmotet/itetclr minmax
cmo/printatt/cmotet/imt minmax
# FIX imt of nodes left behind after removal of cells
define CMO cmotet
define MAX_MAT 2
infile reset_truncated_nodes_imt.mlgi
Set Boundary Node Zones
# tag outside nodes and save attributes
# we need to use the max node located in each xyz direction
# normal zone_outside will tag stair-steps incorrectly
dump/ zone_outside_minmax/ tet_max /cmotet/ keepatt
# check geometric coefficients
cmo/setatt/cmotet/imt 1
dump/ stor/ tet_trunc / cmotet
LaGriT Output Report for Mesh Quality
# check geometric coefficients
dump/stor/tet_trunc/cmotet
*** Construct and Compress Sparse Matrix:3D ***
*** Compress Area Coefficient Values ***
AMatbld3d_stor: Matrix compress_eps: 0.1000000E-07
AMatbld3d_stor: Local epsilon: 0.1000000E-14
AMatbld3d_stor: *****Zero Negative Coefficients ******
AMatbld3d_stor: Number of 'zero' (< compress_eps) coefs 0
AMatbld3d_stor: npoints = 7898 ncoefs = 52244
AMatbld3d_stor: Number of unique coefs = 16
AMatbld3d_stor: Maximum num. connections to a node = 7
AMatbld3d_stor: Volume min = 3.7037037E-02
AMatbld3d_stor: Volume max = 1.0000000E+00
AMatbld3d_stor: Total Volume: 3.0251852E+03
AMatbld3d_stor: abs(Aij/xij) min = 0.0000000E+00
AMatbld3d_stor: abs(Aij/xij) max = 3.3750000E+00
AMatbld3d_stor: (Aij/xij) max = 0.0000000E+00
AMatbld3d_stor: (Aij/xij) min = -3.3750000E+00
AMatbld3d_stor Matrix coefficient values stored as scalar area/distance
AMatbld3d_stor Matrix compression used for graph and coefficient values
ascii STOR file written with name tet_trunc.stor
*** SPARSE COEFFICIENT MATRIX _astor SUCCESSFUL ***
3D Matrix Coefficient file written with name tet_trunc.stor
# check quality
quality
epsilonl, epsilonaspect: 6.2122430E-12 2.3974265E-34
--------------------------------------------
elements with aspect ratio < .01: 0
elements with aspect ratio b/w .01 and .02: 0
elements with aspect ratio b/w .02 and .05: 0
elements with aspect ratio b/w .05 and .1 : 0
elements with aspect ratio b/w .1 and .2 : 0
elements with aspect ratio b/w .2 and .5 : 20686
elements with aspect ratio b/w .5 and 1. : 17649
min aspect ratio = 0.2950E+00 max aspect ratio = 0.1000E+01
epsilonvol: 7.4672778E-10
---------------------------------------
element volumes b/w 0.4938E-01 and 0.7235E-01: 20310
element volumes b/w 0.7235E-01 and 0.1060E+00: 11941
element volumes b/w 0.1060E+00 and 0.1553E+00: 0
element volumes b/w 0.1553E+00 and 0.2275E+00: 6026
element volumes b/w 0.2275E+00 and 0.3333E+00: 58
min volume = 4.9382716E-02 max volume = 3.3333333E-01
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38335 total elements evaluated.