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
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
|
<!DOCTYPE html>
<!--[if IE 8]><html class="no-js lt-ie9" lang="en" > <![endif]-->
<!--[if gt IE 8]><!--> <html class="no-js" lang="en" > <!--<![endif]-->
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>fix mesh/surface command — LIGGGHTS v3.X documentation</title>
<link rel="stylesheet" href="_static/css/theme.css" type="text/css" />
<link rel="top" title="LIGGGHTS v3.X documentation" href="index.html"/>
<script src="_static/js/modernizr.min.js"></script>
</head>
<body class="wy-body-for-nav" role="document">
<div class="wy-grid-for-nav">
<nav data-toggle="wy-nav-shift" class="wy-nav-side">
<div class="wy-side-scroll">
<div class="wy-side-nav-search">
<a href="Manual.html" class="icon icon-home"> LIGGGHTS
</a>
<div class="version">
v3.X
</div>
<div role="search">
<form id="rtd-search-form" class="wy-form" action="search.html" method="get">
<input type="text" name="q" placeholder="Search docs" />
<input type="hidden" name="check_keywords" value="yes" />
<input type="hidden" name="area" value="default" />
</form>
</div>
</div>
<div class="wy-menu wy-menu-vertical" data-spy="affix" role="navigation" aria-label="main navigation">
<ul>
<li class="toctree-l1"><a class="reference internal" href="Section_intro.html">1. Introduction</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_start.html">2. Getting Started</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_input_script.html">3. Input Script</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_commands.html">4. Commands</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_gran_models.html">5. Contact models</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_mesh_modules.html">6. Mesh modules</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_packages.html">7. Packages</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_howto.html">8. How-to discussions</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_modify.html">9. Modifying & extending LIGGGHTS(R)-PUBLIC</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_python.html">10. Python interface to LIGGGHTS(R)-PUBLIC</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_errors.html">11. Errors</a></li>
</ul>
</div>
</div>
</nav>
<section data-toggle="wy-nav-shift" class="wy-nav-content-wrap">
<nav class="wy-nav-top" role="navigation" aria-label="top navigation">
<i data-toggle="wy-nav-top" class="fa fa-bars"></i>
<a href="Manual.html">LIGGGHTS</a>
</nav>
<div class="wy-nav-content">
<div class="rst-content">
<div role="navigation" aria-label="breadcrumbs navigation">
<ul class="wy-breadcrumbs">
<li><a href="Manual.html">Docs</a> »</li>
<li>fix mesh/surface command</li>
<li class="wy-breadcrumbs-aside">
<a href="_sources/fix_mesh_surface.txt" rel="nofollow"> View page source</a>
<a href="http://www.cfdem.com"> Website</a>
<a href="Section_commands.html#comm" rel="nofollow"> Commands</a>
</li>
</ul>
<hr/>
</div>
<div role="main" class="document" itemscope="itemscope" itemtype="http://schema.org/Article">
<div itemprop="articleBody">
<div class="section" id="fix-mesh-surface-command">
<span id="index-0"></span><h1>fix mesh/surface command<a class="headerlink" href="#fix-mesh-surface-command" title="Permalink to this headline">¶</a></h1>
</div>
<div class="section" id="fix-mesh-surface-planar-command">
<h1>fix mesh/surface/planar command<a class="headerlink" href="#fix-mesh-surface-planar-command" title="Permalink to this headline">¶</a></h1>
<div class="section" id="syntax">
<h2>Syntax<a class="headerlink" href="#syntax" title="Permalink to this headline">¶</a></h2>
<div class="highlight-python"><div class="highlight"><pre>fix ID group-ID mesh/surface data_keyword data_value premesh_keywords premesh_values mesh_keywords mesh_values surface_keywords surface_values
fix ID group-ID mesh/surface/module_list data_keyword data_value premesh_keywords premesh_values mesh_keywords mesh_values surface_keywords surface_values module_keywords module_values
fix ID group-ID mesh/surface/planar data_keyword data_value premesh_keywords premesh_values mesh_keywords mesh_values surface_keywords surface_values
</pre></div>
</div>
<ul class="simple">
<li>ID, is documented in <a class="reference internal" href="fix.html"><em>fix</em></a> command.</li>
<li>mesh/surface or mesh/surface/planar = style name of this fix command</li>
<li>module_list = list of mesh modules separated by /</li>
<li>one data_keyword/data_value pair needs to be appended</li>
<li>data_keyword = <em>file</em> or <em>fix</em></li>
</ul>
<pre class="literal-block">
<em>file</em> value = name of STL or VTK file containing the triangle mesh data
<em>fix</em> value = id of a fix that can generate meshes (e.g. this one using the <em>extrude_planar</em> keyword)
</pre>
<ul class="simple">
<li>zero or more premesh_keywords/premesh_value pairs may be appended</li>
<li>premesh_keyword = <em>type</em> or <em>precision</em> or <em>heal</em> or <em>min_feature_length</em> or <em>element_exclusion_list</em> or <em>verbose</em></li>
</ul>
<pre class="literal-block">
<em>type</em> value = atom type (material type) of the wall imported from the STL file
<em>region</em> value = ID of <a class="reference internal" href="region.html"><em>region</em></a> to filter elements which are imported
<em>precision</em> value = length mesh nodes this far away at maximum will be recognized as identical (length units)
<em>heal</em> value = auto_remove_duplicates or no
<em>min_feature_length</em> value = exclude element if belongs to an entity where no element is larger than this (length units)
<em>element_exclusion_list</em> values = mode element_exlusion_file
mode = read or write
element_exlusion_file = name of file containing the elements to be excluded
<em>verbose</em> value = yes or no
</pre>
<ul class="simple">
<li>zero or more mesh_keywords/mesh_value pairs may be appended</li>
</ul>
<pre class="literal-block">
mesh_keyword = <em>scale</em> or <em>move</em> or <em>rotate</em> or <em>temperature</em> or <em>mass_temperature</em> or <em>extrude_planar</em>:l
<em>scale</em> value = factor
factor = factor to scale the mesh in x-, y-, and z-direction (double value)
<em>move</em> values = mx my mz
mx my mz = move the mesh by this extent in x-, y-, and z-direction (length units)
<em>rotate</em> values = axis ax ay az angle ang
axis = obligatory keyword
ax, ay, az = axis vector for rotation (length units)
angle = obligatory keyword
ang = rotation angle (degrees)
<em>temperature</em> value = T0
T0 = Temperature of the wall (temperature units)
<em>mass_temperature</em> value = mt0
mt0 = mass (mass units) assumed for temperature update in the frame of <code class="xref doc docutils literal"><span class="pre">surface</span> <span class="pre">sphere/heatable</span></code>
<em>extrude_planar</em> value = length
length = length (length units) that a planar mesh is extruded in anti-normal direction
</pre>
<ul class="simple">
<li>zero or more surface_keywords/surface_value pairs may be appended</li>
<li>surface_keyword = <em>surface_vel</em> or <em>surface_ang_vel</em> or <em>curvature</em> or <em>curvature_tolerant</em></li>
</ul>
<pre class="literal-block">
<em>surface_vel</em> values = vx vy vz
vx vy vz = conveyor belt surface velocity (velocity units)
<em>surface_ang_vel</em> values = origin ox oy oz axis ax ay az omega om
origin = mandatory keyword
ox oy oz = origin of rotation (length units)
axis = mandatory keyword
ax ay az = axis vector for rotation (length units)
omega = mandatory keyword
om = rotational velocity around specifyied axis (rad/time units)
<em>curvature</em> value = c
c = maximum angle between mesh faces belonging to the same surface (in degree)
<em>curvature_tolerant</em> value = ct
ct = yes or no
</pre>
<ul class="simple">
<li>zero or more module_keywords/module_value pairs may be appended if a mesh module is used</li>
</ul>
<div class="highlight-python"><div class="highlight"><pre>see the respective mesh module parameter list for details
</pre></div>
</div>
</div>
<div class="section" id="examples">
<h2>Examples<a class="headerlink" href="#examples" title="Permalink to this headline">¶</a></h2>
<div class="highlight-python"><div class="highlight"><pre>fix cad all mesh/surface file mesh.stl type 1
fix cad1 all mesh/surface/stress/deform file meshes/plate.stl type 1 scale 1.0 wear finnie
fix extrude all mesh/surface file plane.stl type 1 extrude_planar 0.1
fix side_walls all mesh/surface fix extrude type 1
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
<p>This fix allows the import of triangular surface mesh wall geometry for granular simulations from
ASCII STL files or legacy ASCII VTK files. Style <em>mesh/surface</em> is a general surface mesh, and
<em>mesh/surface/planar</em> represents a planar mesh. <em>mesh/surface/planar</em> requires the mesh to
consist of only 1 planar face.</p>
<p>The <em>region</em> keyword can be used to filter the elements which are imported. An element is only
imported if all of its vertices is inside the specified <a class="reference internal" href="region.html"><em>region</em></a>. Please note that
the geometric extent of this <a class="reference internal" href="region.html"><em>region</em></a> refer to the unscaled, unmoved, and unrotated
original state of the geometry.</p>
<p>In general, you can apply scaling, offset and rotation to the imported mesh via
keywords <em>scale</em>, <em>move</em>, <em>rotate</em>. Operations are applied in the order as they
are specified. The rotation via <em>rotate</em> is performed around the rotation axis
that goes through the origin (0,0,0) and in the direction of <em>axis</em>.</p>
<p>The group-ID defines which particles will “see” the mesh, in case it is used as a granular wall.</p>
<p>One fix represents one wall with a specific material, where the material is identified
via keyword <em>type</em>. If multiple meshes with different materials are desired, the respective
meshes must be imported with different fix mesh/surface commands.</p>
<p>With the <em>temperature</em> keyword, you can define a constant temperature for a mesh in
conjunction with heat conduction via <code class="xref doc docutils literal"><span class="pre">fix</span> <span class="pre">heat/gran</span></code>. Note that the
actual calculation of the heat transfer happens only if you use the mesh in conjunction
with a granular wall, see <a class="reference internal" href="fix_wall_gran.html"><em>fix wall/gran</em></a>.</p>
<p>The <em>extrude_planar</em> option allows to extrude a planar mesh in direction of the
anti-normal by a specified length values. After a <em>run 0</em> command this fix will
hold the generated triangles which can be used in another <em>mesh/surface</em> fix
that uses the <em>fix</em> instead of <em>file</em> keyword.</p>
<p>With the optional <em>surface_vel</em> keyword, you can specify the imported mesh as conveyor belt.
The velocity direction for each mesh face is given by the projection of the conveyor
belt velocity parallel to the mesh face, the velocity magnitude for each mesh face is
equal to the conveyor belt velocity. This ensures the model makes sense also in case
the mesh is curved. Likewise, the optional rotation model activated via keyword
<em>surface_ang_vel</em> mimics rotational motion of the mesh (e.g. for modeling a shear cell)</p>
<p><strong>Mesh modules:</strong></p>
<p>The “mesh/surface” fix allows for several mesh modules to be appended. A
complete list of the available mesh modules can be found in <a class="reference internal" href="Section_mesh_modules.html"><em>Section mesh modules</em></a>.</p>
<p>Note that some of these modules are dependent on each other and some are mutually exclusive.
The order of the mesh modules is important and the arguments for each mesh module need to
be appended in the same order as the modules.</p>
<div class="admonition warning">
<p class="first admonition-title">Warning</p>
<p class="last">When using the deform, heattransfer or liquidtransfer module and
periodic boundary conditions the mesh needs to fulfill the following properties:
(i) a triangle is not allowed to be in contact with itself through periodic
boundaries,
(ii) if two triangles are in contact inside the domain, they are not
allowed to be in contact through periodic boundaries.
Note that these restrictions are not validated by LIGGGHTS(R)-PUBLIC and must be
ensured by the user.</p>
</div>
<p><strong>Quality checks / error and warning messages:</strong></p>
<p>LIGGGHTS(R)-PUBLIC checks a couple of quality criteria upon loading a mesh. LIGGGHTS(R)-PUBLIC tries
to give you as much information about the issue as possible.</p>
<p>Warning messages:</p>
<ul class="simple">
<li>There should be no angle < 0.5 degrees in any element (soft limit for angles)</li>
<li>All nodes should be within the simulation box</li>
</ul>
<p>If any of the above rules is not fulfilled, a warning is generated. Keyword
<em>verbose</em> controls if details about the warning are written to the screen.</p>
<p>Error messages:</p>
<ul class="simple">
<li>The <em>curvature</em> must not be larger than any angle in any mesh element</li>
<li>There must be no element with an angle < 0.0181185 degrees in any element (hard limit for angles)</li>
<li>The number of neighbor elements must be <= 5 for any element</li>
<li>Mesh elements must not be duplicate</li>
<li>Coplanar mesh elements that share an edge must not overlap</li>
<li>Mesh elements must not leave the simulation domain (based on the center of the element)</li>
</ul>
<p>If any of the obove rules is not fulfilled, an error is generated and
LIGGGHTS(R)-PUBLIC halts. Error messages are always <em>verbose</em>.
If LIGGGHTS(R)-PUBLIC halts due to the last error, you might think about (a)
changing the mesh import parameters (<em>scale</em>, <em>move</em>, <em>rotate</em>), (b)
changing the mesh dynamics if a <a class="reference internal" href="fix_move_mesh.html"><em>fix move/mesh</em></a> is
applied or using <a class="reference internal" href="boundary.html"><em>boundary m m m</em></a></p>
<p>There are a couple of features that help you read / repair a mesh which
can not be read correctly in the first place:</p>
<ul class="simple">
<li><em>precision</em></li>
<li><em>curvature</em></li>
<li><em>heal</em></li>
<li><em>element_exclusion_list</em></li>
<li><em>min_feature_length</em></li>
<li><em>curvature_tolerant</em></li>
</ul>
<p>The <em>precision</em> keyword specifies how far away mesh nodes can be at maximum to
be recognized as identical. This is important for building the topology of the mesh
and identify elements as neighbors. Normally, this should only be changed if the mesh file
you are working with is suffering from precsion / round-off issues.</p>
<p>The <em>curvature</em> keyword lets you specify up to which angle between two triangles the
triangles should be treated as belonging to the same surface (e.g. useful for bends).
This angle is used to decide if (a) contact history is copied from one triangle to
the other as the contact point proceeds and (b) if edge and corner interaction is
calculated.</p>
<p>If LIGGGHTS(R)-PUBLIC stalls because of duplicate elements, you can try setting
<em>heal</em> to auto_remove_duplicates. LIGGGHTS(R)-PUBLIC will then try to heal the geometry
by removing duplicate elements.</p>
<p>With the optional <em>element_exclusion_list</em> keyword is used in mode ‘write’, LIGGGHTS(R)-PUBLIC
will write a list of elements which</p>
<ul class="simple">
<li>have more than the allowed 5 face neighbors per surface</li>
<li>have an angle below 0.0181185 degrees</li>
<li>are duplicate</li>
</ul>
<p>element to a file. The ‘read’ mode can then use this file and will skip the elements in
the list. However, you can also manually write such a file to exclude elements you do not
want to have included</p>
<div class="admonition warning">
<p class="first admonition-title">Warning</p>
<p class="last">The <em>element_exclusion_list write</em> model works in serial only. However,
this is not a real restriction, since you can generate the exclusion lists in serial,
but then read them to import the mesh into a parallel simulation</p>
</div>
<div class="admonition warning">
<p class="first admonition-title">Warning</p>
<p class="last">If you use the ‘heal’ or ‘element_exclusion_list’ keywords, you should
check the changes to the geometry, e.g. by using a <a class="reference internal" href="dump.html"><em>dump mesh/stl</em></a> command.</p>
</div>
<p>With the <em>min_feature_length</em> option, you can exlude elements which do not belong
to an entity which has any element larger than <em>min_feature_length</em>. In this context,
‘entity’ is defined by the ‘neighborhood’ of the element.
<em>min_feature_length</em> also writes to the exclusion list, and can thus only be used along
with the ‘element_exclusion_list’ feature. This feature is only available in the
PREMIUM version of LIGGGHTS.</p>
<p>The <em>curvature_tolerant</em> keyword can simply turn off the check that
the <em>curvature</em> must not be larger than any angle in any mesh element.
This is typically not recommended, but can be used as a last resort measure.</p>
</div>
<div class="section" id="restart-fix-modify-output-run-start-stop-minimize-info">
<h2>Restart, fix_modify, output, run start/stop, minimize info<a class="headerlink" href="#restart-fix-modify-output-run-start-stop-minimize-info" title="Permalink to this headline">¶</a></h2>
<p>This fix writes the STL data to binary <a class="reference internal" href="restart.html"><em>restart files</em></a> to be able to
correctly resume the simulation in case the mesh is moved. None of the
<a class="reference internal" href="fix_modify.html"><em>fix_modify</em></a> options are relevant to this fix directly. However,
some mesh modules do have fix_modify options, please refer to the respective module
for further information.</p>
<p>No global scalar or vector or per-atom quantities are stored by this fix for access by
various <span class="xref std std-ref">output commands</span>. No parameter of this fix
can be used with the <em>start/stop</em> keywords of the <a class="reference internal" href="run.html"><em>run</em></a> command.
This fix is not invoked during <code class="xref doc docutils literal"><span class="pre">energy</span> <span class="pre">minimization</span></code>.</p>
</div>
<div class="section" id="restrictions">
<h2>Restrictions<a class="headerlink" href="#restrictions" title="Permalink to this headline">¶</a></h2>
<p>To date, only ASCII STL and VTK files can be read (binary is not supported).
In the current implementation, each processor allocates memory for the whole
geometry, which may lead to memory issues for very large geometries .
It is not supported to use both the moving mesh and the conveyor belt feature.</p>
</div>
<div class="section" id="related-commands">
<h2>Related commands<a class="headerlink" href="#related-commands" title="Permalink to this headline">¶</a></h2>
<p><a class="reference internal" href="fix_wall_gran.html"><em>fix wall/gran</em></a></p>
<p><strong>Default:</strong> curvature = 0.256235 degrees, precision = 1e-8, verbose = no, heal = no</p>
</div>
</div>
</div>
<div class="articleComments">
</div>
</div>
<footer>
<hr/>
<div role="contentinfo">
<p>
© Copyright 2016, DCS Computing GmbH, JKU Linz and Sandia Corporation.
</p>
</div>
Built with <a href="http://sphinx-doc.org/">Sphinx</a> using a <a href="https://github.com/snide/sphinx_rtd_theme">theme</a> provided by <a href="https://readthedocs.org">Read the Docs</a>.
</footer>
</div>
</div>
</section>
</div>
<script type="text/javascript">
var DOCUMENTATION_OPTIONS = {
URL_ROOT:'./',
VERSION:'v3.X',
LANGUAGE:'None',
COLLAPSE_INDEX:false,
FILE_SUFFIX:'.html',
HAS_SOURCE: true,
SOURCELINK_SUFFIX: ''
};
</script>
<script type="text/javascript" src="_static/jquery.js"></script>
<script type="text/javascript" src="_static/underscore.js"></script>
<script type="text/javascript" src="_static/doctools.js"></script>
<script type="text/javascript" src="_static/js/theme.js"></script>
<script type="text/javascript">
jQuery(function () {
SphinxRtdTheme.StickyNav.enable();
});
</script>
</body>
</html>
|
