<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40" dir="ltr"><head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:Wingdings;
panose-1:5 0 0 0 0 0 0 0 0 0;}
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
font-size:11.0pt;
font-family:"Calibri",sans-serif;
mso-fareast-language:EN-US;}
p.MsoListParagraph, li.MsoListParagraph, div.MsoListParagraph
{mso-style-priority:34;
margin-top:0cm;
margin-right:0cm;
margin-bottom:0cm;
margin-left:36.0pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;
mso-fareast-language:EN-US;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Calibri",sans-serif;
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri",sans-serif;
mso-fareast-language:EN-US;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:72.0pt 72.0pt 72.0pt 72.0pt;}
div.WordSection1
{page:WordSection1;}
/* List Definitions */
@list l0
{mso-list-id:1263028945;
mso-list-type:hybrid;
mso-list-template-ids:1055145086 -1140785808 135462915 135462917 135462913 135462915 135462917 135462913 135462915 135462917;}
@list l0:level1
{mso-level-start-at:0;
mso-level-number-format:bullet;
mso-level-text:-;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:"Calibri",sans-serif;
mso-fareast-font-family:Calibri;}
@list l0:level2
{mso-level-number-format:bullet;
mso-level-text:o;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:"Courier New";}
@list l0:level3
{mso-level-number-format:bullet;
mso-level-text:\F0A7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Wingdings;}
@list l0:level4
{mso-level-number-format:bullet;
mso-level-text:\F0B7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Symbol;}
@list l0:level5
{mso-level-number-format:bullet;
mso-level-text:o;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:"Courier New";}
@list l0:level6
{mso-level-number-format:bullet;
mso-level-text:\F0A7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Wingdings;}
@list l0:level7
{mso-level-number-format:bullet;
mso-level-text:\F0B7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Symbol;}
@list l0:level8
{mso-level-number-format:bullet;
mso-level-text:o;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:"Courier New";}
@list l0:level9
{mso-level-number-format:bullet;
mso-level-text:\F0A7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Wingdings;}
ol
{margin-bottom:0cm;}
ul
{margin-bottom:0cm;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="NL-BE" style="text-align:left; direction:ltr;"><div>Add</div><div><br></div><div>Coherence;</div><div><br></div><div>and you'll be fine.</div><div><br></div><div><br></div><div>On Fri, 2020-08-14 at 10:43 +0000, Bart Deschoolmeester wrote:</div><blockquote type="cite" style="margin:0 0 0 .8ex; border-left:2px #729fcf solid;padding-left:1ex">
<div class="WordSection1">
<p class="MsoNormal"><span lang="EN-GB">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I am a beginner.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">While working on a larger 3D project I noticed some gaps and overlaps.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I plan to simulate the heat transfer.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I assume gaps and overlaps are to be avoided to get a good simulation. Correct?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I tracked down the origin of the gaps and overlaps and it seems to be the extrude command causing the trouble.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">The file below draws a rectangle with a round hole in the middle. In the hole a ring (annulus) is drawn.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">If I create the ring with the BooleanDifference command (difference of two circles): all works fine. All triangles line up perfectly around the contact line of ring and hole.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">If I create the ring with the Extrude command, things don’t line up.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Of course I could opt for the booleandifference command for this problem but:<o:p></o:p></span></p>
<ul style="margin-top:0cm" type="disc">
<li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo1"><span lang="EN-GB">I cannot use this booleandifference solution in my 3D problem<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo1"><span lang="EN-GB">I can imagine these holes and overlaps also being produced in other curved contact surfaces.<o:p></o:p></span></li></ul>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Is this a bug in GMSH or the be expected in more elaborate meshes?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">How can it be resolved?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Thank you!<o:p></o:p></span></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid windowtext 1.0pt;padding:0cm 0cm 1.0pt 0cm">
<p class="MsoNormal" style="border:none;padding:0cm"><span lang="EN-GB">Bart<o:p></o:p></span></p>
<p class="MsoNormal" style="border:none;padding:0cm"><span lang="EN-GB"><o:p> </o:p></span></p>
</div>
<p class="MsoNormal"><span lang="EN-GB">KanR = DefineNumber[ 0.1, Name "Parameters/KanR" ];<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">KanMeshsize = DefineNumber[ 0.05, Name "Parameters/KanMeshsize" ];<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">SetFactory("OpenCASCADE");<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Rectangle(1) = {-2.5, -2.5, 0, 5, 5, 0};<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Circle(5) = {0, 0, 0, KanR, 0, 2*Pi};<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Curve Loop(2) = {5};<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Plane Surface(2) = {2};<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">BooleanDifference{ Surface{1}; Delete; }{ Surface{2}; Delete; }<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Point(15) = {0, KanR, 0};<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Point(16) = {0, KanR-0.05, 0};<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Line(20) = {15, 16};<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Extrude {{0, 0, 1}, {0, 0, 0}, 2*Pi} {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"> Curve{20}; <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">}<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Field[1] = Distance;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">//+<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Field[1].EdgesList = {5};<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">//+<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Field[1].NNodesByEdge = 50;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">//+<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Field[2] = Threshold;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">//+<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Field[2].DistMax = 2.5;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">//+<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Field[2].DistMin = 0;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">//+<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Field[2].IField = 1;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">//+<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Field[2].LcMax = 0.25;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">//+<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Field[2].LcMin = KanMeshsize ;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Background Field = 2;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Mesh.CharacteristicLengthExtendFromBoundary = 0;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Mesh.CharacteristicLengthFromPoints = 0;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Mesh.CharacteristicLengthFromCurvature = 0;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
</div>
<pre>_______________________________________________</pre><pre>gmsh mailing list</pre><a href="mailto:gmsh@onelab.info"><pre>gmsh@onelab.info</pre></a><pre><br></pre><a href="http://onelab.info/mailman/listinfo/gmsh"><pre>http://onelab.info/mailman/listinfo/gmsh</pre></a><pre><br></pre></blockquote></body></html>