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<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;">If I specify a 2-D mesh in Gmsh so that it outputs all 2-D elements it has constructed, along with some (not necessarily proper) subset of 1-D elements, should the collection of
nodes specifying a 1-D element be a subset of the nodes specifying some 2-D element?
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<div>I ask because I have the following case where a couple 1-D elements cross a crack in the mesh inserted using the Crack plugin:</div>
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<div>// File: crack.geo </div>
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<div>// Characteristic length</div>
<div>lc = 1;</div>
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<div>// Point: X, Y, Z coordinates, & characteristic length setting elt size</div>
<div>Point(1) = {0, 0, 0, lc} ;</div>
<div>Point(2) = {1, 0, 0, lc} ;</div>
<div>Point(3) = {1, 1, 0, lc} ;</div>
<div>Point(4) = {0, 1, 0, lc} ;</div>
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<div>// Lines defined by lists of numbers:</div>
<div>Line(1) = {1, 2} ;</div>
<div>Line(2) = {2, 3} ;</div>
<div>Line(3) = {3, 4} ;</div>
<div>Line(4) = {4, 1} ;</div>
<div>Line(5) = {1, 3} ;</div>
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<div>// Line loops to construct surfaces</div>
<div>Line Loop(1) = {1, 2, -5} ;</div>
<div>Line Loop(2) = {5, 3, 4} ;</div>
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<div>// Surfaces for meshing</div>
<div>Plane Surface(1) = {1} ;</div>
<div>Plane Surface(2) = {2} ;</div>
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<div>Physical Point(13) = {1, 3};</div>
<div>Physical Surface(201) = {1} ;</div>
<div>Physical Surface(202) = {2} ;</div>
<div>Physical Line(105) = {5} ;</div>
<div>Physical Line(104) = {1, 2, 3, 4};</div>
<div>// end of file</div>
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<div style="font-family:Tahoma; font-size:13px">I run that using "gmsh -2 -o crack.msh crack.geo" and then post-process using the crack plugin with the file</div>
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<div style="font-family:Tahoma; font-size:13px">// File: crack2.geo</div>
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<div>// Add cracks to duplicate nodes</div>
<div>Merge "crack.msh" ;</div>
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<div>// Duplicate around cathode-separator interface</div>
<div>Plugin(Crack).Dimension = 1 ;</div>
<div>Plugin(Crack).PhysicalGroup = 105 ;</div>
<div>Plugin(Crack).OpenBoundaryPhysicalGroup = 13 ;</div>
<div>Plugin(Crack).Run ;</div>
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<div style="font-family:Tahoma; font-size:13px">// end of file</div>
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<div style="font-family:Tahoma; font-size:13px">and the command "gmsh -2 -o crack2.msh crack2.geo".</div>
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<div style="font-family:Tahoma; font-size:13px">The file "crack2.msh" consists of:</div>
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<div>MeshFormat</div>
<div>2.2 0 8</div>
<div>$EndMeshFormat</div>
<div>$Nodes</div>
<div>8</div>
<div>1 0 0 0</div>
<div>2 1 1 0</div>
<div>3 1 0 0</div>
<div>4 0 1 0</div>
<div>5 0.4999999999986928 0.4999999999986928 0</div>
<div>6 0 0 0</div>
<div>7 1 1 0</div>
<div>8 0.4999999999986928 0.4999999999986928 0</div>
<div>$EndNodes</div>
<div>$Elements</div>
<div>14</div>
<div>1 15 2 13 1 1</div>
<div>2 15 2 13 3 2</div>
<div>3 1 2 104 1 1 3</div>
<div>4 1 2 104 2 3 2</div>
<div>5 1 2 104 3 2 4</div>
<div>6 1 2 104 4 4 1</div>
<div>7 1 2 105 5 1 5</div>
<div>8 1 2 105 5 5 2</div>
<div>9 1 2 105 6 6 8</div>
<div>10 1 2 105 6 8 7</div>
<div>11 2 2 201 1 6 3 8</div>
<div>12 2 2 201 1 3 7 8</div>
<div>13 2 2 202 2 1 5 4</div>
<div>14 2 2 202 2 5 2 4</div>
<div>$EndElements</div>
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<div>What I find strange about this output is that the 1-D element 3 is an edge between nodes 1 and 3, but that edge straddles the crack I placed in the mesh, and it seems like that element should be an edge between nodes 6 and 3. Similarly, 1-D element 4 is
an edge between nodes 3 and 2, but that edge also straddles the crack I placed in the mesh, and it seems like that element should be an edge between nodes 3 and 7. There is no 2-D element containing nodes 1 and 3 together, nor is there a 2-D element containing
nodes 3 and 2 together. Is this behavior supposed to happen?</div>
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Geoff<br>
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