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<p style="margin-top:0;margin-bottom:0">Hello,</p>
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<p style="margin-top:0;margin-bottom:0">I have quite a simple problem, however I can't find in the tutorials/elsewhere how to achieve what I want. I want to define some dummy geometry in order to control the mesh size. I've constructed a very simple example
to show what I mean:</p>
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<p style="margin-top:0;margin-bottom:0">//</p>
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<span style="font-variant-ligatures: no-common-ligatures">// Gmsh project created on Tue Aug 14 17:02:15 2018</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">// Define domain - square</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">L1 = 5;</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">domain_lc = 1;</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Point(1) = {-L1, L1, 0, domain_lc};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Point(2) = {-L1, -L1, 0, domain_lc};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Point(3) = {L1, -L1, 0, domain_lc};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Point(4) = {L1, L1, 0, domain_lc};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Line(1) = {1:4,1};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Line Loop(1) = {1};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">// Define object in flow - circle</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">L2 = 0.5;</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">boundary_lc = 0.05;</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Point(5) = {0, 0, 0, boundary_lc};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Point(6) = {L2, 0, 0, boundary_lc};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Point(7) = {-L2, 0, 0, boundary_lc};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Circle(2) = {7,5,6};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Circle(3) = {6,5,7};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Line Loop(2) = {2, 3};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Plane Surface(1) = {1, 2};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">// Define dummy geometry for refined area - trapezium</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">refine1_lc = 0.1;</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Point(8) = {-1, 0.7, 0, refine1_lc};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Point(9) = {2.5, 1.5, 0, refine1_lc};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Point(10) = {2.5, -1.5, 0, refine1_lc};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Point(11) = {-1, -0.7, 0, refine1_lc};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">Line(4) = {8:11,8};</span></p>
<p></p>
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<span style="font-variant-ligatures: no-common-ligatures">Line Loop(3) = {4};</span></p>
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<span style="font-variant-ligatures: no-common-ligatures">//</span></p>
<div><span style="font-variant-ligatures: no-common-ligatures"><br>
</span></div>
<div><span style="font-variant-ligatures: no-common-ligatures">I simply want to enforce the "refined" element size to the trapezium geometry that encloses the circle. So the result would be elements of boundary_lc size on the circle wall, and increase in the
normal (linear) way to the refine1_lc size at the dummy geometry, then continue to the outer domain element size.</span></div>
<div><span style="font-variant-ligatures: no-common-ligatures"><br>
</span></div>
<div><span style="font-variant-ligatures: no-common-ligatures">How do I include the dummy geometry in the mesh definition? I'm aware of the box field for example, however I'd like more complex shaped refinement, and the more gradual change in element size.</span></div>
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<div><span style="font-variant-ligatures: no-common-ligatures">Any help would be greatly appreciated.</span></div>
<div>Kind Regards,</div>
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<div>Nathan Ricks</div>
<div>Vrije Universiteit Brussel</div>
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