<div dir="ltr"><div class="gmail_default" style="font-family:verdana,sans-serif">I've just started using gmsh. I am trying to create a mesh of quads for input into a moment method solver for antennas. As a trial case, I'm trying a simple square microstrip patch antenna. The geometry consists of an outer perimeter representing the ground plane and an inner area where the patch element is. One edge on the inner section must have a sub-section of exactly 1 segment and of specific width and location (corresponding to the attachment of a microstrip transmission line). So, I've created Lines with endpoints at the needed locations. Meshing with triangles works fine. However, when I use Recombine to generate quads, the subsection/segment of interest gets split in two. I've tried setting various values for characteristic length but to no avail. Here's a copy of my input file:</div>
<div class="gmail_default" style="font-family:verdana,sans-serif">//~~~~~~~~~~~~~~~~~~~~~~~~</div><div class="gmail_default" style><div class="gmail_default" style><font face="courier new, monospace">wo = 0.125;</font></div>
<div class="gmail_default" style><font face="courier new, monospace">lo = 0.125;</font></div><div class="gmail_default" style><font face="courier new, monospace">nwo = 8;</font></div><div class="gmail_default" style><font face="courier new, monospace">nlo = 8;</font></div>
<div class="gmail_default" style><font face="courier new, monospace">wi = 0.05;</font></div><div class="gmail_default" style><font face="courier new, monospace">li = 0.05;</font></div><div class="gmail_default" style><font face="courier new, monospace">wf = 0.005;</font></div>
<div class="gmail_default" style><font face="courier new, monospace">lc1 = 0.025;</font></div><div class="gmail_default" style><font face="courier new, monospace">lc2 = 0.01;</font></div><div class="gmail_default" style>
<font face="courier new, monospace"><br>
</font></div><div class="gmail_default" style><font face="courier new, monospace">// Outer perimeter</font></div><div class="gmail_default" style><font face="courier new, monospace">Point(1) = {0.0, wo/2, -lo/2};</font></div>
<div class="gmail_default" style><font face="courier new, monospace">Point(2) = {0.0, wo/2, lo/2};</font></div><div class="gmail_default" style><font face="courier new, monospace">Point(3) = {0.0,-wo/2, lo/2};</font></div>
<div class="gmail_default" style><font face="courier new, monospace">Point(4) = {0.0,-wo/2, -lo/2};</font></div><div class="gmail_default" style><font face="courier new, monospace">Line(101) = {1, 2};</font></div><div class="gmail_default" style>
<font face="courier new, monospace">Line(102) = {2, 3};</font></div><div class="gmail_default" style><font face="courier new, monospace">Line(103) = {3, 4};</font></div><div class="gmail_default" style><font face="courier new, monospace">Line(104) = {4, 1};</font></div>
<div class="gmail_default" style><font face="courier new, monospace">Line Loop(201) = {101, 102, 103, 104};</font></div><div class="gmail_default" style><font face="courier new, monospace"><br></font></div><div class="gmail_default" style>
<font face="courier new, monospace">// Inner perimeter</font></div><div class="gmail_default" style><font face="courier new, monospace">Point(5) = {0.0, wi/2, -li/2, lc2};</font></div><div class="gmail_default" style><font face="courier new, monospace">Point(6) = {0.0, wi/2, li/2, lc2};</font></div>
<div class="gmail_default" style><font face="courier new, monospace">Point(7) = {0.0,-wi/2, li/2, lc2};</font></div><div class="gmail_default" style><font face="courier new, monospace">Point(8) = {0.0,-wi/2, -li/2, lc2};</font></div>
<div class="gmail_default" style><font face="courier new, monospace">Point(9) = {0.0,-wf/2, -li/2, lc2};</font></div><div class="gmail_default" style><font face="courier new, monospace">Point(10) = {0.0, wf/2, -li/2,lc2};</font></div>
<div class="gmail_default" style><font face="courier new, monospace">Line(105) = {5, 6};</font></div><div class="gmail_default" style><font face="courier new, monospace">Line(106) = {6, 7};</font></div><div class="gmail_default" style>
<font face="courier new, monospace">Line(107) = {7, 8};</font></div><div class="gmail_default" style><font face="courier new, monospace">Line(108) = {8, 9};</font></div><div class="gmail_default" style><font face="courier new, monospace">Line(109) = {9, 10};</font></div>
<div class="gmail_default" style><font face="courier new, monospace">Line(110) = {10, 5};</font></div><div class="gmail_default" style><font face="courier new, monospace">Line Loop(202) = {105, 106, 107, 108, 109, 110};</font></div>
<div class="gmail_default" style><font face="courier new, monospace"><br></font></div><div class="gmail_default" style><font face="courier new, monospace">// Make the surfaces</font></div><div class="gmail_default" style>
<font face="courier new, monospace">Plane Surface(301) = {201, 202};</font></div><div class="gmail_default" style><font face="courier new, monospace">Physical Surface("Outer") = {301};</font></div><div class="gmail_default" style>
<font face="courier new, monospace">Plane Surface(302) = {202};</font></div><div class="gmail_default" style><font face="courier new, monospace">Physical Surface("Inner") = {302};</font></div><div class="gmail_default" style>
<font face="courier new, monospace"><br></font></div><div class="gmail_default" style><font face="courier new, monospace">// Uncomment to recombine to quads</font></div><div class="gmail_default" style><font face="courier new, monospace">//Recombine Surface "*";</font></div>
<div style="font-family:verdana,sans-serif">//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~</div><div style="font-family:verdana,sans-serif"><br></div><div style="font-family:verdana,sans-serif">I need exactly 1 edge of a quad on the line from point 9 - 10.</div>
<div style="font-family:verdana,sans-serif"><br></div><div style="font-family:verdana,sans-serif">Excuse the length of this post. I'd appreciate any help.</div><div style="font-family:verdana,sans-serif"><br></div><div style="font-family:verdana,sans-serif">
- Dave</div></div></div>