<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi Tabrez,<div><br></div><div>Actually, aspect ratios of 50+ sound pretty high to me, although that may not be your problem. The other question is what sort of Maxwell times you have compared to your time step size. Are you using automatic or fixed time stepping?</div><div><br></div><div>Charles</div><div><br></div><div><br><div><div>On Dec 11, 2008, at 5:49 AM, Tabrez Ali wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div>Brad/Charles<br><br>Thanks for your reply. Yes the residuals do increase after each time <br>step. I have a low dipping fault which curves from very shallow dip to <br>somewhat steeper dip (as in shallow subduction).<br><br>If I specify slip on the steeper part then things work fine. Things also <br>work fine when I dont specify slip on this particular fault but have <br>other faults/BC's in place (on the same mesh).<br><br>Its slip on the shallow part which seems to mess it up.<br><br>Also my mesh quality isnt that bad. I do have a few elements with aspect <br>ratios of 50+ (in cubit) but nothing greater than 100. And my material <br>property for the fault is the same as used in the examples/benchmarks.<br><br>Regards<br>Tabrez<br><br>Brad Aagaard wrote:<br><blockquote type="cite">Tabrez-<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">Does the solution blow up (residual increases) or just fail to converge <br></blockquote><blockquote type="cite">(residual approaches some value)? If the solution blows up, something is <br></blockquote><blockquote type="cite">wrong. Either the problem is not setup correctly or there is a bug.<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">There are a number of things that can cause the solution to converge very <br></blockquote><blockquote type="cite">slowly. In addition to the mesh quality issue that Charles pointed out, some <br></blockquote><blockquote type="cite">other things you might look into include:<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">(1) Do you get the same behavior with a coarser mesh?<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">(2) Does the solution converge when you omit the fault in the parameters <br></blockquote><blockquote type="cite">(i.e., use the same mesh but don't have any fault interface conditions)? If <br></blockquote><blockquote type="cite">you have zero displacement BC, try simple compression without a fault.<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">(3) What is Poisson's ratio? Do any cells have a Poisson ratio greater than <br></blockquote><blockquote type="cite">0.45 (only values greater than about 0.48 should cause problems)?<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">(4) What physical properties are you using for the fault (this affects the <br></blockquote><blockquote type="cite">conditioning of the system and can affect convergence if they are not <br></blockquote><blockquote type="cite">reasonable)? In a test problem, the solution converged slightly faster for <br></blockquote><blockquote type="cite">uniform physical properties for the fault (only used to condition the system) <br></blockquote><blockquote type="cite">compared with the actual 3-D variation.<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">Brad<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">On Wednesday 10 December 2008 12:05:31 am Charles Williams wrote:<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite"><blockquote type="cite">I would look at the element quality in the mesh. You can do this in<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">ParaView. The low angles may be giving you poorly-formed elements,<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">and this could cause problems. I doubt that incorrect fault<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">parameters is causing the problem, unless you're doing something<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">that's giving you very large strains.<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">Charles<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">On Dec 10, 2008, at 6:43 PM, Tabrez Ali wrote:<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">Brad/PyLith Users<br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">It seems that whenever I use a low angle thrust fault (very low dip)<br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">the<br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">solution (to the quasi-static problem) after a certain number of time<br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">steps fails to converge and blows up. Can wrong fault parameters<br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">such as<br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">up_dir or normal_dir also cause this?<br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">Regards<br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">Tabrez<br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">_______________________________________________<br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">CIG-SHORT mailing list<br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><a href="mailto:CIG-SHORT@geodynamics.org">CIG-SHORT@geodynamics.org</a><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><a href="http://geodynamics.org/cgi-bin/mailman/listinfo/cig-short">http://geodynamics.org/cgi-bin/mailman/listinfo/cig-short</a><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">Charles A. Williams<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">Scientist<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">GNS Science<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">1 Fairway Drive, Avalon<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">PO Box 30368<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">Lower Hutt 5040<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">New Zealand<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">ph (office): 0064-4570-4566<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">fax (office): 0064-4570-4600<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><a href="mailto:C.Williams@gns.cri.nz">C.Williams@gns.cri.nz</a><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">NOTE NEW E-MAIL ADDRESS<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite"><br></blockquote><br>_______________________________________________<br>CIG-SHORT mailing list<br><a href="mailto:CIG-SHORT@geodynamics.org">CIG-SHORT@geodynamics.org</a><br>http://geodynamics.org/cgi-bin/mailman/listinfo/cig-short<br></div></blockquote></div><br><div> <span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font face="Helvetica" size="3" style="font: normal normal normal 12px/normal Helvetica; ">Charles A. Williams</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Scientist<br>GNS Science<br>1 Fairway Drive, Avalon<br>PO Box 30368<br>Lower Hutt 5040<br>New Zealand<br>ph (office): 0064-4570-4566<br>fax (office): 0064-4570-4600</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a href="mailto:C.Williams@gns.cri.nz">C.Williams@gns.cri.nz</a></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">NOTE NEW E-MAIL ADDRESS</div></div></div></span> </div><br></div>
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