OK cracked it, thanks for the pointer to the example in the Wiki Lars,<br>As a resault of this I have a simple exmpale whihc may be appropriate for the Wiki.<br>It is a steady state lapace equation on a cube with natural Neumann conditons on bottom and on two sides, inhomegeneous Neumann on the two remaining sides and a Robin type condtion on the top.<br>
<br><br>I have some hints for other beginners like me,<br><br>1. in Fomulation:<br>Dof{u} is equivalent to test function, {u} is equivalent to trial function.<br>
<br>2.<br>the "Support" of the BasisFunction should be the whole domain, including boundaries, its obvious really but it took me long time to work it out.<br>I originally had the support based on a Physical Volume from the .geo file but getdp gave zero solution. When I added the bounding surfaces of the volume to the "Support" getdp worked. <br>
<br>3.<br>To define a neumann condition in the formulation use something like<br> Galerkin { [ f_neumann_left[] , {phi} ] ; In left ; Jacobian Sur ; Integration Int ; }<br><br>and for a Robin type condition use<br>
Galerkin { [ f_robin_top[]*Dof{phi} , {phi} ] ; In top ; Jacobian Sur ; Integration Int ; }<br><br>f_neumann_left[] and f_robin_top[] may be as simple as a constant.<br><br>Note that there was a typo in the previous post for the robin BC.<br>
<br><br><br><div class="gmail_quote">On Fri, Oct 16, 2009 at 8:25 AM, Thomas Ward <span dir="ltr"><<a href="mailto:tomwardathome@googlemail.com" target="_blank">tomwardathome@googlemail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
many thanks Lars, <br>yes it is normal to the boundary<br>your example helped a lot, especially since you had shown the problem equation alongside the getdp code, it helped me to decipher the getdp syntax.<br><br>so I think I need<br>
<br><br>Formulation {<br> { Name f1 ; Type FemEquation ;<br> Quantity { <br> { Name phi ; Type Local ; NameOfSpace fs1 ; }<br> }<br> Equation {<br> Galerkin { [ Dof{d phi} , {d phi} ] ; In Omega ; Jacobian Vol ; Integration Int ; }<br>
Galerkin { [ k*Dof{d phi} , {phi} ] ; In Top ; Jacobian Vol ; Integration Int ; }<br> }<br> }<br>}<br><br>regards<br><br>Tom<div><div></div><div><br><br><br><div class="gmail_quote">On Fri, Oct 16, 2009 at 7:27 AM, Lars Rindorf <span dir="ltr"><<a href="mailto:Lars.Rindorf@teknologisk.dk" target="_blank">Lars.Rindorf@teknologisk.dk</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
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<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);">Hi Tom</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);" lang="EN-US">Is the spatial derivative normal or perpendicular to the 3D cube
boundary? If it is perpendicular, you can see the scatpar example. That is
similar.</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);" lang="EN-US"> </span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);" lang="EN-US">Kr, Lars</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);" lang="EN-US"> </span></p>
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<p class="MsoNormal"><b><span style="font-size: 10pt;">Fra:</span></b><span style="font-size: 10pt;">
<a href="mailto:getdp-bounces@ace20.montefiore.ulg.ac.be" target="_blank">getdp-bounces@ace20.montefiore.ulg.ac.be</a>
[mailto:<a href="mailto:getdp-bounces@ace20.montefiore.ulg.ac.be" target="_blank">getdp-bounces@ace20.montefiore.ulg.ac.be</a>] <b>På vegne af </b>Thomas
Ward<br>
<b>Sendt:</b> 16. oktober 2009 08:20<br>
<b>Til:</b> <a href="mailto:getdp@geuz.org" target="_blank">getdp@geuz.org</a><br>
<b>Emne:</b> Re: [Getdp] How to define Robin boundary conditions</span></p>
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<p class="MsoNormal" style="margin-bottom: 12pt;">oops that should have read
".... thanks to Christophe ..... "!<br>
<br>
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<p class="MsoNormal">On Thu, Oct 15, 2009 at 5:01 PM, Thomas Ward <<a href="mailto:tomwardathome@googlemail.com" target="_blank">tomwardathome@googlemail.com</a>>
wrote:</p>
<p class="MsoNormal" style="margin-bottom: 12pt;"><br>
Probably a simple question but I can't find the answer in the examples of the
wiki or searching the list.<br>
<br>
I am trying to define a Robin type boundary condition for the Laplace equation
on a cube<br>
<br>
dphi/dz+constant*phi=0 on one face<br>
<br>
I think the weak form of this is<br>
integral_over_face(test_function * trial_function*constant) =0<br>
<br>
can someone point me to an example of how to write this in the .pro file? <br>
thanks<br>
<br>
and thanks to Christian for his public spiritedness over many years by the look
of the archives.<br>
<br>
Tom Ward<br>
<br>
<br>
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