From: Mark Blome <mblome@au...>  20050329 13:47:18

Hi Rolf, > > > > So it seems that  away from the singularity  the accuracy > > of the solution is pretty good, but it deteriorates at the > > node which is shared with the infinite element (at x=3D1).  Is > > that a necessity, BTW? > I noticed the same in my calculations. It seems like the solution becomes=20 inaccurate close to the nodes that are shared with the infinite elements bu= t=20 =2D astonishingly becomes accurate again at some distance to these nodes. = I=20 tried different settings for the infinite elements radial order (and=20 different polynomials), but that doesnt improve things. Also I tried, as=20 Steffen suggested, a spherical mesh (please see the two pictures attached,= =20 they show scalar cut planes through 3D calculations, the border of the mesh= =20 is where the distortions occur, in this case there are no infinite elements= =20 attached at the upper surface ), but the problem remains.=20 I'll let you know if I find out more about whats going wrong, Mark Am Dienstag, 29. M=E4rz 2005 12.02 schrieb Steffen Petersen: > > OK, what an irony: I had chosen laspack, because I had  > > wrongly  assumed that it would be the least errorprone. Now > > I am using PETSc (configuration "enablepetsc > > enablecomplex enablempi") and I think it works: The > > spherical symmetry of the solution looks very good in general > > and was perfect where I tested it (along the xaxis). > > > > Here are some example results for the real part of the > > solution along the xaxis: > > > > x ex6 cos(x)/(4*pi*x) > > 0 6.5665 Inf > > 0.0667 0.6505 1.1910 > > 0.1333 0.6000 0.5915 > > 0.2000 0.3743 0.3900 > > 0.2667 0.2840 0.2879 > > 0.3333 0.2231 0.2256 > > 0.4000 0.1818 0.1832 > > 0.4667 0.1514 0.1523 > > 0.5333 0.1278 0.1285 > > 0.6000 0.1090 0.1095 > > 0.6667 0.0934 0.0938 > > 0.7333 0.0803 0.0806 > > 0.8000 0.0691 0.0693 > > 0.8667 0.0592 0.0594 > > 0.9333 0.0506 0.0507 > > 1.0000 0.0214 0.0430 > > > > So it seems that  away from the singularity  the accuracy > > of the solution is pretty good, but it deteriorates at the > > node which is shared with the infinite element (at x=3D1).  Is > > that a necessity, BTW? > > The main reason for these inaccuracies is probably the > box shaped infinite element interface (envelope). > A spherical envelope should lead to more accurate results. > Note that you can also increase the radial order of the > infinite elements to increase the accuracy of your computations. > Regarding example 6, this can be done changing line 163 > FEType fe_type(FIRST); to FEType fe_type(FIRST, LAGRANGE, > requested_ifem_order); > The default radial order is THIRD. The infinite elements are > implemented up to order EIGHTTEENTH, which is perhaps > solely of academic use. > > Steffen > > > >  > SF email is sponsored by  The IT Product Guide > Read honest & candid reviews on hundreds of IT Products from real users. > Discover which products truly live up to the hype. Start reading now. > http://ads.osdn.com/?ad_id=3D6595&alloc_id=3D14396&op=3Dclick > _______________________________________________ > Libmeshusers mailing list > Libmeshusers@... > https://lists.sourceforge.net/lists/listinfo/libmeshusers 