On 05/09/2013 02:22 PM, PETER ZAJAC wrote: > David, > > I was worried about the volume element for integration. If I use explicit > transformations of coordinates to spherical how would I make sure that the > volume element for integration changes accordingly.
Cartesian -> spherical is just a change of coordinates, so if you take that into account properly in the weak form then everything is fine. In particular, you need to account for: - the change of measure, which gives an extra r^2 * \sin(\phi) factor, if memory serves - the change of variables in the gradient terms It would be nice to automate this so that it is automatically included in libMesh's JxW and dphi, which is what Paul was referring to. But the easiest thing for you in the short term would be to just explicitly deal with the change of variables yourself. David On May 9, 2013, at 10:57, "Paul T. Bauman" <[email protected]> wrote: >> What David said is correct (and how I currently deal with cylindrical >> coordinates). Nevertheless, while there are no formal plans, I've thought >> it would be nice to try and deal with alternative (to Cartesian) coordinate >> systems at the libMesh level. E.g. JxW comes premultiplied by r, >> curl/Laplacian/div/etc formulae have the right terms so that the same code >> could be used regardless of coordinate system, etc. Alas, it hasn't been >> high enough priority for me to spend any time thinking about it and >> proposing how to do it, e.g. whether it should be an FE type, etc. >> >> That said, Peter, if you wanted to take a crack at it, I (and probably >> others) would be happy to give guidance. >> >> >> On Thu, May 9, 2013 at 12:48 PM, David Knezevic >> <[email protected]>wrote: >> >>> I'm not sure I understand what you're getting at, but if you write the >>> PDE in terms of (r,theta,phi), then you can just use libmesh in the >>> standard way. You'll presumably get sin's, cos's and 1/r terms in the >>> weak form, but that's no problem... >>> >>> >>> >>> On 05/09/2013 01:43 PM, Peter Zajac wrote: >>>> Dear All, >>>> >>>> Is treatment in spherical coordinates an option in Libmesh? >>>> If not is there a plan to implement it in the near future? >>>> >>>> Thank you in advance >>>> >>>> >>>> PZ >>>> >>> ------------------------------------------------------------------------------ >>>> Learn Graph Databases - Download FREE O'Reilly Book >>>> "Graph Databases" is the definitive new guide to graph databases and >>>> their applications. This 200-page book is written by three acclaimed >>>> leaders in the field. The early access version is available now. >>>> Download your free book today! http://p.sf.net/sfu/neotech_d2d_may >>>> _______________________________________________ >>>> Libmesh-users mailing list >>>> [email protected] >>>> https://lists.sourceforge.net/lists/listinfo/libmesh-users >>> >>> >>> ------------------------------------------------------------------------------ >>> Learn Graph Databases - Download FREE O'Reilly Book >>> "Graph Databases" is the definitive new guide to graph databases and >>> their applications. This 200-page book is written by three acclaimed >>> leaders in the field. The early access version is available now. >>> Download your free book today! http://p.sf.net/sfu/neotech_d2d_may >>> _______________________________________________ >>> Libmesh-users mailing list >>> [email protected] >>> https://lists.sourceforge.net/lists/listinfo/libmesh-users >>> >> ------------------------------------------------------------------------------ >> Learn Graph Databases - Download FREE O'Reilly Book >> "Graph Databases" is the definitive new guide to graph databases and >> their applications. This 200-page book is written by three acclaimed >> leaders in the field. The early access version is available now. >> Download your free book today! http://p.sf.net/sfu/neotech_d2d_may >> _______________________________________________ >> Libmesh-users mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/libmesh-users ------------------------------------------------------------------------------ Learn Graph Databases - Download FREE O'Reilly Book "Graph Databases" is the definitive new guide to graph databases and their applications. This 200-page book is written by three acclaimed leaders in the field. The early access version is available now. Download your free book today! http://p.sf.net/sfu/neotech_d2d_may _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
