On Tue, 14 May 2013, Manav Bhatia wrote: > This is the Gaussian bump problem from the higher-order CFD workshop ( > http://dept.ku.edu/~cfdku/hiocfd/case_c1.1.html). You are correct that away > from the bump the boundary is straight, so linear elements should be fine. > I am looking at the entropy error, since the entropy is supposed to stay > constant. The bump-boundary, infact, is adding to the entropy-error. I am > able to drop down to 10^-7 in the error L2 norm, and then it stagnates. And > I have a feeling that this is due to the low-order geometry.
Hmm... the low-order geometry should definitely be hurting your convergence rate here, but it shouldn't be giving you a rate of *zero*. Usually when you start to converge but then stagnate it means you're hitting some previously-negligible epsilon. I've never seen anything but a penalty BC parameter cause stagnation at a *relative* error as high as 1e-7 though. Usually the second limitation I run into is insufficiently tight solver tolerances, and the third is FP roundoff error. From our point of view I don't want to discourage you from the QUAD16 idea, but I don't think it's likely to be the cause of your problem, and it would probably be easy for you to check your solver parameters or to recompile with quad precision before going to the effort of adding a new geometric element to libMesh. --- Roy ------------------------------------------------------------------------------ AlienVault Unified Security Management (USM) platform delivers complete security visibility with the essential security capabilities. Easily and efficiently configure, manage, and operate all of your security controls from a single console and one unified framework. Download a free trial. http://p.sf.net/sfu/alienvault_d2d _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
