> > > > > 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. > > Oh yeah, I have heard of this spurious entropy production problem on > curved geometries. > > Are you really using Quad8's? Can you use Quad9's with the hierarchics? > > Can you modify the test problem slightly so the bump is a quadratic > function and verify convergence with higher p's? > >
This is a great suggestion, John. I will try converting the geometry to second order. I have not tried Quad9, but what would that be any better than Quad8? > > Yes, I was considering this, and also the 25-noded quad. However, I am > still > > considering if the effort might be worth it: Meaning that I may be able > to > > get theoretical order of convergence for this simpler benchmark problem, > but > > I don't know if any practical problem will benefit from a 16 or 25 noded > > quad. I am not sure if any mesh generator would give me elements with > these > > many nodes. > > You will probably have trouble viewing the solutions in Paraview too... > As it is, I am having trouble viewing results from higher-order elements in Paraview. I can output only the nodal data for viewing in Paraview, and so the higher-order information of the element solution gets lost. I haven't yet had the chance to look into improving this behavior. Roy: Just to clarify, I do get a reduction in error for higher order elemets after 10^-7, but the rate of convergence is considerably lower than the p+1/2 theoretical order. I will try compiling with quad precision to see if that does something. I have played around with the solver parameters, and have also used direct solvers to flush out any potential problems form linear solvers. ------------------------------------------------------------------------------ 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
