> To be honest, I don't even see the point of having 9 integration points for > a 4-noded quadrilateral or am I overseeing something?
Yes, you are missing some background information: Quadrature formulas are exact for polynomials up to a certain degree. For Gauss quadrature you need degree n to integrate polynomials of degree 2n-1 exactly: https://urldefense.proofpoint.com/v2/url?u=https-3A__en.wikipedia.org_wiki_Gaussian-5Fquadrature-23Fundamental-5Ftheorem&d=DwIBaQ&c=Ngd-ta5yRYsqeUsEDgxhcqsYYY1Xs5ogLxWPA_2Wlc4&r=4k7iKXbjGC8LfYxVJJXiaYVu6FRWmEjX38S7JmlS9Vw&m=PDOwphRntO6TO2o4Lgd_VolY1Tdk0-uWL7LHVKKC9yY&s=GP1u_R42mj2e2VpImgPCnEHpalb6rChFLMnloN6wb_Q&e= The integrals in the weak form involve products of shape functions of a certain degree, so the quadrature should be of high enough degree to integrate them with a small or no error. Maybe you can take a look at https://urldefense.proofpoint.com/v2/url?u=http-3A__www.math.colostate.edu_-7Ebangerth_videos.676.33.5.html&d=DwIBaQ&c=Ngd-ta5yRYsqeUsEDgxhcqsYYY1Xs5ogLxWPA_2Wlc4&r=4k7iKXbjGC8LfYxVJJXiaYVu6FRWmEjX38S7JmlS9Vw&m=PDOwphRntO6TO2o4Lgd_VolY1Tdk0-uWL7LHVKKC9yY&s=FGaRjjjHuJ-ybWRwN7eJRYI_p9YKmCjsIaS5mR2d458&e= or your favorite FEM book. -- Timo Heister http://www.math.clemson.edu/~heister/ -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
