Re: [Libmesh-users] 1D/2D elements in 3D space
On Mon, 12 Feb 2018, Manav Bhatia wrote: So, would the shape function derivatives account the orientation of the element? For instance, a 1D element oriented along: x-axis vs y-axis vs x=y line. In all cases, there is only one shape function defined along the element coordinate. But its derivative wrt x and y will vary. Is this handled for both 1st order and 2nd order Lagrange (for instance)? IIRC it's handled properly for all scalar-valued elements, where by "properly" I mean that the derivative is returned as a directional gradient in LIBMESH_DIM-dimensional space. E.g. If you have an EDGE2 element with a value of 1 at the origin and 0 at the other end, then if the other end is at (x,y,z) the gradient in physical space we return should be (-x, -y, -z). That means that if you're solving e.g. a Laplacian problem, then you want to be integrating grad(u)*grad(v) as a dot product of 2 vectors, not just assuming that you can still ignore the m>>n indexed components for an n-dimensional element. I'm actually not sure if anybody ever made sure we support embedded vector-valued elements. Cc'ing Paul Bauman; if he didn't do it then nobody did. --- Roy -- Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot ___ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
Re: [Libmesh-users] 1D/2D elements in 3D space
Thanks! So, would the shape function derivatives account the orientation of the element? For instance, a 1D element oriented along: x-axis vs y-axis vs x=y line. In all cases, there is only one shape function defined along the element coordinate. But its derivative wrt x and y will vary. Is this handled for both 1st order and 2nd order Lagrange (for instance)? -Manav > On Feb 12, 2018, at 5:06 PM, Roy Stogner wrote: > > > On Mon, 12 Feb 2018, Manav Bhatia wrote: > >> I was looking through some code in FE and noticed some comments >> about 1D/2D elements in 3D space. What is the extent of support >> for this? > > IIRC: > > If you're using just one or just the other, then the support should be > complete. > > If you're connecting one to the other (or connecting either/both to 3D > elements), then you don't get neighbor links for those connections. > > If you're overlapping one on or within the other (e.g. elements which > occupy the sides of higher dimensional elements) and you want them to > share DoFs consistently then I think you're limited to LAGRANGE > variables for those DoFs. > --- > Roy -- Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot ___ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
Re: [Libmesh-users] 1D/2D elements in 3D space
On Mon, 12 Feb 2018, Manav Bhatia wrote: I was looking through some code in FE and noticed some comments about 1D/2D elements in 3D space. What is the extent of support for this? IIRC: If you're using just one or just the other, then the support should be complete. If you're connecting one to the other (or connecting either/both to 3D elements), then you don't get neighbor links for those connections. If you're overlapping one on or within the other (e.g. elements which occupy the sides of higher dimensional elements) and you want them to share DoFs consistently then I think you're limited to LAGRANGE variables for those DoFs. --- Roy -- Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot ___ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users