On Fri, Jul 8, 2016 at 5:15 PM, Jayaraman, Vegnesh <vjayr...@illinois.edu> wrote:
> Hi > > I am trying to solve 2D poisson equation. > \nabla^2 u = f > > My f has dirac delta source terms. \delta(r-r_i) > > I need the value of phi at a particular global x,y location. > > These are the steps that I am currently following: > > 1) Check if the r_i is in the current element > 2) If r_i is in the current element, I take the phi at 4 quadrature points > and perform a bilinear interpolation to get the phi at r_i. > or > The phi returned by get_phi() are the shape function values at the > reference coordinates. > So I modified 2) to perform bilinear interpolation of JxW*phi at 4 > quadrature points. > > My issue with the above step is JxW also contains the quadrature weights. > So JxW*phi will not give me the exact phi value at the global coordinates > but also contain quadrature weights. > > Is there any way to get phi value in global coordinates.? > I think the easiest way to do this is to use FE::reinit. Have a look at include/fe/fe.h, you'll see that you can pass a vector of points to reinit and then evaluate the shape functions on those points. David ------------------------------------------------------------------------------ Attend Shape: An AT&T Tech Expo July 15-16. Meet us at AT&T Park in San Francisco, CA to explore cutting-edge tech and listen to tech luminaries present their vision of the future. This family event has something for everyone, including kids. Get more information and register today. http://sdm.link/attshape _______________________________________________ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
