Dear Dr. Bangerth, Thank you very much! I was confused about the shape function in the vector case. In step.8 we use the FEValue::shape_grad(index of shape function,index of quadrature point) and get a vector as the gradient of shape function. However, in step.20 and step.22, when we take the gradient of FESystem[vector_indices]::gradient(index of shape function, index of quadrature point) we get a rank-2 tensor. If the shape function is a vector, FEValue::shape_grad(index of shape function,index of quadrature point) should give a tensor as well. Does it mean that the shape_grad gives the gradient of the non-zero component in the vector shape function such that it is a vector? Thank you again! Best regards,
On Thu, Sep 3, 2020 at 3:11 PM Wolfgang Bangerth <[email protected]> wrote: > On 9/3/20 1:28 PM, yuesu jin wrote: > > I am working on vector value finite element modeling. I read the > pages > > > https://www.dealii.org/current/doxygen/deal.II/group__vector__valued.html > > < > https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.dealii.org%2Fcurrent%2Fdoxygen%2Fdeal.II%2Fgroup__vector__valued.html&data=02%7C01%7CWolfgang.Bangerth%40colostate.edu%7Cb30f39009c8c49c8fc8108d8503f8631%7Cafb58802ff7a4bb1ab21367ff2ecfc8b%7C0%7C0%7C637347581059635256&sdata=w%2BABjRZ1fzUdFfCQvw49JwLF7Inl3iEG4XR78VwlgoA%3D&reserved=0> > which > > > uses the fe_values.divergence and fe_value.grad, but I cannot find these > two > > member functions in the FEValues\FESystem\FEValueBase categories. Could > you > > give me the documentation page about these two functions? > > These functions only exist in FEValuesViews::Vector and > FEValuesViews::Tensor. > You get that if you have something like > > FEValuesExtractors::Vector velocities(0); > fe_values[velocities].divergence (...); > > step-22 shows how this works in practice. > > Best > W. > > -- > ------------------------------------------------------------------------ > Wolfgang Bangerth email: [email protected] > www: http://www.math.colostate.edu/~bangerth/ > > -- > 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 [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/dealii/79b2e60e-86e5-b310-9b28-c5c96c3eb364%40colostate.edu > . > -- Yuesu Jin, Ph.D student, University of Houston, College of Natural Sciences and Mathematics, Department of Earth and Atmospheric Sciences, Houston, Texas 77204-5008 346-404-2062 -- 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 [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/CA%2B25a%3DK1nXsvYa0EZvL6eMrduqxx_rZHiSTHUFc-Gxr4KaJBzA%40mail.gmail.com.
