From: Wolfgang Bangerth <bangerth@math.tamu.edu>
Date: Fri, 30 Aug 2013 22:14:13 +0000 (+0000)
Subject: Patch by Denis Davydov: Document what exactly the gradient of a vector is.
X-Git-Tag: v8.1.0~920
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=92cb714805726f380ccb2b5aaf2c319872d40439;p=dealii.git

Patch by Denis Davydov: Document what exactly the gradient of a vector is.

git-svn-id: https://svn.dealii.org/trunk@30540 0785d39b-7218-0410-832d-ea1e28bc413d
---

diff --git a/deal.II/include/deal.II/fe/fe_values.h b/deal.II/include/deal.II/fe/fe_values.h
index 1b0164b656..4963d54c30 100644
--- a/deal.II/include/deal.II/fe/fe_values.h
+++ b/deal.II/include/deal.II/fe/fe_values.h
@@ -440,6 +440,17 @@ namespace FEValuesViews
    * this class should not be used for this
    * context.
    *
+   * This class allows to query the
+   * value, gradient and divergence of
+   * (components of) shape functions
+   * and solutions representing
+   * vectors. The
+   * gradient of a vector
+   * $d_{k}, 0\le k<\text{dim}$ is
+   * defined as
+   * $S_{ij} = \frac{\partial d_{i}}{\partial x_j},
+   * 0\le i,j<\text{dim}$.
+   *
    * You get an object of this type if you
    * apply a FEValuesExtractors::Vector to an
    * FEValues, FEFaceValues or
@@ -467,6 +478,9 @@ namespace FEValuesViews
      * <code>dim</code> components of the
      * finite element, the gradient is a
      * <code>Tensor@<2,spacedim@></code>.
+     *
+     * See the general documentation of this class for how exactly
+     * the gradient of a vector is defined.
      */
     typedef dealii::Tensor<2,spacedim>          gradient_type;
 
@@ -647,6 +661,9 @@ namespace FEValuesViews
      * function and quadrature point
      * selected by the arguments.
      *
+     * See the general documentation of this class for how exactly
+     * the gradient of a vector is defined.
+     *
      * @note The meaning of the arguments
      * is as documented for the value()
      * function.