man 2D_D (3): -div 2D operator

SYNOPSIS

form (const space V, const space& V, "2D_D");

Assembly the form associated to the div(2D(.)) components of the operator on the finite element space V:

                 /
                 |
        a(u,v) = |  2 D(u) : D(v) dx
                 |
                 / Omega

where

                1 ( d ui   d uj )
      Dij(u) =  - ( ---- + ---- )
                2 ( d xj   d xi )

This form is usefull when considering elasticity or Stokes problems.

Here is an example of the vector-valued form:

        geo omega ("square");
        space V (omega, "P2", "vector");
        form  a (V, V, "2D_D");

Note that a factor two is here applied to the form. This factor is commonly used in practice.