From b9e89e3bb07381dbb880532b809c3ff4da59685f Mon Sep 17 00:00:00 2001 From: Wolfgang Bangerth Date: Sat, 23 Apr 2011 03:38:27 +0000 Subject: [PATCH] Document what to do with setting the fe index. git-svn-id: https://svn.dealii.org/trunk@23637 0785d39b-7218-0410-832d-ea1e28bc413d --- deal.II/examples/step-46/doc/intro.dox | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/deal.II/examples/step-46/doc/intro.dox b/deal.II/examples/step-46/doc/intro.dox index d971fc7fcf..33688de8ff 100644 --- a/deal.II/examples/step-46/doc/intro.dox +++ b/deal.II/examples/step-46/doc/intro.dox @@ -444,6 +444,32 @@ boundary conditions and geometry are defined nearly analogously to the 2d situation above. +

Identifying which subdomain a cell is in

+ +In the program, we need a way to identify which part of the domain a cell is +in. There are many different ways of doing this. A typical way would be to use +the @ref GlossSubdomainId "subdomain_id" tag available with each cell, though +this field has a special meaning in %parallel computations. An alternative +is the @ref GlossMaterialId "material_id" field also available with +every cell. It has the additional advantage that it is inherited from the +mother to the child cell upon mesh refinement; in other words, we would set +the material id once upon creating the mesh and it will be correct for all +active cells even after several refinement cycles. We therefore go with this +alternative: we define an enum with symbolic names for +material_id numbers and will use them to identify which part of the domain a +cell is on. + +Secondly, we use an object of type hp::DoFHandler. This class needs to know +which cells will use the Stokes and which the elasticity finite element. At +the beginning of each refinement cycle we will therefore have to walk over +all cells and set the (in hp parlance) active FE index to whatever is +appropriate in the current situation. While we can use symbolic names for the +material id, the active FE index is in fact a number that will frequently be +used to index into collections of objects (e.g. of type hp::FECollection and +hp::QCollection); that means that the active FE index actually has to have +value zero for the fluid and one for the elastic part of the domain. + +

Linear solvers

This program is primarily intended to show how to deal with different -- 2.39.5