From: Wolfgang Bangerth Date: Mon, 1 Jul 2024 23:10:14 +0000 (-0600) Subject: Leave a note about DAEs. X-Git-Tag: v9.6.0-rc1~78^2~3 X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e8bdc3a7a54e44181323f9d210af852be5cd3ae6;p=dealii.git Leave a note about DAEs. --- diff --git a/examples/step-86/doc/intro.dox b/examples/step-86/doc/intro.dox index 7fe39d2cd5..b505a96fda 100644 --- a/examples/step-86/doc/intro.dox +++ b/examples/step-86/doc/intro.dox @@ -272,6 +272,15 @@ provide the ability to take a solution vector and set its constrained (algebraic) entries to their correct values; for us, that will mean setting boundary values and hanging node constraints correctly. +(We note that when dealing with Differential-Algebraic Equations (DAEs), +the algebraic components identified by the first callback mentioned +above contain hanging nodes, Dirichlet boundary nodes, *and degrees +of freedom for which the equation does not provide time derivatives*. +This is not of concern to us here, and so we will not dwell on +the issue -- or the fact that the second callback in the case of DAEs +should set only a subset of the algebraic components -- and instead +refer to the examples shown in the SUNDIALS::IDA class documentation.) +

Complication 2: Mesh refinement