From: bangerth Date: Sat, 28 Oct 2006 00:23:35 +0000 (+0000) Subject: Comment on the project_back_saturation X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=616c1428df7151ef52ef1c4bb5bc29f11502ddc9;p=dealii-svn.git Comment on the project_back_saturation git-svn-id: https://svn.dealii.org/trunk@14110 0785d39b-7218-0410-832d-ea1e28bc413d --- diff --git a/deal.II/examples/step-21/doc/intro.dox b/deal.II/examples/step-21/doc/intro.dox index c8fb3af26a..74167d099a 100644 --- a/deal.II/examples/step-21/doc/intro.dox +++ b/deal.II/examples/step-21/doc/intro.dox @@ -359,7 +359,13 @@ easily be verified. (Remember that the saturation corresponds to something like the water fraction in the fluid mixture, and therefore must physically be between 0 and 1.) On the other hand, if we choose our time step according to the criterion listed above, this only happens very very infrequently — -in fact only once for the entire run of the program. +in fact only once for the entire run of the program. However, to be on the +safe side, however, we run a function project_back_saturation at +the end of each time step, that simply projects the saturation back onto the +interval $[0,1]$, should it have gotten out of the physical range. This is +useful since the functions $\lambda(S)$ and $F(S)$ do not represent anything +physical outside this range, and we should not expect the program to do +anything useful once we have negative saturations or ones larger than one. Note that we will have similar restrictions on the time step also in @ref step_23 "step-23" and @ref step_24 "step-24" where we solve the time dependent