[cig-commits] r21630 - seismo/2D/SPECFEM2D/trunk/src/specfem2D

[dkomati1 at geodynamics.org]

Author: dkomati1
Date: 2013-03-25 14:17:11 -0700 (Mon, 25 Mar 2013)
New Revision: 21630

Modified:
   seismo/2D/SPECFEM2D/trunk/src/specfem2D/compute_forces_acoustic.f90
Log:
added a comment about the boundary condition to use on outer edges of PML elements in acoustic (fluid) layers


Modified: seismo/2D/SPECFEM2D/trunk/src/specfem2D/compute_forces_acoustic.f90
===================================================================
--- seismo/2D/SPECFEM2D/trunk/src/specfem2D/compute_forces_acoustic.f90	2013-03-25 21:03:42 UTC (rev 21629)
+++ seismo/2D/SPECFEM2D/trunk/src/specfem2D/compute_forces_acoustic.f90	2013-03-25 21:17:11 UTC (rev 21630)
@@ -731,6 +731,15 @@
 !
 !--- absorbing boundaries
 !
+
+! The outer boundary condition to use for PML elements in fluid layers is Neumann for the potential
+! because we need Dirichlet conditions for the displacement vector, which means Neumann for the potential.
+! Thus, there is nothing to enforce explicitly here.
+! There is something to enforce explicitly only in the case of elastic elements, for which a Dirichlet
+! condition is needed for the displacement vector, which is the vectorial unknown for these elements.
+
+! for Stacey paraxial absorbing conditions (more precisely: Sommerfeld in the case of a fluid) we implement them here
+
   if(.not. PML_BOUNDARY_CONDITIONS .and. anyabs) then
 
     do ispecabs=1,nelemabs