[Getdp] 2d DC Conduction

Laird Bolt lbolt1 at irf.com
Thu Mar 2 00:58:41 CET 2006

I have found my error.  A simple typographical error where the "NameOfConstraint" did not match the
name in the Constraint list.  I had checked this, I thought.  This was also the source of the 
"Warning: Null right Hand Side in Linear Equation " message
I have modified my simpleBar.pro file (fixed a couple of other things that I had meant
to reset before sending the file out previously) and have attached it just in case anyone reads this
in the archives and wants to see the resolution.
Sorry for the wasted bandwidth
Laird Bolt
-----Original Message-----
From: getdp-bounces at geuz.org [mailto:getdp-bounces at geuz.org]On Behalf Of Laird Bolt
Sent: Tuesday, February 28, 2006 5:13 PM
To: getdp at geuz.org
Subject: [Getdp] 2d DC Conduction

I apologise in advance  for sending such a newbie question to the list.  In Payment if someone could 
set me on my way I will add my simple example(s) to the main example list. 

In an effort to walk (more of a crawl) before I run I am trying to simply 
calculate the voltage and current density distribution in a flat bar of copper (no temperature effects assumed) 

Fragments for this exist in the mail archives as well as documentation.  However, 
I must be doing something wrong as my results are always zero when using Dirichlet BC at both ends 
and constant (but non-zero) when I use dirichlet at one end and Neumann BC at the other. 

I assume that the null Neumann BC along the long sides is implicit. 

I have attached my .geo, .pro and solver.par files for the Dirichlet BC (1V at one end 0v at the other) 

THe Formulation was : 

Formulation { 
  { Name Voltage_Steady ; Type FemEquation ; 
    Quantity { 
      { Name Volt ; Type Local ; NameOfSpace Vgrad ; } 
    Equation { 
      Galerkin { [ invrho[] *  Dof {d Volt} ,  {d Volt} ] ;  
                 In Bar ; Jacobian JVol ; Integration GradGrad ; } 

When I run the Dirichlet at both ends I receive a Warning: Null right Hand Side in Linear Equation 
which I assume is correct given the problem formulations.  I also get an indication that NaN is 
being generated in the SOlver (GMRES). 

Not surprisingly the Warning goes away when I use the Neumann BC.  THe Solver does not report any 
NaN problems. <<simpleBar.geo>> <<simpleBar.pre>> <<solver.par>> 

Thanks,  the mail archives have been a big help 

Laird Bolt 

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