[Getdp] 2d DC Conduction

Laird Bolt lbolt1 at irf.com
Tue Feb 28 22:12:58 CET 2006


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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