Velocity potential is pretty well defined here:


When I try to run with no boundary conditions I'm getting the error below. Does it lead to a singular matrix or something with no essential boundary conditions?


Traceback (most recent call last):
  File "", line 113, in <module>
  File "", line 104, in main
    conf = ProblemConf.from_file_and_options(filename_in, options, required, other)
  File "/Users/steve/Development/sfepy/sfepy/base/", line 311, in from_file_and_options
  File "/Users/steve/Development/sfepy/sfepy/base/", line 290, in from_file
    required, other, verbose, override)
  File "/Users/steve/Development/sfepy/sfepy/base/", line 359, in __init__
    required=required, other=other)
  File "/Users/steve/Development/sfepy/sfepy/base/", line 369, in setup
    other_missing = self.validate( required = required, other = other )
  File "/Users/steve/Development/sfepy/sfepy/base/", line 421, in validate
    raise ValueError('required missing: %s' % required_missing)
ValueError: required missing: ['ebc_[0-9]+|ebcs']

On Wednesday, June 6, 2012 3:10:58 PM UTC-6, Robert Cimrman wrote:
On 06/06/2012 09:40 PM, steve wrote:
> OK.. on to the eigenvalue problem.
> I started with the quantum program... and stripped out all the quantum
> stuff. ;-)
> Basically the acoustics problem is exactly the square well potential (V=0
> everywhere) BUT with different boundary conditions.
> In we've got:
>      ebc_1 = {
>          'name' : 'ZeroSurface',
>          'region' : 'Surface',
>          'dofs' : {'Psi.0' : 0.0},
>      }
> Which forces psi to be zero on the surface of Omega. Basically Dirichlet
> conditions. For acoustics the velocity potential needs to have no normal
> gradient at the surfaces.. more or less Neumann conditions. Is there an
> easy way to implement that?

What is the exact definition of the velocity potential? If it's really a
Neumann-like boundary integral, having it zero = omitting the term in
equations + no Dirichlet boundary conditions (ebcs) at all.