DA question

[Randall Mackie]

Amit,

I have a staggered grid with H defined along the edges and E as normals
across the block faces. So if you have l x m x n blocks, then you need
to define your DA as l+1, m+1, n+1, to handle the extra grid point you
need for the staggered grid. I use 3 degrees of freedom (for Hx, Hy, and
Hz), and all my local calculations just need the box stencil.

Randy


Sean Dettrick wrote:
> To elaborate on Matt's suggestion, a staggered grid/Yee mesh code
> could use a single DA with one degree-of-freedom per component of H
> and E.  The extra overlap required for staggered guard cells at the
> domain boundaries could be dealt with by having a bigger-than-usual
> stencil width.  For the 2nd order 3D case, this suggests the
> DACreate3d routine would have arguments dof=6, s=2, and
> stencil_type=DA_STENCIL_STAR.
> 
> It is just a suggestion - I have not tried it.
> 
> Sean
> 
> On Wed, Apr 9, 2008 at 5:06 PM,  <Amit.Itagi at seagate.com> wrote:
>> Randy,
>>
>>  I guess, since you are doing a frequency domain calculation, you eventually
>>  end up with a single matrix equation.
>>
>>  I am planning to work in the time domain. Will that change things ?
>>
>>  Thanks
>>
>>  Rgds,
>>  Amit
>>
>>
>>
>>
>>              Randall Mackie
>>              <rlmackie862 at gmai
>>              l.com>                                                     To
>>
>>              Sent by:                  petsc-users at mcs.anl.gov
>>              owner-petsc-users                                          cc
>>              @mcs.anl.gov
>>              No Phone Info                                         Subject
>>              Available                 Re: DA question
>>
>>
>>              04/09/2008 04:09
>>
>>
>>              PM
>>
>>
>>              Please respond to
>>              petsc-users at mcs.a
>>                   nl.gov
>>
>>
>>
>>
>>
>>
>>  Hi Amit,
>>
>>  Why do you need two staggered grids? I do EM finite difference frequency
>>  domain modeling on a staggered grid using just one DA. Works perfectly
>>  fine.
>>  There are some grid points that are not used, but you just set them to zero
>>  and put a 1 on the diagonal of the coefficient matrix.
>>
>>
>>  Randy
>>
>>
>>  Amit.Itagi at seagate.com wrote:
>>  > Hi Berend,
>>  >
>>  > A detailed explanation of the finite difference scheme is given here :
>>  >
>>  > http://en.wikipedia.org/wiki/Finite-difference_time-domain_method
>>  >
>>  >
>>  > Thanks
>>  >
>>  > Rgds,
>>  > Amit
>>  >
>>  >
>>  >
>>  >
>>
>>  >              Berend van Wachem
>>
>>  >              <berend at chalmers.
>>
>>  >              se>
>>  To
>>  >              Sent by:                  petsc-users at mcs.anl.gov
>>
>>  >              owner-petsc-users
>>  cc
>>  >              @mcs.anl.gov
>>
>>  >              No Phone Info
>>  Subject
>>  >              Available                 Re: DA question
>>
>>  >
>>
>>  >
>>
>>  >              04/09/2008 02:59
>>
>>  >              PM
>>
>>  >
>>
>>  >
>>
>>  >              Please respond to
>>
>>  >              petsc-users at mcs.a
>>
>>  >                   nl.gov
>>
>>  >
>>
>>  >
>>
>>  >
>>  >
>>  >
>>  >
>>  > Dear Amit,
>>  >
>>  > Could you explain how the two grids are attached?
>>  > I am using multiple DA's for multiple structured grids glued together.
>>  > I've done the gluing with setting up various IS objects. From the
>>  > multiple DA's, one global variable vector is formed. Is that what you
>>  > are looking for?
>>  >
>>  > Best regards,
>>  >
>>  > Berend.
>>  >
>>  >
>>  > Amit.Itagi at seagate.com wrote:
>>  >> Hi,
>>  >>
>>  >> Is it possible to use DA to perform finite differences on two staggered
>>  >> regular grids (as in the electromagnetic finite difference time domain
>>  >> method) ? Surrounding nodes from one grid are used to update the value
>>  in
>>  >> the dual grid. In addition, local manipulations need to be done on the
>>  >> nodal values.
>>  >>
>>  >> Thanks
>>  >>
>>  >> Rgds,
>>  >> Amit
>>  >>
>>  >
>>  >
>>  >
>>
>>
>>
>>
>