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Re: DA question

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@xxxxxxxxxxx> 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
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 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@xxxxxxxxxxx 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@chalmers.

 >              se>
 To
 >              Sent by:                  petsc-users@xxxxxxxxxxx

 >              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@xxxxx

 >                   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@xxxxxxxxxxx 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
 >>
 >
 >
 >