Hi, Sorry to hijack the discussion but I'm currently thinking of implementing DMDA for staggered grids in 2D and later on in 3D.
I am not sure if my problem is exactly the same as that of Tim but I don't really understand his problem. So for my case, I have a staggered grid for my finite volume CFD code. So the grid looks like this: Do I need to create 3 DMDA, for u,v,p? When computing the flux, I will also need to interpolate u and v velocities on the u or v cells. I hope you can suggest the best way to approach this problem. Btw, in the discussion, there's also some mention of DOF. However, I thought each variable (u,v,p) will have only 1 DOF, is that not so? Thanks! Yours sincerely, TAY wee-beng On 2/12/2011 8:12 PM, Barry Smith wrote: > Tim, > > Unfortunately the DMDA was not designed with the idea of staggered grids > (or mixed discretizations) in mind so they are not straightforward like we > would like them to be. > > Do I understand you want two DMDA > > 1) one that has locations for cell vertices (or face centers)? > > 2) and one that locations for cell centers? > > Once we understand what you want we may be able to make a suggestion. > > Barry > > > On Dec 2, 2011, at 1:08 PM, Tim Gallagher wrote: > >> Hi, >> >> I'm trying to create some grids for a finite volume simulation and am a >> little stuck on the best way to tackle it. The approach now is to use >> DMDACreate3d with known number of I, J, K points and PETSC_DECIDE for the >> processors. Then I am trying to create another DMDA with the same >> distribution to store the cell centers and actual solution vector. The >> problem with is is the following: >> >> Consider 9 points and two processors. Processor one gets points [1,5] with >> point 6 as a ghost and processor two gets points [6,9] with point 5 as a >> ghost. But now to create/store cell centers, processor two needs point 4 to >> construct a cell center for it's ghost. >> >> I can certainly fetch that point and do the calculation, but I feel like >> there is a more elegant way to do this out there. Has anybody used a DMDA to >> create a dual DMDA? >> >> Any advice would be appreciated, >> >> Tim -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20111207/12041fc2/attachment-0001.htm> -------------- next part -------------- A non-text attachment was scrubbed... Name: ecdhigbj.png Type: image/png Size: 47018 bytes Desc: not available URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20111207/12041fc2/attachment-0001.png>
