Hi Benny, The oscillations may be a result of pressure velocity decoupling. To avoid this on a collocated grid one needs to use an interpolation method such as Rhie-Chow interpolation or a more modern variant:
<http://apps.isiknowledge.com/full_record.do?product=WOS&search_mode=GeneralSearch&qid=6&sid=1c...@1f69fl81hkpdm&page=1&doc=1#output_options> In FiPy this generally required getting the matrix diagonal and using it as part of the interpolation. I can discuss more if you want to pursue it further. I am not sure if it is possible to set up a staggered grid in FiPy in a practical way. That may be another option. One grid would probably have to be created in Gmsh in order to have the cell centers at the same place as the face centers on the other grid. I have never tried this, but it is certainly possible. Hope this helps. Cheers. On Tue, Jul 6, 2010 at 5:48 AM, Benny Malengier <[email protected]> wrote: > Hi, > > I am doing a flow field calculation like > http://www.ctcms.nist.gov/fipy/examples/flow/generated/examples.flow.stokesCavity.html > > However, I obtain spurious oscillations for the pressure solution. Patankar > in his works is very clear that a staggered grid should be used for the > SIMPLE algorithm, in the example averaging is applied so as to work on one > grid, which I believe leads to these oscillations. > > Does anybody has an idea how best to alleviate this problem? I am thinking > about eg a CornerCellVariable for vx/vy, which would be the staggered grid. > In essense that means a mesh holds two grids then. It becomes complicated > fast however. > Perhaps other ideas? Or better to calculate the flow field with another > tool? > > Greetings, > Benny > -- Daniel Wheeler
