# interpolation strategy for topological change

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 February 8, 2016, 05:29 interpolation strategy for topological change #1 New Member   Join Date: Oct 2014 Posts: 24 Rep Power: 5 Hi everyone, I studied several cases with rhoPimpleDymFoam about topological changes of mesh (topoChangerFvMesh), and now i'm trying to understand wich strategy is used by default to initialize new cell layers added. In other words, in my case i have a cylinder with a moving boundary (piston), and according with piston movement a new cell layer is added or removed. That's ok. Now I would like to know how the new cells added are initilized in relation with their velocity, pressure, temperature... Thanks for your help. Last edited by DrFloyd; February 9, 2016 at 08:21.

 February 11, 2016, 09:23 interpolation strategy for topological change #2 New Member   Join Date: Oct 2014 Posts: 24 Rep Power: 5 no one has an idea or suggestion?

 February 11, 2016, 14:19 #3 Senior Member   Sandeep Menon Join Date: Mar 2009 Location: Amherst, MA Posts: 396 Rep Power: 17 For layer addition, cells / faces are inflated from zero cell-volume / face-area. As a result, it doesn't matter what value is assigned to the new cell, because at the old-time, the volume was zero (and so, solver quantities are multiplied with zeros at the old-time) and the faces are swept to a non-zero cell-volume at the new-time level. Hope this helps. __________________ Sandeep Menon University of Massachusetts Amherst https://github.com/smenon

February 12, 2016, 06:14
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Thankyou very much for your help Sandeep.

I have a piston going down and a new cell layer is added. I'm using the PISO algorithm and at new timestep I have two new situations:
1) deforming grid;
2) the deformed grid is "cutted" by a plane that generates new cell layer;
I'm using PISO algorithm and I have to initialize all new cells with non-zero volume. How OF initializes these new cell?
I think possibilities are two:
1) It initializes with zero value for T, p, v... and It lets the algorithm to update these values
2) It initializes these values with a linear interpolation from old-cell and at old-time step to the new cell position... and It lets the algorithm to update these values

I attached an image to explain better the situation.

Thanks again!
Attached Images
 jpg.jpeg (41.5 KB, 18 views)

Last edited by DrFloyd; February 22, 2016 at 05:05.

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