# foam-extend 4.1 GGI check

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 February 23, 2021, 14:46 foam-extend 4.1 GGI check #1 New Member   Andrea Join Date: Dec 2017 Posts: 9 Rep Power: 8 Hello Folks I'm working with foam-extend simulating a Francis turbine and I have problems to get a solution. In the CAD the surfaces composing the interfaces perfectly match each other. After meshed (discretization error) the differences between areas at the interfaces are: Spiral-GuideVanes: Diff = -1.54116647556601e-05 Bulb-DraftTube: Diff = 2.25976241261805e-05 According to your experience, is it enough an area difference of O(e-05) for GGI (or mixing plane) interfaces? Bests

 February 24, 2021, 05:20 #2 Senior Member   Hrvoje Jasak Join Date: Mar 2009 Location: London, England Posts: 1,905 Rep Power: 33 This should not be a problem - compare the error in area between the two surfaces with respect to the flux error. Can you post the whole message? __________________ Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk

 February 24, 2021, 05:35 #3 New Member   Andrea Join Date: Dec 2017 Posts: 9 Rep Power: 8 Thank you for reply Prof. Jasak. The message is the following: GGI pair (SP-GV, GV-SP) Area: 0.254671269026831 0.254686680691586 Diff = -1.54116647556601e-05 or 0.00605122525991961 % Flux: 0.949992608907554 0.950088338717345 Diff = -9.57298097908899e-05 or 0.010075885145599 % GGI pair (BULB-DT, DT-BULB) Area: 0.138815526804067 0.138792929179941 Diff = 2.25976241261805e-05 or 0.0162788879936147 % Flux: 0.972494692318502 0.972510217271029 Diff = -1.55249525264356e-05 or 0.0015963793748101 % Regarding the last interface (mixing-plane) the mixing plane check is not working in parallel (this can be verified also running the tutorial "axialTurbine_mixingPlane"). I made the grids using Numeca AG5 and Omnis. The checkMesh looks fine. Create time Create polyMesh for time = 0 Initializing the GGI interpolator between master/shadow patches: SP-GV/GV-SP Initializing the GGI interpolator between master/shadow patches: BULB-DT/DT-BULB Time = 0 Mesh stats all points: 22230489 live points: 13966149 all faces: 46481093 live faces: 38339883 internal faces: 35820020 cells: 12196229 boundary patches: 27 point zones: 0 face zones: 6 cell zones: 4 Overall number of cells of each type: hexahedra: 11986443 prisms: 0 wedges: 0 pyramids: 0 tet wedges: 0 tetrahedra: 0 polyhedra: 209786 Checking topology... Boundary definition OK. Point usage OK. Upper triangular ordering OK. Face vertices OK. *Number of regions: 4 The mesh has multiple regions which are not connected by any face. <

 August 22, 2022, 11:01 #4 New Member   Jianfeng Join Date: Apr 2021 Posts: 11 Rep Power: 5 Hi, did you use the ggi interface in parallel mode ? I find the initialization takes too much time when I use ggi interface in parallel? Do I need to decompose the mesh in another way ? Thanks!

 Tags foam-extend 4.1, ggi, interfaces, mixing-plane

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