# Strange mesh dependent result of a pipe flow with SSG

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November 8, 2017, 05:24
Strange mesh dependent result of a pipe flow with SSG
#1
New Member

Andi
Join Date: Feb 2014
Location: Berlin
Posts: 6
Rep Power: 12
Hello everybody,

I have simulated a simple turbulent pipe flow with the SSG turbulence model. The residuals converge. Some probs are constant.
I only use linear or limitedLinear schemes in the Divergence scheme. With the Surface-normal gradient I use the Corrected schemes. However, the result shows a strong dependence on the mesh or the orientation of the mesh.
A refinement delivers the same result.
I used wall functions at yPlus = 30.
Is there any hint, what I can try.

Best regards
And I
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 November 9, 2017, 04:14 #2 New Member   Andi Join Date: Feb 2014 Location: Berlin Posts: 6 Rep Power: 12 Hello has anyone some experience with the SSG Reynolds Stress Model? Best Regards Andi

 November 9, 2017, 16:03 #3 New Member   JPeternel Join Date: Oct 2014 Posts: 19 Rep Power: 11 Generally, every solution is mesh dependent ... maybe introducing nonOrthogonal correctors or bigger number of PISO correctors can give you better results. Also, results usually converge when increasing mesh density. Also, using smooth transitions from one type of meshing to another improve results, those triangles may be causing the trouble ...

 November 10, 2017, 00:14 #4 Senior Member     Uwe Pilz Join Date: Feb 2017 Location: Leipzig, Germany Posts: 744 Rep Power: 15 The construction of the mesh may be better: 1) The transition form the radial elements to the rectangular is far to close to the edge. 2) I would look for a construction idea where the transition is nut such abrupt 3) I would use only square/hexagonal elements an avoid abnormal triangular ones __________________ Uwe Pilz -- Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950)

 Tags pipe flow, ssg, turbulence models