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2 stage axial turbine model convergence issues

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Old   September 7, 2009, 11:40
Default 2 stage axial turbine model convergence issues
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Sherif Kadry
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Hello,
I was hoping any CFX turbo gurus could give me some guidance on achieving a converged model of a axial turbine. The model uses a straight stator and bowed rotor blades. I have actual experimental data to use for my boundary conditions. The rotor stage mesh was obtained from a colleague and had performed fairly well in a previous model (previous models had bowed stator and rotor blades). I needed to create a straight stator blade mesh which I did using ICEMCFD.
Model specifics:
-2-stage model (stator and rotor geometry are the same for each stage)
-steady state model
-stage interface was used the pitch to pitch ratio is 1.0 equal blade numbers for stator and rotor.
-total pressure inlet bc specified (based on experimental data).
-exit static pressure bc specified (based on experimental data).
-SST model was used as recommended by ANSYS

The main problem is the model does not converge, I have investigated the stator mesh and it seems to be okay (refining or coarsening of the mesh seems to still produce a diverging model) that could also be a problem point not really sure as I am mainly an experimentalist. Could this be an issue with the stage interface definition and aligning the stator exit and rotor inlet? Any tips or advice would be much appreciated

Sherif
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Old   September 7, 2009, 13:15
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George
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not a turbo expert but check the faq for convergence problems

my guess (if you checked everything else is fine) is that your problem is not steady state
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Old   September 7, 2009, 20:51
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Here's the link George referred to: http://www.cfd-online.com/Wiki/Ansys...gence_criteria
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