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-   -   2 stage axial turbine model convergence issues (https://www.cfd-online.com/Forums/cfx/68109-2-stage-axial-turbine-model-convergence-issues.html)

sherifkadry September 7, 2009 11:40

2 stage axial turbine model convergence issues
 
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

ckleanth September 7, 2009 13:15

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

ghorrocks September 7, 2009 20:51

Here's the link George referred to: http://www.cfd-online.com/Wiki/Ansys...gence_criteria


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