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Old   December 19, 2009, 19:34
Default residuals
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Dear all,

I'm doing the simulation of the flow around a stage of a Low Pressure Turbine and I want a suggestion.
I'm working with Ansys CFX, but I think my problem is not related to the software. I think I need to act on some numerical parameters.
I set residual limits for all of the equations as 1.e-06 and I'm using the k-eps.
The problem is that for momentum and mass residuals the values achieved are less than 1e-06, while for turbulence residuals the values achieved are not less than 1.e-06. Then the simulation continue as long as the maximum number of the iteration that I set at the begin of my simulation is achieved.

For this reason I have two questions:
- do you think the limit value of the residual: 1.e-06 is reasonable? is it too low?
- do you know which parameters do I have to change in order to achieve the converge for turbulence equations.

Kind regards

Domenico di Cugno
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Old   December 20, 2009, 03:51
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The residual level for turbulence transport equations (for k-eps, as well as the Reynolds stress components and the turbulent heat flux components) does not form part of the convergence criteria.
For detail on residual level see: Judging Convergence in ANSYS CFX-Solver Modeling Guide.
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