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Old   April 29, 2014, 01:50
Default Real Gas table generation
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Hi all
i have usual problem when i simulate real gas flow, peng-robinson or RK model.
this problem is " temperature and absolute pressure table range".
for some absolute and pressure range solver diverged and return errors like:

Newtons method failed to converge in 100 iterations. This |
| occurred while computing the following variable: |
| |
| Variable Name : Total Temperature |
| Location Name : NOZZLE |
| Mesh location : VERTICES |
| Mesh entity : |
| Last 3 Changes : 1.73755E+01 1.71344E+01 1.70618E+01 |
| Tolerance : 1.0000E-02 |
| |
| The Newton iteration was either slowly converging or has stalled. |
| The solver will continue with the variable set as it was on the |
| final iteration. If this situation continues you might try |
| increasing the number of iterations allowed for Newtons method. |
| This can be changed by setting one of the parameters: |
| |
| Temperature : "Constitutive Relation Iteration Limit" |
| Pressure : "Newton Pressure Iteration Limit" |
| |
| for your mixture using the definition file editor. |

i generate this range by try and error! is there any relation for set this ranges?

Best regards
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Old   April 29, 2014, 03:38
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Glenn Horrocks
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ghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the rough
These sort of errors are common with complex equations of state. You need to improve your simulation's numerical stability. You can do this by:
* Better mesh quality
* Better initial conditions
* double precision numerics
* smaller time steps
* lower order differencing in space and/or time (this one will reduce the accuracy of your simulation)
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