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Time step independence in Transient simulation with RPI Wall boiling

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Old   October 25, 2023, 07:35
Default Time step independence in Transient simulation with RPI Wall boiling
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marcus aurelius
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I am trying to simulate subcooled flow boiling in horizontal channel with Non-equilibrium RPI wall boiling model. It is transient simulation with Implicit scheme. Steady state simulation are not giving the true results so that scenario is already discarded. I have already performed grid independency and now trying to do time step converging/independence for transient simulation. Started with time step of 5E-02 and reduced upto 1E-05. But, the results keep changing every time. The results have shown to match when time step is around 5E-03. With smaller time step, The results keep changing significantly.

y+ is around 30. I am using ANSYS Fluent

So, please help me how time step independence can be achieved?

The models and schemes are listed in picture attached.
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Old   January 21, 2024, 10:39
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Pierre LECHEVALIER
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Dear MarcusAurelius,
Do you have some figures to introduce ? Is it changing a lot when decreasing your time step ?


Best regards,
Pierre
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Old   January 22, 2024, 06:22
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I have found out the reason for that. Selecting interfacial area model "ia-symmetric" instead of "ia-particle" solved the problem of Time step convergence.

But, the results are now way different than expected. The wall temperature is increasing by 2-3 times than actual.
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ansys, eulerian eulerian, fluent, multiphase, rpi wall boiling

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