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Change of boundary condition value (mole fraction) of species after convergence

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Old   February 6, 2021, 06:21
Default Change of boundary condition value (mole fraction) of species after convergence
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Hi all,

I am simulating a reforming reaction in 2D-axisymmetric case. While putting velocity inlet condition, I am specifying the concentration of inlet species. Say for example. 0.47 for methanol. But as I run the simulation, and get convergence ( less than 10e-05), it seems that the boundary condition of species is changed.

How this is possible as boundary condition should remain same as given by user. I also monitor the mole fraction of methanol while running calculation, it seems to drop sudden at start from 0.47 to 0.29 etc..

However, if I increased the inlet velocity then this change is decreasing. I am not understanding why this is happening?

Also, for pressure outlet condition, I have put 0 value for the species. Is it happening due to reverse flow?

Please help me with this.
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ansys 18.1, fluent 18.1, steam reforming

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