cp_ref in phase change modelling

[Mike]

Hello everyone,

I have conducted a test on the example “stefanmelting2d” in olb-1.4 and discovered that the value of “cp_ref” has a significant impact on the simulation results. However, the paper titled “Phase interface effects in the total enthalpy-based lattice Boltzmann model for solid-liquid phase change,” which is referenced in “stefanmelting2d.cpp,” states that the choice of “cp_ref” can be arbitrary. I attempted to change the value of “cp_ref” both in “stefanmelting2d.cpp” and in the constructor function of the “TotalEnthalpyAdvectionDiffusionBGKdynamics” class. While both simulations converged, the results differed from each other.

Can anyone assist me in resolving this issue? Thank you for your help in advance.

Best regards,
Mike

[mathias]

I guess it is a parameter to conrol stability on the cost of accuracy.

[Mike]

Hello Mathias,

Thanks for your reply! From the perspective of results, “cp_ref” seems to have a serious impact on the simulation accuracy. And the paper mentioned above also mentioned that value of “cp_ref” affects the numerical stability. But when I look into the introduction process of “cp_ref”, it seems that “cp_ref” can be eliminated finally, which may not affect the accuracy of results.

I am uncertain if I have misunderstood this, and I look forward to your response!

Best regards,
Mike

[mathias]

You could also look in the previous paper, I mean the ones before ours.. We also did compare our results to a non-LBM approach. So we have some evidence..

[Mike]

Hello Mathias,

Thank you for your reply again! I understand that stafanmelting2d is a benchmark case that can be compared with non-LBM approaches to demonstrate the capabilities of the current LBM method, and the results match very well.

However, when I developed another self-coded program concerning phase change and used the harmonic mean value for “cp_ref,” the simulation diverged. On the other hand, when I used “cp_s” for “cp_ref,” the simulation converged. Interestingly, the simulation diverged regardless of whether “cp_ref” was larger or smaller than “cp_s.”

Therefore, if “cp_ref” affects the accuracy, I may need to conduct a verification experiment. This is why I want to figure this out.

Best regards,
Mike

[Author]

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