Can you please describe more about your problem? What o you mean by complex?

Imaginary values

Dear Debashis Panda,

what multiphase model are using?

Regards

Knut Küllmer

Dear Knut Küllmer,

I am using multiphase lattice Boltzmann model.

Dear Debashis Panda,

there are various lattice Boltzmann models for multiphase flows, which ground on different assumptions and behave completely different. E.g. the color gradient model, the free-energy model, the pseudopotenial model, different phase field-based models, (and more, all of them lattice Boltzmann models). Thus, to be able to help, you have to be a little more specific.

Regards

Knut Küllmer

Dear Knut Küllmer,

I am using the pseudopotential model with C-S EOS.

Thank you.

Dear Debashis,

thank you for informing about the model you are using. Could it be possible to have some more details about the case you are trying to simulate and the simulation setup?

Best Regards,

Ernesto

Dear Debashis Panda,

okay, to use the CS-EOS in the pseudopotential model, you have to use a modified potential function in which the paramter G appears in the denominator in a square root expression. In this case, G can be picked arbitrarily, only its sign is used to ensure that the radicand of this expression is positive. So this could be a reason for complex numbers. Have you tried switching the sign of G?

Some more information about this procedure and some problems that are connected to it can be found in the publication

Khajepor, Sorush; Wen, John; Chen, Baixin: Multipseudopotential interaction: A solution for thermodynamic inconsistency in pseudopotential lattice Boltzmann models. PRE 91, 023301 (2015).

Regards

Knut Küllmer

Dear Debashis,

together with the paper previously suggested let me address you to another interesting, though older work. I personally implemented this model in my code.

Determination of the pseudopotential gradient in multiphase lattice

Boltzmann models

Attila Markus and Gábor Házi

PHYSICS OF FLUIDS 20, 022101
2008

Best Regards,

Ernesto

Dear Ernesto,

Thank you so much for your input

I will definitely go through and try to implement in my code.