Reply To: Multiphase Separation: Setting Density and Viscosity ratios

[stephan]

Dear joeruan,

thanks for posting.

(1) You can modify the density ratio in the phaseSeparation examples by definition of the initial density profile. The Shan-Chen models currently implemented in OpenLB can be found in src/dynamics/interactionPotential.*. The one used in examples/multiComponent/phaseSeparation2d/ for example is taken from https://doi.org/10.1103/PhysRevE.49.2941 and is based on a single distribution realization. The default values for rho and psi are 200 and 4, respectively (see .h file).

(2) Yes, the modification of viscosity most probably has to be addressed with a second lattice.
For two components, see examples/multiComponent/rayleighTaylor2d/.
However, (to the best of my knowledge) due to numerical reasons, non-marginal viscosity ratios would require a modification of the present code. I can recommend https://www.wiley.com/en-us/Multiphase+Lattice+Boltzmann+Methods%3A+Theory+and+Application-p-9781118971338, or https://link.springer.com/book/10.1007/978-3-319-44649-3 for further reading.

(3) From a purely technical point of view you could make the interaction parameter non constant an pass it to the coupling. Maybe a few other modifications are required.

BR
Stephan