multicomponent with different densities

[lollipopcorn]

Hi,

in the multicomponent2D example, the initial setup is that the densities of the two fluids are close to 1 with small perturbation. However, when I change the density of one fluid to 0.5, (the other one is around 1), then, during simulation, the fluid with larger density tends to expand dramatically, resulting in the densities of both two fluids being around 0.8.

Why does this happen? shouldn’t the fluids be incompressible in LBM?
How do I modify the codes to achieve different densities of fluids?

Thank you very much,
John

[mathias]

Dear John,

basically you set the pressure! You may leave it to the values 1 and chance the charRho in..

std::vector<T> rho0;
rho0.push_back( 1 ); //first lattice
rho0.push_back( 1 ); //second lattice -> e.g. change it to 2
PsiEqualsRho<T,T> interactionPotential;
ShanChenForcedGenerator3D<T,DESCRIPTOR> coupling( G,rho0,interactionPotential );

Best
Mathias

[lollipopcorn]

Thanks a lot for your reply. your reply solves my problem, except that it seems the first value pushed back is for the second lattce, i.e.

std::vector<T> rho0;
rho0.push_back( 1 ); //this rho is for second lattice
rho0.push_back( 1 ); //first lattice
…

I noticed that I can implement MRT, just wondering does openLB support MRT with multicomponents? if so, do you have any examples that I can study?

Thanks a lot for sharing this excellent library.

John

[mathias]

You can combine it easily but it was not tested yet. For 2D it should work all right. But maybe using a standard LES modell is a better choice since LES was studied a lot in combination with LBM.

Best
Mathias

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