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Getting velocity distributions.

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  • #8102
    avrachan1
    Participant

    Dear OpenLB community,

    If we consider a D2Q9 system, at each lattice point, there are 9 distributions – for the 9 velocities.
    We define the initial condition using
    sLattice.defineRhoU( bulkIndicator, rhoF, uF);

    If let’s say rhoF=1. and uF=(1,0), how are these values distributed among the 9 distributions?

    How can I access and modify these ?

    For example can I set uF = (0.,0.) but none of the 9 velocities are zero – How can I do this ?

    Thanks!

    • This topic was modified 3 months, 3 weeks ago by avrachan1. Reason: formatting
    #8104
    avrachan1
    Participant

    got it!

    You can edit the populations at each cell using,

    sLattice.definePopulations(…);

    #8105
    Adrian
    Keymaster

    Indeed, glad you were able to find this method on your own.

    As for the other part of your question: The way that a given macroscopic quantity such as density or velocity is mapped into the mesoscopic population values depends on the specific local model of the specific cell. Generally speaking this is done by computing the equilibrium distribution that represents these specific macroscopic moments.

    Further details of these basic LBM concepts are available in our user guide or for example in the LBM book by Krueger et al.

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