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Knudsen Number

OpenLB – Open Source Lattice Boltzmann Code › Forums › on OpenLB › General Topics › Knudsen Number

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  • September 13, 2021 at 11:34 am #5981
    sahilbhapkar30
    Participant

    Hello,
    I have a doubt regarding the Knudsen Number. In the OpenLB data file, one can see that Knudsen number is calculated by Mach number divided by Reynolds Number.
    However, the formula for Knudsen number based on Reynolds Number and Mach number is :

    Kn=Mach/Re √(γπ/2)
    Where γ is ratio of specific heats.
    So, could you give me the reason why this formula not implemented in OpenLB? I am actually simulating flows based on knudsen number.

    Thank you.

    September 13, 2021 at 11:39 am #5982
    mathias
    Keymaster

    This Ma and Kn are rather numerical than a physical quantities. Furter, the difference is a constant..

    September 13, 2021 at 11:41 am #5983
    sahilbhapkar30
    Participant

    Hello,

    Thank-you for your prompt reply. I did not understand the meaning of the difference is a constant.

    Thank-you

    September 13, 2021 at 11:44 am #5984
    mathias
    Keymaster

    √(γπ/2) is a constant in an incompressible isothermal set up!

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