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dynamic of pressure

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    I have modify a little bit cylinder2d.
    I put a velocity inlet 3ms^-1 and a pressure outlet 0
    I have used air_dynamic_viscosity 1.9e-5 try to have Re#400-100
    (trying with deltaP inlet100Pa outlet0Pa with no succes seem not works…)

    I compare with a real system wich is an air flow on a little valve moving :

    I have a dynamic pressure in front of th valve simulated wich is instantanly moving but in reallity this is smoth change
    time_constant = 0,0386054 so rising time is around 0.15s (due to lag time…) not an instannaly response.
    Maybe I do an error.
    What could be the problem in this kind of simulation?.


    Try to change the parameter smoothly starting with a stable set-up and determine the source of the instability.



    Hi Mathias,
    I have doing like this.
    It is not an instability!

    My simulation didn’t realise the time changement of state : when we open the valve we obtain a step changement of pressure. This is not realistic value. When opening the valve pressure seem change immediatly…
    We measure it on a real system : the time changement is about 0.15s this is not immediatly change.

    I use BGK to calculate but maybe I do use MRT to avoid this phenomen ?


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