[Friendly]

Hello everyone,


I am struggling with a weird phenomenon:
I am doing a simulationen of an underexpanded jet with rhoCentralFoam. At the inlet I have a totalPressure, totalTemperature und zeroGradient for U and the outlet wavetransmissive for p and U and zeroGradient for T. Walls are slip (U) or zeroGradient (p,T).
I have noticed, that that the totalPressure at the inlet rises. I have set the totalPressure to 10e5 Pa but he rises up to 23e5 Pa.


Here are the boundary conditions for the Inlet:

p:

 
         type            totalPressure;

        phi               phi;
        rho              none;
        psi               thermo:psi;
        gamma           1.4;
        p0               uniform 10e5;
         value           uniform 10e5;

T:
        type            totalTemperature;
        gamma         1.4;
        phi              phi;
        rho             none;
        psi              thermo:psi;
        T0              uniform 293.15;
        value           uniform 293.15;


U:

        type            zeroGradient;

For the outlet:

p:


        type            waveTransmissive;
        field           p;
        psi             thermo:psi;
        gamma           1.4;
        fieldInf        101325;
        lInf            1;
        value           uniform 101325;


T:


        type            zeroGradient;


U:


        type            waveTransmissive;
        field             U;
        phi              phi;
        rho              rho;
        psi               thermo:psi;
        gamma           1.4;
        fieldInf        (0 0 0);
        lInf            1;
        value           uniform (0 0 0);

I think somehow my boundary conditions are wrong. But I have seen many people using them like that. Does anyone have an idea what I coudl do better?


Thank you!


Friendly

[tas38]

Are you sure that the total pressure on the inlet boundary patch itself rises, or the total pressure rises "close" to the inlet. I wonder if the inlet boundary patch may not be specified correctly and there is a sudden increase in total pressure just inside the computational domain.

[Friendly]

Hi,


yes, I am looking only at the inlet. I also think that my boundary conditions are wrong, so I searched for other works and those boundary conditions seem ok.


I also wonder why the total pressure should rise. I think it is only possible if a closed vessel is filled with gas. But those boundary conditions shouldnt work like a wall.

[akwiatek]

Hi,

Did you manage to solve the case?