[tmik]

Hi all,


I just ran into something very strange to me. I'm solving a compressible flow using rhoSimpleFoam, and am confused as to how the yPlus function works.


It looks like the yPlus function gave me a calculation for each results set I have. Furthermore, looking at the values, they are different between iterations. There's no reason for y+ to be changing, right? I'm using a mesh I made in Salome, not moving or anything.



y+ is a geometric parameter, based on my mesh - so why does it change with each iteration?

...

Time = 1900
Reading thermophysical properties

Selecting thermodynamics package
{
    type            hePsiThermo;
    mixture         pureMixture;
    transport       const;
    thermo          hConst;
    equationOfState perfectGas;
    specie          specie;
    energy          sensibleInternalEnergy;
}

Reading field U

Reading/calculating face flux field phi

pressureControl
    pMax 1.28091e+06
    pMin 64045.4

Creating turbulence model

Selecting turbulence model type RAS
Selecting RAS turbulence model kOmegaSST
RAS
{
    RASModel        kOmegaSST;
    turbulence      on;
    printCoeffs     on;
    alphaK1         0.85;
    alphaK2         1;
    alphaOmega1     0.5;
    alphaOmega2     0.856;
    gamma1          0.555556;
    gamma2          0.44;
    beta1           0.075;
    beta2           0.0828;
    betaStar        0.09;
    a1              0.31;
    b1              1;
    c1              10;
    F3              false;
    decayControl    false;
    kInf            0;
    omegaInf        0;
}

No MRF models present

yPlus yPlus write:
    writing field yPlus
    patch walls y+ : min = 14.6179, max = 1200.02, average = 452.317

Time = 2000
Reading thermophysical properties

Selecting thermodynamics package
{
    type            hePsiThermo;
    mixture         pureMixture;
    transport       const;
    thermo          hConst;
    equationOfState perfectGas;
    specie          specie;
    energy          sensibleInternalEnergy;
}

Reading field U

Reading/calculating face flux field phi

pressureControl
    pMax 1.28091e+06
    pMin 64045.4

Creating turbulence model

Selecting turbulence model type RAS
Selecting RAS turbulence model kOmegaSST
RAS
{
    RASModel        kOmegaSST;
    turbulence      on;
    printCoeffs     on;
    alphaK1         0.85;
    alphaK2         1;
    alphaOmega1     0.5;
    alphaOmega2     0.856;
    gamma1          0.555556;
    gamma2          0.44;
    beta1           0.075;
    beta2           0.0828;
    betaStar        0.09;
    a1              0.31;
    b1              1;
    c1              10;
    F3              false;
    decayControl    false;
    kInf            0;
    omegaInf        0;
}

No MRF models present

yPlus yPlus write:
    writing field yPlus
    patch walls y+ : min = 4.23512, max = 906.382, average = 453.212

End

[simrego]

Hi!


Yes, it is calculated for every timestep since yPlus is NOT a fully geometric parameter. Check this:
https://www.cfd-online.com/Wiki/Dime...tance_(y_plus)
yPlus is also depending on the friction velocity.
If you are running a steady state calculation, you can call the utility with the switch "-latestTime", so it will calculate the yPlus value only in the last timestep.