[EnricoDeFilippi]

Hi guys, I'm studying an axial turbine, so to solve my stator and rotor fields I'm using mixing plane. The problem is that using steadyCompressibleMRFFoam with foam extend 3.2 all works fine while with 4.0 it takes to unphysical solution.

I can't use the 3.2 because I've to work with real gas whose library is not implemented in foam 3.2. I've already checked the source file in the finiteVolume and foam/meshes folder about mixingPlane trying to make the 4.0 more similar as possibile to the 3.2.
Did anybody of you already face this problem? Do you have any suggestion?
I leave the different results I get with 3.2 and 4.0 version:


Flux divergence min = 0.000232183584313 max = 1824125.33839 average: 1101.45637728
Mach number min = 0.00190838717129 max = 2.00273908446
Field U magnitude min = 0 max = 856.643527779
Field p min = 42331.9029619 max = 510310.051604
Field rho min = 0.306032525316 max = 7.79979800637
Field T min = 200 max = 500
Mixing plane pair (Outflow_stator, Inflow_rotor) : 0.345041766478 -0.345509719296 Diff = -0.000467952818715 or 0.135622079464 %



Flux divergence min = 4.55157280307e-05 max = 249609.441799 average: 114.297658371
Mach number min = 2.98841685868e-05 max = 2.5808451657
Field U magnitude min = 0 max = 500
Field p min = 5444.94477356 max = 1000000
Field rho min = 0.00619202851425 max = 17.379256264
Field T min = 3.19875761314 max = 7469.41474673
Mixing plane pair (Outflow_stator, Inflow_rotor) : 0.00214541998123 0.000282009095223 Diff = 0.00242742907645 or 113.144703493 %



Thanks in advance.

[HenrikJohansson]

Hi Enrico

I have been struggeling with the same problem in 4.0. I think there is something missing in the rothalpy calculations.
In 3.2 rothalpy is calculated by:

    fvScalarMatrix iEqn
    (
        fvm::ddt(rho, i)
      + fvm::div(phi, i)
      - fvm::laplacian(turbulence->alphaEff(), i)
        // u & gradP term (steady-state formulation)
      + fvm::SuSp((fvc::div(faceU, p, "div(U,p)") - fvc::div(faceU)*p)/i, i)
     ==
        // Viscous heating: note sign (devRhoReff has a minus in it)
      - (turbulence->devRhoReff() && fvc::grad(Urel))
    );

And in 4.0 it is:

    fvScalarMatrix iEqn
    (
        fvm::ddt(rho, i)
      + fvm::div(phi, i)
      - fvm::laplacian(turbulence->alphaEff(), i)
     ==
        // Viscous heating: note sign (devRhoReff has a minus in it)
      - (turbulence->devRhoReff() && fvc::grad(Urel))
    );

Thus I think the u and gradP terms are missing in 4.0.
My rothalpy is way off to. I'm running real gas in a turbine. I have tried with different meshes and y+ without any results.
I'm currently running a simluation where the rhotalpy is disabled and the enthalpy is enabled instead.
It doesen't solve the enthalpy but it will hopefully prove my point about the rothalpy.

[EnricoDeFilippi]

Hey Henrik, thank you very much for the input. Me and my professor supposed there was something that was calculated wrong at the mixing plane, do maybe is the rothalpy. I will work on it and let you know if I have managed to solve something as soon as possible.

[EnricoDeFilippi]

At the moment I've checked all the files written n the directory application/solver/compressible/steadyCompressibleMRFFoam. There are some difference but changing the files as it was in 3.2 didn't help to solve my problem.