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Compression instead of expansion

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Old   October 7, 2018, 09:14
Default Compression instead of expansion
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Enrico De Filippi
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Hi everybody, I'm simulating an axial turbine with mixing plane and real gas. As you know, a turbine expand the gas, but in my simulation there are zones in which the gas is higly compressed ( so non-physical results). Do you have any hint on how to solve this or how to control? Maybe, i've put wrong boundary condition. Here are the 0/ files:
alphat
dimensions [1 -1 -1 0 0 0 0];

internalField uniform 0;

boundaryField
{
Inflow_stator
{
type calculated;
value uniform 0;
}
Outflow_stator
{
// type mixingPlaneFvPatchField:
type mixingPlane;
value $internalField;
}

Wall_stator
{
type alphatWallFunction;
Prt 0.741;
value uniform 0;
}
Perio_stator
{
type cyclic;
value uniform 0;
}

Inflow_rotor
{
// type mixingPlaneFvPatchField:
type mixingPlane;
value $internalField;
}

Outflow_rotor
{
type calculated;
value uniform 0;
}
Wall_rotor
{
type alphatWallFunction;
Prt 0.741;
value uniform 0;
}
Perio_rotor1
{
type cyclic;
value uniform 0;
}

Perio_rotor2
{
type cyclic;
value uniform 0;
}

}
epsilon
dimensions [0 2 -3 0 0 0 0];

internalField uniform 10000;

boundaryField
{
Inflow_stator
{
type fixedValue;
value uniform 2000;

}

Outflow_stator
{
type mixingPlane;
value $internalField;
}

Wall_stator
{
type compressible::epsilonWallFunction;
refValue uniform 0;
value $internalField;
Cmu 0.09;
kappa 0.41;
E 9.8;
}

Perio_stator
{
type cyclic;
value $internalField;
}

Inflow_rotor
{
type mixingPlane;
value $internalField;
}

Outflow_rotor
{
type inletOutlet;
inletValue $internalField;
value 13450;

}

Wall_rotor
{
type compressible::epsilonWallFunction;
refValue uniform 0;
value $internalField;
Cmu 0.09;
kappa 0.41;
E 9.8;
}

Perio_rotor1
{
type cyclic;
value $internalField;
}

Perio_rotor2
{
type cyclic;
value $internalField;
}

}
i
dimensions [0 2 -2 0 0 0 0];

internalField uniform 27000;

boundaryField
{
Inflow_stator
{
type fixedValue;
value $internalField;
}
Outflow_stator
{
// type mixingPlaneEnthalpyJump;
// patchType mixingPlane;
type mixingPlane;
rotating false;
value $internalField;
}
Perio_stator
{
type cyclic;
value $internalField;
}
Wall_stator
{
type gradientEnthalpy;
gradient uniform 0;
value uniform 463864;
}

Inflow_rotor
{
// type mixingPlaneEnthalpyJump;
// patchType mixingPlane;
type mixingPlane;
rotating true;
value $internalField;
}

Wall_rotor
{
type gradientEnthalpy;
gradient uniform 0;
value $internalField;
}
Outflow_rotor
{
type inletOutlet;
inletValue $internalField;
value $internalField;
}
Perio_rotor1
{
type cyclic;
value $internalField;
}

Perio_rotor2
{
type cyclic;
value $internalField;
}
}
k
dimensions [0 2 -2 0 0 0 0];

internalField uniform 5;

boundaryField
{
Inflow_stator
{
type fixedValue;
value 0.4;
}

Outflow_stator
{
type mixingPlane;
value $internalField;
}


Wall_stator
{
type compressible::kqRWallFunction;
value $internalField;

}

Perio_stator
{
type cyclic;
value $internalField;
}

Inflow_rotor
{
type mixingPlane;
value $internalField;
}

Outflow_rotor
{
type inletOutlet;
inletValue $internalField;
value $internalField;

}

Wall_rotor
{
type compressible::kqRWallFunction;
value $internalField;

}

Perio_rotor1
{
type cyclic;
value $internalField;
}

Perio_rotor2
{
type cyclic;
value $internalField;
}

}
p
dimensions [1 -1 -2 0 0 0 0];

internalField uniform 400000;

boundaryField
{

Inflow_stator
{
type totalPressure;
phi phi;
rho none;
psi psi;
U U;
gamma 1.4;
p0 uniform 5.1e5;
value $internalField;
}

Outflow_stator
{
type mixingPlane;
rotating false;
value $internalField;
}


Wall_stator
{
type zeroGradient;
}

Perio_stator
{
type cyclic;
value $internalField;
}

Inflow_rotor
{
type mixingPlane;
rotating true;
value $internalField;
}


Outflow_rotor
{
type fixedValue;
value uniform 300000;
}

Wall_rotor
{
type zeroGradient;
}

Perio_rotor1
{
type cyclic;
value $internalField;
}

Perio_rotor2
{
type cyclic;
value $internalField;
}
}
T
dimensions [0 0 0 1 0 0 0];

internalField uniform 330;

boundaryField
{

Inflow_stator
{
type totalTemperature;
phi phi;
rho rho;
psi psi;
U U;
gamma 1.4;
T0 uniform 338;
value $internalField;

}

Outflow_stator
{
// type mixingPlaneEnthalpyJump;
// patchType mixingPlane;
type mixingPlane;
rotating false;
value $internalField;
}

Wall_stator
{
type zeroGradient;
}

Perio_stator
{
type cyclic;
value $internalField;
}

Inflow_rotor
{
// type mixingPlaneEnthalpyJump;
// patchType mixingPlane;
type mixingPlane;
rotating true;
value $internalField;
}

Outflow_rotor
{
type zeroGradient;
value $internalField;
}

Wall_rotor
{
type zeroGradient;
}

Perio_rotor1
{
type cyclic;
value $internalField;
}

Perio_rotor2
{
type cyclic;
value $internalField;
}

}
U
dimensions [0 1 -1 0 0 0 0];

internalField uniform (0 0 100);

boundaryField
{
Inflow_stator
{
type pressureDirectedInletVelocity;
inletDirection uniform (0 0 1);
value uniform (0 0 0);
}

Outflow_stator
{
type mixingPlane;
rotating false;
value $internalField;
}
Wall_stator
{
type fixedValue;
value uniform (0 0 0);
}

Perio_stator
{
type cyclic;
value $internalField;
}


Inflow_rotor
{
type mixingPlane;
rotating true;
value $internalField;
}

Outflow_rotor
{
type pressureInletOutletVelocity;
inletValue $internalField;
value $internalField;

}

Wall_rotor
{
type fixedValue;
value uniform (0 0 0);
}

Perio_rotor1
{
type cyclic;
value $internalField;
}

Perio_rotor2
{
type cyclic;
value $internalField;
}

}


These are the results after 5000 iterations:


Flux divergence min = 4.28614548132e-05 max = 24180860.2673 average: 15406.0985031
Writing divFlux field
Mach number min = 0.00198878622956 max = 4.35597144753
Writing Mach number field
Field U magnitude min = 0 max = 1000
Field p min = 49202.4992467 max = 1055827.15616
Field rho min = 1.52104950445 max = 27.9890057068
Field T min = 337.498873263 max = 1163.72657359
Mixing plane pair (Outflow_stator, Inflow_rotor) : 0.756677749244 -0.757134457367 Diff = -0.00045670812309 or 0.0603570177062 %
End



max U should be around 160 m/s and max T and p should be around the ones at the inlet.
Any hint would be appreciated.
Thanks in advance.
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Old   October 8, 2018, 10:19
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