The stabilityBlendingFactor function object computes the stabilityBlendingFactor to be used by the local blended convection scheme. The output is a surface field weight between 0-1.
The weight of a blended scheme, i.e. w, is given by a function of the blending factor, f:
\[ w = f_{scheme_1} + (1 - f_{scheme_2}) \]
The factor is calculated based on six criteria:
The user can enable them individually.
For option 1, the following relation is used, where \(\phi_1\) is the non-orthogonality:
\[ fNon = min ( max ( 0.0, (\phi_1 - max(\phi_1)) /(min(\phi_1) - max(\phi_1)) ), 1.0 ) \]
For option 2, the following relation is used, where \(\phi_2\) is the magnitude of cell centres gradient (Note that \(\phi_2 = 3\) for orthogonal meshes):
\[ fMagGradCc = min ( max ( 0.0, (\phi_2 - max(\phi_2)) / (min(\phi_2) - max(\phi_2)) ), 1.0 ) \]
For option 3, a PID control is used in order to control residual unbounded fluctuations for individual cells.
\[ factor = P*residual + I*residualIntegral + D*residualDifferential \]
where P, I and D are user inputs.
The following relation is used:
\[ fRes = (factor - meanRes)/(maxRes*meanRes); \]
where
meanRes | Average(residual) maxRes | User input
Note that \(f_{Res}\) will blend more towards one as the cell residual is larger then the domain mean residuals.
For option 4, the following relation is used, where \(\phi_4\) is the face weight (Note that \(\phi_4 = 0.5\) for orthogonal meshes):
\[ ffaceWeight = min ( max ( 0.0, (min(\phi_4) - \phi_4) / (min(\phi_4) - max(\phi_4)) ), 1.0 ) \]
For option 5, the following relation is used, where \(\phi_5\) is the cell skewness:
\[ fskewness = min ( max ( 0.0, (\phi_5 - max(\phi_5)) / (min(\phi_5) - max(\phi_5)) ), 1.0 ) \]
For option 6, the following relation is used:
\[ fCoWeight = min(max((Co - Co1)/(Co2 - Co1), 0), 1) \]
where
Co1 | Courant number below which scheme2 is used Co2 | Courant number above which scheme1 is used
The final factor is determined by:
\[ f = max(fNon, fMagGradCc, fRes, ffaceWeight, fskewness, fCoWeight) \]
An indicator (volume) field, named blendedIndicator is generated if the log flag is on:
1 represent scheme1 as active, 0 represent scheme2 as active.
Additional reporting is written to the standard output, providing statistics as to the number of cells used by each scheme.
| Operand | Type | Location |
|---|---|---|
| input | - | - |
| output file | dat | $FOAM_CASE/postProcessing/<FO>/<time>/<file> |
| output field | volScalarField | $FOAM_CASE/<time>/<outField> |
Example of the stabilityBlendingFactor function object by using functions sub-dictionary in system/controlDict file:
stabilityBlendingFactor1
{
// Mandatory entries (unmodifiable)
type stabilityBlendingFactor;
libs (fieldFunctionObjects);
// Mandatory entries (unmodifiable)
field <field>; // U;
result <outField>; // UBlendingFactor;
// Optional entries (runtime modifiable)
tolerance 0.001;
// Any of the options can be chosen in combinations
// Option-1
switchNonOrtho true;
nonOrthogonality nonOrthoAngle;
maxNonOrthogonality 20;
minNonOrthogonality 60;
// Option-2
switchGradCc true;
maxGradCc 3;
minGradCc 4;
// Option-3
switchResiduals true;
maxResidual 10;
residual initialResidual:p;
P 1.5;
I 0;
D 0.5;
// Option-4
switchFaceWeight true;
maxFaceWeight 0.3;
minFaceWeight 0.2;
// Option-5
switchSkewness true;
maxSkewness 2;
minSkewness 3;
// Option-6
switchCo true;
U U;
Co1 1;
Co2 10;
// Optional (inherited) entries
writePrecision 8;
writeToFile true;
useUserTime true;
region region0;
enabled true;
log true;
timeStart 0;
timeEnd 1000;
executeControl timeStep;
executeInterval 1;
writeControl timeStep;
writeInterval 1;
}
where the entries mean:
| Property | Description | Type | Required | Default |
|---|---|---|---|---|
| type | Type name: stabilityBlendingFactor | word | yes | - |
| libs | Library name: fieldFunctionObjects | word | yes | - |
| field | Name of the operand field | word | yes | - |
| result | Name of surface field to be used in the localBlended scheme | word | yes | - |
| switchNonOrtho | Select non-orthogonal method | bool | no | false |
| nonOrthogonality | Name of the non-orthogonal field | word | no | nonOrthoAngle |
| maxNonOrthogonality | Maximum non-orthogonal for scheme2 | scalar | no | 20 |
| minNonOrthogonality | Minimum non-orthogonal for scheme1 | scalar | no | 60 |
| switchGradCc | Select cell centre gradient method | bool | no | false |
| maxGradCc | Maximum gradient for scheme2 | scalar | no | 2 |
| minGradCc | Minimum gradient for scheme1 | scalar | no | 4 |
| switchResiduals | Select residual evolution method | bool | no | false |
| residual | Name of the residual field | word | no | initialResidual:p |
| maxResidual | Maximum residual-mean ratio for scheme1 | scalar | no | 10 |
| P | Proportional factor for PID | scalar | no | 3 |
| I | Integral factor for PID | scalar | no | 0 |
| D | Differential factor for PID | scalar | no | 0.25 |
| switchFaceWeight | Select face weight method | bool | no | false |
| faceWeight | Name of the faceWeight field | word | no | faceWeight |
| maxFaceWeight | Maximum face weight for scheme1 | scalar | no | 0.2 |
| minFaceWeight | Minimum face weight for scheme2 | scalar | no | 0.3 |
| switchSkewness | Select skewness method | bool | no | false |
| skewness | Name of the skewness field | word | no | skewness |
| maxSkewness | Maximum skewness for scheme2 | scalar | no | 2 |
| minSkewness | Minimum skewness for scheme1 | scalar | no | 3 |
| switchCo | Select Co blended method | bool | no | false |
| U | Name of the flux field for Co blended | word | no | U |
| Co1 | Courant number below which scheme2 is used | scalar | no | 1 |
| Co2 | Courant number above which scheme1 is used | scalar | no | 10 |
| tolerance | Tolerance for number of blended cells | scalar | no | 0.001 |
The result entry is the field which is read by the localBlended scheme specified in fvSchemes. This name is determined by the localBlended class.
The inherited entries are elaborated in:
Usage by the postProcess utility is not available.
Tutorial:
Source code:
History
1.8.17