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-   -   Difference between exact value and calculated value (http://www.cfd-online.com/Forums/openfoam-post-processing/91662-difference-between-exact-value-calculated-value.html)

OFU August 18, 2011 08:31

Difference between exact value and calculated value
 
Hi,

I want to calculate Teps of the the following equation:

T0 (1 + Teps) = T

T0 is the exact solution and T the solution calculated by OpenFOAM in each time step.

For the internalField it works. And also if an boundary patch is defined as type inletOutlet with an uniform inletValue and an uniform value it works too. But if an patch is defined as type zeroGradient or type fixedValue with an uniform value, the calculation of Teps seems not to work. Then the mentioned patches of the boundary field of Teps look the same as the boundary fields in T.
Does anybody know how I can get the right values of these patches?
I want to calculate the same for p, rho and U.
Or are there already applications in OpenFOAM, which calculate the difference between an exact value and the values calculated by OpenFOAM?

Thanks in advance,
Jennifer

eugene August 19, 2011 05:19

The trick is to create your result field independent of the input fields so that it uses a "calculated" type boundary everywhere. Then the assignment should work fine.

Something like:

volScalarField Teps
(
IOobject
(
blah blah blah
),
mesh,
dimensionedScalar("Teps", T.dimensions(), 0.0)
);

Teps = some functions of T and T0

hjasak August 19, 2011 06:10

Did you call

T.correctBoundaryConditions();

after updating the internal field?

Hrv


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