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Implementation of filters in OpenFOAM

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Old   March 21, 2022, 01:34
Default Implementation of filters in OpenFOAM
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Siddhi
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Hello all.

I am currently working on OpenFOAM and have few questions regarding how filters are used in it:

(1)In dynamicKEqn.C, why simplefilter is again used after using filter while calculating LL,MM etc. This has not been specified in any literature.

const volSymmTensorField LL
(
simpleFilter_(dev(filter_(sqr(this->U_)) - (sqr(filter_(this->U_)))))
);

const volSymmTensorField MM
(
simpleFilter_(-2.0*this->delta()*sqrt(KK)*filter_(D))
);

const volScalarField Ck
(
simpleFilter_(0.5*(LL && MM))
/(
simpleFilter_(magSqr(MM))
+ dimensionedScalar("small", sqr(MM.dimensions()), VSMALL)
)
);

(2)In above code, if simpleFilter is used in LL and MM, why again it is used in numerator and denominator term while calculating Ck.

(3)Is LESfilter as same as user defined filter? Can it be simpleFilter, LaplaceFilter etc?

(4) If I want to filter velocity field, will the term given below will be sufficient?
filter_(this->U_)

Thank you so much if anyone can provide some guidance
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Old   October 27, 2022, 03:29
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exw599
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Quote:
Originally Posted by Siddhi View Post
Hello all.

I am currently working on OpenFOAM and have few questions regarding how filters are used in it:

(1)In dynamicKEqn.C, why simplefilter is again used after using filter while calculating LL,MM etc. This has not been specified in any literature.

const volSymmTensorField LL
(
simpleFilter_(dev(filter_(sqr(this->U_)) - (sqr(filter_(this->U_)))))
);

const volSymmTensorField MM
(
simpleFilter_(-2.0*this->delta()*sqrt(KK)*filter_(D))
);

const volScalarField Ck
(
simpleFilter_(0.5*(LL && MM))
/(
simpleFilter_(magSqr(MM))
+ dimensionedScalar("small", sqr(MM.dimensions()), VSMALL)
)
);

(2)In above code, if simpleFilter is used in LL and MM, why again it is used in numerator and denominator term while calculating Ck.

(3)Is LESfilter as same as user defined filter? Can it be simpleFilter, LaplaceFilter etc?

(4) If I want to filter velocity field, will the term given below will be sufficient?
filter_(this->U_)

Thank you so much if anyone can provide some guidance
The simpleFilter is used for smoothing the nominator and denominator. It is neither test filter nor grid filter implemented.
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