[titio]

Hi Foamers,

In some turbulence models it is used the function twoSymm. I think that when applied to a tensor field
representing the gradient of the velocity, this function gives as a result the deformation rate. In OpenFoam
script

volTensorField DU = fvc :: grad (U);
volSymmTensorField DR = twoSymm (DU) ;

DR will be equal to grad(U) + transpose (grad (U)), right?

If I am wrong, can anyone explain what the function twoSymm does when applied to a tensor field. I looked in the
manuals, either in PDF and online and I did not find nothing.

Regards,

Titio

[henrik]

Dear Titio,

have a look here:

$FOAM_SRC/OpenFOAM/lnInclude/TensorI.H

Henrik

[wiedangel]

//- Return twice the symmetric part of a tensor
template <class Cmpt>
inline SymmTensor<Cmpt> twoSymm(const Tensor<Cmpt>& t)
{
return SymmTensor<Cmpt>
(
2*t.xx(), (t.xy() + t.yx()), (t.xz() + t.zx()),
2*t.yy(), (t.yz() + t.zy()),
2*t.zz()
);
}

[alimea]

Originally Posted by titio

Hi Foamers,

In some turbulence models it is used the function twoSymm. I think that when applied to a tensor field
representing the gradient of the velocity, this function gives as a result the deformation rate. In OpenFoam
script

volTensorField DU = fvc :: grad (U);
volSymmTensorField DR = twoSymm (DU) ;

DR will be equal to grad(U) + transpose (grad (U)), right?

If I am wrong, can anyone explain what the function twoSymm does when applied to a tensor field. I looked in the
manuals, either in PDF and online and I did not find nothing.

Regards,

Titio

I have this question too, is there any difference between

grad(U) + transpose (grad (U))

and

twoSymm (U)

[gu1]

Hello,

If I want to write S², how do I do it?

I need to write sqrt(Sij²)... but it has not worked.

[amuzeshi]

Originally Posted by alimea

I have this question too, is there any difference between

grad(U) + transpose (grad (U))

and

twoSymm (U)

No;

twoSymm(U) = U + transpose (U)
twoSymm(grad (U)) = grad (U) + transpose (grad (U))

[amuzeshi]

Originally Posted by gu1

Hello,

If I want to write S², how do I do it?

I need to write sqrt(Sij²)... but it has not worked.

Hello,

sqr(S)

returns S². from here.