[giammy92]

Hi guys, i have a flux on an airfoil 2D and in file nut:

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

internalField uniform 0;

boundaryField
{
FAR_FIELD
{
type freestream;
freestreamValue uniform 0;
}

TRAILING_EDGE
{
type nutkWallFunction;
value uniform 0;
}

SUCTION_SIDE
{
type nutkWallFunction;
value uniform 0;
}

PRESSURE_SIDE
{
type nutkWallFunction;
value uniform 0;
}

frontAndBackPlanes
{
type empty;
}
}

According you, is correct put in internal field 0, and in FAR_FIELD a type freestream with uniform 0? Or i should set a type calculated?

[rupole1185]

I tend to use calculated rather than freestream generally ... Is zero the freestream value you really want?

[giammy92]

in reality my value of nut is 1.51e-6 but comparing with another case it is set often to 0 in internal field and in inlet. So i have found the formula of turbulent viscosity that depends from du/dy and so i think that in undisturbed flux because du/dy=0, nut is 0 too, and then in internal field and in FAR_FIELD for my case.

[rupole1185]

Yep in theory you are right .. But it depends o. The inlet: is it a pipe, duct or something like this? If so, u is not constant in wall normal direction and this returns some inlet turbulence ...

[giammy92]

no, i have a freestream to the inlet, so i have to set 0 both in internal field and in far field but with type calculated?

[rupole1185]

Yep .. If you have a k-epsilon turbulence model you'll get a zero turbulent viscosity when k is zero ...

[giammy92]

i have k-omega SST

[giammy92]

but k isn't 0 in internal field and in far field...

[rupole1185]

Well .. It works the same way .. As I said, if k is not zero in the far field thus nut can't be zero (nut is proportional to k)...

[giammy92]

ok, but if i set type calculated for far field, to entry value i have to set uniform 0 or 1.51e-6 ?

[rupole1185]

Well it doesn't matter as it is just a dumb command

[giammy92]

ok thank you

[rupole1185]

You are welcome