Homogenous and isotropic turbulence in RANS modeling

CFD_10 · May 27, 2019, 13:48

hello
I have a question about turbulence models in the Reynolds Averaging Navier Stokes method implemented in most CFD softwares.

Let's limit the scope only to k-epsilon and k-omega models,

Do they suppose a homogeneous and isotropic turbulence?
if so then as far as I know: A flow is said to be homogenous if there are no spatial gradients in any averaged gradients. and a turbulent flow is said to be isotropic if rotation and buoyancy are not important and there is no mean flow.

Any details please?

FMDenaro · May 27, 2019, 14:07

Quote:

Originally Posted by CFD_10

hello
I have a question about turbulence models in the Reynolds Averaging Navier Stokes method implemented in most CFD softwares.

Let's limit the scope only to k-epsilon and k-omega models,

Do they suppose a homogeneous and isotropic turbulence?
if so then as far as I know: A flow is said to be homogenous if there are no spatial gradients in any averaged gradients. and a turbulent flow is said to be isotropic if rotation and buoyancy are not important and there is no mean flow.

Could you please answer my question?

No, RANS formulations suppose only fully developed turbulence

sbaffini · May 27, 2019, 16:38

Only some (not all) coefficients are typically calibrated against HIT.

May 27, 2019, 13:48	Homogenous and isotropic turbulence in RANS modeling	#1
CFD_10 Member CFD USER Join Date: May 2019 Posts: 40 Rep Power: 6	hello I have a question about turbulence models in the Reynolds Averaging Navier Stokes method implemented in most CFD softwares. Let's limit the scope only to k-epsilon and k-omega models, Do they suppose a homogeneous and isotropic turbulence? if so then as far as I know: A flow is said to be homogenous if there are no spatial gradients in any averaged gradients. and a turbulent flow is said to be isotropic if rotation and buoyancy are not important and there is no mean flow. Any details please? Last edited by CFD_10; May 28, 2019 at 12:48.

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May 27, 2019, 16:38		#3
sbaffini Senior Member Paolo Lampitella Join Date: Mar 2009 Location: Italy Posts: 2,151 Blog Entries: 29 Rep Power: 39	Only some (not all) coefficients are typically calibrated against HIT.